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Sample records for corneal collagen cross-linking

  1. Corneal collagen cross-linking

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    Jankov II Mirko

    2010-01-01

    Full Text Available Corneal collagen cross-linking (CXL with riboflavin and ultraviolet-A (UVA is a new technique of corneal tissue strengthening by using riboflavin as a photosensitizer and UVA to increase the formation of intra- and interfibrillar covalent bonds by photosensitized oxidation. Keratocyte apoptosis in the anterior segment of the corneal stroma all the way down to a depth of about 300 microns has been described and a demarcation line between the treated and untreated cornea has been clearly shown. It is important to ensure that the cytotoxic threshold for the endothelium has not been exceeded by strictly respecting the minimal corneal thickness. Confocal microscopy studies show that repopulation of keratocytes is already visible 1 month after the treatment, reaching its pre-operative quantity and quality in terms of functional morphology within 6 months after the treatment. The major indication for the use of CXL is to inhibit the progression of corneal ectasias, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photoablation. This treatment has also been used to treat infectious corneal ulcers with apparent favorable results. Combination with other treatments, such as intracorneal ring segment implantation, limited topography-guided photoablation and conductive keratoplasty have been used with different levels of success.

  2. [Corneal collagen cross-linking for keratoconus].

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    Zotov, V V; Pashtaev, N P; Pozdeeva, N A

    2015-01-01

    Over the last decade, corneal collagen cross-linking (CXL) has become a conventional treatment method for progressive keratoconus. Laboratory studies have shown that CXL increases the diameter of collagen fibers and also the number of intra- and interfibrillar cross-links, thus, increasing biomechanical strength of the irradiated cornea. As confirmed by a series of clinical and randomized controlled trials, CXL is able to slow down and, perhaps, to stop the progression of keratoconus. In most post-CXL patients visual acuity improves, while keratometric readings, spherical equivalent, and higher order aberrations reduce. Although published results prove CXL effective in the treatment of progressive keratoconus, its late consequences are yet unknown. This article reviews the stages of CXL development and results of published experimental and clinical studies. Prospects for CXL modifications that do not require epithelial debridement are discussed.

  3. ROLE OF CORNEAL COLLAGEN CROSS LINKING IN KERATOCONUS

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    Atul; Superna; Bhimasankar; Vijayleela

    2015-01-01

    To evaluate the outcome of collagen cross linkage using riboflavin 0.1% and ultraviolet A radiation of a wavelength 370nm . PURPOSE : To determine the effect of collagen cross linking for keratoconus on pachymetry , corneal topography, uncorrected visual acuity, specular count, IOP at 1, 3, 6 months . METHODS : The current study was designed as a prospective interventional trial of corneal collagen cross - linking in subjects w...

  4. Transient Anisocoria after Corneal Collagen Cross-Linking

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    Kymionis, George D.; Grentzelos, Michael A.; Stojanovic, Nela; Paraskevopoulos, Theodore A.; Detorakis, Efstathios T.

    2014-01-01

    Purpose. To report a case with transient anisocoria after corneal collagen cross-linking (CXL). Methods. Case report. Results. A 24-year-old male underwent corneal collagen cross-linking (CXL) in his right eye for keratoconus. At the end of the procedure, the pupil of the treated eye was irregular and dilated, while the pupil of the fellow eye was round, regular, and reactive (anisocoria). The following day, pupils were round, regular, and reactive in both eyes. Conclusion. Anisocoria may be a transient and innocuous complication after CXL. A possible cause for this complication might be the anesthetic drops used before and during the surgical procedure or/and the ultraviolet A irradiation during the treatment. PMID:25276451

  5. Transient Anisocoria after Corneal Collagen Cross-Linking

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    George D. Kymionis

    2014-01-01

    Full Text Available Purpose. To report a case with transient anisocoria after corneal collagen cross-linking (CXL. Methods. Case report. Results. A 24-year-old male underwent corneal collagen cross-linking (CXL in his right eye for keratoconus. At the end of the procedure, the pupil of the treated eye was irregular and dilated, while the pupil of the fellow eye was round, regular, and reactive (anisocoria. The following day, pupils were round, regular, and reactive in both eyes. Conclusion. Anisocoria may be a transient and innocuous complication after CXL. A possible cause for this complication might be the anesthetic drops used before and during the surgical procedure or/and the ultraviolet A irradiation during the treatment.

  6. Progress of research on corneal collagen cross-linking for corneal melting

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    Ke-Ren Xiao

    2016-06-01

    Full Text Available Corneal collagen cross-linking(CXLcould increase the mechanical strength, biological stability and halt ectasia progression due to covalent bond formed by photochemical reaction between ultraviolet-A and emulsion of riboflavin between collagen fibers in corneal stroma. Corneal melting is an autoimmune related noninfectious corneal ulcer. The mechanism of corneal melting, major treatment, the basic fundamental of ultraviolet-A riboflavin induced CXL and the clinical researches status and experiment in CXL were summarized in the study.

  7. ROLE OF CORNEAL COLLAGEN CROSS LINKING IN KERATOCONUS

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    Atul

    2015-09-01

    Full Text Available To evaluate the outcome of collagen cross linkage using riboflavin 0.1% and ultraviolet A radiation of a wavelength 370nm . PURPOSE : To determine the effect of collagen cross linking for keratoconus on pachymetry , corneal topography, uncorrected visual acuity, specular count, IOP at 1, 3, 6 months . METHODS : The current study was designed as a prospective interventional trial of corneal collagen cross - linking in subjects with progressive keratoconus between a period of J anuary 2013 to J uly 2014 including 50 eyes of 30 patients. This study rece ived approval from Ethics committee. Informed written consent was obtained from all patients prior to treatment. RESULTS: Mean follow up period of 6 months. There was statistically significant decline in effective k readings from mean pre op (51.7D to pos t op value (49.65D . Pachymetry showed initial increase post operatively followed by reduction in corneal thickness in 3 month s follow up , followed by gradual increase in thickness over a period of 6 months though it was not equivalent to pre - operative values. paired t test p value was 0.00 1 in 1 n 3 month and 0. 043 in 6 month, concluding significant reduction in early post op period with im provement over time . Specular count reduced from pre - op (2673.80 levels to post - op (2654.60 levels ,the reduction in specular count was not statistically significant P value (0.014 The uncorrected visual acuity showed decrease in refractive error with in crease in visual acuity gradually over 6 months, log MAR scale visual acuity was used for statistical analysis with P value (0.001 which was statistically significant .visual acuity improved by 1.5 lines in snellens equivalence or from 0.5 to 0.4 in log MA R char y ± 20cells/mm 3 , P value(0. 001 . IOP statically show ed no significant change in pre - operative and post operatively , paired t test p value was 0. 44 showing it was not significant . CONCLUSIONS : 1. Visual acuity improved in

  8. Corneal collagen cross-linking to stop corneal ectasia exacerbated by radial keratotomy.

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    Mazzotta, Cosimo; Baiocchi, Stefano; Denaro, Rosario; Tosi, Gian Marco; Caporossi, Tomaso

    2011-02-01

    To assess the efficacy of riboflavin ultraviolet A (UV-A) corneal collagen cross-linking in the management of keratoconic corneal ectasia exacerbated by radial keratotomy (RK). A patient with progressive corneal ectasia and hyperopic shift, occurring 10 years after RK performed in the left eye, was treated with riboflavin UV-A corneal collagen cross-linking according to the Siena protocol: Pilocarpin 0.1% drop (1 hour before), lidocaine 4% drops 15 minutes before, mechanical scraping of epithelium (9-mm-diameter area), preirradiation stromal soaking for 10 minutes in riboflavin 0.1%-dextrane 20% (Ricrolin; Sooft Italy) applied every 2 minutes, and 30 minutes of total exposure (6 steps of 5 minutes) to solid-state UV-A illuminator (Caporossi, Baiocchi, Mazzotta Vega X linker; CSO Opthalmics, Florence, Italy), energy delivered 3 mW/cm, and irradiated area 9 mm in diameter. After the operation, uncorrected visual acuity and best spectacle-corrected visual acuity improved from 0.2 to 0.6 and from 0.3 to 0.8 Snellen lines, respectively, in a 12-month follow-up. Improved topographical K readings and corneal symmetry index were also recorded starting from the first postoperative month and continuing thereafter. No adverse effects were recorded after treatment. Riboflavin UV-A-induced corneal cross-linking seems to be a promising surgical option in the management of unstable corneal ectasia exacerbated by RK, particularly in eyes with preexisting keratoconus. A large cohort and longer follow-up are needed to determine its long-term efficacy in this clinical setting.

  9. Scheimpflug imaged corneal changes on anterior and posterior surfaces after collagen cross-linking

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    Ziad Hassan

    2014-04-01

    Full Text Available AIM: To compare the anterior and posterior corneal parameters before and after collagen cross-linking therapy for keratoconus.METHODS: Collagen cross-linking was performed in 31 eyes of 31 keratoconus patients (mean age 30.6±8.9y. Prior to treatment and an average 7mo after therapy, Scheimpflug analysis was performed using Pentacam HR. In addition to corneal thickness assessments, corneal radius, elevation, and aberrometric measurements were performed both on anterior and posterior corneal surfaces. Data obtained before and after surgery were statistically analyzed.RESULTS: In terms of horizontal and vertical corneal radius, and central corneal thickness no deviations were observed an average 7mo after operation. Corneal higher order aberration showed no difference neither on anterior nor on posterior corneal surfaces. During follow-up period, no significant deviation was detected regarding elevation values obtained by measurement in mm units between the 3.0-8.0 mm-zones.CONCLUSION: Corneal stabilization could be observed in terms of anterior and posterior corneal surfaces, elevation and higher order aberration values 7mo after collagen cross-linking therapy for keratoconus.

  10. Induction of corneal collagen cross-linking in experimental corneal alkali burns in rabbits

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    Marcello Colombo-Barboza

    2014-10-01

    Full Text Available Objective: To evaluate the effect of riboflavin-ultraviolet-A-induced cross-linking (CXL following corneal alkali burns in rabbits. Methods: The right corneas and limbi of ten rabbits were burned using a 1N solution of NaOH and the animals were then divided into two groups: a control group submitted to clinical treatment alone and an experimental group that was treated 1 h after injury with CXL, followed by the same clinical treatment as administered to the controls. Clinical parameters were evaluated post-injury at 1, 7, 15, and 30 days by two independent observers. Following this evaluation, the corneas were excised and examined histologically. Results: There were no statistically significant differences in clinical parameters, such as hyperemia, corneal edema, ciliary injection, limbal ischemia, secretion, corneal neovascularization, symblepharon, or blepharospasm, at any of the time-points evaluated. However, the size of the epithelial defect was significantly smaller in the CXL group (p<0.05 (day 15: p=0.008 and day 30: p=0.008 and the extent of the corneal injury (opacity lesion was also smaller (day 30: p=0.021. Histopathology showed the presence of collagen bridges linking the collagen fibers in only the CXL group. Conclusions: These results suggest that the use of CXL may improve the prognosis of acute corneal alkali burns.

  11. Epoxy Cross-Linked Collagen and Collagen-Laminin Peptide Hydrogels as Corneal Substitutes

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    May Griffith

    2013-08-01

    Full Text Available A bi-functional epoxy-based cross-linker, 1,4-Butanediol diglycidyl ether (BDDGE, was investigated in the fabrication of collagen based corneal substitutes. Two synthetic strategies were explored in the preparation of the cross-linked collagen scaffolds. The lysine residues of Type 1 porcine collagen were directly cross-linked using l,4-Butanediol diglycidyl ether (BDDGE under basic conditions at pH 11. Alternatively, under conventional methodology, using both BDDGE and 1-Ethyl-3-(3-dimethyl aminopropyl carbodiimide (EDC/N-hydroxysuccinimide (NHS as cross-linkers, hydrogels were fabricated under acidic conditions. In this latter strategy, Cu(BF42·XH2O was used to catalyze the formation of secondary amine bonds. To date, we have demonstrated that both methods of chemical cross-linking improved the elasticity and tensile strength of the collagen implants. Differential scanning calorimetry and biocompatibility studies indicate comparable, and in some cases, enhanced properties compared to that of the EDC/NHS controls. In vitro studies showed that human corneal epithelial cells and neuronal progenitor cell lines proliferated on these hydrogels. In addition, improvement of cell proliferation on the surfaces of the materials was observed when neurite promoting laminin epitope, IKVAV, and adhesion peptide, YIGSR, were incorporated. However, the elasticity decreased with peptide incorporation and will require further optimization. Nevertheless, we have shown that epoxy cross-linkers should be further explored in the fabrication of collagen-based hydrogels, as alternatives to or in conjunction with carbodiimide cross-linkers.

  12. Acute Corneal Hydrops 3 Years after Intra-corneal Ring Segments and Corneal Collagen Cross-linking

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    Antonios, Rafic; Dirani, Ali; Fadlallah, Ali; Chelala, Elias; Hamadeh, Adib; Jarade, Elias

    2016-01-01

    This case report describes a 15-year-old male with allergic conjunctivitis and keratoconus, who underwent uneventful intra-corneal ring segment (ICRS) implantation and corneal collagen cross-linking (CXL) in the right eye. During the follow-up periods, the patient was noted to have several episodes of allergic conjunctivitis that were treated accordingly. At the 2 years postoperatively, he presented with another episode of allergic conjunctivitis and progression of keratoconus was suspected on topography. However, the patient was lost to follow-up, until he presented with acute hydrops at 3 years postoperatively. There are no reported cases of acute corneal hydrops in cross-linked corneas. We suspect the young age, allergic conjunctivitis and eye rubbing may be a risk factors associated with possible progression of keratoconus after CXL. Prolonged follow-up and aggressive control of the allergy might be necessary in similar cases. PMID:26957859

  13. Corneal collagen cross-linking and liposomal amphotericin B combination therapy for fungal keratitis in rabbits

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    Hao, Zhao-Qin; Song, Jin-Xin; Pan, Shi-Yin; Zhang, Lin; Cheng, Yan; Liu, Xian-Ning; Wu, Jie; Xiao, Xiang-Hua; Gao, Wei; Zhu, Hai-Feng

    2016-01-01

    AIM To observe the therapeutic effect of corneal collagen cross-linking (CXL) in combination with liposomal amphotericin B in fungal corneal ulcers. METHODS New Zealand rabbits were induced fungal corneal ulcers by scratching and randomly divided into 3 groups, i.e. control, treated with CXL, and combined therapy of CXL with 0.25% liposomal amphotericin B (n=5 each). The corneal lesions were documented with slit-lamp and confocal microscopy on 3, 7, 14, 21 and 28d after treatment. The corneas were examined with transmission electron microscopy (TEM) at 4wk. RESULTS A rabbit corneal ulcer model of Fusarium was successfully established. The corneal epithelium defect areas in the two treatment groups were smaller than that in the control group on 3, 7, 14 and 21d (Pulcers. The combined therapy could alleviate corneal inflammattions, accelerate corneal repair, and shorten the course of disease. PMID:27990355

  14. Corneal changes following collagen cross linking and simultaneous topography guided photoablation with collagen cross linking for keratoconus

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    Prema Padmanabhan

    2014-01-01

    Full Text Available Purpose: To compare the outcome of Collagen cross-linking (CXL with that following topography-guided customized ablation treatment (T-CAT with simultaneous CXL in eyes with progressive keratoconus. Materials and Methods: This was a prospective, non-randomized single centre study of 66 eyes with progressive keratoconus. Of these, 40 eyes underwent CXL and 26 eyes underwent T-CAT + CXL. The refractive, topographic, tomographic and aberrometric changes measured at baseline, 1, 3 and 6 months post-operatively were compared between both groups. Results: After a mean follow-up of 7.7 ± 1.3 months, the mean retinoscopic cylinder decreased by 1.02 ± 3.16 D in the CXL group ( P = 0.1 and 2.87 ± 3.22 D in the T-CAT + CXL group ( P = 0.04. The Best corrected visual acuity increased by 2 lines or more in 10% of eyes in the CXL group and in 23.3% of eyes in the T-CAT + CXL group. The mean steepest-K reduced by 0.40 ± 3.71 D ( P = 0.77 in the CXL group and by 2.91 ± 2.01D ( P = 0.03 in the T-CAT + CXL group. The sag factor and surface asymmetry index showed no significant change in the CXL group but reduced by 3.59 ± 5.94 D ( P = 0.01 and 0.72 ± 1.18 ( P = 0.02 respectively in the T-CAT + CXL group. There was a significant increase in the highest posterior corneal elevation in both groups (9.57 ± 14.93 μ in the CXL group and 7.85 ± 9.25 μ in the T-CAT + CXL group, P ≤ 0.001 for both. There was significantly greater reduction of mean coma ( P < 0.001 and mean higher-order aberrations ( P = 0.01 following T-CAT + CXL compared to CXL. Conclusions: CAT + CXL is an effective approach to confer biomechanical stability and to improve the corneal contour in eyes with keratoconus and results in better refractive, topographic and aberrometric outcomes than CXL alone.

  15. Corneal collagen cross-linking and liposomal amphotericin B combination therapy for fungal keratitis in rabbits

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    Zhao-Qin Hao

    2016-11-01

    Full Text Available AIM: To observe the therapeutic effect of corneal collagen cross-linking (CXL in combination with liposomal amphotericin B in fungal corneal ulcers. METHODS: New Zealand rabbits were induced fungal corneal ulcers by scratching and randomly divided into 3 groups, i.e. control, treated with CXL, and combined therapy of CXL with 0.25% liposomal amphotericin B (n=5 each. The corneal lesions were documented with slit-lamp and confocal microscopy on 3, 7, 14, 21 and 28d after treatment. The corneas were examined with transmission electron microscopy (TEM at 4wk. RESULTS: A rabbit corneal ulcer model of Fusarium was successfully established. The corneal epithelium defect areas in the two treatment groups were smaller than that in the control group on 3, 7, 14 and 21d (P<0.05. The corneal epithelium defect areas of the combined group was smaller than that of the CXL group (P<0.05 on 7 and 14d, but there were no statistical differences on 3, 21 and 28d. The corneal epithelium defects of the two treatment groups have been healed by day 21. The corneal epithelium defects of the control group were healed on 28d. The diameters of the corneal collagen fiber bundles (42.960±7.383 nm in the CXL group and 37.040±4.160 nm in the combined group were thicker than that of the control group (24.900±1.868 nm, but there was no difference between the two treatment groups. Some corneal collagen fiber bundles were distorted and with irregular arrangement, a large number of fibroblasts could be seen among them but no inflammatory cells in both treatment groups. CONCLUSION: CXL combined with liposomal amphotericin B have beneficial effects on fungal corneal ulcers. The combined therapy could alleviate corneal inflammattions, accelerate corneal repair, and shorten the course of disease.

  16. Progress of corneal collagen cross-linking combined with refractive surgery

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    Na Li

    2014-02-01

    Full Text Available As a photochemical reaction that can stiffen the cornea, corneal collagen cross-linking (CXL is the only promising method of preventing the progress of keratectasia, such as keratoconus and secondary ectasia following refractive surgery. The aim of CXL is to stabilize the underlying condition, with a small chance of visual improvement. Combining CXL with refractive surgery targeting both stabilization and reshaping of the corneal tissue for visual function improvement is a good treatment option. This review aims to provide a comprehensive and unbiased summary of the published research regarding combined CXL and refractive surgery, including measures and results, to help elucidate the future direction of CXL.

  17. An Update on the Safety and Efficacy of Corneal Collagen Cross-Linking in Pediatric Keratoconus

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    El Rami, Hala; Chelala, Elias; Fakhoury, Henry; Cherfan, Carole; Cherfan, George; Jarade, Elias

    2015-01-01

    Keratoconus is a degenerative disease that affects adolescents and young adults and presents with variable thinning and conical deformation of the corneal apex. The resultant irregular astigmatism can progress to levels that can significantly affect everyday activities and overall quality of life. Therefore, stopping the progression of the disease is an essential part in managing patients with keratoconus. Corneal collagen cross-linking is a minimally invasive procedure that stiffens the anterior corneal stroma by creating strong covalent bonds between collagen fibrils. Over the past decade, many studies have proved its safety and efficacy in halting keratoconus progression in adults. This review of the literature highlights the growing trend towards using this treatment in pediatric keratoconic patients. In children, keratoconus tends to be more severe and fast progression is often encountered requiring closer follow-up intervals. Standard cross-linking shows comparable results in children with a good safety-efficacy profile during follow-up periods of up to three years. Further research is needed to standardize and evaluate transepithelial and accelerated cross-linking protocols as these could be of tremendous help in a population where cooperation and compliance are major issues. PMID:26491663

  18. Stromal haze after combined riboflavin-UVA corneal collagen cross-linking in keratoconus: in vivo confocal microscopic evaluation.

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    Mazzotta, Cosimo; Balestrazzi, Angelo; Baiocchi, Stefano; Traversi, Claudio; Caporossi, Aldo

    2007-08-01

    The technique of corneal collagen cross-linking consists of photopolymerization of stromal fibres by the combined action of a photosensitizing substance (riboflavin or vitamin B2) and ultraviolet light from a solid state UVA source. Photopolymerization increases the rigidity of corneal collagen and its resistance to keratectasia. In this report we present two cases, studied through in vivo confocal microscopy, with stage III keratoconus that developed stromal haze after the cross-linking treatment.

  19. Morphological and functional correlations in riboflavin UV A corneal collagen cross-linking for keratoconus.

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    Mazzotta, Cosimo; Caporossi, Tomaso; Denaro, Rosario; Bovone, Cristina; Sparano, Caterina; Paradiso, Anna; Baiocchi, Stefano; Caporossi, Aldo

    2012-05-01

    To investigate the correlations between corneal structural modifications assessed by in vivo corneal confocal microscopy with visual function [uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA)] and morphological data (corneal topography, pachymetry, elevation analysis) after riboflavin UV A corneal collagen cross-linking (CXL) for the stabilization of progressive keratoconus. Forty-four eyes with progressive keratoconus were enrolled in the Siena Eye Cross Study (prospective nonrandomized phase II open trial). All eyes underwent Riboflavin UV A CXL. Preoperative and postoperative evaluation comprised: UCVA, BSCVA, optical pachymetry (Visante OCT, Zeiss, Germany), corneal topography (CSO, Florence, Italy) and tomography (Orbscan IIz; B&L, Rochester, NY, USA) and in vivo confocal microscopy (Heidelberg Retina Tomograph II; Rostock, Heidelberg Gmbh, Germany). Examinations were performed preoperatively 6 months and one day before treatment and at 1, 3, 6 and 12 months of follow-up. In vivo corneal confocal microscopy showed time-dependent postoperative epithelial and stromal modifications after cross-linking. Epithelial thinning associated with stromal oedema and keratocytes apoptosis explained initial tendency towards slightly reduced VA and more glare one month postoperatively in 70% of eyes. Furthermore, a statistically not significant early worsening of topographic mean K values was observed. Orbscan II analysis significantly underestimated pachymetric values after treatment. Pachymetric underestimation was rectified by high-resolution optical pachymetry provided by the Visante OCT system. After the third post-CXL month, epithelial thickening, disappearance of oedema and new collagen compaction recorded by in vivo corneal confocal microscopy explained the improvements in visual performance during the follow-up. Changes in stromal reflectivity and collagen compaction observed by in vivo confocal microscopy were associated with corneal

  20. In vivo Confocal Microscopy Report after Lasik with Sequential Accelerated Corneal Collagen Cross-Linking Treatment.

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    Mazzotta, Cosimo; Balestrazzi, Angelo; Traversi, Claudio; Caragiuli, Stefano; Caporossi, Aldo

    2014-01-01

    We report the first pilot qualitative confocal microscopic analysis of a laser in situ keratomileusis (Lasik) treatment combined with sequential high-fluence accelerated corneal collagen cross-linking, denominated Lasik XTra, by means of HRT II laser scanning in vivo confocal microscopy after a 6-month follow-up. After obtaining approval from the Siena University Hospital Institutional Review Board, a 33-year-old female patient underwent a Lasik XTra procedure in her left eye. Confocal analysis demonstrated induced slight corneal microstructural changes by the interaction between UV-A, riboflavin and corneal stromal collagen, beyond the interface to a depth of 160 µm, without adverse events at the interface and endothelial levels. This application may be considered a prophylactic biomechanical treatment, stiffening the intermediate corneal stroma to prevent corneal ectasia and stabilizing the clinical results of refractive surgery. According to our preliminary experiences, this combined approach may be useful in higher-risk Lasik patients for hyperopic treatments, high myopia and lower corneal thicknesses.

  1. In vivo Confocal Microscopy Report after Lasik with Sequential Accelerated Corneal Collagen Cross-Linking Treatment

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    Cosimo Mazzotta

    2014-04-01

    Full Text Available We report the first pilot qualitative confocal microscopic analysis of a laser in situ keratomileusis (Lasik treatment combined with sequential high-fluence accelerated corneal collagen cross-linking, denominated Lasik XTra, by means of HRT II laser scanning in vivo confocal microscopy after a 6-month follow-up. After obtaining approval from the Siena University Hospital Institutional Review Board, a 33-year-old female patient underwent a Lasik XTra procedure in her left eye. Confocal analysis demonstrated induced slight corneal microstructural changes by the interaction between UV-A, riboflavin and corneal stromal collagen, beyond the interface to a depth of 160 µm, without adverse events at the interface and endothelial levels. This application may be considered a prophylactic biomechanical treatment, stiffening the intermediate corneal stroma to prevent corneal ectasia and stabilizing the clinical results of refractive surgery. According to our preliminary experiences, this combined approach may be useful in higher-risk Lasik patients for hyperopic treatments, high myopia and lower corneal thicknesses.

  2. Collagen cross-linking using rose bengal and green light to increase corneal stiffness.

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    Cherfan, Daniel; Verter, E Eri; Melki, Samir; Gisel, Thomas E; Doyle, Francis J; Scarcelli, Giuliano; Yun, Seok Hyun; Redmond, Robert W; Kochevar, Irene E

    2013-05-13

    Photochemical cross-linking of corneal collagen is an evolving treatment for keratoconus and other ectatic disorders. We evaluated collagen cross-linking by rose bengal plus green light (RGX) in rabbit eyes and investigated factors important for clinical application. Rose bengal (RB, 0.1%) was applied to deepithelialized corneas of enucleated rabbit eyes for 2 minutes. The diffusion distance of RB into the stroma was measured by fluorescence microscopy on frozen sections. RB-stained corneas were exposed to green (532-nm) light for 3.3 to 9.9 minutes (50-150 J/cm(2)). Changes in the absorption spectrum during the irradiation were recorded. Corneal stiffness was measured by uniaxial tensiometry. The spatial distribution of the stromal elastic modulus was assessed by Brillouin microscopy. Viable keratocytes were counted on H&E-stained sections 24 hours posttreatment. RB penetrated approximately 100 μm into the corneal stroma and absorbed >90% of the incident green light. RGX (150 J/cm(2)) increased stromal stiffness by 3.8-fold. The elastic modulus increased in the anterior approximately 120 μm of stroma. RB was partially photobleached during the 2-minute irradiation, but reapplication of RB blocked light transmission by >70%. Spectral measurements suggested that RGX initiated cross-linking by an oxygen-dependent mechanism. RGX did not decrease keratocyte viability. RGX significantly increases cornea stiffness in a rapid treatment (≅12 minutes total time), does not cause toxicity to keratocytes and may be used to stiffen corneas thinner than 400 μm. Thus, RGX may provide an attractive approach to inhibit progression of keratoconus and other ectatic disorders.

  3. Iontophoresis-Assisted Corneal Collagen Cross-Linking with Epithelial Debridement: Preliminary Results

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    Legrottaglie, Emanuela F.

    2016-01-01

    Purpose. To report the early outcomes of iontophoresis-assisted corneal collagen cross-linking procedure with epithelial debridement (I-SCXL). Methods. Twenty eyes of twenty patients with progressive keratoconus were included in this prospective clinical study. Best spectacle corrected visual acuity (BSCVA), sphere and cylinder refraction, corneal topography, Scheimpflug tomography, aberrometry, anterior segment optical coherence tomography (AS-OCT), and endothelial cell count were assessed at baseline and at 1, 3, and 6 months of follow-up. The parameters considered to establish keratoconus progression were always proven with differential maps as change in curvature in the cone area of at least 1 diopter obtained with an instantaneous map. Results. Functional parameters showed a significant improvement (p 0.05). Conclusion. The early results indicate that the I-SCXL may be able to reduce the treatment time and improve the riboflavin diffusion. PMID:27547758

  4. Iontophoresis-Assisted Corneal Collagen Cross-Linking with Epithelial Debridement: Preliminary Results

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    Paolo Vinciguerra

    2016-01-01

    Full Text Available Purpose. To report the early outcomes of iontophoresis-assisted corneal collagen cross-linking procedure with epithelial debridement (I-SCXL. Methods. Twenty eyes of twenty patients with progressive keratoconus were included in this prospective clinical study. Best spectacle corrected visual acuity (BSCVA, sphere and cylinder refraction, corneal topography, Scheimpflug tomography, aberrometry, anterior segment optical coherence tomography (AS-OCT, and endothelial cell count were assessed at baseline and at 1, 3, and 6 months of follow-up. The parameters considered to establish keratoconus progression were always proven with differential maps as change in curvature in the cone area of at least 1 diopter obtained with an instantaneous map. Results. Functional parameters showed a significant improvement (p0.05. Conclusion. The early results indicate that the I-SCXL may be able to reduce the treatment time and improve the riboflavin diffusion.

  5. Changes in corneal topography and biomechanical properties after collagen cross linking for keratoconus: 1-year results

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    Mohammadreza Sedaghat

    2015-01-01

    Full Text Available Purpose: To evaluate changes in corneal topography and biomechanical properties after collagen cross-linking (CXL for progressive keratoconus. Patients and Methods: Collagen cross-linking was performed on 97 eyes. We assessed uncorrected visual acuity (UCVA and best corrected visual acuity (BCVA. Corneal topography indices were evaluated using placido disc topography, scanning slit anterior topography (Orbscan II, and rotating Scheimpflug topography (Pentacam. Specular microscopy and corneal biomechanics were evaluated. Results: A 1-year-follow-up results revealed that UCVA improved from 0.31 to 0.45 and BCVA changed from 0.78 to 0.84 (P < 0.001. The mean of average keratometry value decreased from 49.62 to 47.95 D (P < 0.001. Astigmatism decreased from 4.84 to 4.24 D (P < 0.001. Apex corneal thickness decreased from 458.11 to 444.46 mm. Corneal volume decreased from 56.66 to 55.97 mm 3 (P < 0.001. Posterior best fit sphere increased from 55.50 to 46.03 mm (P = 0.025. Posterior elevation increased from 99.2 to 112.22 mm (P < 0.001. Average progressive index increased from 2.26 to 2.56 (P < 0.001. A nonsignificant decrease was observed in mean endothelial count from 2996 to 2928 cell/mm 2 (P = 0.190. Endothelial coefficient of variation (CV increased nonsignificantly from 18.26 to 20.29 (P = 0.112. Corneal hysteresis changed from 8.18 to 8.36 (P = 0.552 and corneal resistance factor increased from 6.98 to 7.21(P = 0.202, so these changes were not significant. Conclusion: Visual acuity and K values improved after CXL. In spite of the nonsignificant increase in endothelial cell count and increase in the CV, CLX seems to be a safe treatment for keratoconus. Further studies with larger sample sizes and longer follow-up periods are recommended.

  6. Efficacy of Intrastromal Corneal Ring Segments Combined With Flash Collagen Cross-Linking in Keratoconus.

    Science.gov (United States)

    Gordillo, Carlos H; Grandin, Juan C; Zaldivar, Roger; Zaldivar, Roberto; Lotfi, Adriana C

    2017-02-01

    To evaluate outcomes, efficacy, and safety of intrastromal corneal ring segment implantation for treatment of keratoconus combined with collagen cross-linking (CXL) with 1-year follow-up. One hundred nineteen eyes of 82 patients with keratoconus (37 females) underwent femtosecond (Intralase FS; Abbott Medical Optics, Inc) laser-assisted intrastromal corneal ring segment implantation (INTRASEG; Gamma Vision) with flash CXL (18 mW/cm for 5 minutes). The outcome measures were uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), subjective refractive error, keratometry values, and corneal thickness. Mean age of patients at implantation was 31 years (range 12-63, SD 9.5). According to the Amsler-Krumeich scale of keratoconus severity, 62 eyes were type 1 (52%), 43 eyes, type 2 (36%), and 14 eyes, type 3 (11.8%). Statistically significant improvement of UDVA/CDVA and reduction in the mean cylinder and mean keratometry at 1 year were observed. Mean UDVA (logMAR) was 1.11 ± 0.61 (SD) preoperatively and 0.54 ± 0.58 (SD) postoperatively (P keratoconus. The variety of options in thickness and arc length of the segments enables more precise correction of keratoconus and refractive errors.

  7. Corneal Collagen Cross-Linking in Pellucid Marginal Degeneration: 2 Patients, 4 Eyes

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    Serife Bayraktar

    2015-01-01

    Full Text Available Purpose. To report the long-term results of corneal collagen cross-linking (CXL with riboflavin and ultraviolet-A irradiation in 4 eyes of 2 patients affected by pellucid marginal degeneration (PMD. Methods. This study involved the retrospective analysis of 4 eyes of 2 patients with PMD that underwent CXL treatment. Of the eyes, three had only CXL treatment and one had CXL treatment after an intrastromal corneal ring segment implantation. We have pre- and postoperatively evaluated uncorrected distance visual acuity (UDVA, best corrected distance visual acuity (BCDVA, corneal topography (Pentacam, specular microscopy, and pachymetry. Results. Patient 1 was a woman, aged 35, and Patient 2 was a man, aged 33. The right eye of Patient 1 showed an improvement in her BCDVA, from 16/40 to 18/20 in 15 months, and her left eye improved from 12/20 to 18/20 in 20 months. Patient 2’s right eye showed an improvement in his BCDVA, from 18/20 to 20/20 in 43 months, and his left eye improved from 16/20 to 18/20 in 22 months. No complications were recorded during or after the treatment. Conclusion. CXL is a safe tool for the management of PMD, and it can help to stop the progression of this disease.

  8. Corneal collagen cross-linking in keratoconus: A systematic review and meta-analysis

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    Chunyu, Tian; Xiujun, Peng; Zhengjun, Fan; Xia, Zhang; Feihu, Zhou

    2014-01-01

    The aim of this study was to determine the effectiveness of corneal collagen cross-linking (CXL) for the treatment of progressive keratoconus (KC). Some of the published literature, including a few small, randomized controlled trials (RCTs), demonstrated good results after CXL, but large RCTs with long-term follow-up to establish a cause-effect relationship are lacking. Using PubMed, EMBASE, and the Cochrane Library database, we searched for relevant studies published between October 2007 and March 2014. A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify the effectiveness of CXL for treating KC. The primary outcome parameters included uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), refraction, corneal topography, and corneal thickness at baseline and at 1, 3, 6, 12, and 18 months after CXL. A total of 1171 participants (1557 eyes) were enrolled in this meta-analysis. CXL may be effective in halting the progress of KC for at least 12 months under certain conditions. However, further research from randomized trials is needed to confirm our findings. PMID:25007895

  9. Research advances of corneal collagen cross linking%角膜胶原交联术研究进展

    Institute of Scientific and Technical Information of China (English)

    赵旭东; 高晓唯

    2011-01-01

    Corneal collagen cross-linking, which increases corneal mechanical strength to prevent the progress of keratoconus,is the first treatment to control the progression of keratoconus effectively. Witii recent studies, the security of corneal cross-linking has been widely recognized. With the continuous development of this technique, the indications also expanded. This article not only reviews its principles, indications, complications and contraindications,but also summarizes the technique of corneal collagen cross-linking in recent years.%目的 角膜胶原交联术(corneal collagen cross linking,CXL)是第一种能有效控制圆锥角膜选展的治疗方法,通过核黄素/紫外光介导的角膜胶原交联,增加角膜的机械强度,阻止了圆锥角膜的进展.经过近年来的研究,CXL的安全性得到了广泛的认可,随着技术方法不断改进,治疗范围也有所扩大.本文就近年来对于CXL原理、适应证、并发症、禁忌证的研究进展进行了综述.

  10. Corneal wound healing after ultraviolet-A/riboflavin collagen cross-linking: a rabbit study.

    Science.gov (United States)

    Salomão, Marcella Q; Chaurasia, Shyam S; Sinha-Roy, Abhijit; Ambrósio, Renato; Esposito, Andrew; Sepulveda, Ricardo; Agrawal, Vandana; Wilson, Steven E

    2011-06-01

    To investigate corneal wound healing following ultraviolet-A (UVA)/riboflavin corneal collagen cross-linking (CXL) in rabbit corneas. Thirty-six rabbits were enrolled in the study. Animals were divided into three treatment groups and corneas were analyzed at 24 hours and 4 weeks postoperatively. Thus, each group had 6 rabbits at each time point. Treatment groups were: 1) standard UVA+riboflavin CXL, 2) UVA alone, and 3) riboflavin alone. One eye of each rabbit served as an untreated control eye. TUNEL assay was performed to detect stromal cell apoptosis. Immunocytochemistry was performed to detect the inflammatory marker CD11b expressed in monocytes and the alpha-smooth muscle actin (SMA) marker expressed in myofibroblasts. At 24 hours, corneas from the UVA+riboflavin CXL group had significantly more apoptosis than the UVA alone and riboflavin alone groups. Eyes from all three groups had significantly more inflammatory cell influx into the cornea than unwounded controls. Four weeks after the procedure, many corneas in the UVA+riboflavin CXL group had mild haze, but very few SMA-positive myofibroblasts could be detected in the central cornea. Riboflavin+UVA CXL triggers more anterior keratocyte apoptosis than corneal scrape with UVA alone or riboflavin alone. Inflammation monitored by the monocyte marker CD11b was present, but not statistically different among the three groups. Very little myofibroblast generation could be detected after UVA+riboflavin CXL, indicating that the mild stromal haze associated with this procedure is normally related to transient corneal fibroblast generation rather than more persistent haze due to generation of myofibroblasts. Copyright 2011, SLACK Incorporated.

  11. A constant-force technique to measure corneal biomechanical changes after collagen cross-linking.

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    Olivier Richoz

    Full Text Available PURPOSE: To introduce a constant-force technique for the analysis of corneal biomechanical changes induced after collagen cross-linking (CXL that is better adapted to the natural loading in the eye than previous methods. METHODS: For the biomechanical testing, a total of 50 freshly enucleated eyes were obtained and subdivided in groups of 5 eyes each. A Zwicki-Line Testing Machine was used to analyze the strain of 11 mm long and 5 mm wide porcine corneal strips, with and without CXL. Before material testing, the corneal tissues were pre-stressed with 0.02 N until force stabilization. Standard strip extensiometry was performed as control technique. For the constant-force technique, tissue elongation (Δ strain, % was analyzed for 180 seconds while different constant forces (0.25 N, 0.5 N, 1 N, 5 N were applied. RESULTS: Using a constant force of 0.5 N, we observed a significant difference in Δstrain between 0.26±0.01% in controls and 0.12±0.03% in the CXL-treated group (p = 0.003 over baseline. Similarly, using a constant force of 1 N, Δstrain was 0.31±0.03% in controls and 0.19±0.02% after CXL treatment (p = 0.008. No significant differences were observed between CXL-treated groups and controls with 0.25 N or 5 N constant forces. Standard stress-strain extensiometry failed to show significant differences between CXL-treated groups and controls at all percentages of strains tested. CONCLUSION: We propose a constant-force technique to measure corneal biomechanics in a more physiologic way. When compared to standard stress-strain extensiometry, the constant-force technique provides less variability and thus reaches significant results with a lower sample number.

  12. New techniques to improve classical corneal collagen cross-linking treatment

    Institute of Scientific and Technical Information of China (English)

    Li Na; Peng Xiujun; Fan Zhengjun; Xia Yu; Wu Tengfei

    2014-01-01

    Objective The aim of this review is to comprehensively and unbiasedly summarize the improvements in the techniques for classical corneal collagen cross-linking (CXL) by covering the reasons for this improvement,measure,and effect to approach the future direction of the CXL.Data sources All articles used in this review were mainly retrieved from the PubMed database.Study selection Original articles and reviews were selected if they were related to the improvement in the technique of classical CXL.Data were mainly extracted from 94 articles,which are listed in the reference section of this review.Results This innovative research involves every step such as instrument preparation,epithelial management,riboflavin instillation,and UVA irradiation.These clinical and experimental results seem promising.Conclusions CXL treatment is the only recent promising method for preventing the progress of keratoconus.The limitations and potential complications that accompany classical CXL such as corneal thickness limitations,ultraviolet-A (UVA) light injury,and the impact of de-epithelialization encourage people to research new improvements in techniques.While this research needs to be further investigated,we hope our review can help related researchers and patients.

  13. Does Corneal Collagen Cross-linking Reduce the Need for Keratoplasties in Patients With Keratoconus?

    Science.gov (United States)

    Sandvik, Gunhild Falleth; Thorsrud, Andreas; Råen, Marianne; Østern, Atle E; Sæthre, Marit; Drolsum, Liv

    2015-09-01

    To investigate whether the introduction of corneal collagen cross-linking (CXL) influences the frequency of keratoplasties in patients with keratoconus. Data were obtained from a cohort of patients from our corneal transplant registry. Two different periods were compared, 2005 to 2006 (period 1) and 2013 to 2014 (period 2). Patients during period 1 had surgery before the introduction of CXL treatment, and patients in period 2 had surgery after this treatment was well established in our department. Age and gender were registered, and the Amsler-Krumeich classification system was applied to grade the degree of keratoconus. The total number of keratoplasties performed during period 1 was 137, and keratoconus was the cause of surgery in 55 eyes (55 patients). The corresponding numbers in period 2 were 231 and 26 eyes (26 patients), respectively. The difference in the number of keratoplasties for keratoconus in both periods was statistically significant (P = 0.003). There were no significant differences in the distributions of age and gender between both periods. In period 1, 63.6% of the eyes were graded as stage 4 in the Amsler-Krumeich classification, compared with 96.2% in period 2 (P = 0.001). The frequency of keratoplasty for keratoconus has been more than halved in our department over the last decade. There is reason to believe that this reduction is for a great part caused by the introduction of CXL treatment.

  14. Corneal Collagen Cross-Linking for Keratoconus in Pediatric Patients-Long-Term Results.

    Science.gov (United States)

    Padmanabhan, Prema; Rachapalle Reddi, Sudhir; Rajagopal, Rama; Natarajan, Radhika; Iyer, Geetha; Srinivasan, Bhaskar; Narayanan, Niveditha; Lakshmipathy, Meena; Agarwal, Shweta

    2017-02-01

    To report the long-term outcome of corneal collagen cross-linking (CXL) for progressive keratoconus in pediatric patients. "Epithelium-off" CXL was performed in pediatric eyes with progressive keratoconus. Spectacle-corrected distance visual acuity (CDVA), retinoscopy, topography, and tomography were documented preoperatively and postoperatively at 3 months, 6 months, 1 year, and annually thereafter. A total of 377 eyes of 336 pediatric patients aged 8 to 18 years with progressive keratoconus underwent CXL. Of these, 194 eyes had a follow-up beyond 2 years and up to 6.7 years. At last follow-up, there was significant improvement in mean CDVA from 0.33 ± 0.22 to 0.27 ± 0.19 logMAR (P ≤ 0.0001), reduction in mean topographic astigmatism from 7.22 ± 3.55 to 6.13 ± 3.28 D (P = 0.0001), mean flattening of 1.20 ± 3.55 diopters in maximum keratometry (Kmax) (P = 0.0002), and mean corneal thinning of 31.1 ± 36.0 μm (P keratoconus (average keratometry 48-53 diopters). Central cones showed more corneal flattening than peripheral cones. Stabilization or flattening of Kmax was seen in 85% of eyes at 2 years and in 76% after 4 years. Stabilization or improvement of CDVA was seen in 80.1% of eyes at 2 years and in 69.1% after 4 years. CXL remains effective in stabilizing keratoconus for longer than 2 years in a majority of pediatric eyes. Flattening of Kmax was greater in moderately advanced keratoconus and central cones. Long-term follow-up beyond 4 years, however, revealed that a few eyes showed features suggestive of reversal of the effect of CXL.

  15. Corneal Collagen Cross-Linking with Hypoosmolar Riboflavin Solution in Keratoconic Corneas

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    Shaofeng Gu

    2014-01-01

    Full Text Available Purpose. To report the 12-month outcomes of corneal collagen cross-linking (CXL with a hypoosmolar riboflavin and ultraviolet-A (UVA irradiation in thin corneas. Methods. Eight eyes underwent CXL using a hypoosmolar riboflavin solution after epithelial removal. The corrected distance visual acuity (CDVA, manifest refraction, the mean thinnest corneal thickness (MTCT, and the endothelial cell density (ECD were evaluated before and 6 and 12 months after CXL. Results. The MTCT was 413.9 ± 12.4 μm before treatment and reduced to 381.1 ± 7.3 μm after the removal of the epithelium. After CXL, the thickness decreased to 410.3 ± 14.5 μm at the last follow-up. Before treatment, the mean K-value of the apex of the keratoconus corneas was 58.7 ± 3.5 diopters and slightly decreased (57.7 ± 4.9 diopters at 12 months. The mean CDVA was 0.54 ± 0.23 logarithm of the minimal angle of resolution before treatment and increased to 0.51 ± 0.21 logarithm at the last follow-up. The ECD was 2731.4 ± 191.8 cells/mm2 before treatment and was 2733.4 ± 222.6 cells/mm2 at 12 months after treatment. Conclusions. CXL with a hypoosmolar riboflavin in thin corneas seems to be a promising method for keratoconic eyes with the mean thinnest corneal thickness less than 400 μm without epithelium.

  16. Accelerated corneal collagen cross-linking should be modified

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    Kymionis GD

    2014-11-01

    Full Text Available George D Kymionis,1,2 Konstantinos I Tsoulnaras11Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece; 2Bascom Palmer Eye Institute, University of Miami, Miller School of Medicine, Miami, FL, USAWe have read with interest the recently published comparative study regarding the accelerated versus conventional corneal collagen cross-linking (CXL in the treatment of mild keratoconus. We would like to underline the importance of the CXL treatment time reduction in this time consuming operation.1 Accelerated CXL became popular due to patient and doctor comfort in comparison to the previously widespread use of Dresden protocol which is successful in terms of safety and efficacy. Based on the Bunsen-Roscoe law of reciprocity many modifications to the time and irradiation settings have been proposed while the total energy dose delivered to the cornea should be maintained at 5.4 J/cm2.2View original paper by Sherif

  17. Collagen cross linking: Current perspectives

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    Srinivas K Rao

    2013-01-01

    Full Text Available Keratoconus is a common ectatic disorder occurring in more than 1 in 1,000 individuals. The condition typically starts in adolescence and early adulthood. It is a disease with an uncertain cause and its progression is unpredictable, but in extreme cases, vision deteriorates and can require corneal transplant surgery. Corneal collagen cross-linking (CCL with riboflavin (C3R is a recent treatment option that can enhance the rigidity of the cornea and prevent disease progression. Since its inception, the procedure has evolved with newer instrumentation, surgical techniques, and is also now performed for expanded indications other than keratoconus. With increasing experience, newer guidelines regarding optimization of patient selection, the spectrum of complications and their management, and combination procedures are being described. This article in conjunction with the others in this issue, will try and explore the uses of collagen cross-linking (CXL in its current form.

  18. Riboflavin-UVA-induced corneal collagen cross-linking in pediatric patients.

    Science.gov (United States)

    Caporossi, Aldo; Mazzotta, Cosimo; Baiocchi, Stefano; Caporossi, Tomaso; Denaro, Rosario; Balestrazzi, Angelo

    2012-03-01

    Evaluation of stability and functional response after riboflavin-UVA–induced cross-linking in a population of patients younger than 18 years with progressive keratoconus after 36 months of follow-up. Prospective nonrandomized phase II open trial conducted at the Department of Ophthalmology, Siena University, Italy. The "Siena CXL Pediatrics" trial involved 152 patients aged 18 years or younger (10–18 years) with clinical and instrumental evidence of keratoconus progression. The population was divided into 2 groups according to corneal thickness (>450 and 450 μm) and +0.14 and +0.15 Snellen lines, respectively, in the thinner group (corneal thickness <450 μm). Patients in the latter group already showed a better and faster functional recovery than the thicker group at 3-month follow-up. Topographic results showed statistically significant improvement in K readings and asymmetry index values. Coma reduction was also statistically significant. The study demonstrated significant and rapid functional improvement in pediatric patients younger than 18 years with progressive keratoconus, undergoing riboflavin-UVA–induced cross-linking. In pediatric age, a good functional response and keratoconus stability was obtained after corneal cross-linking in a 36-month follow-up.

  19. A case of in vivo iontophoresis-assisted corneal collagen cross-linking for keratoconus: An immunohistochemical study.

    Science.gov (United States)

    Manetti, Mirko; Favuzza, Eleonora; Sgambati, Eleonora; Mencucci, Rita; Marini, Mirca

    2017-04-01

    The standard corneal collagen cross-linking (CXL), that includes the removal of corneal epithelium to permit adequate penetration of riboflavin in the stroma, is an established procedure to halting keratoconus progression. However, as epithelial removal may cause postoperative pain and an increased risk of corneal infection, new therapeutic approaches have been proposed. Iontophoresis is a recently developed non-invasive technique which provides the use of electrical current during CXL to enhance transepithelial penetration of riboflavin into the corneal stroma. Here, we describe for the first time the morphological changes of the corneal stromal compartment in a patient with keratoconus who underwent in vivo iontophoresis-assisted CXL (ionto-CXL) before full-thickness corneal transplantation. Immunohistochemistry for type I collagen and CD34 was performed to investigate the stromal distribution of collagen fibers and keratocytes, respectively. The histology of ionto-CXL-treated keratoconic cornea, collected 6 months after the intervention, was compared with that of healthy corneas and either untreated or standard CXL-treated keratoconic corneas. An attempt to restore a normal stromal architecture was observed in the ionto-CXL-treated cornea compared with untreated keratoconic corneas. In particular, the ionto-CXL-treated cornea showed a parallel distribution of type I collagen fibers, although fiber interweaving appeared less organized than in healthy corneas and standard CXL-treated keratoconic corneas. Moreover, the distribution of CD34-positive keratocytes was improved in keratoconic corneas following ionto-CXL treatment, though a scattered CD34 immunoreactivity was still noticeable in the subepithelial stroma. This study provides histological evidence that ionto-CXL may represent a non-invasive alternative in the management of progressive keratoconus in adults. Copyright © 2017 Elsevier GmbH. All rights reserved.

  20. Clinical Observation of Transepithelial Corneal Collagen Cross-linking by Iontophoresis of Riboflavin in Treatment of Keratoconus

    Institute of Scientific and Technical Information of China (English)

    Na Li; Zhengjun Fan; Xiujun Peng; Xu Pang; Chunyu Tian

    2014-01-01

    Purpose: To evaluate the efficacy and safety of transepithelial collagen cross-linking by iontophoretic delivery of riboflavin in treatment of progressive keratoconus.Methods:.Eleven patients (15 eyes) with progressive kerato-conus were enrolled. After 0.1% riboflavin-distilled water so-lution was deliveried via transepithelial iontophpresis for 5 min with 1 mA current, and ultraviolet radiation (370 nm,.3 mW /cm2) was performed at a 1.5 cm distance for 30 min. The fol-low up were 6 months in all eyes. The uncorrected visual acu-ity, corrected visual acuity,endothelial cell counting, corneal thickness,.intraocular pressure, corneal curvature, corneal to-pography,.OCT and corneal opacity before and 6-month after surgery were analyzed.Results: At 6 month postoperatively, mean uncorrected visual acuity and corrected visual acuity changed from 0.36 to 0.30 and from 0.42 to 0.57 without statistical significance..The mean value of each index of corneal curvature declined with-out statistical significance.Kmax value dereased from 60.91 to 59.91, and the astigmatism declined from 3.86 to 3.19. Cen-tral corneal thickness decreased from 460.93 μm to 455.40μm,.and thinnest corneal thickness declined from 450.87 μm to 440.60 μm with no statistical significance..Intraocular pres-sure was significantly elevated from 10.85 mmHg to 12.62 mmHg. Endothelial cell count did not change significantly. No corneal haze occurred. Mean depth of corneal demarcation line was 288.46 μm at 1 month postoperatively..Conclusion:.Transepithelial corneal collagen cross-linking by iontophoresis is effective and safe in the treatment of progres-sive keratoconus, and yields stable clinical outcomes during 6-month follow up..However,.long-term follow up is urgently required. (Eye Science 2014; 29:160-164)

  1. The influence of corneal collagen cross-linking on anterior chamber in keratoconus.

    Science.gov (United States)

    Polat, Nihat; Gunduz, Abuzer; Colak, Cemil

    2017-04-01

    This study aimed to evaluate the effect of the corneal changes following corneal cross-linking (CXL) on the anterior chamber in keratoconus patients. Forty-five eyes of 32 patients who had been diagnosed with progressive keratoconus and had undergone CXL were included in this retrospective study. The thinnest corneal thickness of the progressive keratoconus patients included in the study was >400 μ. The preoperative (T0), postoperative 6th month (T1), and postoperative 1st year (T2) anterior chamber volume (ACV), anterior chamber angle (ACA), and anterior chamber depth (ACD) scheimpflug imaging values were obtained for each eye. The mean T0 ACV value was 182.79 ± 36.68 mmwhile the T1 value was 201.25 ± 41.73 mm3 and the T2 value was 208.40 ± 42.69 mm3 with a statistically significant difference between the periods (P = 0.001). The mean T0 ACA value was 38.64° ±5.85°, increasing to 41.45° ±4.83° in the T1 and 42.10° ± 4.84° in the T2. The T0 value was significantly lower than the post-CXL values (P = 0.003). The mean ACD value was 3.73 ± 0.29 mm at the T0 and 3.82 ± 0.38 mm at the T1 and 3.84 ± 0.36 mm at the T2. The pre-CXL values were significantly lower than the post-CXL values (P = 0.001). The improvement of corneal parameters by CXL in keratoconus patients can have a positive effect on anterior chamber parameters as well. This effect becomes marked at the postoperative first 6-month evaluation.

  2. Late onset post-LASIK keratectasia with reversal and stabilization after use of latanoprost and corneal collagen cross-linking

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    Tor Paaske Utheim

    2012-01-01

    Full Text Available We report a case of late onset keratectasia after laser in situ keratomileusis (LASIK and its quick reversal and stabilization after use of latanoprost and riboflavin/ultraviolet-A corneal collagen cross-linking (CXL. A 39-year-old man with normal intraocular pressure developed a rapid deterioration of vision in his left eye 6 years after LASIK-retreatment for high myopic astigmatism. Keratectasia was diagnosed by corneal topography and ultrasound pachymetry. After two months of treatment with latanoprost and a minor intraocular pressure reduction, uncorrected distance visual acuity improved from 20/100 to 20/20 and corneal topography showed reversal of keratectasia. CXL was performed after the reversal to achieve long-term stabilization. At 1, 3, 6, 13 and 39 months followup exams after the CXL, stable vision, refraction, and topography were registered. This case shows that keratectasia may rapidly occur several years after LASIK and that a quick reversal and stabilization may be achieved by use of latanoprost followed by CXL.

  3. Management of pediatric keratoconus – Evolving role of corneal collagen cross-linking: An update

    Science.gov (United States)

    Kankariya, Vardhaman P; Kymionis, George D; Diakonis, Vasilios F; Yoo, Sonia H

    2013-01-01

    Pediatric keratoconus demonstrates several distinctive management issues in comparison with adult keratoconus with respect to under-diagnosis, poor compliance and modifications in treatment patterns. The major concerns comprise of the accelerated progression of the disease in the pediatric age group and management of co-morbidities such as vernal keratoconjuntivitis. Visual impairment in pediatric patients may affect social and educational development and overall negatively impact their quality of life. The treatment algorithm between adults and pediatric keratoconus has been similar; comprising mainly of visual rehabilitation with spectacles, contacts lenses (soft or rigid) and keratoplasty (lamellar or penetrating) depending on the stage of the disease. There is a paradigm shift in the management of keratoconus, a new treatment modality, corneal collagen crosslinking (CXL), has been utilized in adult keratoconic patients halting the progression of the disease. CXL has been utilized for over a 10 year period and based on the evidence of efficacy and safety in the adult population; this treatment has been recently utilized in management of pediatric keratoconus. This article will present an update about current management of pediatric keratoconus with special focus on CXL in this age group. PMID:23925333

  4. Management of pediatric keratoconus - Evolving role of corneal collagen cross-linking: An update

    Directory of Open Access Journals (Sweden)

    Vardhaman P Kankariya

    2013-01-01

    Full Text Available Pediatric keratoconus demonstrates several distinctive management issues in comparison with adult keratoconus with respect to under-diagnosis, poor compliance and modifications in treatment patterns. The major concerns comprise of the accelerated progression of the disease in the pediatric age group and management of co-morbidities such as vernal keratoconjuntivitis. Visual impairment in pediatric patients may affect social and educational development and overall negatively impact their quality of life. The treatment algorithm between adults and pediatric keratoconus has been similar; comprising mainly of visual rehabilitation with spectacles, contacts lenses (soft or rigid and keratoplasty (lamellar or penetrating depending on the stage of the disease. There is a paradigm shift in the management of keratoconus, a new treatment modality, corneal collagen crosslinking (CXL, has been utilized in adult keratoconic patients halting the progression of the disease. CXL has been utilized for over a 10 year period and based on the evidence of efficacy and safety in the adult population; this treatment has been recently utilized in management of pediatric keratoconus. This article will present an update about current management of pediatric keratoconus with special focus on CXL in this age group.

  5. Corneal endothelial changes after accelerated corneal collagen cross-linking in keratoconus and postLASIK ectasia

    Science.gov (United States)

    Badawi, Amani E

    2016-01-01

    Purpose The purpose of this study was to evaluate the effects of accelerated cross-linking (CXL) on corneal endothelium in keratoconus and postlaser-assisted in situ keratomileusis (LASIK) ectasia. Design This study is a prospective nonrandomized controlled study. Setting This study was conducted in Mansoura Ophthalmic Center (Mansoura University) and Al-Mostakbal Ophthalmic Center, Mansoura, Egypt. Methods In total, 40 eyes with progressive keratoconus and 10 eyes with postLASIK ectasia were subjected to an accelerated CXL (10 mW/cm2 for 9 minutes). Qualitative and quantitative analyses of the corneal endothelial cells were conducted before CXL and 3, 6, and 12 months after CXL by using a specular microscope (Tomy EM-3000). Results There was a significant reduction in endothelial cell count particularly at 3 and 6 months postCXL. In addition, the coefficient of variance was also statistically significantly higher at 3 and 6 months postoperatively than the preCXL value. There was a slight change in the percentage of hexagonal cells. Conclusion The use of accelerated CXL (10 mW/cm2 for 9 minutes) has a transient negative impact on endothelial cell density and/or endothelial morphology. PMID:27757009

  6. Evaluation of Corneal Stromal Demarcation Line after Two Different Protocols of Accelerated Corneal Collagen Cross-Linking Procedures Using Anterior Segment Optical Coherence Tomography and Confocal Microscopy

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    Engin Bilge Ozgurhan

    2014-01-01

    Full Text Available Purpose. To evaluate the depth of corneal stromal demarcation line using AS-OCT and confocal microscopy after two different protocols of accelerated corneal collagen cross-linking procedures (CXL. Methods. Patients with keratoconus were divided into two groups. Peschke CXL device (Peschke CCL-VARIO Meditrade GmbH applied UVA light with an intended irradiance of 18.0 mW/cm2 for 5 minutes after applying riboflavin for 20 minutes (group 1 and 30 minutes (group 2. One month postoperatively, corneal stromal demarcation line was measured using AS-OCT and confocal microscopy. Results. This study enrolled 34 eyes of 34 patients (17 eyes in group 1 and 17 eyes in group 2. The mean depth of the corneal stromal demarcation line was 208.64±18.41 μm in group 1 and 240.37±18.89 μm in group 2 measured with AS OCT, while it was 210.29±18.66 μm in group 1 and 239.37±20.07 μm in group 2 measured with confocal microscopy. Corneal stromal demarcation line depth measured with AS OCT or confocal microscopy was significantly deeper in group 2 than group 1 (P<0.01. Conclusion. The group in which riboflavin was applied for 30 minutes showed significantly deeper corneal stromal demarcation line than the group in which riboflavin was applied for 20 minutes.

  7. Corneal collagen cross-linking with riboflavin and ultraviolet - A light for keratoconus: Results in Indian eyes

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    Agrawal Vinay

    2009-01-01

    Full Text Available Aim: To assess the results of corneal collagen cross-linking with riboflavin using ultraviolet - A light for keratoconus at one year in Indian eyes. Materials and Methods: Sixty-eight eyes of 41 patients with progressive keratoconus were included in this retrospective study. All eyes completed was 12 months of follow-up and 37 eyes had a one-year follow-up. The maximum follow-up was 16 months. Ocular examinations including refraction, best corrected visual acuity (BCVA, corneal topography, were recorded at each visit. Results: The mean age was 16.9 ± 3.5 years (range 12-39 years and the mean follow-up was 10.05 ± 3.55 months (range six to 16 months. Thirty seven eyes with a follow-up of at least 12 months were analyzed. The preoperative values on the day of treatment were compared with postoperative values of the 12-month examination. This showed that BCVA improved at least one line in 54% (20/37 of eyes and remained stable in 28% (10/37 of eyes ( P =0.006. Astigmatism decreased by a mean of 1.20 diopter (D in 47% (17/37 of eyes ( P =0.005 and remained stable (within ± 0.50 D in 42% (15/37 of eyes. The K value of the apex decreased by a mean of 2.73 D in 66% (24/37 of eyes ( P =0.004 and remained stable (within ± 0.50 D in 22% (8/37 of eyes. The maximum K value decreased by a mean of 2.47 D in 54% (20/37 of eyes ( P =0.004 and remained stable (within ± 0.50 D in 38% (14/37 of eyes. Corneal Wavefront analysis revealed that spherical and higher-order aberrations did not show significant variations in the follow-up period. The coma component showed a very significant reduction at six months after treatment and persisted throughout the follow-up period ( P =0.003 Conclusion: The results show a stabilization and improvement in keratoconus after collagen cross-linking in Indian eyes. This suggests that it is an effective treatment for progressive keratoconus.

  8. The Long-term Clinical Outcome after Corneal Collagen Cross-linking in Korean Patients with Progressive Keratoconus.

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    Kim, Tae Gi; Kim, Ki Young; Han, Jung Bin; Jin, Kyung Hyun

    2016-10-01

    To evaluate the long-term clinical effectiveness and safety of corneal collagen cross-linking (CXL) in progressive keratoconus compared with untreated contralateral eyes. In this retrospective study, nine eyes of nine patients with progressive keratoconus who received CXL (treatment group) and nine untreated contralateral eyes with keratoconus (control group) were included. All patients were followed for at least 5 years and assessed with best-corrected visual acuity, maximum keratometry, mean keratometry, corneal astigmatism, and corneal thickness. Clinical data were collected preoperatively and at 1, 3, 6, 12, 24, 36, 48, and 60 months, postoperatively. Mean best-corrected visual acuity improved significantly from 0.58 ± 0.37 logarithm of minimum angle of resolution preoperatively to 0.39 ± 0.29 logarithm of minimum angle of resolution at 5 years after corneal CXL (p = 0.012). There was significant flattening of the maximum keratometry and mean keratometry from preoperative values of 63.39 ± 10.89 and 50.87 ± 6.27 diopter (D) to postoperative values of 60.89 ± 11.29 and 49.54 ± 7.23 D, respectively (p = 0.038, 0.021). Corneal astigmatism decreased significantly from 7.20 ± 1.83 D preoperatively to 5.41 ± 1.79 D postoperatively (p = 0.021). The thinnest corneal thickness decreased from 434.00 ± 54.13 to 365.78 ± 71.58 µm during 1 month after treatment, then increased to 402.67 ± 52.55 µm at 5 years, which showed a statistically significant decrease compared to the baseline (p = 0.020). In the untreated contralateral eyes, mean keratometry increased significantly at 2 years compared with the baseline (p = 0.043). CXL seems to be an effective and safe treatment for halting the progression of keratoconus over a long-term follow-up period of up to 5 years in progressive keratoconus.

  9. Treatment of progressive keratoconus by riboflavin-UVA-induced cross-linking of corneal collagen: ultrastructural analysis by Heidelberg Retinal Tomograph II in vivo confocal microscopy in humans.

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    Mazzotta, Cosimo; Balestrazzi, Angelo; Traversi, Claudio; Baiocchi, Stefano; Caporossi, Tomaso; Tommasi, Cristina; Caporossi, Aldo

    2007-05-01

    To assess ultrastructural stromal modifications after riboflavin-UVA-induced cross-linking of corneal collagen in patients with progressive keratoconus. This was a second-phase prospective nonrandomized open study in 10 patients with progressive keratoconus treated by riboflavin-UVA-induced cross-linking of corneal collagen and assessed by means of Heidelberg Retinal Tomograph II Rostock Corneal Module (HRT II-RCM) in vivo confocal microscopy. The eye in the worst clinical condition was treated for each patient. Treatment under topical anesthesia included corneal deepithelization (9-mm diameter) and instillation of 0.1% riboflavin phosphate-20% dextran T 500 solution at 5 minutes before UVA irradiation and every 5 minutes for a total of 30 minutes. UVA irradiation was 7 mm in diameter. Patients were assessed by HRT II-RCM confocal microscopy in vivo at 1, 3, and 6 months after treatment. Rarefaction of keratocytes in the anterior and intermediate stroma, associated with stromal edema, was observed immediately after treatment. The observation at 3 months after the operation detected keratocyte repopulation in the central treated area, whereas the edema had disappeared. Cell density increased progressively over the postoperative period. At approximately 6 months, keratocyte repopulation was complete, accompanied by increased density of stromal fibers. No endothelial damage was observed at any time. Reduction in anterior and intermediate stromal keratocytes followed by gradual repopulation has been confirmed directly in vivo in humans by HRT II-RCM confocal microscopy after riboflavin-UVA-induced corneal collagen cross-linking.

  10. A short-term study of corneal collagen cross-linking with hypo-osmolar riboflavin solution in keratoconic corneas

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    Shao-Feng Gu

    2015-02-01

    Full Text Available AIM: To report the 3mo outcomes of collagen cross-linking (CXL with a hypo-osmolar riboflavin in thin corneas with the thinnest thickness less than 400 μm without epithelium. METHODS: Eight eyes in 6 patients with age 26.2±4.8y were included in the study. All patients underwent CXL using a hypo-osmolar riboflavin solution after its de-epithelization. Best corrected visual acuity, manifest refraction, the thinnest corneal thickness, and endothelial cell density were evaluated before and 3mo after the procedure. RESULTS: The mean thinnest thickness of the cornea was 408.5±29.0 μm before treatment and reduced to 369.8±24.8 μm after the removal of epithelium. With the application of the hypo-osmolar riboflavin solution, the thickness increased to 445.0±26.5 μm before CXL and recover to 412.5±22.7 μm at 3mo after treatment, P=0.659. Before surgery, the mean K-value of the apex of the keratoconus corneas was 57.6±4.0 diopters, and slightly decreased (54.7±4.9 diopters after surgery (P=0.085. Mean best-corrected visual acuity was 0.55±0.23 logarithm of the minimal angle of resolution, and increased to 0.53±0.26 logarithm after surgery (P=0.879. The endothelial cell density was 2706.4±201.6 cells/mm2 before treatment, and slightly decreased (2641.2±218.2 cells/mm2 at last fellow up (P=0.002. CONCLUSION: Corneal collagen cross-linking with a hypo-osmolar riboflavin in thin corneas seems to be a promising treatment. Further study should be done to evaluate the safety and efficiency of CXL in thin corneas for the long-term.

  11. Monitoring of cornea elastic properties changes during UV-A/riboflavin-induced corneal collagen cross-linking using supersonic shear wave imaging: a pilot study.

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    Nguyen, Thu-Mai; Aubry, Jean-François; Touboul, David; Fink, Mathias; Gennisson, Jean-Luc; Bercoff, Jeremy; Tanter, Mickael

    2012-08-31

    Keratoconus disease or post-LASIK corneal ectasia are increasingly treated using UV-A/riboflavin-induced corneal collagen cross-linking (CXL). However, this treatment suffers from a lack of techniques to provide an assessment in real-time of the CXL effects. Here, we investigated the potential interest of corneal elasticity as a biomarker of the efficacy of this treatment. For this purpose, supersonic shear wave imaging (SSI) was performed both ex vivo and in vivo on porcine eyes before and after CXL. Based on ultrasonic scanners providing ultrafast frame rates (~30 kHz), the SSI technique generates and tracks the propagation of shear waves in tissues. It provides two- and three-dimensional (2-D and 3-D) quantitative maps of the corneal elasticity. After CXL, quantitative maps of corneal stiffness clearly depicted the cross-linked area with a typical 200-μm lateral resolution. The CXL resulted in a 56% ± 15% increase of the shear wave speed for corneas treated in vivo (n = 4). The in vivo CXL experiments performed on pigs demonstrated that the quantitative estimation of local stiffness and the 2-D elastic maps of the corneal surface provide an efficient way to monitor the local efficacy of corneal cross-linking.

  12. Corneal thickness changes during corneal collagen cross-linking with UV-A irradiation and hypo-osmolar riboflavin in thin corneas

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    Belquiz Amaral Nassaralla

    2013-06-01

    Full Text Available PURPOSE: To evaluate the thinnest corneal thickness changes during and after corneal collagen cross-linking treatment with ultraviolet-A irradiation, using hypo-osmolar riboflavin solution in thin corneas. METHODS: Eighteen eyes of 18 patients were included in this study. After epithelium removal, iso-osmolar 0.1% riboflavin solution was instilled to the cornea every 3 minutes for 30 minutes. Hypo-osmolar 0.1% riboflavin solution was then applied every 20 seconds for 5 minutes or until the thinnest corneal thickness reached 400 µm. Ultraviolet-A irradiation was performed for 30 minutes. During irradiation, iso-osmolar 0.1% riboflavin drops were applied every 5 minutes. Ultrasound pachymetry was performed at approximately the thinnest point of the cornea preoperatively, after epithelial removal, after iso-osmolar riboflavin instillation, after hypo-osmolar riboflavin instillation, after ultraviolet-A irradiation, and at 1, 6 and 12 months after treatment. RESULTS: Mean preoperative thinnest corneal thickness was 380 ± 11 µm. After epithelial removal it decreased to 341 ± 11 µm, and after 30 minutes of iso-osmolar 0.1% riboflavin drops, to 330 ± 7.6 µm. After hypo-osmolar 0.1% riboflavin drops, mean thinnest corneal thickness increased to 418 ± 11 µm. After UVA irradiation, it was 384 ± 10 µm. At 1, 6 and 12 months after treatment, it was 372 ± 10 µm, 381 ± 12.7, and 379 ± 15 µm, respectively. No intraoperative, early postoperative, or late postoperative complications were noted. CONCLUSIONS: Hypo-osmolar 0.1% riboflavin solution seems to be effective for swelling thin corneas. The swelling effect is transient and short acting. Corneal thickness should be monitored throughout the procedure. Larger sample sizes and longer follow-up are required in order to make meaningful conclusions regarding safety.

  13. Corneal collagen cross-linking for progressive keratoconus in patients aged 9 to 14

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    Fernando Plazzi Palis

    2016-04-01

    Full Text Available RESUMO Objetivo: Determinar a segurança e eficácia do cross-linking corneano (CXL em pacientes de 9 a 14 anos de idade com ceratocone progressivo. Métodos: Dezesseis olhos de onze pacientes (8 homens e 3 mulheres com ceratocone progressivo foram submetidos ao CXL, de acordo com o protocolo padrão de Dresden. A média do tempo de seguimento foi de 26 meses (variando de 12 a 60 meses. Os exames pré e pós-operatórios incluíram: acuidade visual sem correção (AVSC, melhor acuidade visual com correção (AVCC, topografia corneana, tonometria, refração, paquimetria corneana, e contagem de células endoteliais. Resultados: Na última visita de acompanhamento ambulatorial, a AVCC melhorou pelo menos uma linha na tabela de Snellen em 6 olhos (37,5% e permaneceu estável em 9 olhos (56,25%. Dois olhos (12,5% de pacientes que coçam os olhos com frequência, exigiram retratamento devido à progressão do ceratocone, 15 e 28 meses após o primeiro CXL. A refração e contagem de células endoteliais mantiveram-se estáveis. Os resultados topográficos mostraram melhora estatisticamente significativa nos valores do K máximo até dois anos após o CXL. No entanto, houve perda de significância ao longo do tempo. Nenhuma complicação peroperatória foi observada. Dois olhos (12,5% apresentaram haze grau I, que regrediu após um mês de terapia com esteróide tópico. Conclusão: Neste estudo com pacientes selecionados, de 9 a 14 anos de idade, o CXL mostrou ser uma opção segura e eficaz para o tratamento do ceratocone progressivo. No entanto, o efeito pode não ser duradouro, podendo ser necessário um novo tratamento. Maior amostragem e maior seguimento são necessários para verificar esta tendência.

