Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements.

Science.gov (United States)

Aslanides, Ioannis M; Dessi, Claudia; Georgoudis, Panagiotis; Charalambidis, Georgios; Vlassopoulos, Dimitris; Coutsolelos, Athanassios G; Kymionis, George; Mukherjee, Achyut; Kitsopoulos, Theofanis N

2016-04-01

The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.

Herpetic keratitis after corneal collagen cross-linking with riboflavin and ultraviolet-A for progressive keratoconus.

Science.gov (United States)

Yuksel, Nilay; Bilgihan, Kamil; Hondur, Ahmet M

2011-12-01

To describe a case of herpetic keratitis after corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A for progressive keratoconus. A 31-year-old woman with rapidly progressive keratoconus in the left eye was treated with CXL. Four days postoperatively, a dendritic ulcer developed in the treated eye. The diagnosis was confirmed with polymerase chain reaction analysis of the corneal swab for herpes simplex. The patient had no prior history of herpetic eye disease or cold sores. The keratitis resolved in 10 days with treatment. At 1 month, the visual acuity was stable, but a mild superficial opacity was noted. Herpetic keratitis can be induced by CXL even in patients with no history of previous herpetic eye disease. Early diagnosis and proper treatment can facilitate successful management of this rare but important complication.

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

Directory of Open Access Journals (Sweden)

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.

The effect of riboflavin/UVA collagen cross-linking therapy on the structure and hydrodynamic behaviour of the ungulate and rabbit corneal stroma.

Directory of Open Access Journals (Sweden)

Sally Hayes

Full Text Available To examine the effect of riboflavin/UVA corneal crosslinking on stromal ultrastructure and hydrodynamic behaviour.One hundred and seventeen enucleated ungulate eyes (112 pig and 5 sheep and 3 pairs of rabbit eyes, with corneal epithelium removed, were divided into four treatment groups: Group 1 (28 pig, 2 sheep and 3 rabbits were untreated; Group 2 (24 pig were exposed to UVA light (3.04 mW/cm(2 for 30 minutes and Group 3 (29 pig and Group 4 (31 pig, 3 sheep and 3 rabbits had riboflavin eye drops applied to the corneal surface every 5 minutes for 35 minutes. Five minutes after the initial riboflavin instillation, the corneas in Group 4 experienced a 30 minute exposure to UVA light (3.04 mW/cm(2. X-ray scattering was used to obtain measurements of collagen interfibrillar spacing, spatial order, fibril diameter, D-periodicity and intermolecular spacing throughout the whole tissue thickness and as a function of tissue depth in the treated and untreated corneas. The effect of each treatment on the hydrodynamic behaviour of the cornea (its ability to swell in saline solution and its resistance to enzymatic digestion were assessed using in vitro laboratory techniques.Corneal thickness decreased significantly following riboflavin application (p<0.01 and also to a lesser extent after UVA exposure (p<0.05. With the exception of the spatial order factor, which was higher in Group 4 than Group 1 (p<0.01, all other measured collagen parameters were unaltered by cross-linking, even within the most anterior 300 microns of the cornea. The cross-linking treatment had no effect on the hydrodynamic behaviour of the cornea but did cause a significant increase in its resistance to enzymatic digestion.It seems likely that cross-links formed during riboflavin/UVA therapy occur predominantly at the collagen fibril surface and in the protein network surrounding the collagen.

Corneal Absorption of a New Riboflavin-Nanostructured System for Transepithelial Collagen Cross-Linking

Science.gov (United States)

Bottos, Katia M.; Oliveira, Anselmo G.; Bersanetti, Patrícia A.; Nogueira, Regina F.; Lima-Filho, Acácio A. S.; Cardillo, José A.; Schor, Paulo; Chamon, Wallace

2013-01-01

Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion. PMID:23785497

Current status of accelerated corneal cross-linking

Directory of Open Access Journals (Sweden)

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.