  14. Combined femtosecond laser-assisted intracorneal ring segment implantation and corneal collagen cross-linking for correction of keratoconus

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    Ibrahim O

    2016-03-01

    Full Text Available Osama Ibrahim,1 Ahmed Elmassry,1 Amr Said,1,2 Moones Abdalla,2 Hazem El Hennawi,1 Ihab Osman1 1Department of Ophthalmology, Alexandria University, Alexandria, Egypt; 2Roayah Vision Correction Center, Alexandria, Egypt Purpose: To assess the safety, predictability, and effectiveness of Keraring intrastromal corneal ring segments (ICRS insertion assisted by femtosecond laser and corneal collagen cross-linking (CXL for keratoconus correction. Patients and methods: In this prospective, noncomparative, and interventional case series, 160 eyes of 100 adult keratoconus patients with poor best-corrected visual acuity (BCVA (less than 0.7 and intolerance to contact lens wear were included. Patients underwent femtosecond laser-assisted placement of ICRS and CXL. All patients were examined for a complete ophthalmological test: uncorrected visual acuity (UCVA, BCVA, spherical equivalent, keratometry (K1-flat and K2-steep, pachymetry, and Scheimpflug imaging with the Pentacam at 1 week and at 1, 3, and 6 months postoperatively. Results: At 6 months, a significant difference was observed (P<0.001 in mean UCVA and BCVA from 0.92±0.677 and 0.42±0.600 logMAR preoperatively to 0.20±0.568 and 0.119±0.619 logMAR, respectively. Mean spherical equivalent refractions were significantly lower (P<0.001 at 6 months. Mean keratometry (K also significantly reduced (P<0.001 from 50.93±5.53 D (K1-flat and 55.37±5.76 D (K2-steep to 47.32±4.61 and 51.08±5.38 D, respectively. In terms of pachymetry, no significant difference was observed preoperatively versus postoperatively (P=1.000. Conclusion: Keraring ICRS insertion assisted by femtosecond laser and corneal CXL provided significant improvement in visual acuity, spherical equivalent, and keratometry, which suggests that it may be effective, safe, and predictable for keratoconus correction. Keywords: keratometry, pachymetry, keratectesia, Pentacam, irregular astigmatism

  15. A short-term study of corneal collagen cross-linking with hypo-osmolar riboflavin solution in keratoconic corneas

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    Shao-Feng; Gu; Zhao-Shan; Fan; Li-Hua; Wang; Xiang-Chen; Tao; Yong; Zhang; Chun-Qin; Wang; Ya; Wang; Guo-Ying; Mu

    2015-01-01

    AIM: To report the 3mo outcomes of collagen crosslinking(CXL) with a hypo-osmolar riboflavin in thin corneas with the thinnest thickness less than 400 μm without epithelium.METHODS: Eight eyes in 6 patients with age 26.2±4.8y were included in the study. All patients underwent CXL using a hypo-osmolar riboflavin solution after its de-epithelization. Best corrected visual acuity, manifest refraction, the thinnest corneal thickness, and endothelial cell density were evaluated before and 3mo after the procedure.RESULTS: The mean thinnest thickness of the cornea was 408.5 ±29.0 μm before treatment and reduced to369.8 ±24.8 μm after the removal of epithelium. With the application of the hypo-osmolar riboflavin solution, the thickness increased to 445.0 ±26.5 μm before CXL and recover to 412.5 ±22.7 μm at 3mo after treatment, P =0.659). Before surgery, the mean K-value of the apex of the keratoconus corneas was 57.6 ±4.0 diopters, and slightly decreased(54.7±4.9 diopters) after surgery(P =0.085). Mean best-corrected visual acuity was 0.55 ±0.23 logarithm of the minimal angle of resolution, and increased to 0.53±0.26 logarithm after surgery(P =0.879).The endothelial cell density was 2706.4 ±201.6 cells/mm2 before treatment, and slightly decreased( 2641. 2 ±218.2 cells/mm2) at last fellow up(P =0.002).CONCLUSION: Corneal collagen cross-linking with a hypo-osmolar riboflavin in thin corneas seems to be a promising treatment. Further study should be done to evaluate the safety and efficiency of CXL in thin corneas for the long-term.

  16. Same-day intrastromal corneal ring segment and collagen cross-linking for ectasia after laser in situ keratomileusis: long-term results.

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    Yildirim, Aydin; Uslu, Hasim; Kara, Necip; Cakir, Hanefi; Gurler, Bulent; Colak, Hatice Nur; Ozgurhan, Engin Bilge

    2014-05-01

    To report the long-term results of combined same-day intrastromal corneal ring segment placement and corneal collagen cross-linking (CXL) for postoperative laser in situ keratomileusis (LASIK) ectasia. Retrospective, interventional case series. This retrospective, interventional cases series was performed in Turkiye Hospital Eye Clinic and the Department of Ophthalmology, Fatih University Medical Faculty Hospital, Istanbul, Turkey. Sixteen eyes of 14 patients with postoperative ectasia after LASIK were enrolled. All consecutive patients were treated with femtosecond laser-assisted intrastromal corneal ring segment implantation and followed by same-day corneal collagen cross-linking for ectasia occurring after LASIK. Main outcome measures included uncorrected distance visual acuity, corrected distance visual acuity, spherical and cylindrical refraction, and simulated keratometry values. The mean age ± standard deviation of the 10 women and 4 men was 33.0 ± 6.5 years (range, 23 to 44 years), and the mean follow-up was 43 months (range, 36 to 62 months). The uncorrected distance visual acuity improved significantly from 1.18 ± 0.42 logarithm of the minimal angle of resolution (logMAR) units to 0.44 ± 0.22 logMAR (P 8 D at the last visit, and the minimum keratometry value decreased from 44.3 ± 4.7 D to 41.5 ± 3.5 D (P < .001 for both). No serious complications were shown during follow-up. Implantation of intrastromal corneal ring segment implantation combined with same-day corneal collagen cross-linking was a safe and effective treatment for ectasia occurring after LASIK. It also significantly improved the visual acuity, refraction, and keratometry values. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Corneal healing after riboflavin ultraviolet-A collagen cross-linking determined by confocal laser scanning microscopy in vivo: early and late modifications.

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    Mazzotta, Cosimo; Traversi, Claudio; Baiocchi, Stefano; Caporossi, Orsola; Bovone, Cristina; Sparano, Maria Caterina; Balestrazzi, Angelo; Caporossi, Aldo

    2008-10-01

    To assess early and late micromorphological modifications of cross-linked corneas in vivo by means of Heidelberg Retinal Tomography (HRT) II confocal microscopy. Prospective nonrandomized open trial. Micromorphological examination of 44 cross-linked keratoconic corneas was performed in vivo by HRT II confocal laser scanning microscopy. Riboflavin ultraviolet (UV)-A-induced corneal collagen cross-linking (CXL) was performed according to the Siena protocol: pilocarpin 1% drops 30 minutes before, topical anesthesia with lidocaine 4% drops 15 minutes before irradiation, mechanical scraping of epithelium (9-mm-diameter area), preirradiation soaking for 10 minutes in riboflavin solution 0.1% (Ricrolin, Sooft, Italy) applied every 2.5 minutes for 30 minutes, 30 minutes exposure to solid-state UVA illuminator (Caporossi; Baiocchi; Mazzotta, X-linker, CSO, Italy), 8-mm-diameter irradiated area, energy delivered 3 mW/cm(2). All patients were examined by confocal scans preoperatively and at the following times after treatment: one, three, and six months, and one, two, and three years. No damage to the limbal region was observed. Epithelial regrowth was complete after four days of soft contact lens bandage. The anatomy of the subepithelial plexus was restored one year after the operation with full corneal sensitivity. Increased density of extracellular matrix in late postoperative period indicated cross-linked collagen to a depth of 340 microm expressed by a late demarcation line. In vivo confocal microscopy showed early and late modification of corneal microstructure after the treatment. The three-year stability of CXL recorded could be related to increased cross-links formation, synthesis of well-structured collagen and new lamellar interconnections.

  18. Corneal Melting after Collagen Cross-Linking for Keratoconus in a Thin Cornea of a Diabetic Patient Treated with Topical Nepafenac: A Case Report with a Literature Review

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    Karim Mohamed-Noriega

    2016-02-01

    Full Text Available Purpose: To report the case of a 50-year-old woman with diabetes that presented with corneal melting and perforation 6 weeks after collagen cross-linking (CxL for keratoconus (KC and postoperative use of nepafenac eye drops, a nonsteroidal anti-inflammatory drug (NSAID. Methods: This is a case report of a patient with diabetes, KC and a thin cornea that had undergone left eye corneal CxL at a different hospital followed by postoperative use of nepafenac eye drops for 6 weeks. Results: The patient presented for the first time to our clinic with left corneal melting, perforation and iris prolapse 6 weeks after corneal CxL and topical nepafenac use. She was treated with a left eye tectonic penetrating keratoplasty, extracapsular cataract extraction, intraocular lens implantation and pupilloplasty. Conclusions: The corneal melting and perforation in this patient was associated with multiple risk factors: (1 nepafenac eye drop use, (2 CxL in a cornea thinner than 400 µm and (3 diabetes. The recommended corneal thickness limits should be respected. Topical NSAIDs should be used with caution if used as postoperative treatment after corneal CxL and in patients with diabetes, epithelial defect or delayed healing, because of the possible increased risk for corneal melting when multiple risk factors are observed.

  19. Ultraviolet-visible light spectral transmittance of rabbit corneas after riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking.

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    Hwang, Ho Sik; Kim, Man Soo

    2013-01-01

    To determine the effect of riboflavin/ultraviolet-A (365 nm) corneal collagen cross-linking on the transmission of the ultraviolet-visible (UV-VIS) light spectrum through the cornea. Twelve New Zealand white male rabbits were used in this research. Cross-linking was performed unilaterally on the right eyes of the animals while only the epithelium was removed on the left eyes as the control. Seven weeks after cross-linking, the animals were euthanized, and the enucleated eyes were processed for transmission spectroscopy. To confirm that the cross-linking procedures was done successfully on the right corneas, the tensile force-extension relationship was measured using six corneas from three of the rabbits after the transmission spectrum was determined. Seven weeks after cross-linking, ten of the 12 rabbits had clear corneas in the cross-linked and control eyes. The two rabbits with neovascularization and granular opacities in the right corneas were not included in subsequent measurements. In the cross-linked corneas, transmittance was 87.57% at 650 nm, and decreased continuously as the wavelength shortened. From 315 nm, the transmittance rapidly decreased and was 35.52% at 300 nm. In the control corneas, transmittance was 95.95% at 650 nm and decreased continuously as the wavelength shortened. Below 315 nm, the transmittance rapidly decreased, to 40.29% at 300 nm. The transmittance of the cross-linking corneas was 10%-20% lower than that of the control corneas. The difference was 8.38% at 650 nm and increased as the wavelength shortened, reaching a maximum of 20.59% at 320 nm, and decreased rapidly to 4.77% at 300 nm. The tensile force-extension relationship showed that a greater force was necessary to extend the cross-linking corneas over 500 µm than that of the control corneas. The transmittance of the cross-linked corneas was 10%-20% lower than that of the control corneas. The difference increased as the wavelength decrease, reaching a maximum at 320 nm and then

  20. Collagen cross-linking in thin corneas

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    Prema Padmanabhan

    2013-01-01

    Full Text Available Collagen cross-linking (CXL has become the standard of care for progressive keratoconus, after numerous clinical studies have established its efficacy and safety in suitably selected eyes. The standard protocol is applicable in eyes which have a minimum corneal thickness of 400 μm after epithelial debridement. This prerequisite was stipulated to protect the corneal endothelium and intraocular tissues from the deleterious effect of ultraviolet-A (UVA radiation. However, patients with keratoconus often present with corneal thickness of less than 400 μm and could have otherwise benefited from this procedure. A few modifications of the standard procedure have been suggested to benefit these patients without a compromise in safety. Transepithelial cross-linking, pachymetry-guided epithelial debridement before cross-linking, and the use of hypoosmolar riboflavin are some of the techniques that have been attempted. Although clinical data is limited at the present time, these techniques are worth considering in patients with thin corneas. Further studies are needed to scientifically establish their efficacy and safety.

  1. Parasurgical therapy for keratoconus by riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen: preliminary refractive results in an Italian study.

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    Caporossi, Aldo; Baiocchi, Stefano; Mazzotta, Cosimo; Traversi, Claudio; Caporossi, Tomaso

    2006-05-01

    To assess the effectiveness of riboflavin-ultraviolet type A rays induced cross-linking of corneal collagen in reducing progression of keratoconus and in improving visual acuity in patients with progressive keratoconus. Department of Ophthalmology, Siena University, Siena, Italy. This was a second-phase prospective nonrandomized open study. Starting in September 2004, 10 eyes of 10 patients (mean age 31.4 years) with bilateral keratoconus were treated by combined riboflavin-ultraviolet type A rays (UVA) collagen cross-linking. Radiant energy was 3 mW/cm2 or 5.4 joule/cm2 for a 30-minute exposure at 1 cm from the corneal apex. A complete ophthalmologic examination (uncorrected visual acuity [UCVA], sphere spectacles corrected visual acuity (SSCVA), best spectacle-corrected visual acuity [BSCVA]) was performed. Patients had corneal computerized topographic examination, linear scan optical tomography, endothelial cell count, ultrasound pachometry, intraocular pressure (IOP) evaluation, and HRT II system confocal microscopy at 1, 2, 3, and 6 months. After treatment, eyes were medicated and dressed with a soft contact lens. Comparative preoperative and postoperative results showed increases of 3.6 lines for UCVA (P = .0000112), 1.85 lines for SSCVA (P = .00065), and 1.66 lines for BSCVA (P = .00071). Topographic analysis showed a mean K reduction of 2.1 +/- 0.13 diopters (D) in the central 3.0 mm. Statistical analysis of IOP and endothelial cell count did not show significant differences. Topo-aberrometric analysis findings of corneal symmetry showed a trend toward increasing corneal symmetry with a major reduction in asymmetry between vertical hemimeridians. Refractive results showed a reduction of about 2.5 D in the mean spherical equivalent, topographically confirmed by the reduction in mean K. Results of surface aberrometric analysis showed improvement in morphologic symmetry with a significant reduction in comatic aberrations.

  2. Research Progress in Corneal Cross-linking Agents

    Institute of Scientific and Technical Information of China (English)

    Na Li; Xiujun Peng; Zhengjun Fan

    2014-01-01

    Corneal collagen cross-linking with UVA-riboflavin is cur-rently the only method for preventing the progression of kera-toconus from the pathological perspective. Topical application of a direct cross-linking agent is now attracting widespread at-tention in clinical settings..This article reviews the research progress in the application of indirect or direct cross-linking agents (e.g., riboflavin, glucose, ribose, glutaraldehyde, formaldehyde,.glyceraldehyde,.short chain aliphatic β-nitro alcohol, and genipin) in the treatment of corneal diseases and analyzes the cross-linking efficacy,.toxicity,.and merits and disadvantages of each cross-linking agent,.providing clinical information for further studies.

  3. Imaging Mass Spectrometry by Matrix-Assisted Laser Desorption/Ionization and Stress-Strain Measurements in Iontophoresis Transepithelial Corneal Collagen Cross-Linking

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    Paolo Vinciguerra

    2014-01-01

    Full Text Available Purpose. To compare biomechanical effect, riboflavin penetration and distribution in transepithelial corneal collagen cross-linking with iontophoresis (I-CXL, with standard cross linking (S-CXL and current transepithelial protocol (TE-CXL. Materials and Methods. The study was divided into two different sections, considering, respectively, rabbit and human cadaver corneas. In both sections corneas were divided according to imbibition protocols and irradiation power. Imaging mass spectrometry by matrix-assisted laser desorption/ionization (MALDI-IMS and stress-strain measurements were used. Forty-eight rabbit and twelve human cadaver corneas were evaluated. Results. MALDI-IMS showed a deep riboflavin penetration throughout the corneal layers with I-CXL, with a roughly lower concentration in the deepest layers when compared to S-CXL, whereas with TE-CXL penetration was considerably less. In rabbits, there was a significant increase (by 71.9% and P=0.05 in corneal rigidity after I-CXL, when compared to controls. In humans, corneal rigidity increase was not significantly different among the subgroups. Conclusions. In rabbits, I-CXL induced a significant increase in corneal stiffness as well as better riboflavin penetration when compared to controls and TE-CXL but not to S-CXL. Stress-strain in human corneas did not show significant differences among techniques, possibly because of the small sample size of groups. In conclusion, I-CXL could be a valid alternative to S-CXL for riboflavin delivery in CXL, preserving the epithelium.

  4. Nursing Experience of Corneal Collagen Cross-linking in Treating Keratoconus%角膜胶原交联术的护理

    Institute of Scientific and Technical Information of China (English)

    王飞鹏; 田碧珊

    2015-01-01

    目的:总结了角膜胶原交联术治疗圆锥角膜的护理及其效果。方法:回顾分析30例(31眼)角膜胶原交联术患者术前术后护理记录及病历资料。结果:30例(31眼)患者病情得到控制,术后恢复理想,术后一个月复查视力都有提高。结论:角膜胶原交联术护理重点在于术前协助患者完善各项检查、相关健康知识宣教及有效的心理护理,术后严密观察病情变化、减轻病人痛苦、预防感染及促进角膜上皮修复治疗。眼科学报2015:30:128-130.%Purpose:..To summarize the nursing experience and clinical efficacy of corneal collagen cross-linking in treating keratoconus. Methods: Preoperative and postoperative nursing and medical record of 30 patients (31 eyes) undergoing corneal collagen cross-linking were retrospectively analyzed. Results: The the severity of diseases in all 30 patients (31 eyes) was properly controlled. All cases were fully recovered. The visual acuity at postoperative one month was improved in all cases. Conclusion: assistance in terms of preoperative examination, education of health knowledge and effective psychological nursing play a pivatol role in the nursing before and after corneal collagen cross-linking. Following surgery, postoperative changes in the the severity of diseases should be strictly observed. Much attention should be diverted to ease patients’ pain, prevent infection and accelerate the healing of corneal epithelium.

  5. Long-term results of riboflavin ultraviolet a corneal collagen cross-linking for keratoconus in Italy: the Siena eye cross study.

    Science.gov (United States)

    Caporossi, Aldo; Mazzotta, Cosimo; Baiocchi, Stefano; Caporossi, Tomaso

    2010-04-01

    To report the long-term results of 44 keratoconic eyes treated by combined riboflavin ultraviolet A collagen cross-linking in the first Italian open, nonrandomized phase II clinical trial, the Siena Eye Cross Study. Perspective, nonrandomized, open trial. After Siena University Institutional Review Board approval, from September 2004 through September 2008, 363 eyes with progressive keratoconus were treated with riboflavin ultraviolet A collagen cross-linking. Forty-four eyes with a minimum follow-up of 48 months (mean, 52.4 months; range, 48 to 60 months) were evaluated before and after surgery. Examinations comprised uncorrected visual acuity, best spectacle-corrected visual acuity, spherical spectacle-corrected visual acuity, endothelial cells count (I Konan, Non Con Robo; Konan Medical, Inc., Hyogo, Japan), optical (Visante OCT; Zeiss, Jena, Germany) and ultrasound (DGH; Pachette, Exton, Pennsylvania, USA) pachymetry, corneal topography and surface aberrometry (CSO EyeTop, Florence, Italy), tomography (Orbscan IIz; Bausch & Lomb Inc., Rochester, New York, USA), posterior segment optical coherence tomography (Stratus OCT; Zeiss, Jena, Germany), and in vivo confocal microscopy (HRT II; Heidelberg Engineering, Rostock, Germany). Keratoconus stability was detected in 44 eyes after 48 months of minimum follow-up; fellow eyes showed a mean progression of 1.5 diopters in more than 65% after 24 months, then were treated. The mean K value was reduced by a mean of 2 diopters, and coma aberration reduction with corneal symmetry improvement was observed in more than 85%. The mean best spectacle-corrected visual acuity improved by 1.9 Snellen lines, and the uncorrected visual acuity improved by 2.7 Snellen lines. The results of the Siena Eye Cross Study showed a long-term stability of keratoconus after cross-linking without relevant side effects. The uncorrected visual acuity and best spectacle-corrected visual acuity improvements were supported by clinical, topographic

  6. One-Year Results of Simultaneous Topography-Guided Photorefractive Keratectomy and Corneal Collagen Cross-Linking in Keratoconus Utilizing a Modern Ablation Software

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    A. M. Sherif

    2015-01-01

    Full Text Available Purpose. To evaluate effectiveness of simultaneous topography-guided photorefractive keratectomy and corneal collagen cross-linking in mild and moderate keratoconus. Methods. Prospective nonrandomized interventional study including 20 eyes of 14 patients with grade 1-2 keratoconus that underwent topography-guided PRK using a Custom Ablation Transition Zone (CATz profile with 0.02% MMC application immediately followed by standard 3 mw/cm2 UVA collagen cross-linking. Maximum ablation depth did not exceed 58 μm. Follow-up period: 12 months. Results. Progressive statistically significant improvement of UCVA from 0.83±0.37 logMAR preoperative, reaching 0.25±0.26 logMAR at 12 months (P<0.001. Preoperative BCVA (0.27±0.31 logMAR showed a progressive improvement reaching 0.08±0.12 logMAR at 12 months (P=0.02. Mean Kmax reduced from 48.9±2.8 to 45.4±3.1 D at 12 months (P<0.001, mean Kmin reduced from 45.9±2.8 D to 44.1±3.2 D at 12 months (P<0.003, mean keratometric asymmetry reduced from 3.01±2.03 D to 1.25±1.2 D at 12 months (P<0.001. The safety index was 1.39 at 12 months and efficacy index 0.97 at 12 months. Conclusion. Combined topography-guided PRK and corneal collagen cross-linking are a safe and effective option in the management of mild and moderate keratoconus. Precis. To our knowledge, this is the first published study on the use of the CATz ablation system on the Nidek Quest excimer laser platform combined with conventional cross-linking in the management of mild keratoconus.

  7. Corneal Collagen Cross-Linking in the Management of Keratoconus in Canada: A Cost-Effectiveness Analysis.

    Science.gov (United States)

    Leung, Victoria C; Pechlivanoglou, Petros; Chew, Hall F; Hatch, Wendy

    2017-08-01

    To use patient-level microsimulation models to evaluate the comparative cost-effectiveness of early corneal cross-linking (CXL) and conventional management with penetrating keratoplasty (PKP) when indicated in managing keratoconus in Canada. Cost-utility analysis using individual-based, state-transition microsimulation models. Simulated cohorts of 100 000 individuals with keratoconus who entered each treatment arm at 25 years of age. Fellow eyes were modeled separately. Simulated individuals lived up to a maximum of 110 years. We developed 2 state-transition microsimulation models to reflect the natural history of keratoconus progression and the impact of conventional management with PKP versus CXL. We collected data from the published literature to inform model parameters. We used realistic parameters that maximized the potential costs and complications of CXL, while minimizing those associated with PKP. In each treatment arm, we allowed simulated individuals to move through health states in monthly cycles from diagnosis until death. For each treatment strategy, we calculated the total cost and number of quality-adjusted life years (QALYs) gained. Costs were measured in Canadian dollars. Costs and QALYs were discounted at 5%, converting future costs and QALYs into present values. We used an incremental cost-effectiveness ratio (ICER = difference in lifetime costs/difference in lifetime health outcomes) to compare the cost-effectiveness of CXL versus conventional management with PKP. Lifetime costs and QALYs for CXL were estimated to be Can$5530 (Can$4512, discounted) and 50.12 QALYs (16.42 QALYs, discounted). Lifetime costs and QALYs for conventional management with PKP were Can$2675 (Can$1508, discounted) and 48.93 QALYs (16.09 QALYs, discounted). The discounted ICER comparing CXL to conventional management was Can$9090/QALY gained. Sensitivity analyses revealed that in general, parameter variations did not influence the cost-effectiveness of CXL. CXL is

  8. Safety and Visual Outcome of Visian Toric ICL Implantation after Corneal Collagen Cross-Linking in Keratoconus: Up to 2 Years of Follow-Up.

    Science.gov (United States)

    Antonios, Rafic; Dirani, Ali; Fadlallah, Ali; Chelala, Elias; Hamade, Adib; Cherfane, Carole; Jarade, Elias

    2015-01-01

    Purpose. To evaluate the long-term safety and clinical outcome of phakic Visian toric implantable collamer lens (ICL) insertion after corneal collagen cross-linking (CXL) in progressive keratoconus. Methods. This was a retrospective study of 30 eyes (19 patients), with progressive keratoconus, who underwent sequential CXL followed by Visian toric ICL implantation after 6 months. Results. At baseline, 6 eyes had stage I, 14 eyes stage II, and 10 eyes stage III keratoconus graded by Amsler-Krumeich classification. At 6 months after CXL, only K (steep) and K (max) decreased significantly from baseline, with no change in visual acuity or refraction. Flattening in keratometric readings was stable thereafter. There was significant improvement in mean uncorrected distance visual acuity (1.57 ± 0.56 to 0.17 ± 0.06 logMAR, P ICL implantation that was maintained at the 2-year follow-up. Mean cylinder power and mean spherical equivalent (SE) also decreased significantly after ICL implantation. A small hyperopic shift in SE (+0.25 D) was observed at 2 years that did not alter visual outcomes. Conclusions. Visian toric ICL implantation following CXL is an effective option for improving visual acuity in patients with keratoconus up to 2 years.

  9. Our experience with Athens protocol - simultaneous topo-guided photorefractive keratectomy followed by corneal collagen cross linking for keratoconus

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    Shreyas Shah

    2016-07-01

    Results: Mean UCVA improved from 0.81 log mar units pre-operatively to 0.43 log mar units at the end of 6 months. Preoperative BCVA was maintained or improved in 37 eyes (94.87% and BCVA decreased by more than 1 line in 2 eyes (5.12% post-operatively. The mean BCVA improved from 0.2 log mar units pre-operatively to 0.1 log mar units at the end of 6 months. The mean preoperative manifest refraction spherical equivalent reduced from -3.1+/-2.3D to -1.4+/-1.3D postoperatively. The mean steepest K reading decreased from 47.8+/-4.2D pre-op to 45+/-3.3D at the end of 6 month. Similarly, mean flat keratometry readings reduced significantly from 44.8+/-3.5D preoperatively to 42.2+/-2.8D at the last follow-up visit postoperatively. Conclusions: Combined topo-guided PRK+CXL is an effective approach in treating patients with keratoconus. It biomechanically stabilizes the cornea, improves the corneal contour, reduces irregular astigmatism and offers a better quality of vision. [Int J Res Med Sci 2016; 4(7.000: 2639-2644

  10. Current status of accelerated corneal cross-linking

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    Michael Mrochen

    2013-01-01

    Full Text Available Corneal cross-linking with riboflavin is a technique to stabilize or reduce corneal ectasia, in diseases such as keratoconus and post-laser-assisted in situ keratomileusis (LASIK ectasia. There is an interest by patient as well as clinicians to reduce the overall treatment time. Especially, the introduction of corneal cross-linking in combination with corneal laser surgery demands a shorter treatment time to assure a sufficient patient flow. The principles and techniques of accelerated corneal cross-linking is discussed.

  11. Management of fungal corneal ulcer by corneal collagen cross-linking technique%角膜交联对真菌性角膜溃疡的治疗作用

    Institute of Scientific and Technical Information of China (English)

    郝兆芹; 宋金鑫; 吴洁; 潘士印; 刘先宁; 程燕; 肖湘华

    2014-01-01

    Background Fungal corneal ulcer is a visual-threatening eye disease,and drug therapy has a limiting efficacy.Corneal transplantation or eye enucleation sometimes is necessary to the severe patients.Corneal collagen cross-linking (CXL) is an effective method for some corneal diseases,but the study on CXL for fungal corneal ulcer is lack.Objective This study was to evaluate the clinical effectiveness and safety CXL for fungal corneal ulcer.Methods Fifteen 8-week-old healthy New Zealand white rabbits were used in this study and other 5 rabbits served as normal controls.Fungal corneal ulcer models were established in the right eyes of other 10 rabbits by infecting sickle bacteria liquid after corneal scratching and removing corneal epithelium,then decellularized ostrich corneal patch covered the defected cornea.The models were randomly divided into the non-treatment group and the CXL treatment group.Corneal lesions were examined under the slit lamp microscope every day,and cornea was pictured by laser scanning confocal microscope on the 3rd,7th,14th,21st and 28th day individually after CXL.All rabbits were sacrificed and corneal tissues were obtained 4 weeks after treatment,and the collagen fiber diameter and fibrocytes were observed under the scanning electron microscope.Results Fungal corneal ulcer models were successfully established by corneal scratching and decellularized ostrich cornea covering.The gray ulcer lesions and hypbae like bean pod were seen by slit lamp microscope and laser scanning confocal microscope 3 days after modeling.Corneal ulcer deepened and expanded 1 week later,and there were a large number of spore and hyphae criss-crossing as short rod in shallow stroma.Inflammatory cells were observed in corneal endothelial cells and ocular anterior chamber.In the CXL treatment group,the range of corneal epithelial deficiency was less than that in the nontreatment group on the 3rd,7th,14th,and 21st (all at P< 0.05).The diameters of collagen fibers were

  12. Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

    Science.gov (United States)

    El Emam, Dalia Sabry; Farag, Rania Kamel; Abouelkheir, Hossam Youssef

    2016-01-01

    Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure. PMID:28127465

  13. Microbial Keratitis After Collagen Cross-linking Treatment

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    Banu Torun Acar

    2012-07-01

    Full Text Available A 33-year-old woman presented with pain, redness, and diminution of vision that occurred 2 days after collagen cross-linking had been performed for keratoconus in the right eye. Culture results from the patient's contact lens and corneal scrapings were positive for Staphylococcus epidermidis. According to the results of antibiotic susceptibility testing, the patient was treated with hourly topical fortified vancomycin and exocin. Before collagen cross-linking, the best-corrected visual acuity (BCVA was 4/10, the manifest refraction was -7.00 -1.755 3°. Four months after the procedure, the BCVA was 4/10, the manifest refraction was -5.50 -1.75 10°. Slit-lamp examination revealed a mild residual haze in the upper midperipheral cornea, and stromal opacities had disappeared. Collagen crosslinking is less invasive compared to other methods for treatment of keratoconus, but epithelial debridement and bandage contact lens wearing may lead to the development of bacterial keratitis. (Turk J Oph thal mol 2012; 42: 300-2

  14. A genetic anomaly of oriented collagen biosynthesis and cross-linking: Keratoconus.

    Science.gov (United States)

    Bourges, J L; Robert, A M; Robert, L

    2015-02-01

    Oriented collagen biosynthesis is one of the major mechanisms involved in tissue and organ formation during development. Corneal biogenesis is one example. Defects in this process lead to anomalies in tissue structure and function. The transparency of cornea and its achievement are a good example as well as its pathological modifications. Keratoconus is one example of this type of pathologies, involving also inappropriate cross-linking of collagen fibers. Among the tentatives to correct this anomaly, the riboflavin-potentiated UV-cross-linking (CXL) of keratoconus corneas appears clinically satisfactory, although none of the experiments and clinical results published prove effective cross-linking. The published results are reviewed in this article.

  15. Corneal cross-linking in a 10-year-old child with stage III keratoconus.

    Science.gov (United States)

    Abbondanza, Marco; Felice, Valentina De; Abbondanza, Gabriele

    2016-07-01

    Keratoconus is a corneal dystrophy characterized by progressive thinning, conical shape of the cornea and irregular astigmatism. It is particularly insidious when it occurs in very young patients. We report the case of a 10-year-old child with an aggressive stage III keratoconus, who was suggested to undergo a Penetrating Keratoplasty. We performed Corneal Collagen Cross-linking with epithelium removal instead, which was successful in arresting the rapid progression of keratoconus. Eighteen months later, Kmax had decreased by 1.3 D, astigmatism by 0.8 D, thinnest pachimetry had improved by 69 μm and CDVA was 20/32. This case confirms that Corneal Collagen Cross-linking is a safe and effective procedure for the treatment of keratoconus even in its aggressive forms. We encourage ophthalmic surgeons to favor conservative treatments when dealing with very young patients. © NEPjOPH.

  16. Corneal Cross-Linking: An Example of Photoinduced Polymerization as a Treatment Modality in Keratoconus.

    Science.gov (United States)

    Kubrak-Kisza, Magdalena; Kisza, Krystian Jerzy; Misiuk-Hojło, Marta

    2016-01-01

    The cornea is one of the principal refractive elements in the human eye and plays a crucial role in the process of vision. Keratoconus is the most common corneal dystrophy, found mostly among young adults. It is characterized by a reduced number of collagen cross-links in the corneal stroma, resulting in reduced biomechanical stability and an abnormal shape of the cornea. These changes lead to progressive myopia, corneal thinning, central scarring and irregular astigmatism, causing severely impaired vision. Hard contact lenses, photorefractive keratectomy or intracorneal rings are the most common treatment options for refractive error caused by keratoconus. However, these techniques do not treat the underlying cause of the corneal ectasia and therefore are not able to stop the progression of the disease. Riboflavin photoinduced polymerization of corneal collagen, also known as corneal cross-linking (CXL), has been introduced as the first therapy which, by stabilizing the structure of the cornea, prevents the progression of keratoconus. It stiffens the cornea using the photo-sensitizer riboflavin in combination with ultraviolet irradiation. This is a current review of the CXL procedure as a therapy for keratoconus, which relies on photoinduced polymerization of human tissue. We have focused on its biomechanical and physiological influences on the human cornea and have reviewed the previous and current biochemical theories behind cross-linking reactions in the cornea.

  17. Advanced Corneal Cross-Linking System with Fluorescence Dosimetry

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    Marc D. Friedman

    2012-01-01

    Full Text Available Purpose. This paper describes an advanced system that combines corneal cross-linking with riboflavin with fluorescence dosimetry, the ability to measure riboflavin diffusion within the cornea both before and during UVA treatment. Methods and Results. A corneal cross-linking system utilizing a digital micromirror device (DMD was assembled and used to measure diffusion coefficients of 0.1% riboflavin in 20% dextran in porcine eyes. A value of (3.3±0.2×10−7 cm2/s was obtained for the stroma. Diffusion coefficients for the transepithelial formulation of 0.1% riboflavin in 0.44% saline and 0.02% BAK were also measured to be 4.7±0.3×10−8 cm2/s for epithelium only and (4.6±0.4×10−7 cm2/s for stroma only. Riboflavin consumption during a UVA treatment was also demonstrated. Conclusion. A new advanced corneal cross-linking system with fluorescence dosimetry of riboflavin has been demonstrated. It is hoped that this method may play a significant role in determining the underlying mechanisms of corneal cross-linking and assist with the development of additional riboflavin formulations. Moreover, dosimetry may prove valuable in providing a method to account for the biological differences between individuals, potentially informing cornea-specific UVA treatment doses in real time.

  18. Scleral lens tolerance after corneal cross-linking for keratoconus

    NARCIS (Netherlands)

    Visser, Esther Simone; Soeters, Nienke; Tahzib, Nayyirih G.

    2015-01-01

    Purpose. Subjective and objective evaluation of scleral lens tolerance and fitting before and after corneal cross-linking (CXL) for progressive keratoconus. Methods. In this prospective cohort, evaluations were made of 18 unilateral eyes in patients who underwent CXL and had been wearing scleral len

  19. Newer protocols and future in collagen cross-linking

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    Arthur B Cummings

    2013-01-01

    Full Text Available Corneal Cross-Linking (CXL is an established surgical procedure for the treatment of corneal disorders such as corneal ectasia and keratoconus. This method of treatment stabilises the corneal structure and increases rigidity, reducing the requirement for corneal transplantation. Since its development, many scientific studies have been conducted to investigate ways of improving the procedure. Biomechanical stability of the cornea after exposure to UV-A light, and the effect of shortening procedure time has been some of the many topics explored

  20. The management of cornea blindness from severe corneal scarring, with the Athens Protocol (transepithelial topography-guided PRK therapeutic remodeling, combined with same-day, collagen cross-linking

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    Kanellopoulos AJ

    2012-02-01

    Full Text Available Anastasios John KanellopoulosLaservision.gr Institute, Athens, Greece; Manhattan Eye, Ear and Throat Hospital, New York, NY, USA; New York University Medical School, New York, NY, USAPurpose: To evaluate the safety and efficacy of combined transepithelial topography-guided photorefractive keratectomy (PRK therapeutic remodeling, combined with same-day, collagen cross-linking (CXL. This protocol was used for the management of cornea blindness due to severe corneal scarring.Methods: A 57-year-old man had severe corneal blindness in both eyes. Both corneas had significant central scars attributed to a firework explosion 45 years ago, when the patient was 12 years old. Corrected distance visual acuity (CDVA was 20/100 both eyes (OU with refraction: +4.00, –4.50 at 135° in the right eye and +3.50, –1.00 at 55° in the left. Respective keratometries were: 42.3, 60.4 at 17° and 35.8, 39.1 at 151.3°. Cornea transplantation was the recommendation by multiple cornea specialists as the treatment of choice. We decided prior to considering a transplant to employ the Athens Protocol (combined topography-guided partial PRK and CXL in the right eye in February 2010 and in the left eye in September 2010. The treatment plan for both eyes was designed on the topography-guided wavelight excimer laser platform.Results: Fifteen months after the right eye treatment, the right cornea had improved translucency and was topographically stable with uncorrected distance visual acuity (UDVA 20/50 and CDVA 20/40 with refraction +0.50, –2.00 at 5°. We noted a similar outcome after similar treatment applied in the left eye with UDVA 20/50 and CDVA 20/40 with –0.50, –2.00 at 170° at the 8-month follow-up.Conclusion: In this case, the introduction of successful management of severe cornea abnormalities and scarring with the Athens Protocol may provide an effective alternative to other existing surgical or medical options.Keywords: Athens Protocol, collagen cross-linking

  1. Collagen cross-linking in the treatment of pellucid marginal degeneration

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    Ziad Hassan

    2014-01-01

    Full Text Available Pellucid marginal degeneration (PMD is an uncommon cause of inferior peripheral corneal thinning disorder, characterized by irregular astigmatism. We analyzed a case of bilateral PMD patient and treated one eye with corneal collagen cross-linking (CXL therapy. Corneal topography was characteristic for PMD. Visual acuity, slitlamp examinations, tonometry, and corneal thickness were observed. Simulated keratometric and topographic index values were detected with corneal topography. Uncorrected, LogMAR visual acuity has improved from +0.8 to +0.55 during the 6 months and +0.3 during the 8 months follow-up after CXL. Pachymetry values and intraocular pressure showed no changes. Keratometric values and topografic indexes disclosed no progression of the disease. CXL may postpone or eliminate the need of corneal transplantation in cases with PMD.

  2. Long-term results of cornea collagen cross-linking with riboflavin for keratoconus

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    Vinay Agrawal

    2013-01-01

    Full Text Available Corneal collagen cross-linking with riboflavin and UVA light (CXL is the only method designed to arrest the progression of keratoconus. Visual improvement generally starts 3 months after treatment. Reduction is coma seen on aberrometry in early postoperative phase is also responsible for the improvement in visual acuity. In the light of currently available data we can thus say that CXL is a safe procedure that is successful in arresting keratoconus.

  3. The theory and art of corneal cross-linking

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    Rebecca McQuaid

    2013-01-01

    Full Text Available Before the discovery of corneal cross-linking (CXL, patients with keratoconus would have had to undergo corneal transplantation, or wear rigid gas permeable lenses (RGPs that would temporarily flatten the cone, thereby improving the vision. The RGP contact lens (CL would not however alter the corneal stability and if the keratoconus was progressive, the continued steepening of the cone would occur under the RGP CL. To date, the Siena Eye has been the largest study to investigate long term effects of standard CXL. Three hundred and sixty-three eyes were treated and monitored over 4 years, producing reliable long-term results proving long-term stability of the cornea by halting the progression of keratoconus, and proving the safety of the procedure. Traditionally, CXL requires epithelial removal prior to corneal soakage of a dextran-based 0.1% riboflavin solution, followed by exposure of ultraviolet-A (UV-A light for 30 min with an intensity of 3 mW/cm2. A series of in vitro investigations on human and porcine corneas examined the best treatment parameters for standard CXL, such as riboflavin concentration, intensity, wavelength of UV-A light, and duration of treatment. Photochemically, CXL is achieved by the generation of chemical bonds within the corneal stroma through localized photopolymerization, strengthening the cornea whilst minimizing exposure to the surrounding structures of the eye. In vitro studies have shown that CXL has an effect on the biomechanical properties of the cornea, with an increased corneal rigidity of approximately 70%. This is a result of the creation of new chemical bonds within the stroma.

  4. Corneal crossed links: a new alternative in the treatment of ectasia

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    Maygret Alberro Hernández

    2009-09-01

    Full Text Available Cross-linking a technique that allows increasing the creation of covalent links through the process of photo-oxidation among the collagen fibers and enhance the corneal biomechanical stabilization. The main objective of this procedure is to stop the development of ectasia. The indications include the Keratoconus and Pellucid Marginal Degeneration. This can reduce the necessity for permanent keratoplasty and is highly efficient in the treatment and prophylaxis of keratectasia after ablation caused by laser. Many reviewed articles prove the security and efficacy of this treatment. The confocal microscopy techniques have shown significant swelling and resistance of corneal stroma after this procedure. Density of endothelial cell and transparency of the cornea and crystallin remain unchanged. This is a simple, safe and non-invasive technique with promising results. Since this is not expensive it could be particularly useful in developing countries where corneal transplant and other procedures are very expensive.

  5. Collagen/elastin hydrogels cross-linked by squaric acid.

    Science.gov (United States)

    Skopinska-Wisniewska, J; Kuderko, J; Bajek, A; Maj, M; Sionkowska, A; Ziegler-Borowska, M

    2016-03-01

    Hydrogels based on collagen and elastin are very valuable materials for medicine and tissue engineering. They are biocompatible; however their mechanical properties and resistance for enzymatic degradation need to be improved by cross-linking. Up to this point many reagents have been tested but more secure reactants are still sought. Squaric acid (SqAc), 3,4-dihydroxy 3-cyclobutene 1,2-dione, is a strong, cyclic acid, which reacts easily with amine groups. The properties of hydrogels based on collagen/elastin mixtures (95/5, 90/10) containing 5%, 10% and 20% of SqAc and neutralized via dialysis against deionized water were tested. Cross-linked, 3-D, transparent hydrogels were created. The cross-linked materials are stiffer and more resistant to enzymatic degradation than those that are unmodified. The pore size, swelling ability and surface polarity are reduced due to 5% and 10% of SqAc addition. At the same time, the cellular response is not significantly affected by the cross-linking. Therefore, squaric acid would be regarded as a safe, effective cross-linking agent.

  6. Riboflavin-ultraviolet a corneal cross-linking for keratoconus

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    El-Raggal Tamer

    2009-01-01

    Full Text Available Purpose: To evaluate the safety, efficacy of riboflavin-ultraviolet A irradiation (UVA corneal cross-linking and present refractive changes induced by the treatment in cases of keratoconus. Materials and Methods: The study includes 15 eyes of 9 patients with keratoconus with an average keratometric (K reading less than 54 D and minimal corneal thickness greater than 420 microns. The corneal epithelium was removed manually within the central 8.5 mm diameter area and the cornea was soaked with riboflavin eye drops (0.1% in 20% dextran t-500 for 30 minutes followed by exposure to UVA radiation (365 nm, 3 mW/cm 2 for 30 minutes. During the follow-up period, uncorrected visual acuity (UCVA, best spectacle-corrected visual acuity (BSCVA, manifest refraction, slit lamp examination and topographic changes were recorded at the first week, first month, 3 and 6 months. Results: There was statistically significant improvement of UCVA from a preoperative mean of 0.11 ± 0.07 (range 0.05-0.3 to a postoperative mean of 0.15 ± 0.06 (range 0.1-0.3 (P < 0.05. None of the eyes lost lines of preoperative UCVA but 1 eye lost 1 line of preoperative BSCVA. The preoperative mean K of 49.97 ± 2.81 D (range 47.20-51.75 changed to 48.34 ± 2.64 D (range 45.75-50.40. This decrease in K readings was statistically significant (P < 0.05. All eyes developed minimal faint stromal haze that cleared in 14 eyes within 1 month. In only 1 eye, this resulted in a very faint corneal scar. Other sight threatening complications were not encountered in this series. Progression of the original disease was not seen in any of the treated eyes within 6 months of follow-up. Conclusion: Riboflavin-UVA corneal cross-linking is a safe and promising method for keratoconus. Larger studies with longer follow up are recommended.

  7. Evaluation of Epithelial Integrity with Various Transepithelial Corneal Cross-Linking Protocols for Treatment of Keratoconus

    Directory of Open Access Journals (Sweden)

    Suphi Taneri

    2014-01-01

    Full Text Available Purpose. Corneal collagen cross-linking (CXL has been demonstrated to stiffen cornea and halt progression of ectasia. The original protocol requires debridement of central corneal epithelium to facilitate diffusion of a riboflavin solution to stroma. Recently, transepithelial CXL has been proposed to reduce risk of complications associated with epithelial removal. Aim of the study is to evaluate the impact of various transepithelial riboflavin delivery protocols on corneal epithelium in regard to pain and epithelial integrity in the early postoperative period. Methods. One hundred and sixty six eyes of 104 subjects affected by progressive keratoconus underwent transepithelial CXL using 6 different riboflavin application protocols. Postoperatively, epithelial integrity was evaluated at slit lamp and patients were queried regarding their ocular pain level. Results. One eye had a corneal infection associated with an epithelial defect. No other adverse event including endothelial decompensation or endothelial damage was observed, except for epithelial damages. Incidence of epithelial defects varied from 0 to 63%. Incidence of reported pain varied from 0 to 83%. Conclusion. Different transepithelial cross-linking protocols have varying impacts on epithelial integrity. At present, it seems impossible to have sufficient riboflavin penetration without any epithelial disruption. A compromise between efficacy and epithelial integrity has to be found.

  8. Femtosecond laser collagen cross-linking without traditional photosensitizers

    Science.gov (United States)

    Guo, Yizang; Wang, Chao; Celi, Nicola; Vukelic, Sinisa

    2015-03-01

    Collagen cross-linking in cornea has the capability of enhancing its mechanical properties and thereby providing an alternative treatment for eye diseases such as keratoconus. Currently, riboflavin assisted UVA light irradiation is a method of choice for cross-link induction in eyes. However, ultrafast pulsed laser interactions may be a powerful alternative enabling in-depth treatment while simultaneously diminishing harmful side effects such as, keratocyte apoptosis. In this study, femtosecond laser is utilized for treatment of bovine cornea slices. It is hypothesized that nonlinear absorption of femtosecond laser pulses plays a major role in the maturation of immature cross-links and the promotion of their growth. Targeted irradiation with tightly focused laser pulses allows for the absence of a photosensitizing agent. Inflation test was conducted on half treated porcine cornea to identify the changes of mechanical properties due to laser treatment. Raman spectroscopy was utilized to study subtle changes in the chemical composition of treated cornea. The effects of treatment are analyzed by observing shifts in Amide I and Amide III bands, which suggest deformation of the collagen structure in cornea due to presence of newly formed cross-links.

  9. Collagen telopeptides (cross-linking sites) play a role in collagen gel lattice contraction

    Science.gov (United States)

    Woodley, D. T.; Yamauchi, M.; Wynn, K. C.; Mechanic, G.; Briggaman, R. A.

    1991-01-01

    Solubilized interstitial collagens will form a fibrillar, gel-like lattice when brought to physiologic conditions. In the presence of human dermal fibroblasts the collagen lattice will contract. The rate of contraction can be determined by computer-assisted planemetry. The mechanisms involved in contraction are as yet unknown. Using this system it was found that the rate of contraction was markedly decreased when collagen lacking telopeptides was substituted for native collagen. Histidinohydroxylysinonorleucine (HHL) is a major stable trifunctional collagen cross-link in mature skin that involves a carboxyl terminal, telopeptide site 16c, the sixteenth amino acid residue from the carboxy terminal of the telopeptide region of alpha 1 (I) in type I collagen. Little, if any, HHL was present in native, purified, reconstituted, soluble collagen fibrils from 1% acetic acid-extracted 2-year-old bovine skin. In contrast, HHL cross-links were present (0.22 moles of cross-link per mole of collagen) in lattices of the same collagen contracted by fibroblasts. However, rat tail tendon does not contain HHL cross-links, and collagen lattices made of rat tail tendon collagen are capable of contraction. This suggests that telopeptide sites, and not mature HHL cross-links per se, are essential for fibroblasts to contract collagen lattices. Beta-aminopropionitrile fumarate (BAPN), a potent lathyrogen that perturbs collagen cross-linking by inhibition of lysyl oxidase, also inhibited the rate of lattice cell contraction in lattices composed of native collagen. However, the concentrations of BAPN that were necessary to inhibit the contraction of collagen lattices also inhibited fibroblast growth suggestive of cellular toxicity. In accordance with other studies, we found no inhibition of the rate of lattice contraction when fibronectin-depleted serum was used. Electron microscopy of contracted gels revealed typical collagen fibers with a characteristic axial periodicity. The data

  10. Pyridinium cross-links in heritable disorders of collagen

    Energy Technology Data Exchange (ETDEWEB)

    Pasquali, M.; Still, M.J.; Dembure, P.P. [Emory Univ., Atlanta, GA (United States)] [and others

    1995-12-01

    Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited disorders of collagen that is characterized by skin fragility, skin hyperextensibility, and joint hypermobility. EDS type VI is caused by impaired collagen lysyl hydroxylase (procollagen-lysine, 2-oxoglutarate 5-dioxygenase; E.C.1.14.11.4), the ascorbate-dependent enzyme that hydroxylates lysyl residues on collagen neopeptides. Different alterations in the gene for collagen lysyl hydroxylase have been reported in families with EDS type VI. In EDS type VI, impairment of collagen lysyl hydroxylase results in a low hydroxylysine content in mature collagen. Hydroxylysine is a precursor of the stable, covalent, intermolecular cross-links of collagen, pyridinoline (Pyr), and deoxypyridinoline (Dpyr). Elsewhere we reported in preliminary form that patients with EDS type VI had a distinctive alteration in the urinary excretion of Pyr and Dpyr. In the present study, we confirm that the increased Dpyr/Pyr ratio is specific for EDS type VI and is not observed in other inherited or acquired collagen disorders. In addition, we find that skin from patients with EDS type VI has reduced Pyr and increased Dpyr, which could account for the organ pathology. 19 refs., 1 tab.

  11. Acute corneal hydrops during pregnancy with spontaneous resolution after corneal cross-linking for keratoconus: a case report.

    Science.gov (United States)

    Stock, Ricardo Alexandre; Thumé, Thaís; Bonamigo, Elcio Luiz

    2017-02-25

    Keratoconus may progress to acute corneal hydrops even after cross-linking. In some cases, keratoconus progresses during pregnancy. In this report, we present a case of a patient with increased anterior stromal resistance after cross-linking that would favor nonprogression of keratoconus during pregnancy. We report that cross-linking is likely to have had a protective effect in a white pregnant patient with acute corneal hydrops who showed rapid improvement, as documented by corneal topography. Improvement occurred within 8 days, whereas up to 250 days are reported in the literature. No keratoconus progression occurred in the 20-month follow-up period. Cross-linking failed to prevent the occurrence of acute corneal hydrops after rupture of Descemet's membrane but most likely helped to accelerate the resolution of the condition. Corneal hardening resulting from cross-linking may have also contributed to stabilizing keratoconus during pregnancy.

  12. Standard and hypoosmolar corneal cross-linking in various pachymetry groups

    NARCIS (Netherlands)

    Soeters, Nienke; Tahzib, Nayyirih G

    2015-01-01

    PURPOSE: To investigate the influence of corneal thickness on the outcome of corneal cross-linking (CXL) for progressive keratoconus. METHODS: In this cohort study, 72 unilateral eyes were treated by CXL and divided into three groups according to central corneal thickness (CCT) measured by ultrasoun

  13. Progression in keratoconus and the effect of corneal cross-linking on progression.

    Science.gov (United States)

    Brown, Sarah E; Simmasalam, Rubinee; Antonova, Nataliya; Gadaria, Neha; Asbell, Penny A

    2014-11-01

    Ultraviolet corneal collagen cross-linking (CXL) has been shown to possibly delay, halt, or even reverse disease progression in keratoconus. Understanding of keratoconic progression in untreated eyes, however, is still incomplete and is hampered by the varying definitions and metrics used to evaluate corneal changes. As a result, the CXL literature varies widely in criteria for progression and parameters for successful outcomes. To date, there have been few long-term, well-controlled clinical trials supporting the efficacy of CXL to prevent progression in keratoconus. Review of our data on keratoconus suggests the course of corneal change is difficult to predict and that many keratoconic eyes appear stable once the eyes begin to exhibit frank changes in corneal curvature typical of keratoconus. Better-defined metrics for progression in keratoconus are needed. Larger, long-term randomized clinical trials may more clearly establish the efficacy and safety of CXL in the management of keratoconus and determine which patients are the best candidates for this procedure.

  14. Subclinical inflammatory response after accelerated corneal cross-linking

    Institute of Scientific and Technical Information of China (English)

    Hassan Hashemi; Nahid Ashraf; Ebrahim Jafarzadehpur; Alireza Hedayatfar; Soheila Asgari

    2016-01-01

    Background: To evaluate the inlfammatory response after accelerated collagen cross-linking (CXL) in eyes with keratoconus. Methods: Consecutive eyes with keratoconus undergoing CXL surgery were included in this non-randomized interventional study. Aqueous lfare was measured pre- and post-operatively with a laser lfare photometer at 1 week, 1, 3 and 6 months after CXL. Results: Sixty eyes of 60 patients were entered into the study. Before CXL, the mean lfare value was 4.5 photons per millisecond (ph/ms). The lfare values observed at week 1 (7.1 ph/ms; P=0.008), month 1 (6.5 ph/ms; P=0.04), month 3 (6.7 ph/ms; P=0.004) and month 6 (6.7 ph/ms; P=0.004) were signiifcantly higher compared to baseline. Flare values were not signiifcantly different from week 1 up to 6 months after CXL (P=0.930). No statistically significant correlation was detected between the amount of inlfammation and keratometric indices. Conclusions: Accelerated CXL in patients with keratoconus may cause a subclinical inflammatory response which is evident as slight but rather long-lasting rise of aqueous lfare.

  15. Different Topographic Response Between Mild to Moderate and Advanced Keratoconus After Accelerated Collagen Cross-linking.

    Science.gov (United States)

    Chan, Tommy C Y; Chow, Vanissa W S; Jhanji, Vishal; Wong, Victoria W Y

    2015-08-01

    To evaluate the clinical and topographic effects after accelerated corneal collagen cross-linking (CXL) in keratoconus. This was a prospective interventional study in 25 eyes of 24 Asian patients with keratoconus, where 10 eyes in group 1 had mild to moderate keratoconus with the steepest keratometry reading (Kmax) keratoconus with Kmax ≥ 58.0 D. The patients underwent accelerated CXL with 18 W/cm UV-A light for 5 minutes. Clinical and topographic parameters were obtained before and 1 year after treatment. Overall, spectacle-corrected distance visual acuity, refraction, average keratometry readings, Kmax, anterior elevation at the apex, and corneal endothelial cell density remained stable (P keratoconus but not as effective in the less progressed counterparts.

  16. Methicillin-Resistant Staphylococcus aureus Ocular Infection after Corneal Cross-Linking for Keratoconus: Potential Association with Atopic Dermatitis.

    Science.gov (United States)

    Fasciani, Romina; Agresta, Antonio; Caristia, Alice; Mosca, Luigi; Scupola, Andrea; Caporossi, Aldo

    2015-01-01

    Purpose. To report the risk of methicillin-resistant Staphylococcus aureus (MRSA) ocular infection after UVA-riboflavin corneal collagen cross-linking in a patient with atopic dermatitis. Methods. A 22-year-old man, with bilateral evolutive keratoconus and atopic dermatitis, underwent UVA-riboflavin corneal cross-linking and presented with rapidly progressive corneal abscesses and cyclitis in the treated eye five days after surgery. The patient was admitted to the hospital and treated with broad-spectrum antimicrobic therapy. Results. The patient had positive cultures for MRSA, exhibiting a strong resistance to antibiotics. Antibiotic therapy was modified and targeted accordingly. The intravitreal reaction is extinguished, but severe damage of ocular structures was unavoidable. Conclusion. Riboflavin/UVA corneal cross-linking is considered a safe procedure and is extremely effective in halting keratoconus' progression. However, this procedure is not devoid of infectious complications, due to known risk factors and/or poor patients' hygiene compliance in the postoperative period. Atopic dermatitis is a common disease among patients with keratoconus and Staphylococcus aureus colonization is commonly found in patients with atopic dermatitis. Therefore, comorbidity with atopic dermatitis should be thoroughly assessed through clinical history before surgery. A clinical evaluation within three days after surgery and the imposition of strict personal hygiene rules are strongly recommended.

  17. Methicillin-Resistant Staphylococcus aureus Ocular Infection after Corneal Cross-Linking for Keratoconus: Potential Association with Atopic Dermatitis

    Directory of Open Access Journals (Sweden)

    Romina Fasciani

    2015-01-01

    Full Text Available Purpose. To report the risk of methicillin-resistant Staphylococcus aureus (MRSA ocular infection after UVA-riboflavin corneal collagen cross-linking in a patient with atopic dermatitis. Methods. A 22-year-old man, with bilateral evolutive keratoconus and atopic dermatitis, underwent UVA-riboflavin corneal cross-linking and presented with rapidly progressive corneal abscesses and cyclitis in the treated eye five days after surgery. The patient was admitted to the hospital and treated with broad-spectrum antimicrobic therapy. Results. The patient had positive cultures for MRSA, exhibiting a strong resistance to antibiotics. Antibiotic therapy was modified and targeted accordingly. The intravitreal reaction is extinguished, but severe damage of ocular structures was unavoidable. Conclusion. Riboflavin/UVA corneal cross-linking is considered a safe procedure and is extremely effective in halting keratoconus’ progression. However, this procedure is not devoid of infectious complications, due to known risk factors and/or poor patients’ hygiene compliance in the postoperative period. Atopic dermatitis is a common disease among patients with keratoconus and Staphylococcus aureus colonization is commonly found in patients with atopic dermatitis. Therefore, comorbidity with atopic dermatitis should be thoroughly assessed through clinical history before surgery. A clinical evaluation within three days after surgery and the imposition of strict personal hygiene rules are strongly recommended.

  18. Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Olde Damink, L.H.H.; Dijkstra, P.J.; Luyn, van M.J.A.; Wachem, van P.B.; Nieuwenhuis, P.; Feijen, J.

    1996-01-01

    A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links

  19. Novel Technique of Transepithelial Corneal Cross-Linking Using Iontophoresis in Progressive Keratoconus

    Science.gov (United States)

    Raffa, Paolo; Rosati, Marianna

    2016-01-01

    In this work, the authors presented the techniques and the preliminary results at 6 months of a randomized controlled trial (NCT02117999) comparing a novel transepithelial corneal cross-linking protocol using iontophoresis with the Dresden protocol for the treatment of progressive keratoconus. At 6 months, there was a significant average improvement with an average flattening of the maximum simulated keratometry reading of 0.72 ± 1.20 D (P = 0.01); in addition, corrected distance visual acuity improved significantly (P = 0.08) and spherical equivalent refraction was significantly less myopic (P = 0.02) 6 months after transepithelial corneal cross-linking with iontophoresis. The novel protocol using iontophoresis showed comparable results with standard corneal cross-linking to halt progression of keratoconus during 6-month follow-up. Investigation of the long-term RCT outcomes are ongoing to verify the efficacy of this transepithelial corneal cross-linking protocol and to determine if it may be comparable with standard corneal cross-linking in the management of progressive keratoconus. PMID:27597895

  20. Novel Technique of Transepithelial Corneal Cross-Linking Using Iontophoresis in Progressive Keratoconus

    Directory of Open Access Journals (Sweden)

    Marco Lombardo

    2016-01-01

    Full Text Available In this work, the authors presented the techniques and the preliminary results at 6 months of a randomized controlled trial (NCT02117999 comparing a novel transepithelial corneal cross-linking protocol using iontophoresis with the Dresden protocol for the treatment of progressive keratoconus. At 6 months, there was a significant average improvement with an average flattening of the maximum simulated keratometry reading of 0.72±1.20 D (P=0.01; in addition, corrected distance visual acuity improved significantly (P=0.08 and spherical equivalent refraction was significantly less myopic (P=0.02 6 months after transepithelial corneal cross-linking with iontophoresis. The novel protocol using iontophoresis showed comparable results with standard corneal cross-linking to halt progression of keratoconus during 6-month follow-up. Investigation of the long-term RCT outcomes are ongoing to verify the efficacy of this transepithelial corneal cross-linking protocol and to determine if it may be comparable with standard corneal cross-linking in the management of progressive keratoconus.

  1. Biodegradation of differently cross-linked collagen membranes: an experimental study in the rat.

    NARCIS (Netherlands)

    Rothamel, D.; Schwarz, F.; Sager, M.; Herten, M. van; Sculean, A.; Becker, J.M.

    2005-01-01

    The aim of the present study was to compare the biodegradation of differently cross-linked collagen membranes in rats. Five commercially available and three experimental membranes (VN) were included: (1) BioGide (BG) (non-cross-linked porcine type I and III collagens), (2) BioMend (BM), (3) BioMendE

  2. Intraoperative Corneal Thickness Changes during Pulsed Accelerated Corneal Cross-Linking Using Isotonic Riboflavin with HPMC

    Directory of Open Access Journals (Sweden)

    Ahmed M. Sherif

    2016-01-01

    Full Text Available Purpose. To evaluate corneal thickness changes during pulsed accelerated corneal cross-linking (CXL for keratoconus using a new isotonic riboflavin formula. Methods. In this prospective, interventional, clinical study patients with grades 1-2 keratoconus (Amsler-Krumeich classification underwent pulsed accelerated (30 mW/cm2 CXL after application of an isotonic riboflavin solution (0.1% with HPMC for 10 minutes. Central corneal thickness (CCT measurements were taken using ultrasound pachymetry before and after epithelial removal, after riboflavin soaking, and immediately after completion of UVA treatment. Results. Twenty eyes of 11 patients (4 males, 7 females were enrolled. Mean patient age was 26±3 (range from 18 to 30 years. No intraoperative or postoperative complications were observed in any of the patients. Mean CCT was 507±35 μm (range: 559–459 μm before and 475±40 μm (range: 535–420 μm after epithelial removal (P<0.001. After 10 minutes of riboflavin instillation, there was a statistically significant decrease of CCT by 6.2% from 475±40 μm (range: 535–420 μm to 446±31 μm (range: 508–400 (P<0.005. There was no other statistically significant change of CCT during UVA irradiation. Conclusions. A significant decrease of corneal thickness was demonstrated during the isotonic riboflavin with HPMC application while there was no significant change during the pulsed accelerated UVA irradiation.

  3. The Effect of Cross-Linking Treatment on Conus Curvature and Higher Order Corneal Aberrations in Keratoconus

    Directory of Open Access Journals (Sweden)

    Sücattin İlker Kocamış

    2014-05-01

    Full Text Available Objectives: To study the effect of corneal collagen cross-linking on conus curvature and corneal aberrations in keratoconus. Materials and Methods: The medical records of thirty-seven eyes of 32 progressive keratoconus patients (17 male, 15 female, mean age: 22.13±4.64 years who had undergone corneal cross-linking were evaluated retrospectively. The change in refractive errors, visual acuity on Snellen charts, average keratometry, conus curvature, and corneal aberrations calculated at 6.00 mm pupil size throughout the follow-up time were compared with paired t-test. The correlation of the change in best-corrected visual acuity and in uncorrected visual acuity with the change of the parameters which had statistically significant difference at 18 months was studied with Pearson’s correlation analysis. Results: The best-corrected visual acuity, uncorrected visual acuity, spherical and cylindrical error, average keratometry, conus curvature, vertical coma, total corneal aberrations, total higher order aberrations had statistically significant difference at 18 postoperative months (p=0.001. Spherical aberration (p=0.95 and horizontal coma (p=0.78 did not show statistically significant difference at the end of follow-up. The change in uncorrected visual acuity correlated with change in conus curvature (r=-0.420, p=0.01 and change in cylindrical refraction (r=0.453, p=0.005 at 18 months. The change in best-corrected visual acuity correlated with change in total corneal aberrations (r=-0.490, p=0.002, vertical coma (r=0.408, p=0.01, average keratometry (r=-0.386, p=0.02, conus curvature (r=-0.381, p=0.02, and total higher order aberrations (r=-0.326, p=0.05 at 18 months. Conclusion: Corneal collagen cross-linking treatment applied to progressive keratoconus cases induces significant decrease in conus curvature, in total corneal aberrations, and in higher order aberrations, especially in vertical coma, and leads to a prominent visual acuity increase

  4. Novel myopic refractive correction with transepithelial very high-fluence collagen cross-linking applied in a customized pattern: early clinical results of a feasibility study

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2014-04-01

    Full Text Available Anastasios John Kanellopoulos LaserVision.gr Institute, Athens, Greece, and New York Medical School, New York, NY, USA Background: The purpose of this study is to report the safety and efficacy of a new application of collagen cross-linking using a novel device to achieve predictable refractive myopic changes in virgin corneas. Methods: Four cases were treated with a novel device employing very high-fluence collagen cross-linking applied in a myopic pattern. Prior to treatment, riboflavin solution was applied to the intact epithelium. The collagen cross-linking device was then engaged for a total of 12 J/cm2, to be applied transepithelially in a predetermined pattern. Cornea clarity, corneal keratometry, and corneal topography were evaluated by both Placido disc and Scheimpflug imaging, along with cornea anterior segment optical coherence tomography and endothelial cell counts. Results: An average of 2.3 diopters was achieved in the first week in all four cases treated with the very high-fluence myopic collagen cross-linking intervention. There was a slight regression to 1.44 diopters at 1 month, which remained stable at 6-month follow-up. The mean keratometry change was from 44.90 diopters to 43.46 diopters. There was no significant change in endothelial cell counts or corneal clarity. There was some mild change in epithelial thickness distribution, with the treated area showing a slight but homogeneous reduction in mean thickness from 52 µm to 44 µm. Conclusion: This report describes the novel application of very high-fluence collagen cross-linking with a predictable well defined myopic refractive (flattening corneal effect. This technique has the advantages of essentially no postoperative morbidity, immediate visual rehabilitation, and the potential for tapering until the desired result is achieved. Keywords: myopia, refractive correction, high-fluence collagen cross-linking, clinical results

  5. Nationwide reduction in the number of corneal transplantations for keratoconus following the implementation of cross-linking

    NARCIS (Netherlands)

    Godefrooij, Daniel A; Gans, Renze; Imhof, Saskia M; Wisse, Robert P L

    2016-01-01

    PURPOSE: Keratoconus is characterized by corneal ectasia and irregular astigmatism, which can lead to diminished vision and corneal scarring. Approximately 10-20% of patients with keratoconus eventually require a corneal transplant. Corneal cross-linking (CXL) is a relatively new treatment that may

  6. T3 affects expression of collagen I and collagen cross-linking in bone cell cultures

    OpenAIRE

    Varga, F.; Rumpler, M.; Zoehrer, R.; Turecek, C.; Spitzer, S.; Thaler, R; Paschalis, E.P.; Klaushofer, K.

    2010-01-01

    Thyroid hormones (T3, T4) have a broad range of effects on bone, however, its role in determining the quality of bone matrix is poorly understood. In-vitro, the immortalized mouse osteoblast-like cell line MC3T3-E1 forms a tissue like structure, consisting of several cell layers, whose formation is affected by T3 significantly. In this culture system, we investigated the effects of T3 on cell multiplication, collagen synthesis, expression of genes related to the collagen cross-linking process...

  7. Glucose-mediated cross-linking of collagen in rat tendon and skin

    NARCIS (Netherlands)

    Mentink, CJAL; Hendriks, M; Levels, AAG; Wolffenbuttel, BHR

    2002-01-01

    Back-ground: Cross-linking of macromolecules like collagen plays an important role in the development of complications in diabetes and ageing. One of the underlying mechanisms of this cross-linking is the formation of advanced glycation endproducts (AGEs). Methods: In this study, we assessed the use

  8. Infrared microspectroscopic determination of collagen cross-links in articular cartilage

    Science.gov (United States)

    Rieppo, Lassi; Kokkonen, Harri T.; Kulmala, Katariina A. M.; Kovanen, Vuokko; Lammi, Mikko J.; Töyräs, Juha; Saarakkala, Simo

    2017-03-01

    Collagen forms an organized network in articular cartilage to give tensile stiffness to the tissue. Due to its long half-life, collagen is susceptible to cross-links caused by advanced glycation end-products. The current standard method for determination of cross-link concentrations in tissues is the destructive high-performance liquid chromatography (HPLC). The aim of this study was to analyze the cross-link concentrations nondestructively from standard unstained histological articular cartilage sections by using Fourier transform infrared (FTIR) microspectroscopy. Half of the bovine articular cartilage samples (n=27) were treated with threose to increase the collagen cross-linking while the other half (n=27) served as a control group. Partial least squares (PLS) regression with variable selection algorithms was used to predict the cross-link concentrations from the measured average FTIR spectra of the samples, and HPLC was used as the reference method for cross-link concentrations. The correlation coefficients between the PLS regression models and the biochemical reference values were r=0.84 (p<0.001), r=0.87 (p<0.001) and r=0.92 (p<0.001) for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), and pentosidine (Pent) cross-links, respectively. The study demonstrated that FTIR microspectroscopy is a feasible method for investigating cross-link concentrations in articular cartilage.

  9. The process of EDC-NHS cross-linking of reconstituted collagen fibres increases collagen fibrillar order and alignment

    Directory of Open Access Journals (Sweden)

    D. V. Shepherd

    2015-01-01

    Full Text Available We describe the production of collagen fibre bundles through a multi-strand, semi-continuous extrusion process. Cross-linking using an EDC (1-ethyl-3-(3-dimethylaminopropylcarbodiimide, NHS (N-hydroxysuccinimide combination was considered. Atomic Force Microscopy and Raman spectroscopy focused on how cross-linking affected the collagen fibrillar structure. In the cross-linked fibres, a clear fibrillar structure comparable to native collagen was observed which was not observed in the non-cross-linked fibre. The amide III doublet in the Raman spectra provided additional evidence of alignment in the cross-linked fibres. Raman spectroscopy also indicated no residual polyethylene glycol (from the fibre forming buffer or water in any of the fibres.

  10. The process of EDC-NHS cross-linking of reconstituted collagen fibres increases collagen fibrillar order and alignment

    Science.gov (United States)

    Shepherd, D. V.; Shepherd, J. H.; Ghose, S.; Kew, S. J.; Cameron, R. E.; Best, S. M.

    2015-01-01

    We describe the production of collagen fibre bundles through a multi-strand, semi-continuous extrusion process. Cross-linking using an EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide), NHS (N-hydroxysuccinimide) combination was considered. Atomic Force Microscopy and Raman spectroscopy focused on how cross-linking affected the collagen fibrillar structure. In the cross-linked fibres, a clear fibrillar structure comparable to native collagen was observed which was not observed in the non-cross-linked fibre. The amide III doublet in the Raman spectra provided additional evidence of alignment in the cross-linked fibres. Raman spectroscopy also indicated no residual polyethylene glycol (from the fibre forming buffer) or water in any of the fibres.

  11. Changes in corneal sensitivity following cross-linking for progressive early-stage keratoconus

    Directory of Open Access Journals (Sweden)

    Anelise de Medeiros Lago

    2014-04-01

    Full Text Available Purpose: To evaluate changes in corneal sensitivity following corneal cross-linking (CXL in patients with progressive earlier stage keratoconus. Methods: Thirty-eight eyes of 19 patients (11 women, 8 men were included in a prospective, nonrandomized clinical study. The mean patient age was 22 years (range, 18-26 years. Inclusion criteria were early stage bilateral progressive keratoconus, a transparent cornea, and a thickness of ≥440 µm in the thinnest area of the cornea. Using the Cochet-Bonnet esthesiometer, central corneal sensitivity was measured before surgery, 7 days after surgery, and once a month thereafter until recovery of baseline preoperative levels. Central corneal sensitivity >40 mm was considered normal. Results: Corneal sensitivity gradually returned to preoperative levels in all treated eyes. The mean central corneal sensitivity was 52.2, 24.0, 38.2, 42.5, 50.0, and 52.5 mm before surgery, 7 days after surgery, and at 1, 2, 3, and 4 months after surgery, respectively. Normal levels of corneal sensation, but not baseline (preoperative levels, were observed 2 months after surgery. The preoperative levels were observed 3 months after surgery. Conclusions: Our results suggest that central corneal sensitivity can be decreased for as long as 3 months after CXL for progressive earlier stage keratoconus.

  12. Biodegradation of differently cross-linked collagen membranes: an experimental study in the rat.

    Science.gov (United States)

    Rothamel, Daniel; Schwarz, Frank; Sager, Martin; Herten, Monika; Sculean, Anton; Becker, Jürgen

    2005-06-01

    The aim of the present study was to compare the biodegradation of differently cross-linked collagen membranes in rats. Five commercially available and three experimental membranes (VN) were included: (1) BioGide (BG) (non-cross-linked porcine type I and III collagens), (2) BioMend (BM), (3) BioMendExtend (BME) (glutaraldehyde cross-linked bovine type I collagen), (4) Ossix (OS) (enzymatic-cross-linked bovine type I collagen), (5) TutoDent (TD) (non-cross-linked bovine type I collagen, and (6-8) VN(1-3) (chemical cross-linked porcine type I and III collagens). Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 40 wistar rats, which were divided into five groups (2, 4, 8, 16, and 24 weeks), including eight animals each. After 2, 4, 8, 16, and 24 weeks of healing, the rats were sacrificed and explanted specimens were prepared for histologic and histometric analysis. The following parameters were evaluated: biodegradation over time, vascularization, tissue integration, and foreign body reaction. Highest vascularization and tissue integration was noted for BG followed by BM, BME, and VN(1); TD, VN(2), and VN(3) showed prolongated, while OS exhibited no vascularization. Subsequently, biodegradation of BG, BM, BME and VN(1) was faster than TD, VN(2), and VN(3). OS showed only a minute amount of superficial biodegradation 24 weeks following implantation. Biodegradation of TD, BM, BME, VN(2), and VN(3) was associated with the presence of inflammatory cells. Within the limits of the present study, it was concluded that cross-linking of bovine and porcine-derived collagen types I and III was associated with (i) prolonged biodegradation, (ii) decreased tissue integration and vascularization, and (iii) in case of TD, BM, BME, VN(2), and VN(3) foreign body reactions.

  13. Mechanical and biocompatible characterization of a cross-linked collagen-hyaluronic acid wound dressing.

    Science.gov (United States)

    Kirk, James F; Ritter, Gregg; Finger, Isaac; Sankar, Dhyana; Reddy, Joseph D; Talton, James D; Nataraj, Chandra; Narisawa, Sonoko; Millán, José Luis; Cobb, Ronald R

    2013-01-01

    Collagen scaffolds have been widely employed as a dermal equivalent to induce fibroblast infiltrations and dermal regeneration in the treatment of chronic wounds and diabetic foot ulcers. Cross-linking methods have been developed to address the disadvantages of the rapid degradation associated with collagen-based scaffolds. To eliminate the potential drawbacks associated with glutaraldehyde cross-linking, methods using a water soluble carbodiimide have been developed. In the present study, the glycosaminoglycan (GAG) hyaluronic acid (HA), was covalently attached to an equine tendon derived collagen scaffold using 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) to create ntSPONGE The HA was shown to be homogeneously distributed throughout the collagen matrix. In vitro analyses of the scaffold indicated that the cross-linking enhanced the biological stability by decreasing the enzymatic degradation and increasing the thermal denaturation temperature. The material was shown to support the attachment and proliferation of mouse L929 fibroblast cells. In addition, the cross-linking decreased the resorption rate of the collagen as measured in an intramuscular implant model in rabbits. The material was also shown to be biocompatible in a variety of in vitro and in vivo assays. These results indicate that this cross-linked collagen-HA scaffold, ntSPONGE has the potential for use in chronic wound healing.

  14. Mature enzymatic collagen cross-links, hydroxylysylpyridinoline and lysylpyridinoline, in the aging human vitreous

    NARCIS (Netherlands)

    Ponsioen, T.L.; van Deemter, M.; Bank, R.A.; Snabel, J.M.; Zijlstra, G.S.; van der Worp, R.J.; Hooymans, J.M.M.; Los, L.I.

    2009-01-01

    Purpose. The vitreous body of the human eye undergoes progressive morphologic changes with aging. Since the enzymatic collagen cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are known to be important for the integrity of the collagen matrix, the presence in the vitreous on agin

  15. Mature Enzymatic Collagen Cross-Links, Hydroxylysylpyridinoline and Lysylpyridinoline, in the Aging Human Vitreous

    NARCIS (Netherlands)

    Ponsioen, Theodorus L.; van Deemter, Marielle; Bank, Rudolf A.; Snabel, Johanna M.; Zijlstra, Gerrit S.; van der Worp, Roelofje J.; Hooymans, Johanna M. M.; Los, Leonoor I.

    2009-01-01

    PURPOSE. The vitreous body of the human eye undergoes progressive morphologic changes with aging. Since the enzymatic collagen cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are known to be important for the integrity of the collagen matrix, the presence in the vitreous on agin

  16. Influence of corneal collagen crosslinking with riboflavin and ultraviolet-a irradiation on excimer laser surgery.

    NARCIS (Netherlands)

    Kampik, D.; Ralla, B.; Keller, S.; Hirschberg, M.; Friedl, P.H.A.; Geerling, G.

    2010-01-01

    PURPOSE: Riboflavin/ultraviolet A (UVA) cross-linking (CXL) of corneal collagen is a novel method of stabilizing corneal mechanical properties and preventing progression of keratectasias. This study was conducted to investigate whether CXL influences ablation rate, flap thickness, and refractive res

  17. Influence of corneal collagen crosslinking with riboflavin and ultraviolet-a irradiation on excimer laser surgery.

    NARCIS (Netherlands)

    Kampik, D.; Ralla, B.; Keller, S.; Hirschberg, M.; Friedl, P.H.A.; Geerling, G.

    2010-01-01

    PURPOSE: Riboflavin/ultraviolet A (UVA) cross-linking (CXL) of corneal collagen is a novel method of stabilizing corneal mechanical properties and preventing progression of keratectasias. This study was conducted to investigate whether CXL influences ablation rate, flap thickness, and refractive res

  18. Cornea Collagen Cross-linking for Keratoconus: A Comparison between Accelerated and Conventional Methods

    Science.gov (United States)

    Razmjoo, Hasan; Peyman, Alireza; Rahimi, Ali; Modrek, Hoda Jafari

    2017-01-01

    Background: Keratoconus is a progressive degenerative disorder of the cornea in which structural changes in the cornea cause it to become thin and conical in shape. Recently, collagen cross-linking (CXL) has been introduced as an effective intervention in management of progressive keratoconus. Accelerated CXL is a new protocol of this procedure which reduces corneal ultraviolet irradiation exposure time to 5 min. This study aimed to compare visual acuity, keratometry and topographic criteria of keratoconic eyes after conventional and accelerated CXL with a six-month follow-up. Materials and Methods: In this prospective interventional study we assessed eyes of 40 patients. Patients were divided into two groups randomly. One group underwent accelerated (5 min) CXL and the other underwent conventional (30 min) CXL. Visual acuity, topographic criteria and keratometry were assessed preoperatively and 6 months postoperatively. Results: In the present study we assessed 40 patients, 50% of which were right eye (OD) and 50% were left eye (OS). Mean age of patients in the accelerated group was 22.10 and in the conventional group was 22.80 years. Our results showed no significant differences between visual acuity, keratometric and topographic criteria in the two groups before intervention. Likewise our results manifested no significant difference between visual acuity, keratometric, refractive and topographic criteria after intervention. Conclusion: According to our survey topographic criteria and keratometry improvement in the accelerated and conventional protocol are the same. So accelerated protocol is suggested as a safe and effective option for management of progressive keratoconus. PMID:28299302

  19. Riboflavin cross-linking of collagen porous scaffolds for periodontal regeneration

    Directory of Open Access Journals (Sweden)

    Seciu A-M.

    2016-05-01

    Full Text Available Periodontitis treatment using occlusive membranes presented variable efficacy due to their rapid degradation in the complex biologic environment of the damaged periodontium. The aim of this study was to prepare novel composites based on collagen, chondroitin sulfate and fibronectin, and to establish the optimal parameters for their photochemical cross-linking using riboflavin and UV exposure. The degree of cross-linking, biodegradability and density of all scaffold variants were investigated. Their cytotoxicity was evaluated in a culture of gingival fibroblasts by MTT assay and light microscopy. The results indicated that the higher the cross-linking degree, the lower was the scaffold biodegradation. Cell culture studies showed that composite scaffolds were favorable for cellular survival. In conclusion, the cross-linking method using riboflavin and UV exposure resulted in stable and biocompatible collagen-based composite scaffolds that could be used for periodontitis treatment.

  20. A Review of Collagen Cross-Linking in Cornea and Sclera

    Directory of Open Access Journals (Sweden)

    Xiao Zhang

    2015-01-01

    Full Text Available Riboflavin/UVA cross-linking is a technique introduced in the past decades for the treatment of keratoconus, keratectasia, and infectious keratitis. Its efficacy and safety have been investigated with clinical and laboratory studies since its first clinical application by Wollensak for the treatment of keratoconus. Although its complications are encountered during clinical practice, such as infection inducing risk, minimal invasion merits a further investigation on its future application in clinical practice. Recently, collagen cross-linking in sclera shows a promising prospect. In present study, we summarized the representative studies describing the clinical and laboratory application of collagen cross-linking published in past decades and provided our opinion on the positive and negative results of cross-linking in the treatment of ophthalmic disorders.

  1. MICROWAVE IRRADIATION AND CROSS-LINKING OF COLLAGEN

    NARCIS (Netherlands)

    VISSER, CE; VOUTE, ABE; OOSTING, J; BOON, ME; KOK, LP

    1992-01-01

    In a multifactorial experiment, dermal sheep collagen was treated in diluted glutaraldehyde solutions, 70% ethyl alcohol, Cialit 1:5000, and distilled water for 1, 3 and 5 min, respectively, in combination with microwave irradiation at different temperature settings. The shrinkage temperature indica

  2. CROSS-LINKING OF DERMAL SHEEP COLLAGEN USING HEXAMETHYLENE DIISOCYANATE

    NARCIS (Netherlands)

    DAMINK, LHHO; DIJKSTRA, PJ; VANLUYN, MJA; VANWACHEM, PB; NIEUWENHUIS, P; FEIJEN, J

    1995-01-01

    The use of hexamethylene diisocyanate (HMDIC) as a crosslinking agent for dermal sheep collagen (DSC) was studied. Because HMDIC is on ly slightly water soluble, a surfactant was used to obtain a clear and micellar crosslinking solution and to promote the penetration of HMDIC in the DSC matrix. Usin

  3. Cross-linking of collagen-based materials

    NARCIS (Netherlands)

    Zeeman, R.

    1998-01-01

    An example of a collagen-based tissue is the aortic heart valve. A variety of pathological processes can lead to heart valve malfunction and this is usually associated with degenerative changes of the tissue. The most commonly used types of prosthetic valves are mechanical and tissue valves. One

  4. Cross-linking of collagen-based materials

    NARCIS (Netherlands)

    Zeeman, Raymond

    1998-01-01

    An example of a collagen-based tissue is the aortic heart valve. A variety of pathological processes can lead to heart valve malfunction and this is usually associated with degenerative changes of the tissue. The most commonly used types of prosthetic valves are mechanical and tissue valves. One maj

  5. Analysis of the effective dose of ultraviolet light in corneal cross-linking.

    Science.gov (United States)

    Zhang, Yong; Wang, Kuan-Chen; Chang, Chao-Kai; Lin, Jui-Teng

    2016-01-01

    To analyze the efficacy of ultraviolet (UV) light initiating corneal cross-linking (CXL). The time-dependent absorption of UV light due to the depletion of the initiator (riboflavin) was calculated. The effective dose of CXL with corneal surface covered by a thin layer of riboflavin was derived analytically. The cross linking time was calculated by the depletion level of the riboflavin concentration. A comprehensive method was used to derive analytic formulas. The effective dose of CXL was reduced by a factor (R) which was proportional to the thickness (d) and concentrations (C0) of the riboflavin surface layer. Our calculations showed that the conventional dose of 5.4 J/cm(2) had a reduced effective dose of 4.3 and 3.45 J/cm(2), for d was 100 and 200 µm, respectively, and C0=0.1%. The surface cross linking time was calculated to be T*=10.75s, for a depletion level of 0.135 and UV initial intensity of 30 mW/cm(2). The volume T* was exponentially increasing and proportional to exp (bdC0), with b being the steady state absorption coefficient. The effective dose of CXL is reduced by a factor proportional to the thickness and concentrations of the riboflavin surface layer. The wasted dose should be avoided by washing out the extra riboflavin surface layer prior to the UV light exposure.

  6. Corneal Cross-Linking in a 4-Year-Old Child With Keratoconus and Down Syndrome.

    Science.gov (United States)

    Sabti, Saad; Tappeiner, Christoph; Frueh, Beatrice E

    2015-09-01

    To describe the clinical outcome of corneal cross-linking (CXL) in a young child with keratoconus. This is a case report of a young girl with keratoconus with ophthalmologic findings and 3-year follow-up. Follow-up visits included visual acuity measurement, retinoscopy, corneal tomography, and topography. A girl with Down syndrome was diagnosed with bilateral keratoconus and relative amblyopia at the age of 4 years. The best-corrected near visual acuity was 20/100 binocularly. Corneal tomography showed the following parameters: OD K(max) 47.2 diopters (D), thinnest location 442 μm; OS K(max) 49.6 D, thinnest location 432 μm. Three months later, the keratoconus in the left eye progressed (K(max) 50.2 D, thinnest location 424 μm), and CXL was performed. One year later, CXL was necessary also in the right eye because of progression. The girl was most recently reexamined at the age of 7 years. The corrected near visual acuity was 20/80 in both eyes. The corneal curvature slightly flattened, and the corneal thickness stabilized (OD K(max) 46.8 D, thinnest location 389 μm; OS K(max) 49.4 D, thinnest location 360 μm). Onset of keratoconus can occur in early childhood, especially in patients with Down syndrome. In this case, CXL was performed at 4 and 5 years of age without complications and stopped further keratoconus progression.

  7. Exogenous collagen cross-linking recovers tendon functional integrity in an experimental model of partial tear.

    Science.gov (United States)

    Fessel, Gion; Wernli, Jeremy; Li, Yufei; Gerber, Christian; Snedeker, Jess G

    2012-06-01

    We investigated the hypothesis that exogenous collagen cross-linking can augment intact regions of tendon to mitigate mechanical propagation of partial tears. We first screened the low toxicity collagen cross-linkers genipin, methylglyoxal and ultra-violet (UV) light for their ability to augment tendon stiffness and failure load in rat tail tendon fascicles (RTTF). We then investigated cross-linking effects in load bearing equine superficial digital flexor tendons (SDFT). Data indicated that all three cross-linking agents augmented RTTF mechanical properties but reduced native viscoelasticity. In contrast to effects observed in fascicles, methylglyoxal treatment of SDFT detrimentally affected tendon mechanical integrity, and in the case of UV did not alter tendon mechanics. As in the RTTF experiments, genipin cross-linking of SDFT resulted in increased stiffness, higher failure loads and reduced viscoelasticity. Based on this result we assessed the efficacy of genipin in arresting tendon tear propagation in cyclic loading to failure. Genipin cross-linking secondary to a mid-substance biopsy-punch significantly reduced tissue strains, increased elastic modulus and increased resistance to fatigue failure. We conclude that genipin cross-linking of injured tendons holds potential for arresting tendon tear progression, and that implications of the treatment on matrix remodeling in living tendons should now be investigated.

  8. Mechanical properties and collagen cross-linking of the patellar tendon in old and young men

    DEFF Research Database (Denmark)

    Couppé, C; Hansen, P; Kongsgaard, M

    2009-01-01

    Age-related loss in muscle mass and strength impairs daily life function in the elderly. However, it remains unknown whether tendon properties also deteriorate with age. Cross-linking of collagen molecules provides structural integrity to the tendon fibrils and has been shown to change with age...... in animals but has never been examined in humans in vivo. In this study, we examined the mechanical properties and pyridinoline and pentosidine cross-link and collagen concentrations of the patellar tendon in vivo in old (OM) and young men (YM). Seven OM (67 +/- 3 years, 86 +/- 10 kg) and 10 YM (27 +/- 2...... contractions. Percutaneous tendon biopsies were taken and analyzed for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), pentosidine, and collagen concentrations. We found no significant differences in the dimensions or mechanical properties of the tendon between OM and YM. Collagen concentrations were...

  9. [Use of native and cross-linked collagen membranes for guided tissue and bone regeneration].

    Science.gov (United States)

    Schwarz, Frank; Sager, Martin; Rothamel, Daniel; Herten, Monika; Sculean, Anton; Becker, Jürgen

    2006-01-01

    A material which is used as a barrier for GBR/GTR procedures has to satisfy several physicochemical characteristics such as biocompatibility, tissue integration, barrier function, and dimensional stability. Recently, many investigations reported on the use of products derived from type I and type III porcine or bovine collagen. Collagen membranes are predominantly resorbed by enzymatic activity (protease and collagenase). To decrease resorption, various physical and chemical cross-linking techniques have been used. Although nowadays cross-linking of collagen seems to be a commonly used procedure, its impact on physicochemical properties of the membrane is still unknown. The aim of the present literature review is to evaluate the potential use of different collagen membranes for GBR/GTR procedures.

  10. Corneal Laceration

    Medline Plus

    Full Text Available ... your vision. Privacy Policy Related People with Advanced Keratoconus May Have A Future Alternative to Full Corneal ... 2016 Corneal Collagen Cross-linking Approved to Treat Keratoconus in U.S. Aug 01, 2016 Firework Blinds Teenager, ...

  11. Evaluation of epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes and concerns on osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Chenyu; Deng, Jia [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Xiang, Lin; Wu, Yingying [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Department of Oral Implantology, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Wei, Xiawei [State Key Laboratory of Biotherapy and Laboratory for Aging Research, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, Sichuan 610041 (China); Qu, Yili [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Department of Oral Implantology, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Man, Yi, E-mail: manyi780203@126.com [State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China); Department of Oral Implantology, West China Hospital of Stomatology, Sichuan University, Chengdu 610041 (China)

    2016-10-01

    Collagen membranes have ideal biological and mechanical properties for supporting infiltration and proliferation of osteoblasts and play a vital role in guided bone regeneration (GBR). However, pure collagen can lead to inflammation, resulting in progressive bone resorption. Therefore, a method for regulating the level of inflammatory cytokines at surgical sites is paramount for the healing process. Epigallocatechin-3-gallate (EGCG) is a component extracted from green tea with numerous biological activities including an anti-inflammatory effect. Herein, we present a novel cross-linked collagen membrane containing different concentrations of EGCG (0.0064%, 0.064%, and 0.64%) to regulate the level of inflammatory factors secreted by pre-osteoblast cells; improve cell proliferation; and increase the tensile strength, wettability, and thermal stability of collagen membranes. Scanning electron microscope images show that the surfaces of collagen membranes became smoother and the collagen fiber diameters became larger with EGCG treatment. Measurement of the water contact angle demonstrated that introducing EGCG improved membrane wettability. Fourier transform infrared spectroscopy analyses indicated that the backbone of collagen was intact, and the thermal stability was significant improved in differential scanning calorimetry. The mechanical properties of 0.064% and 0.64% EGCG-treated collagen membranes were 1.5-fold greater than those of the control. The extent of cross-linking was significantly increased, as determined by a 2,4,6-trinitrobenzenesulfonic acid solution assay. The Cell Counting Kit-8 (CCK-8) and live/dead assays revealed that collagen membrane cross-linked by 0.0064% EGCG induced greater cell proliferation than pure collagen membranes. Additionally, real-time polymerase chain reaction and enzyme-linked immunosorbent assay results showed that EGCG significantly affected the production of inflammatory factors secreted by MC3T3-E1 cells. Taken together, our

  12. Elevated carboxy terminal cross linked telopeptide of type I collagen in alcoholic cirrhosis

    DEFF Research Database (Denmark)

    Møller, S; Hansen, M; Hillingsø, Jens

    1999-01-01

    BACKGROUND: The carboxy terminal cross linked telopeptide of type I collagen (ICTP) has been put forward as a marker of bone resorption. Patients with alcoholic liver disease may have osteodystrophy. AIMS: To assess circulating and regional concentrations of ICTP in relation to liver dysfunction...

  13. Nationwide reduction in the number of corneal transplantations for keratoconus following the implementation of cross-linking.

    Science.gov (United States)

    Godefrooij, Daniel A; Gans, Renze; Imhof, Saskia M; Wisse, Robert P L

    2016-11-01

    Keratoconus is characterized by corneal ectasia and irregular astigmatism, which can lead to diminished vision and corneal scarring. Approximately 10-20% of patients with keratoconus eventually require a corneal transplant. Corneal cross-linking (CXL) is a relatively new treatment that may help prevent the need for corneal transplantation. Here, we investigated whether the introduction of CXL has reduced the number of corneal transplants performed annually. Data regarding the transplantation procedures performed in patients under the age of 50 years were extracted from the Dutch National Organ Transplant Registry. The number of corneal transplants performed prior to (i.e. in 2005 through 2007) and following the introduction of CXL (i.e. in 2012 through 2014) were compared. Furthermore, a trend analysis on annual keratoplasties over time was performed. Approximately 25% fewer corneal transplants were performed in the 3-year period following the introduction of CXL compared to the 3-year period prior to the introduction of CXL (201 versus 269 transplants, respectively; p = 0.005). Age, gender and visual acuity were similar between the patient groups in the two time periods. Trend analysis also demonstrated a significant decrease in the amount of corneal transplants (p = 0.001). Significantly fewer corneal transplants were performed for treating keratoconus following the nationwide introduction of CXL. This reduction suggests that corneal cross-linking can significantly reduce the need for corneal transplantation. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  14. Studies on Cross-linking of succinic acid with chitosan/collagen

    Directory of Open Access Journals (Sweden)

    Tapas Mitra

    2013-01-01

    Full Text Available The present study summarizes the cross-linking property of succinic acid with chitosan /collagen. In detail, the chemistry behind the cross-linking and the improvement in mechanical and thermal properties of the cross-linked material were discussed with suitable instruments and bioinformatics tools. The concentration of succinic acid with reference to the chosen polymers was optimized. A 3D scaffold prepared using an optimized concentration of succinic acid (0.2% (w/v with chitosan (1.0% (w/v and similarly with collagen (0.5% (w/v, was subjected to surface morphology, FT-IR analysis, tensile strength assessment, thermal stability and biocompatibility. Results revealed, cross-linking with succinic acid impart appreciable mechanical strength to the scaffold material. In silico analysis suggested the prevalence of non-covalent interactions, which played a crucial role in improving the mechanical and thermal properties of the cross-linked scaffold. The resultant 3D scaffold may find application as wound dressing material, as an implant in clinical applications and as a tissue engineering material.

  15. Physical Aspects of Photodynamic Corneal Collagen Crosslinking

    Science.gov (United States)

    Kornfield, Julia

    2012-02-01

    Healthy vision depends on the stability of the shape of the cornea, which provides most of the lens power of the optical system of the eye. Diseases in which the cornea progressively undergoes irregular deformation over time (e.g., keratoconus) can be treated clinically by inducing additional protein-protein crosslinks using a photosensitizing drug and a tailored dose of light. Unfortunately, the treatment moving through clinical trials is toxic to cells in and on the cornea. A path to a safer treatment is offered by the nanostructure of the corneal stroma---reminiscent of a HEX phase in block copolymers with 30nm diameter collagen cylinders spaced 60nm center-to-center in a hydrogel matrix of proteoglycans and water. We show that using a photosensitizing drug that sequesters itself in the collagen fibrils can minimize the toxicity of therapeutic protein-protein cross-linking. Photorheology and transport measurements are used to quantify the parameters of a simple physical model that is useful for optimizing clinical protocols.

  16. Is dialdehyde starch a valuable cross-linking agent for collagen/elastin based materials?

    Science.gov (United States)

    Skopinska-Wisniewska, J; Wegrzynowska-Drzymalska, K; Bajek, A; Maj, M; Sionkowska, A

    2016-04-01

    Collagen and elastin are the main structural proteins in mammal bodies. They provide mechanical support, strength, and elasticity to various organs and tissues, e.g. skin, tendons, arteries, and bones. They are readily available, biodegradable, biocompatible and they stimulate cell growth. The physicochemical properties of collagen and elastin-based materials can be modified by cross-linking. Glutaraldehyde is one of the most efficient cross-linking agents. However, the unreacted molecules can be released from the material and cause cytotoxic reactions. Thus, the aim of our work was to investigate the influence of a safer, macromolecular cross-linking agent--dialdehyde starch (DAS). The properties of hydrogels based on collagen/elastin mixtures (95/5, 90/10) containing 5 and 10% of DAS and neutralized via dialysis against deionized water were tested. The homogenous, transparent, stiff hydrogels were obtained. The DAS addition causes the formation of intermolecular cross-linking bonds but does not affect the secondary structure of the proteins. As a result, the thermal stability, mechanical strength, and, surprisingly, swelling ability increased. At the same time, the surface properties test and in vitro study show that the materials are attractive for 3T3 cells. Moreover, the materials containing 10% of DAS are more resistant to enzymatic degradation.

  17. Histological response to injected gluteraldehyde cross-linked bovine collagen based implant in a rat model

    Directory of Open Access Journals (Sweden)

    Cağlar Melda

    2006-02-01

    Full Text Available Abstract Background The aim of present study is to investigate the short and long term histopathological alterations caused by submucosal injection of gluteraldehyde cross-linked bovine collagen based on an experimental rat model. Methods Sixty Sprague-Dawley rats were assigned into two groups as group I and II each containing 30 rats. 0.1 ml of saline solution and 0.1 ml of gluteraldehyde cross-linked bovine collagen were injected into the submucosa of bladder of first (control and second groups, respectively. Both group I and II were further subdivided into 3 other groups as Group IA, IB, IC and Group IIA, IIB, IIC according to the sacrification period. Group IA and IIA, IB and IIB, IC and IIC rats (10 rats for each group were sacrificed 3, 6, and 12 months after surgical procedure, respectively. Two slides prepared from injection site of the bladder were evaluated completely for each rat by being unaware of the groups and at random by two independent senior pathologists to determine the fibroblast invasion, collagen formation, capillary ingrowth and inflammatory reaction. Additionally, randomized brain sections from each rat were also examined to detect migration of the injection material. The measurements were made using an ocular micrometer at ×10 magnification. The results were assessed using t-tests for paired and independent samples, with p Results Migration to the brain was not detected in any group. Significant histopathological changes in the gluteraldehyde cross-linked bovine collagen injected groups were fibroblast invasion in 93.3%, collagen formation in 73.3%, capillary ingrowth in 46.6%, inflamatory reaction in 20%. Conclusion We emphasize that the usage of gluteraldehyde cross-linked bovine collagen in children appears to be safe for endoscopic treatment of vesicoureteral reflux.

  18. Distribution of Young's modulus in porcine corneas after riboflavin/UVA-induced collagen cross-linking as measured by atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    Jan Seifert

    Full Text Available Riboflavin/UVA-induced corneal collagen cross-linking has become an effective clinical application to treat keratoconus and other ectatic disorders of the cornea. Its beneficial effects are attributed to a marked stiffening of the unphysiologically weak stroma. Previous studies located the stiffening effect predominantly within the anterior cornea. In this study, we present an atomic force microscopy-derived analysis of the depth-dependent distribution of the Young's modulus with a depth resolution of 5 µm in 8 cross-linked porcine corneas and 8 contralateral controls. Sagittal cryosections were fabricated from every specimen and subjected to force mapping. The mean stromal depth of the zone with effective cross-linking was found to be 219 ± 67 µm. Within this cross-linked zone, the mean Young's modulus declined from 49 ± 18 kPa at the corneal surface to 46 ± 17 kPa, 33 ± 11 kPa, 17 ± 5 kPa, 10 ± 4 kPa and 10 ± 4 kPa at stromal depth intervals of 0-50 µm, 50-100 µm, 100-150 µm, 150-200 µm and 200-250 µm, respectively. This corresponded to a stiffening by a factor of 8.1 (corneal surface, 7.6 (0-50 µm, 5.4 (50-100 µm, 3.0 (100-150 µm, 1.6 (150-200 µm, and 1.5 (200-250 µm, when compared to the Young's modulus of the posterior 100 µm. The mean Young's modulus within the cross-linked zone was 20 ± 8 kPa (2.9-fold stiffening, while it was 11 ± 4 kPa (1.7-fold stiffening for the entire stroma. Both values were significantly distinct from the mean Young's modulus obtained from the posterior 100 µm of the cross-linked corneas and from the contralateral controls. In conclusion, we were able to specify the depth-dependent distribution of the stiffening effect elicited by standard collagen cross-linking in porcine corneas. Apart from determining the depth of the zone with effective corneal cross-linking, we also developed a method that allows for atomic force microscopy-based measurements of gradients of Young's modulus in soft

  19. PACK-CXL: Corneal cross-linking for treatment of infectious keratitis

    Directory of Open Access Journals (Sweden)

    David Tabibian

    2015-01-01

    Full Text Available This article discusses corneal cross-linking (CXL and how it transitioned from a modality for treating corneal ectatic disorders to an inventive means of treating infectious keratitis. Initially, CXL was successfully developed to halt the progression of ectatic diseases such as keratoconus, using the standard Dresden protocol. Later, indications were extended to treat iatrogenic ectasia developing after laser-assisted in situ keratomileusis (LASIK and photo-refractive keratectomy (PRK. At the time, it had been postulated that the combination of ultraviolet light with riboflavin could not only biomechanically strengthen the cornea but also was capable of destroying living cells and organisms including keratocytes and pathogens. Thus a new and innovative concept of treatment for infectious keratitis emerged through the use of CXL technology. Initially only advanced infectious melting ulcers resisting standard microbicidal therapy were treated with CXL in addition to standard therapy. In subsequent studies CXL was also used to treat bacterial keratitis as first line therapy without the use of concomitant antibiotic therapy. With the increasing interest in CXL technology to treat infectious keratitis and to clearly separate its use from the treatment of ectatic disorders, a new term was adopted at the 9 th CXL congress in Dublin for this specific indication: PACK-CXL (photoactivated chromophore for infectious keratitis. PACK-CXL has the potential to eventually become an interesting alternative to standard antibiotic therapy in treating infectious corneal disorders, and may help reduce the global burden of microbial resistance to antibiotics and other therapeutic agents.

  20. Fracture mechanics of collagen fibrils: influence of natural cross-links.

    Science.gov (United States)

    Svensson, Rene B; Mulder, Hindrik; Kovanen, Vuokko; Magnusson, S Peter

    2013-06-04

    Tendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy technique to measure the mechanical behavior of individual collagen fibrils loaded to failure. Fibrils from human patellar tendons, rat-tail tendons (RTTs), NaBH₄ reduced RTTs, and tail tendons of Zucker diabetic fat rats were tested. We found a characteristic three-phase stress-strain behavior in the human collagen fibrils. There was an initial rise in modulus followed by a plateau with reduced modulus, which was finally followed by an even greater increase in stress and modulus before failure. The RTTs also displayed the initial increase and plateau phase, but the third region was virtually absent and the plateau continued until failure. The importance of cross-link lability was investigated by NaBH₄ reduction of the rat-tail fibrils, which did not alter their behavior. These findings shed light on the function of cross-links at the fibril level, but further studies will be required to establish the underlying mechanisms.

  1. Fluorescence imaging of tryptophan and collagen cross-links to evaluate wound closure ex vivo

    Science.gov (United States)

    Wang, Ying; Ortega-Martinez, Antonio; Farinelli, Bill; Anderson, R. R.; Franco, Walfre

    2016-02-01

    Wound size is a key parameter in monitoring healing. Current methods to measure wound size are often subjective, time-consuming and marginally invasive. Recently, we developed a non-invasive, non-contact, fast and simple but robust fluorescence imaging (u-FEI) method to monitor the healing of skin wounds. This method exploits the fluorescence of native molecules to tissue as functional and structural markers. The objective of the present study is to demonstrate the feasibility of using variations in the fluorescence intensity of tryptophan and cross-links of collagen to evaluate proliferation of keratinocyte cells and quantitate size of wound during healing, respectively. Circular dermal wounds were created in ex vivo human skin and cultured in different media. Two serial fluorescence images of tryptophan and collagen cross-links were acquired every two days. Histology and immunohistology were used to validate correlation between fluorescence and epithelialization. Images of collagen cross-links show fluorescence of the exposed dermis and, hence, are a measure of wound area. Images of tryptophan show higher fluorescence intensity of proliferating keratinocytes forming new epithelium, as compared to surrounding keratinocytes not involved in epithelialization. These images are complementary since collagen cross-links report on structure while tryptophan reports on function. HE and immunohistology show that tryptophan fluorescence correlates with newly formed epidermis. We have established a fluorescence imaging method for studying epithelialization processes during wound healing in a skin organ culture model, our approach has the potential to provide a non-invasive, non-contact, quick, objective and direct method for quantitative measurements in wound healing in vivo.

  2. Age-Related Long-Term Functional Results after Riboflavin UV A Corneal Cross-Linking.

    Science.gov (United States)

    Caporossi, Aldo; Mazzotta, Cosimo; Baiocchi, Stefano; Caporossi, Tomaso; Denaro, Rosario

    2011-01-01

    Purpose. To report a comparative prospective long-term functional analysis after Riboflavin UV A corneal cross-linking (CXL) in three different age groups of patients affected by progressive keratoconus (KC). Methods. Functional analysis comprised paediatric patients (≤18 years) included 152 eyes (29.5%); intermediate group (19-26 years) 286 eyes (55.4%), and adults (≥27 years) 78 eyes (15.1%). CXL was performed according to the Siena protocol by using the Vega CBM (Caporossi-Baiocchi-Mazzotta) X linker (CSO, Florence, Italy) at Siena University by the same authors. Pre- and post-op examinations included UCVA, BSCVA, corneal topography, and surface aberrometry (CSO Eye Top, Florence, Italy), at 48 months followup. Results. At 48 months followup paediatrics, intermediate, and adult patients showed a mean gain in UCVA of +0.2, +0.14 and +0.12 Snellen lines. BSCVA gained by a mean of +0.21, +0.2, and +0.1 Snellen lines. K(max) was reduced by a mean value of -0.9 D, -0.6 D, and -0.5 D, respectively. Coma values improved by a mean of -0.45 μm, -0.91 μm, and -0.19 μm, respectively. Treatment ensured a long-term keratoconus stabilization in over 90% of treated patients. Conclusion. According to our long-term comparative results, epithelium-off Riboflavin UV A cross-linking should be the first choice therapy of progressive KC, particularly in paediatric age and patients under 26 years.

  3. Age-Related Long-Term Functional Results after Riboflavin UV A Corneal Cross-Linking

    Directory of Open Access Journals (Sweden)

    Aldo Caporossi

    2011-01-01

    Full Text Available Purpose. To report a comparative prospective long-term functional analysis after Riboflavin UV A corneal cross-linking (CXL in three different age groups of patients affected by progressive keratoconus (KC. Methods. Functional analysis comprised paediatric patients (≤18 years included 152 eyes (29.5%; intermediate group (19–26 years 286 eyes (55.4%, and adults (≥27 years 78 eyes (15.1%. CXL was performed according to the Siena protocol by using the Vega CBM (Caporossi-Baiocchi-Mazzotta X linker (CSO, Florence, Italy at Siena University by the same authors. Pre- and post-op examinations included UCVA, BSCVA, corneal topography, and surface aberrometry (CSO Eye Top, Florence, Italy, at 48 months followup. Results. At 48 months followup paediatrics, intermediate, and adult patients showed a mean gain in UCVA of +0.2, +0.14 and +0.12 Snellen lines. BSCVA gained by a mean of +0.21, +0.2, and +0.1 Snellen lines. Kmax was reduced by a mean value of −0.9 D, −0.6 D, and −0.5 D, respectively. Coma values improved by a mean of −0.45 μm, −0.91 μm, and −0.19 μm, respectively. Treatment ensured a long-term keratoconus stabilization in over 90% of treated patients. Conclusion. According to our long-term comparative results, epithelium-off Riboflavin UV A cross-linking should be the first choice therapy of progressive KC, particularly in paediatric age and patients under 26 years.

  4. Corneal Cross-Linking (with a Partial Deepithelization) in Keratoconus with Five Years of Follow-Up

    Science.gov (United States)

    Galvis, Virgilio; Tello, Alejandro; Carreño, Néstor I.; Ortiz, Alvaro I.; Barrera, Rodrigo; Rodriguez, Carlos Julián; Ochoa, Miguel E.

    2016-01-01

    We performed a retrospective interventional case series including 80 eyes of 48 patients with keratoconus (KC) who were treated with modified corneal cross-linking (CXL) for KC (with a partial deepithelization in a pattern of stripes). The average follow-up was 5.8 years (with a minimum of 5 years). At the last follow-up visit, compared with preoperative values, there were no significant changes in spherical equivalent, average keratometry, corneal thickness, corneal hysteresis, or corneal resistance factor. The distance-corrected visual acuity was 20/39 preoperatively and 20/36 postoperatively (P = 0.3). The endothelial cell count decreased by 4.7% (P < 0.005). These findings suggest that this modified corneal CXL technique is a safe and effective alternative to halt the progression of KC up to five years after the procedure. However, some concerns remain as to whether this technique can affect in some degree the corneal endothelial cells. PMID:27199574

  5. Effect of nordihydroguaiaretic acid cross-linking on fibrillar collagen: in vitro evaluation of fibroblast adhesion strength and migration

    Directory of Open Access Journals (Sweden)

    Ana Y. Rioja

    2017-04-01

    Full Text Available Fixation is required to reinforce reconstituted collagen for orthopedic bioprostheses such as tendon or ligament replacements. Previous studies have demonstrated that collagen fibers cross-linked by the biocompatible dicatechol nordihydroguaiaretic acid (NDGA have mechanical strength comparable to native tendons. This work focuses on investigating fibroblast behavior on fibrillar and NDGA cross-linked type I collagen to determine if NDGA modulates cell adhesion, morphology, and migration. A spinning disk device that applies a range of hydrodynamic forces under uniform chemical conditions was employed to sensitively quantify cell adhesion strength, and a radial barrier removal assay was used to measure cell migration on films suitable for these quantitative in vitro assays. The compaction of collagen films, mediated by the drying and cross-linking fabrication process, suggests a less open organization compared to native fibrillar collagen that likely allowed the collagen to form more inter-chain bonds and chemical links with NDGA polymers. Fibroblasts strongly adhered to and migrated on native and NDGA cross-linked fibrillar collagen; however, NDGA modestly reduced cell spreading, adhesion strength and migration rate. Thus, it is hypothesized that NDGA cross-linking masked some adhesion receptor binding sites either physically, chemically, or both, thereby modulating adhesion and migration. This alteration in the cell-material interface is considered a minimal trade-off for the superior mechanical and compatibility properties of NDGA cross-linked collagen compared to other fixation approaches.

  6. Analysis of pseudoprogression after corneal cross-linking in children with progressive keratoconus.

    Science.gov (United States)

    Schuerch, Kaspar; Tappeiner, Christoph; Frueh, Beatrice E

    2016-11-01

    To analyse the long-term efficacy of corneal cross-linking (CXL) in children with keratoconus and to describe criteria for the detection of pseudoprogression. Evaluation of retrospectively collected corneal topography (Placido system) and tomography (Scheimpflug system) results after CXL in children (age 18 or younger). Twenty-five patients (33 eyes) were included. Follow-up was assessed after 1, 2, 3 and 4 years. Progression was defined as an increase in maximal keratometry (Kmax) of at least one dioptre (D) in 1 year. For the entire group, mean Kmax prior to CXL was 55.3 ± 7.3D and decreased significantly (p = 0.00001) after 1 year to 53.4 ± 7.4D. In 23 patients, the progression could be halted. Five cases of presumed progression were identified. One case showed marked steepening in Kmax 4 years after CXL, but the topographic parameters were unchanged. The tomography was repeated and showed that Kmax was stable. Two cases with limbal vernal keratoconjunctivitis (VKC) worsened both in corneal tomography and topography. After resolution of the limbal inflammation, the Kmax values returned to the values before the inflammation. We found two cases of true progression both of which had advanced keratoconus prior to CXL with a preoperative Kmax of 64.4, respectively, 75.1D. Our results confirm that CXL is effective in stabilizing keratoconus in children. True progression after CXL could only be verified in two of 33 eyes in a follow-up period of 37.5 months (SD ± 10 months). Two different measuring methods can help to detect diagnostic discrepancies and prevent false conclusions. Moreover, limbal vernal changes can cause transient pseudoprogression, reversible upon sufficient treatment. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  7. Transepithelial versus epithelium-off corneal cross-linking for the treatment of progressive keratoconus : A randomized controlled trial

    NARCIS (Netherlands)

    Soeters, Nienke; Wisse, Robert P L; Godefrooij, Daniël A.; Imhof, Saskia M.; Tahzib, Nayyirih G.

    2015-01-01

    Purpose  To compare the clinical effects and safety of transepithelial corneal cross-linking (CXL) to epithelium-off (epi-off) CXL in progressive keratoconus.  Design Randomized clinical trial (noninferiority). Methods Patients received either transepithelial CXL with Ricrolin TE (n = 35) or epi-off

  8. [Healing of osseous defects by guided bone regeneration using ribose cross linked collagen membranes].

    Science.gov (United States)

    Tal, H

    2004-07-01

    The ultimate goal of periodontal therapy has long been the complete regeneration of the periodontal attachment apparatus. Guided Tissue Regeneration (GTR) and Guided Bone Regeneration (GBR) are two regenerative procedures which converted this goal from a dream to reality. In search of a biocompatible resorbable tissue barrier, collagen, being a natural protein and a weak antigen, has attracted much interest and became the focus of much intention during the 80's and the 90's. The understanding that cross linking of collagen with aldehyde sugars, especially ribose, produces collagen which is highly resistant to resorption in vivo led to the development of a "natural" Crossed-Linked Collagen Barrier (CB-SX). Animal and Human studies have shown that the newly developed membrane is biocompatible, remains intact in the tissues 6 months and more, and results in impressive guided tissue/bone regeneration. Spontaneous early exposure of the membrane is common but the healing potential of the resulted tissue dehiscence is favorable with no tendency for bacterial infection. The commercial version of the CB-SX is especially suitable for GBR procedures; it is highly recommended that the gingival flaps involved will properly be released, will lack tension, and be thoroughly sutured.

  9. Properties of collagen gels cross-linked by N-hydroxysuccinimide activated adipic acid deriviate.

    Science.gov (United States)

    Duan, Lian; Liu, Wentao; Tian, Zhenhua; Li, Conghu; Li, Guoying

    2014-08-01

    In order to improve the properties of collagen gel, N-hydroxysuccinimide activated adipic acid derivative (NHS-AA) was introduced into the formation of collagen fibrils. NHS-AA with different [NHS-AA]/[NH2] ratios (0.1-1.5, calculated by [ester group] of NHS-AA and [NH2] of lysine and hydroxylysine residues of collagen) was added after, simultaneously with or before the formation of collagen fibrils (abbreviated CAF, CSF and CBF, respectively) to obtain different collagen gels. With the same dose of NHS-AA, the cross-linking degree for CAF was lower than those for CSF and CBF. The formation of collagen fibrils was restrained by NHS-AA for CSF and CBF while that for CAF was unaffected. When the dose of NHS-AA increased from 0.1 to 1.5, the water contents of CSF and CBF increased while that of CAF had no obvious change. With lower dose of NHS-AA (0.1), CAF possessed higher value of G' (87.3Pa) and the best thermal stability (47.6°C). As the ratio of [NHS-AA]/[NH2] increased to 1.5, CSF had the maximum value of G' (288.8Pa) and CAF had the best thermal stability (52.9°C). These results showed collagen gels with different properties could be prepared by adding NHS-AA with different adding sequence and dose.

  10. The molecular mechanism of photodynamic therapy to fibrosis: Regulation on the pyridinoline cross-link formation in collagen

    Institute of Scientific and Technical Information of China (English)

    ZHANG JuCheng; LIU Wei; YI ZhongZhou; CHEN Rui; LI Ying; MIN Yong

    2009-01-01

    Fibrotic processes in tissues are characterised by an excessive accumulation of collagen containing increased levels of pyridinoline cross-links,which has been taken as an important criterion to diagnose the fibrosis.Hypocrellin B (HB) is a natural photosensitizer with excellent photodynamic activity but very low dark-toxicity.In the current work,main purpose was to clarify if photodynamic action of HB could be applied to regulating the level of pyridinoline cross-link in collagen.To use gelatin as a model collagen,it was observed that the pyridinoline cross-link formation was effectively degraded by HB photodynamic action in the gelatin,suggesting the level of pyridinoline cross-link formation in collagen may be photodynamically regulated to a normal level.Furthermore,mechanism of the photodynamic action of HB was studied.

  11. Long-term safety and efficacy follow-up of prophylactic higher fluence collagen cross-linking in high myopic laser-assisted in situ keratomileusis

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2012-07-01

    Full Text Available Anastasios John KanellopoulosLaservision.gr Institute, Athens, Greece, and New York University Medical School, New York, NY, USABackground: The purpose of this study was to evaluate the safety and efficacy of ultraviolet A irradiation cross-linking on completion for cases of high myopic laser-assisted in situ keratomileusis (LASIK.Methods: Forty-three consecutive LASIK cases treated with femtosecond laser flap and the WaveLight excimer platform were evaluated perioperatively for uncorrected visual acuity, best corrected spectacle visual acuity, refraction, keratometry, topography, total and flap pachymetry, corneal optical coherence tomography, and endothelial cell count. All eyes at the completion of LASIK had cross-linking through the repositioned flap, with higher fluence (10 mW/cm2 ultraviolet light of an average 370 µm wavelength and 10 mW/cm2 fluence applied for 3 minutes following an earlier single instillation of 0.1% riboflavin within the flap interface. Mean follow-up duration was 3.5 (range 1.0–4.5 years.Results: Mean uncorrected visual acuity changed from 0.2 to 1.2, best corrected spectacle visual acuity from 1.1 to 1.2, spherical equivalent from -7.5 diopters (D to -0.2 D, keratometry from 44.5 D to 38 D, flap pachymetry from 105 µm to, total pachymetry from 525 to 405, and endothelial cell count from 2750 to 2800. None of the cases developed signs of ectasia or significant regression during follow-up.Conclusion: Prophylactic collagen cross-linking for high-risk LASIK cases appears to be a safe and effective adjunctive treatment for refractive regression and potential ectasia. This application may be viewed as prophylactic customization of the biomechanical behavior of corneal collagen.Keywords: prophylactic collagen cross-linking, laser-assisted in situ keratomileusis, high-risk, post-LASIK ectasia

  12. Corneal crossed links: a new alternative in the treatment of ectasia Enlaces cruzados corneales: una nueva alternativa en el tratamiento de las ectasias

    Directory of Open Access Journals (Sweden)

    Eduardo Rojas Álvarez

    2009-09-01

    Full Text Available

    Cross-linking a technique that allows increasing the creation of covalent links through the process of photo-oxidation among the collagen fibers and enhance the corneal biomechanical stabilization. The main objective of this procedure is to stop the development of ectasia. The indications include the Keratoconus and Pellucid Marginal Degeneration. This can reduce the necessity for permanent keratoplasty and is highly efficient in the treatment and prophylaxis of keratectasia after ablation caused by laser. Many reviewed articles prove the security and efficacy of this treatment. The confocal microscopy techniques have shown significant swelling and resistance of corneal stroma after this procedure. Density of endothelial cell and transparency of the cornea and crystallin remain unchanged. This is a simple, safe and non-invasive technique with promising results. Since this is not expensive it could be particularly useful in developing countries where corneal transplant and other procedures are very expensive.

    Los enlaces cruzados son una técnica que favorece el incremento de la formación de enlaces covalentes, por un proceso de fotooxidación, entre la fibras de colágeno y propician la estabilización biomecánica de la córnea. El objetivo principal al realizarlos es detener la progresión de ectasia. Las indicaciones incluyen el queratocono y la degeneración marginal pelúcida. Puede reducir la necesidad de queratoplastia penetrante y resulta muy eficaz en el tratamiento y profilaxis de la queratectasia posterior a la ablación por láser excimer. Numerosos artículos revisados demuestran la seguridad y eficacia de este procedimiento. La microscopía confocal ha mostrado engrosamiento y resistencia significativa del estroma corneal después de realizado y que permanecen sin cambios la densidad de células endoteliales y la transparencia del cristalino y la córnea. Es una técnica simple, segura y no invasiva con resultados

  13. Influence of cross-link structure, density and mechanical properties in the mesoscale deformation mechanisms of collagen fibrils.

    Science.gov (United States)

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

    2015-12-01

    Collagen is a ubiquitous protein with remarkable mechanical properties. It is highly elastic, shows large fracture strength and enables substantial energy dissipation during deformation. Most of the connective tissue in humans consists of collagen fibrils composed of a staggered array of tropocollagen molecules, which are connected by intermolecular cross-links. In this study, we report a three-dimensional coarse-grained model of collagen and analyze the influence of enzymatic cross-links on the mechanics of collagen fibrils. Two representatives immature and mature cross-links are implemented in the mesoscale model using a bottom-up approach. By varying the number, type and mechanical properties of cross-links in the fibrils and performing tensile test on the models, we systematically investigate the deformation mechanisms of cross-linked collagen fibrils. We find that cross-linked fibrils exhibit a three phase behavior, which agrees closer with experimental results than what was obtained using previous models. The fibril mechanical response is characterized by: (i) an initial elastic deformation corresponding to the collagen molecule uncoiling, (ii) a linear regime dominated by molecule sliding and (iii) the second stiffer elastic regime related to the stretching of the backbone of the tropocollagen molecules until the fibril ruptures. Our results suggest that both cross-link density and type dictate the stiffness of large deformation regime by increasing the number of interconnected molecules while cross-links mechanical properties determine the failure strain and strength of the fibril. These findings reveal that cross-links play an essential role in creating an interconnected fibrillar material of tunable toughness and strength.

  14. Nondestructive fluorescence-based quantification of threose-induced collagen cross-linking in bovine articular cartilage

    Science.gov (United States)

    Kinnunen, Jussi; Kokkonen, Harri T.; Kovanen, Vuokko; Hauta-Kasari, Markku; Vahimaa, Pasi; Lammi, Mikko J.; Töyräs, Juha; Jurvelin, Jukka S.

    2012-09-01

    Extensive collagen cross-linking affects the mechanical competence of articular cartilage: it can make the cartilage stiffer and more brittle. The concentrations of the best known cross-links, pyridinoline and pentosidine, can be accurately determined by destructive high-performance liquid chromatography (HPLC). We explore a nondestructive evaluation of cross-linking by using the intrinsic fluorescence of the intact cartilage. Articular cartilage samples from bovine knee joints were incubated in threose solution for 40 and 100 h to increase the collagen cross-linking. Control samples without threose were also prepared. Excitation-emission matrices at wavelengths of 220 to 950 nm were acquired from the samples, and the pentosidine and pyridinoline cross-links and the collagen concentrations were determined using HPLC. After the threose treatment, pentosidine and lysyl pyridinole (LP) concentrations increased. The intrinsic fluorescence, excited below 350 nm, decreased and was related to pentosidine [r=-0.90, 240/325 nm (excitation/emission)] or LP (r=-0.85, 235/285 nm) concentrations. Due to overlapping, the changes in emission could not be linked specifically to the recorded cross-links. However, the fluorescence signal enabled a nondestructive optical estimate of changes in the pentosidine and LP cross-linking of intact articular cartilage.

  15. Trans epithelial corneal collagen crosslinking for progressive keratoconus: 6 months follow up.

    Science.gov (United States)

    De Bernardo, Maddalena; Capasso, Luigi; Tortori, Antonia; Lanza, Michele; Caliendo, Luisa; Rosa, Nicola

    2014-12-01

    To evaluate keratoconus biomechanical changes after transepithelial corneal collagen cross linking (TE CXL) using riboflavin and ultraviolet A (UVA). Second University of Naples, Naples, Italy. Prospective non comparative case series study. Patients with progressive keratoconus were examined, before and during a 6 months follow up after TE CXL, with a Pentacam, an Ocular Response Analyzer and an IOLMaster. Best corrected visual acuity (BCVA), refraction, corneal thinnest point (CTP), keratometry readings at the keratoconus apex (Kmax), axial eye length (AL), corneal volume (CV) anterior chamber volume (ACV), anterior chamber depth (ACD), corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated. Thirty-six eyes of 36 patients with progressive keratoconus were analyzed. Six months after treatment there was a significant improvement in BCVA (pkeratoconus, without affecting in negative way the corneal elasticity. Copyright © 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

  16. Quantitative Raman characterization of cross-linked collagen thin films as a model system for diagnosing early osteoarthritis

    Science.gov (United States)

    Wang, Chao; Durney, Krista M.; Fomovsky, Gregory; Ateshian, Gerard A.; Vukelic, Sinisa

    2016-03-01

    The onset of osteoarthritis (OA)in articular cartilage is characterized by degradation of extracellular matrix (ECM). Specifically, breakage of cross-links between collagen fibrils in the articular cartilage leads to loss of structural integrity of the bulk tissue. Since there are no broadly accepted, non-invasive, label-free tools for diagnosing OA at its early stage, Raman spectroscopyis therefore proposed in this work as a novel, non-destructive diagnostic tool. In this study, collagen thin films were employed to act as a simplified model system of the cartilage collagen extracellular matrix. Cross-link formation was controlled via exposure to glutaraldehyde (GA), by varying exposure time and concentration levels, and Raman spectral information was collected to quantitatively characterize the cross-link assignments imparted to the collagen thin films during treatment. A novel, quantitative method was developed to analyze the Raman signal obtained from collagen thin films. Segments of Raman signal were decomposed and modeled as the sum of individual bands, providing an optimization function for subsequent curve fitting against experimental findings. Relative changes in the concentration of the GA-induced pyridinium cross-links were extracted from the model, as a function of the exposure to GA. Spatially resolved characterization enabled construction of spectral maps of the collagen thin films, which provided detailed information about the variation of cross-link formation at various locations on the specimen. Results showed that Raman spectral data correlate with glutaraldehyde treatment and therefore may be used as a proxy by which to measure loss of collagen cross-links in vivo. This study proposes a promising system of identifying onset of OA and may enable early intervention treatments that may serve to slow or prevent osteoarthritis progression.

  17. Corneal collagen crosslinking for keratoconus. A review

    Directory of Open Access Journals (Sweden)

    M. M. Bikbov

    2014-10-01

    Full Text Available Photochemical crosslinking is widely applied in ophthalmology. Its biochemical effect is due to the release of singlet oxygen that promotes anaerobic photochemical reaction. Keratoconus is one of the most common corneal ectasia affecting 1 in 250 to 250 000 persons. Currently, the rate of iatrogenic ectasia following eximer laser refractive surgery increases due to biomechanical weakening of the cornea. Morphologically and biochemically, ectasia is characterized by corneal layers thinning, contact between the stroma and epithelium resulting from Bowman’s membrane rupture, chromatin fragmentation in keratocyte nuclei, phagocytosis, abnormal staining and arrangement of collagen fibers, enzyme system disorders, and keratocyte apoptosis. In corneal ectasia, altered enzymatic processes result in the synthesis of abnormal collagen. Collagen packing is determined by the activity of various extracellular matrix enzymes which bind amines and aldehydes of collagen fiber amino acids. In the late stage, morphological changes of Descemet’s membrane (i.e., rupture and detachment develop. Abnormal hexagonal-shaped keratocytes and their apoptosis are the signs of endothelial dystrophy. The lack of analogs in domestic ophthalmology encouraged the scientists of Ufa Eye Research Institute to develop a device for corneal collagen crosslinking. The parameters of ultraviolet (i.e., wavelength, exposure time, power to achieve the desired effect were identified. The specifics of some photosensitizers in the course of the procedure were studied. UFalink, a device for UV irradiation of cornea, and photosensitizer Dextralink were developed and adopted. Due to the high risk of endothelial damage, this treatment is contraindicated in severe keratoconus (CCT less than 400 microns. Major effects of corneal collagen crosslinking are the following: Young’s modulus (modulus of elasticity increase by 328.9 % (on average, temperature tolerance increase by 5

  18. Corneal collagen crosslinking for keratoconus. A review

    Directory of Open Access Journals (Sweden)

    M. M. Bikbov

    2014-01-01

    Full Text Available Photochemical crosslinking is widely applied in ophthalmology. Its biochemical effect is due to the release of singlet oxygen that promotes anaerobic photochemical reaction. Keratoconus is one of the most common corneal ectasia affecting 1 in 250 to 250 000 persons. Currently, the rate of iatrogenic ectasia following eximer laser refractive surgery increases due to biomechanical weakening of the cornea. Morphologically and biochemically, ectasia is characterized by corneal layers thinning, contact between the stroma and epithelium resulting from Bowman’s membrane rupture, chromatin fragmentation in keratocyte nuclei, phagocytosis, abnormal staining and arrangement of collagen fibers, enzyme system disorders, and keratocyte apoptosis. In corneal ectasia, altered enzymatic processes result in the synthesis of abnormal collagen. Collagen packing is determined by the activity of various extracellular matrix enzymes which bind amines and aldehydes of collagen fiber amino acids. In the late stage, morphological changes of Descemet’s membrane (i.e., rupture and detachment develop. Abnormal hexagonal-shaped keratocytes and their apoptosis are the signs of endothelial dystrophy. The lack of analogs in domestic ophthalmology encouraged the scientists of Ufa Eye Research Institute to develop a device for corneal collagen crosslinking. The parameters of ultraviolet (i.e., wavelength, exposure time, power to achieve the desired effect were identified. The specifics of some photosensitizers in the course of the procedure were studied. UFalink, a device for UV irradiation of cornea, and photosensitizer Dextralink were developed and adopted. Due to the high risk of endothelial damage, this treatment is contraindicated in severe keratoconus (CCT less than 400 microns. Major effects of corneal collagen crosslinking are the following: Young’s modulus (modulus of elasticity increase by 328.9 % (on average, temperature tolerance increase by 5

  19. Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology

    DEFF Research Database (Denmark)

    Hansen, Philip; Haraldsson, Bjarki Thor; Aagaard, Per

    2010-01-01

    The human patellar tendon is frequently affected by tendinopathy, but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross......-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined...

  20. The reparative response to cross-linked collagen-based scaffolds in a rat spinal cord gap model.

    Science.gov (United States)

    Cholas, Rahmatullah H; Hsu, Hu-Ping; Spector, Myron

    2012-03-01

    Prior work demonstrated the improvement of peripheral nerve regeneration in gaps implanted with collagen scaffold-filled collagen tubes, compared with nerve autografts, and the promise of such implants for treating gaps in spinal cord injury (SCI) in rats. The objective of this study was to investigate collagen implants alone and incorporating select therapeutic agents in a 5-mm full-resection gap model in the rat spinal cord. Two studies were performed, one with a 6-week time point and one with a 2-week time point. For the 6-week study the groups included: (1) untreated control, (2) dehydrothermally (DHT)-cross-linked collagen scaffold, (3) DHT-cross-linked collagen scaffold seeded with adult rat neural stem cells (NSCs), and (4) DHT-cross-linked collagen scaffold incorporating plasmid encoding glial cell line-derived neurotropic factor (pGDNF). The 2-week study groups were: (1) nontreated control, (2) DHT-cross-linked collagen scaffold; (3) DHT-cross-linked collagen scaffold containing laminin; and (4) carbodiimide-cross-linked collagen scaffold containing laminin. The tissue filling the defect of all groups at 6 weeks was largely composed of fibrous scar; however, the tissue was generally more favorably aligned with the long axis of the spinal cord in all of the treatment groups, but not in the control group. Quantification of the percentage of animals per group containing cystic cavities in the defect showed a trend toward fewer rats with cysts in the groups in which the scaffolds were implanted compared to control. All of the collagen implants were clearly visible and mostly intact after 2 weeks. A band of fibrous tissue filling the control gaps was not seen in the collagen implant groups. In all of the groups there was a narrowing of the spinal canal within the gap as a result of surrounding soft tissue collapse into the defect. The narrowing of the spinal canal occurred to a greater extent in the control and DHT scaffold alone groups compared to the DHT

  1. Polyanionic collagen membranes for guided tissue regeneration: Effect of progressive glutaraldehyde cross-linking on biocompatibility and degradation.

    Science.gov (United States)

    Veríssimo, D M; Leitão, R F C; Ribeiro, R A; Figueiró, S D; Sombra, A S B; Góes, J C; Brito, G A C

    2010-10-01

    The ultimate goal of periodontal therapy is to control periodontal tissue inflammation and to produce predictable regeneration of that part of the periodontium which has been lost as a result of periodontal disease. In guided tissue regeneration membranes function as mechanical barriers, excluding the epithelium and gingival corium from the root surface and allowing regeneration by periodontal ligament cells. This report aims to study the effect of glutaraldehyde (GA) cross-linking on mineralized polyanionic collagen (PAC) membranes by conducting a histological evaluation of the tissue response (biocompatibility) and by assessing the biodegradation of subcutaneous membrane implants in rats. We studied six different samples: a PAC, a PAC mineralized by alternate soaking processes for either 25 or 75 cycles (PAC 25 and PAC 75, respectively) and these films cross-linked by GA. Inflammatory infiltrate, cytokine dosage, fibrosis capsule thickness, metalloproteinase immunohistochemistry and membrane biodegradation after 1, 7, 15 and 30 days were measured. The inflammatory response was found to be more intense in membranes without cross-linking, while the fibrosis capsules became thicker in cross-linked membranes after 30 days. The membranes without cross-linking suffered intense biodegradation, while the membranes with cross-linking remained intact after 30 days. The cross-linking with GA reduced the inflammatory response and prevented degradation of the membranes over the entire course of the observation period. These membranes are thus an attractive option when the production of new bone depends on the prolonged presence of a mechanical barrier.

  2. Stromal demarcation line induced by corneal cross-linking in eyes with keratoconus and nonkeratoconic asymmetric topography.

    Science.gov (United States)

    Malta, João B N; Renesto, Adimara C; Moscovici, Bernardo K; Soong, H K; Campos, Mauro

    2015-02-01

    To evaluate stromal demarcation lines following corneal cross-linking (CXL) using anterior segment optical coherence tomography in patients with keratoconus and nonkeratoconic asymmetric topography. Fifth-nine eyes of 59 patients were enrolled in a retrospective comparative case series, of which 19 eyes had keratoconus and 40 eyes had asymmetric topography. Eyes with asymmetric topography were treated in preparation for photorefractive keratectomy. One month after CXL, a stromal demarcation line was evaluated at 5 standardized corneal points using anterior segment optical coherence tomography. Mean stromal demarcation line depths were measured at 5 points on the cornea, namely, centrally, 3.0 mm temporally, 1.5 mm temporally, 3.0 mm nasally, and 1.5 mm nasally. For the keratoconus group, the values were 178 ± 47, 123 ± 15, 152 ± 47, 125 ± 23, and 160 ± 43 μm, respectively. For the asymmetric corneal topography group (without keratoconus), they were 305 ± 64, 235 ± 57, 294 ± 50, 214 ± 54, and 285 ± 58 μm, respectively. There was no correlation between central corneal pachymetry and stromal demarcation line depth in all 5 measured corneal points in both groups. CXL treatment profiles are similar in keratoconic and nonkeratoconic eyes with asymmetric topography.

  3. Determination of the relationship between collagen cross-links and the bone-tissue stiffness in the porcine mandibular condyle.

    Science.gov (United States)

    Willems, Nop M B K; Mulder, Lars; Bank, Ruud A; Grünheid, Thorsten; den Toonder, Jaap M J; Zentner, Andrej; Langenbach, Geerling E J

    2011-04-07

    Although bone-tissue stiffness is closely related to the degree to which bone has been mineralized, other determinants are yet to be identified. We, therefore, examined the extent to which the mineralization degree, collagen, and its cross-links are related to bone-tissue stiffness. A total of 50 cancellous and cortical bone samples were derived from the right mandibular condyles of five young and five adult female pigs. The degree of mineralization of bone (DMB) was assessed using micro-computed tomography. Using high-performance liquid chromatography, we quantified the collagen content and the number of cross-links per collagen molecule of two enzymatic cross-links: hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), and one non-enzymatic cross-link: pentosidine (Pen). Nanoindentation was used to assess bone-tissue stiffness in three directions, and multiple linear regressions were used to calculate the correlation between collagen properties and bone-tissue stiffness, with the DMB as first predictor. Whereas the bone-tissue stiffness of cancellous bone did not differ between the three directions of nanoindentation, or between the two age groups, cortical bone-tissue stiffness was higher in the adult tissue. After correction for DMB, the cross-links studied did not increase the explained variance. In the young group, however, LP significantly improved the explained variance in bone-tissue stiffness. Approximately half of the variation in bone-tissue stiffness in cancellous and cortical bone was explained by the DMB and the LP cross-links and thus they cannot be considered the sole determinants of the bone-tissue stiffness.

  4. Corneal Cross-Linking for the Treatment of Keratoconus in a Patient with Ipsilateral Myelinated Retinal Nerve Fiber Layer

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    M. Leozappa

    2011-03-01

    Full Text Available Keratoconus associated with myelinated retinal nerve fibers is not frequent and the relationship between the two pathologies is difficult to explain, therefore studies and further investigation are required. The etiology of each condition may suggest the role of genetic factors. Follow-up is important to evaluate the progression of keratoconus and myelination. Here we describe the unusual coexistence of keratoconus and ipsilateral myelinated retinal nerve fiber layer and, for the first time, the corneal cross-linking treatment in this condition.

  5. Tranexamic acid, an inhibitor of plasminogen activation, reduces urinary collagen cross-link excretion in both experimental and rheumatoid arthritis

    NARCIS (Netherlands)

    Ronday, H.K.; TeKoppele, J.M.; Greenwald, R.A.; Moak, S.A.; Roos, J.A.D.M. de; Dijkmans, B.A.C.; Breedveld, F.C.; Verheijen, J.H.

    1998-01-01

    The plasminogen activation system is one of the enzyme systems held responsible for bone and cartilage degradation in rheumatoid arthritis (RA). In this study, we evaluated the effect of tranexamic acid (TEA), an inhibitor of plasminogen activation, on urinary collagen cross-link excretion and radio

  6. Determination of the relationship between collagen cross-links and the bone-tissue stiffness in the porcine mandibular condyle

    NARCIS (Netherlands)

    Willems, N.M.B.K.; Mulder, L.; Bank, R.A.; Grünheid, T.; Toonder, J.M.J. den; Zentner, A.; Langenbach, G.E.J.

    2011-01-01

    Although bone-tissue stiffness is closely related to the degree to which bone has been mineralized, other determinants are yet to be identified. We, therefore, examined the extent to which the mineralization degree, collagen, and its cross-links are related to bone-tissue stiffness. A total of 50 ca

  7. Introduction of quantitative and qualitative cornea optical coherence tomography findings induced by collagen cross-linking for keratoconus: a novel effect measurement benchmark

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    Kanellopoulos AJ

    2013-02-01

    Full Text Available A John Kanellopoulos1,2 George Asimellis11Laservision.gr Institute, Athens, Greece; 2New York University Medical School, New York, NY, USAPurpose: To introduce a novel, noninvasive technique to determine the depth and extent of anterior corneal stroma changes induced by collagen cross-linking (CXL using quantitative analysis of high-resolution anterior-segment optical coherence tomography (OCT post-operative images.Setting: Private clinical ophthalmology practice.Patients and methods: Two groups of corneal cross-sectional images obtained with the OptoVue RTVue anterior-segment OCT system were studied: group A (control consisted of unoperated, healthy corneas, with the exception of possible refractive errors. The second group consisted of keratoconic corneas with CXL that were previously operated on. The two groups were investigated for possible quantitative evidence of changes induced by the CXL, and specifically, the depth, horizontal extent, as well as the cross-sectional area of intrastromal hyper-reflective areas (defined in our study as the area consisting of pixels with luminosity greater than the mean +2 × standard deviation of the entire stromal cross section within the corneal stroma.Results: In all images of the second group (keratoconus patients treated with CXL there was evidence of intrastromal hyper-reflective areas. The hyper-reflective areas ranged from 0.2% to 8.8% of the cross-sectional area (mean ± standard deviation; 3.46% ± 1.92%. The extent of the horizontal hyper-reflective area ranged from 4.42% to 99.2% (56.2% ± 23.35% of the cornea image, while the axial extent (the vertical extent in the image ranged from 40.00% to 86.67% (70.98% ± 7.85%. There was significant statistical difference (P < 0.02 in these values compared to the control group, in which, by application of the same criteria, the same hyper-reflective area (owing to signal noise ranged from 0.00% to 2.51% (0.74% ± 0.63%.Conclusion: Herein, we introduce a

  8. Diaphragm Repair with a Novel Cross-Linked Collagen Biomaterial in a Growing Rabbit Model.

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    Steffi Mayer

    Full Text Available Neonates with congenital diaphragmatic hernia and large defects often require patch closure. Acellular collagen matrices (ACM have been suggested as an alternative to synthetic durable patches as they are remodeled by the host or could also be used for tissue engineering purposes.2.0x1.0 cm diaphragmatic defects were created in 6-weeks old New-Zealand white rabbits. We compared reconstruction with a purpose-designed cross-linked ACM (Matricel to 4-layer non-cross-linked small intestinal submucosa (SIS and a 1-layer synthetic Dual Mesh (Gore-Tex. Unoperated animals or animals undergoing primary closure (4/0 polyglecaprone served as age-matched controls. 60 (n = 25 resp. 90 (n = 17 days later, animals underwent chest x-ray and obduction for gross examination of explants, scoring of adhesion and inflammatory response. Also, uniaxial tensiometry was done, comparing explants to contralateral native diaphragmatic tissue.Overall weight nearly doubled from 1,554±242 g at surgery to 2,837±265 g at obduction (+84%. X-rays did show rare elevation of the left diaphragm (SIS = 1, Gore-Tex = 1, unoperated control = 1, but no herniation of abdominal organs. 56% of SIS and 10% of Matricel patches degraded with visceral bulging in four (SIS = 3, Matricel = 1. Adhesion scores were limited: 0.5 (Matricel to 1 (SIS, Gore-Tex to the left lung (p = 0.008 and 2.5 (Gore-Tex, 3 (SIS and 4 (Matricel to the liver (p<0.0001. Tensiometry revealed a reduced bursting strength but normal compliance for SIS. Compliance was reduced in Matricel and Gore-Tex (p<0.01. Inflammatory response was characterized by a more polymorphonuclear cell (SIS resp. macrophage (Matricel type of infiltrate (p<0.05. Fibrosis was similar for all groups, except there was less mature collagen deposited to Gore-Tex implants (p<0.05.Matricel induced a macrophage-dominated inflammatory response, more adhesions, had appropriate strength but a lesser compliance compared to native tissue. The herein

  9. Disentangling mechanisms involved in collagen pyridinoline cross-linking : The immunophilin FKBP65 is critical for dimerization of lysyl hydroxylase 2

    NARCIS (Netherlands)

    Gjaltema, Rutger A. F.; van der Stoel, Miesje M.; Boersema, Miriam; Bank, Ruud A.