Treatment Results of Corneal Collagen Cross-Linking Combined with Riboflavin and 440 Nm Blue Light for Bacterial Corneal Ulcer in Rabbits.

Science.gov (United States)

Wei, Shufang; Zhang, Cuiying; Zhang, Shaoru; Xu, Yanyun; Mu, Guoying

2017-10-01

To study the treatment effect of corneal collagen cross-linking (CXL) combined with 440 nm blue light and riboflavin on bacterial corneal ulcer using animal experiments. A total of 21 New Zealand white rabbits that developed Staphylococcus aureus corneal ulcer were randomly divided into three groups. Seven rabbits were used as blank control groups; seven rabbits were treated with CXL combined with riboflavin and 440 nm blue light; and seven rabbits were treated with CXL combined with riboflavin and 370 nm ultraviolet A light. Necrotic tissues or secretions from the ulcer surface, eye secretions, conjunctival hyperemia, hypopyon, corneal infiltration, and pathological changes of the cornea were all observed. The 1st, 3th, and 7th day after CXL treatment, a statistically significant difference was found among the inflammation scores of the three groups. The scores of 440 and 370 groups decreased gradually, significantly lower than that of the control group. Bacterial cultures of 440 and 370 groups turned to be negative while that of the control group remained positive. After 1 day of CXL treatment, pathology pictures of the three groups all showed loss of corneal epithelia with many inflammatory cells in deep stroma. After 7 days of CXL treatment, abscess formed in almost all corneal area in the control group, while in 440 and 370 groups, multilayer healing of corneal epithelia, neovascularization, and many inflammatory cells within ulcers and proliferation of a small amount of fibroblast were seen. CXL combined with riboflavin and 440 nm blue light is effective in treating S. aureus corneal ulcer.

Conventional Corneal Collagen Cross-Linking Versus Transepithelial Diluted Alcohol and Iontophoresis-Assisted Corneal Cross-Linking in Progressive Keratoconus.

Science.gov (United States)

Bilgihan, Kamil; Yesilirmak, Nilufer; Altay, Yesim; Yuvarlak, Armagan; Ozdemir, Huseyin Baran

2017-12-01

To compare clinical outcomes of conventional corneal cross-linking (C-CXL) and diluted alcohol and iontophoresis-assisted corneal cross-linking (DAI-CXL) for the treatment of progressive keratoconus (KC). Ninety-three eyes of 80 patients with KC were treated by C-CXL (n = 47) or DAI-CXL (n = 46). Visual acuity, keratometry, KC indexes, pachymetry, and aberrations were recorded before treatment and 1, 3, 6, and 12 months after treatment. The demarcation line was assessed 1 month after treatment. A significant improvement in visual acuity was observed at month 3 and month 6 after DAI-CXL and C-CXL, respectively. A significant decrease in maximum keratometry was observed in both groups at month 6. The front symmetry index significantly improved in both groups after 6 months, whereas the Baiocchi Calossi Versaci index significantly improved only after DAI-CXL at month 12 (P = 0.01). Average keratometry and other KC indexes were stable during 12 months of follow-up. Central corneal thickness decreased by 28.6 and 40.2 μm after DAI-CXL and C-CXL at month 1, respectively (P < 0.01), and it reached baseline at the 12th month (P = 0.14) only in the DAI-CXL group. Higher-order aberrations, coma, and spherical aberration significantly worsened at month 1 (P < 0.01) only after C-CXL; however, they improved significantly at month 12 compared with baseline (P < 0.05) in both groups. The demarcation line was visible in all cases at month 1 at a mean depth of 302 ± 56 μm and 311 ± 57 μm after DAI-CXL and C-CXL, respectively (P = 0.7). The DAI-CXL protocol seems as effective as the C-CXL protocol in halting KC progression after 1 year of follow-up.