    2016-01-01

    Collagens are subjected to extensive posttranslational modifications, such as lysine hydroxylation. Bruck syndrome (BS) is a connective tissue disorder characterized at the molecular level by a loss of telopeptide lysine hydroxylation, resulting in reduced collagen pyridinoline cross-linking. BS

  10. Refractive, Topographic, and Aberrometric Results at 2-Year Follow-Up for Accelerated Corneal Cross-Link for Progressive Keratoconus

    Science.gov (United States)

    Bozkurt, Ercüment; Akcay, Betul Ilkay Sezgin; Kurt, Tugba; Yildirim, Yusuf; Günaydin, Zehra Karaagaç; Demirok, Ahmet

    2017-01-01

    Purpose. To report the visual, refractive, and corneal topography and wavefront aberration results of accelerated corneal cross-linking (CXL) during a 24-month follow-up. Methods. Forty-seven eyes underwent riboflavin-ultraviolet A-induced accelerated CXL treatment (30 mW/cm2 with a total dose of 7.2 joules/cm2). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical and cylindrical values, keratometry (K) measurements (Ksteep, Kflat, Kavg, and Kapex), central corneal thickness, and anterior corneal aberrometric analyses including total wavefront error (WFE), total high order aberration (HOA), astigmatism, trefoil, coma, quadrafoil, secondary astigmatism, and spherical aberration were evaluated. Results. The mean UDVA and CDVA were significantly improved at 1 (p = 0.003 and p = 0.004, resp.) and 2 years after treatment (p = 0.001 and p = 0.001, resp.). The mean Ksteep, Kflat, Kaverage, and Kapex values were significantly lower than baseline at 12 months (p = 0.008, p = 0.024, p = 0.001, and p = 0.014, resp.) and 24 months (p = 0.014, p = 0.017, p = 0.001, and p = 0.012, resp.). Corneal thickness showed a significant decrease at 1 month. Total HOA and coma decreased significantly at the 12-month (p = 0.001 and p = 0.009, resp.) and 24-month visits (p = 0.001 and p = 0.007, resp.). Conclusion. Accelerated CXL (30 mW/cm2) was found to be effective in improving UDVA, CDVA, corneal topography readings, total HOA, and coma aberrations during the 24-month follow-up. PMID:28197339

  11. Corneal Cross-Linking for Pediatric Keratoconus : Long-Term Results

    NARCIS (Netherlands)

    Godefrooij, Daniel A; Soeters, Nienke; Imhof, Saskia M; Wisse, Robert P L

    2016-01-01

    PURPOSE: To assess the efficacy and safety of cross-linking in pediatric patients with keratoconus and to provide a systematic literature overview regarding this subject. METHODS: In this prospective cohort, 54 eyes of 36 pediatric patients with keratoconus underwent standard epithelium-off cross-li

  12. Corneal Cross-Linking with Riboflavin and UV-A in the Mouse Cornea in Vivo: Morphological, Biochemical, and Physiological Analysis

    Science.gov (United States)

    Kling, Sabine; Hammer, Arthur; Conti, Alain; Hafezi, Farhad

    2017-01-01

    Purpose To morphologically, biochemically, and physiologically characterize corneal cross-linking with riboflavin and UV-A light (CXL) in a newly established in vivo murine model. Methods C57BL/6 wild-type mice (N = 67) were treated with various CXL protocols, with modification of the following parameters: total energy (fluence) used, duration of UV-A irradiation, continuous versus pulsed irradiation, and CXL under hypoxic conditions (contact lens). Corneas were evaluated biomicroscopically, histologically, and using optical coherence tomography. Conformational collagen changes were evaluated via changes in the speed of enzymatic digestion. Results A fluence of 5.4 J/cm2 induced scar formation, while fluences of scar formation. Changes in the speed of enzymatic digestion suggest that CXL in mice, when compared to humans, requires less UV-A energy than the difference in corneal thickness between the species would suggest. Conclusions We demonstrated the in vivo response of very strong and very weak CXL and identified the best suited range of UV fluence in murine corneas. The presented murine CXL model may be helpful in future research addressing cellular and molecular pathways associated to CXL treatment. Translational Relevance Adverse tissue reactions following CXL treatment were observed, if the administered UV energy was out of the treatment window—raising concern about novel CXL treatment protocols that have not been previously validated in an experimental setting. PMID:28149672

  13. Quantification of carboxyl groups in carbodiimide cross-linked collagen sponges

    NARCIS (Netherlands)

    Everaerts, Frank; Torrianni, Mark; Hendriks, Marc; Feijen, Jan

    2007-01-01

    Glutaraldehyde (GA) fixation of bioprosthetic tissue is a well adapted technique, with commercial products on the market for almost 40 years. Amine groups present in tissue react with GA to form different types of cross-links. An estimation of the degree of cross-linking of the tissue can be obtaine

  14. Randomized Controlled Trial Comparing Transepithelial Corneal Cross-linking Using Iontophoresis with the Dresden Protocol in Progressive Keratoconus.

    Science.gov (United States)

    Lombardo, Marco; Giannini, Daniela; Lombardo, Giuseppe; Serrao, Sebastiano

    2017-06-01

    To compare clinical outcomes of transepithelial corneal cross-linking using iontophoresis (T-ionto CL) and standard corneal cross-linking (standard CL) for the treatment of progressive keratoconus 12 months after the operation. Prospective randomized controlled clinical trial. Thirty-four eyes of 25 participants with progressive keratoconus were randomized into T-ionto CL (22 eyes) or standard CL (12 eyes). T-ionto CL was performed using an iontophoresis device with dextran-free 0.1% riboflavin-5-phosphate solution with enhancers and by irradiating the cornea with a 10 mW/cm(2) ultraviolet A device for 9 minutes. Standard CL was performed according to the Dresden protocol. The primary outcome measure was stabilization of keratoconus after 12 months through analysis of maximum simulated keratometry readings (Kmax, diopters). Other outcome measures were corrected distance visual acuity (CDVA, logarithm of the minimum angle of resolution [logMAR]), manifest spherical equivalent refraction (D), central corneal thickness (CCT, micrometers) and endothelial cell density (ECD). Follow-up examinations were arranged at 3 and 7 days and 1, 3, 6, and 12 months. Twelve months after T-ionto CL and standard CL, Kmax on average flattened by -0.52±1.30 D (P = 0.06) and -0.82±1.20 D (P = 0.04), respectively. The mean change in CDVA was -0.10±0.12 logMAR (P = 0.003) and -0.03±0.06 logMAR (P = 0.10) after T-ionto CL and standard CL, respectively. The manifest spherical equivalent refraction changed on average by +0.71±1.44 D (P = 0.03) and +0.21±0.76 D (P = 0.38), respectively. The CCT and ECD measures did not change significantly in any group at 12 months. Significant differences in the outcome measures between treatments were found in the first week postoperatively. No complications occurred in the T-ionto CL group; 1 eye (8%) had sterile corneal infiltrates, which did not affect the final visual acuity, in the standard CL group. Significant visual and refractive

  15. Association of Cross Linked C-Telopeptide II Collagen and Hyaluronic Acid with Knee Osteoarthritis Severity

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    John Butar Butar

    2013-12-01

    Full Text Available BACKGROUND: This study was carried out to investigate the association of Cross Linked C-Telopeptide Type I & II Collagen (CTX-I and II and hyaluronic acid (HA with knee osteoarthritis (OA severity. METHODS: Sixty menopause women with primary knee OA were enrolled in this study during their visits to the Outpatient Department. Patients with knee pain during weight bearing, active or passive range of motion, or tenderness with Kellgren-Lawrence (KL grade of more than I were included. Patients with injury, inflammatory and metabolic diseases were excluded. Patients were put in a 10-hour fasting prior to withdrawal of morning blood samples for examinations of HA, CTX-I, interleukin 1 beta (IL-1β, and high sensitivity C reactive protein (hs-CRP level. Second void morning urine specimens were taken for CTXII assessment. HA, CTX-I and II levels were measured by enzyme-linked immunosorbent assay. RESULTS: Sixty menopausal female patients were included in this study, 35 with KL grade II, 17 grade III, and 8 grade IV. Means of CTX-II were significantly different between subjects KL grade IV and III (p=0.021. Correlation of KL grade was significant with CTX-II (p=0.001, r=0.412 and HA (p=0.0411, r=0.269. KL grades were not significantly associated with CTX-I (p=0.8364, r=-0.0272; IL-1β (p=0.5773, r=0.0853 and hs-CRP (p=0.2625, r=0.1470. CONCLUSIONS: CTX-II and HA were associated with severity of knee OA, suggesting that CTX-II and HA can be used as marker for knee OA severity. KEYWORDS: CTX-II, hyaluronic acid, otestoarthritis, knee.

  16. In situ cross-linked electrospun fiber scaffold of collagen for fabricating cell-dense muscle tissue.

    Science.gov (United States)

    Takeda, Naoya; Tamura, Kenichi; Mineguchi, Ryo; Ishikawa, Yumiko; Haraguchi, Yuji; Shimizu, Tatsuya; Hara, Yusuke

    2016-06-01

    Engineered muscle tissues used as transplant tissues in regenerative medicine should have a three-dimensional and cell-dense structure like native tissue. For fabricating a 3D cell-dense muscle tissue from myoblasts, we proposed the electrospun type I collagen microfiber scaffold of the string-shape like a harp. The microfibers were oriented in the same direction to allow the myoblasts to align, and were strung at low density with micrometer intervals to create space for the cells to occupy. To realize this shape of the scaffold, we employed in situ cross-linking during electrospinning process for the first time to collagen fibers. The collagen microfibers in situ cross-linked with glutaraldehyde stably existed in the aqueous media and completely retained the original shape to save the spaces between the fibers for over 14 days. On the contrary, the conventional cross-linking method by exposure to a glutaraldehyde aqueous solution vapor partially dissolved and damaged the fiber to lose a low-density shape of the scaffold. Myoblasts could penetrate into the interior of the in situ cross-linked string-shaped scaffold and form the cell-dense muscle tissues. Histochemical analysis showed the total area occupied by the cells in the cross section of the tissue was approximately 73 %. Furthermore, the resulting muscle tissue fabricated from primary myoblasts showed typical sarcomeric cross-striations and the entire tissue continuously pulsated by autonomous contraction. Together with the in situ cross-linking, the string-shaped scaffold provides an efficient methodology to fabricate a cell-dense 3D muscle tissue, which could be applied in regenerative medicine in future.

  17. Lower strength of the human posterior patellar tendon seems unrelated to mature collagen cross-linking and fibril morphology.

    Science.gov (United States)

    Hansen, Philip; Haraldsson, Bjarki Thor; Aagaard, Per; Kovanen, Vuokko; Avery, Nicholas C; Qvortrup, Klaus; Larsen, Jytte Overgaard; Krogsgaard, Michael; Kjaer, Michael; Peter Magnusson, S

    2010-01-01

    The human patellar tendon is frequently affected by tendinopathy, but the etiology of the condition is not established, although differential loading of the anterior and posterior tendon may be associated with the condition. We hypothesized that changes in fibril morphology and collagen cross-linking would parallel differences in material strength between the anterior and posterior tendon. Tendon fascicles were obtained from elective ACL surgery patients and tested micromechanically. Transmission electron microscopy was used to assess fibril morphology, and collagen cross-linking was determined by HPLC and calorimetry. Anterior fascicles were markedly stronger (peak stress: 54.3 +/- 21.2 vs. 39.7 +/- 21.3 MPa; P < 0.05) and stiffer (624 +/- 232 vs. 362 +/- 170 MPa; P < 0.01) than posterior fascicles. Notably, mature pyridinium type cross-links were less abundant in anterior fascicles (hydroxylysylpyridinoline: 0.859 +/- 0.197 vs. 1.416 +/- 0.250 mol/mol, P = 0.001; lysylpyridinoline: 0.023 +/- 0.006 vs. 0.035 +/- 0.006 mol/mol, P < 0.01), whereas pentosidine and pyrrole concentrations showed no regional differences. Fibril diameters tended to be larger in anterior fascicles (7.819 +/- 2.168 vs. 4.897 +/- 1.434 nm(2); P = 0.10). Material properties did not appear closely related to cross-linking or fibril morphology. These findings suggest region-specific differences in mechanical, structural, and biochemical properties of the human patellar tendon.

  18. Characterization of cross-linked porous gelatin carriers and their interaction with corneal endothelium: biopolymer concentration effect.

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    Jui-Yang Lai

    Full Text Available Cell sheet-mediated tissue regeneration is a promising approach for corneal reconstruction. However, the fragility of bioengineered corneal endothelial cell (CEC monolayers allows us to take advantage of cross-linked porous gelatin hydrogels as cell sheet carriers for intraocular delivery. The aim of this study was to further investigate the effects of biopolymer concentrations (5-15 wt% on the characteristic and safety of hydrogel discs fabricated by a simple stirring process combined with freeze-drying method. Results of scanning electron microscopy, porosity measurements, and ninhydrin assays showed that, with increasing solid content, the pore size, porosity, and cross-linking index of carbodiimide treated samples significantly decreased from 508±30 to 292±42 µm, 59.8±1.1 to 33.2±1.9%, and 56.2±1.6 to 34.3±1.8%, respectively. The variation in biopolymer concentrations and degrees of cross-linking greatly affects the Young's modulus and swelling ratio of the gelatin carriers. Differential scanning calorimetry measurements and glucose permeation studies indicated that for the samples with a highest solid content, the highest pore wall thickness and the lowest fraction of mobile water may inhibit solute transport. When the biopolymer concentration is in the range of 5-10 wt%, the hydrogels have high freezable water content (0.89-0.93 and concentration of permeated glucose (591.3-615.5 µg/ml. These features are beneficial to the in vitro cultivation of CECs without limiting proliferation and changing expression of ion channel and pump genes such as ATP1A1, VDAC2, and AQP1. In vivo studies by analyzing the rabbit CEC morphology and count also demonstrate that the implanted gelatin discs with the highest solid content may cause unfavorable tissue-material interactions. It is concluded that the characteristics of cross-linked porous gelatin hydrogel carriers and their triggered biological responses are in relation to biopolymer

  19. Lathyrism-induced alterations in collagen cross-links influence the mechanical properties of bone material without affecting the mineral

    Science.gov (United States)

    Paschalis, E.P.; Tatakis, D.N.; Robins, S.; Fratzl, P.; Manjubala, I.; Zoehrer, R.; Gamsjaeger, S.; Buchinger, B.; Roschger, A.; Phipps, R.; Boskey, A.L.; Dall'Ara, E.; Varga, P.; Zysset, P.; Klaushofer, K.; Roschger, P.

    2011-01-01

    In the present study a rat animal model of lathyrism was employed to decipher whether anatomically confined alterations in collagen cross-links are sufficient to influence the mechanical properties of whole bone. Animal experiments were performed under an ethics committee approved protocol. Sixty-four female (47 day old) rats of equivalent weights were divided into four groups (16 per group): Controls were fed a semi-synthetic diet containing 0.6% calcium and 0.6% phosphorus for 2 or 4 weeks and β-APN treated animals were fed additionally with β-aminopropionitrile (0.1% dry weight). At the end of this period the rats in the four groups were sacrificed, and L2–L6 vertebra were collected. Collagen cross-links were determined by both biochemical and spectroscopic (Fourier transform infrared imaging (FTIRI)) analyses. Mineral content and distribution (BMDD) were determined by quantitative backscattered electron imaging (qBEI), and mineral maturity/crystallinity by FTIRI techniques. Micro-CT was used to describe the architectural properties. Mechanical performance of whole bone as well as of bone matrix material was tested by vertebral compression tests and by nano-indentation, respectively. The data of the present study indicate that β-APN treatment changed whole vertebra properties compared to non-treated rats, including collagen cross-links pattern, trabecular bone volume to tissue ratio and trabecular thickness, which were all decreased (p < 0.05). Further, compression tests revealed a significant negative impact of β-APN treatment on maximal force to failure and energy to failure, while stiffness was not influenced. Bone mineral density distribution (BMDD) was not altered either. At the material level, β-APN treated rats exhibited increased Pyd/Divalent cross-link ratios in areas confined to a newly formed bone. Moreover, nano-indentation experiments showed that the E-modulus and hardness were reduced only in newly formed bone areas under the influence

  20. [Study on the effect of temperature on the conformation of cross-linked collagen by two-dimensional infrared correlation spectroscopy].

    Science.gov (United States)

    Chen, Yi-Hui; Tian, Hui-Lin; Li, Ji-Heng; Li, Guo-Ying

    2012-06-01

    The Fourier transform infrared spectroscopy and two dimensional correlation analysis method were applied to study a denaturing process of uncross-linked collagen and cross-linked collagen during varying temperature. It was found that the intensity of typically characteristic absorptions of collagen decreased and its peak shifted to low frequency, The amide II central absorbance peak moved to a lower frequency by about 10 cm(-1), which indicated that the inter-chain hydrogen bonds which stabilized the triple helix conformation of collagen were disrupted during thermal denaturation, resulting in a conformational change. The intensity of auto-peak at 1 515 cm(-1) was maximum, which suggested that the temperature had a big impact on amide II. In comparison with uncross-linked collagen, the intensity of cross-peaks of cross-linked collagen was weaker, which demonstrated that the effect of temperature on the structure of cross-linked collagen was smaller, and the thermal stability properties of collagen solution could be improved by cross-linking. While the order of second structure changes of cross-linked collagen was different. These fundamental data should provide available information for understanding the relationship between the structure and function of cross-linked collagen.

  1. Corneal cross-linking in a child with osteogenesis imperfecta syndrome and keratoconus

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    Sergio Kwitko

    2017-07-01

    Full Text Available Cross-linking (CXL is a well-established procedure in children with keratoconus (KC, but cases of CXL and osteogenesis imperfecta (OI have not been published in the literature, despite the association between physiopathology of these diseases. This is the first case, to the best of our knowledge, of a young girl with both OI and KC that underwent a CXL treatment. In this case, CXL was performed at 6-years-old prior to an expected progression, without complications and probably stopped further keratoconus progression.

  2. 胶原交联治疗眼科疾病的进展%Recent advancement of collagen cross-linking in the treatment of ophthalmic diseases

    Institute of Scientific and Technical Information of China (English)

    莫利娟; 李青松; 张兴儒

    2016-01-01

    Although collagen cross-linking (CXL) technology is still in the research and experimental stage in ophthalmology,but which is likely to significantly improve the mechanical strength of the collagen fibers,so a great number of ophthalmologists are becoming concerned about it.In recent years,based on the traditional CXL,the high-energy accelerated CXL,iontophoresis CXL and combination procedures are being described.Most of the experience gained from the treatment of the keratoconus.If individuals have been diagnosed as progressive keratoconus,they can be given CXL treatment early.After the operation,patients appear to increase the corneal stability and improve the visual acuity,while as to non-progression of keratoconus,the efficacy of the CXL is still in need of further study.In addition,CXL were attempted to be applied on the treatment of the iatrogenic keratoconus,transparent marginal degeneration,corneal edema and infectious corneal diseases,but the efficacy remains to be further verified.%虽然胶原交联(collagen cross-linking,CXL)技术在眼科还处于研究和试验性阶段,但因其能显著提高胶原纤维的机械强度,所以正在逐渐成为广大眼科医生关注的热点.近年来在传统角膜交联术的基础上,出现了高能量加速角膜交联、电离导入角膜交联以及联合治疗等方法,其在眼科疾病的应用所获得的经验大多来自于治疗圆锥角膜,一旦确认圆锥角膜处于进展期,可及早给予胶原交联治疗,术后角膜病情稳定,视力提高,而对于非进展期圆锥角膜的治疗有待进一步研究.另外,CXL在医源性圆锥角膜、透明边缘变性、角膜水肿和感染性角膜病变中也有了一些应用,具体效果有待进一步验证.

  3. Improving the mechanical properties of collagen-based membranes using silk fibroin for corneal tissue engineering.

    Science.gov (United States)

    Long, Kai; Liu, Yang; Li, Weichang; Wang, Lin; Liu, Sa; Wang, Yingjun; Wang, Zhichong; Ren, Li

    2015-03-01

    Although collagen with outstanding biocompatibility has promising application in corneal tissue engineering, the mechanical properties of collagen-based scaffolds, especially suture retention strength, must be further improved to satisfy the requirements of clinical applications. This article describes a toughness reinforced collagen-based membrane using silk fibroin. The collagen-silk fibroin membranes based on collagen [silk fibroin (w/w) ratios of 100:5, 100:10, and 100:20] were prepared by using silk fibroin and cross-linking by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. These membranes were analyzed by scanning electron microscopy and their optical property, and NaCl and tryptophan diffusivity had been tested. The water content was found to be dependent on the content of silk fibroin, and CS10 membrane (loading 10 wt % of silk fibroin) performed the optimal mechanical properties. Also the suture experiments have proved CS10 has high suture retention strength, which can be sutured in rabbit eyes integrally. Moreover, the composite membrane proved good biocompatibility for the proliferation of human corneal epithelial cells in vitro. Lamellar keratoplasty shows that CS10 membrane promoted complete epithelialization in 35 ± 5 days, and their transparency is restored quickly in the first month. Corneal rejection reaction, neovascularization, and keratoconus are not observed. The composite films show potential for use in the field of corneal tissue engineering.

  4. Evaluation of Intrastromal Riboflavin Concentration in Human Corneas after Three Corneal Cross-Linking Imbibition Procedures: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Antonella Franch

    2015-01-01

    Full Text Available Purpose. To compare stromal riboflavin concentration after three corneal cross-linking (CXL imbibition procedures: standard (EpiOff, transepithelial corneal (EpiOn, and iontophoresis-assisted technique (Ionto using 0.1% hypotonic riboflavin phosphate. Methods. Randomized open-label pilot clinical study. Twelve corneas/12 patients with advanced keratoconus were randomly divided into 4 groups for CXL (n=3. The corneas underwent imbibition with standard riboflavin EpiOff and with enhanced riboflavin solution (RICROLIN+ EpiOff, EpiOn, and iontophoresis techniques. Thereafter, deep anterior lamellar keratectomy procedure was performed and the obtained debrided corneal tissues were frozen. The maximal intrastromal riboflavin concentration was measured by high-performance liquid chromatography/mass spectrometry (mcg/dg. Results. The mean stromal concentration of riboflavin was 2.02±0.72 mcg/dg in EpiOff group, 4.33±0.12 mcg/g in EpiOff-RICROLIN+ group, 0.63±0.21 mcg/dg in EpiOn-RICROLIN+ group, and 1.15±0.27 mcg/dg in iontophoresis RICROLIN+ group. A 7-fold decrease in intrastromal riboflavin concentration was observed comparing EpiOn-RICROLIN+ and EpiOff-RICROLIN+ groups. Conclusion. The present pilot study indicates that both transepithelial CXL techniques in combination with hypotonic enhanced riboflavin formulation (RICROLIN+ were still inferior to the standard CXL technique; however, larger clinical studies to further validate the results are needed and in progress.

  5. A two-year's results of iontophoresis-assisted transepithelial corneal cross-linking for progressive keratoconus

    Directory of Open Access Journals (Sweden)

    Hong-Zhen Jia

    2016-07-01

    Full Text Available AIM: To report a two-year's results of iontophoresis-assisted transepithelial corneal cross-linking(I-CXLfor progressive keratoconus. METHODS: Thirty-four eyes in 24 patients with progressive keratoconus(mean age 21.0±5.6 years; range: 14-32 yearswere treated. After 1g/L riboflavin-distilled water solution was administered by iontophoresis-assited(current 1mAtransepithelial method for 5min in total, standard surface UVA irradiation(370nm, 3mW/cm2was performed at a 1-cm distance for 30min. The best corrected visual acuity(BCVAmeasured as LogMAR number, corneal refractive astigmatism, K1, K2, Kmean, Kmax, intraocular pressure, endothelial cell density, the thickness at corneal apex and the thinnest point were measured preoperatively and 2a postoperatively. RESULTS:At 2a after the procedure, BCVA(LogMARimproved from 0.32±0.25 to 0.25±0.19(t=2.849, P=0.015. K1 decreased from 47.12±4.33 to 46.06±4.77(t=2.652, P=0.015. K2 decreased from 51.36±5.59 to 50.40±6.16(t=2.121, P=0.047. Kmean decreased from 49.12±4.76 to 48.10±5.25(t=2.663, P=0.015. Kmax decreased from 57.57±8.30 to 55.91±8.14(t=2.398, P=0.026. The corneal apex thickness decreased from 476.90±38.71μm to 454.43±40.86μm(t=2.853, P=0.010. The thinnest thickness decreased from 464.38±39.92μm to 433.86±50.78μm(t=3.485, P=0.002. Corneal refractive astigmatism, intraocular pressure and endothelial cell density did not show significant changes. CONCLUSION: I-CXL for progressive keratoconus is safe and effective which can prevent deterioration of progressive keratoconus within 2a, but further long-term studies are necessary still.

  6. TGFβ affects collagen cross-linking independent of chondrocyte phenotype but strongly depending on physical environment

    NARCIS (Netherlands)

    Bastiaansen-Jenniskens, Y.M.; Koevoet, W.; Bart, A.C.W. de; Zuurmond, A.-M.; Bank, R.A.; Verhaar, J.A.N.; Groot, J. de; Osch, G.J.V.M. van

    2008-01-01

    Transforming growth factor beta (TGFβ) is often used in cartilage tissue engineering to increase matrix formation by cells with various phenotypes. However, adverse effects of TGFβ, such as extensive cross-linking in cultured fibroblasts, have also been reported. Our goal was to study effects of

  7. RELATIONS BETWEEN INVITRO CYTOTOXICITY AND CROSS-LINKED DERMAL SHEEP COLLAGENS

    NARCIS (Netherlands)

    VANLUYN, MJA; VANWACHEM, PB; DAMINK, LO; DIJKSTRA, PJ; FEIJEN, J; NIEUWENHUIS, P

    Collagen-based biomaterials have found various applications in the biomedical field. However, collagen-based biomaterials may induce cytotoxic effects. This study evaluated possible cytotoxic effects of (crosslinked) dermal sheep collagen (DSC) using a 7-d-methylcellulose cell culture with human

  8. Physical and mechanical properties of cross-linked type I collagen scaffolds derived from bovine, porcine, and ovine tendons.

    Science.gov (United States)

    Ghodbane, Salim A; Dunn, Michael G

    2016-11-01

    Collagen scaffolds are often utilized in tissue engineering applications where their performance depends on physical and mechanical properties. This study investigated the effects of collagen source (bovine, porcine, and ovine tendon) on properties of collagen sponge scaffolds cross-linked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS). Scaffolds were tested for tensile and compressive properties, stability (resistance to enzymatic degradation), pore size, and swelling ratio. No significant differences in tensile modulus were observed, but ovine scaffolds had significantly greater ultimate strain, stress, and toughness relative to bovine and porcine scaffolds. No significant differences in compressive properties, pore size, or swelling ratio were observed as a function of collagen source. Ovine scaffolds were more resistant to collagenase degradation compared to bovine samples, which were more resistant than porcine scaffolds. In comparison to bovine scaffolds, ovine scaffolds performed equivalently or superiorly in all evaluations, and porcine scaffolds were equivalent in all properties except enzymatic stability. These results suggest that collagen sponges derived from bovine, porcine, and ovine tendon have similar physical and mechanical properties, and are all potentially suitable materials for various tissue engineering applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2685-2692, 2016.

  9. Collagen cross-linking in keratoconus in Asian eyes: visual, refractive and confocal microscopy outcomes in a prospective randomized controlled trial.

    Science.gov (United States)

    Sharma, Namrata; Suri, Kunal; Sehra, Sri Vatsa; Titiyal, Jeewan S; Sinha, Rajesh; Tandon, Radhika; Vajpayee, Rasik B

    2015-12-01

    To evaluate the safety and efficacy of collagen cross-linking (CXL) in the treatment of keratoconus. A prospective randomized sham-controlled clinical trial was undertaken and 43 eyes with moderate to severe keratoconus were randomized into two groups that is the treatment (n = 23) and the sham (n = 20) group. CXL was performed with riboflavin (0.1 in 20 % dextran) followed by UVA radiation (365 nm, 3 mW/cm(2), 30 min). In the sham group, only riboflavin was administered without UVA radiation. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity, intraocular pressure, corneal thickness, keratometry, endothelial count, confocal microscopy were evaluated at baseline and at 1 week, 1, 3, and 6 months. In cases where CXL was done, UDVA improved by mean 0.11 ± 0.06 logMAR units at 6 months (P = 0.01). The refractive cylinder and spherical equivalent decreased by mean of 0.62 D (P = 0.01) and 0.5 D (P = 0.19), respectively. Ultrasonic central corneal thickness decreased by mean 22.7 ± 10.3 μm (P = 0.01). The maximum and minimum keratometry decreased by mean of 1.2 ± 0.8 D (P = 0.01) and 0.83 ± 1.2 D (P = 0.39), respectively. The specular count and intraocular pressure did not show any significant change. In the sham group, no significant change was observed in any parameter. Confocal analysis showed that the epithelial healing was complete at 1 week after crosslinking. The sub-epithelial plexus showed loss of nerve plexus at 1 month, regeneration of nerve fibers which started at 3 months and was complete at 6 months. The anterior stroma showed loss of keratocytes with honeycomb oedema and apoptotic bodies till 3 months. The regeneration of keratocytes started at 3 months and was complete at 6 months of follow-up. Collagen cross-linking is an effective procedure to halt progression in keratoconus. The confocal microscopic changes correlate with the outcomes in the treatment and the sham groups.

  10. Collagen/silicocarnotite composites, cross-linked with chondroitin sulphate: in vitro bioactivity

    OpenAIRE

    Lachezar Radev; Vladimir Hristov; Irena Michailova; Maria H. V. Fernandes; Isabel M. M. Salvado

    2011-01-01

    In this work we present the experimental results on synthesis, structure evolution and in vitro bioactivity of collagen-silicocarnotite-chondroitin sulphate composites. The obtained samples were synthesised by mixing collagen (C) and silicocarnotite (S) powder with C:S ratio of 75:25 and 25:75 wt.% in the presence of chondroitin sulphate (ChS). Collagen was diluted in 5M CH3COOH before mixing. The obtained materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT...

  11. Cross-linked type I and type II collagenous matrices for the repair of full-thickness articular cartilage defects--a study in rabbits.

    NARCIS (Netherlands)

    Buma, P.; Pieper, J.S.; Tienen, Tony van; Susante, J.L.C. van; Kraan, P.M. van der; Veerkamp, J.H.; Berg, W.B. van den; Veth, R.P.H.; Kuppevelt, A.H.M.S.M. van

    2003-01-01

    The physico-chemical properties of collagenous matrices may determine the tissue response after insertion into full-thickness articular cartilage defects. In this study, cross-linked type I and type II collagen matrices, with and without attached chondroitin sulfate, were implanted into full-thickne

  12. Collagens and proteoglycans of the corneal extracellular matrix

    Directory of Open Access Journals (Sweden)

    Y.M. Michelacci

    2003-08-01

    Full Text Available The cornea is a curved and transparent structure that provides the initial focusing of a light image into the eye. It consists of a central stroma that constitutes 90% of the corneal depth, covered anteriorly with epithelium and posteriorly with endothelium. Its transparency is the result of the regular spacing of collagen fibers with remarkably uniform diameter and interfibrillar space. Corneal collagen is composed of heterotypic fibrils consisting of type I and type V collagen molecules. The cornea also contains unusually high amounts of type VI collagen, which form microfibrillar structures, FACIT collagens (XII and XIV, and other nonfibrillar collagens (XIII and XVIII. FACIT collagens and other molecules, such as leucine-rich repeat proteoglycans, play important roles in modifying the structure and function of collagen fibrils.Proteoglycans are macromolecules composed of a protein core with covalently linked glycosaminoglycan side chains. Four leucine-rich repeat proteoglycans are present in the extracellular matrix of corneal stroma: decorin, lumican, mimecan and keratocan. The first is a dermatan sulfate proteoglycan, and the other three are keratan sulfate proteoglycans. Experimental evidence indicates that the keratan sulfate proteoglycans are involved in the regulation of collagen fibril diameter, and dermatan sulfate proteoglycan participates in the control of interfibrillar spacing and in the lamellar adhesion properties of corneal collagens. Heparan sulfate proteoglycans are minor components of the cornea, and are synthesized mainly by epithelial cells. The effect of injuries on proteoglycan synthesis is discussed.

  13. Feline chronic kidney disease is associated with upregulation of transglutaminase 2: a collagen cross-linking enzyme.

    Science.gov (United States)

    Sánchez-Lara, A C; Elliott, J; Syme, H M; Brown, C A; Haylor, J L

    2015-05-01

    Chronic kidney disease is a major cause of morbidity and mortality in cats. Transglutaminase 2 (TG2) is a calcium-dependent enzyme proposed to mediate tubulointerstitial fibrosis in the kidney by cross-linking collagen fibrils. Postmortem kidney tissue was obtained from primary renal azotemic (n = 10) and nonazotemic (n = 5) cats (14 domestic short hair, 1 Burmese; aged 9-23.7 years). Extracellular matrix protein deposition was determined by Masson's trichrome staining and collagen immunofluorescence. Total kidney transglutaminase (TG) enzyme activity and TG2 protein were measured in tissue homogenates by putrescine incorporation and Western blotting. Extracellular TG enzyme activity and TG2 protein were determined in situ by immunofluorescence, quantified by multiphase image analysis. Results were compared using the unpaired Student's t-test with Welch's correction. Elevated plasma creatinine, urea, and phosphate concentrations were associated with tubulointerstitial fibrosis but not glomerular fibrosis. Kidney homogenates from azotemic cats showed a 3-fold higher total TG enzyme activity and TG2 protein compared with kidneys from nonazotemic cats. Immunofluorescent studies performed in situ confirmed a 3-fold higher extracellular TG enzyme activity and TG2 protein in cats with azotemia. Tubulointerstitial TG2 showed a positive linear correlation with both renal function and tubulointerstitial fibrosis. In conclusion, for cats with azotemia, both filtration failure and tubulointerstitial fibrosis were associated with the upregulation of TG2, a collagen cross-linking enzyme and the major isoform of transglutaminase in the kidney. TG2 may provide a new therapeutic target for drugs designed to slow the progression of feline chronic kidney disease.

  14. Directed 2-dimensional organisation of collagen: Role of cross-linking and denaturing agents

    Indian Academy of Sciences (India)

    Nishtar nishad Fathima; Aruna Dhathathreyan; Thirumalachari Ramasami

    2010-11-01

    The effect of additives like curcumin and surfactants on the self-assembly of collagen from a simple 2-dimensional system of Langmuir films of the protein at air/solution interface has been attempted in this study using quartz crystal microbalance (QCM) and dynamic surface tensiometer. Though pure curcumin is not surface active, a synergistic effect of collagen with curcumin seems to lead to enhanced surface activity in the protein. In general, the presence of additives, increases the surface activity of collagen even for the lowest concentration and the largest change in surface activity is seen for collagen with sodium dodecyl sulfate (SDS). The results suggest interplay between the unexposed hydrophobic groups, and the opening out and solvation of the more charged or polar groups at the surface leading to aggregation followed by self-assembly. Modulation of aggregation at interface in collagen due to these additives may be an approach that could be explored for possible applications in bio-materials and for delivery of protein-drug complexes.

  15. Corneal collagen crosslinking: a systematic review.

    Science.gov (United States)

    Sorkin, Nir; Varssano, David

    2014-01-01

    Keratoconus (KCN) is an ectatic disorder with progressive corneal thinning and a clinical picture of corneal protrusion, progressive irregular astigmatism, corneal fibrosis and visual deterioration. Other ectatic corneal disorders include: post-LASIK ectasia (PLE) and pellucid marginal degeneration (PMD). Corneal crosslinking (CXL) is a procedure whereby riboflavin sensitization with ultraviolet A radiation induces stromal crosslinks. This alters corneal biomechanics, causing an increase in corneal stiffness. In recent years, CXL has been an established treatment for the arrest of KCN, PLE and PMD progression. CXL has also been shown to be effective in the treatment of corneal infections, chemical burns, bullous keratopathy and other forms of corneal edema. This is a current review of CXL - its biomechanical principles, the evolution of CXL protocols in the past, present and future, indications for treatment, treatment efficacy and safety.

  16. A review and meta-analysis of corneal cross-linking for post-laser vision correction ectasia.

    Science.gov (United States)

    Wan, Qi; Wang, Dan; Ye, HongQuan; Tang, Jing; Han, Yu

    2017-09-01

    The aim of this study was to review the safety and stability of cornea cross-linking (CXL) for the treatment of keratectasia after Excimer Laser Refractive Surgery. Eligible studies were identified by systematically searching PubMed, Embase, Web of Science and reference lists. Meta-analysis was performed using Stata 12.1 software. The primary outcome parameters included the changes of corrected distant visual acuity (CDVA), uncorrected visual acuity (UCVA), the maximum keratometry value (Kmax) and minimum keratometry value (Kmin), the surface regularity index (SRI), the surface asymmetry index (SAI), the keratoconus prediction index (KPI), corneal thickness, and endothelial cell count. Efficacy estimates were evaluated by weighted mean difference (WMD) and 95% confidence interval (CI) for absolute changes of the interested outcomes. Seven studies involving 118 patients treated with CXL for progressive ectasia after laser-assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) (140 eyes; the follow-up time range from 12 to 62 months) were included in the meta-analysis. The pooled results showed that there were no significant differences in Kmax and Kmin values after CXL (WMD = 0.584; 95% CI: -0.289 to 1.458; P = 0.19; WMD = 0.466; 95% CI: -0.625 to 1.556; P = 0.403, respectively). The CDVA improved significantly after CXL (WMD = 0.045; 95% CI: 0.010 to 0.079; P = 0.011), whereas UCVA did not differ statistically (WMD = 0.011; 95% CI: -0.055 to 0.077; P = 0.746). The changes were not statistically significant in SRI, SAI, and KPI (WMD = 0.116; 95% CI: -0.090 to 0.322; P = 0.269; WMD = 0.240; 95% CI: -0.200 to 0.681; P = 0.285; WMD = 0.045; 95% CI: -0.001 to 0.090; P = 0.056, respectively). Endothelial cell count and corneal thickness did not deteriorate (WMD = 12.634; 95% CI: -29.460 to 54.729; P = 0.556; WMD = 0.657; 95% CI: -9.402 to 10.717; P = 0.898, respectively). The study showed that CXL is a promising

  17. The relationship between collagen scaffold cross-linking agents and neutrophils in the foreign body reaction

    NARCIS (Netherlands)

    Ye, Qingsong; Harmsen, Martin C.; van Luyn, Marja J. A.; Bank, Ruud A.

    2010-01-01

    In order to get more insight into the role of neutrophils on the micro-environment and consequently on macrophages in the foreign body reaction in mice, we investigated the fate of the two differently crosslinked dermal sheep collagen disks (glutaraldehyde = GDSC, hexamethylenediisocyanate = HDSC) i

  18. BIOCOMPATIBILITY AND TISSUE REGENERATING CAPACITY OF CROSS-LINKED DERMAL SHEEP COLLAGEN

    NARCIS (Netherlands)

    VANWACHEM, PB; VANLUYN, MJA; DAMINK, LHHO; DIJKSTRA, PJ; FEIJEN, J; NIEUWENHUIS, P

    1994-01-01

    The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanate-crosslinked DSC (HDSC) seldo

  19. In vitro degradation of dermal sheep collagen cross-linked using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Olde damink, L.H.H.; Olde Damink, L.H.H.; Dijkstra, Pieter J.; van Luyn, M.J.A.; van Wachem, P.B.; Nieuwenhuis, P.; Feijen, Jan

    1996-01-01

    Bacterial collagenase was used to study the susceptibility of dermal sheep collagen (DSC) crosslinked with a mixture of the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydrochloride and N-hydroxysuccinimide (E/N-DSC) towards enzymatic degradation. Contrary to

  20. In vitro degradation of dermal sheep collagen cross-linked using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Damink, LHHO; Dijkstra, PJ; vanLuyn, MJA; vanWachem, PB; Nieuwenhuis, P; Feijen, J

    Bacterial collagenase was used to study the susceptibility of dermal sheep collagen (DSC) cross-inked with a mixture of the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (EIN-DSC) towards enzymatic degradation. Contrary to

  1. In vitro degradation of dermal sheep collagen cross-linked using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Damink, LHHO; Dijkstra, PJ; vanLuyn, MJA; vanWachem, PB; Nieuwenhuis, P; Feijen, J

    1996-01-01

    Bacterial collagenase was used to study the susceptibility of dermal sheep collagen (DSC) cross-inked with a mixture of the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (EIN-DSC) towards enzymatic degradation. Contrary to non-cross-

  2. In vitro degradation of dermal sheep collagen cross-linked using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Olde Damink, L.H.H.; Dijkstra, P.J.; Luyn, van M.J.A.; Wachem, van P.B.; Nieuwenhuis, P.; Feijen, J.

    1996-01-01

    Bacterial collagenase was used to study the susceptibility of dermal sheep collagen (DSC) crosslinked with a mixture of the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydrochloride and N-hydroxysuccinimide (E/N-DSC) towards enzymatic degradation. Contrary to non-cross

  3. GLUTARALDEHYDE AS A CROSS-LINKING AGENT FOR COLLAGEN-BASED BIOMATERIALS

    NARCIS (Netherlands)

    DAMINK, LHHO; DIJKSTRA, PJ; VANLUYN, MJA; VANWACHEM, PB; NIEUWENHUIS, P; FEIJEN, J

    1995-01-01

    The formation of Schiff bases during crosslinking of dermal sheep collagen (DSC) with glutaraldehyde (GA), their stability and their reactivity towards GA was studied. All available free amine groups had reacted with GA to form a Schiff base within 5 min after the start of the reaction under the con

  4. CALCIFICATION OF SUBCUTANEOUSLY IMPLANTED COLLAGENS IN RELATION TO CYTOTOXICITY, CELLULAR INTERACTIONS AND CROSS-LINKING

    NARCIS (Netherlands)

    VANLUYN, MJA; VANWACHEM, PB; DIJKSTRA, PJ; DAMINK, LHHO; FEIJEN, J

    1995-01-01

    In general, calcification of biomaterials occurs through an interaction of host and implanted material factors, but up to now the real origin of pathologic calcification is unknown. In this study we aimed to investigate incidence of calcification of (crosslinked) dermal sheep collagens (DSCs) with r

  5. Effect of green tea extract on advanced glycation and cross-linking of tail tendon collagen in streptozotocin induced diabetic rats.

    Science.gov (United States)

    Babu, Pon Velayutham Anandh; Sabitha, Kuruvimalai Ekambaram; Shyamaladevi, Chennam Srinivasulu

    2008-01-01

    Diabetes leads to modification of collagen such as advanced glycation and cross-linking which play an important role in the pathogenesis of diabetes mellitus. We have investigated the effect of green tea on modification of collagen in streptozotocin (60 mg/kg body weight) induced diabetic rats. To investigate the therapeutic effect of green tea, treatment was begun six weeks after the onset of diabetes and green tea extract (300 mg/kg body weight) was given orally for 4 weeks. The collagen content, extent of advanced glycation, advanced glycation end products (AGE) and cross-linking of tail tendon collagen were investigated. Green tea reduced the tail tendon collagen content which increased in diabetic rats. Accelerated advanced glycation and AGE in diabetic animals, as detected by Ehrlich's-positive material and collagen linked fluorescence respectively were reduced significantly by green tea. The solubility of tail tendon collagen decreased significantly in diabetic rats indicating a remarkable increase in the cross-linking, whereas green tea increases the solubility of collagen in diabetic rats. The present study reveals that green tea is effective in reducing the modification of tail tendon collagen in diabetic rats. Thus green tea may have a therapeutic effect in the treatment of glycation induced complications of diabetes.

  6. Understanding of the Viscoelastic Response of the Human Corneal Stroma Induced by Riboflavin/UV-A Cross-Linking at the Nano Level

    Science.gov (United States)

    Labate, Cristina; De Santo, Maria Penelope; Lombardo, Giuseppe; Lombardo, Marco

    2015-01-01

    Purpose To investigate the viscoelastic changes of the human cornea induced by riboflavin/UV-A cross-linking using Atomic Force Microscopy (AFM) at the nano level. Methods Seven eye bank donor corneas were investigated, after gently removing the epithelium, using a commercial AFM in the force spectroscopy mode. Silicon cantilevers with tip radius of 10 nm and spring elastic constants between 26- and 86-N/m were used to probe the viscoelastic properties of the anterior stroma up to 3 µm indentation depth. Five specimens were tested before and after riboflavin/UV-A cross-linking; the other two specimens were chemically cross-linked using glutaraldehyde 2.5% solution and used as controls. The Young’s modulus (E) and the hysteresis (H) of the corneal stroma were quantified as a function of the application load and scan rate. Results The Young’s modulus increased by a mean of 1.1-1.5 times after riboflavin/UV-A cross-linking (P<0.05). A higher increase of E, by a mean of 1.5-2.6 times, was found in chemically cross-linked specimens using glutaraldehyde 2.5% (P<0.05). The hysteresis decreased, by a mean of 0.9-1.5 times, in all specimens after riboflavin/UV-A cross-linking (P<0.05). A substantial decrease of H, ranging between 2.6 and 3.5 times with respect to baseline values, was observed in glutaraldehyde-treated corneas (P<0.05). Conclusions The present study provides the first evidence that riboflavin/UV-A cross-linking induces changes of the viscoelastic properties of the cornea at the scale of stromal molecular interactions. PMID:25830534

  7. Bovine pericardium based non-cross linked collagen matrix for successful root coverage, a clinical study in human

    Directory of Open Access Journals (Sweden)

    Schlee Markus

    2012-03-01

    Full Text Available Abstract Introduction The aim of this study was to clinically assess the capacity of a novel bovine pericardium based, non-cross linked collagen matrix in root coverage. Methods 62 gingival recessions of Miller class I or II were treated. The matrix was adapted underneath a coronal repositioned split thickness flap. Clinical values were assessed at baseline and after six months. Results The mean recession in each patient was 2.2 mm at baseline. 6 Months after surgery 86.7% of the exposed root surfaces were covered. On average 0,3 mm of recession remained. The clinical attachment level changed from 3.5 ± 1.3 mm to 1,8 ( ± 0,7 mm during the observational time period. No statistically significant difference was found in the difference of probing depth. An increase in the width of gingiva was significant. With a baseline value of 1.5 ± 0.9 mm an improvement of 2.4 ± 0.8 mm after six month could be observed. 40 out of 62 recessions were considered a thin biotype at baseline. After 6 months all 62 sites were assessed thick. Conclusions The results demonstrate the capacity of the bovine pericardium based non-cross linked collagen matrix for successful root coverage. This material was able to enhance gingival thickness and the width of keratinized gingiva. The percentage of root coverage achieved thereby is comparable to existing techniques. This method might contribute to an increase of patient's comfort and an enhanced aesthetical outcome.

  8. Bovine pericardium based non-cross linked collagen matrix for successful root coverage, a clinical study in human

    Science.gov (United States)

    2012-01-01

    Introduction The aim of this study was to clinically assess the capacity of a novel bovine pericardium based, non-cross linked collagen matrix in root coverage. Methods 62 gingival recessions of Miller class I or II were treated. The matrix was adapted underneath a coronal repositioned split thickness flap. Clinical values were assessed at baseline and after six months. Results The mean recession in each patient was 2.2 mm at baseline. 6 Months after surgery 86.7% of the exposed root surfaces were covered. On average 0,3 mm of recession remained. The clinical attachment level changed from 3.5 ± 1.3 mm to 1,8 ( ± 0,7) mm during the observational time period. No statistically significant difference was found in the difference of probing depth. An increase in the width of gingiva was significant. With a baseline value of 1.5 ± 0.9 mm an improvement of 2.4 ± 0.8 mm after six month could be observed. 40 out of 62 recessions were considered a thin biotype at baseline. After 6 months all 62 sites were assessed thick. Conclusions The results demonstrate the capacity of the bovine pericardium based non-cross linked collagen matrix for successful root coverage. This material was able to enhance gingival thickness and the width of keratinized gingiva. The percentage of root coverage achieved thereby is comparable to existing techniques. This method might contribute to an increase of patient's comfort and an enhanced aesthetical outcome. PMID:22390875

  9. Confocal Raman mapping of collagen cross-link and crystallinity of human dentin-enamel junction

    Science.gov (United States)

    Slimani, Amel; Nouioua, Fares; Desoutter, Alban; Levallois, Bernard; Cuisinier, Frédéric J. G.; Tassery, Hervé; Terrer, Elodie; Salehi, Hamideh

    2017-08-01

    The separation zone between enamel and dentin [dentin-enamel junction (DEJ)] with different properties in biomechanical composition has an important role in preventing crack propagation from enamel to dentin. The understanding of the chemical structure (inorganic and organic components), physical properties, and chemical composition of the human DEJ could benefit biomimetic materials in dentistry. Spatial distribution of calcium phosphate crystallinity and the collagen crosslinks near DEJ were studied using confocal Raman microscopy and calculated by different methods. To obtain collagen crosslinking, the ratio of two peaks 1660 cm-1 over 1690 cm-1 (amide I bands) is calculated. For crystallinity, the inverse full-width at half maximum of phosphate peak at 960 cm-1, and the ratio of two Raman peaks of phosphate at 960/950 cm-1 is provided. In conclusion, the study of chemical and physical properties of DEJ provides many benefits in the biomaterial field to improve the synthesis of dental materials in respect to the natural properties of human teeth. Confocal Raman microscopy as a powerful tool provides the molecular structure to identify the changes along DEJ and can be expanded for other mineralized tissues.

  10. Confocal Raman mapping of collagen cross-link and crystallinity of human dentin-enamel junction.

    Science.gov (United States)

    Slimani, Amel; Nouioua, Fares; Desoutter, Alban; Levallois, Bernard; Cuisinier, Frédéric J G; Tassery, Hervé; Terrer, Elodie; Salehi, Hamideh

    2017-08-01

    The separation zone between enamel and dentin [dentin-enamel junction (DEJ)] with different properties in biomechanical composition has an important role in preventing crack propagation from enamel to dentin. The understanding of the chemical structure (inorganic and organic components), physical properties, and chemical composition of the human DEJ could benefit biomimetic materials in dentistry. Spatial distribution of calcium phosphate crystallinity and the collagen crosslinks near DEJ were studied using confocal Raman microscopy and calculated by different methods. To obtain collagen crosslinking, the ratio of two peaks 1660  cm-1 over 1690  cm-1 (amide I bands) is calculated. For crystallinity, the inverse full-width at half maximum of phosphate peak at 960  cm-1, and the ratio of two Raman peaks of phosphate at 960/950  cm-1 is provided. In conclusion, the study of chemical and physical properties of DEJ provides many benefits in the biomaterial field to improve the synthesis of dental materials in respect to the natural properties of human teeth. Confocal Raman microscopy as a powerful tool provides the molecular structure to identify the changes along DEJ and can be expanded for other mineralized tissues. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

  11. Elevated levels of collagen cross-link residues in gingival tissues and crevicular fluid of teeth with periodontal disease.

    Science.gov (United States)

    Jepsen, Søren; Springer, Ingo N G; Buschmann, Andreas; Hedderich, Jürgen; Açil, Yahya

    2003-06-01

    Lysylpyridinoline (LP) and hydroxylysylpyridinoline (HP) are collagen cross-link residues. Lysylpyridinoline is present in most tissues, whereas LP is present mainly in mineralized tissue. Both are elevated in tissue with increased collagen resorption. The purpose of this investigation was to assess if the concentrations of LP and HP are elevated in gingiva and gingival crevicular fluid (GCF) of teeth with advanced periodontitis (AP). We investigated human gingival biopsies of healthy teeth (n = 19) and teeth with AP (n = 43) in 49 individuals. Samples of GCF from 54 teeth with AP were collected in seven patients and compared with samples from 11 patients with experimentally induced gingivitis. Levels of LP and HP were measured by HPLC and fluorescence detection. Gingival concentrations of HP but not LP around teeth with advanced periodontitis were significantly elevated compared with teeth with healthy periodontium. While significant amounts of HP and LP were measurable in the GCF of teeth with AP, no HP and LP was identified 3 months following non-surgical periodontal therapy of the teeth or in fluid from teeth subjected to experimentally induced gingivitis. Elevated concentrations of HP and LP in GCF may serve as indicators of ongoing destruction of periodontal tissues and alveolar bone in advanced periodontitis.

  12. Gum arabic modified Fe3O4 nanoparticles cross linked with collagen for isolation of bacteria

    Directory of Open Access Journals (Sweden)

    Chittor Raghuraman

    2010-12-01

    Full Text Available Abstract Background Multifunctional magnetic nanoparticles are important class of materials in the field of nanobiotechnology, as it is an emerging area of research for material science and molecular biology researchers. One of the various methods to obtain multifunctional nanomaterials, molecular functionalization by attaching organic functional groups to nanomagnetic materials is an important technique. Recently, functionalized magnetic nanoparticles have been demonstrated to be useful in isolation/detection of dangerous pathogens (bacteria/viruses for human life. Iron (Fe based material especially FePt is used in the isolation of ultralow concentrations (2 cfu/ml of bacteria in less time and it has been demonstrated that van-FePt may be used as an alternative fast detection technique with respect to conventional polymerase chain reaction (PCR method. However, still further improved demonstrations are necessary with interest to biocompatibility and green chemistry. Herein, we report the synthesis of Fe3O4 nanoparticles by template medication and its application for the detection/isolation of S. aureus bacteria. Results The reduction of anhydrous Iron chloride (FeCl3 in presence of sodium borohydride and water soluble polyelectrolyte (polydiallyldimethyl ammonium chloride, PDADMAC produces black precipitates. The X-ray diffraction (XRD, XPS and TEM analysis of the precipitates dried at 373 K demonstrated the formation of nanocrystalline Fe3O4. Moreover, scanning electron microscopy (SEM showed isolated staphylococcous aureus (S. aureus bacteria at ultralow concentrations using collagen coated gum arabic modified iron oxide nanoparticles (CCGAMION. Conclusion We are able to synthesize nanocrystalline Fe3O4 and CCGAMION was able to isolate S. aureus bacteria at 8-10 cfu (colony forming units/ml within ~3 minutes.

  13. Elevated carboxy terminal cross linked telopeptide of type I collagen in alcoholic cirrhosis: relation to liver and kidney function and bone metabolism

    DEFF Research Database (Denmark)

    Møller, S; Hansen, M; Hillingso, J

    1999-01-01

    BACKGROUND: The carboxy terminal cross linked telopeptide of type I collagen (ICTP) has been put forward as a marker of bone resorption. Patients with alcoholic liver disease may have osteodystrophy. AIMS: To assess circulating and regional concentrations of ICTP in relation to liver dysfunction...

  14. 2-YEAR EXPERIENCE OF CORNEAL COLLAGEN CROSSLINKING IN KERATOCONUS TREATMENT

    Directory of Open Access Journals (Sweden)

    D. D. Dement’ev

    2015-01-01

    Full Text Available Aim. To assess reliability, efficacy, and stability of corneal collagen crosslinking (CXL results for stage I‑II keratoconus.Patients and methods. 2‑year (2012-2014 results of CXL were analyzed. CXL was performed on 20 eyes of 15 patients (13 men and 2 women, mean age 31 years. Stage 1 keratoconus was diagnosed in 13 eyes, stage 2 keratoconus was diagnosed in 2 eyes. Primary stage 1‑2 keratoconus was diagnosed in 17 eyes, keratoconus after corneal refractive surgery (LASIK, radial keratotomy was diagnosed in 3 eyes. Preoperative and postoperative examination included uncorrected (UCVA and best-corrected (BCVA visual acuity measurement, pachymetry, corneal topography (total astigmatism measurement, and biomicroscopy. Follow-up period varied from 1 to 24 months.Results. All patients reported on vision improvement. Preoperatively, mean UCVA and BCVA were 0.4 and 0.64, respectively. Postoperatively, mean UCVA and BCVA were 0.49 and 0.66, respectively. Preoperatively and postoperatively, total astigmatism was 2.1 D and 2.0 D, respectively, while mean central corneal thickness was 454 μm and 447 μm, respectively.Conclusions. Corneal collagen crosslinking for stage 1‑2 keratoconus provides mild UCVA and BCVA improvement, decrease in total astigmatism and central corneal thickness. CXL provides stable results of treatment of primary stage 1‑2 keratoconus and keratoconus after corneal refractive surgery. 

  15. Dehydrothermally Cross-Linked Collagen Membrane with a Bone Graft Improves Bone Regeneration in a Rat Calvarial Defect Model.

    Science.gov (United States)

    An, Yin-Zhe; Heo, Young-Ku; Lee, Jung-Seok; Jung, Ui-Won; Choi, Seong-Ho

    2017-08-10

    In this study, the bone regeneration efficacy of dehydrothermally (DHT) cross-linked collagen membrane with or without a bone graft (BG) material was evaluated in a critical-sized rat model. An 8-mm-diameter defect was created in the calvaria of 40 rats, which were randomized into four groups: (1) control; (2) DHT; (3) BG; and, (4) DHT + BG. Evaluations were made at 2 and 8 weeks after surgery using micro-computed tomographic (micro-CT), histological, and histomorphometric analyses. Micro-CT analysis showed an increase in the new bone volume (NBV) of the BG and DHT + BG groups at 2 weeks after surgery, representing a significant difference (p DHT + BG groups, and a significant difference was no longer observed between the two groups. Histologic analysis demonstrated that the graft materials sustained the center of the defect in the BG and DHT + BG groups, which was shown in histomorphometric analysis as well. These results suggest that DHT membrane is a safe biomaterial with adequate tissue integration, and has a positive effect on new bone formation. Moreover, the best effects were achieved when DHT was used in conjunction with BG materials.

  16. Serum cross-linked n-telopeptides of type 1 collagen (NTx in patients with solid tumors

    Directory of Open Access Journals (Sweden)

    Fernando Jablonka

    Full Text Available CONTEXT AND OBJECTIVE: Cross-linked N-telopeptides of type I collagen (NTx increase in concentration in situations in which bone resorption is increased, such as osteoporosis and bone metastasis (BM. We aimed to evaluate the serum concentrations of NTx in a sample of patients with several types of solid tumors. DESIGN AND SETTING: Cross-sectional analytical study with a control group in a tertiary public hospital. METHODS: We performed the quantitative enzyme-linked immunosorbent assay (ELISA on serum NTx levels in 19 subjects without a history of cancer and 62 patients with various solid tumors who had been referred for a bone scan. Three experienced analysts read all bone scans. RESULTS: The serum NTx levels in patients with cancer and BM, with cancer but without BM and without cancer were 46.77 ± 2.58, 32.85 ± 2.05 and 22.32 ± 2.90 respectively (P < 0.0001. We did not find any significant correlations of serum NTx with age, gender, history of bone pain, tumor type and bone alkaline phosphatase levels. We found a significant correlation between serum NTx and alkaline phosphatase levels (R² = 0.08; P = 0.022. CONCLUSIONS: Serum NTx levels are significantly higher in patients with solid tumors and bone metastases than they are in patients without bone metastases and in normal controls.

  17. The structural and optical properties of type III human collagen biosynthetic corneal substitutes

    Science.gov (United States)

    Hayes, Sally; Lewis, Phillip; Islam, M. Mirazul; Doutch, James; Sorensen, Thomas; White, Tomas; Griffith, May; Meek, Keith M.

    2015-01-01

    The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2–9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants. PMID:26159106

  18. Preparation of guar gum scaffold film grafted with ethylenediamine and fish scale collagen, cross-linked with ceftazidime for wound healing application.

    Science.gov (United States)

    Jana, Piyali; Mitra, Tapas; Selvaraj, Thirupathi Kumara Raja; Gnanamani, A; Kundu, P P

    2016-11-20

    Present study describes the synthesis of carboxymethyl guar gum (CMGG) from the native guar gum (GG) and the prepared CMGG is grafted with ethylenediamine (EDA) to form aminated CMGG. Then, fish scale collagen and aminated CMGG are cross-linked by ceftazidime drug through non- covalent ionic interaction. The resultant cross-linked film is subjected to the analysis of (1)HNMR, ATR-FTIR, TGA, SEM and XRD. The TNBS results revealed that 45% of interaction between EDA and CMGG and 90-95% of Ceftazidime is released from aminated CMGG-Ceftazidime-Collagen (ACCC) film after 96h of incubation at physiological pH. In vitro cell line studies reveal the biocompatibility of the cross-linked film and the antimicrobial studies display the growth inhibition against Staphylococcus aureus and Pseudomonas aeruginosa organisms. Overall, the study indicates that the incorporation of Ceftazidime into collagen and aminated CMGG can improve the functional property of aminated CMGG as well as collagen, leading to its biomedical applications.

  19. Investigations on the effects of growth rate and dietary vitamin C on skeletal muscle collagen and hydroxylysyl pyridinoline cross-link concentration in farmed Atlantic salmon (Salmo salar).

    Science.gov (United States)

    Li, Xuejun; Bickerdike, Ralph; Nickell, David; Campbell, Patrick; Dingwall, Alistair; Johnston, Ian A

    2007-01-24

    We have investigated the interactions between dietary vitamin C levels (at 33, 79, 135, and 424 mg kg-1 of wet mass feed) and growth rate on the collagen and cross-link contents of fast muscle in farmed juvenile Atlantic salmon (Salmo salar L.). The growth rate was measured over an 11 week period using the thermal growth coefficient (TGC). Alkaline-soluble (0.1 M NaOH) (a-s) hydroxyproline (HYP) and alkaline-insoluble (i-s) HYP were determined as a measure of collagen content and hydroxylysyl pyridinoline (PYD) as a measure of mature collagen cross-link concentration. There was a approximately 5-fold increase in muscle vitamin C concentration at similar feed conversion ratios ( approximately 0.82) as dietary vitamin C levels increased from 39 to 424 mg kg-1 of wet mass feed. However, even the lowest dietary vitamin C was sufficient for normal skeletal development and growth. The lowest dietary vitamin C level tested resulted in a approximately 27% decrease in the a-sHYP concentration relative to the other diets, whereas there was no significant effect of vitamin C on the i-sHYP and PYD concentrations. ANOVA revealed no significant interaction between vitamin C and growth rate, whereas the covariate TGC was significant for i-sHYP and PYD but not for a-sHYP. Pyridinoline cross-link and i-s HYP concentrations were 11.1 and 7.7% lower, respectively, in high (TGC > 3.9) mass than low (TGC salmon reared under controlled growth conditions, the dietary vitamin C inclusion of 79 mg kg-1 of wet mass feed was sufficient to produce the required synthesis of soluble muscle collagen. Furthermore, post-translational modifications of the collagen leading to cross-linking showed a small decrease with increasing growth rate but was independent of vitamin C concentration in the diet at these levels.

  20. Influence on the physicochemical properties of fish collagen gels using self-assembly and simultaneous cross-linking with the N-hydroxysuccinimide adipic acid derivative.

    Science.gov (United States)

    Shen, Lirui; Tian, Zhenhua; Liu, Wentao; Li, Guoying

    2015-06-01

    Collagen gels from Southern catfish (Silurus meridionalis Chen) skins were prepared via the self-assembly of collagen molecules and simultaneous cross-linking with the N-hydroxysuccinimide adipic acid derivative (NHS-AA). The doses of NHS-AA were converted to [NHS-AA]/[NH2] ratios (0.025-1.6, calculated by the [active ester group] of NHS-AA and [ε-NH2] of lysine and hydroxylysine residues of collagen). When the ratio collagen gels were formed by collagen molecule self-assembly, resulting in the opalescent appearance of collagen gels and the characteristic D-periodicity of partial collagen fibrils, the collagen gel ([NHS-AA]/[NH2] = 0.05) displayed a small increase in denaturation temperature (Td, 42.8 °C), remaining weight (12.59%), specific water content (SWC 233.7) and elastic modulus (G' 128.4 Pa) compared with uncross-linked collagen gel (39.1 °C, 9.12%, 222.4 and 85.4 Pa, respectively). As the ratio > 0.05, disappearance of D-periodicity and a gradual change in appearance from opalescent to transparent suggested that the inhibition of NHS-AA in the self-assembly of collagen molecules was more obvious. As a result, the collagen gel ([NHS-AA]/[NH2] = 0.2) had the lowest Td (35.8 °C), remaining weight (7.96%), SWC (130.9) and G' (31.9 Pa). When the ratio was 1.6, the collagen molecule self-assembly was markedly suppressed and the formation of collagen gel was predominantly via the covalent cross-linking bonds which led to the transparent appearance, and the maximum values of Td (47.0 °C), remaining weight (45.92%) and G' (420.7 Pa) of collagen gel. These results indicated that collagen gels with different properties can be prepared using different NHS-AA doses.

  1. Pyridinium cross-links in bone of patients with osteogenesis imperfecta: Evidence of a normal intrafibrillar collagen packing

    NARCIS (Netherlands)

    Bank, R.A.; Tekoppele, J.M.; Janus, G.J.M.; Wassen, M.H.M.; Pruijs, H.E.H.; Sluijs, H.A.H. van der; Sakkers, R.J.B.

    2000-01-01

    The brittleness of bone in patients with osteogenesis imperfecta (OI) has been attributed to an aberrant collagen network. However, the role of collagen in the loss of tissue integrity has not been well established. To gain an insight into the biochemistry and structure of the collagen network, the

  2. Dose-dependent collagen cross-linking of rabbit scleral tissue by blue light and riboflavin treatment probed by dynamic shear rheology.

    Science.gov (United States)

    Schuldt, Carsten; Karl, Anett; Körber, Nicole; Koch, Christian; Liu, Qing; Fritsch, Anatol W; Reichenbach, Andreas; Wiedemann, Peter; Käs, Josef A; Francke, Mike; Iseli, Hans Peter

    2015-08-01

    To determine the visco-elastic properties of isolated rabbit scleral tissue and dose-dependent biomechanical and morphological changes after collagen cross-linking by riboflavin/blue light treatment. Scleral patches from 87 adult albino rabbit eyes were examined by dynamic shear rheology. Scleral patches were treated by riboflavin and different intensities of blue light (450 nm), and the impact on the visco-elastic properties was determined by various rheological test regimes. The relative elastic modulus was calculated from non-treated and corresponding treated scleral patches, and treatments with different blue light intensities were compared. Shear rheology enables us to study the material properties of scleral tissue within physiological relevant parameters. Cross-linking treatment increased the viscous as well as the elastic modulus and changed the ratio of the elastic versus viscous proportion in scleral tissue. Constant riboflavin application combined with different blue light intensities from 12 mW/cm(2) up to 100 mW/cm(2) increased the relative elastic modulus of scleral tissue by factors up to 1.8. Further enhancement of the applied light intensity caused a decline of the relative elastic modulus. This might be due to destructive changes of the collagen bundle structure at larger light intensities, as observed by histological examination. Collagen cross-linking by riboflavin/blue light application increases the biomechanical stiffness of the sclera in a dose-dependent manner up to certain light intensities. Therefore, this treatment might be a suitable therapeutic approach to stabilize the biomechanical properties of scleral tissue in cases of pathological eye expansion. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  3. Role of protein kinase C signaling in collagen degradation by rabbit corneal fibroblasts cultured in three-dimensional collagen gels.

    Science.gov (United States)

    Nagano, Takashi; Hao, Ji-Long; Nakamura, Masatsugu; Nishida, Teruo

    2002-08-01

    To understand the mechanism of corneal ulceration by characterizing the intracellular signaling pathways that regulate collagen degradation by corneal fibroblasts cultured in three-dimensional type I collagen gels. Specifically, the potential roles of protein kinase C (PKC) and protein kinase A (PKA) in collagen degradation were investigated. Rabbit corneal fibroblasts were cultured in three-dimensional type I collagen gels for 24 hours in the presence of plasminogen and in the absence or presence of activators or inhibitors of PKC or PKA. Degradation of collagen fibrils was then evaluated by measurement of released hydroxyproline, and the production of matrix metalloproteinases (MMPs) was assessed by gelatin zymography and immunoblot analysis. The PKC activator phorbol 12-myristate 13-acetate (PMA) increased the extent of collagen degradation by corneal fibroblasts in a dose-dependent manner, with the maximal effect apparent at a concentration of 0.1 microM. The inactive analog 4alpha-PMA had no effect on collagen degradation. The PKC inhibitor H-7 reduced the extent of collagen degradation by corneal fibroblasts in the absence or presence of PMA. Phorbol 12-myristate 13-acetate also increased the production of proMMP-1, -3, and -9 by corneal fibroblasts, whereas H-7 inhibited this effect. Neither the PKA activators 8-bromo-cAMP, isobutylmethylxanthine, and forskolin nor the PKA inhibitor HA1004 affected collagen degradation by corneal fibroblasts. These results demonstrate that PKC plays an important role in collagen degradation by corneal fibroblasts in three-dimensional type I collagen gels, whereas PKA does not appear to participate in this process.

  4. Ultra B2 - Promoção de ligações covalentes do colágeno corneal (Corneal cross-linking no tratamento de ceratocone: resultados preliminares Corneal Cross-linking for the treatment of keratoconus: preliminary results

    Directory of Open Access Journals (Sweden)

    Mirko R. Jankov II

    2008-12-01

    atingir diferença estatisticamente significante. Nenhum dos olhos perdeu linha de BSCVA, 12 mantiveram o BSCVA pré-operatório, 7 ganharam uma linha, 5 ganharam duas e 1 paciente ganhou três linhas de BSCVA. CONCLUSÕES: O tratamento com Ultra-B2 mostrou-se seguro (não apresentou perda de linha de visão corrigida e eficaz (manteve os parâmetros anatômicos e ópticos em estacionar a progressão da ectasia corneal. Houve redução, embora sem significância estatística, da curvatura corneal máxima, equivalente esférico e cilindro refrativo nos olhos com a córnea instável devida ao ceratocone.PURPOSE: To present early visual and keratometric results for corneal cross-linking with riboflavin and UV irradiation in patients with progressive keratoconus. METHODS: Twenty-five eyes of twenty patients (15 males and 5 females with a progressive keratoconus in the previous 6 months were followed. Unaided visual acuity (UVA, best spectacle corrected visual acuity (BSCVA, spherical equivalent (SEQ, manifest cylinder, and maximal corneal curvature (max K values were followed at 1, 3 and 6 months. All patients were submitted to corneal cross-linking using riboflavin (vitamin B2 as the photosensitizer and ultraviolet light (UV, wavelength 370 nm. Epithelium was removed with 20% alcohol, cornea was soaked with vitamin B2 for 15 min, and then irradiated with UV light for 30 min, after which a bandage contact lens (BCL was placed. RESULTS: UVA increased after one month (from 0.15 ± 0.15 to 0.23 ± 0.20, and went on increasing at 3 and 6 months, reaching statistical significance (p=0.025 e p=0.037, respectively. BSCVA increased from 0.41 ± 0.27 to 0.49 ± 0.29 at month six, without reaching statistical significance at any time point. Progression of keratoconus stopped in all patients, in contrast with progression in all of them in the six-month period prior to the surgery. Max K decreased by more than 2 D (from 53.02 ± 8.42 to 50.88 ± 6.05 D, SEQ less that 1 D (from -3.27 ± 4

  5. Corneal collagen crosslinking in keratoconus and other eye disease

    Institute of Scientific and Technical Information of China (English)

    Adel; Alhayek; Pei-Rong; Lu

    2015-01-01

    Keratoconus is a condition characterized by biomechanical instability of the cornea, presenting in a progressive, asymmetric and bilateral way. Corneal collagen crosslinking(CXL) with riboflavin and Ultraviolet-A(UVA) is a new technique of corneal tissue strengthening that combines the use of riboflavin as a photo sensitizer and UVA irradiation. Studies showed that CXL was effective in halting the progression of keratoconus over a period of up to four years. The published studies also revealed a reduction of max K readings by more than 2 D, while the postoperative spherical equivalent(SEQ) was reduced by an average of more than 1 D and refractive cylinder decreased by about1 D. The major indication for the use of CXL is to inhibit the progression of corneal ecstasies, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photo ablation. This treatment has been used to treat infectious corneal ulcers with apparent favorable results. Most recent studies demonstrate the beneficial impact of CXL for iatrogenic ecstasies, pellucid marginal degeneration, infectious keratitis, bullous keratopathy and ulcerative keratitis. Several long-term and short-term complications of CXL have been studied and documented. The possibility of a secondary infection after the procedure exists because the patient is subject to epithelial debridement and the application of a soft contact lens. Formation of temporary corneal haze,permanent scars, endothelial damage, treatment failure,sterile infiltrates, bullous keratopathy and herpes reactivation are the other reported complications of this procedure.

  6. Collagen structure regulates fibril mineralization in osteogenesis as revealed by cross-link patterns in calcifying callus

    NARCIS (Netherlands)

    Wassen, M.H.M.; Lammens, J.; Tekoppele, J.M.; Sakkers, R.J.B.; Liu, Z.; Verbout, A.J.; Bank, R.A.

    2000-01-01

    Although >80% of the mineral in mammalian bone is present in the collagen fibrils, limited information is available about factors that determine a proper deposition of mineral. This study investigates whether a specific collagen matrix is required for fibril mineralization. Calcifying callus from do

  7. Photo-cross-linking of amniotic membranes for limbal epithelial cell cultivation

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Jui-Yang, E-mail: jylai@mail.cgu.edu.tw

    2014-12-01

    In the present study, we developed photo-cross-linked amniotic membrane (AM) as a limbal stem cell niche. After ultraviolet (UV) irradiation for varying time periods, the biological tissues were studied by determinations of cross-linking structure, degradability, and nutrient permeation ability. Our results showed that the number of cross-links per unit mass of AM significantly increased with increasing illumination time from 5 to 50 min. However, the cross-link formation was inhibited by longer irradiation time (i.e., 150 min), probably due to the scission of tissue collagen chains through irradiation. The biological stability and matrix permeability of photo-cross-linked AM materials strongly depended on their cross-linking densities affected by the UV irradiation. In vitro biocompatibility studies including cell viability and pro-inflammatory gene expression analyses demonstrated that, irrespective of the irradiation time employed, the physically cross-linked biological tissues exhibited negligible cytotoxicity and similar interleukin-6 (IL-6) mRNA levels. The data clearly indicate that these AM matrices do not cause potential harm to the corneal epithelial cells. After the growth of limbal epithelial cells (LECs) on AM substrates, Western blot analyses were conducted to examine the expression of ABCG2. It was found that the ability of UV-irradiated AM to maintain the undifferentiated precursor cell phenotype was significantly enhanced with increasing extent of photo-cross-linking. In summary, the UV irradiation time may have a profound influence on the fabrication of photo-cross-linked AM matrices for LEC cultivation. - Highlights: • We report the development of photo-cross-linked AM as a limbal stem cell niche. • Cross-linked structure of tissue materials was controlled by UV irradiation time. • Biostability and matrix permeability of AM depended on cross-linking density. • All the studied photo-cross-linked AM showed good in vitro biocompatibility.