Persistent Epithelial Defects and Corneal Opacity After Collagen Cross-Linking With Substitution of Dextran (T-500) With Dextran Sulfate in Compounded Topical Riboflavin.

Science.gov (United States)

Höllhumer, Roland; Watson, Stephanie; Beckingsale, Peter

2017-03-01

Collagen cross-linking (CXL) is a commonly performed procedure to prevent the progression of keratoconus. Riboflavin is an essential part of the procedure, which facilitates both the cross-linking process and protection of intraocular structures. Dextran can be added to riboflavin to create an isotonic solution. This case report highlights the importance of compounding riboflavin with the correct dextran solution. A retrospective case series. Six eyes of 4 male patients with keratoconus aged from 20 to 38 years underwent CXL with substitution of 20% dextran (T-500) with 20% dextran sulfate in a compounded riboflavin 0.1% solution. Postoperatively, persistent corneal epithelial defects, stromal haze, and then scarring occurred. Corneal transplantation was performed for visual rehabilitation but was complicated by graft rejection followed by failure (n = 1 eye), dehiscence (n = 4), cataract (n = 2), post-laser ablation haze (n = 1), and steroid-induced glaucoma (n = 2). The visual outcome was dextran (T-500) with dextran sulfate in riboflavin solutions during CXL results in loss of vision from permanent corneal opacity. Residual host changes may compromise the results of corneal transplantation.

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

Directory of Open Access Journals (Sweden)

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.

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

Directory of Open Access Journals (Sweden)

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.

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

Directory of Open Access Journals (Sweden)

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.

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

Directory of Open Access Journals (Sweden)

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.

Collagen Cross-Linking: Current Status and Future Directions

Directory of Open Access Journals (Sweden)

Marine Hovakimyan

2012-01-01

Full Text Available Collagen cross-linking (CXL using UVA light and riboflavin (vitamin B2 was introduced as a clinical application to stabilize the cornea by inducing cross-links within and between collagen fibers. CXL has been investigated extensively and has been shown clinically to arrest the progression of keratoconic or post-LASIK ectasia. With its minimal cost, simplicity, and proven positive clinical outcome, CXL can be regarded as a useful approach to reduce the number of penetrating keratoplasties performed. Small case series have also indicated that CXL is beneficial in corneal edema by reducing stromal swelling behavior and in keratitis by inhibiting pathogen growth. Despite these encouraging results, CXL remains a relatively new method that is potentially associated with complications. Aspects such as side effects and recurrence rates have still to be elucidated. In light of the growing interest in CXL, our paper summarizes present knowledge about this promising approach. We have intentionally endeavored to include the more relevant studies from the recent literature to provide an overview of the current status of CXL.

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

Microbiologic, Pharmacokinetic, and Clinical Effects of Corneal Collagen Cross-Linking on Experimentally Induced Pseudomonas Keratitis in Rabbits.

Science.gov (United States)

Cosar, C Banu; Kucuk, Mutlu; Celik, Ekrem; Gonen, Tansu; Akyar, Isin; Serteser, Mustafa; Tokat, Fatma; Ince, Umit

2015-10-01

To determine the effects of corneal collagen cross-linking (CXL) on the penetration of topical 0.5% moxifloxacin, on the number of colony-forming units (CFUs) in the cornea, and on the clinical course in a rabbit eye model of experimentally induced Pseudomonas aeruginosa keratitis. In this prospective animal study, experimental Pseudomonas corneal ulcers were induced in 56 corneas of 28 albino New Zealand rabbits. The corneas were randomly divided into the following 4 groups: the control group (14 eyes), the MOX group (moxifloxacin) (14 eyes), the MOX + CXL group (14 eyes), and the CXL group (14 eyes). On day 4 of the experiment, the eyes in the control group were enucleated and CFU counting was performed. On day 10 of the experiment, all eyes were enucleated and CFU counting was performed. In the MOX and MOX + CXL groups, the moxifloxacin level in the cornea, aqueous humor, iris, plasma, and serum was measured by reverse-phase high-performance liquid chromatography. The difference in the corneal CFU count between the MOX group and the MOX + CXL group was not significant (P = 0.317). Clinical improvement was greatest in the MOX + CXL group (P < 0.001). The mean corneal moxifloxacin level was 0.391 ± 0.09 μg·mg in the MOX group versus 0.291 ± 0.09 μg·mg in the MOX + CXL group; as such, CXL did not have a significant effect on antibiotic penetrance (P = 0.386). Clinical improvement was greatest in the MOX + CXL group. The synergistic effect of CXL on corneal ulcer treatment is not through antibiotic penetrance.