  8. Treatment of chest burn contracture causing respiratory compromise with island release and grafting using cross-link collagen and Integra™ bilayer dressing

    Directory of Open Access Journals (Sweden)

    Neil Doctor

    2014-04-01

    Full Text Available Post-burn skin contractures of the anterior and lateral abdomen and chest may result in respiratory compromise due to limitation of rib excursion. This case report describes a young man with respiratory compromise limiting his daily activity and function, as a result of a 90% burn sustained 6 years previously. Release of his chest and upper abdomen was achieved using “island” scar releases and a cross-linked bovine tendon collagen and glycosaminoglycan and a semi-permeable polysiloxane bilayer matrix dressing (Integra™ followed by subsequent split thickness skin graft. An immediate increase in maximal inspiratory volume was obtained intra-operatively and in the im­mediate post-operative period, and this improvement was sustained after healing of all wounds with subjective relief of the patient’s symptoms.

  9. Non-cross-linked collagen type I/III materials enhance cell proliferation: in vitro and in vivo evidence

    Directory of Open Access Journals (Sweden)

    Ines WILLERSHAUSEN

    2014-01-01

    Full Text Available Objective: To analyze Mucograft®(MG, a recently introduced collagen matrix, in vitro and in vivo, and compare it with BioGide®(BG, a well-established collagen membrane, as control. Material and Methods: A detailed analysis of the materials surface and ultra-structure was performed. Cellular growth patterns and proliferation rates of human fibroblasts on MG and BG were analyzed in vitro. In addition, the early tissue reaction of CD-1 mouse to these materials was analyzed by means of histological and histomorphometrical analysis. Results: MG showed a three-fold higher thickness both in dry and wet conditions, when compared to BG. The spongy surface of BG significantly differed from that of MG. Cells showed a characteristic proliferation pattern on the different materials in vitro. Fibroblasts tended to proliferate on the compact layers of both collagens, with the highest values on the compact side of BG. In vivo, at day three both materials demonstrated good tissue integration, with a mononuclear cell sheet of fibroblasts on all surfaces, however, without penetrating into the materials. Conclusions: The findings of this study showed that MG and BG facilitate cell proliferation on both of their surfaces in vitro. In vivo, these two materials induce a comparable early tissue reaction, while serving as cell occlusive barriers.

  10. Review of current indications for combined very high fluence collagen cross-linking and laser in situ keratomileusis surgery

    Directory of Open Access Journals (Sweden)

    Anastasios John Kanellopoulos

    2013-01-01

    Full Text Available In this brief review we will discuss the reasoning and evolution of our current use of combined very high-fluence collagen crosslinking and laser in situ keratomileusis. Several presentations and pertinent publications are reviewed, along with the key steps of the enhanced LASIK procedure. Long term outcome data support the safety and efficacy of LASIK Xtra in stabilizing myopic but also hyperopic LASIK results.In conclusion, we have compelling evidence that LASIK Xtra is a safe and effective adjunct.

  11. Inhibition by medroxyprogesterone acetate of interleukin-1β-induced collagen degradation by corneal fibroblasts.

    Science.gov (United States)

    Zhou, Hongyan; Kimura, Kazuhiro; Orita, Tomoko; Nishida, Teruo; Sonoda, Koh-Hei

    2012-06-28

    To examine the effect of medroxyprogesterone 17-acetate (MPA) on interleukin-1β (IL-1β)-induced collagen degradation by corneal fibroblasts. Rabbit corneal fibroblasts were cultured in three-dimensional collagen gels with or without MPA. Collagen degradation was determined by measurement of hydroxyproline after acid hydrolysis. The expression or activity of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) was evaluated by immunoblot analysis or gelatin zymography. The phosphorylation of mitogen-activated protein kinases (MAPKs) in corneal fibroblasts was examined by immunoblot analysis. Cell proliferation and viability were evaluated by measurement of bromodeoxyuridine incorporation and the release of lactate dehydrogenase, respectively. MPA inhibited IL-1β-induced collagen degradation by corneal fibroblasts in a concentration- and time-dependent manner. MMP expression and activation as well as TIMP expression in corneal fibroblasts exposed to IL-1β were also inhibited by MPA. MPA had no effect on cell proliferation or viability. MPA inhibited the IL-1β-induced phosphorylation of p38 MAPK without affecting that of the MAPKs ERK or JNK. IL-1β-induced MMP expression and activation as well as collagen degradation were also blocked by the p38 MAPK inhibitor SB203580. MPA inhibited MMP expression and thereby suppressed collagen degradation by corneal fibroblasts induced by IL-1β. Furthermore, inhibition of p38 MAPK phosphorylation by MPA may contribute to its inhibition of collagen degradation.

  12. Investigation the Porous Collagen-Chitosan /Glycosaminoglycans for Corneal Cell Culture as Tissue Engineering Scaffold

    Institute of Scientific and Technical Information of China (English)

    LI Qin-Hua; CHEN Jian-Su

    2005-01-01

    The objective of this study was to produce the porous collagen-chitosan/Glycosanminglycans (GAG) for corneal ceil-seed implant as a three-dimensional tissue engineering scaffold to improve the regeneration corneas. The effect of various content of glycerol as form porous agent to collagen-chitosan/GAG preserved a porous dimensional structure was investigated. The heat-drying was used to prepare porous collagen-chitosan /GAG scaffold. The pore morphology of collagenchitosan/GAG was controlled by changing the concentration of glycerol solution and drying methods. The porous structure morphology was observed by SEM. The diameter of the pores form 10 to 50 μm. The highly porous scaffold had interconnecting pores. The corneal cell morphology was observed under the light microscope. These results suggest that collagen-chitosan/GAG showed that corneal cell have formed confluent layers and resemble the surface of normal corneal cell surface.

  13. Inhibition by female sex hormones of collagen degradation by corneal fibroblasts.

    Science.gov (United States)

    Zhou, Hongyan; Kimura, Kazuhiro; Orita, Tomoko; Nishida, Teruo; Sonoda, Koh-Hei

    2011-01-01

    Corneal fibroblasts contribute to collagen remodeling in the corneal stroma in part by mediating collagen degradation. Given that corneal structure is influenced by sex hormone status, we examined the effects of sex hormones on collagen degradation by corneal fibroblasts. Rabbit corneal fibroblasts were cultured in three-dimensional collagen gels with or without sex hormones including 17β-estradiol, progesterone, testosterone, and dehydroepiandrosterone (DHEA). Collagen degradation was determined by measurement of hydroxyproline after acid hydrolysis. The expression and activity of matrix metalloproteinases (MMPs) were evaluated by immunoblot analysis and gelatin zymography. The phosphorylation of mitogen-activated protein kinases (MAPKs) and the nuclear factor-kappa B (NF-κB) inhibitor NF kappa B Inhibitor-alpha (IκB-α) in corneal fibroblasts was examined by immunoblot analysis. Cell proliferation and viability were evaluated by measurement of bromodeoxyuridine incorporation and the release of lactate dehydrogenase, respectively. 17β-Estradiol and progesterone each inhibited interleukin (IL)-1β-induced collagen degradation by corneal fibroblasts in a concentration-dependent manner, whereas testosterone and DHEA had no such effect. MMP expression and activation in corneal fibroblasts exposed to IL-1β were also inhibited by 17β-estradiol and progesterone. These female sex hormones did not affect cell proliferation or viability. Both 17β-estradiol and progesterone inhibited the IL-1β-induced phosphorylation of p38 MAPK without affecting that of the MAPKs extracellular Signal-regulated Kinase (ERK) or c-jun N-terminal kinase (JNK). 17β-Estradiol also inhibited the IL-1β-induced phosphorylation of IκB-α. 17β-Estradiol and progesterone inhibited MMP expression and activity in IL-1β-stimulated corneal fibroblasts and thereby suppressed collagen degradation by these cells.

  14. Femtosecond Corneal Collagen Crosslinking in Treatment of Patients with Progressive Keratoconus Stages I–II

    OpenAIRE

    K.B. Letnikova; A.T. Khandjan; O.G. Oganesyan; A.V. Penkina; V.V. Neroyev

    2016-01-01

    The aim of the investigation was to assess safety and efficacy of corneal collagen crosslinking technique using femtosecond laser for intrastromal pocket creation in patients with progressive keratoconus. Materials and Methods. Thirty-three patients (34 eyes) with progressive keratoconus stages I–II underwent femto-crosslinking of the corneal collagen. FEMTO LDV Z6 femtosecond laser was used to create an intrastromal pocket of 8.0 mm diameter and 140 μm depth. Normotonic riboflavin solution (...

  15. HPLC detection of loss rate and cell migration of HUVECs in a proanthocyanidin cross-linked recombinant human collagen-peptide (RHC)–chitosan scaffold

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jing; Deng, Aipeng [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Yang, Yang [Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Gao, Lihu; Xu, Na; Liu, Xin; Hu, Lunxiang; Chen, Junhua [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Yang, Shulin, E-mail: yshulin@njust.edu.cn [School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2015-11-01

    Porous scaffolds with appropriate pore structure, biocompatibility, mechanical property and processability play an important role in tissue engineering. In this paper, we fabricated a recombinant human collagen-peptide (RHC)–chitosan scaffold cross-linked by premixing 30% proanthocyanidin (PA) in one-step freeze-drying. To remove the residual acetic acid, optimized 0.2 M phosphate buffer of pH 6.24 with 30% ethanol (PBSE) was selected to neutralize the lyophilized scaffold followed by three times deionized water rinse. Ninhydrin assay was used to characterize the components loss during the fabrication process. To detect the exact RHC loss under optimized neutralization condition, high performance liquid chromatography (HPLC) equipped size exclusion chromatography column was used and the total RHC loss rate through PBSE rinse was 19.5 ± 5.08%. Fourier transform infrared spectroscopy (FT-IR) indicated hydrogen bonding among RHC, chitosan and PA, it also presented a probative but not strong hydrophobic interaction between phenyl rings of polyphenols and pyrrolidine rings of proline in RHC. Further, human umbilical vein endothelial cell (HUVEC) viability analyzed by a scanning electron microscope (SEM) and acridine orange/ethidium bromide (AO/EB) fluorescence staining exhibited that this scaffold could not only promote cell proliferation on scaffold surface but also permit cells migration into the scaffold. qRT-PCR exhibited that the optimized scaffold could stimulate angiogenesis associated genes VEGF and CD31 expression. These characterizations indicated that this scaffold can be considered as an ideal candidate for tissue engineering. - Highlights: • PA cross-linked recombinant human collagen–chitosan scaffold. • Fabrication in one-step lyophilization with neutralization. • HPLC detection of RHC loss rate • HUVEC proliferation and migration in scaffold • Angiogenesis associated gene expressions were increased in scaffold cell culturing.

  16. Visual rehabilitation in low-moderate keratoconus:intracorneal ring segment implantation followed by same-day topography-guided photorefractive keratectomy and collagen cross linking

    Institute of Scientific and Technical Information of China (English)

    Ferial; M.Zeraid; Asma; A; Jawkhab; Waleed; S; Al-Tuwairqi; Uchechukwu; L.Osuagwu

    2014-01-01

    AIM:To present the results of same-day topographyguided photorefractive keratectomy(TG-PRK) and corneal collagen crosslinking(CXL) after previous intrastromal corneal ring segment(ISCR) implantation for keratoconus.METHODS:An experimental clinical study on twentyone eyes of 19 patients aged 27.1±6.6y(range 19-43y),with low to moderate keratoconus who were selected to undergo customized TG-PRK immediately followed by same-day CXL, 9mo after ISCR implantation in a university ophthalmology clinic. Refraction, uncorrected distance visual acuities(UDVA) and corrected distance visual acuities(CDVA), keratometry(K) values, central corneal thickness(CCT) and coma were assessed 3mo after TG-PRK and CXL.RESULTS:After TG-PRK/CXL: the mean UDVA(logMAR) improved significantly from 0.66 ±0.41 to 0.20 ±0.25(P <0.05); Kflatvalue decreased from: 48.44±3.66 D to43.71±1.95 D; Ksteepvalue decreased from 45.61±2.40 D to41.56±2.05 D; Kaveragealso decreased from 47.00±2.66 D to42.42 ±2.07 D(P <0.05 for all). The mean sphere andcylinder decreased significantly post- surgery from,- 3. 10 ± 2. 99 D to-0.11±0.93 D and from-3.68±1.53 to-1.11 ±0.75 D respectively, while the CDVA, CCT and coma showed no significant changes. Compared to postISCR, significant reductions(P <0.05 or all) in all K values,sphere and cylinder were observed after TG-PRK/CXL.CONCLUSION:Same-day combined topography-guided PRK and corneal crosslinking following placement of ISCR is a safe and potentially effective option in treating low-moderate keratoconus. It significantly improves all visual acuity, reduced keratometry, sphere and astigmatism, but causes no change in central corneal thickness and coma.

  17. Inhibition by all-trans retinoic acid of collagen degradation mediated by corneal fibroblasts.

    Science.gov (United States)

    Kimura, Kazuhiro; Zhou, Hongyan; Orita, Tomoko; Kobayashi, Shinya; Wada, Tomoyuki; Nakamura, Yoshikuni; Nishida, Teruo; Sonoda, Koh-Hei

    2016-08-01

    We examined the effect of all-trans retinoic acid on collagen degradation mediated by corneal fibroblasts. Rabbit corneal fibroblasts were cultured with or without all-trans retinoic acid in a three-dimensional collagen gel, and the extent of collagen degradation was determined by measurement of hydroxyproline in acid hydrolysates of culture supernatants. Matrix metalloproteinase expression was examined by immunoblot analysis and gelatin zymography. The abundance and phosphorylation state of the endogenous nuclear factor-kappaB inhibitor IκB-α were examined by immunoblot analysis. Corneal ulceration was induced by injection of lipopolysaccharide into the central corneal stroma of rabbits and was assessed by observation with a slitlamp microscope. All-trans retinoic acid inhibited interleukin-1β-induced collagen degradation by corneal fibroblasts in a concentration- and time-dependent manner. It also attenuated the release and activation of matrix metalloproteinases as well as the phosphorylation and degradation of IκB-α induced by interleukin-1β in these cells. Topical application of all-trans retinoic acid suppressed corneal ulceration induced by injection of lipopolysaccharide into the corneal stroma. All-trans retinoic acid inhibited collagen degradation mediated by corneal fibroblasts exposed to interleukin-1β, with this effect being accompanied by suppression of nuclear factor-kappaB signalling as well as of matrix metalloproteinase release and activation in these cells. All-trans retinoic acid also attenuated lipopolysaccharide-induced corneal ulceration in vivo. Our results therefore suggest that all-trans retinoic acid might prove effective for the treatment of patients with corneal ulceration. © 2016 Royal Australian and New Zealand College of Ophthalmologists.

  18. The effect of cross-link distributions in axially-ordered, cross-linked networks

    Science.gov (United States)

    Bennett, C. Brad; Kruczek, James; Rabson, D. A.; Matthews, W. Garrett; Pandit, Sagar A.

    2013-07-01

    Cross-linking between the constituent chains of biopolymers has a marked effect on their materials’ properties. In certain of these materials, such as fibrillar collagen, increases in cross-linking lead to an increase in the melting temperature. Fibrillar collagen is an axially-ordered network of cross-linked polymer chains exhibiting a broadened denaturation transition, which has been explained in terms of the successive denaturation with temperature of multiple species. We model axially-ordered, cross-linked materials as stiff chains with distinct arrangements of cross-link-forming sites. Simulations suggest that systems composed of chains with identical arrangements of cross-link-forming sites exhibit critical behavior. In contrast, systems composed of non-identical chains undergo a crossover. This model suggests that the arrangement of cross-link-forming sites may contribute to the broadening of the denaturation transition in fibrillar collagen.

  19. Betanin reduces the accumulation and cross-links of collagen in high-fructose-fed rat heart through inhibiting non-enzymatic glycation.

    Science.gov (United States)

    Han, Junyan; Tan, Chang; Wang, Yiheng; Yang, Shaobin; Tan, Dehong

    2015-02-05

    We attempted to determine whether betanin (from natural pigments) that has antioxidant properties would be protective against fructose-induced diabetic cardiac fibrosis in Sprague-Dawley rats. Fructose water solution (30%) was accessed freely, and betanin (25 and 100 mg/kg/d) was administered by intra-gastric gavage continuously for 60 d. Rats were sacrificed after overnight fast. The rat blood and left ventricle were collected. In vitro antiglycation assay in bovine serum albumin/fructose system was also performed. In rats treated only with fructose, levels of plasma markers: glucose, insulin, HOMA and glycated hemoglobin rised, left ventricle collagen accumulated and cross-linked, profibrotic factor-transforming growth factor (TGF)-β1 and connective tissue growth factor (CTGF) protein expression increased, and soluble collagen decreased, compared with those in normal rats, showing fructose induces diabetic cardiac fibrosis. Treatment with betanin antagonized the changes of these parameters, demonstrating the antifibrotic role of betanin in the selected diabetic models. In further mechanistic study, betanin decreased protein glycation indicated by the decreased levels of protein glycation reactive intermediate (methylglyoxal), advanced glycation end product (N(ε)-(carboxymethyl) lysine) and receptors for advanced glycation end products (AGEs), antagonized oxidative stress and nuclear factor-κB activation elicited by fructose feeding, suggesting inhibition of glycation, oxidative stress and nuclear factor-κB activation may be involved in the antifibrotic mechanisms. Betanin also showed anitglycative effect in BSA/fructose system, which supported that anitglycation was involved in betanin's protective roles in vivo. Taken together, the potential for using betanin as an auxillary therapy for diabetic cardiomyopathy deserves to be explored further.

  20. Urinary excretion of type I collagen cross-linked N-telopeptides, bone mass and related lifestyle in middle-aged women.

    Directory of Open Access Journals (Sweden)

    Masatomi C

    1999-06-01

    Full Text Available The relationship between past and present lifestyle and urinary excretion of type I collagen cross-linked N-telopeptides (NTx was studied in 61 Japanese females aged 34-59, with a view toward using NTx excretion rates as a predictor of future osteoporosis. Bone mineral density (BMD of the lumbar spine, the speed of sound (SOS and broadband ultrasound attenuation (BUA of the os calcis, urinary NTx, serum osteocalcin (BGP and bone-specific alkaline phosphatase (BAP were measured. Stiffness index (stiffness was calculated from SOS and BUA. The subjects were asked whether they took regular exercise in their childhood and teen years (in elementary, junior-high, senior-high school and college, the past (20-40 years of age and present adulthood. Regular calcium intake, smoking habits, alcohol and other beverage consumption and milk consumption were also covered in the questionnaire. The mean NTx values of premenopausal and postmenopausal group were 22.2 and 56.0 nM bone collagen equivalents (BCE/mM urinary creatinine (Cr, respectively. The group which did not exercise regularly between the ages of 20 and 40 had a higher mean NTx value (40.9 nMBCE/mMCr than the group which did exercise regularly (22.7 nMBCE/mMCr. In multiple regression analyses, age, stiffness and exercise in past adulthood could explain 43.5% of the NTx variance. For prevention of bone metabolic increases around menopause, habitual exercise in early adulthood seems to be effective.

  1. The Effects of Scleral Collagen Cross-Linking Using Glyceraldehyde on the Progression of Form-Deprived Myopia in Guinea Pigs.

    Science.gov (United States)

    Chu, Yanhua; Cheng, Zhaohui; Liu, Jing; Wang, Ying; Guo, Haixia; Han, Quanhong

    2016-01-01

    To investigate the effects of collagen cross-linking using glyceraldehyde on the biomechanical properties of the sclera and the axial elongation of form-deprived myopia in the guinea pig. Thirty-six guinea pigs were randomly assigned to four groups: FDM (form-deprived myopia); FDMG (form-deprived myopia treated with glyceraldehyde); FDMS (form-deprived myopia treated with 0.9% isotonic sodium chloride); and normal control (free of form-deprivation). FDM was achieved in the right eye using a latex facemask. The right eye in FDMG was treated with a posterior subtenon injection of 0.5 M glyceraldehyde; 0.9% isotonic sodium chloride was administered to the right eye in FDMS group using the same method. Axial length, refraction, and stress-strain of the sclera were measured at scheduled time points. The treated eyes were also examined histologically by light microscopy. It was found that glyceraldehyde treatment significantly increased the stiffness of the sclera in the FDM eyes and abnormalities have not been observed in the retina and optic nerve of the treated eyes. But the development of myopia was not affected.

  2. Serum Bone Resorption Markers after Parathyroidectomy for Renal Hyperparathyroidism: Correlation Analyses for the Cross-Linked N-telopeptide of Collagen I and Tartrate-Resistant Acid Phosphatase

    Directory of Open Access Journals (Sweden)

    Kuo-Chin Hung

    2012-01-01

    Full Text Available Patients on long-term dialysis may develop secondary hyperparathyroidism (SHPT with increased serum concentrations of bone resorption markers such as the cross-linked N-telopeptide of type I collagen (NTX and type-5b tartrate-resistant acid phosphatase (TRAP. When SHPT proves refractory to treatment, parathyroidectomy (PTX may be needed. Renal patients on maintenance HD who received PTX for refractory SHPT (n=23 or who did not develop refractory SHPT (control subjects; n=25 were followed prospectively for 4 weeks. Serum intact parathyroid hormone (iPTH, NTX, TRAP, and bone alkaline phosphatase (BAP concentrations were measured serially and correlation analyses were performed. iPTH values decreased rapidly and dramatically. BAP values increased progressively with peak increases observed at 2 weeks after surgery. NTX and TRAP values decreased concurrently and progressively through 4 weeks following PTX. A significant correlation between TRAP and NTX values was observed before PTX but not at 4 weeks after PTX. Additionally, the fractional changes in serum TRAP were larger than those in serum NTX at all times examined after PTX. Serum iPTH, TRAP, and NTX values declined rapidly following PTX for SHPT. Serum TRAP values declined to greater degrees than serum NTX values throughout the 4-week period following PTX.

  3. Sensitivity and specificity of serum cross-linked N-telopeptides of type 1 collagen (NTx in patients with solid tumors

    Directory of Open Access Journals (Sweden)

    Fernando Jablonka

    2009-03-01

    Full Text Available Objective: Cross-linked N-telopeptides of type I collagen (NTx increase in situations in which bone resorption is increased, such as osteoporosis and bone metastasis. It was evaluated the usefulness of NTx for the diagnosis of bone metastases in patients with solid tumors. Methods: It was conducted a prospective study, at a tertiary public hospital. A quantitative enzyme-linked immunosorbent assay (ELISA assay of serum NTx levels in 19 subjects without a history of cancer and 62 patients with various solid tumors referred for a bone scan was evaluated. Three specialists read all bone scans. Rresults: It was not found any significant correlations between serum NTx and age, sex, history of bone pain, tumor type and bone alkaline phosphatase levels. We found a significant correlation between serum NTx and alkaline phosphatase levels (r2 = 0.08, p  = 0.022. Serum NTx sensitivity, specificity, positive and negative predictive values and area under the receiver operating characteristic (ROC curve for the presence of bone metastases were 0.34, 0.92, 0.95, 0.22 and 0.59, respectively. Cconclusions: It was concluded that serum levels of NTx are highly sensitive for the diagnosis of bone metastases in patients with solid tumors.

  4. The Effects of Scleral Collagen Cross-Linking Using Glyceraldehyde on the Progression of Form-Deprived Myopia in Guinea Pigs

    Directory of Open Access Journals (Sweden)

    Yanhua Chu

    2016-01-01

    Full Text Available To investigate the effects of collagen cross-linking using glyceraldehyde on the biomechanical properties of the sclera and the axial elongation of form-deprived myopia in the guinea pig. Thirty-six guinea pigs were randomly assigned to four groups: FDM (form-deprived myopia; FDMG (form-deprived myopia treated with glyceraldehyde; FDMS (form-deprived myopia treated with 0.9% isotonic sodium chloride; and normal control (free of form-deprivation. FDM was achieved in the right eye using a latex facemask. The right eye in FDMG was treated with a posterior subtenon injection of 0.5 M glyceraldehyde; 0.9% isotonic sodium chloride was administered to the right eye in FDMS group using the same method. Axial length, refraction, and stress-strain of the sclera were measured at scheduled time points. The treated eyes were also examined histologically by light microscopy. It was found that glyceraldehyde treatment significantly increased the stiffness of the sclera in the FDM eyes and abnormalities have not been observed in the retina and optic nerve of the treated eyes. But the development of myopia was not affected.

  5. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma

    OpenAIRE

    Alanazi, Saud A.; Turki Almubrad; AlIbrahim, Ahmad I. A.; Khan, Adnan A; Saeed Akhtar

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma w...

  6. Role of nuclear factor-kappaB in interleukin-1-induced collagen degradation by corneal fibroblasts.

    Science.gov (United States)

    Lu, Ying; Fukuda, Ken; Li, Qin; Kumagai, Naoki; Nishida, Teruo

    2006-09-01

    The proinflammatory cytokine interleukin (IL)-1 is implicated in corneal ulceration. The role of nuclear factor (NF)-kappaB in the IL-1-induced degradation of collagen by corneal fibroblasts that underlies corneal ulceration was investigated. Rabbit corneal fibroblasts were cultured in three-dimensional gels of type I collagen with or without IL-1 and sulfasalazine, an inhibitor of NF-kappaB activation. Collagen degradation was assessed from the amount of hydroxyproline generated by acid-heat hydrolysis of culture supernatants. The release of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) into culture supernatants was examined by immunoblot analysis and gelatin zymography, and the cellular abundance of MMP and TIMP mRNAs was determined by reverse transcription and real-time polymerase chain reaction analysis. The phosphorylation and degradation of the NF-kappaB-inhibitory protein IkappaB-alpha were examined by immunoblot analysis. The subcellular localization and DNA binding activity of the p65 subunit of NF-kappaB were evaluated by immunofluorescence analysis and with a colorimetric assay, respectively. The transactivation activity of NF-kappaB was assessed with a reporter gene assay. Sulfasalazine inhibited IL-1-induced collagen degradation by corneal fibroblasts in a concentration-dependent manner. It also inhibited the stimulatory effects of IL-1 on the synthesis or activation of various MMPs in a concentration-dependent manner. IL-1 induced the phosphorylation and degradation of IkappaB-alpha, the nuclear translocation and up-regulation of the DNA binding activity of the p65 subunit of NF-kappaB, and the activation of NF-kappaB in a manner sensitive to sulfasalazine. These results suggest that NF-kappaB contributes to the IL-1-induced degradation of collagen by corneal fibroblasts and is therefore a potential therapeutic target for treatment of corneal ulcers.

  7. Comparison of the Early Clinical Outcomes between Combined Small-Incision Lenticule Extraction and Collagen Cross-Linking versus SMILE for Myopia

    Directory of Open Access Journals (Sweden)

    Alex L. K. Ng

    2016-01-01

    Full Text Available Background. To compare the early outcome of combined SMILE and collagen crosslinking (SMILE Xtra with SMILE. Method. Prospective, comparative interventional study of 21 eyes receiving SMILE Xtra using a low energy protocol and 32 control eyes receiving SMILE only. The outcomes were compared at 1, 3, and 6 months postoperatively. Results. Both groups had myopia with spherical equivalent refraction (SEQ > 4.00 D. The SMILE Xtra group had thinner preoperative central corneal thickness and residual stromal bed thickness (p<0.021. At 6 months, no eyes lost more than 1 line in corrected distance visual acuity. The safety index was 0.96±0.06 and 1.00±0.00 in SMILE Xtra and control, respectively (p<0.001. 89% and 94% of eyes were within ±0.50 D of target refraction, respectively, with the mean error in SEQ correction being -0.17±0.26 D for SMILE Xtra and +0.03±0.25 D for control (p=0.021. The efficacy index was 0.88±0.13 and 0.97±0.06, respectively (p=0.005. Conclusion. SMILE Xtra had good overall safety profile and predictability at 6 months. However, when compared with control, the safety index and efficacy index were statistically significantly lower in the early postoperative period.

  8. Suppression by an RAR-γ Agonist of Collagen Degradation Mediated by Corneal Fibroblasts.

    Science.gov (United States)

    Kimura, Kazuhiro; Zhou, Hongyan; Orita, Tomoko; Kobayashi, Masaaki; Nishida, Teruo; Sonoda, Koh-Hei

    2017-04-01

    To examine the role of retinoic acid receptor (RAR) isoforms in interleukin-1β (IL-1β)-induced collagen degradation by corneal fibroblasts. Primary rabbit corneal fibroblasts embedded in a three-dimensional collagen gel were incubated with or without all-trans retinoic acid (ATRA), the RAR-α agonist Am580, the RAR-β agonist AC55649, or the RAR-γ agonist R667. Collagen degradation was determined by measurement of hydroxyproline produced in acid hydrolysates of culture supernatants. Matrix metalloproteinase (MMP) expression was evaluated by immunoblot analysis and gelatin zymography. The phosphorylation of mitogen-activated protein kinases (MAPKs) and the endogenous nuclear factor (NF)-κB inhibitor IκB-α was examined by immunoblot analysis. Cell proliferation was measured with a bromodeoxyuridine incorporation assay, and cell viability was determined by measurement of the release of lactate dehydrogenase. Interleukin-1β-induced collagen degradation by corneal fibroblasts was inhibited by ATRA, Am580, and R667 in a concentration-dependent manner but was unaffected by AC55649, with the inhibitory effects of ATRA and R667 being markedly greater than that of Am580. The IL-1β-induced production of MMP-1, MMP-2, MMP-3, and MMP-9 by corneal fibroblasts was also inhibited by R667 in a concentration-dependent manner. R667 inhibited the IL-1β-induced phosphorylation of IκB-α but not that of MAPKs. R667 had no effect on the proliferation or viability of corneal fibroblasts. The RAR-γ agonist R667 suppressed MMP production and thereby inhibited collagen degradation by corneal fibroblasts exposed to the proinflammatory cytokine IL-1β. These effects of R667 may be mediated by the NF-κB signaling pathway.

  9. Dexamethasone inhibition of IL-1-induced collagen degradation by corneal fibroblasts in three-dimensional culture.

    Science.gov (United States)

    Lu, Ying; Fukuda, Ken; Liu, Yang; Kumagai, Naoki; Nishida, Teruo

    2004-09-01

    Corticosteroids regulate the functions of inflammatory cells. The purpose of the present study was to investigate the effect of dexamethasone on collagen degradation by corneal fibroblasts, an underlying cause of corneal ulceration. Rabbit corneal fibroblasts were cultured in three-dimensional gels of type I collagen and in the absence or presence of IL-1beta or dexamethasone. The extent of collagen degradation was determined by measurement of the amount of hydroxyproline generated by acid-heat hydrolysis of culture supernatants. The expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) was evaluated by immunoblot analysis, gelatin zymography, and reverse transcription and real-time polymerase chain reaction. The phosphorylation of mitogen-activated protein kinases (MAPKs) in corneal fibroblasts was assessed by immunoblot analysis. Dexamethasone inhibited IL-1beta-induced collagen degradation by corneal fibroblasts in a dose-dependent manner. Both the synthesis and activation of MMPs and the expression of TIMPs were inhibited by dexamethasone, as was the activity of plasmin in culture supernatants. Dexamethasone also inhibited the IL-1beta-induced phosphorylation of the MAPKs extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not that of p38. Dexamethasone exerted multiple effects on the MMP-TIMP system in corneal fibroblasts and thereby inhibited IL-1beta-induced collagen degradation by these cells. Inhibition of the IL-1beta-induced activation of ERK and JNK may contribute to these effects of dexamethasone. Copyright Association for Research in Vision and Ophthalmology

  10. Effect of Adipic Acid Derivative Cross-linking on the Resistanceto Trypsin Degradation of Collagen%己二酸衍生物交联对胶原抗胰蛋白酶解的影响

    Institute of Scientific and Technical Information of China (English)

    陈以会; 刘文涛; 李国英

    2012-01-01

    In order to improve the enzymatic resistance of collagen, collagen was cross-linked with N-hydroxysuccinimide activated adipic acid (NHS-AA) at concentrations ranging from 0.25 mM to 4 mM. The results demonstrated that the digested collagen cross-linked with 1. 5 mM NHS-AA had the maximum weight remaining, minimum amino groups determined by trinitrobenzensulfonic acid (TNBS) assay, and the maximum denaturation temperature, obtained by means of differential scanning calorimeter (DSC ). Meanwhile, with increasing NHS-AA concentration, color of peptide maps of collagen digested by trypsin, obtained by means of sodium dodeeyl sulphate polyarrylamide gel electrophoresis ( SDS-PAGE), gradually became lighter. All shown enzymatic resistance of collagen was improved significantly owing to interference of the penetration of the enzyme into the cross-linked collagen network. The results demonstrated that collagen cross-linked with 1. 5 mM NHS-AA had optimum enzymatic degradability due to the highest cross-linking density of collagen. The susceptibility of collagen towards enzymatic degradation could be controlled by varying the degree of cross-linking of the samples.%为了提高胶原耐酶解能力,以N-羟基琥珀酰亚胺-己二酸酯(NHS-AA)为交联剂(浓度CNHS-AA为0.25-4.0mmol/L)交联胶原,采用质量法、三硝基苯磺酸法、差示扫描量热法和十二烷基硫酸钠-丙烯酰胺凝胶电泳等对胶原耐胰蛋白酶解的性能进行了研究.结果显示,当CNHS-AA为1.5 mmol/L时,胶原酶解重量保持率达到最大,自由氨基浓度达到最低,胶原的变性温度达到最高;酶解产物电泳谱带的颜色随CNHS-AA增加而逐渐变浅.研究表明,NHS-AA与胶原的自由氨基反应形成的交联网状结构有效地阻碍了胰蛋白酶渗透进入胶原材料,从而提高了胶原抗酶解能力,当CNHS-AA=1.5 mmol/L时,胶原抗酶解能力达到最强.由此可见,可以通过改变交联度来控制胶原胰蛋白酶降解的速率.

  11. Type V collagen: molecular structure and fibrillar organization of the chicken alpha 1(V) NH2-terminal domain, a putative regulator of corneal fibrillogenesis

    National Research Council Canada - National Science Library

    Linsenmayer, T F; Gibney, E; Igoe, F; Gordon, M K; Fitch, J M; Fessler, L I; Birk, D E

    1993-01-01

    Previous work from our laboratories has demonstrated that: (a) the striated collagen fibrils of the corneal stroma are heterotypic structures composed of type V collagen molecules coassembled along with those of type I collagen, (b...

  12. United States Multicenter Clinical Trial of Corneal Collagen Crosslinking for Keratoconus Treatment.

    Science.gov (United States)

    Hersh, Peter S; Stulting, R Doyle; Muller, David; Durrie, Daniel S; Rajpal, Rajesh K

    2017-09-01

    To evaluate the safety and efficacy of corneal collagen crosslinking (CXL) for the treatment of progressive keratoconus. Prospective, randomized, multicenter, controlled clinical trial. Patients with progressive keratoconus (n = 205). The treatment group underwent standard CXL and the sham control group received riboflavin alone without removal of the epithelium. The primary efficacy criterion was the change over 1 year of topography-derived maximum keratometry value, comparing treatment with control group. Secondary outcomes evaluated were corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent, endothelial cell count, and adverse events. In the CXL treatment group, the maximum keratometry value decreased by 1.6 diopters (D) from baseline to 1 year, whereas keratoconus continued to progress in the control group. In the treatment group, the maximum keratometry value decreased by 2.0 D or more in 28 eyes (31.4%) and increased by 2.0 D or more in 5 eyes (5.6%). The CDVA improved by an average of 5.7 logarithm of the minimum angle of resolution (logMAR) units. Twenty-three eyes (27.7%) gained and 5 eyes lost (6.0%) 10 logMAR or more. The UDVA improved 4.4 logMAR. Corneal haze was the most frequently reported CXL-related adverse finding. There were no significant changes in endothelial cell count 1 year after treatment. Corneal collagen crosslinking was effective in improving the maximum keratometry value, CDVA, and UCVA in eyes with progressive keratoconus 1 year after treatment, with an excellent safety profile. Corneal collagen crosslinking affords the keratoconic patient an important new option to decrease progression of this ectatic corneal process. Copyright © 2017 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

  13. A Case of “en bloc” Excision of a Chest Wall Leiomyosarcoma and Closure of the Defect with Non-Cross-Linked Collagen Matrix (Egis®

    Directory of Open Access Journals (Sweden)

    Marco Rastrelli

    2016-10-01

    Full Text Available Sarcomas arising from the chest wall account for less than 20% of all soft tissue sarcomas, and at this site, primitive tumors are the most frequent to occur. Leiomyosarcoma is a malignant smooth muscle tumor and the best outcomes are achieved with wide surgical excision. Although advancements have been made in treatment protocols, leiomyosarcoma remains one of the more difficult soft tissue sarcoma to treat. Currently, general local control is obtained with surgical treatment with wide negative margins. We describe the case of a 50-year-old man who underwent a chest wall resection involving a wide portion of the pectoralis major and minor muscle, the serratus and part of the second, third and fourth ribs of the left side. The full-thickness chest wall defect of 10 × 8 cm was closed using a non-cross-linked acellular dermal matrix (Egis® placed in two layers, beneath the rib plane and over it. A successful repair was achieved with no incisional herniation and with complete tissue regeneration, allowing natural respiratory movements. No complications were observed in the postoperative course. Biological non-cross-linked matrix, derived from porcine dermis, behaves like a scaffold supporting tissue regeneration; it can be successfully used as an alternative to synthetic mesh for chest wall reconstruction.

  14. Quantification of collagen ultrastructure after penetrating keratoplasty - implications for corneal biomechanics.

    Directory of Open Access Journals (Sweden)

    Craig Boote

    Full Text Available PURPOSE: To quantify long-term changes in stromal collagen ultrastructure following penetrating keratoplasty (PK, and evaluate their possible implications for corneal biomechanics. METHODS: A pair of 16 mm post-mortem corneo-scleral buttons was obtained from a patient receiving bilateral penetrating keratoplasty 12 (left/28 (right years previously. Small-angle x-ray scattering quantified collagen fibril spacing, diameter and spatial order at 0.5 mm or 0.25 mm intervals along linear scans across the graft margin. Corresponding control data was collected from two corneo-scleral buttons with no history of refractive surgery. Wide-angle x-ray scattering quantified collagen fibril orientation at 0.25 mm (horizontal×0.25 mm (vertical intervals across both PK specimens. Quantification of orientation changes in the graft margin were verified by equivalent analysis of data from a 13 year post-operative right PK specimen obtained from a second patient in a previous study, and comparison made with new and published data from normal corneas. RESULTS: Marked changes to normal fibril alignment, in favour of tangentially oriented collagen, were observed around the entire graft margin in all PK specimens. The total number of meridional fibrils in the wound margin was observed to decrease by up to 40%, with the number of tangentially oriented fibrils increasing by up to 46%. As a result, in some locations the number of fibrils aligned parallel to the wound outnumbered those spanning it by up to five times. Localised increases in fibril spacing and diameter, with an accompanying reduction in matrix order, were also evident. CONCLUSIONS: Abnormal collagen fibril size and spatial order within the PK graft margin are indicative of incomplete stromal wound remodelling and the long term persistence of fibrotic scar tissue. Lasting changes in collagen fibril orientation in and around PK wounds may alter corneal biomechanics and compromise the integrity of the graft

  15. Iontophoresis-assisted corneal cross-linking in pediatric keratoconus%离子导入辅助角膜交联治疗青少年圆锥角膜

    Institute of Scientific and Technical Information of China (English)

    贾洪真; 庞旭; 李娜; 李刚; 樊郑军; 彭秀军

    2016-01-01

    • AIM: To evaluate the efficacy and safety of iontophoresis - assisted transepithelial corneal cross -linking ( I-CXL) in a population of patients younger than 18y.•METHODS: Fifteen eyes of 12 patients aged 18y or younger (mean age, 15. 8 ± 2. 08y; range, 12-18y) were treated. After 0. 1% riboflavin-distilled water solution was administered by iontophoresis-assisted ( Current 1mA ) transepithelial method for 5min in total, standard surface UVA irradiation (370 nm, 3 mW/cm2 ) was performed for 30min. The uncorrected visual acuity ( UCVA ), best corrected visual acuity ( BCVA ) , K1 , K2 , Kmax , Kmean , corneal refractive astigmatism, endothelial cell density, intraocular pressure ( IOP ) , the corneal apex thickness and the thinnest corneal thickness were measured preoperatively 3mo and 12mo postoperatively. Corneal parameters were assessed by corneal topography ( Wavelight, Allergro Topolyzer & Topolyzer Vario, Germany) . Corneal endothelium was photographed with a noncontact Specular Microscope ( SP 2000, Topcon, Japan) .•RESULTS: Twelve months after the procedure, no significant changes occurred in the UCVA, BCVA, K1 , K2 , Kmax , Kmean , corneal refractive astigmatism, endothelial cell density and IOP. The thinnest corneal thickness decreased from 468.08±33.40 μm to 447.46±40.20 μm (t=4. 379, P=0. 001). The corneal apex thickness decreased from 476.07±35.96 μm to 454.60±49.32 μm (t=4.270, P=0. 001 ). The differences of the above were both statistically significant.•CONCLUSION:I-CXL using 0. 1% riboflavin-distilled water solution for pediatric keratoconus is effective and safe which can halt deterioration of keratoconus within 1y, but permanent effects still need to be observed.%目的:评估离子导入辅助的跨上皮角膜交联治疗青少年圆锥角膜的安全性和有效性。方法:搜集12例(年龄12~18岁,平均15.8±2.08岁)进展期圆锥角膜患者,共15眼,采用0.1%核黄素蒸馏水溶液,离子导入(1 m

  16. Transverse depth-dependent changes in corneal collagen lamellar orientation and distribution.

    Science.gov (United States)

    Abass, Ahmed; Hayes, Sally; White, Nick; Sorensen, Thomas; Meek, Keith M

    2015-03-06

    It is thought that corneal surface topography may be stabilized by the angular orientation of out-of plane lamellae that insert into the anterior limiting membrane. In this study, micro-focus X-ray scattering data were used to obtain quantitative information about lamellar inclination (with respect to the corneal surface) and the X-ray scatter intensity throughout the depth of the cornea from the centre to the temporal limbus. The average collagen inclination remained predominantly parallel to the tissue surface at all depths. However, in the central cornea, the spread of inclination angles was greatest in the anterior-most stroma (reflecting the increased lamellar interweaving in this region), and decreased with tissue depth; in the peripheral cornea inclination angles showed less variation throughout the tissue thickness. Inclination angles in the deeper stroma were generally higher in the peripheral cornea, suggesting the presence of more interweaving in the posterior stroma away from the central cornea. An increase in collagen X-ray scatter was identified in a region extending from the sclera anteriorly until about 2 mm from the corneal centre. This could arise from the presence of larger diameter fibrils, probably of scleral origin, which are known to exist in this region. Incorporation of this quantitative information into finite-element models will further improve the accuracy with which they can predict the biomechanical response of the cornea to pathology and refractive procedures.

  17. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma

    Directory of Open Access Journals (Sweden)

    Saud A. Alanazi

    2015-01-01

    Full Text Available We report here the ultrastructural organization of collagen fibrils (CF and proteoglycans (PGs of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS/dermatan sulfate (DS PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark.

  18. Ultrastructure Organization of Collagen Fibrils and Proteoglycans of Stingray and Shark Corneal Stroma.

    Science.gov (United States)

    Alanazi, Saud A; Almubrad, Turki; AlIbrahim, Ahmad I A; Khan, Adnan A; Akhtar, Saeed

    2015-01-01

    We report here the ultrastructural organization of collagen fibrils (CF) and proteoglycans (PGs) of the corneal stroma of both the stingray and the shark. Three corneas from three stingrays and three corneas from three sharks were processed for electron microscopy. Tissues were embedded in TAAB 031 resin. The corneal stroma of both the stingray and shark consisted of parallel running lamellae of CFs which were decorated with PGs. In the stingray, the mean area of PGs in the posterior stroma was significantly larger than the PGs of the anterior and middle stroma, whereas, in the shark, the mean area of PGs was similar throughout the stroma. The mean area of PGs of the stingray was significantly larger compared to the PGs, mean area of the shark corneal stroma. The CF diameter of the stingray was significantly smaller compared to the CF diameter in the shark. The ultrastructural features of the corneal stroma of both the stingray and the shark were similar to each other except for the CFs and PGs. The PGs in the stingray and shark might be composed of chondroitin sulfate (CS)/dermatan sulfate (DS) PGs and these PGs with sutures might contribute to the nonswelling properties of the cornea of the stingray and shark.

  19. Development of human corneal epithelium on organized fibrillated transparent collagen matrices synthesized at high concentration.

    Science.gov (United States)

    Tidu, Aurélien; Ghoubay-Benallaoua, Djida; Lynch, Barbara; Haye, Bernard; Illoul, Corinne; Allain, Jean-Marc; Borderie, Vincent M; Mosser, Gervaise

    2015-08-01

    Several diseases can lead to opacification of cornea requiring transplantation of donor tissue to restore vision. In this context, transparent collagen I fibrillated matrices have been synthesized at 15, 30, 60 and 90 mg/mL. The matrices were evaluated for fibril organizations, transparency, mechanical properties and ability to support corneal epithelial cell culture. The best results were obtained with 90 mg/mL scaffolds. At this concentration, the fibril organization presented some similarities to that found in corneal stroma. Matrices had a mean Young's modulus of 570 kPa and acellular scaffolds had a transparency of 87% in the 380-780 nm wavelength range. Human corneal epithelial cells successfully colonized the surface of the scaffolds and generated an epithelium with characteristics of corneal epithelial cells (i.e. expression of cytokeratin 3 and presence of desmosomes) and maintenance of stemness during culture (i.e. expression of ΔNp63α and formation of holoclones in colony formation assay). Presence of cultured epithelium on the matrices was associated with increased transparency (89%). Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Collagen cross-linking by adipose-derived mesenchymal stromal cells and scar-derived mesenchymal cells: Are mesenchymal stromal cells involved in scar formation?

    NARCIS (Netherlands)

    Bogaerdt, van den A.J.; Veen, van der A.G.; Zuijlen, van P.P.; Reijnen, L.; Verkerk, M.; Bank, R.A.; Middelkoop, E.; Ulrich, M.

    2009-01-01

    In this work, different fibroblast-like (mesenchymal) cell populations that might be involved in wound healing were characterized and their involvement in scar formation was studied by determining collagen synthesis and processing. Depending on the physical and mechanical properties of the tissues,

  1. Collagen cross-linking by adipose-derived mesenchymal stromal cells and scar-derived mesenchymal cells : Are mesenchymal stromal cells involved in scar formation?

    NARCIS (Netherlands)

    van den Bogaerdt, Antoon J.; van der Veen, Vincent C.; van Zuijlen, Paul P. M.; Reijnen, Linda; Verkerk, Michelle; Bank, Ruud A.; Middelkoop, Esther; Ulrich, Magda M. W.

    2009-01-01

    In this work, different fibroblast-like (mesenchymal) cell populations that might be involved in wound healing were characterized and their involvement in scar formation was studied by determining collagen synthesis and processing. Depending on the physical and mechanical properties of the tissues,

  2. In vitro characterization of electrochemically compacted collagen matrices for corneal applications.

    Science.gov (United States)

    Kishore, Vipuil; Iyer, Ranjani; Frandsen, Athela; Nguyen, Thuy-Uyen

    2016-10-06

    Loss of vision due to corneal disease is a significant problem worldwide. Transplantation of donor corneas is a viable treatment option but limitations such as short supply and immune-related complications call for alternative options for the treatment of corneal disease. A tissue engineering-based approach using a collagen scaffold is a promising alternative to develop a bioengineered cornea that mimics the functionality of native cornea. In this study, an electrochemical compaction method was employed to synthesize highly dense and transparent collagen matrices. We hypothesized that chemical crosslinking of electrochemically compacted collagen (ECC) matrices will maintain transparency, improve stability, and enhance the mechanical properties of the matrices to the level of native cornea. Further, we hypothesized that keratocyte cell viability and proliferation will be maintained on crosslinked ECC matrices. The results indicated that uncrosslinked and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide (EDC-NHS) crosslinked ECC matrices were highly transparent with light transmission measurements comparable to native cornea. Stability tests showed that while the uncrosslinked ECC matrices degraded within 6 h when treated with collagenase, EDC-NHS or genipin crosslinking significantly improved the stability of ECC matrices (192 h for EDC-NHS and 256 h for genipin). Results from the mechanical tests showed that both EDC-NHS and genipin crosslinking significantly improved the strength and modulus of ECC matrices. Cell culture studies showed that keratocyte cell viability and proliferation are maintained on EDC-NHS crosslinked ECC matrices. Overall, results from this study suggest that ECC matrices have the potential to be developed as a functional biomaterial for corneal repair and regeneration.

  3. Clinical outcomes at one year following keratoconus treatment with accelerated transepithelial cross-linking

    Science.gov (United States)

    Artola, Alberto; Piñero, David P.; Ruiz-Fortes, Pedro; Soto-Negro, Roberto; Pérez-Cambrodí, Rafael J

    2017-01-01

    This study evaluated the clinical outcomes in keratoconus corneas following accelerated transepithelial corneal collagen cross-linking (CXL) (Avedro KXL® system, Waltham, MA, USA) over one year of follow-up. The mean depth of the demarcation line measured by optical coherence tomography (OCT) was 205.19 µm. One month after surgery, a non-statistically significant change was noted in sphere (P=0.18) and in spherical equivalent (P=0.17), whereas a significant improvement was observed in corrected distance visual acuity (P=0.04). A significant change was observed in topographic astigmatism (P=0.03) and posterior corneal a sphericity (P=0.04). Accelerated transepithelial CXL may be a useful technique for the management of progressive keratoconus. PMID:28503442

  4. Corneal collagen crosslinking for ectasia after laser in situ keratomileusis: long-term results.

    Science.gov (United States)

    Yildirim, Aydin; Cakir, Hanefi; Kara, Necip; Uslu, Hasim; Gurler, Bulent; Ozgurhan, Engin Bilge; Colak, Hatice Nur

    2014-10-01

    To report the long-term results of corneal collagen crosslinking (CXL) treatment for post-laser in situ keratomileusis (LASIK) ectasia. Turkiye Hospital Eye Clinic and Fatih University Medical Faculty, Department of Ophthalmology, Istanbul, Turkey. Retrospective case series study. Consecutive patients with ectasia after LASIK were treated with CXL. The main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical and cylindrical refractions, and simulated keratometry (K) values. The study enrolled 20 eyes (14 patients; 7 women) with a mean age of 34.8 years ± 6.0 (SD) (range 25 to 45 years) and mean follow-up of 42 months (range 36 to 60 months). The UDVA and CDVA improved significantly, from 0.78 ± 0.61 logMAR to 0.53 ± 0.36 logMAR (P=.007) and from 0.27 ± 0.23 logMAR to 0.19 ± 0.13 logMAR, respectively (P≤.028). No eye lost 1 or more Snellen lines of UDVA or CDVA. Although the mean spherical refraction was not significantly different at the last visit (P=.074), the mean cylindrical refraction decreased significantly (P=.036). The maximum K value decreased from 46.0 ± 4.4 diopters (D) at baseline to 45.6 ± 3.8 D at the last visit (P=.013). By the last visit, the maximum K value decreased (≥1.0 D) in 5 eyes and remained stable in 15 eyes. No serious complications occurred. Corneal collagen crosslinking yielded long-term stability in cases with post-LASIK corneal ectasia without significant side effects. Improvements in visual acuity, cylindrical refraction, and maximum K values occurred. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  5. Outcome of Corneal Collagen Crosslinking for Progressive Keratoconus in Paediatric Patients

    Directory of Open Access Journals (Sweden)

    Deepa Viswanathan

    2014-01-01

    Full Text Available Purpose. To evaluate the efficacy of corneal collagen crosslinking for progressive keratoconus in paediatric patients. Methods. This prospective study included 25 eyes of 18 patients (aged 18 years or younger who underwent collagen crosslinking performed using riboflavin and ultraviolet-A irradiation (370 nm, 3 mW/cm2, 30 min. Results. The mean patient age was 14.3 ± 2.4 years (range 8–17 and mean followup duration was 20.1 ± 14.25 months (range 6–48. Crosslinked eyes demonstrated a significant reduction of keratometry values. The mean baseline simulated keratometry values were 46.34 dioptres (D in the flattest meridian and 50.06 D in the steepest meridian. At 20 months after crosslinking, the values were 45.67 D (P=0.03 and 49.34 D (P=0.005, respectively. The best spectacle corrected visual acuity (BSCVA and topometric astigmatism improved after crosslinking. Mean logarithm of the minimum angle of resolution (logMAR BSCVA decreased from 0.24 to 0.21 (P=0.89 and topometric astigmatism reduced from mean 3.50 D to 3.25 D (P=0.51. Conclusions. Collagen crosslinking using riboflavin and ultraviolet-A is an effective treatment option for progressive keratoconus in paediatric patients. Crosslinking stabilises the condition and, thus, reduces the need for corneal grafting in these young patients.

  6. 离子导入辅助跨上皮角膜胶原交联治疗进展期圆锥角膜2a 随访分析%A two - year's results of iontophoresis -assisted transepithelial corneal cross -linking for progressive keratoconus

    Institute of Scientific and Technical Information of China (English)

    贾洪真; 庞旭; 樊郑军; 彭秀军

    2016-01-01

    AIM: To report a two- year's results of iontophoresis-assisted transepithelial corneal cross-linking (I-CXL) for progressive keratoconus. METHODS: Thirty - four eyes in 24 patients with progressive keratoconus ( mean age 21. 0 ± 5. 6 years;range: 14-32 years) were treated. After 1g/ L riboflavin-distilled water solution was administered by iontophoresis-assited (current 1mA) transepithelial method for 5min in total, standard surface UVA irradiation ( 370nm, 3mW/cm2 ) was performed at a 1 - cm distance for 30min. The best corrected visual acuity ( BCVA ) measured as LogMAR number, corneal refractive astigmatism, K1, K2, Kmean, Kmax, intraocular pressure, endothelial cell density, the thickness at corneal apex and the thinnest point were measured preoperatively and 2a postoperatively. RESULTS:At 2a after the procedure, BCVA (LogMAR) improved from 0. 32 ± 0. 25 to 0. 25 ± 0. 19 ( t = 2. 849, P =0. 015). K1 decreased from 47. 12±4. 33 to 46. 06±4. 77 (t =2. 652, P= 0. 015). K2 decreased from 51. 36±5. 59 to 50. 40±6. 16 (t= 2. 121, P= 0. 047). Kmean decreased from 49. 12±4. 76 to 48. 10±5. 25(t = 2. 663, P = 0. 015). Kmax decreased from 57. 57±8. 30 to 55. 91±8. 14 (t = 2. 398, P = 0. 026). The corneal apex thickness decreased from 476. 90±38. 71μ m to 454. 43 ± 40. 86μ m ( t = 2. 853, P = 0. 010 ). The thinnest thickness decreased from 464. 38 ± 39. 92μ m to 433. 86 ±50. 78μ m ( t = 3. 485, P = 0. 002 ). Corneal refractive astigmatism, intraocular pressure and endothelial cell density did not show significant changes. CONCLUSION: I - CXL for progressive keratoconus is safe and effective which can prevent deterioration of progressive keratoconus within 2a, but further long-term studies are necessary still.%目的:报道离子导入辅助跨上皮角膜胶原交联(iontophoresis-assited transepithelial corneal collagen cross-linking, I-CXL)治疗进展期圆锥角膜的2a 观察结果。  方法:选取进展期圆锥角膜患者24例34

  7. A novel collagen film with micro-rough surface structure for corneal epithelial repair fabricated by freeze drying technique

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yang [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Ren, Li, E-mail: psliren@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China); Wang, Yingjun, E-mail: imwangyj@163.com [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641 (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou 510006 (China); Guangdong Province Key Laboratory of Biomedical Engineering, South China University of Technology, Guangzhou 510006 (China)

    2014-05-01

    Highlights: • Collagen film with micro-rough surface is fabricated by freeze drying technique. • The film has suitable water uptake capability and toughness performance. • The film has good optical performance. • Human corneal epithelial cells studies confirmed the biocompatibility of the film. - Abstract: Corneal epithelial defect is a common disease and keratoplasty is a common treatment method. A collagen film with micro-rough surface was fabricated through a simple freeze drying technique in this study. Compared with the air-dried collagen film (AD-Col), this freeze-dried collagen film (FD-Col) has a more suitable water uptake capability (about 85.5%) and toughness performance. Both of the two films have good optical properties and the luminousness of them is higher than 80%. Besides, the adhesion and proliferation rate of human corneal epithelial cells on the micro-rough surface of FD-Col film is higher than that on the smooth surface of AD-Col film. The results indicate that this FD-Col film may have potential applications for corneal epithelial repair.

  8. Ⅱ型噁唑烷-儿茶素固化皮胶原的特性表征%Characteristics of Collagen Cross-Linked by Oxazolidine Ⅱ and Catechin

    Institute of Scientific and Technical Information of China (English)

    王亚娟; 周国权; 邵双喜; 郭军; 单志华

    2011-01-01

    Using catechin (CC) and oxazolidine Ⅱ (ZE) as the basic cross linking agents, the raw sheep skin collagen was treated. The influences of modify sequence, moisture content of the treated sample and kind of used solvents on the thermal stability of the samples were investigated by examining the shrinkage temperature of the modified collagen. According to the scanning electron microscope (SEM) images of samples before and after shrinkage, the histological morphology was observed, and the shrink mechanism of modified collagen was speculated by comparing its SEM images. The results show that the catechin-oxazolidine tanning sequence can enhance the heat resistance of the modified collagen, whose shrinkage temperature can be enhanced to 113.5℃.The moisture content of the sample has a negative effect on its thermal stability, and the thermal stability of the collagen will decrease with the increase of its moisture content. As to the solvent choosing, the acidity of the solvent will do a more destruction to the hydrothermal stability of the modified collagen, especially for collagen treated with CC-ZE sequence. It was found that, regardless of the tanning sequence, the fibers of non-shrunk sample are more evenly spreaded and compact than that of shrunk sample, and the regular structure of the collagen will be broken after heat treatment.%选用儿茶素和Ⅱ型噁唑烷为基本交联剂交联动物皮胶原,通过对交联后胶原热变性温度的考察探索了双组分交联剂的加入顺序、样品湿含量及溶剂处理对其热稳定性的影响;根据扫描电镜图像对热变性前后交联胶原的组织形态进行了观察,进而推测了交联胶原的热变性机理.结果发现:先儿茶素后噁唑烷顺序交联的胶原热稳定性较高,其热变性温度可达113.5℃;交联后胶原湿含量对其耐热稳定性有较大影响,在一定范围内胶原的热稳定性随着湿含量的增加而降低;交联后胶原的贮存环境的pH对其

  9. 角膜胶原交联治疗进展期圆锥角膜%Corneal collagen cross-linking in the treatment of progressive keratoconus

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    圆锥角膜是一种以角膜扩张为特征,原因不明的双侧进行性角膜病变,可严重影响患者的视力.目前,使用角膜胶原交联治疗,已经成为可以有效阻止圆锥角膜进展的新方法,本文就角膜胶原交联治疗进展期圆锥角膜的原理、方法、并发症及展望进行综述.

  10. A role for topographic cues in the organization of collagenous matrix by corneal fibroblasts and stem cells.

    Science.gov (United States)

    Karamichos, Dimitrios; Funderburgh, Martha L; Hutcheon, Audrey E K; Zieske, James D; Du, Yiqin; Wu, Jian; Funderburgh, James L

    2014-01-01

    Human corneal fibroblasts (HCF) and corneal stromal stem cells (CSSC) each secrete and organize a thick stroma-like extracellular matrix in response to different substrata, but neither cell type organizes matrix on tissue-culture polystyrene. This study compared cell differentiation and extracellular matrix secreted by these two cell types when they were cultured on identical substrata, polycarbonate Transwell filters. After 4 weeks in culture, both cell types upregulated expression of genes marking differentiated keratocytes (KERA, CHST6, AQP1, B3GNT7). Absolute expression levels of these genes and secretion of keratan sulfate proteoglycans were significantly greater in CSSC than HCF. Both cultures produced extensive extracellular matrix of aligned collagen fibrils types I and V, exhibiting cornea-like lamellar structure. Unlike HCF, CSSC produced little matrix in the presence of serum. Construct thickness and collagen organization was enhanced by TGF-ß3. Scanning electron microscopic examination of the polycarbonate membrane revealed shallow parallel grooves with spacing of 200-300 nm, similar to the topography of aligned nanofiber substratum which we previously showed to induce matrix organization by CSSC. These results demonstrate that both corneal fibroblasts and stromal stem cells respond to a specific pattern of topographical cues by secreting highly organized extracellular matrix typical of corneal stroma. The data also suggest that the potential for matrix secretion and organization may not be directly related to the expression of molecular markers used to identify differentiated keratocytes.

  11. A role for topographic cues in the organization of collagenous matrix by corneal fibroblasts and stem cells.

    Directory of Open Access Journals (Sweden)

    Dimitrios Karamichos

    Full Text Available Human corneal fibroblasts (HCF and corneal stromal stem cells (CSSC each secrete and organize a thick stroma-like extracellular matrix in response to different substrata, but neither cell type organizes matrix on tissue-culture polystyrene. This study compared cell differentiation and extracellular matrix secreted by these two cell types when they were cultured on identical substrata, polycarbonate Transwell filters. After 4 weeks in culture, both cell types upregulated expression of genes marking differentiated keratocytes (KERA, CHST6, AQP1, B3GNT7. Absolute expression levels of these genes and secretion of keratan sulfate proteoglycans were significantly greater in CSSC than HCF. Both cultures produced extensive extracellular matrix of aligned collagen fibrils types I and V, exhibiting cornea-like lamellar structure. Unlike HCF, CSSC produced little matrix in the presence of serum. Construct thickness and collagen organization was enhanced by TGF-ß3. Scanning electron microscopic examination of the polycarbonate membrane revealed shallow parallel grooves with spacing of 200-300 nm, similar to the topography of aligned nanofiber substratum which we previously showed to induce matrix organization by CSSC. These results demonstrate that both corneal fibroblasts and stromal stem cells respond to a specific pattern of topographical cues by secreting highly organized extracellular matrix typical of corneal stroma. The data also suggest that the potential for matrix secretion and organization may not be directly related to the expression of molecular markers used to identify differentiated keratocytes.

  12. Cross-linking for microbial keratitis

    Directory of Open Access Journals (Sweden)

    Jayesh Vazirani

    2013-01-01

    Full Text Available The success of collagen cross-linking as a clinical modality to modify the clinical course in keratoconus seems to have fueled the search for alternative applications for this treatment. Current clinical data on its efficacy is limited and laboratory data seems to indicate that it performs poorly against resistant strains of bacteria and against slow growing organisms. However, the biological plausibility of crosslinking and the lack of effective strategies in managing infections with these organisms continue to focus attention on this potential treatment. Well-conducted experimental and clinical studies with controls are required to answer the questions of its efficacy in future.

  13. Differentiating untreated and cross-linked porcine corneas of the same measured stiffness with optical coherence elastography

    Science.gov (United States)

    Li, Jiasong; Han, Zhaolong; Singh, Manmohan; Twa, Michael D.; Larin, Kirill V.

    2014-11-01

    Structurally degenerative diseases, such as keratoconus, can significantly alter the stiffness of the cornea, directly affecting the quality of vision. Ultraviolet-induced collagen cross-linking (CXL) effectively increases corneal stiffness and is applied clinically to treat keratoconus. However, measured corneal stiffness is also influenced by intraocular pressure (IOP). Therefore, experimentally measured changes in corneal stiffness may be attributable to the effects of CXL, changes in IOP, or both. We present a noninvasive measurement method using phase-stabilized swept-source optical coherence elastography to distinguish between CXL and IOP effects on measured corneal stiffness. This method compared the displacement amplitude attenuation of a focused air-pulse-induced elastic wave. The damping speed of the displacement amplitudes at each measurement position along the wave propagation were compared for different materials. This method was initially tested on gelatin and agar phantoms of the same stiffness for validation. Consequently, untreated and CXL-treated porcine corneas of the same measured stiffness, but at different IOPs, were also evaluated. The results suggest that this noninvasive method may have the potential to detect the early stages of ocular diseases such as keratoconus or may be applied during CLX procedures by factoring in the effects of IOP on the measured corneal stiffness.

  14. Topographic outcomes after corneal collagen crosslinking in progressive keratoconus: 1-year follow-up

    Directory of Open Access Journals (Sweden)

    Mauro C. Tiveron Jr

    Full Text Available ABSTRACT Purpose: We aimed to report and analyze topographic and refractive outcomes following corneal collagen crosslinking (CXL in patients with progressive keratoconus (KC. Methods: We performed a retrospective, analytical, and observational study of 100 eyes from 74 progressive KC patients who underwent CXL at the Eye Hospital of Paraná. Keratometric values were analyzed preoperatively as well as 3 and 12 months postoperatively. Results: For a total of 100 eyes, 68 belonged to male patients. The mean age of our study population was 19.9 ± 5.61 years. The average visual acuity and topographic parameters overall were stable after 1 year (p<0.05. After 3 months, steepest keratometry reading (K2 and maximum keratometry (Kmax were significantly decreased (p<0.05. Regarding topographic astigmatism (dK, there was no significant difference between the 3-month and 12-month follow-ups. When we made comparisons between genders following CXL, there were no significant differences related to the changes in Kmax, K2, and spectacle-corrected distance visual acuity (SCDVA. Conclusions: CXL promoted stabilization or improvement of keratometric values and visual acuity. We found that keratoconus apex stability may be achieved 3 months after the procedure. There was no significant difference in keratometric and refractive values measured between male and female patients.

  15. Inhibition by a selective IkappaB kinase-2 inhibitor of interleukin-1-induced collagen degradation by corneal fibroblasts in three-dimensional culture.

    Science.gov (United States)

    Kondo, Yukiko; Fukuda, Ken; Adachi, Tadafumi; Nishida, Teruo

    2008-11-01

    Corneal ulcer results from excessive collagen degradation in the corneal stroma. Interleukin (IL)-1 promotes this process by activating signaling molecules that include nuclear factor (NF)-kappaB and stimulating the synthesis of matrix metalloproteinases (MMPs) in corneal fibroblasts. NF-kappaB activation is mediated by phosphorylation of the inhibitor IkappaB by IkappaB kinase (IKK)-2 and consequent IkappaB degradation. The authors investigated the effects of the IKK-2 inhibitor [5-(p-fluorophenyl)-2-ureido]thiophene-3-carboxamide (TPCA-1) on collagen degradation by corneal fibroblasts. Rabbit corneal fibroblasts were cultured in three-dimensional collagen gels. Collagen degradation was evaluated by spectrophotometric quantitation of hydroxyproline in culture supernatants subjected to acid-heat hydrolysis. Expression of MMPs was evaluated by immunoblot analysis, gelatin zymography, and real-time reverse transcription polymerase chain reaction analysis. The phosphorylation and degradation of IkappaBalpha and the subcellular localization of NF-kappaB were examined by immunoblot and immunofluorescence analyses, respectively. IL-1beta-induced collagen degradation by corneal fibroblasts was inhibited by TPCA-1 in a concentration- and time-dependent manner. TPCA-1 inhibited the IL-1beta-induced expression of MMP-1, -3, and -9 in these cells at both the mRNA and protein levels and the IL-1beta-induced activation of pro-MMP-2. In contrast to dexamethasone, TPCA-1 inhibited the phosphorylation and degradation of IkappaBalpha and the nuclear translocation of NF-kappaB induced by IL-1beta. An IKK-2 inhibitor blocked IL-1beta-induced collagen degradation by corneal fibroblasts by inhibiting the activation of the NF-kappaB signaling pathway and the upregulation of MMPs. IKK-2 inhibitors are thus potential alternatives to dexamethasone for the treatment of corneal ulcer.

  16. Study on the Effect of Temperature on the Conformation of Cross-Linked Collagen by Two-Dimensional Infrared Correlation Spectroscopy%二维红外相关光谱法研究温度对交联胶原结构的影响

    Institute of Scientific and Technical Information of China (English)

    陈以会; 田荟琳; 李季衡; 李国英

    2012-01-01

    The Fourier transform infrared spectroscopy and two dimensional correlation analysis method were applied to study a denaturing process of uncross-linked collagen and cross-linked collagen during varying temperature. It was found that the intensity of typically characteristic absorptions of collagen decreased and its peak shifted to low frequency, The amide II central absor-bance peak moved to a lower frequency by about ~10 cm-1, which indicated that the inter-chain hydrogen bonds which stabilized the triple helix conformation of collagen were disrupted during thermal denaturation, resulting in a conformational change. The intensity of auto-peak at 1 515 cn-1 was maximum, which suggested that the temperature had a big impact on amide IL In comparison with uncross-linked collagen, the intensity of cross-peaks of cross-linked collagen was weaker, which demonstrated that the effect of temperature on the structure of cross-linked collagen was smaller, and the thermal stability properties of collagen solution could be improved by cross-linking. While the order of second structure changes of cross-linked collagen was different These fundamental data should provide available information for understanding the relationship between the structure and function of cross-linked collagen.%采用傅里叶红外光谱和二维相关分析研究了改性前后胶原在升温(25~115℃)过程中结构的变化.结果显示,改性前后胶原的特征吸收峰强度降低,峰值向低波数移动,其中酰胺Ⅱ带的变化最明显,降低了~10 cm-1,表明维系胶原三股螺旋结构稳定的氢键被破坏,结构发生改变.在1515 cm-1处自相关峰强度最强,说明温度对酰胺Ⅱ带的影响最大.与未改性胶原相比,改性胶原的相关程度更弱,表明改性胶原结构受温度影响要小,交联提高了胶原的热稳定性;改性后胶原结构变化的顺序也不一样.由此可见,二维红外相关分析法能提供由温度引起的胶原结构动

  17. 交联对胶原溶液的动态流变性能和热稳定性能的影响%The effect of cross-linking on the dynamic viscoelastic properties and thermal stability of collagen solution

    Institute of Scientific and Technical Information of China (English)

    陈以会; 李国英

    2011-01-01

    为了提高胶原溶液的粘弹性能和热稳定性,以及提高胶原耐酶解的能力,使用一种新的交联剂--N-羟基琥珀酰亚胺己二酸酯(NHS-AA),对胶原溶液进行交联改性.动态流变仪测定结果表明,在f=0.02Hz和25℃时,胶原溶液的弹性模量(G'),粘性模量(G")和复数粘度(η*)分别从未交联时的0.03、0.11Pa和0.76Pa·s增加到22.83、3.36Pa和143.90Pa·s.差示扫描量热分析仪(DSC)测量结果显示,交联后胶原溶液的热变性温度达到42.5℃,比未交联胶原溶液(40.4℃)提高了2.1℃.针对交联后胶原溶液制成的海绵,电泳法(SDS-PAGE)研究表明胶原海绵抗酶降解能力显著增强.%To improve the viscoelastic properties, thermal stability and enzymatic resistance of collagen, collagen solution was cross-linked with a novel cross-linker, N-hydroxysuccinimide activated adipic acid (NHS-AA) , and the effect of NHS-AA on the physicochemical properties of collagen was investigated. The rheological and thermal properties of cross-linked collagen solutions have been investigated by means of dynamic frequency sweeps and differential scanning calorimeter (DSC). At 25℃ , when the concentration of NHS-AA was increased from 0 to 0. 03%, the storage modulus (G'), loss modulus (G"), complex viscosity (η* ) of collagen solution increased from 0.03, 0.11Pa, 0. 76Pa · S to 22. 83, 3. 36Pa, 143. 90Pa · S, respectively. Denaturation temperature ( Td) of cross-linked collagen solution was about 2. 1 ℃ higher than that of uncross-linked collagen solution (40. 4℃ ). The sample solutions were lyophilized to become sponges, the resistance to trypsin digestion of these sponges were observed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The results shown that, after cross-linking, enzymatic resistance were improved significantly.

  18. Characterizing the effects of aligned collagen fibers and ascorbic acid derivatives on behavior of rabbit corneal fibroblasts.

    Science.gov (United States)

    Phu, Donna; Orwin, Elizabeth J

    2009-01-01

    The cornea is responsible for functional optical activity of the mammalian eye, as it must remain transparent in order to focus light onto the retina. Corneal disease is the second leading cause worldwide of vision loss [1]. Human donor tissue transplantation in the cornea is associated with problems such as immunorejection and recurring graft failures [1]. Tissue engineering offers a promising alternative to using human donor tissues in treating corneal diseases. A viable tissue-engineered cornea must be mechanically resilient to protect the fragile intraocular components of the eye, and optically transparent to refract light onto the retina. In the native cornea, transparency is maintained by both the cells in the stromal layer and the high organization of the extracellular matrix (ECM). This study aims to combine the effects of aligned collagen fibers and ascorbic acid derivatives to control corneal fibroblast behavior to not only express the appropriate proteins, but also to deposit aligned, small diameter collagen fibers that resemble the highly organized structure of the natural ECM. Results from this study suggest that the combined effect of an aligned scaffolding material and ascorbic acid supplements can create a cell-matrix construct that both downregulates expression of the light scattering protein a-smooth muscle actin (alpha-sma) and supports an increased number of cell layers.

  19. Thinner Corneas Appear to Have More Striking Effects of Corneal Collagen Crosslinking in Patients with Progressive Keratoconus

    Science.gov (United States)

    Han, Yunfei; Xu, Yanyun; Zhu, Wei; Liu, Yuling; Liu, Zhen; Dou, Xiaoxiao

    2017-01-01

    Purpose. To analyze the outcomes and difference after UVA/riboflavin corneal collagen crosslinking (CXL) in four different corneal thickness groups of patients with progressive keratoconus. Methods. Retrospective study. Eyes with progressive keratoconus after CXL were divided into 4 subgroups as follows: group 1, thinnest corneal thickness (TCT) ≤ 400 µm; group 2, 400 µm corneal topography, TCT, and endothelial cell density were evaluated. Results. The analysis included 123 eyes of 101 patients. At 6 and 12 months after CXL, there was a mean improvement about visual acuity and keratometry values in all patients. There was a reduction in the change of maximum keratometry (Kmax) with the increase of TCT. After 1 year of treatment, it was 3.04 ± 0.75 D in group 1, 2.38 ± 0.51 D in group 2, 1.57 ± 0.35 D in group 3, and 0.31 ± 0.20 D in group 4. Conclusion. CXL is successful in halting the progression of keratoconus and there was a negative linear correlation between TCT and Kmax. Advanced cases of progressive keratoconus seemed to obtain more benefits from the flatting effects of CXL. PMID:28392939

  20. Transepithelial corneal collagen crosslinking for progressive keratoconus: 24-month clinical results.

    Science.gov (United States)

    Caporossi, Aldo; Mazzotta, Cosimo; Paradiso, Anna Lucia; Baiocchi, Stefano; Marigliani, Davide; Caporossi, Tomaso

    2013-08-01

    To assess the clinical results of transepithelial collagen crosslinking (CXL) in patients 26 years and younger with progressive keratoconus suitable for epithelium-off (epi-off) CXL. Department of Ophthalmology, Siena University Hospital, Siena, Italy. Prospective case series. The study included 26 eyes (26 patients) treated by transepithelial (epithelium-on) CXL. The mean age was 22 years (range 11 to 26 years) (10 younger than 18 years; 16 between 19 years and 26 years). Preoperative and postoperative examinations included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, simulated maximum keratometry (K), coma and spherical aberration, and corneal optical coherence tomography optical pachymetry. The solution for transepithelial CXL (Ricrolin TE) comprised riboflavin 0.1%, dextran 15.0%, trometamol (Tris), and ethylenediaminetetraacetic acid. Ultraviolet-A treatment was performed with the Caporossi Baiocchi Mazzotta X Linker Vega at 3 mW/cm(2). After relative improvement in the first 3 to 6 months, the UDVA and CDVA gradually returned to baseline preoperative values. After 12 months of stability, the simulated maximum K value worsened at 24 months. Coma aberration showed no statistically significant change. Spherical aberration increased at 24 months. Pachymetry showed a progressive, statistically significant decrease at 24 months. Fifty percent of pediatric patients were retreated with epi-off CXL due to significant deterioration of all parameters after 12 months of follow-up. Functional results after transepithelial CXL showed keratoconus instability, in particular in pediatric patients 18 years old and younger; there was also functional regression in patients between 19 years and 26 years old after 24 months of follow-up. mentioned. Copyright © 2013 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  1. Ⅰ型胶原吡啶交联终肽在结肠肿瘤诊断中的应用%Investigation of pyridinolne cross linked carboxyterminal telopeptide of type Ⅰ collagen on carcinomaofrectum

    Institute of Scientific and Technical Information of China (English)

    丁敏勇; 梅祎军; 周子花; 毛茅; 李春孟; 王理富

    2013-01-01

    Objective To investigate the clinical usefulness of determination of serum pyridinoline cross linked carboxyterminal telopeptide of type Ⅰ collagen (ICTP) in patients with carcinomaofrectum.Methods 75 malignant carcinomaofrectum patients in group A with 71 primary malignant carcinomaofrecrum patients and 4 metastatic carcinomaofrectum patients were analyzed,43 benign carcinomaofrectum patients were including group B,52 normal persons were chosen in group C,Serum ICTP in everybody was determined by enzyme immunoassay (EIA).Results The serum level of ICTP in group A was (14.84 ±8.49) μg/L,and the serum level of primary malignant carcinomaofrectum,and metastatic tumor of bone in group A were (17.47 ± 10.86) μg/L and (8.14 ± 5.45) μg/L,the serum level of ICTP in group B and C were (6.75 ±3.34) μg/L and (4.68 ±2.91) μg/L.The serum level in group A was significantly higher than that in group B and C (P < 0.05),At the same time,the serum level in primary malignant carcinomaofrectum patients were significantly higher than that of metastatic carcinomaofrectum patients (P < 0.05).Conclusion Serum ICTP was a sensitive and convenient biochemical index which could diagnose and identify carcinomaofrectum.%目的 检测良性结肠肿瘤、恶性结肠肿瘤患者及健康对照组血清中的Ⅰ型胶原吡啶交联终肽(ICTP)活性,探讨ICTP在良恶性结肠肿瘤诊断和鉴别诊断中的价值.方法 选取75例恶性胃肠肿瘤患者,设为A组,其中71例为原发性恶性结肠肿瘤、4例为转移性肿瘤患者,另选43例良性结肠肿瘤患者为B组,同时,设52例同龄健康人为C组,均采用酶免疫测定(EIA)方法测定血清中的ICTP活性.结果 B组患者血清ICTP活性为(6.75 ±3.34) μg/L,C组血清ICTP活性为(4.68±2.91) μg/L,A组患者血清ICTP活性为(14.84±8.49) μg/L,其中,原发性恶性结肠肿瘤患者和转移性结肠肿瘤患者的血清ICTP活性分别为(17.47±10.86) μg/L和(8.14 ±5.45) μg/L.A组中两

  2. Study on the Cross-Linking of Collagen Catalyzed by Transglutaminase in CO2 -Supercritical Fluid Contrasting in Water%谷氨酰胺转氨酶在CO2超临界流体介质与水相介质中对胶原交联作用对比

    Institute of Scientific and Technical Information of China (English)

    吴炼; 程海明; 陈敏; 廖隆理; 贺贤贤; 李志强

    2012-01-01

    The effect of the collagen cross-linking which catalyzed by transglutaminase (Tgase) in CO2-supercritical fluid (SCF-CO2) was investigated by Differential Scanning Calorimeter (DSC) in this paper, and which was contrasted with the cross-linking reaction in water medium. The results indicated that the cross-linking reaction of collagen catalyzed by Tgase in SCF-CO2 could be occurred and the thermal stability of the treated collagen was significantly improved. In addition, comparing with the collagen catalyzed by Tgase in water medium, the thermal denaturation temperature of collagen treated within SCF-CO2 medium was increased 10 to 20 °C. The appropriate conditions of enzymatic reaction in SCF-CO2 as follows: time 2 h, temperature 40°C., Tgase 40-60 Unit/g collagen, pH 6.0 ~ 7.0, pressure 8.0 Mpa.%探讨了CO2超临界流体(SFC - CO2)介质中谷氨酰胺转氨酶(TGase)对胶原的交联作用,且采用差示扫描量热法(DSC)表征胶原交联效果,并与常规水相介质条件下的酶催化胶原交联反应作出对比分析.结果表明:在SCF- CO2介质中TGase催化胶原的交联反应是能发生的,酶处理后胶原的热稳定性得到了显著的提高,且与水相介质条件下酶处理的胶原相比,其热变性温度提高了10 ~20℃.本试验得出TGase在SCF - CO2介质中催化胶原交联反应较适宜的条件为:时间2h、温度40℃、酶用量40 ~60U/g、pH值6.0~7.0、压力8.0 MPa.

  3. The clinical observation of ultraviolet A/riboflavin corneal collagen crosslinking for treatment of progressive keratoconus%紫外光-核黄素角膜交联术治疗进展期圆锥角膜的临床研究

    Institute of Scientific and Technical Information of China (English)

    王山丹; 钱志敏

    2015-01-01

    Objective To investigate clinical efficacy and security of ultroviolet A/riboflavin corneal collagen crosslinking to progressive keratoconus.MethodsTwenty-two eyes with progressive keratoconus were treated by Ultraviolet A/riboflavin corneal collagen crosslinking. To observe the reaction of cornea at postoperative first, third and 7th day,and follow-up 1-6 months,containing corneal conditions, corneal curvature and intraocular pressure. At postoperative 6 month corneal hysteresis and corneal resistance factor was compared with preoperations.Results There were varying degrees of corneal edema at post-operative 1 day, 3 day, 7 day and 1 month. Nerve plexus of corneal stroma decreased. Corneal edema was fading and the number of nerve plexus was restoring gradually at postoperative 3 months. The corneas were clear and the number of nerve plexus returned to the preoperative level. There was statistically significant in comparing corneal hysteresis and corneal resistance factor in pre-operation and post-operation(P<0.01). The change of corneal curvature was unobvious. The intraocular pressure was stable and without unusual changes. The vision improved a line than pre-operation.Conclusion Ultraviolet A/riboflavin corneal collagen cross linking is a secure and effective therapy and stop the development of progressive keratoconus with stable disease.%目的:探讨紫外光-核黄素角膜交联术对进展期圆锥角膜的临床疗效及安全性。方法对22眼进行紫外光-核黄素角膜交联术,观察术后1、3、7d角膜反应,术后1、3、6个月角膜情况,角膜曲率,眼压。第6个月时测量角膜滞后量(CH)和角膜阻力因子量(CRF)与术前对比。结果术后1、3、7d,1个月角膜基质有不同程度水肿,角膜基质神经丛减少,术后3个月水肿消退,神经丛数量逐渐恢复,术后6个月角膜透明,神经丛数量恢复到术前水平。手术前后角膜强度CH值和CRF值比

  4. Electrospinning formaldehyde cross-linked zein solutions

    Science.gov (United States)

    In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as the cross-linking reagent before spinning. The cross-linking reaction was carried out in either acetic acid or ethanolic-HCl where the amount of cross-linking reagent was between 1 and...

  5. [Predictive factors for visual outcome after corneal collagen crosslinking treatment in progressive keratoconus: One-year refractive and topographic results].

    Science.gov (United States)

    De Angelis, F; Rateau, J; Destrieux, C; Patat, F; Pisella, P-J

    2015-09-01

    To assess the effects of preoperative patient characteristics on clinical outcomes of corneal collagen crosslinking (CXL) in patients with progressive keratoconus. Fifty-four eyes of 41 patients underwent CXL for progressive keratoconus between June 2011 and December 2012. Corneal topography (Orbscan(®)) was assessed at 1, 3, and 6 months and 1 year after CXL treatment and compared with preoperative data. A significant improvement in 1-year postoperative best-corrected visual acuity (BCVA) (0.16±0.21 LogMar preoperatively versus 0.09±0.16 LogMar postoperatively, P=0.007) and in 3mm topographic central irregular astigmatism (P=0.04) was demonstrated with CXL. No significant change was noted for refractive astigmatism (P=0.69), or for 1-year postoperative Kmax (48.4 D±4.1 at baseline versus 48.5 D±4.1 postoperatively, P=0.46). Predictive factors for BVCA improvement were low preoperative BCVA, high refractive astigmatism and advanced keratoconus. Predictive factors for stability of postoperative Kmax values were early keratoconus, and central cone ("nipple" morphology of the cone mainly located in the central 3mm of the cornea). This retrospective study confirms the efficacy of CXL for progressive keratoconus, from a refractive as well as topographic standpoint. While cone localization or its eccentricity seems to explain the variability of CXL efficacy reported in the literature, cone severity appears to be the main predictive factor for a lack of topographic stability after CXL treatment but must be weighted by the preferential localization of the cone (3 or 5mm central corneal zone). Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  6. Effects of Corneal Collagen Crosslinking on Confocal Microscopic Findings and Tear Indices in Patients with Progressive Keratoconus

    Science.gov (United States)

    Zare, Mohammad Ali; Mazloumi, Mehdi; Farajipour, Hasan; Hoseini, Bagher; Fallah, Mohammad R.; Mahrjerdi, Hadi Z.; Abtahi, Mohammad-Ali; Abtahi, Seyed-Hossein

    2016-01-01

    Background: To evaluate any change in tear indices and confocal microscopic findings after corneal collagen crosslinking (CXL) in patients with progressive keratoconus. Methods: Thirty-two consecutive eyes from 23 patients having progressive keratoconus were enrolled in this prospective, interventional cohort study. The standard crosslinking surgery was performed for all patients. Visual, refractive, and topographic evaluations were done before and at 6 months after surgery. Tear function tests and confocal microscopic examination were performed before and at 1 month and 6 months after the procedure. Results: There was no significant change in Schirmer-1 test results and tear osmolarity at 1 month and 6 months after CXL. Using confocal microscopy, all eyes showed reduced or absent subepithelial nerve plexus. Differences in basal epithelial cell density, epithelial mean cell area, and keratocyte density in anterior and middle stroma and endothelial cell pleomorphism were all significant at 1 month and 6 months after CXL (P < 0.05). No significant change was noted in endothelial cell count and their polymegathism at 6 months follow-up. Significant improvement was noted in uncorrected visual acuity, best corrected visual acuity, flattest corneal meridian (K2), and maximum keratometry in Pentacam (Kmax) after 6 months of the procedure. Conclusions: While CXL would have no effect on tear indices and endothelial cell count, it can cause a significant reduction in subepithelial nerve plexus and significant alterations in epithelial cell density in the anterior and middle stroma. PMID:28123695

  7. Corneal haze and visual outcome after collagen crosslinking for keratoconus: A comparison between total epithelium off and partial epithelial removal methods

    Directory of Open Access Journals (Sweden)

    Hasan Razmjoo

    2014-01-01

    Full Text Available Background: Keratoconus is an asymmetric, bilateral, progressive noninflammatory ectasia of the cornea that affects approximately 1 in 2000 of the general population. This may cause a significant negative impact on quality of life. Corneal collagen crosslinking (CXL is one of the recently introduced methods that have been used to decrease the progression of keratoconus, in particular, as well as other corneal-thinning processes. Materials and Methods: A total of 44 keratoconic eyes of 22 patients were enrolled in this randomized prospective study, after obtaining informed consent. In the first group, the corneal epithelium were totally removed and in the second group, the central 3 mm of epithelium was kept intact and partial removal was performed. After collagen crosslinking in both groups, comprehensive ophthalmologic examination was performed on all patients before and 6 months after the surgery. This article is registered at www.clinicaltrial.gov with registration number NCT01809977. Results: The difference between the two groups was not statistically significant regarding postoperative corneal haziness, refraction, and visual acuity (P > 0.05. However, comparison of pre- and postoperative parameters within each group revealed that total removal of the cornea has resulted in significant improvement of K-max (P value: 0.01 and Q-value (P value: 0.009; while eyes in partial removal group had better improvement of corrected vision (P value: 0.006. Both methods had significant and similar increase in optical corneal density (P < 0.0001. Conclusion: In our study, keeping the central corneal epithelium intact was not beneficial for decreasing corneal haziness, however, this method caused better improvement in corrected vision. Total epithelium off technique resulted in better improvement of K-max and Q-value.

  8. Transepithelial corneal collagen crosslinking for keratoconus: qualitative investigation by in vivo HRT II confocal analysis.

    Science.gov (United States)

    Caporossi, Aldo; Mazzotta, Cosimo; Baiocchi, Stefano; Caporossi, Tomaso; Paradiso, Anna Lucia

    2012-01-01

    This was a qualitative investigation of corneal microstructural modifications in keratoconic patients undergoing experimental transepithelial crosslinking (TE CXL). Ten patients with keratoconus intolerant to gas-permeable rigid contact lenses were enrolled. Corneal thickness was in the range 350-390 µm at the thinnest point measured by Visante AC optical coherence tomography system (Zeiss, Jena, Germany). All patients underwent TE CXL with 0.1% riboflavin-15% dextran solution supplemented with TRIS plus sodium EDTA (Ricrolin TE, Sooft Italia) according to Siena protocol. In vivo Heidelberg retinal tomograph II laser scanning confocal analysis (Rostock Cornea Module, Heidelberg, Germany) was performed with the following follow-up: preoperative and postoperative assessments at 1, 3, and 6 months. The following morphologic parameters were evaluated: epithelium, subepithelial, and anterior stroma nerve plexi, keratocytes apoptosis, stromal changes, and the endothelium. After TE CXL, epithelial cells showed apoptosis, with mosaic alterations gradually disappearing. Keratocytes apoptosis was variable, superficial, and uneven, with a maximum depth of penetration at about 140 µm, measured from the surface of epithelium. Treatment respected subepithelial and stromal nerves that did not disappear. No variation in cell count or endothelial mosaic was observed. In vivo confocal analysis of corneal modifications induced by TE CXL showed a limited apoptotic affect of this treatment, about one-third of classic epi-off crosslinking procedure. The TE CXL respected sub-basal and anterior stroma nerve fibers, resulting safe for corneal endothelium. According to limited penetration, its mid- to long-term efficacy needs to be determined in different clinical settings related to patient age and keratoconus progression.

  9. Combined treatment with flap amputation, phototherapeutic keratectomy, and collagen crosslinking in severe intractable post-LASIK atypical mycobacterial infection with corneal melt.

    Science.gov (United States)

    Kymionis, George D; Kankariya, Vardhaman P; Kontadakis, Georgios A

    2012-04-01

    A 23-year-old woman was referred for management of intractable post-laser in situ keratomileusis (LASIK) keratitis due to atypical mycobacteria in the left eye. Corrected distance visual acuity was 20/20 in the right eye and counting fingers at 3 meters in the left eye. Slitlamp examination revealed multiple infiltrates in the flap interface and severe corneal stromal melting with thinning. Despite maximum antibiotic therapy for 7 days, the keratitis continued to worsen. A penetrating keratoplasty (PKP) was scheduled. While waiting for a corneal graft, corneal collagen crosslinking (CXL) with riboflavin and ultraviolet-A was proposed as an alternative treatment. Flap amputation and limited phototherapeutic keratotomy (PTK) (10 μm) were also performed. One week postoperatively, all infiltrates and stromal edema had resolved. At 3 months, the uncorrected distance visual acuity improved to 20/35. Corneal crosslinking after flap amputation and limited PTK was an effective treatment for severe intractable post-LASIK keratitis with corneal melting and obviated PKP.

  10. Epithelium-off photochemical corneal collagen cross-linkage using riboflavin and ultraviolet a for keratoconus and keratectasia: a systematic review and meta-analysis.

    Science.gov (United States)

    Craig, Joyce A; Mahon, James; Yellowlees, Ann; Barata, Teresa; Glanville, Julie; Arber, Mick; Mandava, Lakshmi; Powell, John; Figueiredo, Francisco

    2014-07-01

    This report presents the results of a systematic review and meta-analyses of studies on epithelium-off photochemical corneal collagen cross-linkage for the management of keratoconus and secondary ectasia. The literature search identified 3,400 records of which 49 were considered for inclusion in the meta-analyses. Eight papers reported 4 unique randomized controlled trials, 29 studies were prospective, and 12 were retrospective studies. The majority of the studies (39/49) were graded as very low quality evidence. Twenty-six studies described adverse events and were included in the safety analysis. Meta-analyses are presented for changes in four outcomes: visual acuity, topography, refraction and astigmatism, and central corneal thickness. Statistically significant improvements were found in all efficacy outcomes at 12 months after the operation. Common side effects were pain, corneal edema, and corneal haze, which resolved usually within a few days after the procedure. The remaining uncertainty is duration of benefit to establish the procedure's potential benefit in avoiding or delaying disease progression and possibly reducing the need for corneal transplantation.

  11. New insights into the pros and cons of cross-linking decellularized bioartificial organs.

    Science.gov (United States)

    Hussein, Kamal H; Park, Kyung-Mee; Lee, Yun-Suk; Woo, Jae-Seok; Kang, Byung-Jae; Choi, Ki-Young; Kang, Kyung-Sun; Woo, Heung-Myong

    2017-01-25

    ABSTRACTDecellularization is an attractive method for scaffold designing in regenerative medicine. The resulting extracellular matrix (ECM) consists of structural proteins such as collagen and elastin, growth factors, and glycosaminoglycans, which can direct site-appropriate remodeling after in vivo implantation. Mainly, collagen and elastin of ECM are exposed to the enzymatic biodegradation in the host. To control the biodegradation process, treatment of decellularized tissue by a cross-linking agent is required. Cross-linking also reduces antigenicity and increases the storage properties. Cross-linkers should be nontoxic, with the ability to preserve the ECM components, especially glycosaminoglycans and associated growth factors for retention of scaffold bioactivity. In this review, we describe the different cross-linking agents and methods of evaluation of cross-linking efficiency.

  12. Chemical cross-linking of Chlamydia trachomatis

    DEFF Research Database (Denmark)

    Birkelund, Svend; Lundemose, AG; Christiansen, Gunna

    1988-01-01

    Purified elementary bodies (EBs) of Chlamydia trachomatis serovar L2 were analyzed by chemical cross-linking with disuccinimidyl selenodipropionate. The effect of the cross-linking was analyzed by immunoblotting sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated components which...

  13. Effect of ultraviolet A (UVA) plus riboflavin induced collagen cross-linking on biomechanical properties of the sclera in guinea pigs%紫外光-核黄素交联法对豚鼠巩膜生物力学特性的影响

    Institute of Scientific and Technical Information of China (English)

    吕雅平; 周浩; 夏文涛; 褚仁远; 周行涛; 戴锦晖

    2012-01-01

    目的 探索紫外光-核黄素交联法对巩膜织张力和强度的影响.方法 交联组和对照组皆选右眼为实验眼,交联组采用波长为(370±5)nm、辐射强度定为3.0 mW/cm2的紫外线和0.1%核黄素为光敏剂对豚鼠赤道部巩膜面进行胶原交联,对照组不进行交联处理.术后一个月取交联组交联区巩膜条带和对照组相应区域的巩膜条带,进行生物力学测试,并对眼球各组织进行HE染色光镜和透射电镜检测.结果 交联组巩膜的生物力学特性增强,赤道部交联组巩膜试件断裂时的极限应力增加了147%,弹性模量显著增加了193%,极限应变降低了21.9%;后极部交联组巩膜试件断裂时的极限应力增加了108%,弹性模量显著增加了191%,极限应变降低了40.42%.HE染色光镜检查结果显示形态学无病理改变,透射电镜结果显示交联组交联区的巩膜成纤维细胞增生活跃.结论 紫外光-核黄素交联法可以有效地提高巩膜的生物力学特性,增强巩膜组织的张力和强度,有望作为治疗高度病理性近视的一种方法.%Objective To study the effect of collagen cross-linking induced by riboflavin and ultraviolet A ( UVA ) on biomechanical properties of the sclera in guinea pigs. Methods The changes of biomechanical properties of the sclera induced by riboflavin and ultraviolet A ( UVA)-induced collagen crosslinking were examined in ten guinea pigs and compared with those of ten non-treated guinea pigs. Histological and ultrastructural changes of the sclera were examined to evaluate the side-effects. Results At one month after the UVA plus riboflavin treatment, the ultimate stress increased by 147% , elastic modulus increased by 193% , ultimate strain reduced by 21.9% in the equatorial sclera and significantly changed by 108% , 191% , 40.42% in the posterior sclera, respectively. Light microscopy showed no pathological alterations. Transmission electron microscopy showed active

  14. Corneal Resistance to Keratolysis After Collagen Crosslinking With Rose Bengal and Green Light.

    Science.gov (United States)

    Fadlallah, Ali; Zhu, Hong; Arafat, Samer; Kochevar, Irene; Melki, Samir; Ciolino, Joseph B

    2016-12-01

    The purpose of this study was to evaluate the resistance to degradation by collagenase A of corneas that have been crosslinked with Rose Bengal and green light (RGX). The ex vivo crosslinking procedure was performed on enucleated rabbit corneas. Corneas were deepithelialized after applying 30% alcohol. Corneas were stained with Rose Bengal (RB, 0.1%) for 2 minutes and then exposed to green light (532 nm) at 0.25 W/cm2 for times to deliver doses of 50, 100, 150, or 200 J/cm2 (n = 5 per group). Five corneas were pretreated with riboflavin solution (0.1% riboflavin) for 15 minutes and irradiated with ultraviolet A (UVA) light (370 nm, 3 mW/cm2) for 30 minutes. Five corneas underwent only de-epithelialization and were otherwise untreated. Five corneas were stained with RB without light exposure. The central corneas of each group was removed with a 8.5-mm trephine and incubated at 37°C in 0.3% collagenase A solution. Time to dissolution of each cornea was compared across treatments. Corneas treated with RGX were treated with light fluences of 50, 100, 150, and 200 J/cm2; these corneas dissolved completely at 8.3 ± 1.2, 11.1 ± 1.4, 12.4 ± 1.7, and 15.7 ± 1.8 hours, respectively. Corneas treated by riboflavin and UVA light dissolved at 15.7 ± 1.7 hours, and nontreated corneas dissolved at 6.1 ± 1.3 hours. Corneas treated with only RB (no green light) dissolved at 9.3 ± 1.7 hours. Compared with the untreated corneas, all of the RB groups and the riboflavin-UVA-treated group of corneas degraded statistically significantly slower than untreated corneas (P < 0.05). Crosslinking with RGX increased corneal resistance to digestion by collagenase comparable to that produced by riboflavin and UVA treatment.

  15. Collagen based film with well epithelial and stromal regeneration as corneal repair materials: Improving mechanical property by crosslinking with citric acid

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xuan; Liu, Yang; Li, Weichang; Long, Kai; Wang, Lin; Liu, Sa; Wang, Yingjun [School of Materials Science and Engineering, South China University of Technology, Guangzhou (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou (China); Ren, Li, E-mail: psliren@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou (China); National Engineering Research Center for Tissue Restoration and Reconstruction, Guangzhou (China)

    2015-10-01

    Corneal disease can lead to vision loss. It has become the second greatest cause of blindness in the world, and keratoplasty is considered as an effective treatment method. This paper presents the crosslinked collagen (Col)–citric acid (CA) films developed by making use of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The results showed that the Col–CA films had necessary optical performance, water content. The collagenase resistance of CA crosslinked films was superior to that of EDC crosslinked films. And CA5 film (Col:CA:EDC:NHS = 60:3:10:10) had the best mechanical properties. Cell experiments showed that CA5 film was non-cytotoxic and human corneal epithelial cells could proliferate well on the films. Lamellar keratoplasty showed that the CA5 film could be sutured in the rabbit eyes and was epithelialized completely in about 10 days, and the transparency was restored quickly in 30 ± 5 days. No inflammation and corneal neovascularization were observed at 6 months. Corneal stroma had been repaired; stromal cells and neo-stroma could be seen in the area of operation from the hematoxylin–eosin stained histologic sections and anterior segment optical coherence tomography images. These results indicated that Col–CA films were highly promising biomaterials that could be used in corneal tissue engineering and a variety of other tissue engineering applications. - Highlights: • Adding different amounts of citric acid could change the properties of films. • The crosslinked films had better mechanical property than non-modified films. • Crosslinked collagen–citric acid films could tolerate suture during operation. • The films showed good ability of epithelial and stromal repair.

  16. Effect of cross-linking with riboflavin and ultraviolet A on the chemical bonds and ultrastructure of human sclera

    Science.gov (United States)

    Jung, Gyeong-Bok; Lee, Hui-Jae; Kim, Ji-Hye; Lim, Jin Ik; Choi, Samjin; Jin, Kyung-Hyun; Park, Hun-Kuk

    2011-12-01

    This study examined the effect of the cross-linking with riboflavin-ultraviolet A (UVA) irradiation on the chemical bonds and ultrastructural changes of human sclera tissues using Raman spectroscopy and atomic force microscopy (AFM). Raman spectroscopy of the normal and cross-linked human sclera tissue revealed different types of the riboflavin-UVA and collagen interactions, which could be identified from their unique peaks, intensity, and shape. Raman spectroscopy can prove to be a powerful tool for examining the chemical bond of collagenous tissues at the molecular level. After riboflavin-UVA treatment, unlike a regular parallel arrangement of normal collagen fibrils, the AFM image revealed interlocking arrangements of collagen fibrils. The observed changes in the surface topography of the collagen fibrils, as well as in their chemical bonds in the sclera tissue, support the formation of interfibrilar cross-links in sclera tissues.

  17. Cross-linking chemistry of squid beak.

    Science.gov (United States)

    Miserez, Ali; Rubin, Daniel; Waite, J Herbert

    2010-12-03

    In stark contrast to most aggressive predators, Dosidicus gigas (jumbo squids) do not use minerals in their powerful mouthparts known as beaks. Their beaks instead consist of a highly sclerotized chitinous composite with incremental hydration from the tip to the base. We previously reported l-3,4-dihydroxyphenylalanine (dopa)-histidine (dopa-His) as an important covalent cross-link providing mechanical strengthening to the beak material. Here, we present a more complete characterization of the sclerotization chemistry and describe additional cross-links from D. gigas beak. All cross-links presented in this report share common building blocks, a family of di-, tri-, and tetra-histidine-catecholic adducts, that were separated by affinity chromatography and high performance liquid chromatography (HPLC) and identified by tandem mass spectroscopy and proton nuclear magnetic resonance ((1)H NMR). The data provide additional insights into the unusually high cross-link density found in mature beaks. Furthermore, we propose both a low molecular weight catechol, and peptidyl-dopa, to be sclerotization agents of squid beak. This appears to represent a new strategy for forming hard tissue in animals. The interplay between covalent cross-linking and dehydration on the graded properties of the beaks is discussed.

  18. Cross-linked structure of network evolution

    Science.gov (United States)

    Bassett, Danielle S.; Wymbs, Nicholas F.; Porter, Mason A.; Mucha, Peter J.; Grafton, Scott T.

    2014-03-01

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

  19. Cross-linked structure of network evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, Danielle S., E-mail: dsb@seas.upenn.edu [Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Sage Center for the Study of the Mind, University of California, Santa Barbara, California 93106 (United States); Wymbs, Nicholas F.; Grafton, Scott T. [Department of Psychology and UCSB Brain Imaging Center, University of California, Santa Barbara, California 93106 (United States); Porter, Mason A. [Oxford Centre for Industrial and Applied Mathematics, Mathematical Institute, University of Oxford, Oxford OX2 6GG (United Kingdom); CABDyN Complexity Centre, University of Oxford, Oxford, OX1 1HP (United Kingdom); Mucha, Peter J. [Carolina Center for Interdisciplinary Applied Mathematics, Department of Mathematics, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

    2014-03-15

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

  20. Tissue-specific effects of aldose reductase inhibition on fluorescence and cross-linking of extracellular matrix in chronic galactosemia. Relationship to pentosidine cross-links.

    Science.gov (United States)

    Richard, S; Tamas, C; Sell, D R; Monnier, V M

    1991-08-01

    Chronic experimental hyperglycemia mediated by galactose has been shown to induce browning and cross-linking of rat tail tendon collagen that could be duplicated in vitro by nonenzymatic galactosylation. To investigate the nature of these changes, Sprague-Dawley rats were placed on a 33% galactose diet without and with sorbinil for 6 and 12 mo. Collagen-linked fluorescence and pentosidine cross-links increased with age and galactosemia in tail tendons (P less than 0.001) and skin but were essentially unresponsive to aldose reductase inhibition (ARI). In contrast, tendon breaking time in urea, a likely parameter of cross-linking, was markedly improved (P less than 0.001) by ARI. Fluorescence that was inhibited by sorbinil treatment was increased in pepsin and proteinase K digest of aortic tissue from galactosemic rats (P less than 0.001), but impaired enzymatic digestibility was not observed. Systolic blood pressure as potential consequence of aortic stiffening was not increased in galactosemia. These data suggest that fluorescence in skin and tendon might be in part due to advanced glycosylation and pentosidine formation because these were not decreased by ARI. However, they also suggest that nonfluorescent cross-links may also be forming because, in contrast to fluorescence, tail tendon breaking time was partly corrected by ARI. Thus, it appears that extracellular matrix changes in chronic galactosemia are complex, being partly attributable to advanced glycosylation and partly to polyol-pathway activation.

  1. Method of preparing cross-linked enzyme particles

    NARCIS (Netherlands)

    Mateo, C.; Van Langen, L.M.; Van Rantwijk, F.

    2004-01-01

    The invention relates to a method of preparing cross-linked enzyme particles using a cross-linking agent. According to the invention, the enzyme particles are formed and subsequently cross-linked using a cross-linking agent having at least n reactive groups where N>=3 and a molecular weight of

  2. Method of preparing cross-linked enzyme particles

    NARCIS (Netherlands)

    Mateo, C.; Van Langen, L.M.; Van Rantwijk, F.

    2004-01-01

    The invention relates to a method of preparing cross-linked enzyme particles using a cross-linking agent. According to the invention, the enzyme particles are formed and subsequently cross-linked using a cross-linking agent having at least n reactive groups where N>=3 and a molecular weight of >2,00

  3. Sterile Keratitis following Collagen Crosslinking

    Science.gov (United States)

    Javadi, Mohammad-Ali; Feizi, Sepehr

    2014-01-01

    Purpose: To report a keratoconic eye that developed severe sterile keratitis and corneal scar after collagen crosslinking necessitating corneal transplantation. Case Report: A 26-year-old man with progressive keratoconus underwent collagen crosslinking and presented with severe keratitis 72 hours after the procedure. The initial impression was infectious corneal ulcer and a fortified antibiotic regimen was administered. However, the clinical course and confocal microscopy results prompted a diagnosis of sterile keratitis. The eye developed severe corneal scars leading to reduced visual acuity and necessitating corneal transplantation. Conclusion: Sterile keratitis may develop after collagen crosslinking resulting in profound visual loss leading to corneal transplantation. PMID:25709779

  4. Effects of alginate hydrogel cross-linking density on mechanical and biological behaviors for tissue engineering.

    Science.gov (United States)

    Jang, Jinah; Seol, Young-Joon; Kim, Hyeon Ji; Kundu, Joydip; Kim, Sung Won; Cho, Dong-Woo

    2014-09-01

    An effective cross-linking of alginate gel was made through reaction with calcium carbonate (CaCO3). We used human chondrocytes as a model cell to study the effects of cross-linking density. Three different pore size ranges of cross-linked alginate hydrogels were fabricated. The morphological, mechanical, and rheological properties of various alginate hydrogels were characterized and responses of biosynthesis of cells encapsulated in each gel to the variation in cross-linking density were investigated. Desired outer shape of structure was maintained when the alginate solution was cross-linked with the applied method. The properties of alginate hydrogel could be tailored through applying various concentrations of CaCO3. The rate of synthesized GAGs and collagens was significantly higher in human chondrocytes encapsulated in the smaller pore structure than that in the larger pore structure. The expression of chondrogenic markers, including collagen type II and aggrecan, was enhanced in the smaller pore structure. It was found that proper structural morphology is a critical factor to enhance the performance and tissue regeneration.

  5. The cross linking of EPDM and NBR rubber

    Directory of Open Access Journals (Sweden)

    Samardžija-Jovanović Suzana

    2005-01-01

    Full Text Available In the process of macromolecule cross linking, the choice of type and quantity of the components and the experimental conditions are important to obtain the new cross linked materials with better mechanical and chemical characteristics. The cross linking method depends on the rubber type and structure. Intermolecular cross linking results in the formation elastomer network. The basis of the cross linking process, between ethylene propylene diene rubber (EPDM and acrylonitrile butadiene rubber (NBR, is a chemical reaction. Fillers and other additives are present in different mass ratios in the material. The exploitation properties of the cross linked materials depend on the quantity of additive in the cross linked systems.

  6. Glutaraldehyde Cross-Linking of TendonMechanical Effects at the Level of the Tendon Fascicle and Fibril

    DEFF Research Database (Denmark)

    Hansen, P.; Svensson, R.B.; Aagaard, P.;

    2009-01-01

    allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from 8 MPa to 39 MPa. The mechanical effects of glutaraldehyde at the tendon fibril level......Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy...... were examined by atomic force microscopy. Peak forces increased from 1379 to 2622 pN while an extended Hertz fit of force-indentation data showed a 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross-linking on the tensile properties of a single collagen fibril...

  7. Characterization of Cross-Linked Lipase Aggregates

    DEFF Research Database (Denmark)

    Prabhavathi Devi, Bethala Lakshmi Anu; Guo, Zheng; Xu, Xuebing

    2009-01-01

    Commercially available microbial lipases from different sources were immobilized as cross-linked enzyme aggregates (CLEAs) using different precipitants and glutaraldehyde as cross-linkers. These CLEAs were assayed based on esterification between lauric acid and n-propanol in solvent-free systems...... change upon CLEA formation. This work presents a characterization of CLEAs based on an esterification activity assay, which is useful for exploring the synthetic application potential of CLEA technology with favorable perspectives....

  8. Thermal Analyse sof Cross-Linked Polyethylene

    Directory of Open Access Journals (Sweden)

    Radek Polansky

    2007-01-01

    Full Text Available The paper summarizes results obtained during the structural analyses measurements (Differential Scanning Calorimetry DSC, Thermogravimetry TG, Thermomechanical analysis TMA and Fourier transform infrared spectroscopy FT-IR. The samples of cross-linked polyethylene cable insulation were tested via these analyses. The DSC and TG were carried out using simultaneous thermal analyzer TA Instruments SDT Q600 with connection of Fourier transform infrared spectrometer Nicolet 380. Thermomechanical analysis was carried out by TMA Q400EM TA Instruments apparatus.

  9. Human pluripotent stem cell-derived limbal epithelial stem cells on bioengineered matrices for corneal reconstruction.

    Science.gov (United States)

    Mikhailova, Alexandra; Ilmarinen, Tanja; Ratnayake, Anjula; Petrovski, Goran; Uusitalo, Hannu; Skottman, Heli; Rafat, Mehrdad

    2016-05-01

    Corneal epithelium is renewed by limbal epithelial stem cells (LESCs), a type of tissue-specific stem cells located in the limbal palisades of Vogt at the corneo-scleral junction. Acute trauma or inflammatory disorders of the ocular surface can destroy these stem cells, leading to limbal stem cell deficiency (LSCD) - a painful and vision-threatening condition. Treating these disorders is often challenging and complex, especially in bilateral cases with extensive damage. Human pluripotent stem cells (hPSCs) provide new opportunities for corneal reconstruction using cell-based therapy. Here, we investigated the use of hPSC-derived LESC-like cells on bioengineered collagen matrices in serum-free conditions, aiming for clinical applications to reconstruct the corneal epithelium and partially replace the damaged stroma. Differentiation of hPSCs towards LESC-like cells was directed using small-molecule induction followed by maturation in corneal epithelium culture medium. After four to five weeks of culture, differentiated cells were seeded onto bioengineered matrices fabricated as transparent membranes of uniform thickness, using medical-grade porcine collagen type I and a hybrid cross-linking technology. The bioengineered matrices were fully transparent, with high water content and swelling capacity, and parallel lamellar microstructure. Cell proliferation of hPSC-LESCs was significantly higher on bioengineered matrices than on collagen-coated control wells after two weeks of culture, and LESC markers p63 and cytokeratin 15, along with proliferation marker Ki67 were expressed even after 30 days in culture. Overall, hPSC-LESCs retained their capacity to self-renew and proliferate, but were also able to terminally differentiate upon stimulation, as suggested by protein expression of cytokeratins 3 and 12. We propose the use of bioengineered collagen matrices as carriers for the clinically-relevant hPSC-derived LESC-like cells, as a novel tissue engineering approach for

  10. Higher number of pentosidine cross-links induced by ribose does not alter tissue stiffness of cancellous bone

    Energy Technology Data Exchange (ETDEWEB)

    Willems, Nop M.B.K., E-mail: n.willems@acta.nl [Dept. of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Langenbach, Geerling E.J. [Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Stoop, Reinout [Dept. of Metabolic Health Research, TNO, P.O. Box 2215, 2301 CE Leiden (Netherlands); Toonder, Jaap M.J. den [Dept. of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Mulder, Lars [Dept. of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Zentner, Andrej [Dept. of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Everts, Vincent [Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands)

    2014-09-01

    The role of mature collagen cross-links, pentosidine (Pen) cross-links in particular, in the micromechanical properties of cancellous bone is unknown. The aim of this study was to examine nonenzymatic glycation effects on tissue stiffness of demineralized and non-demineralized cancellous bone. A total of 60 bone samples were derived from mandibular condyles of six pigs, and assigned to either control or experimental groups. Experimental handling included incubation in phosphate buffered saline alone or with 0.2 M ribose at 37 °C for 15 days and, in some of the samples, subsequent complete demineralization of the sample surface using 8% EDTA. Before and after experimental handling, bone microarchitecture and tissue mineral density were examined by means of microcomputed tomography. After experimental handling, the collagen content and the number of Pen, hydroxylysylpyridinoline (HP), and lysylpyridinoline (LP) cross-links were estimated using HPLC, and tissue stiffness was assessed by means of nanoindentation. Ribose treatment caused an up to 300-fold increase in the number of Pen cross-links compared to nonribose-incubated controls, but did not affect the number of HP and LP cross-links. This increase in the number of Pen cross-links had no influence on tissue stiffness of both demineralized and nondemineralized bone samples. These findings suggest that Pen cross-links do not play a significant role in bone tissue stiffness. - Highlights: • The assessment of effects of glycation in bone using HPLC, microCT, and nanoindentation • Ribose incubation: 300‐fold increase in the number of pentosidine cross-links • 300‐fold increase in the number of pentosidine cross-links: no changes in bone tissue stiffness.

  11. The Cross - linking reaction of HEC

    Institute of Scientific and Technical Information of China (English)

    XIONG Jian; YE Jun; XUAN Zhiyong; XIE Guohui

    2001-01-01

    @@ Cellulose ethers are important components for light industries such as food and papermaking industries. Its modification research is a frontline science to widen their uses and realize their industrialization. The target of modification is to make high production value, low input and meet the needs better in industries. O-(2-hydroxyethl) cellulose (HEC) is one of the best-known cellulose ether derivatives. It is mainly used as thickeners, dispersants, adhesives, extenders, and films because of its water solubility and gel-forming properties. The present research,by means of cross-linking, we study the influence on HEC about rheological behavior.This will provide a feasible scheme for cellulose ethers modification.

  12. The Cross - linking reaction of HEC

    Institute of Scientific and Technical Information of China (English)

    XIONG; Jian

    2001-01-01

    Cellulose ethers are important components for light industries such as food and papermaking industries. Its modification research is a frontline science to widen their uses and realize their industrialization. The target of modification is to make high production value, low input and meet the needs better in industries.  O-(2-hydroxyethl) cellulose (HEC) is one of the best-known cellulose ether derivatives. It is mainly used as thickeners, dispersants, adhesives, extenders, and films because of its water solubility and gel-forming properties. The present research,by means of cross-linking, we study the influence on HEC about rheological behavior.This will provide a feasible scheme for cellulose ethers modification.……

  13. Triple combination of siRNAs targeting TGFβ1, TGFβR2, and CTGF enhances reduction of collagen I and smooth muscle actin in corneal fibroblasts.

    Science.gov (United States)

    Sriram, Sriniwas; Robinson, Paulette; Pi, Liya; Lewin, Alfred S; Schultz, Gregory

    2013-12-17

    Transforming growth factor β1 (TGFβ1), TGFβ receptor (TGFβR2), and connective tissue growth factor (CTGF) are key regulators of fibrosis in the cornea and in other tissues, including liver, skin, and kidney. We developed an antifibrotic treatment targeting these three critical scarring genes by using a combination of small interfering RNAs (siRNAs) and assessed its effect on downstream scarring genes, collagen I, and α smooth muscle actin (SMA). Up to six individual siRNAs for each of the three target gene mRNAs were transfected into cultures of rabbit corneal fibroblasts at concentrations from 15 to 90 nM. The knockdown of target gene proteins was measured by ELISA, and the two most effective siRNAs were tested in dual combinations. Knockdown percentages of both individual and dual siRNA combinations were analyzed for synergy by using combination index to predict "effective" and "ineffective" triple siRNA combinations. Effects of both triple siRNA combinations on target and downstream mRNAs were measured by using quantitative RT-PCR, and levels of SMA protein were assessed by immunohistochemistry. Single and dual siRNA combinations produced a wide range of protein knockdown of target genes (5%-80%). The effective triple siRNA combination significantly reduced mRNA levels of target genes (>80%) and downstream scarring genes (>85%), and of SMA protein (>95%), and significantly reduced cell migration without reducing cell viability. Simultaneous targeting of TGFβ1, TGFβR2, and CTGF genes by effective triple siRNA combination produced high knockdown of target and downstream scarring genes without cell toxicity, which may have clinical applications in reducing corneal fibrosis and scarring in other tissues.

  14. Contact Lens Visual Rehabilitation in Keratoconus and Corneal Keratoplasty

    Directory of Open Access Journals (Sweden)

    Yelda Ozkurt

    2012-01-01

    Full Text Available Keratoconus is the most common corneal distrophy. It’s a noninflammatory progressive thinning process that leads to conical ectasia of the cornea, causing high myopia and astigmatism. Many treatment choices include spectacle correction and contact lens wear, collagen cross linking, intracorneal ring segments implantation and finally keratoplasty. Contact lenses are commonly used to reduce astigmatism and increase vision. There are various types of lenses are available. We reviewed soft contact lenses, rigid gas permeable contact lenses, piggyback contact lenses, hybrid contact lenses and scleral-semiscleral contact lenses in keratoconus management. The surgical option is keratoplasty, but even after sutur removal, high astigmatism may stil exists. Therefore, contact lens is an adequate treatment option to correct astigmatism after keratoplasty.

  15. Cross-link guided molecular modeling with ROSETTA.

    Directory of Open Access Journals (Sweden)

    Abdullah Kahraman

    Full Text Available Chemical cross-links identified by mass spectrometry generate distance restraints that reveal low-resolution structural information on proteins and protein complexes. The technology to reliably generate such data has become mature and robust enough to shift the focus to the question of how these distance restraints can be best integrated into molecular modeling calculations. Here, we introduce three workflows for incorporating distance restraints generated by chemical cross-linking and mass spectrometry into ROSETTA protocols for comparative and de novo modeling and protein-protein docking. We demonstrate that the cross-link validation and visualization software Xwalk facilitates successful cross-link data integration. Besides the protocols we introduce XLdb, a database of chemical cross-links from 14 different publications with 506 intra-protein and 62 inter-protein cross-links, where each cross-link can be mapped on an experimental structure from the Protein Data Bank. Finally, we demonstrate on a protein-protein docking reference data set the impact of virtual cross-links on protein docking calculations and show that an inter-protein cross-link can reduce on average the RMSD of a docking prediction by 5.0 Å. The methods and results presented here provide guidelines for the effective integration of chemical cross-link data in molecular modeling calculations and should advance the structural analysis of particularly large and transient protein complexes via hybrid structural biology methods.

  16. Hyperopic correction: clinical validation with epithelium-on and epithelium-off protocols, using variable fluence and topographically customized collagen corneal crosslinking

    Directory of Open Access Journals (Sweden)

    Kanellopoulos AJ

    2014-12-01

    invasive alternative.Keywords: topography customizable crosslinking, high-fluence cross linking, epi-on and epi-off CXL, PiXL, KXL II, CXL hyperopic correction, CXL presbyopic correction

  17. Keratoconus, cross-link-induction, comparison between fitting exponential function and a fitting equation obtained by a mathematical model.

    Science.gov (United States)

    Albanese, A; Urso, R; Bianciardi, L; Rigato, M; Battisti, E

    2009-11-01

    With reference to experimental data in the literature, we present a model consisting of two elastic elements, conceived to simulate resistance to stretching, at constant velocity of elongation, of corneal tissue affected by keratoconus, treated with riboflavin and ultraviolet irradiation to induce cross-linking. The function describing model behaviour adapted to stress and strain values. It was found that the Young's moduli of the two elastic elements increased in cross-linked tissues and that cross-linking treatment therefore increased corneal rigidity. It is recognized that this observation is substantially in line with the conclusion reported in the literature, obtained using an exponential fitting function. It is observed, however, that the latter function implies a condition of non-zero stresses without strain, and does not provide interpretative insights for lack of any biomechanical basis. Above all, the function fits a singular trend, inexplicably claimed to be viscoelastic, with surprising perfection. In any case, using the reported data, the study demonstrates that a fitting equation obtained by a modelling approach not only shows the evident efficacy of the treatment, but also provides orientations for studying modifications induced in cross-linked fibres.

  18. Cross Linked Metal Particles for Low Noise Bolometer Materials

    Science.gov (United States)

    2016-12-12

    SECURITY CLASSIFICATION OF: This final report summarizes WSU’s progress from 4/2/2015 to 09/30/2016 on the project, "Cross-linked Metal Particles ...2016 Final Report: Cross-linked Metal Particles for Low-noise Bolometer Materials The views, opinions and/or findings contained in this report are...peer-reviewed journals: Number of Papers published in non peer-reviewed journals: Final Report: Cross-linked Metal Particles for Low-noise Bolometer

  19. Histological evaluation of type I collagen scaffolds preparde under different dehydrothermal cross-linking conditions in a rat model%应用不同物理加强条件的Ⅰ型胶原支架的大白鼠动物模型与组织学分析

    Institute of Scientific and Technical Information of China (English)

    张聪; 张艳勤; Mark Spilker; Myron Spector; 李登云; 鲁玉梅; 许和平

    2016-01-01

    BACKGROUND:In previous studies, the dehydrothermal cross-linking method was modified by the authors to improve the degradation property of colagen scaffolds. The cross-linking time was increased from 24 to 48 hours, and the cross-linking temperature increased from 105 to 115℃. OBJECTIVE:To verify the anti-degradation ability of colagen scaffolds prepared using the modified dehydrothermal cross-linking method and to obtain the optimal efficacy of the scaffolds on damaged tissue repair and regeneration. METHODS: Highly-purified type I colagen scaffolds with native triple helix structure were prepared and subjected to three different dehydrothermal cross-linking conditions: 105℃ for 24 hours, 105℃ for 48 hours and 115℃ for 24 hours. Material samples, 1 cm×1 cm, were implanted subcutaneously into the rat dorsum. The specimens were harvested at 3 days, 14 days and 42 postoperative days folowed by fixation and histological analysis using hematoxylin-eosin staining. RESULTS AND CONCLUSION:No untoward foreign body and immunological reactions were observed in any groups. In the group of 105℃ for 48 hours, the scaffold retention and degree of pore openness were better than the other two groups at 14 days after scaffold implantation (P < 0.05). These findings indirectly suggest that the anti-degradation ability of colagen scaffolds can be strengthened under certain dehydrothermal cross-linking conditions: the cross-linking time is increased from 24 to 48 hours.%背景:为改善胶原支架的降解性能,作者对胶原支架的高温脱水物理交联方法进行了改进,将交联时间由24 h增加到48 h,将交联温度由105℃提高到115℃。目的:验证改进高温脱水物理交联方法制备胶原支架的抗降解能力,获取支架在体内对受损组织修复与再生的最佳功效。方法:将高纯度保持三螺旋结构的动物源性Ⅰ型胶原制成膜状支架,分别采取3种不同条件的高

  20. Radiation cross-linked polyolefin-insulated wire

    Science.gov (United States)

    Sano, K.; Ishitani, H.

    Because radiation cross-linked polyolefin has excellent mechanical heat resistance, its application limit can be expanded extremely by improving the resistance against heat oxidation and flame. This paper is concerning a halogen free radiation cross-linked polyolefin-insulated wire having excellent heat resistance and flameretardant property, which is used for appliances.

  1. 老年髋部骨折围术期Ⅰ型胶原交联N末端肽和骨钙素的检测及意义%Detection and Significance of Cross-Linked N-Telopeptide of TypeⅠCollagen and Osteocalcin during Perioperative Period in Elderly Patients with Hip Fracture

    Institute of Scientific and Technical Information of China (English)

    李经堂; 汤晓正; 熊龙; 刘剑军

    2015-01-01

    目的:通过对老年髋部骨折围术期骨代谢生化指标[Ⅰ型胶原交联 N末端肽(NTX)和骨钙素(又称骨γ-羧基谷氨酸蛋,BGP)]变化的研究,为临床老年髋部骨折围术期的抗骨质疏松治疗提供一定的帮助。方法对56例老年髋部骨折患者采用双能 X线骨密度仪行骨密度(BMD)测定,并根据BMD测定结果将56例患者分为2组:骨质疏松组(30例)和非骨质疏松组(26例)。测定56例患者,术前、术后2周血清 NTX、BGP水平。结果56例患者中术后2周30例患者(其中男9例,女21例)BMD值较成年人BMD峰值减低2.5个标准差以上,26例患者(其中男15例,女11例)BMD值较成年人BMD减低不足2.5个标准差,女性骨质疏松症发病率明显高于男性(P<0.05)。与术前比较,56例患者术后2周血清 NTX水平均明显升高,女性、骨质疏松组术后2周血清 BGP水平则均明显降低(均P<0.05);与男性比较,女性术后2周血清NTX差值明显升高,血清BGP差值则明显降低(均P<0.05);与非骨质疏松组比较,骨质疏松组术后2周血清 NTX差值明显升高,血清 BGP 差值则明显降低(均P<0.05)。结论老年髋部骨折患者围术期骨代谢加快,骨丢失大于骨形成,女性患者和骨质疏松患者骨丢失更明显,围术期应加强抗骨质疏松治疗。%Objective To provide help for the treatment of osteoporosis during the periopera-tive period in elderly patients with hip fracture through investigating the changes in bone metabo-lism markers cross-linked N-telopeptide of typeⅠcollagen(NTX)and osteocalcinduring(BGP). Methods The bone mineral density(BMD)was measured by dual energy X-ray absorptiometry in 5 6 elderly patients with hip fracture.According to the BMD values,these patients were divided in-to two groups:osteoporosis group(n=30)and non-osteoporosis group(n=26).Serum levels of NTX and BGP were determined

  2. Role of the Maillard reaction in aging of tissue proteins. Advanced glycation end product-dependent increase in imidazolium cross-links in human lens proteins.

    Science.gov (United States)

    Frye, E B; Degenhardt, T P; Thorpe, S R; Baynes, J W

    1998-07-24

    Dicarbonyl compounds such as glyoxal and methylglyoxal are reactive dicarbonyl intermediates in the nonenzymatic browning and cross-linking of proteins during the Maillard reaction. We describe here the quantification of glyoxal and methylglyoxal-derived imidazolium cross-links in tissue proteins. The imidazolium salt cross-links, glyoxal-lysine dimer (GOLD) and methylglyoxal-lysine dimer (MOLD), were measured by liquid chromatography/mass spectrometry and were present in lens protein at concentrations of 0. 02-0.2 and 0.1-0.8 mmol/mol of lysine, respectively. The lens concentrations of GOLD and MOLD correlated significantly with one another and also increased with lens age. GOLD and MOLD were present at significantly higher concentrations than the fluorescent cross-links pentosidine and dityrosine, identifying them as major Maillard reaction cross-links in lens proteins. Like the N-carboxy-alkyllysines Nepsilon-(carboxymethyl)lysine and Nepsilon-(carboxyethyl)lysine, these cross-links were also detected at lower concentrations in human skin collagen and increased with age in collagen. The presence of GOLD and MOLD in tissue proteins implicates methylglyoxal and glyoxal, either free or protein-bound, as important precursors of protein cross-links formed during Maillard reactions in vivo during aging and in disease.

  3. Scleral wound healing with cross-link technique using riboflavin and ultraviolet A on rabbit eyes.

    Science.gov (United States)

    Damasceno, Nadyr A; Miguel, Nadia C; Ventura, Marcelo Palis; Burnier, Miguel; Avila, Marcos P; Damasceno, Eduardo F

    2017-01-01

    The aim of study was to evaluate the cross-link using riboflavin and ultraviolet A (UVA) for improving scleral wound healing. This was an experimental study involving four New Zealand rabbits (eight eyes). Therapy procedure was chosen for the right eye and control procedure for the left one. UVA irradiation of 365 nm with a surface irradiance of 3 mW/cm(2) and a photosensitizer of riboflavin drops were applied for 30 minutes on the right eye at 2 mm from the limbus. Sclerotomy incision was performed at 2 mm from the limbus in both right (on the cross-link-treated area) and left eye. Then, 30 days after surgery, a morphological analysis and histological staining with hematoxylin-eosin and picrosirius red were performed, and the sclerotomy cicatrization of right and left eyes was compared. The variables investigated were as follows: sclerotomy incision pictures and measurements were made using the ImageJ Software. Scleral thickness was measured (employing the anterior optical coherence tomography and the digital caliper). Collagen fiber density stained with picrosirius red staining was measured using the Image Pro Plus software. The morphological analysis showed that in all samples, the right eye presented sclerotomy closure, and in two eyes, among them, there were no visible edges of the sclerotomies incision. The left eye presented sclerotomy closure and incision edges. The Image Pro demonstrated a higher density of collagen fibers in the right eye when compared to the one. The statistical analysis was significant when compared to the collagen fiber density in the treated eyes with the control eyes. The cross-link procedure resulted in a better sclerotomy wound healing.

  4. Elasticity of cross-linked semiflexible biopolymers under tension.

    Science.gov (United States)

    von der Heydt, Alice; Wilkin, Daniel; Benetatos, Panayotis; Zippelius, Annette

    2013-09-01

    Aiming at the mechanical properties of cross-linked biopolymers, we set up and analyze a model of two weakly bending wormlike chains subjected to a tensile force, with regularly spaced inter-chain bonds (cross-links) represented by harmonic springs. Within this model, we compute the force-extension curve and the differential stiffness exactly and discuss several limiting cases. Cross-links effectively stiffen the chain pair by reducing thermal fluctuations transverse to the force and alignment direction. The extra alignment due to cross-links increases both with growing number and with growing strength of the cross-links, and is most prominent for small force f. For large f, the additional, cross-link-induced extension is subdominant except for the case of linking the chains rigidly and continuously along their contour. In this combined limit, we recover asymptotically the elasticity of a weakly bending wormlike chain without constraints, stiffened by a factor of 4. The increase in differential stiffness can be as large as 100% for small f or large numbers of cross-links.

  5. Molecular Structures of Isolevuglandin-Protein Cross-Links.

    Science.gov (United States)

    Bi, Wenzhao; Jang, Geeng-Fu; Zhang, Lei; Crabb, John W; Laird, James; Linetsky, Mikhail; Salomon, Robert G

    2016-10-17

    Isolevuglandins (isoLGs) are stereo and structurally isomeric γ-ketoaldehydes produced through free radical-induced oxidation of arachidonates. Some isoLG isomers are also generated through enzymatic cyclooxygenation. Post-translational modification of proteins by isoLGs is associated with loss-of-function, cross-linking and aggregation. We now report that a low level of modification by one or two molecules of isoLG has a profound effect on the activity of a multi subunit protease, calpain-1. Modification of one or two key lysyl residues apparently suffices to abolish catalytic activity. Covalent modification of calpain-1 led to intersubunit cross-linking. Hetero- and homo-oligomers of the catalytic and regulatory subunits of calpain-1 were detected by SDS-PAGE with Western blotting. N-Acetyl-glycyl-lysine methyl ester and β-amyloid(11-17) peptide EVHHQKL were used as models for characterizing the cross-linking of protein lysyl residues resulting from adduction of iso[4]LGE2. Aminal, bispyrrole, and trispyrrole cross-links of these two peptides were identified and fully characterized by mass spectrometry. Aminal and bispyrrole dimers were both detected. Furthermore, a complex mixture of derivatives of the bispyrrole cross-link containing one or more additional atoms of oxygen was found. Interesting differences are evident in the predominant cross-link type generated in the reaction of iso[4]LGE2 with these peptides. More aminal cross-links versus bispyrrole are formed during the reaction of the dipeptide with iso[4]LGE2. In contrast, more bispyrrole versus aminal cross-links are formed during the reaction of EVHHQKL with iso[4]LGE2. It is tempting to speculate that the EVHHQKL peptide-pyrrole modification forms noncovalent aggregates that favor the production of covalent bispyrrole cross-links because β-amyloid(11-17) tends to spontaneously oligomerize.

  6. Glutaraldehyde cross-linking of tendon mechanical effects at the level of the tendon fascicle and fibril

    DEFF Research Database (Denmark)

    Hansen, Philip; Hassenkam, Tue; Svensson, Rene Bruggebusch

    2009-01-01

    Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy...... allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from approximately 8 MPa to approximately 39 MPa. The mechanical effects of glutaraldehyde...... at the tendon fibril level were examined by atomic force microscopy. Peak forces increased from approximately 1379 to approximately 2622 pN while an extended Hertz fit of force-indentation data showed a approximately 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross...

  7. Corneal Laceration

    Medline Plus

    Full Text Available ... Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment What Is Corneal Laceration? Written By: Daniel Porter Reviewed By: ... A Harrison MD Sep. 01, 2016 The cornea is the clear front window of the eye . A ...

  8. Characterization of genipin-modified dentin collagen.

    Science.gov (United States)

    Nagaoka, Hiroko; Nagaoka, Hideaki; Walter, Ricardo; Boushell, Lee W; Miguez, Patricia A; Burton, Andrew; Ritter, André V; Yamauchi, Mitsuo

    2014-01-01

    Application of biomodification techniques to dentin can improve its biochemical and biomechanical properties. Several collagen cross-linking agents have been reported to strengthen the mechanical properties of dentin. However, the characteristics of collagen that has undergone agent-induced biomodification are not well understood. The objective of this study was to analyze the effects of a natural cross-linking agent, genipin (GE), on dentin discoloration, collagen stability, and changes in amino acid composition and lysyl oxidase mediated natural collagen cross-links. Dentin collagen obtained from extracted bovine teeth was treated with three different concentrations of GE (0.01%, 0.1%, and 0.5%) for several treatment times (0-24 h). Changes in biochemical properties of NaB(3)H4-reduced collagen were characterized by amino acid and cross-link analyses. The treatment of dentin collagen with GE resulted in a concentration- and time-dependent pigmentation and stability against bacterial collagenase. The lysyl oxidase-mediated trivalent mature cross-link, pyridinoline, showed no difference among all groups while the major divalent immature cross-link, dehydro-dihydroxylysinonorleucine/its ketoamine in collagen treated with 0.5% GE for 24 h, significantly decreased compared to control (P < 0.05). The newly formed GE-induced cross-links most likely involve lysine and hydroxylysine residues of collagen in a concentration-dependent manner. Some of these cross-links appear to be reducible and stabilized with NaB(3)H4.

  9. Characterization of Genipin-Modified Dentin Collagen

    Directory of Open Access Journals (Sweden)

    Hiroko Nagaoka

    2014-01-01

    Full Text Available Application of biomodification techniques to dentin can improve its biochemical and biomechanical properties. Several collagen cross-linking agents have been reported to strengthen the mechanical properties of dentin. However, the characteristics of collagen that has undergone agent-induced biomodification are not well understood. The objective of this study was to analyze the effects of a natural cross-linking agent, genipin (GE, on dentin discoloration, collagen stability, and changes in amino acid composition and lysyl oxidase mediated natural collagen cross-links. Dentin collagen obtained from extracted bovine teeth was treated with three different concentrations of GE (0.01%, 0.1%, and 0.5% for several treatment times (0–24 h. Changes in biochemical properties of NaB3H4-reduced collagen were characterized by amino acid and cross-link analyses. The treatment of dentin collagen with GE resulted in a concentration- and time-dependent pigmentation and stability against bacterial collagenase. The lysyl oxidase-mediated trivalent mature cross-link, pyridinoline, showed no difference among all groups while the major divalent immature cross-link, dehydro-dihydroxylysinonorleucine/its ketoamine in collagen treated with 0.5% GE for 24 h, significantly decreased compared to control (P< 0.05. The newly formed GE-induced cross-links most likely involve lysine and hydroxylysine residues of collagen in a concentration-dependent manner. Some of these cross-links appear to be reducible and stabilized with NaB3H4.

  10. Covalently cross-linked polyetheretherketone proton exchange membrane for DMFC

    CSIR Research Space (South Africa)

    Luo, H

    2009-05-01

    Full Text Available -7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application....

  11. Gelation threshold of cross-linked polymer brushes.

    Science.gov (United States)

    Hoffmann, Max; Lang, Michael; Sommer, Jens-Uwe

    2011-02-01

    The cross-linking of polymer brushes is studied using the bond-fluctuation model. By mapping the cross-linking process into a two-dimensional (2D) percolation problem within the lattice of grafting points, we investigate the gelation transition in detail. We show that the particular properties of cross-linked polymer brushes can be reduced to the distribution of bonds which are formed between the grafted chains, and we propose scaling arguments to relate the gelation threshold to the chain length and the grafting density. The gelation threshold is lower than the percolation threshold for 2D bond percolation because of the longer range and broad distribution of bonds formed by the cross-linking process. We term this type of percolation problem star percolation. We observe a broad crossover from mean-field to critical percolation behavior by analyzing the cluster size distribution near the gelation threshold.

  12. Photochemical Patterning of Ionically Cross-Linked Hydrogels

    Directory of Open Access Journals (Sweden)

    Marion Bruchet

    2013-08-01

    Full Text Available Iron(III cross-linked alginate hydrogel incorporating sodium lactate undergoes photoinduced degradation, thus serving as a biocompatible positive photoresist suitable for photochemical patterning. Alternatively, surface etching of iron(III cross-linked hydrogel contacting lactic acid solution can be used for controlling the thickness of the photochemical pattering. Due to biocompatibility, both of these approaches appear potentially useful for advanced manipulation with cell cultures including growing cells on the surface or entrapping them within the hydrogel.

  13. Elasticity of cross-linked semiflexible biopolymers under tension

    CERN Document Server

    von der Heydt, Alice; Benetatos, Panayotis; Zippelius, Annette

    2013-01-01

    Aiming at the mechanical properties of cross-linked biopolymers, we set up and analyze a model of two weakly bending wormlike chains subjected to a tensile force, with regularly spaced inter-chain bonds (cross-links) represented by harmonic springs. Within this model, we compute the force-extension curve and the differential stiffness exactly and discuss several limiting cases. Cross-links effectively stiffen the chain pair by reducing thermal fluctuations transverse to the force and alignment direction. The extra alignment due to cross-links increases both with growing number and with growing strength of the cross-links, and is most prominent for small force f. For large f, the additional, cross-link-induced extension is subdominant except for the case of linking the chains rigidly and continuously along their contour. In this combined limit, we recover asymptotically the elasticity of a weakly bending wormlike chain without constraints, stiffened by a factor four. The increase in differential stiffness can ...

  14. Scleral wound healing with cross-link technique using riboflavin and ultraviolet A on rabbit eyes

    Directory of Open Access Journals (Sweden)

    Damasceno NA

    2017-07-01

    Full Text Available Nadyr A Damasceno,1 Nadia C Miguel,2 Marcelo Palis Ventura,3 Miguel Burnier Jr,4 Marcos P Avila,5 Eduardo F Damasceno3 1Ophthalmology Department, Hospital Naval Marcílio Dias, 2Laboratory of Neurohistology and Cell Ultrastructure, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 3Ophthalmology Department, Universidade Federal Fluminense, Niterói, Brazil; 4Ophthalmology Department, McGill University, Montreal, QC, Canada; 5Ophthalmology Department, Universidade Federal de Goiás, Goiania, Brazil Purpose: The aim of study was to evaluate the cross-link using riboflavin and ultraviolet A (UVA for improving scleral wound healing.Materials and methods: This was an experimental study involving four New Zealand rabbits (eight eyes. Therapy procedure was chosen for the right eye and control procedure for the left one. UVA irradiation of 365 nm with a surface irradiance of 3 mW/cm2 and a photosensitizer of riboflavin drops were applied for 30 minutes on the right eye at 2 mm from the limbus. Sclerotomy incision was performed at 2 mm from the limbus in both right (on the cross-link-treated area and left eye. Then, 30 days after surgery, a morphological analysis and histological staining with hematoxylin–eosin and picrosirius red were performed, and the sclerotomy cicatrization of right and left eyes was compared. The variables investigated were as follows: sclerotomy incision pictures and measurements were made using the ImageJ Software. Scleral thickness was measured (employing the anterior optical coherence tomography and the digital caliper. Collagen fiber density stained with picrosirius red staining was measured using the Image Pro Plus software.Results: The morphological analysis showed that in all samples, the right eye presented sclerotomy closure, and in two eyes, among them, there were no visible edges of the sclerotomies incision. The left eye presented sclerotomy closure and incision edges

  15. Biocompatibility of Genipin cross-linked type I collagen with human adipose-derived stem cells in vitro%京尼平交联Ⅰ型胶原蛋白材料与人脂肪间充质干细胞的生物相容性

    Institute of Scientific and Technical Information of China (English)

    王刚; 亢婷; 刘毅; 刘刚强

    2014-01-01

    BACKGROUND:Low toxicity of Genipin has certain species and cellspecificity. Biocompatibility of Genipin cross-linked type I colagen with human adipose-derived stem cels is essential for construction of tissue-engineered adipose. OBJECTIVE:To investigate the bbiocompatibility of Genipin cross-linked type I colagen with human adipose-derived stem cels. METHODS:Human adipose-derived stem cels were isolated and cultured to the third generation, and the cels were seeded on Genipin cross-linked type I colagen scaffold. MTT assay was used to evaluate the adhesion and proliferation of cels on the scaffold, and the toxic effects of Genipin cross-linked type I colagen on human adipose-derived stem cels. Optical microscopy and scanning electron microscopy were utilized to observe the adhesion and growth process of human adipose-derived stem cels on the scaffold as wel as the morphological changes of cels. RESULTS AND CONCLUSION:Human adipose-derived stem cels could adhere to the scaffold immediately after seeded and increase gradualy on the scaffold, with the average adhesion rate of 86.5%. Optical microscopy and scanning electron microscopy showed that human adipose-derived stem cels adhered wel on the scaffold. The cels increased gradualy over time, and could migrate into the scaffold, and distribute evenly with the passage of time when observed with optical microscopy. The result showed Genipin possesses very low cytotoxicity to the cels, and the outstanding biocompatibility is found between the cels and scaffoldin vitro after cross-linked with Genipin.%背景:京尼平的低毒性具有一定的种属和细胞特异性,人脂肪间充质干细胞与京尼平交联的Ⅰ型胶原蛋白支架材料的生物相容性对于应用两者构建组织工程脂肪至关重要。  目的:评估人脂肪间充质干细胞与京尼平交联的Ⅰ型胶原蛋白支架材料的生物相容性。  方法:分离培养人脂肪间充质干细胞,传代培养至第3代

  16. A collagen defect in homocystinuria.

    Science.gov (United States)

    Kang, A H; Trelstad, R L

    1973-10-01

    The biochemical mechanism accounting for the connective tissue abnormalities in homocystinuria was explored by examining the effects of various amino acids known to accumulate in the plasma of patients with this disease on cross-link formation in collagen. Neutral salt solutions of purified, rat skin collagen, rich in cross-link precursor aldehydes, were polymerized to native type fibrils by incubating at 37 degrees C in the presence of homocysteine, homocystine, or methionine. After the polymerization was completed, each sample was examined for the formation of covalent intermolecular cross-links, assessed indirectly by solubility tests and directly by measuring the cross-link compounds after reduction with tritiated sodium borohydride and hydrolysis. Collagen solutions containing homocysteine (0.01 M-0.1 M) failed to form insoluble fibrils. Furthermore, much less of the reducible cross-links, Delta(6,7) dehydrohydroxylysinonorleucine, Delta(6,7) dehydrohydroxylysinohydroxynorleucine, and histidino-dehydrohydroxymerodesmosine were formed in the preparations containing homocysteine as compared with the control and the samples containing methionine or homocystine. The content of the precursor aldehydes, alpha-aminoadipic-delta-semialdehyde (allysine) and the aldol condensation product, was also markedly diminished in tropocollagen incubated with homocysteine. It is concluded that homocysteine interferes with the formation of intermolecular cross-links that help stabilize the collagen macromolecular network via its reversible binding to the aldehydic functional groups. Analysis of the collagen cross-links in skin biopsy samples obtained from three patients with documented homocystinuria showed that the cross-links were significantly decreased as compared with the age-matched controls, supporting the tentative conclusions reached from the in vitro model studies. In addition, the solubility of dermal collagen in non-denaturing solvents was significantly increased in

  17. Extreme dryness and DNA-protein cross-links

    Science.gov (United States)

    Bieger-Dose, A.; Dose, K.; Meffert, R.; Mehler, M.; Risi, S.

    Exposure of fungal conidia (Aspergillus ochraceus) or spores of Bacillus subtilis to extreme dryness or vacuum induces DNA lesions, including strand breaks and the formation of DNA-protein cross-links. In wet cells only a small amount of protein is bound to DNA, but exposure to conditions of lowered water activity results in an increasing number of cross-links between DNA and proteins. In fungal conidia these cross-links are detected after selective iodination (125J) of the DNA-bound proteins followed by gel electrophoresis and subsequent autoradiography. Another approach is the labelling of DNA with 32p by means of nick translation and the detection of differences in the electrophoretic mobility of DNA before and after digestion with proteinase K of proteins bound to DNA.

  18. Computer simulation of randomly cross-linked polymer networks

    CERN Document Server

    Williams, T P

    2002-01-01

    In this work, Monte Carlo and Stochastic Dynamics computer simulations of mesoscale model randomly cross-linked networks were undertaken. Task parallel implementations of the lattice Monte Carlo Bond Fluctuation model and Kremer-Grest Stochastic Dynamics bead-spring continuum model were designed and used for this purpose. Lattice and continuum precursor melt systems were prepared and then cross-linked to varying degrees. The resultant networks were used to study structural changes during deformation and relaxation dynamics. The effects of a random network topology featuring a polydisperse distribution of strand lengths and an abundance of pendant chain ends, were qualitatively compared to recent published work. A preliminary investigation into the effects of temperature on the structural and dynamical properties was also undertaken. Structural changes during isotropic swelling and uniaxial deformation, revealed a pronounced non-affine deformation dependant on the degree of cross-linking. Fractal heterogeneiti...

  19. Effect of corneal epithelium on ultraviolet-A and riboflavin absorption

    Directory of Open Access Journals (Sweden)

    Katia Mantovani Bottós

    2011-10-01

    Full Text Available PURPOSE: To determine if the corneal epithelium prevents the collagen cross-linking effect. Using immunofluorescence microscopy after CXL, we indirectly analyzed the role of the epithelium as ultraviolet-A (UVA shield as well as a barrier to riboflavin penetration. METHODS: Fifteen freshly enucleated porcine eyes were divided into 3 groups. The corneal epithelium was kept intact in all groups. Five eyes served as control (Group 1. On group 2, eyes received tetracaine anesthetic drops and topical 0.1% riboflavin solution (10 mg riboflavin-5-phosphate in 10 mL 20% dextran-T-500. On Group 3, riboflavin was injected into the anterior chamber to allow penetration of the drug through the endothelium. Groups 2 and 3 were exposed to UVA (365 nm, 3 mW/cm² for 30 minutes. Ultra-thin sections (8 µm of the corneas were stained with anti-collagen type I and DAPI (4,6-diamidino-2-fenilindole dihydrocloride and analyzed with fluorescence microscopy. RESULTS: Corneas treated with UVA irradiation and intracameral injection of riboflavin (Group 3 showed greater pattern of collagen organization compared to groups 1 (Control and 2 (riboflavin and tetracaine eye drops. A yellow stromal staining, which represents the riboflavin diffusion into the stroma, was only observed in eyes injected with riboflavin into the anterior chamber. CONCLUSION: Using immunofluorescence microscopy in porcine corneas, we demonstrated that the corneal epithelium reduces the effectiveness of CXL by preventing the penetration of the drug and not by limiting the UVA transmittance. An inadequate intrastromal concentration of riboflavin may impair CXL effect.

  20. Safety and Efficacy of Sequential Intracorneal Ring Segment Implantation and Cross-linking in Pediatric Keratoconus.

    Science.gov (United States)

    Abdelmassih, Youssef; El-Khoury, Sylvain; Dirani, Ali; Antonios, Rafic; Fadlallah, Ali; Cherfan, Carole G; Chelala, Elias; Jarade, Elias F

    2017-06-01

    To evaluate the safety and visual outcome of intracorneal ring segment (ICRS) implantation followed by cross-linking in pediatric keratoconus patients. Retrospective interventional case series. This retrospective study included pediatric patients (aged ≤14 years) with keratoconus and poor corrected distance visual acuity (CDVA) that underwent ICRS implantation and cross-linking (CXL). ICRS were inserted under topical anesthesia after creating a corneal tunnel with a femtosecond laser. Cross-linking was performed 1 month subsequently. Records were reviewed and data collected preoperatively and at 6 months, 1 year, 2 years, and 4 years postoperatively. Twelve patients (17 eyes; 10 male, 2 female) aged 9-14 years (mean age 12.3 years) received ICRS implantation followed by CXL. Follow-up times ranged from 6 months to 4 years after surgery. At the 6-month follow-up all eyes were evaluated; at the 1-year, 2-year, and 4-year follow-up 11, 10, and 7 eyes were evaluated, respectively. At the 6-month follow-up, mean CDVA in comparison to preoperative levels improved significantly (P = .001) from 0.30 ± 0.19 logMAR to 0.12 ± 0.1 logMAR; mean uncorrected distance visual acuity (UDVA) also improved significantly from 0.90 ± 0.50 logMAR to 0.43 ± 0.31 logMAR. A significant decrease in both keratometry readings and spherical equivalent (from -4.0 to -1.56 diopters) was also noted after ICRS insertion. At the 1-year, 2-year, and 4-year follow-up refractive values remained relatively stable in comparison to the 6-month follow-up, except for a minor but significant improvement in cylinder and, at 4 years, in UDVA. All patients tolerated the surgery well and no intraoperative or postoperative complications were reported, except for 1 ring segment that had to be removed after 2 years owing to vascularization and corneal thinning. ICRS implantation is a safe and effective procedure for visual rehabilitation in children with keratoconus and poor CDVA. Copyright © 2017

  1. FTIR Spectroscopic Studies on Cross Linking of SU-8 Photoresist

    Science.gov (United States)

    Kalaiselvi, S. M. P.; Tan, T. L.; Rawat, R. S.; Lee, P.; Heussler, S. P.; Breese, M. B. H.

    2013-11-01

    The usage of chemically-amplified, negative tone SU-8 photoresist is numerous, spanning industrial, scientific and medical fields. Hence, in this study, some preliminary studies were conducted to understand the dosage and heat treatment requirements of the SU-8 photoresist essential for pattern generation using X-ray lithography. In this work, using Synchrotron as the X-ray source, SU-8 photoresist was characterized for X-ray lithography in terms of its process parameters such as X-ray exposure dose, post exposure bake (PEB) time and temperature for various photoresist thicknesses which is considered worthwhile in view of applications of SU-8 for the fabrication of very high aspect ratio micro structures. The process parameters were varied and the resultant cross linking of the molecular chains of the photoresist was accurately monitored using a Fourier Transform Infra-Red (FTIR) spectrometer and the results are discussed. The infrared absorption peak at 914 cm-1 in the spectrum of the SU-8 photoresist was found to be a useful indicator for the completion of cross linking in the SU-8 photoresist. Results show that the cross linking of the SU-8 photoresist is at a higher rate from 0 J/cm3 to 30 J/cm3 after which the peak almost saturates regardless of the PEB time. It is a good evidence for the validation of dosage requirement of SU-8 photoresist for effective completion of cross linking, which in turn is a requirement for efficient fabrication of micro and nano structures. An analogous behavior was also observed between the extent of cross linking and the PEB time and temperature. The rate of cross linking declines after a certain period of PEB time regardless of PEB temperature. The obtained results also show a definite relation between variation of the absorbance area of the peak at 914 cm-1 and the X-ray exposure dose.

  2. Resin bond strength to water versus ethanol-saturated human dentin pretreated with three different cross-linking agents

    Science.gov (United States)

    Venigalla, Bhuvan Shome; Jyothi, Pinnamreddy; Kamishetty, Shekhar; Reddy, Smitha; Cherukupalli, Ravi Chandra; Reddy, Depa Arun

    2016-01-01

    Context: Resin-dentin bonds are unstable owing to hydrolytic and enzymatic degradation. Several approaches such as collagen cross-linking and ethanol-wet bonding (EWB) have been developed to overcome this problem. Collagen cross-linking improves the intrinsic properties of the collagen matrix. However, it leaves a water-rich collagen matrix with incomplete resin infiltration making it susceptible to fatigue degradation. Since EWB is expected to overcome the drawbacks of water-wet bonding (WWB), a combination of collagen cross-linking with EWB was tested. Aim: The aim of this study was to compare the effect of pretreatment with different cross-linking agents such as ultraviolet A (UVA)-activated 0.1% riboflavin, 1 M carbodiimide, and 6.5 wt% proanthocyanidin on the immediate and long-term bond strengths of an etch and rinse adhesive system to water- versus ethanol-saturated dentin within clinically relevant application time periods. Settings and Design: Long-term in vitro study evaluating the microtensile bond strength of adhesive-dentin interface after different surface pretreatments. Subjects and Methods: Eighty freshly extracted human molars were prepared to expose dentin, etched with 37% phosphoric acid for 15 s rinsed, and grouped randomly. They were blot-dried and pretreated with different cross-linkers: 0.1% riboflavin for 2 min followed by UVA activation for 2 min; 1 M carbodiimide for 2 min; 6.5 wt% proanthocyanidin for 2 min and rinsed. They were then bonded with Adper Single Bond Adhesive (3M ESPE), by either WWB or EWB, followed by resin composite build-ups (Filtek Z350, 3M ESPE). Bonded specimens in each group were then sectioned and divided into two halves. Microtensile bond strength was tested in one half after 24 h and the other after 6 months storage in artificial saliva. Statistical Analysis Used: Analysis was done using SPSS version 18 software (SPSS Inc., Chicago, IL, USA). Intergroup comparison of bond strength was done using ANOVA with post hoc

  3. Inactivation of Matrix-bound MMPs by Cross-linking Agents in Acid Etched Dentin

    Science.gov (United States)

    Scheffel, Débora Lopes Salles; Hebling, Josimeri; Scheffel, Régis Henke; Agee, Kelly A.; Turco, Gianluca; de Souza Costa, Carlos Alberto; Pashley, David H.

    2014-01-01

    Objectives Published TEM analysis of in vivo resin-dentin bonds shows that in 44 months almost 70% of collagen fibrils from the hybrid layer disappear. Matrix metalloproteinases (MMPs) play an important role in that process and are thought to be the main factor responsible for the solubitization of dentin collagen. Therefore, this study aimed to evaluate the inactivation of matrix-bound MMPs by carbodiimide (EDC) or proanthocyanidin (PA) both cross-linking agents, or the MMP-inhibitor, chlorhexidine (CHX), on acid-etched dentin using a simplified MMP assay method. Methods Dentin beams (1×1×6mm) were obtained from mid-coronal dentin of sound third molars and randomly divided into 6 groups (G) according to the dentin treatment: G1: Deionized water (control), G2: 0.1M EDC, G3: 0.5M EDC, G4: 0.5M EDC+35% HEMA, G5: 5% Proanthocyanidin (PA) and G6: 2% CHX. The beams were etched for 15s with 37% phosphoric acid, rinsed and then immersed for 60s in one of the treatment solutions. The total MMP activity of dentin was analyzed for 1 h by colorimetric assay (Sensolyte). Data were submitted to Wilcoxon non-parametric test and Mann-Whitney tests (p>0.05). Results All experimental cross-linking solutions significantly reduced MMP activity compared to control, except 0.1M EDC (53.6% ±16.1). No difference was observed between cross-linking agents and 2% CHX 0.5M EDC + 35% HEMA (92.3% ±8.0) was similar to 0.5M EDC (89.1% ±6.4), 5% PA (100.8% ±10.9) and 2% CHX (83.4% ±10.9). Conclusion Dentin treatment with cross-linking agents is effective to significantly reduce MMP activity. Mixing 0.5M EDC and 35% HEMA did not influence EDC inhibitor potential. PMID:23786610

  4. Simulation of Fracture Nucleation in Cross-Linked Polymer Networks

    Science.gov (United States)

    Moller, J. C.; Barr, S. A.; Schultz, E. J.; Breitzman, T. D.; Berry, R. J.

    2013-02-01

    A novel atomistic simulation method is developed whereby polymer systems can undergo strain-rate-controlled deformation while bond scission is enabled. The aim is to provide insight into the nanoscale origins of fracture. Various highly cross-linked epoxy systems including various resin chain lengths and levels of nonreactive dilution were examined. Consistent with the results of physical experiments, cured resin strength increased and ductility decreased with increasing cross-link density. An analysis of dihedral angle activity shows the locations in the molecular network that are most absorptive of mechanical energy. Bond scission occurred principally at cross-link sites as well as between phenyl rings in the bisphenol moiety. Scissions typically occurred well after yield and were accompanied by steady increases in void size and dihedral angle motion between bisphenol moieties and at cross-link sites. The methods developed here could be more broadly applied to explore and compare the atomistic nature of deformation for various polymers such that mechanical and fracture properties could be tuned in a rational way. This method and its results could become part of a solution system that spans multiple length and time scales and that could more completely represent such mechanical events as fracture.

  5. The Database of Ribosomal Cross-links: an update.

    OpenAIRE

    Baranov, P V; Kubarenko, A V; Gurvich, O L; Shamolina, T A; Brimacombe, R

    1999-01-01

    The Database of Ribosomal Cross-links (DRC) was created in 1997. Here we describe new data incorporated into this database and several new features of the DRC. The DRC is freely available via World Wide Web at http://visitweb.com/database/ or http://www. mpimg-berlin-dahlem.mpg.de/ approximately ag_ribo/ag_brimacombe/drc/

  6. Elasticity of Rigidly Cross-Linked Networks of Athermal Filaments

    NARCIS (Netherlands)

    Zagar, Goran; Onck, Patrick R.; Van der Giessen, Erik

    2011-01-01

    Actin filaments assemble into network-like structures and play an important role in various cellular mechanical processes. It is known that the response of actin networks cross-linked by stiff proteins is characterized by two distinct regimes: (i) a linear stress strain response for small deformatio

  7. Molecular mechanisms in deformation of cross-linked hydrogel nanocomposite.

    Science.gov (United States)

    Mathesan, Santhosh; Rath, Amrita; Ghosh, Pijush

    2016-02-01

    The self-folding behavior in response to external stimuli observed in hydrogels is potentially used in biomedical applications. However, the use of hydrogels is limited because of its reduced mechanical properties. These properties are enhanced when the hydrogels are cross-linked and reinforced with nanoparticles. In this work, molecular dynamics (MD) simulation is applied to perform uniaxial tension and pull out tests to understand the mechanism contributing towards the enhanced mechanical properties. Also, nanomechanical characterization is performed using quasi static nanoindentation experiments to determine the Young's modulus of hydrogels in the presence of nanoparticles. The stress-strain responses for chitosan (CS), chitosan reinforced with hydroxyapatite (HAP) and cross-linked chitosan are obtained from uniaxial tension test. It is observed that the Young's modulus and maximum stress increase as the HAP content increases and also with cross-linking process. Load displacement plot from pullout test is compared for uncross-linked and cross-linked chitosan chains on hydroxyapatite surface. MD simulation reveals that the variation in the dihedral conformation of chitosan chains and the evolution of internal structural variables are associated with mechanical properties. Additional results reveal that the formation of hydrogen bonds and electrostatic interactions is responsible for the above variations in different systems.

  8. Porous Cross-Linked Polyimide-Urea Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  9. Lactoferrin binding to transglutaminase cross-linked casein micelles

    NARCIS (Netherlands)

    Anema, S.G.; de Kruif, C.G.

    2012-01-01

    Casein micelles in skim milk were either untreated (untreated milk) or were cross-linked using transglutaminase (TGA-milk). Added lactoferrin (LF) bound to the casein micelles and followed Langmuir adsorption isotherms. The adsorption level was the same in both milks and decreased the micellar zeta

  10. Polyimide Aerogels with Three-Dimensional Cross-Linked Structure

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor)

    2016-01-01

    A method for creating a three dimensional cross-linked polyimide structure includes dissolving a diamine, a dianhydride, and a triamine in a solvent, imidizing a polyamic acid gel by heating the gel, extracting the gel in a second solvent, supercritically drying the gel, and removing the solvent to create a polyimide aerogel.

  11. 21 CFR 177.2420 - Polyester resins, cross-linked.

    Science.gov (United States)

    2010-04-01

    .... Pentaerythritol. Polyoxypropylene ethers of 4,4′-isopropylide-nediphenol (containing an average of 2-7.5 moles of...-pentanediol. (3) Cross-linking agents: Butyl acrylate. Butyl methacrylate. Ethyl acrylate. Ethylhexyl acrylate... the production of the resins or added thereto to impart desired technical or physical...

  12. Cross-linked enzyme aggregates (CLEAs): stable and recyclable biocatalysts

    NARCIS (Netherlands)

    Sheldon, R.A.

    2007-01-01

    The key to obtaining an optimum performance of an enzyme is often a question of devising an effective method for its immobilization. In the present review, we describe a novel, versatile and effective methodology for enzyme immobilization as CLEAs (cross-linked enzyme aggregates). The method is

  13. Hyper-cross-linked, hybrid membranes via interfacial polymerization

    NARCIS (Netherlands)

    Raaijmakers, M.J.T.

    2015-01-01

    Hyper-cross-linked, hybrid membranes consist of covalent networks of alternating organic and inorganic, or biological groups. This thesis reports on the preparation of such hybrid networks via interfacial polymerization. The structure-property relationships of the hybrid networks depend strongly on

  14. Corneal Laceration

    Medline Plus

    Full Text Available ... lost sight from a corneal scar as a child. Now that I’m older, will a corneal transplant help me? May 15, 2015 Why Do My Eyes Burn After Inserting My Contacts? Feb 27, 2015 Dark ...

  15. CARS and SHG microscopy to follow the collagen production in living human corneal fibroblasts and mesenchymal stem cells in fibrin gel 3D cultures

    CERN Document Server

    Mortati, Leonardo; Sassi, Maria Paola

    2011-01-01

    Coherent anti-Stokes Raman scattering (CARS) microscopy is combined with second harmonic generation (SHG) technique in order to follow the early stage of stem cell differentiation within a 3D scaffold. CARS microscopy can detect lipid membranes and droplet compartments in living cells and SHG microscopy enables a strong imaging contrast for molecules with a non-centrosymmetric ordered structure like collagen. One of the first evidence of hMSCs differentiation is the formation of an extracellular matrix (ECM) where the collagen protein is its main component. This work demonstrated the multimodal CARS and SHG microscopy as a powerful non-invasive label free technique to investigate the collagen production dynamic in living cell 3D cultures. Its ability to image the cell morphology and the produced collagen distribution on a long term (4 weeks) experiment allowed to obtain important information about the cell-scaffold interaction and the ECM production. The very low limit reached in detecting collagen has permit...

  16. Corneal Abrasions

    Science.gov (United States)

    ... and lead to a serious condition called a corneal ulcer . That's why it's important to see a doctor to get a corneal abrasion checked out. What Causes a Corneal ... and land on your cornea, tears help to wash the particles away. Sometimes, ...

  17. Dynamic viscoelastic properties of collagen gels in the presence and absence of collagen fibrils

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Hideki; Shimizu, Kousuke; Hara, Masayuki, E-mail: hara@b.s.osakafu-u.ac.jp

    2012-10-01

    We measured the dynamic viscoelasticities of collagen gels prepared and modified by four different methods: i) collagen gels cross-linked by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) after their preparation, ii) collagen gels cross-linked simultaneously with their preparation, iii) collagen gels irradiated with gamma rays after their preparation, and iv) collagen gels directly formed from an acidic collagen solution by gamma-cross-linking. Dynamic viscoelasticities of all samples were measured using a rheometer before and after heating for 30 min at 80 Degree-Sign C. The collagen gels sequentially cross-linked by 125 mM EDC after preparation and then heated exhibited mechanically strong properties (storage modulus G Prime , 7010 Pa; loss modulus G Double-Prime , 288 Pa; Young's modulus E, 0.012 in the rapidly-increasing phase and 0.095 in the moderately-increasing phase; tensile strain, 5.29; tensile stress {sigma}, 0.053). We generally conclude that the G Prime value decreases when gels without fibrils are heated. On the other hand, well cross-linked collagen gels with thick fibrils, such as gels sequentially cross-linked with 125 mM EDC after preparation or gamma-cross-linked conventional gels irradiated at 40 kGy, exhibit a distinct increase in G Prime value after heating. Those gels also have thick, twisted, or fused fibrils of collagen. Highlights: Black-Right-Pointing-Pointer Dynamic viscoelasticities of collagen gels prepared and modified by various methods. Black-Right-Pointing-Pointer Chemical cross-linking with EDC and gamma-cross-linking were used. Black-Right-Pointing-Pointer Dynamic viscoelasticities of those samples were measured before and after the heating. Black-Right-Pointing-Pointer The gels sequentially cross-linked with 125 mM EDC exhibit a distinct increase in G' value after heating. Black-Right-Pointing-Pointer Those gels also have thick, twisted, or fused fibrils of collagen.

  18. Ratio between mature and immature enzymatic cross-links correlates with post-yield cortical bone behavior: An insight into greenstick fractures of the child fibula.

    Science.gov (United States)

    Berteau, Jean-Philippe; Gineyts, Evelyne; Pithioux, Martine; Baron, Cécile; Boivin, Georges; Lasaygues, Philippe; Chabrand, Patrick; Follet, Hélène

    2015-10-01

    As a determinant of skeletal fragility, the organic matrix is responsible for the post-yield and creep behavior of bone and for its toughness, while the mineral apatite acts on stiffness. Specific to the fibula and ulna in children, greenstick fractures show a plastic in vivo mechanical behavior before bone fracture. During growth, the immature form of collagen enzymatic cross-links gradually decreases, to be replaced by the mature form until adolescence, subsequently remaining constant throughout adult life. However, the link between the cortical bone organic matrix and greenstick fractures in children remains to be explored. Here, we sought to determine: 1) whether plastic bending fractures can occur in vitro, by testing cortical bone samples from children's fibula and 2) whether the post-yield behavior (ωp plastic energy) of cortical bone before fracture is related to total quantity of the collagen matrix, or to the quantity of mature and immature enzymatic cross-links and the quantity of non-enzymatic cross-links. We used a two-step approach; first, a 3-point microbending device tested 22 fibula machined bone samples from 7 children and 3 elderly adults until fracture. Second, biochemical analysis by HPLC was performed on the sample fragments. When pooling two groups of donors, children and elderly adults, results show a rank correlation between total energy dissipated before fracture and age and a linear correlation between plastic energy dissipated before fracture and ratio of immature/mature cross-links. A collagen matrix with more immature cross-links (i.e. a higher immature/mature cross-link ratio) is more likely to plastically deform before fracture. We conclude that this ratio in the sub-nanostructure of the organic matrix in cortical bone from the fibula may go some way towards explaining the variance in post-yield behavior. From a clinical point of view, therefore, our results provide a potential explanation of the presence of greenstick fractures in

  19. Cosmetic preservatives as therapeutic corneal and scleral tissue cross-linking agents

    National Research Council Canada - National Science Library

    Babar, Natasha; Kim, MiJung; Cao, Kerry; Shimizu, Yukari; Kim, Su-Young; Takaoka, Anna; Trokel, Stephen L; Paik, David C

    2015-01-01

    ...), that are in commercial use as preservatives in cosmetics and other personal care products. The present study was undertaken in order to screen such compounds for potential clinical utility as therapeutic TXL agents...

  20. Cytokines and growth factors cross-link heparan sulfate

    Science.gov (United States)

    Migliorini, Elisa; Thakar, Dhruv; Kühnle, Jens; Sadir, Rabia; Dyer, Douglas P.; Li, Yong; Sun, Changye; Volkman, Brian F.; Handel, Tracy M.; Coche-Guerente, Liliane; Fernig, David G.; Lortat-Jacob, Hugues; Richter, Ralf P.

    2015-01-01

    The glycosaminoglycan heparan sulfate (HS), present at the surface of most cells and ubiquitous in extracellular matrix, binds many soluble extracellular signalling molecules such as chemokines and growth factors, and regulates their transport and effector functions. It is, however, unknown whether upon binding HS these proteins can affect the long-range structure of HS. To test this idea, we interrogated a supramolecular model system, in which HS chains grafted to streptavidin-functionalized oligoethylene glycol monolayers or supported lipid bilayers mimic the HS-rich pericellular or extracellular matrix, with the biophysical techniques quartz crystal microbalance (QCM-D) and fluorescence recovery after photobleaching (FRAP). We were able to control and characterize the supramolecular presentation of HS chains—their local density, orientation, conformation and lateral mobility—and their interaction with proteins. The chemokine CXCL12α (or SDF-1α) rigidified the HS film, and this effect was due to protein-mediated cross-linking of HS chains. Complementary measurements with CXCL12α mutants and the CXCL12γ isoform provided insight into the molecular mechanism underlying cross-linking. Fibroblast growth factor 2 (FGF-2), which has three HS binding sites, was also found to cross-link HS, but FGF-9, which has just one binding site, did not. Based on these data, we propose that the ability to cross-link HS is a generic feature of many cytokines and growth factors, which depends on the architecture of their HS binding sites. The ability to change matrix organization and physico-chemical properties (e.g. permeability and rigidification) implies that the functions of cytokines and growth factors may not simply be confined to the activation of cognate cellular receptors. PMID:26269427

  1. Electrochemical Characterization of Ultrathin Cross-Linked Metal Nanoparticle Films.

    Science.gov (United States)

    Han, Chu; Percival, Stephen J; Zhang, Bo

    2016-09-06

    Here we report the preparation, characterization, and electrochemical study of conductive, ultrathin films of cross-linked metal nanoparticles (NPs). Nanoporous films ranging from 40 to 200 nm in thickness composed of gold and platinum NPs of ∼5 nm were fabricated via a powerful layer-by-layer spin coating process. This process allows preparation of uniform NP films as large as 2 × 2 cm(2) with precise control over thickness, structure, and electrochemical and electrocatalytic properties. Gold, platinum, and bimetallic NP films were fabricated and characterized using cyclic voltammetry, scanning electron microscopy, and conductance measurements. Their electrocatalytic activity toward the oxygen reduction reaction (ORR) was investigated. Our results show that the electrochemical activity of such NP films is initially hindered by the presence of dense thiolate cross-linking ligands. Both electrochemical cycling and oxygen plasma cleaning are effective means in restoring their electrochemical activity. Gold NP films have higher electric conductivity than platinum possibly due to more uniform film structure and closer particle-particle distance. The electrochemical and electrocatalytic performance of platinum NP films can be greatly enhanced by the incorporation of gold NPs. This work focuses on electrochemical characterization of cross-linked NP films and demonstrates several unique properties. These include quick and easy preparation, ultrathin and uniform film thickness, tunable structure and composition, and transferability to many other substrates.

  2. Late Stage of Corneal Decompensation Caused by Progressive Keratoconus: Can We Treat It and Save the Cornea?

    Directory of Open Access Journals (Sweden)

    Igor Knezović

    2015-01-01

    Full Text Available Aim. To report a case of 40-year-old male with progressive bilateral keratoconus who had undergone transepithelial phototherapeutic keratectomy (TE-PTK and corneal collagen cross-linking (CXL using hypoosmolar riboflavin solution in a same day procedure. Methods. Eye examination showed that UCDVA on both eyes was 0,01 according to Snellen charts, and slit lamp biomicroscopy showed paracentral diffuse intrastromal corneal haze. Anterior OCT marked stromal hyperreflective zones and localized paracentral thinning of the cornea. Scheimpflug tomography noted keratoconus stages III-IV on both eyes. After 40/35 microns TE-PTK, a CXL was performed for 30 minutes using hypoosmolar riboflavin solution. The left eye was treated first and the right eye 1 month after. Follow-up period was 10 months. Results. One month after the treatment both eyes showed improvement in corneal topography and the UCDVA was better. Eight months after the treatment BSCVA improved to 0,6 in both eyes using Rose K2 contact lenses and remained stable. Conclusion. TE-PTK and CXL using hypotonic riboflavin solution as a same day procedure have been shown to be a safe and promising method in this case of progressive keratoconus. It was necessary to consider certain parameters that could influence the safety and the final outcome of this combined protocol.

  3. Collagen derived serum markers in carcinoma of the prostate

    DEFF Research Database (Denmark)

    Rudnicki, M; Jensen, L T; Iversen, P

    1995-01-01

    Three new collagen markers deriving from the collagenous matrix, e.g. carboxyterminal propeptide of type I procollagen (PICP), carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP), and aminoterminal propeptide of type III procollagen (PIIINP) were used for the diagnose...

  4. Triple Combination of siRNAs Targeting TGFβ1, TGFβR2, and CTGF Enhances Reduction of Collagen I and Smooth Muscle Actin in Corneal Fibroblasts

    OpenAIRE

    Sriram, Sriniwas; Robinson, Paulette; Pi, Liya; Lewin, Alfred S.; Schultz, Gregory

    2013-01-01

    An optimized triple combination of siRNAs targeting TGFβ1, TGFβR2, and CTGF genes produced very high knockdown of target and downstream scarring genes (collagen and alpha smooth muscle actin) without cell toxicity, suggesting a new approach for reducing fibrosis in the cornea and other tissues.

  5. Macrophage response to cross-linked and conventional UHMWPE.

    Science.gov (United States)

    Sethi, Rajiv K; Neavyn, Mark J; Rubash, Harry E; Shanbhag, Arun S

    2003-07-01

    To prevent wear debris-induced osteolysis and aseptic loosening, cross-linked ultra-high molecular weight polyethylene's (UHMWPE) with improved wear resistance have been developed. Hip simulator studies have demonstrated very low wear rates with these new materials leading to their widespread clinical use. However, the biocompatibility of this material is not known. We studied the macrophage response to cross-linked UHMWPE (XLPE) and compared it to conventional UHMWPE (CPE) as well as other clinically used orthopaedic materials such as titanium-alloy (TiAlV) and cobalt-chrome alloy (CoCr). Human peripheral blood monocytes and murine macrophages, as surrogates for cells mediating peri-implant inflammation, were cultured onto custom designed lipped disks fabricated from the test materials to isolate cells. Culture supernatants were collected at 24 and 48h and analyzed for cytokines such as IL-1alpha, IL-1beta, TNF-alpha and IL-6. Total RNA was extracted from adherent cells and gene expression was analyzed using qualitative RT-PCR. In both in vitro models, macrophages cultured on cross-linked and conventional polyethylene released similar levels of cytokines, which were also similar to levels on control tissue culture dishes. Macrophages cultured on TiAlV and CoCr-alloy released significantly higher levels of cytokines. Human monocytes from all donors varied in the magnitude of cytokines released when cultured on identical surfaces. The variability in individual donor responses to TiAlV and CoCr surfaces may reflect how individuals respond differently to similar stimuli and perhaps reveal a predisposed sensitivity to particular materials.

  6. Optimization of protein cross-linking in bicomponent electrospun scaffolds for therapeutic use

    Energy Technology Data Exchange (ETDEWEB)

    Papa, Antonio [Institute for Polymers, Composites and Biomaterials, National Research Council of Italy (IPCB-CNR), V.le Kennedy 54, Naples 80125 (Italy); IMAST SCaRL, Piazza Bovio 22, 80133 Naples (Italy); Guarino, Vincenzo, E-mail: vincenzo.guarino@cnr.it; Cirillo, Valentina; Oliviero, Olimpia; Ambrosio, Luigi [Institute for Polymers, Composites and Biomaterials, National Research Council of Italy (IPCB-CNR), V.le Kennedy 54, Naples 80125 (Italy)

    2015-12-17

    Bio-instructive electrospun scaffolds based on the combination of synthetic polymers, such as PCL or PLLA, and natural polymers (e.g., collagen) have been extensively investigated as temporary extracellular matrix (ECM) analogues able to support cell proliferation and stem cell differentiation for the regeneration of several tissues. The growing use of natural polymers as carrier of bioactive molecules is introducing new ideas for the design of polymeric drug delivery systems based on electrospun fibers with improved bioavailability, therapeutic efficacy and programmed drug release. In particular, the release mechanism is driven by the use of water soluble proteins (i.e., collagen, gelatin) which fully degrade in in vitro microenvironment, thus delivering the active principles. However, these protein are generally rapidly digested by enzymes (i.e., collagenase) produced by many different cell types, both in vivo and in vitro with significant drawbacks in tissue engineering and controlled drug delivery. Here, we aim at investigating different chemical strategies to improve the in vitro stability and mechanical strength of scaffolds against enzymatic degradation, by modifying the biodegradation rates of proteins embedded in bicomponent fibers. By comparing scaffolds treated by different cross-linking agents (i.e., GC, EDC, BDDGE), we have provided an extensive morphological/chemical/physical characterization via SEM and TGA to identify the best conditions to control drug release via protein degradation from bicomponent fibers without compromising in vitro cell response.

  7. Release effect of the active ingredients using a radiation cross linking technology

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Seung Hyun; Ahn, Sung Jun; Park, Jong Seok; Jeong, Sung In; Gwon, Hui Jeong; Lim, Youn Mook [Research Division for Industry and Environment, Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of); Lee, Dong Yun [Dept. of Bioengineering, Division of Applied Chemical and Bio Engineering, Hanyang University, Seoul (Korea, Republic of)

    2015-12-15

    Typical radiation cross-linked hydrogels has the characteristic that high water content, but low emission efficiency of active ingredients. Therefore, the hydrogel was prepared by the addition to collagen, which is closely related to the formation of skin wrinkles in biocompatibility and highly water-soluble carboxymethyl cellulose sodium salt (CMC) in order to preparation of hydrogels has excellent emission efficiency of active ingredients. Hydrogels were prepared by dissolving CMC and collagen each of 0.5%, 10% concentration in deionized water. Then, prepared hydrogels are performed by gamma-radiation at 1, 3, 5 kGy irradiation dose. The results showed that the gel fraction of after irradiated 3 kGy hydrogel was higher than before irradiated gelation as long as the 55.3%. The swelling rate of irradiated 3 kGy hydrogel was lower than the non-irradiated sample. The compressive strength of 3 kGy irradiated hydrogel was the highest. The visco-elastic did not show any significant differences, even after irradiation. The CMC hydrogel in this study suggested a potential use as a material for the mask pack for improved emission efficiency of the active ingredient and anti-wrinkles.

  8. Optimization of protein cross-linking in bicomponent electrospun scaffolds for therapeutic use

    Science.gov (United States)

    Papa, Antonio; Guarino, Vincenzo; Cirillo, Valentina; Oliviero, Olimpia; Ambrosio, Luigi

    2015-12-01

    Bio-instructive electrospun scaffolds based on the combination of synthetic polymers, such as PCL or PLLA, and natural polymers (e.g., collagen) have been extensively investigated as temporary extracellular matrix (ECM) analogues able to support cell proliferation and stem cell differentiation for the regeneration of several tissues. The growing use of natural polymers as carrier of bioactive molecules is introducing new ideas for the design of polymeric drug delivery systems based on electrospun fibers with improved bioavailability, therapeutic efficacy and programmed drug release. In particular, the release mechanism is driven by the use of water soluble proteins (i.e., collagen, gelatin) which fully degrade in in vitro microenvironment, thus delivering the active principles. However, these protein are generally rapidly digested by enzymes (i.e., collagenase) produced by many different cell types, both in vivo and in vitro with significant drawbacks in tissue engineering and controlled drug delivery. Here, we aim at investigating different chemical strategies to improve the in vitro stability and mechanical strength of scaffolds against enzymatic degradation, by modifying the biodegradation rates of proteins embedded in bicomponent fibers. By comparing scaffolds treated by different cross-linking agents (i.e., GC, EDC, BDDGE), we have provided an extensive morphological/chemical/physical characterization via SEM and TGA to identify the best conditions to control drug release via protein degradation from bicomponent fibers without compromising in vitro cell response.

  9. DNA interstrand cross-linking by a mycotoxic diepoxide.

    Science.gov (United States)

    Millard, J T; Katz, J L; Goda, J; Frederick, E D; Pierce, S E; Speed, T J; Thamattoor, D M

    2004-06-01

    The diepoxide mycotoxin (2R, 3R, 8R, 9R)-4,6-decadiyne-2,3:8,9-diepoxy-1,10-diol (repandiol) was both isolated from the mushroom Hydnum repandum and synthesized de novo. Repandiol was found to form interstrand cross-links within a restriction fragment of DNA, linking deoxyguanosines on opposite strands primarily within the 5'-GNC and 5'-GNNC sequences preferred by diepoxyoctane. However, repandiol was a significantly less efficient cross-linker than either of the diepoxyalkanes (diepoxyoctane and diepoxybutane) to which it was compared.

  10. Probing native protein structures by chemical cross-linking, mass spectrometry, and bioinformatics.

    Science.gov (United States)

    Leitner, Alexander; Walzthoeni, Thomas; Kahraman, Abdullah; Herzog, Franz; Rinner, Oliver; Beck, Martin; Aebersold, Ruedi

    2010-08-01

    Chemical cross-linking of reactive groups in native proteins and protein complexes in combination with the identification of cross-linked sites by mass spectrometry has been in use for more than a decade. Recent advances in instrumentation, cross-linking protocols, and analysis software have led to a renewed interest in this technique, which promises to provide important information about native protein structure and the topology of protein complexes. In this article, we discuss the critical steps of chemical cross-linking and its implications for (structural) biology: reagent design and cross-linking protocols, separation and mass spectrometric analysis of cross-linked samples, dedicated software for data analysis, and the use of cross-linking data for computational modeling. Finally, the impact of protein cross-linking on various biological disciplines is highlighted.

  11. Corneal Laceration

    Science.gov (United States)

    ... drugs. These drugs thin the blood and may increase bleeding. After you have finished protecting the eye, see a physician immediately. Next Corneal Laceration Symptoms Related Ask an Ophthalmologist Answers I lost sight from a corneal scar as a child. Now that I’m older, ...

  12. Corneal Laceration

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration ... Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué Es una Laceración de la Córnea? Written ...

  13. Corneal Laceration

    Medline Plus

    Full Text Available ... Health Find an Ophthalmologist Academy Store Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask ... Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration Sections What Is Corneal Laceration? ...

  14. Corneal Laceration

    Medline Plus

    Full Text Available ... Health Find an Ophthalmologist Academy Store Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask ... Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration Sections What Is Corneal Laceration? ...

  15. Cross-linked comb-shaped anion exchange membranes with high base stability

    Energy Technology Data Exchange (ETDEWEB)

    Li, NW; Wang, LZ; Hickner, M

    2014-01-01

    A unique one-step cross-linking strategy that connects quaternary ammonium centers using Grubbs II-catalyzed olefin metathesis was developed. The cross-linked anion exchange membranes showed swelling ratios of less than 10% and hydroxide conductivities of 18 to 40 mS cm(- 1). Cross-linking improved the membranes' stability to hydroxide degradation compared to their non-cross-linked analogues.

  16. Cross-linking e segmento de anel corneano intraestromal

    Directory of Open Access Journals (Sweden)

    Adimara da Candelaria Renesto

    2011-02-01

    Full Text Available O cross-linking corneano é um procedimento usado para a estabilização mecânica e aumento da rigidez corneana em pacientes com ceratocone (reduzindo a possibilidade de progressão, e também em processos inflamatórios de afinamento corneano. Os segmentos de anéis corneanos intraestromais têm como princípio o aplanamento central da córnea. Inicialmente utilizados para correção de baixa miopia, a principal indicação atual é em pacientes com ceratocone, para melhorar a acuidade visual não corrigida, a acuidade visual corrigida e permitir uma melhor tolerância ao uso de lentes de contato como também retardar a necessidade de um transplante de córnea. O objetivo deste artigo é revisar algumas publicações relacionadas ao cross-linking corneano e à inserção do segmento de anel intraestromal, apresentando suas indicações, resultados e complicações relatadas até o momento.

  17. Fiber optic immunosensor for cross-linked fibrin concentration

    Science.gov (United States)

    Moskowitz, Samuel E.

    2000-08-01

    Working with calcium ions in the blood, platelets produce thromboplastin which transforms prothrombin into thrombin. Removing peptides, thrombin changes fibrinogen into fibrin. Cross-linked insoluble fibrin polymers are solubilized by enzyme plasmin found in blood plasma. Resulting D-dimers are elevated in patients with intravascular coagulation, deep venous thrombosis, pulmonary embolism, myocardial infarction, multiple trauma, cancer, impaired renal and liver functions, and sepsis. Consisting principally of a NIR 780 nm GaAlAs laser diode and a 800 nm avalanche photodiode (APD), the fiber-optic immunosensor can determined D-dimer concentration to levels detected by a second antibody which is labeled with NN 382 fluorescent dye. An evanescent wave traveling on an excitation optical fiber excites the antibody-antigen fluorophore complex. Concentration of cross-linked fibrin is directly proportional to the APD measured intensity of fluorescence. NIR fluorescence has advantages of low background interference, short fluorescence lifetime, and large difference between excitation and emission peaks. Competitive ELISA test for D-dimer concentration requires trained personnel performing a time consuming operation.

  18. Phosphate uptake studies of cross-linked chitosan bead materials.

    Science.gov (United States)

    Mahaninia, Mohammad H; Wilson, Lee D

    2017-01-01

    A systematic experimental study is reported that provides a molecular based understanding of cross-linked chitosan beads and their adsorption properties in aqueous solution containing phosphate dianion (HPO4(2-)) species. Synthetically modified chitosan using epichlorohydrin and glutaraldehyde cross-linkers result in surface modified beads with variable hydrophile-lipophile character and tunable HPO4(2-) uptake properties. The kinetic and thermodynamic adsorption properties of cross-linked chitosan beads with HPO4(2-) species were studied in aqueous solution. Complementary structure and physicochemical characterization of chitosan beads via potentiometry, Raman spectroscopy, DSC, and dye adsorption measurements was carried out to establish structure-property relationships. The maximum uptake (Qm) of bead systems with HPO4(2-) at equilibrium was 52.1mgg(-1); whereas, kinetic uptake results for chitosan bead/phosphate systems are relatively rapid (0.111-0.113min(-1)) with an intraparticle diffusion rate-limiting step. The adsorption process follows a multi-step pathway involving inner- and outer-sphere complexes with significant changes in hydration. Phosphate uptake strongly depends on the composition and type of cross-linker used for preparation of chitosan beads. The adsorption isotherms and structural characterization of bead systems illustrate the role of surface charge, hydrophile-lipophile balance, adsorption site accessibility, and hydration properties of the chitosan bead surface. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Adsorption of methyl orange onto protonated cross-linked chitosan

    Directory of Open Access Journals (Sweden)

    Ruihua Huang

    2017-01-01

    Full Text Available The adsorption of methyl orange (MO from aqueous solutions on protonated cross-linked chitosan was studied in a batch system. The results showed that the adsorption of MO onto protonated cross-linked chitosan was affected significantly by initial MO concentration, adsorbent dosage, adsorption temperature, and contact time. The pH value of solution had a minor impact on the adsorption of MO in a pH range of 1.0–9.1. The equilibrium isotherms at different temperatures (293, 303, and 313 K and pH values (4.5, 6.7, and 9.1 were investigated. Langmuir model was able to describe these Equilibrium data fitted perfectly. The maximum monolayer adsorption capacities obtained from the Langmuir model were 89.29, 130.9, and 180.2 mg/g at 293, 303, and 313 K, respectively. Adsorption kinetics at different concentrations (100, 200 and 300 mg/L and pH values (4.5, 6.7 and 9.1 were also studied. The kinetics was correlated well with the pseudo second-order model.

  20. Supermacroporous chemically cross-linked poly(aspartic acid) hydrogels.

    Science.gov (United States)

    Gyarmati, Benjámin; Mészár, E Zsuzsanna; Kiss, Lóránd; Deli, Mária A; László, Krisztina; Szilágyi, András

    2015-08-01

    Chemically cross-linked poly(aspartic acid) (PASP) gels were prepared by a solid-liquid phase separation technique, cryogelation, to achieve a supermacroporous interconnected pore structure. The precursor polymer of PASP, polysuccinimide (PSI) was cross-linked below the freezing point of the solvent and the forming crystals acted as templates for the pores. Dimethyl sulfoxide was chosen as solvent instead of the more commonly used water. Thus larger temperatures could be utilized for the preparation and the drawback of increase in specific volume of water upon freezing could be eliminated. The morphology of the hydrogels was characterized by scanning electron microscopy and interconnectivity of the pores was proven by the small flow resistance of the gels. Compression tests also confirmed the interconnected porous structure and the complete re-swelling and shape recovery of the supermacroporous PASP hydrogels. The prepared hydrogels are of interest for several biomedical applications as scaffolding materials because of their cytocompatibility, controllable morphology and pH-responsive character.

  1. Covalently Cross-Linked Arabinoxylans Films for Debaryomyces hansenii Entrapment

    Directory of Open Access Journals (Sweden)

    Ramsés González-Estrada

    2015-06-01

    Full Text Available In the present study, wheat water extractable arabinoxylans (WEAX were isolated and characterized, and their capability to form covalently cross-linked films in presence of Debaryomyces hansenii was evaluated. WEAX presented an arabinose to xylose ratio of 0.60, a ferulic acid and diferulic acid content of 2.1 and 0.04 µg∙mg−1 WEAX, respectively and a Fourier Transform Infra-Red (FT-IR spectrum typical of WEAX. The intrinsic viscosity and viscosimetric molecular weight values for WEAX were 3.6 dL∙g−1 and 440 kDa, respectively. The gelation of WEAX (1% w/v with and without D. hansenii (1 × 107 CFU∙cm−2 was rheologically investigated by small amplitude oscillatory shear. The entrapment of D. hansenii decreased gel elasticity from 1.4 to 0.3 Pa, probably by affecting the physical interactions between WEAX chains. Covalently cross-linked WEAX films containing D. hansenii were prepared by casting. Scanning electron microscopy images show that WEAX films containing D. hansenii were porous and consisted of granular-like and fibre microstructures. Average tensile strength, elongation at break and Young’s modulus values dropped when D. hansenii was present in the film. Covalently cross-lined WEAX containing D. hansenii could be a suitable as a functional entrapping film.

  2. One-step electrospinning of cross-linked chitosan fibers.

    Science.gov (United States)

    Schiffman, Jessica D; Schauer, Caroline L

    2007-09-01

    Chitin is a nitrogen-rich polysaccharide that is abundant in crustaceans, mollusks, insects, and fungi and is the second most abundant organic material found in nature next to cellulose. Chitosan, the N-deacetylated derivative of chitin, is environmentally friendly, nontoxic, biodegradable, and antibacterial. Fibrous mats are typically used in industries for filter media, catalysis, and sensors. Decreasing fiber diameters within these mats causes many beneficial effects such as increased specific surface area to volume ratios. When the intrinsically beneficial effects of chitosan are combined with the enhanced properties of nanofibrous mats, applications arise in a wide range of fields, including medical, packaging, agricultural, and automotive. This is particularly important as innovative technologies that focus around bio-based materials are currently of high urgency, as they can decrease dependencies on fossil fuels. We have demonstrated that Schiff base cross-linked chitosan fibrous mats can be produced utilizing a one-step electrospinning process that is 25 times faster and, therefore, more economical than a previously reported two-step vapor-cross-linking method. These fibrous mats are insoluble in acidic, basic, and aqueous solutions for 72 h. Additionally, this improved production method results in a decreased average fiber diameter, which measures 128 +/- 40 nm. Chemical and structural analyses were conducted utilizing Fourier transform infrared spectroscopy, solubility studies, and scanning electron microscopy.

  3. Tea derived galloylated polyphenols cross-link purified gastrointestinal mucins.

    Directory of Open Access Journals (Sweden)

    Pantelis Georgiades

    Full Text Available Polyphenols derived from tea are thought to be important for human health. We show using a combination of particle tracking microrheology and small-angle neutron scattering that polyphenols acts as cross-linkers for purified gastrointestinal mucin, derived from the stomach and the duodenum. Both naturally derived purified polyphenols, and green and black tea extracts are shown to act as cross-linkers. The main active cross-linking component is found to be the galloylated forms of catechins. The viscosity, elasticity and relaxation time of the mucin solutions experience an order of magnitude change in value upon addition of the polyphenol cross-linkers. Similarly small-angle neutron scattering experiments demonstrate a sol-gel transition with the addition of polyphenols, with a large increase in the scattering at low angles, which is attributed to the formation of large scale (>10 nm heterogeneities during gelation. Cross-linking of mucins by polyphenols is thus expected to have an impact on the physicochemical environment of both the stomach and duodenum; polyphenols are expected to modulate the barrier properties of mucus, nutrient absorption through mucus and the viscoelastic microenvironments of intestinal bacteria.

  4. Thermally Cross-Linked Anion Exchange Membranes from Solvent Processable Isoprene Containing Ionomers

    Science.gov (United States)

    2015-01-15

    capacities (IECs). Solution cast membranes were thermally cross- linked to form anion exchange membranes. Cross-linking was achieved by taking advantage...distribution is unlimited. Thermally Cross-Linked Anion Exchange Membranes from Solvent Processable Isoprene Containing Ionomers The views...Box 12211 Research Triangle Park, NC 27709-2211 Anion Exchnage Membrane, Polymer synthesis, Morphology, Anion Conductivity REPORT DOCUMENTATION PAGE

  5. Small Strain Topological Effects of Biopolymer Networks with Rigid Cross-Links

    NARCIS (Netherlands)

    Zagar, G.; Onck, P. R.; Van der Giessen, E.; Garikipati, K; Arruda, EM

    2010-01-01

    Networks of cross-linked filamentous biopolymers form topological structures characterized by L, T and X cross-link types of connectivity 2, 3 and 4, respectively. The distribution of cross-links over these three types proofs to be very important for the initial elastic shear stiffness of isotropic

  6. Short duration gluteraldehyde cross linking of decellularized bovine pericardium improves biological response.

    Science.gov (United States)

    Umashankar, P R; Arun, T; Kumari, T V

    2011-06-01

    Gluteraldehyde stabilized bovine pericardium is used for clinical application since 1970s because of its desirable features such as less immunogenicity and acceptable durability. However, a propensity for calcification and long term implant failure is reported because of gluteraldehyde treatment. There is also failure of implant to integrate into host tissue because of its resistance to tissue remodeling. Decellularized bovine pericardium, a potential alternative allows tissue remodeling but it has problems such as immunogenicity and chronic inflammatory response. In this study, decellularized bovine pericardium was subjected to short duration, low concentration gluteraldehyde cross-linking at two levels and its biological response (both in vitro and in vivo) was compared with un-crosslinked decellularized bovine pericardium and fully crosslinked normal bovine pericardium. It was observed that both un-crosslinked and partially crosslinked decellularized bovine pericardium to be non-cytotoxic and it caused significantly less inflammatory cytokine release such as TNF alpha and IL1beta from activated macrophages. Among all groups, short duration 0.2% Gluteraldehyde treated decellularized bovine pericardium showed significantly less antibody response and inflammatory response compared to un-crosslinked decellularized pericardium, short duration 0.6% gluteraldehyde treated decellularized bovine pericardium or completely cross linked bovine pericardium in juvenile rat subcutaneous implantation model. Moreover, short duration 0.2% gluteraldehyde crosslinked decellularized bovine pericardium showed minimum calcification, better host fibroblast incorporation, new collagen deposition and angiogenesis within the implant. These attributes may finally lead to better implant remodeling and sustained implant function during clinical use. Copyright © 2011 Wiley Periodicals, Inc.

  7. Use of cross-linked carboxymethyl cellulose for soft-tissue augmentation: preliminary clinical studies

    Directory of Open Access Journals (Sweden)

    Mauro Leonardis

    2010-11-01

    Full Text Available Mauro Leonardis1, Andrea Palange2, Rodrigo FV Dornelles3, Felipe Hund41Department of Plastic Surgery, Salvator Mundi International Hospital, Roma, Italy; 2Department of Aesthetic Medicine, Fisiobios, Roma, Italy; 3Department of Plastic Surgery, Núcleo de Plástica Avançada, São Paulo, SP, Brazil; 4Department of Plastic Surgery, Consultorio de Cirurgia Plastica, Criciuma, SC, BrazilPurpose: The continual search for new products for soft-tissue augmentation has in recent years led to the introduction of long lasting alternatives to hyaluronic acids and collagen that are composed of other polymers able to improve clinical persistence over time. This is the first report in which sodium carboxymethyl cellulose (CMC has been chemically treated by the cross-linking process and thus used as a hydrogel for soft-tissue augmentation through injection with thin needles. The study evaluates, from a clinical point of view, the behavior of cross-linked carboxymethyl cellulose hydrogel used in the aesthetic field and its side effects so as to check the safety and performance of the polymer following intradermal injections.Patients and methods: This work shows the preliminary results of an ongoing clinical study conducted between 2006 and 2009, performed on 84 healthy volunteers (62 females, 22 males aged between 18 and 72 years, for the treatment of 168 nasolabial folds, 45 perioral wrinkles, and 39 lip volume.Results: Study results show an excellent correction of facial defects. Tolerance and aesthetic quality of the correction obtained indicate considerable safety features and absence of side effects. From a clinical point of view, hydrogel is gradually absorbed into the injection site without migration issues.Conclusion: Cross-linked CMC hydrogel proves to be an ideal agent for soft tissue augmentation with regard to safety and ease of application. It did not cause infection, extrusion, migration, or adverse reactions in the patients who have been

  8. KIOM-79, an Inhibitor of AGEs–Protein Cross-linking, Prevents Progression of Nephropathy in Zucker Diabetic Fatty Rats

    Directory of Open Access Journals (Sweden)

    Young Sook Kim

    2011-01-01

    Full Text Available Advanced glycation end products (AGEs have been implicated in the development of diabetic complications, including diabetic nephropathy. KIOM-79, an 80% ethanolic extract obtained from parched Puerariae Radix, gingered Magnolia Cortex, Glycyrrhiza Radix and Euphorbia Radix, was investigated for its effects on the development of renal disease in Zucker diabetic fatty rats, an animal model of type 2 diabetes. In vitro inhibitory effect of KIOM-79 on AGEs cross-linking was examined by enzyme-linked immunosorbent assay (ELISA. KIOM-79 (50 mg/kg/day was given to Zucker diabetic fatty rats for 13 weeks. Body and kidney weight, blood glucose, glycated hemoglobin, urinary albumin and creatinine excretions were monitored. Kidney histopathology, collagen accumulation, fibrinogen and transforming growth factor-beta 1 (TGF-β1 expression were also examined. KIOM-79 reduced blood glucose, kidney weight, histologic renal damage and albuminuria in Zucker diabetic fatty rats. KIOM-79 prevented glomerulosclerosis, tubular degeneration, collagen deposition and podocyte apoptosis. In the renal cortex, TGF-β1, fibronectin mRNA and protein were significantly reduced by KIOM-79 treatment. KIOM-79 reduces AGEs accumulation in vivo, AGE–protein cross-linking and protein oxidation. KIOM-79 could be beneficial in preventing the progression of diabetic glomerularsclerosis in type 2 diabetic rats by attenuating AGEs deposition in the glomeruli.

  9. Cross-linked hyaluronic acid in pressure ulcer prevention.

    Science.gov (United States)

    Beniamino, P; Vadalà, M; Laurino, C

    2016-07-02

    Long-term bedridden patients are at high risk of acquring pressure ulcers (PUs). In this group of patients, prevention is necessary to cut the health costs, improve quality of life and reduce the mortality. Here, we evaluated the effectiveness of a cross-linked hyaluronic acid (HA) as plastic bulking-agent filling and remodelling the deep dermis and subcutaneous space of the skin areas exposed to the risk of necrosis. Our work hypothesis has been to inflate a sub-dermal elastic cushion, filled with a natural ECM component, with the aim to induce a stronger tissue background resistant to the ulcerative process. All the patients had an increased risk of PUs, at the sacral, ileum or heel skin. Patients were being nursed accordingly to the standard orthopaedic ward management with a pressure relieveing air mattress. The standard protocol consisted in body mobilisation every 3 hours, 24 hours a day and accurate cleaning of the skin with liquid soap and water without any towel friction and without adding any cream or lotion for the skin protection. Our filling protocol enclosed: accurate disinfection of the skin to be injected with povidone-iodine solution, followed by a local anaesthesia with 28G 13 mm needle, injecting 1.5 ml of 1% xylocaine. Then slow, deep, subcutaneous injection of cross-linked HA was performed with a 18G long needle, in order to deliver a homogeneous, soft gel layer underneath and around the whitish erythematous skin edges at risk of ulceration. Patients' tolerability of the compound and adverse events were also recorded. There were 15 patients (78-94 years old) who participated in the study. All tolerated the procedure very well and no serious side effects were declared. No skin pressure ulceration was detected in the four weeks follow-up Conclusion: We have demonstrated the safety and tolerability of a cross-linked HA subdermal injection in PUs prevention. The compound stratifies in a soft, elastic, interstitial bulk into the deep dermis, thus

  10. Biocatalytic cross-linking of pectic polysaccharides for designed food functionality

    DEFF Research Database (Denmark)

    Zaidel, Dayang Norulfairuz Abang; Meyer, Anne S.

    2012-01-01

    Recent research has demonstrated how cross-linking of pectic polysaccharides to obtain gel formation can be promoted by enzymatic catalysis reactions, and provide opportunities for functional upgrading of pectic polysaccharides present in agro-industrial sidestreams. This review highlights...... the mechanisms of formation of functional pectic polysaccharide cross-links, including covalent cross-links (notably phenolic esters and uronyl ester linkages) and non-covalent, ionic cross-links (which involve calcium and borate ester links). The treatise examines how such cross-links can be designed via...

  11. Stiffening of semiflexible biopolymers and cross-linked networks

    CERN Document Server

    Van Dillen, T; Van der Giessen, E

    2006-01-01

    We study the mechanical stiffening behavior in two-dimensional (2D) cross-linked networks of semiflexible biopolymer filaments under simple shear. Filamental constituents immersed in a fluid undergo thermally excited bending motions. Pulling out these undulations results in an increase in the axial stiffness. We analyze this stiffening behavior of 2D semiflexible filaments in detail: we first investigate the average, {static} force-extension relation by considering the initially present undulated configuration that is pulled straight under a tensile force, and compare this result with the average response in which undulation dynamics is allowed during pulling, as derived earlier by MacKintosh and coworkers. We will show that the resulting mechanical behavior is rather similar, but with the axial stiffness being a factor 2 to 4 larger in the dynamic model. Furthermore, we study the stretching contribution in case of extensible filaments and show that, for 2D filaments, the mechanical response is dominated by {...

  12. Swelling properties of cross-linked DNA gels.

    Science.gov (United States)

    Costa, Diana; Miguel, M Graça; Lindman, Björn

    2010-07-12

    This work represents our contribution to the field of physical chemistry of DNA gels, and concerns the synthesis and study of novel chemically cross-linked DNA gels. The use of covalent DNA gels is a very promising way to study DNA-cosolute interactions, as well as the dynamic behaviour of DNA and cationic compacting agents, like lipids, surfactants and polycations. Manipulating DNA in new ways, like DNA networks, allows a better understanding and characterization of DNA-cosolute complexes at the molecular level, and also allows us to follow the assembly structures of these complexes. The use of responsive polymer gels for targeted delivery of toxic and/or labile drugs has, during the past few years, shown to be a promising concept. The features found in the proposed system would find applications in a broader field of gel/drug interaction, for the development of controlled release and targeted delivery devices.

  13. Conventional Versus Cross-Linked Polyethylene for Total Hip Arthroplasty.

    Science.gov (United States)

    Surace, Michele F; Monestier, Luca; Vulcano, Ettore; Harwin, Steven F; Cherubino, Paolo

    2015-09-01

    The clinical and radiographic outcomes of 88 patients who underwent primary total hip arthroplasty with either conventional polyethylene or cross-linked polyethylene (XLPE) from the same manufacturer were compared. There were no significant differences between the 2 subpopulations regarding average age, gender, side affected, or prosthetic stem and cup size. The average follow-up was 104 months (range, 55 to 131 months). To the authors' knowledge, this is the longest follow-up for this particular insert. Clinical and radiographic evaluations were performed at 1, 3, 6, and 12 months and then annually. Results showed that XLPE has a significantly greater wear reduction than that of standard polyethylene in primary total hip arthroplasty. At the longest available follow-up for these specific inserts, XLPE proved to be effective in reducing wear.

  14. Studies on N-vinylformamide cross-linked copolymers

    Science.gov (United States)

    Świder, Joanna; Tąta, Agnieszka; Sokołowska, Katarzyna; Witek, Ewa; Proniewicz, Edyta

    2015-12-01

    Copolymers of N-vinylformamide (NVF) cross-linked with three multifunctional monomers, including divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA), and N,N‧-methylenebisacrylamide (MBA) were synthetized by a three-dimensional free radical polymerization in inverse suspension using 2,2‧-azobis(2-methylpropionamide) dihydrochloride (AIBA) as an initiator. Methyl silicon oil was used as the continuous phase during the polymerization processes. Fourier-transform adsorption infrared (FT-IR) spectra revealed the presence of silicone oil traces and suggested that silicone oil strongly interacted with the copolymers surface. Purification procedure allowed to completely remove the silicon oil traces from P(NVF-co-DVB) only. The morphology and the structure of the investigated copolymers were examined by optical microscopy, FT-IR, and FT-Raman (Fourier-transform Raman spectroscopy) methods.

  15. Grass Cell Walls: A Story of Cross-Linking

    Science.gov (United States)

    Hatfield, Ronald D.; Rancour, David M.; Marita, Jane M.

    2017-01-01

    Cell wall matrices are complex composites mainly of polysaccharides, phenolics (monomers and polymers), and protein. We are beginning to understand the synthesis of these major wall components individually, but still have a poor understanding of how cell walls are assembled into complex matrices. Valuable insight has been gained by examining intact components to understand the individual elements that make up plant cell walls. Grasses are a prominent group within the plant kingdom, not only for their important roles in global agriculture, but also for the complexity of their cell walls. Ferulate incorporation into grass cell wall matrices (C3 and C4 types) leads to a cross-linked matrix that plays a prominent role in the structure and utilization of grass biomass compared to dicot species. Incorporation of p-coumarates as part of the lignin structure also adds to the complexity of grass cell walls. Feruoylation results in a wall with individual hemicellulosic polysaccharides (arabinoxylans) covalently linked to each other and to lignin. Evidence strongly suggests that ferulates not only cross-link arabinoxylans, but may be important factors in lignification of the cell wall. Therefore, the distribution of ferulates on arabinoxylans could provide a means of structuring regions of the matrix with the incorporation of lignin and have a significant impact upon localized cell wall organization. The role of other phenolics in cell wall formation such as p-coumarates (which can have concentrations higher than ferulates) remains unknown. It is possible that p-coumarates assist in the formation of lignin, especially syringyl rich lignin. The uniqueness of the grass cell wall compared to dicot sepcies may not be so much in the gross composition of the wall, but how the distinctive individual components are organized into a functional wall matrix. These features are discussed and working models are provided to illustrate how changing the organization of feruoylation and p

  16. Peptidoglycan Cross-Linking in Glycopeptide-Resistant Actinomycetales

    Science.gov (United States)

    Hugonnet, Jean-Emmanuel; Haddache, Nabila; Veckerlé, Carole; Dubost, Lionel; Marie, Arul; Shikura, Noriyasu; Mainardi, Jean-Luc; Rice, Louis B.

    2014-01-01

    Synthesis of peptidoglycan precursors ending in d-lactate (d-Lac) is thought to be responsible for glycopeptide resistance in members of the order Actinomycetales that produce these drugs and in related soil bacteria. More recently, the peptidoglycan of several members of the order Actinomycetales was shown to be cross-linked by l,d-transpeptidases that use tetrapeptide acyl donors devoid of the target of glycopeptides. To evaluate the contribution of these resistance mechanisms, we have determined the peptidoglycan structure of Streptomyces coelicolor A(3)2, which harbors a vanHAX gene cluster for the production of precursors ending in d-Lac, and Nonomuraea sp. strain ATCC 39727, which is devoid of vanHAX and produces the glycopeptide A40296. Vancomycin retained residual activity against S. coelicolor A(3)2 despite efficient incorporation of d-Lac into cytoplasmic precursors. This was due to a d,d-transpeptidase-catalyzed reaction that generated a stem pentapeptide recognized by glycopeptides by the exchange of d-Lac for d-Ala and Gly. The contribution of l,d-transpeptidases to resistance was limited by the supply of tetrapeptide acyl donors, which are essential for the formation of peptidoglycan cross-links by these enzymes. In the absence of a cytoplasmic metallo-d,d-carboxypeptidase, the tetrapeptide substrate was generated by hydrolysis of the C-terminal d-Lac residue of the stem pentadepsipeptide in the periplasm in competition with the exchange reaction catalyzed by d,d-transpeptidases. In Nonomuraea sp. strain ATCC 39727, the contribution of l,d-transpeptidases to glycopeptide resistance was limited by the incomplete conversion of pentapeptides into tetrapeptides despite the production of a cytoplasmic metallo-d,d-carboxypeptidase. Since the level of drug production exceeds the level of resistance, we propose that l,d-transpeptidases merely act as a tolerance mechanism in this bacterium. PMID:24395229

  17. The wear of cross-linked polyethylene against itself.

    Science.gov (United States)

    Joyce, T J; Ash, H E; Unsworth, A

    1996-01-01

    Cross-linked polyethylene (XLPE) may have an application as a material for an all-plastic surface replacement finger joint. It is inexpensive, biocompatible and can be injection-moulded into the complex shapes that are found on the ends of the finger bones. Further, the cross-linking of polyethylene has significantly improved its mechanical properties. Therefore, the opportunity exists for an all-XLPE joint, and so the wear characteristics of XLPE sliding against itself have been investigated. Wear tests were carried out on both reciprocating pin-on-plate machines and a finger function simulator. The reciprocating pin-on-plate machines had pins loaded at 10 N and 40 N. All pin-on-plate tests show wear factors from the plates very much greater than those of the pins. After 349 km of sliding, a mean wear factor of 0.46 x 10(-6) mm3/N m was found for the plates compared with 0.021 x 10(-6) mm3/N m for the pins. A fatigue mechanism may be causing this phenomenon of greater plate wear. Tests using the finger function simulator give an average wear rate of 0.22 x 10(-6) mm3/N m after 368 km. This sliding distance is equivalent to 12.5 years of use in vivo. The wear factors found were comparable with those of ultra-high molecular weight polyethylene (UHMWPE) against a metallic counterface and, therefore, as the loads across the finger joint are much less than those across the knee or the hip, it is probable that an all-XLPE finger joint will be viable from a wear point of view.

  18. Anisotropic Thermal Conductivity Measurements on Cross-Linked Polybutadienes in Uniaxial Elongation

    Science.gov (United States)

    Venerus, David C.; Kolev, Dimitre

    2008-07-01

    Cross-linked elastomers have numerous applications including automobiles, sporting goods, and biomedical devices. During both their processing and application, these materials experience large mechanical stresses and thermal gradients. In this study, we investigate the mechanical and thermal transport behavior of cross-linked polybutadienes. These materials have been prepared by cross linking well-entangled polybutadienes using an organic peroxide cross-linking agent at low concentration. Samples obtained after nearly complete conversion of the cross-linking agent, which can be characterized as lightly cross-linked (i.e., more than 10 entanglements per cross-link), were subjected to a series of large strain, uniaxial deformations. Measurements of the tensile stress and two components of the thermal conductivity tensor will be reported as a function of elongation. These data are also used to examine the stress-thermal rule in which the stress and thermal conductivity tensors are linearly related.

  19. Yield and Failure Behavior Investigated for Cross-Linked Phenolic Resins Using Molecular Dynamics

    Science.gov (United States)

    Monk, Joshua D.; Lawson, John W.

    2016-01-01

    Molecular dynamics simulations were conducted to fundamentally evaluate the yield and failure behavior of cross-linked phenolic resins at temperatures below the glass transition. Yield stress was investigated at various temperatures, strain rates, and degrees of cross-linking. The onset of non-linear behavior in the cross-linked phenolic structures was caused by localized irreversible molecular rearrangements through the rotation of methylene linkers followed by the formation or annihilation of neighboring hydrogen bonds. The yield stress results, with respect to temperature and strain rate, could be fit by existing models used to describe yield behavior of amorphous glasses. The degree of cross-linking only indirectly influences the maximum yield stress through its influence on glass transition temperature (Tg), however there is a strong relationship between the degree of cross-linking and the failure mechanism. Low cross-linked samples were able to separate through void formation, whereas the highly cross-linked structures exhibited bond scission.

  20. Nanoscale modification of porous gelatin scaffolds with chondroitin sulfate for corneal stromal tissue engineering

    Directory of Open Access Journals (Sweden)

    Lai JY

    2012-02-01

    Full Text Available Jui-Yang Lai*, Ya-Ting Li*, Ching-Hsien Cho, Ting-Chun Yu Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan, Republic of China*These authors contributed equally to this workAbstract: Recent studies reflect the importance of using naturally occurring biopolymers as three-dimensional corneal keratocyte scaffolds and suggest that the porous structure of gelatin materials may play an important role in controlling nutrient uptake. In the current study, the authors further consider the application of carbodiimide cross-linked porous gelatin as an alternative to collagen for corneal stromal tissue engineering. The authors developed corneal keratocyte scaffolds by nanoscale modification of porous gelatin materials with chondroitin sulfate (CS using carbodiimide chemistry. Scanning electron microscopy/energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy showed that the amount of covalently incorporated polysaccharide was significantly increased when the CS concentration was increased from 0% to 1.25% (w/v. In addition, as demonstrated by dimethylmethylene blue assays, the CS content in these samples was in the range of 0.078–0.149 nmol per 10 mg scaffold. When compared with their counterparts without CS treatment, various CS-modified porous gelatin membranes exhibited higher levels of water content, light transmittance, and amount of permeated nutrients but possessed lower Young’s modulus and resistance against protease digestion. The hydrophilic and mechanical properties of scaffolds modified with 0.25% CS were comparable with those of native corneas. The samples from this group were biocompatible with the rabbit corneal keratocytes and showed enhanced proliferative and biosynthetic capacity of cultured cells. In summary, the authors found that the nanoscale-level modification has influence on the characteristics and cell-material interactions of CS-containing gelatin hydrogels

  1. Mass spectrometric analysis of a UV-cross-linked protein-DNA complex: tryptophans 54 and 88 of E. coli SSB cross-link to DNA

    DEFF Research Database (Denmark)

    Steen, H; Petersen, J; Mann, M

    2001-01-01

    Protein-nucleic acid complexes are commonly studied by photochemical cross-linking. UV-induced cross-linking of protein to nucleic acid may be followed by structural analysis of the conjugated protein to localize the cross-linked amino acids and thereby identify the nucleic acid binding site. Mass....... coli single-stranded DNA binding protein (SSB) that was UV-cross-linked to a 5-iodouracil containing DNA oligomer. Two methods were optimized to circumvent the need for standard liquid chromatography and gel electrophoresis, thereby dramatically increasing the overall sensitivity of the analysis....... Enzymatic degradation of protein and oligonucleotide was combined with miniaturized sample preparation methods for enrichment and desalting of cross-linked peptide-nucleic acid heteroconjugates from complex mixtures prior to mass spectrometric analysis. Detailed characterization of the peptidic component...

  2. Corneal Laceration

    Medline Plus

    Full Text Available ... from Laundry Packets On the Rise Jun 30, 2017 People with Advanced Keratoconus May Have A Future Alternative to Full Corneal Transplantation Nov 29, 2016 Combating Eye Injuries from Air Guns Aug 30, ...

  3. Corneal transplant

    Science.gov (United States)

    ... lenses to achieve the best vision. Laser vision correction may be an option if you have nearsightedness, ... Editorial team. Related MedlinePlus Health Topics Corneal Disorders Refractive Errors Browse the Encyclopedia A.D.A.M., Inc. ...

  4. Corneal Laceration

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    Full Text Available ... Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide ... What Is Corneal Laceration? Leer en Español: ¿Qué ...

  5. Corneal Laceration

    Medline Plus

    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... Dangerous for Your Eyes Sep 20, 2017 Eye Injuries from Laundry Packets On the Rise Jun 30, ...

  6. Corneal Laceration

    Medline Plus

    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... 27, 2015 Dark Spot in Vision After Blunt Trauma Dec 21, 2014 Pain a Year After Eyelid ...

  7. Corneal Laceration

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    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... and preserving your vision. Privacy Policy Related Eye Injuries from Laundry Packets On the Rise Jun 30, ...

  8. Corneal Laceration

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    Full Text Available ... 2017 People with Advanced Keratoconus May Have A Future Alternative to Full Corneal Transplantation Nov 29, 2016 Combating Eye Injuries from Air Guns Aug 30, ... Public & Patients: Contact Us About ...

  9. Corneal Laceration

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    Full Text Available ... by something sharp flying into the eye. It can also be caused by something striking the eye ... If the corneal laceration is deep enough it can cause a full thickness laceration. This is when ...

  10. Corneal Laceration

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    Full Text Available ... Pediatric Ophthalmology Education Center Oculofacial Plastic Surgery Center Laser Surgery Education Center Redmond Ethics Center Global Ophthalmology Guide ... What Is Corneal Laceration? Written By: Daniel Porter ...

  11. Corneal Laceration

    Medline Plus

    Full Text Available ... By: Devin A Harrison MD Sep. 01, 2017 The cornea is the clear front window of the eye . A corneal laceration is a cut on the cornea. It is usually caused by something sharp ...

  12. Corneal Laceration

    Medline Plus

    Full Text Available ... itself. A corneal laceration is a very serious injury and requires immediate medical attention to avoid severe ... 27, 2015 Dark Spot in Vision After Blunt Trauma Dec 21, 2014 Pain a Year After Eyelid ...

  13. Enhancing amine terminals in an amine-deprived collagen matrix.

    LENUS (Irish Health Repository)

    Tiong, William H C

    2008-10-21

    Collagen, though widely used as a core biomaterial in many clinical applications, is often limited by its rapid degradability which prevents full exploitation of its potential in vivo. Polyamidoamine (PAMAM) dendrimer, a highly branched macromolecule, possesses versatile multiterminal amine surface groups that enable them to be tethered to collagen molecules and enhance their potential. In this study, we hypothesized that incorporation of PAMAM dendrimer in a collagen matrix through cross-linking will result in a durable, cross-linked collagen biomaterial with free -NH 2 groups available for further multi-biomolecular tethering. The aim of this study was to assess the physicochemical properties of a G1 PAMAM cross-linked collagen matrix and its cellular sustainability in vitro. Different amounts of G1 PAMAM dendrimer (5 or 10 mg) were integrated into bovine-derived collagen matrices through a cross-linking process, mediated by 5 or 25 mM 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) in 5 mM N-hydroxysuccinimide (NHS) and 50 mM 2-morpholinoethane sulfonic acid buffer at pH 5.5. The physicochemical properties of resultant matrices were investigated with scanning electron microscopy (SEM), collagenase degradation assay, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectra, and ninhydrin assay. Cellular sustainability of the matrices was assessed with Alamar Blue assay and SEM. There was no significant difference in cellular behavior between the treated and nontreated groups. However, the benefit of incorporating PAMAM in the cross-linking reaction was limited when higher concentrations of either agent were used. These results confirm the hypothesis that PAMAM dendrimer can be incorporated in the collagen cross-linking process in order to modulate the properties of the resulting cross-linked collagen biomaterial with free -NH 2 groups available for multi-biomolecular tethering.

  14. Effect of substrate composition and alignment on corneal cell phenotype.

    Science.gov (United States)

    Phu, Donna; Wray, Lindsay S; Warren, Robert V; Haskell, Richard C; Orwin, Elizabeth J

    2011-03-01

    Corneal blindness is a significant problem treated primarily by corneal transplants. Donor tissue supply is low, creating a growing need for an alternative. A tissue-engineered cornea made from patient-derived cells and biopolymer scaffold materials would be widely accessible to all patients and would alleviate the need for donor sources. Previous work in this lab led to a method for electrospinning type I collagen scaffolds for culturing corneal fibroblasts ex vivo that mimics the microenvironment in the native cornea. This electrospun scaffold is composed of small-diameter, aligned collagen fibers. In this study, we investigate the effect of scaffold nanostructure and composition on the phenotype of corneal stromal cells. Rabbit-derived corneal fibroblasts were cultured on aligned and unaligned collagen type I fibers ranging from 50 to 300 nm in diameter and assessed for expression of α-smooth muscle actin, a protein marker upregulated in hazy corneas. In addition, the optical properties of the cell-matrix constructs were assessed using optical coherence microscopy. Cells grown on collagen scaffolds had reduced myofibroblast phenotype expression compared to cells grown on tissue culture plates. Cells grown on aligned collagen type I fibers downregulated α-smooth muscle actin protein expression significantly more than unaligned collagen scaffolds, and also exhibited reduced overall light scattering by the tissue construct. These results suggest that aligned collagen type I fibrous scaffolds are viable platforms for engineering corneal replacement tissue.

  15. Collagen cross-linkage: a comprehensive review and directions for future research.

    Science.gov (United States)

    Ashwin, P T; McDonnell, P J

    2010-08-01

    Individuals with keratoconus form a significant proportion of patients for a practitioner specialising in corneal diseases. Yet it is a disease where the pathogenesis is poorly understood, and until recently, there has been no treatment apart from transplantation that could be offered that was curative or even capable of slowing the progression of the disease. Collagen cross-linking treatment using riboflavin and UV light has been developed to address this need, and the initial results are promising. The purpose of this review is to critically evaluate this treatment in light of the scientific basis for cross-linking, to highlight the strengths and limitations of the evidence in terms of efficacy and long-term safety, and finally to identify areas for future research in this area with a significant potential to change the way we treat our keratoconus patients. In addition, we hope that our unbiased review for the first time would bring together, in a concise fashion, scientific information for a practitioner contemplating on offering this treatment and to help inform their patients of its potential risks and benefits.

  16. Spontaneous corneal melting in pregnancy: a case report

    Directory of Open Access Journals (Sweden)

    Arya Sudesh K

    2007-11-01

    Full Text Available Abstract Background To report a case of spontaneous corneal melting in pregnancy. We reviewed the literature on corneal melting and the effect of pregnancy on cornea and collagen containing tissues. Case presentation A 29-year-old woman who underwent radial keratotomy in both eyes followed by trabeculectomy in her left eye developed corneal melting in the same eye, in her seventh month of pregnancy. Despite screening, no infectious or immune mediated condition could be identified. She was managed conservatively with cyanoacrylate glue, bandage contact lens, lubricants and antibiotics. Conclusion It may not always be possible to find the underlying cause of corneal melting but the more common underlying causes should be ruled out by proper investigations. Pregnancy with its host of hormonal changes could potentially have some effect on corneal collagen leading to corneal melting in compromised corneas.

  17. Corneal surface reconstruction - a short review

    Directory of Open Access Journals (Sweden)

    Madhavan H N

    2009-01-01

    Full Text Available Cornea is the clear, dome-shaped surface that covers the front of the eye and when damage due to burns or injury and several other diseases, stem cells residing in its rim called "limbus" are stimulated to multiply to support growth of new epithelial cells over its surface. If this ready source of stem cells is damaged or destroyed the natural repair is not possible and such a condition is known as corneal limbal stem cell deficiency (CLSCD disease. Stem cell transplant helps such persons to regenerate the corneal surface. Human corneal limbal stem cell transplantation is at present an established procedure with reasonable good clinical outcome particularly when autologous limbal epithelial tissue from a fellow unaffected eye is used. 1, 2 A major concern related to the autograft is the possibility of CLSCD at the donor site, 3 techniques that allowed the expansion of a small limbal biopsy in the laboratory using cell cultures that could be then transplanted to the affected eye have been developed ,4, 5 Human amniotic membrane (HAM is used as a scaffold for both culturing the human limbal epithelial cells and for ocular surface reconstruction with the cultured limbal epithelial cells. 4-7 However, researchers have used alternative scaffolds like collagen 8, fibrin gel 9 and cross-linked gel of fibronectin and fibrin. 10 All these are biological materials and also need for animal 3T3 feeder layer for stem cell cultures. The properties of HAM are unique including antiadhesive effects, bacteriostatic effects, wound protection, pain reduction, and improvement of epithelialization and characteristically lacking imunogenicity. The use of amniotic membrane transplantation (AMT to treat ocular surface abnormalities was first reported by Graziella Pellegrini, chief of stem cell laboratory at Giovanni Paolo Hospital in Venice, Italy, who was the first to demonstrate the limbal stem cell transplant in 1997. Amniotic membrane has been successfully used in

  18. Characterization of Interstrand DNA-DNA Cross-Links Using the α-Hemolysin Protein Nanopore.

    Science.gov (United States)

    Zhang, Xinyue; Price, Nathan E; Fang, Xi; Yang, Zhiyu; Gu, Li-Qun; Gates, Kent S

    2015-12-22

    Nanopore-based sensors have been studied extensively as potential tools for DNA sequencing, characterization of epigenetic modifications such as 5-methylcytosine, and detection of microRNA biomarkers. In the studies described here, the α-hemolysin protein nanopore embedded in a lipid bilayer was used for the detection and characterization of interstrand cross-links in duplex DNA. Interstrand cross-links are important lesions in medicinal chemistry and toxicology because they prevent the strand separation that is required for read-out of genetic information from DNA in cells. In addition, interstrand cross-links are used for the stabilization of duplex DNA in structural biology and materials science. Cross-linked DNA fragments produced unmistakable current signatures in the nanopore experiment. Some cross-linked substrates gave irreversible current blocks of >10 min, while others produced long current blocks (10-100 s) before the double-stranded DNA cross-link translocated through the α-hemolysin channel in a voltage-driven manner. The duration of the current block for the different cross-linked substrates examined here may be dictated by the stability of the duplex region left in the vestibule of the nanopore following partial unzipping of the cross-linked DNA. Construction of calibration curves measuring the frequency of cross-link blocking events (1/τon) as a function of cross-link concentration enabled quantitative determination of the amounts of cross-linked DNA present in samples. The unique current signatures generated by cross-linked DNA in the α-HL nanopore may enable the detection and characterization of DNA cross-links that are important in toxicology, medicine, and materials science.

  19. Implantation of a Multifocal Toric Intraocular Lens after Radial Keratotomy and Cross-Linking with Hyperopia and Astigmatism Residues: A Case Report

    Directory of Open Access Journals (Sweden)

    Raffaele Nuzzi

    2017-08-01

    Full Text Available Radial keratotomy is a refractive surgical technique, widely used in the 80s and early 90s to correct myopia and astigmatism, but now overcome by more recent laser techniques. Important consequences, often in patients with more than 45 years of age, are progressive hyperopic shift and/or an increase in corneal astigmatism, whose main cause seems to be an increase in the curvature radius of the central portion of the cornea. This seems to be due to radial keratotomy incisions – with the consequent need for cross-linking – intraocular pressure, and corneal biomechanical parameters. The authors propose phacoemulsification with a customized multifocal toric intraocular lens implantation to correct the induced shift and hyperopic astigmatism. A decent postoperative visual acuity was observed with good patient satisfaction. A specific protocol must be applied to optimize the correct diagnosis, presurgical evaluation and postsurgical outcomes that are to be maintained over time, without regressions.

  20. Hydroxylysyl pyridinoline cross-link concentration affects the textural properties of fresh and smoked Atlantic salmon (Salmo salar L.) flesh.

    Science.gov (United States)

    Li, Xuejun; Bickerdike, Ralph; Lindsay, Emma; Campbell, Patrick; Nickell, David; Dingwall, Alastair; Johnston, Ian A

    2005-08-24

    A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g(-)(1) dry mass muscle in post-rigor muscle stored at 0 degrees C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P = 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.

  1. Cross-linked polyethylenimine–tripolyphosphate nanoparticles for gene delivery

    Directory of Open Access Journals (Sweden)

    Huang XZ

    2014-10-01

    Full Text Available Xianzhang Huang,1 Sujing Shen,2 Zhanfeng Zhang,1 Junhua Zhuang1 1Department of Laboratory Science, Second Affiliated Hospital of Guangzhou University of Chinese Medicine, 2Department of Laboratory Science, Guangdong Second Provincial Traditional Chinese Medicine Hospital, Guangzhou, People’s Republic of China Abstract: The high transfection efficiency of polyethylenimine (PEI makes it an attractive potential nonviral genetic vector for gene delivery and therapy. However, the highly positive charge of PEI leads to cytotoxicity and limits its application. To reduce the cytotoxicity of PEI, we prepared anion-enriched nanoparticles that combined PEI with tripolyphosphate (TPP. We then characterized the PEI-TPP nanoparticles in terms of size, zeta potential, and Fourier-transform infrared (FTIR spectra, and assessed their transfection efficiency, cytotoxicity, and ability to resist deoxyribonuclease (DNase I digestion. The cellular uptake of PEI-TPP with phosphorylated internal ribosome entry site–enhanced green fluorescent protein C1 or FAM (fluorouracil, Adriamycin [doxorubicin] and mitomycin-labeled small interfering ribonucleic acids (siRNAs was monitored by fluorescence microscopy and confocal laser microscopy. The efficiency of transfected delivery of plasmid deoxyribonucleic acid (DNA and siRNA in vitro was 1.11- to 4.20-fold higher with the PEI-TPP particles (7.6% cross-linked than with the PEI, at all N:P ratios (nitrogen in PEI to phosphorus in DNA tested. The cell viability of different cell lines was more than 90% at the chosen N:P ratios of PEI-TPP/DNA complexes. Moreover, PEI-TPP nanoparticles resisted digestion by DNase I for more than 2 hours. The time-dependent absorption experiment showed that 7.6% of cross-linked PEI-TPP particles were internalized by 293T cells within 1 hour. In summary, PEI-TPP nanoparticles effectively transfected cells while conferring little or no toxicity, and thus have potential application in gene

  2. Comparison of Riboflavin/Ultraviolet-A Cross-Linking in Porcine, Rabbit, and Human Sclera

    Directory of Open Access Journals (Sweden)

    Yali Zhang

    2014-01-01

    Full Text Available Purpose. To compare the biomechanical properties of porcine, rabbit, and human sclera before and after riboflavin/ultraviolet-A (UVA collagen cross-linking (CXL. Methods. Eight rabbits, 8 porcine eyeballs, and 8 human eyeballs were included. One rabbit eye and half of each bisected human and porcine eyeball were treated with riboflavin/UVA CXL. Untreated fellow rabbit eyes and eyeball halves served as controls. A 10 mm × 20 mm scleral band was harvested from each specimen. From this band, two 3.5 mm × 15.0 mm strips were prepared for biomechanical testing. The biomechanical parameters were ultimate stress, stress and Young’s modulus. Results. Values of stress, and Young’s modulus showed that human sclera was 4 times stiffer than porcine sclera and 3 times stiffer than rabbit sclera. In rabbit sclera, both the stress and Young’s modulus were significantly increased by CXL (P0.05. Conclusions. Human sclera has higher biomechanical stiffness than porcine and rabbit sclera. With the same irradiation dose, riboflavin/UVA CXL increases the biomechanical stiffness of rabbit sclera but not porcine or human sclera.

  3. Energy harvesting from vibration with cross-linked polypropylene piezoelectrets

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhang

    2015-07-01

    Full Text Available Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP, followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d33 coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d33 ⋅ g33 for a more typical d33 value of 400 pC/N is about 11.2 GPa−1. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm2 and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

  4. Cross-linking da cornea: protocolo padrão

    Directory of Open Access Journals (Sweden)

    Marcony R. Santhiago

    Full Text Available RESUMO O objetivo desta revisão é de determinar as indicações e eficácia da cirurgia que promove novas ligações covalentes entre as fibras de colágeno da córnea, conhecida como Cross-Linking (CXL, assim como esclarecer seus objetivos. O ceratocone é uma doença ectasica da córnea, bilateral, assimétrica, que, principalmente, cursa com encurvamento e afinamentos progressivo, e se inicia em geral na segunda década de vida. O uso primário do CXL tem sido na interrupção da progressão do Ceratocone. Apesar do conhecido encurvamento no estroma da córnea ocorrer nesses pacientes, a fisiopatologia por trás do ceratocone ainda é desconhecida e parece ser multifatorial. Pela evidencia literária disponível até o momento, o CXL da córnea esta, portanto indicado nos pacientes com doença em progressão. Concluímos que existe evidencia suficiente para afirmar que o CXL da córnea é eficaz na estabilização da doença ectásica da cornea.

  5. Cross-linking of polytetrafluoroethylene during room-temperature irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Pugmire, David L [Los Alamos National Laboratory; Wetteland, Chris J [Los Alamos National Laboratory; Duncan, Wanda S [Los Alamos National Laboratory; Lakis, Rollin E [Los Alamos National Laboratory; Schwartz, Daniel S [Los Alamos National Laboratory

    2008-01-01

    Exposure of polytetrafluoroethylene (PTFE) to {alpha}-radiation was investigated to detennine the physical and chemical effects, as well as to compare and contrast the damage mechanisms with other radiation types ({beta}, {gamma}, or thermal neutron). A number of techniques were used to investigate the chemical and physical changes in PTFE after exposure to {alpha}-radiation. These techniques include: Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and fluorescence spectroscopy. Similar to other radiation types at low doses, the primary damage mechanism for the exposure of PTFE to {alpha}-radiation appears to be chain scission. Increased doses result in a change-over of the damage mechanism to cross-linking. This result is not observed for any radiation type other than {alpha} when irradiation is performed at room temperature. Finally, at high doses, PTFE undergoes mass-loss (via smallfluorocarbon species evolution) and defluorination. The amount and type of damage versus sample depth was also investigated. Other types of radiation yield damage at depths on the order of mm to cm into PTFE due to low linear energy transfer (LET) and the correspondingly large penetration depths. By contrast, the {alpha}-radiation employed in this study was shown to only induce damage to a depth of approximately 26 {mu}m, except at very high doses.

  6. Synthesis and Properties of Cross-Linked Polyamide Aerogels

    Science.gov (United States)

    Williams, Jarrod C.; Meador, Mary Ann; McCorkle, Linda

    2015-01-01

    We report the first synthesis of cross-linked polyamide aerogels through step growth polymerization using a combination of diamines, diacid chloride and triacid chloride. Polyamide oligomers endcapped with amines are prepared as stable solutions in N-methylpyrrolidinone from several different diamine precursors and 1,3-benzenedicarbonyl dichloride. Addition of 1,3,5-benzenetricarbonyl trichloride yields gels which form in under five minutes according to the scheme shown. Solvent exchange of the gels into ethanol, followed by drying using supercritical CO2 extraction gives colorless aerogels with densities around 0.1 to 0.2 gcm3. Thicker monolithes of the polyamide aerogels are stiff and strong, while thin films of certain formulations are highly flexible, durable, and even translucent. These materials may have use as insulation for deployable space structures, rovers, habitats or extravehicular activity suits as well as in many terrestrial applications. Strucure property relationships of the aerogels, including surface area, mechanical properties, and thermal conductivity will be discussed.

  7. Energy harvesting from vibration with cross-linked polypropylene piezoelectrets

    Science.gov (United States)

    Zhang, Xiaoqing; Wu, Liming; Sessler, Gerhard M.

    2015-07-01

    Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP), followed by proper corona charging. Young's modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d33 coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d33 ṡ g33) for a more typical d33 value of 400 pC/N is about 11.2 GPa-1. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm2 and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

  8. Energy harvesting from vibration with cross-linked polypropylene piezoelectrets

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoqing [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Institute for Telecommunications Technology, Merckstrasse 25, 64283 Darmstadt (Germany); Wu, Liming [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Sessler, Gerhard M., E-mail: g.sessler@nt.tu-darmstadt.de [Institute for Telecommunications Technology, Merckstrasse 25, 64283 Darmstadt (Germany)

    2015-07-15

    Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP), followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d{sub 33} coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d{sub 33} ⋅ g{sub 33}) for a more typical d{sub 33} value of 400 pC/N is about 11.2 GPa{sup −1}. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm{sup 2} and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

  9. Analysis of protein-nucleic acid interactions by photochemical cross-linking and mass spectrometry

    DEFF Research Database (Denmark)

    Steen, Hanno; Jensen, Ole Nørregaard

    2002-01-01

    Photochemical cross-linking is a commonly used method for studying the molecular details of protein-nucleic acid interactions. Photochemical cross-linking aids in defining nucleic acid binding sites of proteins via subsequent identification of cross-linked protein domains and amino acid residues....... Mass spectrometry (MS) has emerged as a sensitive and efficient analytical technique for determination of such cross-linking sites in proteins. The present review of the field describes a number of MS-based approaches for the characterization of cross-linked protein-nucleic acid complexes...... and for sequencing of peptide-nucleic acid heteroconjugates. The combination of photochemical cross-linking and MS provides a fast screening method to gain insights into the overall structure and formation of protein-oligonucleotide complexes. Because the analytical methods are continuously refined and protein...

  10. Characterization of the deoxyguanosine-lysine cross-link of methylglyoxal.

    Science.gov (United States)

    Petrova, Katya V; Millsap, Amy D; Stec, Donald F; Rizzo, Carmelo J

    2014-06-16

    Methylglyoxal is a mutagenic bis-electrophile that is produced endogenously from carbohydrate precursors. Methylglyoxal has been reported to induce DNA-protein cross-links (DPCs) in vitro and in cultured cells. Previous work suggests that these cross-links are formed between guanine and either lysine or cysteine side chains. However, the chemical nature of the methylglyoxal induced DPC have not been determined. We have examined the reaction of methylglyoxal, deoxyguanosine (dGuo), and Nα-acetyllysine (AcLys) and determined the structure of the cross-link to be the N2-ethyl-1-carboxamide with the lysine side chain amino group (1). The cross-link was identified by mass spectrometry and the structure confirmed by comparison to a synthetic sample. Further, the cross-link between methylglyoxal, dGuo, and a peptide (AcAVAGKAGAR) was also characterized. The mechanism of cross-link formation is likely to involve an Amadori rearrangement.

  11. Fabrication of patterned calcium cross-linked alginate hydrogel films and coatings through reductive cation exchange.

    Science.gov (United States)

    Bruchet, Marion; Melman, Artem

    2015-10-20

    Calcium cross-linked alginate hydrogels are widely used in targeted drug delivery, tissue engineering, wound treatment, and other biomedical applications. We developed a method for preparing homogeneous alginate hydrogels cross-linked with Ca(2+) cations using reductive cation exchange in homogeneous iron(III) cross-linked alginate hydrogels. Treatment of iron(III) cross-linked alginate hydrogels with calcium salts and sodium ascorbate results in reduction of iron(III) cations to iron(II) that are instantaneously replaced with Ca(2+) cations, producing homogeneous ionically cross-linking hydrogels. Alternatively, the cation exchange can be performed by photochemical reduction in the presence of calcium chloride using a sacrificial photoreductant. This approach allows fabrication of patterned calcium alginate hydrogels through photochemical patterning of iron(III) cross-linked alginate hydrogel followed by the photochemical reductive exchange of iron cations to calcium.

  12. An Open Data Format for Visualization and Analysis of Cross-Linked Mass Spectrometry Results.

    Science.gov (United States)

    Hoopmann, Michael R; Mendoza, Luis; Deutsch, Eric W; Shteynberg, David; Moritz, Robert L

    2016-11-01

    Protein-protein interactions are an important element in the understanding of protein function, and chemical cross-linking shotgun mass spectrometry is rapidly becoming a routine approach to identify these specific interfaces and topographical interactions. Protein cross-link data analysis is aided by dozens of algorithm choices, but hindered by a lack of a common format for representing results. Consequently, interoperability between algorithms and pipelines utilizing chemical cross-linking remains a challenge. pepXML is an open, widely-used format for representing spectral search algorithm results that has facilitated information exchange and pipeline development for typical shotgun mass spectrometry analyses. We describe an extension of this format to incorporate cross-linking spectral search results. We demonstrate application of the extension by representing results of multiple cross-linking search algorithms. In addition, we demonstrate adapting existing pepXML-supporting software pipelines to analyze protein cross-linking results formatted in pepXML. Graphical Abstract ᅟ.

  13. Properties and modification of porous 3-D collagen/hydroxyapatite composites.

    Science.gov (United States)

    Sionkowska, A; Kozłowska, J

    2013-01-01

    A freeze drying technique was used to form porous three-dimensional collagen matrixes modified by the addition of a variable amount of nano-hydroxyapatite. For chemical cross-linking EDC/NHS were used. Physical cross-linking was achieved by dehydrothermal treatment. Mechanical properties, morphology, dissolution, porosity, density, enzymatic degradation and swelling properties of materials have been studied after cross-linking. The density of scaffolds and its compressive modulus increased with an increasing amount of hydroxyapatite and collagen concentration in the composite scaffold, while the swelling ratio and porosity decreased. The studied scaffolds dissolved slowly in PBS solution. DHT cross-linked collagen matrices showed a much faster degradation rate after exposure to collagenase than the EDC cross-linked samples.

  14. Tailoring the properties of cholecyst-derived extracellular matrix using carbodiimide cross-linking.

    LENUS (Irish Health Repository)

    Burugapalli, Krishna

    2009-01-01

    Modulation of properties of extracellular matrix (ECM) based scaffolds is key for their application in the clinical setting. In the present study, cross-linking was used as a tool for tailoring the properties of cholecyst-derived extracellular matrix (CEM). CEM was cross-linked with varying cross-linking concentrations of N,N-(3-dimethyl aminopropyl)-N\\'-ethyl carbodiimide (EDC) in the presence of N-hydroxysuccinimide (NHS). Shrink temperature measurements and ATR-FT-IR spectra were used to determine the degree of cross-linking. The effect of cross-linking on degradation was tested using the collagenase assay. Uniaxial tensile properties and the ability to support fibroblasts were also evaluated as a function of cross-linking. Shrink temperature increased from 59 degrees C for non-cross-linked CEM to 78 degrees C for the highest EDC cross-linking concentration, while IR peak area ratios for the free -NH(2) group at 3290 cm(-1) to that of the amide I band at 1635 cm(-1) decreased with increasing EDC cross-linking concentration. Collagenase assay demonstrated that degradation rates for CEM can be tailored. EDC concentrations 0 to 0.0033 mmol\\/mg CEM were the cross-linking concentration range in which CEM showed varied susceptibility to collagenase degradation. Furthermore, cross-linking concentrations up to 0.1 mmol EDC\\/mg CEM did not have statistically significant effect on the uniaxial tensile strength, as well as morphology, viability and proliferation of fibroblasts on CEM. In conclusion, the degradation rates of CEM can be tailored using EDC-cross-linking, while maintaining the mechanical properties and the ability of CEM to support cells.

  15. In vitro cross-linking of elastin peptides and molecular characterization of the resultant biomaterials.

    Science.gov (United States)

    Heinz, Andrea; Ruttkies, Christoph K H; Jahreis, Günther; Schräder, Christoph U; Wichapong, Kanin; Sippl, Wolfgang; Keeley, Fred W; Neubert, Reinhard H H; Schmelzer, Christian E H

    2013-04-01

    Elastin is a vital protein and the major component of elastic fibers which provides resilience to many vertebrate tissues. Elastin's structure and function are influenced by extensive cross-linking, however, the cross-linking pattern is still unknown. Small peptides containing reactive allysine residues based on sequences of cross-linking domains of human elastin were incubated in vitro to form cross-links characteristic of mature elastin. The resultant insoluble polymeric biomaterials were studied by scanning electron microscopy. Both, the supernatants of the samples and the insoluble polymers, after digestion with pancreatic elastase or trypsin, were furthermore comprehensively characterized on the molecular level using MALDI-TOF/TOF mass spectrometry. MS(2) data was used to develop the software PolyLinX, which is able to sequence not only linear and bifunctionally cross-linked peptides, but for the first time also tri- and tetrafunctionally cross-linked species. Thus, it was possible to identify intra- and intermolecular cross-links including allysine aldols, dehydrolysinonorleucines and dehydromerodesmosines. The formation of the tetrafunctional cross-link desmosine or isodesmosine was unexpected, however, could be confirmed by tandem mass spectrometry and molecular dynamics simulations. The study demonstrated that it is possible to produce biopolymers containing polyfunctional cross-links characteristic of mature elastin from small elastin peptides. MALDI-TOF/TOF mass spectrometry and the newly developed software PolyLinX proved suitable for sequencing of native cross-links in proteolytic digests of elastin-like biomaterials. The study provides important insight into the formation of native elastin cross-links and represents a considerable step towards the characterization of the complex cross-linking pattern of mature elastin. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Radiation cross-linking in ultra-high molecular weight polyethylene for orthopaedic applications

    OpenAIRE

    Oral, Ebru; Muratoglu, Orhun K.

    2007-01-01

    The motivation for radiation cross-linking of ultra-high molecular weight polyethylene (UHMWPE) is to increase its wear resistance to be used as bearing surfaces for total joint arthroplasty. However, radiation also leaves behind long-lived residual free radicals in this polymer, the reactions of which can detrimentally affect mechanical properties. In this review, we focus on the radiation cross-linking and oxidative stability of first and second generation highly cross-linked UHMWPEs develo...

  17. Retinal Pigment Epithelium Cell Alignment on Nanostructured Collagen Matrices

    OpenAIRE

    Ulbrich, Stefan; Friedrichs, Jens; Valtink, Monika; Murovski, Simo; Franz, Clemens M.; Müller, Daniel J.; Richard H. W. Funk; Engelmann, Katrin

    2014-01-01

    We investigated attachment and migration of human retinal pigment epithelial cells (primary, SV40-transfected and ARPE-19) on nanoscopically defined, two-dimensional matrices composed of parallel-aligned collagen type I fibrils. These matrices were used non-cross-linked (native) or after riboflavin/UV-A cross-linking to study cell attachment and migration by time-lapse video microscopy. Expression of collagen type I and IV, MMP-2 and of the collagen-binding integrin subunit α2 were examined b...

  18. Effect of Cross-Linking and Enzymatic Hydrolysis Composite Modification on the Properties of Rice Starches

    Directory of Open Access Journals (Sweden)

    Gao-Qiang Liu

    2012-07-01

    Full Text Available Native rice starch lacks the versatility necessary to function adequately under rigorous industrial processing, so modified starches are needed to meet the functional properties required in food products. This work investigated the impact of enzymatic hydrolysis and cross-linking composite modification on the properties of rice starches. Rice starch was cross-linked with epichlorohydrin (EPI with different concentrations (0.5%, 0.7%, 0.9% w/w, on a dry starch basis, affording cross-linked rice starches with the three different levels of cross-linking that were named R1, R2, and R3, respectively. The cross-linked rice starches were hydrolyzed by α-amylase and native, hydrolyzed, and hydrolyzed cross-linked rice starches were comparatively studied. It was found that hydrolyzed cross-linked rice starches showed a lower the degree of amylase hydrolysis compared with hydrolyzed rice starch. The higher the degree of cross-linking, the higher the capacity to resist enzyme hydrolysis. Hydrolyzed cross-linked rice starches further increased the adsorptive capacities of starches for liquids and decreased the trend of retrogradation, and it also strengthened the capacity to resist shear compared to native and hydrolyzed rice starches.

  19. Alkaline battery containing a separator of a cross-linked copolymer of vinyl alcohol and unsaturated carboxylic acid

    Science.gov (United States)

    Hsu, L. C.; Philipp, W. H.; Sheibley, D. W.; Gonzalez-Sanabria, O. D. (Inventor)

    1985-01-01

    A battery separator for an alkaline battery is described. The separator comprises a cross linked copolymer of vinyl alcohol units and unsaturated carboxylic acid units. The cross linked copolymer is insoluble in water, has excellent zincate diffusion and oxygen gas barrier properties and a low electrical resistivity. Cross linking with a polyaldehyde cross linking agent is preferred.

  20. Encapsulation of volatiles by homogenized partially-cross linked alginates.

    Science.gov (United States)

    Inguva, Pavan K; Ooi, Shing Ming; Desai, Parind M; Heng, Paul W S

    2015-12-30

    Cross-linked calcium alginate gels are too viscous to be efficaciously incorporated into spray dried formulations. Thus, viscosity reduction is essential to ensure the processability of calcium alginate gels to be sprayed. Viscosity reduction by high pressure homogenization can open new formulation possibilities. Presently, testing of microcapsule integrity is also limited because either single particle tests neglect collective particle behaviours in bulk or bulk testing methods are often associated with single compressions which may not fully characterize individual particle strengths. The aim of this study was sub-divided into three objectives. First objective was to evaluate the impact of high pressure homogenization on gel viscosity. Second objective was to explore the use of the homogenized gels with modified starch for microencapsulation by spray drying. The final objective was to develop a stamping system as microcapsule strength tester that can assess microcapsules in bulk and evaluate the impact of multiple compressions. Collectively, this study would lead towards developing a pressure-activated patch of microcapsules with encapsulated volatiles and the method to assess the patch efficacy. The alginate gels largely experienced an exponential decay in viscosity when homogenized. Furthermore, the homogenized gels were successfully incorporated in spray drying formulations for microencapsulation. The custom-designed microcapsule strength tester was successfully used and shown to possess the required sensitivity to discern batches of microcapsules containing volatiles to have different release profiles. Addition of homogenized gels strengthened the microcapsules only at high wall to core ratios with low mass-load alginate gels. High mass-load gels weaken the microcapsules, exhibiting a higher release at low stamping pressures and wrinkling on the microcapsules surface.

  1. Integrated Cryogenic Satellite Communications Cross-Link Receiver Experiment

    Science.gov (United States)

    Romanofsky, R. R.; Bhasin, K. B.; Downey, A. N.; Jackson, C. J.; Silver, A. H.; Javadi, H. H. S.

    1995-01-01

    An experiment has been devised which will validate, in space, a miniature, high-performance receiver. The receiver blends three complementary technologies; high temperature superconductivity (HTS), pseudomorphic high electron mobility transistor (PHEMT) monolithic microwave integrated circuits (MMIC), and a miniature pulse tube cryogenic cooler. Specifically, an HTS band pass filter, InP MMIC low noise amplifier, HTS-sapphire resonator stabilized local oscillator (LO), and a miniature pulse tube cooler will be integrated into a complete 20 GHz receiver downconverter. This cooled downconverter will be interfaced with customized signal processing electronics and integrated onto the space shuttle's 'HitchHiker' carrier. A pseudorandom data sequence will be transmitted to the receiver, which is in low Earth orbit (LEO), via the Advanced Communication Technology Satellite (ACTS) on a 20 GHz carrier. The modulation format is QPSK and the data rate is 2.048 Mbps. The bit error rate (BER) will be measured in situ. The receiver is also equipped with a radiometer mode so that experiment success is not totally contingent upon the BER measurement. In this mode, the receiver uses the Earth and deep space as a hot and cold calibration source, respectively. The experiment closely simulates an actual cross-link scenario. Since the receiver performance depends on channel conditions, its true characteristics would be masked in a terrestrial measurement by atmospheric absorption and background radiation. Furthermore, the receiver's performance depends on its physical temperature, which is a sensitive function of platform environment, thermal design, and cryocooler performance. This empirical data is important for building confidence in the technology.

  2. Transglutaminases: widespread cross-linking enzymes in plants.

    Science.gov (United States)

    Serafini-Fracassini, Donatella; Del Duca, Stefano

    2008-08-01

    Transglutaminases have been studied in plants since 1987 in investigations aimed at interpreting some of the molecular mechanisms by which polyamines affect growth and differentiation. Transglutaminases are a widely distributed enzyme family catalysing a myriad of biological reactions in animals. In plants, the post-translational modification of proteins by polyamines forming inter- or intra-molecular cross-links has been the main transglutaminase reaction studied. The few plant transglutaminases sequenced so far have little sequence homology with the best-known animal enzymes, except for the catalytic triad; however, they share a possible structural homology. Proofs of their catalytic activity are: (a) their ability to produce glutamyl-polyamine derivatives; (b) their recognition by animal transglutaminase antibodies; and (c) biochemical features such as calcium-dependency, etc. However, many of their fundamental biochemical and physiological properties still remain elusive. It has been detected in algae and in angiosperms in different organs and sub-cellular compartments, chloroplasts being the best-studied organelles. Possible roles concern the structural modification of specific protein substrates. In chloroplasts, transglutaminases appear to stabilize the photosynthetic complexes and Rubisco, being regulated by light and other factors, and possibly exerting a positive effect on photosynthesis and photo-protection. In the cytosol, they modify cytoskeletal proteins. Preliminary reports suggest an involvement in the cell wall construction/organization. Other roles appear to be related to fertilization, abiotic and biotic stresses, senescence and programmed cell death, including the hypersensitive reaction. The widespread occurrence of transglutaminases activity in all organs and cell compartments studied suggests a relevance for their still incompletely defined physiological roles. At present, it is not possible to classify this enzyme family in plants owing to

  3. Molecular mechanism of the inhibition effect of Lipoxin A4 on corneal dissolving pathology process

    Directory of Open Access Journals (Sweden)

    Hong-Yan Zhou

    2013-02-01

    Full Text Available AIM: Excessive dissolve of corneal tissue induced by MMPs which were activated by cytokins and chemokines will lead to corneal ulcer. The molecular mechanism of Lipoxin A4 (LXA4 on corneal collagen degradation in three dimensions was investigated.METHODS:Rabbit corneal fibroblasts were harvested and suspended in serum-free MEM. Type I collagen, DMEM, collagen reconstitution buffer and corneal fibroblast suspension were mixed on ice. The resultant mixture solidified in an incubator, after which test reagents and plasminogen was overlaid and the cultures were returned to the incubator. The supernatants from collagen gel incubations were collected and the amount of hydroxyproline in the hydrolysate was measured. Immunoblot analysis of MMP-1, -3 and TMMP-1,-2 was performed. MMP-2,-9 was detected by the method of Gelatin zymography. Cytotoxicity assay was measured.RESULTS:LXA4 inhibited corneal collagen degradation in a dose and time manner. LXA4 inhibited the IL-1β induced increases in the pro-MMP-1, -2, -3, -9 and active MMP-1, -2, -3, -9 in a concentration dependent manner. LXA4 could also inhibit the IL-1β induced increases in TIMP-1, -2.CONCLUSION: As a potent anti-inflammation reagent, LXA4 can inhibit corneal collagen degradation induced by IL-1β in corneal fibroblasts thus inhibiting corneal dissolving pathology process.

  4. Feruloylated arabinoxylans are oxidatively cross-linked by extracellular maize peroxidase but not by horseradish peroxidase.

    Science.gov (United States)

    Burr, Sally J; Fry, Stephen C

    2009-09-01

    Covalent cross-linking of soluble extracellular arabinoxylans in living maize cultures, which models the cross-linking of wall-bound arabinoxylans, is due to oxidation of feruloyl esters to oligoferuloyl esters and ethers. The oxidizing system responsible could be H2O2/peroxidase, O2/laccase, or reactive oxygen species acting non-enzymically. To distinguish these possibilities, we studied arabinoxylan cross-linking in vivo and in vitro. In living cultures, exogenous, soluble, extracellular, feruloylated [pentosyl-3H]arabinoxylans underwent cross-linking, beginning abruptly 8 d after sub-culture. Cross-linking was suppressed by iodide, an H2O2 scavenger, indicating dependence on endogenous H2O2. However, exogenous H2O2 did not cause precocious cross-linking, despite the constant presence of endogenous peroxidases, suggesting that younger cultures contained natural cross-linking inhibitors. Dialysed culture-filtrates cross-linked [3H]arabinoxylans in vitro only if H2O2 was also added, indicating a peroxidase requirement. This cross-linking was highly ionic-strength-dependent. The peroxidases responsible were heat-labile, although relatively heat-stable peroxidases (assayed on o-dianisidine) were also present. Surprisingly, added horseradish peroxidase, even after heat-denaturation, blocked the arabinoxylan-cross-linking action of maize peroxidases, suggesting that the horseradish protein was a competing substrate for [3H]arabinoxylan coupling. In conclusion, we show for the first time that cross-linking of extracellular arabinoxylan in living maize cultures is an action of apoplastic peroxidases, some of whose unusual properties we report.

  5. Analytical characterisation of glutardialdehyde cross-linking products in gelatine-gum arabic complex coacervates

    Energy Technology Data Exchange (ETDEWEB)

    Fuguet, Elisabet [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands)], E-mail: eli.fuguet@gmail.com; Platerink, Chris van [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands); Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht (Netherlands); Janssen, Hans-Gerd [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands); van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam (Netherlands)

    2007-11-26

    Encapsulates having shells of cross-linked mixtures of proteins and polysaccharides are widely used in the food and pharmaceutical industry for controlled release of actives and flavour compounds. In order to be able to predict the behaviour and the release characteristics of the microcapsules, a better understanding of the nature and extent of the cross-linking reaction is needed. Several analytical techniques were applied for the characterisation of glutardialdehyde (GDA) cross-linked encapsulates made of gelatine and gum arabic. To allow the use of sensitive, high-resolution methods such as chromatography and mass spectrometry, the sample first had to be hydrolysed. In this way, a mixture of amino acids, small peptides and the cross-link moieties was obtained. High-resolution liquid chromatography coupled to high-resolution mass spectrometry (HPLC-MS) was applied to detect possible cross-link markers through a comparison of HPLC-MS mass-chromatograms obtained for cross-linked and non-cross-linked coacervates. HPLC-MS/MS was used to identify the species responsible for the differences. Cross-linking occurred between GDA molecules and lysine and hydroxylysine {epsilon}-amino groups, and up to eight cross-link products of different nature could be identified. They included pyridinium ions and Schiff bases, and also unreacted GDA condensation products. Next, based on the insight gained in the possible chemical structures present in the cross-link markers, methods for selective labelling of these functionalities were employed to allow easier detection of related reaction products. Both liquid chromatography (LC) and gas chromatography (GC) were used in these experiments. Unfortunately, these approaches failed to detect new cross-link markers, most likely as a result of the low levels at which these are present.

  6. Feruloylated Arabinoxylans Are Oxidatively Cross-Linked by Extracellular Maize Peroxidase but Not by Horseradish Peroxidase

    Institute of Scientific and Technical Information of China (English)

    Sally J. Burr; Stephen C. Fry

    2009-01-01

    Covalent cross-linking of soluble extraceUular arabinoxylans in living maize cultures, which models the cross-linking of wall-bound arabinoxylans, is due to oxidation of feruloyl esters to oligoferuloyl esters and ethers. The oxidizing system responsible could be H_2O_2/peroxidase, O_2/laccase, or reactive oxygen species acting non-enzymically. To distinguish these possibilities, we studied arabinoxylan cross-linking in vivo and in vitro. In living cultures, exogenous, soluble, extra-cellular, feruloylated [pentosyl-~3H]arabinoxylans underwent cross-linking, beginning abruptly 8 d after sub-culture. Cross-linking was suppressed by iodide, an H_2O_2 scavenger, indicating dependence on endogenous H2O2. However, exogenous H_2O_2 did not cause precocious cross-linking, despite the constant presence of endogenous peroxidases, suggesting that younger cultures contained natural cross-linking inhibitors. Dialysed culture-filtrates cross-linked [~3H]arabinoxylans in vitro only if H_20_2 was also added, indicating a peroxiclase requirement. This cross-linking was highly ionic-strength-dependent. The peroxidases responsible were heat-labile, although relatively heat-stable peroxidases (assayed on o-dianisidine) were also present, Surprisingly, added horseradish peroxidase, even after heat-denaturation, blocked the arabinoxylan-cross-linking action of maize peroxidases, suggesting that the horseradish protein was a competing substrate for [~3H]arabino-xylan coupling. In conclusion, we show for the first time that cross-linking of extracellular arabinoxylan in living maize cultures is an action of apoplastic peroxidases, some of whose unusual properties we report.

  7. Corneal Transplantation

    DEFF Research Database (Denmark)

    Hjortdal, Jesper Østergaard

    Corneal transplantation has been performed for more than 100 years. Until 15 years ago the state-of-the art type of transplantation was penetrating keratoplasty, but since the start of this millennium, newly designed surgical techniques have developed considerably. Today, the vast majority of ker...

  8. Corneal Laceration

    Medline Plus

    Full Text Available ... Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye Health / Eye Health A-Z Corneal Laceration ... After Eyelid Scratch Jul 28, 2014 Leer en Español: ¿Qué Es una Laceración de la Córnea? Find ...

  9. Corneal topography

    DEFF Research Database (Denmark)

    Andersen, J.; Koch-Jensen, P.; Østerby, Ole

    1993-01-01

    The central corneal zone is depicted on keratoscope photographs using a small target aperture and a large object distance. Information on the peripheral area is included by employing a hemispherical target with a dense circular and radial pattern. On a 16 mm (R = 8 mm) reference steel sphere...

  10. Corneal chromoblastomycosis.

    Science.gov (United States)

    Barton, K; Miller, D; Pflugfelder, S C

    1997-03-01

    We sought to illustrate the difficulty in managing uncommon, pigmented mold-related corneal ulceration and to highlight the role of itraconazole in treating these patients. We describe the management and clinical course of a patient with a recurring corneal infection caused by Fonsecaea pedrosoi and discuss this experience in the light of existing literature on management of cutaneous chromoblastomycosis. A corneal ulcer caused by this organism healed initially on treatment with topical and systemic antifungal medication, but infection recurred in the deep stroma 4 months after cessation of therapy. After failure to respond to a further period of medical therapy, a small therapeutic penetrating keratoplasty was performed. Culture of a fibrinous membrane from the anterior iris surface demonstrated intraocular fungal infection, and postoperatively, an episode of marked fibrinous uveitis developed, suggesting the presence of viable intraocular fungal elements. A large penetrating keratoplasty was therefore performed with excision of involved iris in combination with extracapsular cataract extraction. F. pedrosoi was again cultured from the fibrinous membrane adherent to the iris and from the anterior lens capsule. Postoperatively the patient received a 5-month course of systemic itraconazole, and no further recurrences have been encountered after a further 2 months. F. pedrosoi is the organism most commonly isolated from the chronic cutaneous mycosis, chromoblastomycosis, and is relatively resistant to medical therapy. As has been reported for cutaneous disease, surgery in combination with systemic itraconazole may provide the best chance of cure in corneal chromoblastomycosis.

  11. Effect of curcumin caged silver nanoparticle on collagen stabilization for biomedical applications.

    Science.gov (United States)

    Srivatsan, Kunnavakkam Vinjimur; Duraipandy, N; Begum, Shajitha; Lakra, Rachita; Ramamurthy, Usha; Korrapati, Purna Sai; Kiran, Manikantan Syamala

    2015-04-01

    The current study aims at understanding the influence of curcumin caged silver nanoparticle (CCSNP) on stability of collagen. The results indicated that curcumin caged silver nanoparticles efficiently stabilize collagen, indicated by enhanced tensile strength, fibril formation and viscosity. The tensile strength of curcumin caged silver nanoparticle cross-linked collagen and elongation at break was also found to be higher than glutaraldehyde cross-linked collagen. The physicochemical characteristics of curcumin caged nanoparticle cross-linked collagen exhibited enhanced strength. The thermal properties were also good with both thermal degradation temperature and hydrothermal stability higher than native collagen. CD analysis showed no structural disparity in spite of superior physicochemical properties suggesting the significance of curcumin caged nanoparticle mediated cross-linking. The additional enhancement in the stabilization of collagen could be attributed to multiple sites for interaction with collagen molecule provided by curcumin caged silver nanoparticles. The results of cell proliferation and anti-microbial activity assays indicated that curcumin caged silver nanoparticles promoted cell proliferation and inhibited microbial growth making it an excellent biomaterial for wound dressing application. The study opens scope for nano-biotechnological strategies for the development of alternate non-toxic cross-linking agents facilitating multiple site interaction thereby improving therapeutic values to the collagen for biomedical application.

  12. Nile tilapia skin collagen sponge modified with chemical cross-linkers as a biomedical hemostatic material.

    Science.gov (United States)

    Sun, Leilei; Li, Bafang; Jiang, Dandan; Hou, Hu

    2017-07-26

    Nile tilapia skin collagen sponges were fabricated by freeze-drying technology and modified with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide (EDC/NHS), genipin+PBS, genipin+ethanol, tea polyphenol (TP), nordihydroguaiaretic acid (NDGA) and diphenyl phosphoryl azide (DPPA). Physicochemical and biological properties, micromorphology and compatibility before and after modification were investigated to evaluate collagen sponge as a hemostatic biomedical material. The mechanical property of collagen sponges strengthened after cross-linking. The elongation at break of cross-linked collagen sponges decreased except for EDC/NHS, which was close to that of non-crosslinked. The collagen sponge cross-linked with EDC/NHS exhibited the highest hygroscopicity in comparison with other cross-linkers. The resistance to collagenase biodegradation of collagen sponges after cross-linking strengthened significantly except for NDGA. Collagen sponges cross-linked with EDC/NHS, TP and NDGA maintained high porosity (97-98%), similar to non-crosslinked (98.42%). Collagen sponges could shorten the blood coagulation time. From the variations of the FTIR spectrum pattern and SEM, DPPA could change the secondary structure of collagen and destroy the spongy structure of collagen sponge, which was not suitable for the cross-linking of collagen sponge. Whereas, EDC/NHS was recognized as a perfect cross-linker owing to its excellent properties and porous microstructure. All fabricated collagen sponges were recognized to be biocompatible by the hemolysis assay in vitro. Therefore, collagen sponge modified with EDC/NHS could be used as a perfect biomedical hemostatic material. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. SYNTHESIS AND CATALYTIC PROPERTIES OF CROSS-LINKED HYDROPHOBICALLY ASSOCIATING POLY(ALKYLMETHYLDIALLYLAMMONIUM BROMIDES)

    NARCIS (Netherlands)

    WANG, GJ; ENGBERTS, JBFN

    1994-01-01

    Cross-linked, hydrophobically associating homo- and copolymers were synthesized by free-radical cyclo(co)polymerization of alkylmethyldiallylammonium bromide monomers with a small amount of N,N'-methylenebisacrylamide in aqueous solution using ammonium persulfate as the initiator. The cross-linked h

  14. Rheological properties of dispersions of enzymatically cross-linked apo-α-lactalbumin

    NARCIS (Netherlands)

    Saricay, Yunus; Wierenga, Peter A.; Vries, de Renko

    2016-01-01

    The enzymatic cross-linking of apo-α-lactalbumin (α-LA) with horseradish peroxidase (HRP) leads to the formation of hydrophilic protein aggregates with controlled size and architecture. We explore the rheological properties of dispersions of these HRP-cross-linked α-LA aggregates with a hydrodyna

  15. Covalently Cross-Linked Sulfone Polybenzimidazole Membranes with Poly(Vinylbenzyl Chloride) for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Aili, David; Li, Qingfeng;

    2013-01-01

    Covalently cross-linked polymer membranes were fabricated from poly(aryl sulfone benzimidazole) (SO(2) PBI) and poly(vinylbenzyl chloride) (PVBCl) as electrolytes for high-temperature proton-exchange-membrane fuel cells. The cross-linking imparted organo insolubility and chemical stability against...

  16. PREPARATION OF NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES UNDER MICROWAVE IRRADIATION

    Science.gov (United States)

    A facile method utilizing microwave irradiation is described that accomplishes the cross-linking reaction of PVA with metallic and bimetallic systems. Nanocomposites of PVA-cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-Pt, Pt-Fe, Cu...

  17. NOVEL METALLIC AND BIMETALLIC CROSS-LINKED POLY (VINYL ALCOHOL) NANOCOMPOSITES PREPARED UNDER MICROWAVE IRRADIATION

    Science.gov (United States)

    A facile microwave irradiation approach that results in a cross-linking reaction of poly (vinyl alcohol) (PVA) with metallic and bimetallic systems is described. Nanocomposites of PVA cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-P...

  18. Effects of Supercritical CO 2 Conditioning on Cross-Linked Polyimide Membranes

    KAUST Repository

    Kratochvil, Adam M.

    2010-05-25

    The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a structural reorganization of the polymer matrix that was observed in the non-cross-linkable, free acid polymer. Pure gas permeation isotherms and mixed gas permeabilities and selectivities show the cross-linked polymers to be much more stable to scCO2 conditioning than the free acid polymer. In fact, following scCO2 conditioning, the mixed gas CO2 permeabilities of the cross-linked polymers increased while the CO2/CH4 separation factors remained relatively unchanged. This response highlights the stability and high performance of these cross-linked membranes in aggressive environments. In addition, this response reveals the potential for the preconditioning of cross-linked polymer membranes to enhance productivity without sacrificing efficiency in practical applications which, in effect, provides another tool to \\'tune\\' membrane properties for a given separation. Finally, the dual mode model accurately describes the sorption and dilation characteristics of the cross-linked polymers. The changes in the dual mode sorption model parameters before and after the scCO2 exposure also provide insights into the alterations in the different glassy samples due to the cross-linking and scCO2 exposure. © 2010 American Chemical Society.

  19. Self-assembly made durable: water-repellent materials formed by cross-linking fullerene derivatives.

    Science.gov (United States)

    Wang, Jiaobing; Shen, Yanfei; Kessel, Stefanie; Fernandes, Paulo; Yoshida, Kaname; Yagai, Shiki; Kurth, Dirk G; Möhwald, Helmuth; Nakanishi, Takashi

    2009-01-01

    Fullerene flakes: A diacetylene-functionalized fullerene derivative self-organizes into flakelike microparticles (see picture). Both the diacetylene and C(60) moieties can be effectively cross-linked, which leads to supramolecular materials with remarkable resistivity to solvent, heat, and mechanical stress. Moreover, the surface of the cross-linked flakelike objects is highly durable and water-repellent.

  20. Peroxidase-mediated cross-linking of a tyrosine-containing peptide with ferulic acid

    NARCIS (Netherlands)

    Oudgenoeg, G.; Hilhorst, R.; Piersma, S.R.; Boeriu, C.G.; Gruppen, H.; Hessing, M.; Voragen, A.G.J.; Laane, C.

    2001-01-01

    The tyrosine-containing peptide Gly-Tyr-Gly (GYG) was oxidatively cross-linked by horseradish peroxidase in the presence of hydrogen peroxide. As products, covalently coupled di- to pentamers of the peptide were identified by LC-MS. Oxidative cross-linking of ferulic acid with horseradish peroxidase

  1. TISSUE INTERACTIONS WITH DERMAL SHEEP COLLAGEN IMPLANTS - A TRANSMISSION ELECTRON-MICROSCOPIC EVALUATION

    NARCIS (Netherlands)

    VANWACHEM, PB; VANLUYN, MJA; DAMINK, LO; FEIJEN, J; NIEUWENHUIS, P

    1991-01-01

    Tissue interactions with discs of dermal sheep collagen (DSC), subcutaneously implanted in rats, were evaluated using transmission electron microscopy. DSC cross-linked with hexamethylenediisocyanate (HDSC) had already been tested previously. In the present study, we compared tissue interactions of

  2. Investigation of anisotropic thermal transport in cross-linked polymers

    Science.gov (United States)

    Simavilla, David Nieto

    Thermal transport in lightly cross-linked polyisoprene and polybutadine subjected to uniaxial elongation is investigated experimentally. We employ two experimental techniques to assess the effect that deformation has on this class of materials. The first technique, which is based on Forced Rayleigh Scattering (FRS), allows us to measure the two independent components of the thermal diffusivity tensor as a function of deformation. These measurements along with independent measurements of the tensile stress and birefringence are used to evaluate the stress-thermal and stress-optic rules. The stress-thermal rule is found to be valid for the entire range of elongations applied. In contrast, the stress-optic rule fails for moderate to large stretch ratios. This suggests that the degree of anisotropy in thermal conductivity depends on both orientation and tension in polymer chain segments. The second technique, which is based on infrared thermography (IRT), allows us to measure anisotropy in thermal conductivity and strain induced changes in heat capacity. We validate this method measurements of anisotropic thermal conductivity by comparing them with those obtained using FRS. We find excellent agreement between the two techniques. Uncertainty in the infrared thermography method measurements is estimated to be about 2-5 %. The accuracy of the method and its potential application to non-transparent materials makes it a good alternative to extend current research on anisotropic thermal transport in polymeric materials. A second IRT application allows us to investigate the dependence of heat capacity on deformation. We find that heat capacity increases with stretch ratio in polyisoprene specimens under uniaxial extension. The deviation from the equilibrium value of heat capacity is consistent with an independent set of experiments comparing anisotropy in thermal diffusivity and conductivity employing FRS and IRT techniques. We identify finite extensibility and strain

  3. Assessment of protein function following cross-linking by alpha-dicarbonyls.

    Science.gov (United States)

    Miller, Antonia G; Gerrard, Juliet A

    2005-06-01

    Protein cross-linking via the Maillard reaction with alpha-dicarbonyl compounds has been the subject of intense scrutiny in the literature. We report here a study of the impact of this cross-linking on enzyme function. Protein function following glycation was examined by treating ribonuclease A with methylglyoxal, glyoxal, and diacetyl, which cross-linked the enzyme and impaired its activity. The effects of two reported Maillard reaction inhibitors, aminoguanidine and 3,5-dimethylpyrazole-1-carboxamidine, on the cross-linking reaction were assessed, with a parallel measurement of the effect on enzyme activity. The results demonstrate that preventing protein cross-linking does not necessarily preserve enzyme activity. These results cast doubt on the likely efficacy of some purported antiaging compounds in vivo.

  4. Characteristic of hyaluronic acid derivative films cross-linked by polyethylene glycol of low water content

    Institute of Scientific and Technical Information of China (English)

    Chen Jinghua; Chen Jingtao; Xu Zheng; Gu Qisheng

    2008-01-01

    Objective: To test the characteristics of byaluronic acid (HA) derivative cross-linked by polyethylene glycol films of low water content. Methods: The cross-linked HA film with 200 μm thickness was got at atmospheric pressure at 25℃ for 5 d. After dried, cross-linked films of 10 mm×10 mm were weighed and immersed in phosphate buffered saline (PBS pH 7.45) at 37℃ for 24 h. Then the solution fraction and water content were estimated. Meanwhile, cross-linked HA derivative films were immersed in phosphate buffered saline (PBS: pH 7.45) at 37℃ for determined time and then implanted subcutaneously in the back of white rats to test in vitro or in vivo degradation characteristic. Results and Conclusion: HA hydrogel cross-linked by polyethylene glycol with water content is as low as 60% and this kind of HA derivative has a slow degradation rate.

  5. Disuccinimidyl suberate cross-linked hemoglobin as a novel red blood cell substitute

    Institute of Scientific and Technical Information of China (English)

    LU; Xiuling; ZHENG; Chunyang; XU; Yuhong; SU; Zhiguo

    2005-01-01

    Disuccinimidyl suberate (DSS) intramolecularly cross-linked hemoglobin (Hb) was developed as a novel red blood cell substitute. A multi-angle laser light scattering detector coupled with size exclusion HPLC was applied to determine the molecular weight of the modified Hb. SDS-PAGE was also used as a complement. It was proved that 83.8% of the product was intramolecularly cross-linked Hb with weight-average molecular weights (Mw) of 67.5 kD, 12% was dimeric Hb with Mw of 146.6 kD, and 4.2% was trimeric Hb with Mw of 306.4 kD. The tetramer structure of the cross-linked Hb was stable as shown in size-exclusion chromatography using a mobile phase containing 1 mol/L MgCl2. Analysis by LC-MS demonstrated that the reaction of DSS with Hb mainly took place between the twoα subunits within a Hb molecule, resulting in stabilization of the tetramer structure. However, the cross-linking was not site-specific. The P50 of the cross-linked Hb decreased from 21.8 mmHg to 14.3 mmHg, and the Hill coefficient decreased from 2.22 to 1.41. Result of isoelectric focusing showed that the pI of DSS cross-linked Hb was in the range of 4.6-5.2, similar to that of serum albumin. The safety of DSS cross-linked Hb was favored by animal tests on rats and guinea pigs. Exchange transfusion experiment with DSS cross-linked Hb using rats as a model indicated no pressor effect or other significant side effects. The characteristics and properties of DSS cross-linked Hb were also compared with that of diaspirin cross-linked Hb reported in the literature.

  6. Collagen derived serum markers in carcinoma of the prostate

    DEFF Research Database (Denmark)

    Rudnicki, M; Jensen, L T; Iversen, P

    1995-01-01

    Three new collagen markers deriving from the collagenous matrix, e.g. carboxyterminal propeptide of type I procollagen (PICP), carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP), and aminoterminal propeptide of type III procollagen (PIIINP) were used for the diagnose......, ICTP, and PICP did not differ between these two groups. In patients with metastatic prostatic cancer all five markers were increased compared to the level measured in patients with localized cancer (p

  7. The natural history of corneal topographic progression of keratoconus after age 30 years in non-contact lens wearers.

    Science.gov (United States)

    Gokul, Akilesh; Patel, Dipika V; Watters, Grant A; McGhee, Charles N J

    2017-06-01

    To determine if significant progression of disease occurs in older, non-contact lens wearing, subjects with keratoconus and to identify potential predictive factors. Clinical and computerised corneal topography records of subjects with keratoconus attending a specialist optometry practice were retrospectively analysed to identify those aged ≥30 years, with ≥2 consultations ≥12 months apart, no contact lens wear and no corneal scarring, surgery or corneal hydrops. Topographic parameters assessed included: maximum keratometry (Kmax), steep keratometry (Ksteep), flat keratometry (Kflat), inferior-superior (I-S) ratio and the surface asymmetry and regularity (surface asymmetry index and surface regularity index) indices. Of the 449 subjects with keratoconus assessed, 43 eyes of 27 patients (6.01%) met inclusion criteria, with median age 38.45 (12.86) years at baseline and median follow-up 4.36 (8.68) years. There was a significant increase in Kmax (0.30 (1.21) D), Ksteep (0.27 (0.90) D), Kflat (0.34 (1.12) D) and I-S (0.26 (0.82) D) between baseline and final review, pkeratoconus may continue to progress beyond age 30. Older subjects with keratoconus should be monitored for progression, particularly with respect to possible corneal collagen cross-linking or astigmatic correction in cataract surgery. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  8. Age-related changes in collagen properties and mineralization in cancellous and cortical bone in the porcine mandibular condyle.

    Science.gov (United States)

    Willems, Nop M B K; Langenbach, Geerling E J; Everts, Vincent; Mulder, Lars; Grünheid, Thorsten; Bank, Ruud A; Zentner, Andrej; van Eijden, Theo M G J

    2010-04-01

    Collagen is an important constituent of bone, and it has been suggested that changes in collagen and mineral properties of bone are interrelated during growth. The aim of this study was to quantify age-related changes in collagen properties and the degree of mineralization of bone (DMB). The DMB in cancellous and cortical bone samples from the mandibular condyle of 35 female pigs aged 0-100 weeks was determined using micro-computed tomography. Subsequently, the amount of collagen and the number of pentosidine (Pen), hydroxylysylpyridinoline (HP), and lysylpyridinoline (LP) cross-links were quantified by means of high-performance liquid chromatography. The amount of collagen increased with age in cancellous bone but remained unchanged in cortical bone. The number of Pen and LP cross-links decreased in both bone types. In contrast, the number of HP cross-links decreased only in cancellous bone. The sum of the number of HP and LP cross-links decreased with age in cancellous bone only. The DMB increased in cancellous and cortical bone. It was concluded that the largest changes in the number of mature collagen cross-links and the mineralization in porcine cancellous and cortical bone take place before the age of 40 weeks. The low number of mature cross-links after this age suggests that the bone turnover rate continues to be high and thereby prevents the development of mature cross-links.

  9. Chemistry and physical properties of melt-processed and solution-cross-linked corn zein.

    Science.gov (United States)

    Sessa, David J; Mohamed, Abdellatif; Byars, Jeffrey A

    2008-08-27

    Corn zein was cross-linked with glutaraldehyde (GDA) using glacial acetic acid (HAc) as catalyst. The objectives are to evaluate the swelling characteristics of GDA cross-linked zein gels in water, ethanol, and their combinations. Similar formulations, upon solvent evaporation, form films. The mechanical properties of the films are compared to compression molded tensile bars from GDA melt-processed zein as a second objective. Chemistry of the cross-linking reaction was based on the aldehyde binding characteristics defined by use of fluorescence spectroscopy; sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to demonstrate the cross-linking reaction; FTIR to observe absorption differences of the cross-linked product; differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis to assess thermal properties; and the use of Instron Universal Testing Machine to evaluate mechanical properties. A reaction mechanism for acid catalyzed GDA cross-linking of zein is proposed. Thermal and mechanical properties of tensile bars cut from either film or formed by compression molding were similar, where both showed increased tensile strengths, ductility and stiffness when compared with unmodified controls. Samples that were reacted with 8% GDA by weight based on weight of zein from either process retained their integrity when tensile bars from each were subjected to boiling water for 10 min or soaking in either water or HAc for 24 h. The melt-processed, cross-linked zein is a more environmentally friendly method that would eliminate the need for HAc recovery.

  10. Modified gum arabic cross-linked gelatin scaffold for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sarika, P.R. [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala 695 547 (India); Cinthya, Kuriakose [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram, Kerala 695 012 (India); Jayakrishnan, A. [Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600 036 (India); Anilkumar, P.R., E-mail: anilkumarpr@sctimst.ac.in [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram, Kerala 695 012 (India); James, Nirmala Rachel, E-mail: nirmala@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala 695 547 (India)

    2014-10-01

    The present work deals with development of modified gum arabic cross-linked gelatin scaffold for cell culture. A new biocompatible scaffold was developed by cross-linking gelatin (Gel) with gum arabic, a polysaccharide. Gum arabic was subjected to periodate oxidation to obtain gum arabic aldehyde (GAA). GAA was reacted with gelatin under appropriate pH to prepare the cross-linked hydrogel. Cross-linking occurred due to Schiff's base reaction between aldehyde groups of oxidized gum arabic and amino groups of gelatin. The scaffold prepared from the hydrogel was characterized by swelling properties, degree of cross-linking, in vitro degradation and scanning electron microscopy (SEM). Cytocompatibility evaluation using L-929 and HepG2 cells confirmed non-cytotoxic and non-adherent nature of the scaffold. These properties are essential for generating multicellular spheroids and hence the scaffold is proposed to be a suitable candidate for spheroid cell culture. - Highlights: • Gum arabic cross-linked gelatin scaffold was developed for tissue engineering. • Cross-linking was achieved by Schiff's base reaction. • The scaffold is non-cytotoxic and non adherent to fibroblast and hepatocytes. • The scaffolds are potential candidates for spheroid cell culture.

  11. Understanding chemical reactivity for homo- and heterobifunctional protein cross-linking agents.

    Science.gov (United States)

    Chen, Fan; Nielsen, Simone; Zenobi, Renato

    2013-07-01

    Chemical cross-linking, combined with mass spectrometry, has been applied to map three-dimensional protein structures and protein-protein interactions. Proper choice of the cross-linking agent, including its reactive groups and spacer arm length, is of great importance. However, studies to understand the details of reactivity of the chemical cross-linkers with proteins are quite sparse. In this study, we investigated chemical cross-linking from the aspects of the protein structures and the cross-linking reagents involved, by using two structurally well-known proteins, glyceraldehyde 3-phosohate dehydrogenase and ribonuclease S. Chemical cross-linking reactivity was compared using a series of homo- and hetero-bifunctional cross-linkers, including bis(sulfosuccinimidyl) suberate, dissuccinimidyl suberate, bis(succinimidyl) penta (ethylene glycol), bis(succinimidyl) nona (ethylene glycol), m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester, 2-pyridyldithiol-tetraoxaoctatriacontane-N-hydrosuccinimide and succinimidyl-[(N-maleimidopropionamido)-tetracosaethyleneglycol]ester. The protein structure itself, especially the distances between target amino acid residues, was found to be a determining factor for the cross-linking efficiency. Moreover, the reactive groups of the chemical cross-linker also play an important role; a higher cross-linking reaction efficiency was found for maleimides compared to 2-pyrimidyldithiols. The reaction between maleimides and sulfhydryl groups is more favorable than that between N-hydroxysuccinimide esters and amine groups, although cysteine residues are less abundant in proteins compared to lysine residues. Copyright © 2013 John Wiley & Sons, Ltd.

  12. Shell and core cross-linked poly(L-lysine)/poly(acrylic acid) complex micelles.

    Science.gov (United States)

    Hsieh, Yi-Hsuan; Hsiao, Yung-Tse; Jan, Jeng-Shiung

    2014-12-21

    We report the versatility of polyion complex (PIC) micelles for the preparation of shell and core cross-linked (SCL and CCL) micelles with their surface properties determined by the constituent polymer composition and cross-linking agent. The negatively and positively charged PIC micelles with their molecular structure and properties depending on the mixing weight percentage and polymer molecular weight were first prepared by mixing the negatively and positively charged polyions, poly(acrylic acid) (PAA) and poly(L-lysine) (PLL). The feasibility of preparing SCL micelles was demonstrated by cross-linking the shell of the negatively and positively charged micelles using cystamine and genipin, respectively. The core of the micelles can be cross-linked by silica deposition to stabilize the assemblies. The shell and/or core cross-linked micelles exhibited excellent colloid stability upon changing solution pH. The drug release from the drug-loaded SCL micelles revealed that the controllable permeability of the SCL micelles can be achieved by tuning the cross-linking degree and the SCL micelles exhibited noticeable pH-responsive behavior with accelerated release under acidic conditions. With the versatility of cross-linking strategies, it is possible to prepare a variety of SCL and CCL micelles from PIC micelles.

  13. Novel antimicrobial superporous cross-linked chitosan/pyromellitimide benzoyl thiourea hydrogels.

    Science.gov (United States)

    Mohamed, Nadia A; Abd El-Ghany, Nahed A; Fahmy, Mona M

    2016-01-01

    In this work, chitosan (CS) was cross-linked with different amounts of pyromellitimide benzoyl thiourea moieties. The structure of the cross-linked CS was confirmed by elemental analyses, FTIR and (1)H- NMR spectroscopy. The cross-linking process proceeds via reacting of the amino groups of CS with the isothiocyanate groups of the N,N'-bis [4-(isothiocyanate carbonyl)phenyl] pyromellitimide cross-linker. The amount of the cross-linker was varied with respect to CS to produce four new pyromellitimide benzoyl thiourea cross-linked CS (PIBTU-CS) hydrogels designated as PIBTU-CS-1, PIBTU-CS-2, PIBTU-CS-3, and PIBTU-CS-4 of increasing cross-linking degree percent of 11, 22, 44 and 88%, respectively. The scanning electron microscopy observation indicates the extremely porous structure of the hydrogels. XRD results showed that the crystallinity of CS was decreased upon cross-linking. The four hydrogels exhibit a higher antibacterial activity on Bacillus subtilis and Streptococcus pneumoniae as Gram positive bacteria and against Escherichia coli as Gram negative bacteria and higher antifungal activity on Aspergillus fumigatus, Syncephalastrum racemosum and Geotricum candidum than that of the parent CS as shown from their higher inhibition zone diameters and their lower MIC values. The swell ability of the hydrogel as well as their antimicrobial activity increased with increasing cross-linking density.

  14. Jellyfish collagen scaffolds for cartilage tissue engineering.

    Science.gov (United States)

    Hoyer, Birgit; Bernhardt, Anne; Lode, Anja; Heinemann, Sascha; Sewing, Judith; Klinger, Matthias; Notbohm, Holger; Gelinsky, Michael

    2014-02-01

    Porous scaffolds were engineered from refibrillized collagen of the jellyfish Rhopilema esculentum for potential application in cartilage regeneration. The influence of collagen concentration, salinity and temperature on fibril formation was evaluated by turbidity measurements and quantification of fibrillized collagen. The formation of collagen fibrils with a typical banding pattern was confirmed by atomic force microscopy and transmission electron microscopy analysis. Porous scaffolds from jellyfish collagen, refibrillized under optimized conditions, were fabricated by freeze-drying and subsequent chemical cross-linking. Scaffolds possessed an open porosity of 98.2%. The samples were stable under cyclic compression and displayed an elastic behavior. Cytotoxicity tests with human mesenchymal stem cells (hMSCs) did not reveal any cytotoxic effects of the material. Chondrogenic markers SOX9, collagen II and aggrecan were upregulated in direct cultures of hMSCs upon chondrogenic stimulation. The formation of typical extracellular matrix components was further confirmed by quantification of sulfated glycosaminoglycans.

  15. Feline corneal disease.

    Science.gov (United States)

    Moore, Phillip Anthony

    2005-05-01

    The cornea is naturally transparent. Anything that interferes with the cornea's stromal architecture, contributes to blood vessel migration, increases corneal pigmentation, or predisposes to corneal edema, disrupts the corneas transparency and indicates corneal disease. The color, location, and shape and pattern of a corneal lesion can help in determining the underlying cause for the disease. Corneal disease is typically divided into congenital or acquired disorders. Congenital disorders, such as corneal dermoids are rare in cats, whereas acquired corneal disease associated with nonulcerative or ulcerative keratitis is common. Primary ocular disease, such as tear film instability, adenexal disease (medial canthal entropion, lagophthalmus, eyelid agenesis), and herpes keratitis are associated with the majority of acquired corneal disease in cats. Proliferative/eosinophilic keratitis, acute bullous keratopathy, and Florida keratopathy are common feline nonulcerative disorders. Nonprogressive ulcerative disease in cats, such as chronic corneal epithelial defects and corneal sequestration are more common than progressive corneal ulcerations.

  16. Grafted, cross-linked carbon black as a double-layer capacitor electrode material