Comparison of Changes in Central Corneal Thickness During Corneal Collagen Cross-Linking, Using Isotonic Riboflavin Solutions With and Without Dextran, in the Treatment of Progressive Keratoconus.

Science.gov (United States)

Zaheer, Naima; Khan, Wajid Ali; Khan, Shama; Khan, M Abdul Moqeet

2018-03-01

To compare intraoperative changes in central corneal thickness (CCT) during corneal cross-linking, using 2 different isotonic riboflavin solutions either with dextran or with hydroxy propyl methylcellulose, in the treatment of progressive keratoconus. In this retrospective study, we analyzed records of corneal thickness measurements, taken during various steps of cross-linking. Cross-linking was performed using either isotonic riboflavin with dextran (group A) or isotonic riboflavin with hydroxy propyl methylcellulose (without dextran) (group B). CCT measurements were recorded before and after epithelial removal, after saturation with respective isotonic riboflavin solution, after use of hypotonic riboflavin in selected cases, and after ultraviolet A (UV-A) application. A mixed-way analysis of variance was conducted on CCT readings within each group and between both groups, and p dextran causes a significant decrease in corneal thickness, whereas dextran-free isotonic riboflavin causes a significant increase in corneal thickness, thus facilitating the procedure.

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

Radiation cross-linked collagen/dextran dermal scaffolds: effects of dextran on cross-linking and degradation.

Science.gov (United States)

Zhang, Yaqing; Zhang, Xiangmei; Xu, Ling; Wei, Shicheng; Zhai, Maolin

2015-01-01

Ionizing radiation effectively cross-links collagen into network with enhanced anti-degradability and biocompatibility, while radiation-cross-linked collagen scaffold lacks flexibility, satisfactory surface appearance, and performs poor in cell penetration and ingrowth. To make the radiation-cross-linked collagen scaffold to serve as an ideal artificial dermis, dextran was incorporated into collagen. Scaffolds with the collagen/dextran (Col/Dex) ratios of 10/0, 7/3, and 5/5 were fabricated via (60)Co γ-irradiation cross-linking, followed by lyophilization. The morphology, microstructure, physicochemical, and biological properties were investigated. Compared with pure collagen, scaffolds with dextran demonstrated more porous appearance, enhanced hydrophilicity while the cross-linking density was lower with the consequence of larger pore size, higher water uptake, as well as reduced stiffness. Accelerated degradation was observed when dextran was incorporated in both the in vitro and in vivo assays, which led to earlier integration with cell and host tissue. The effect of dextran on degradation was ascribed to the decreased cross-linking density, looser microstructure, more porous and hydrophilic surface. Considering the better appearance, softness, moderate degradation rate due to controllable cross-linking degree and good biocompatibility as well, radiation-cross-linked collagen/dextran scaffolds are expected to serve as promising artificial dermal substitutes.

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

Directory of Open Access Journals (Sweden)

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.

Safety and efficacy of simultaneous corneal collagen cross-linking with topography-guided PRK in managing low-grade keratoconus: 1-year follow-up.

Science.gov (United States)

Tuwairqi, Waleed S; Sinjab, Mazen M

2012-05-01

To evaluate 1-year visual and topographic outcomes and safety and efficacy of corneal collagen cross-linking (CXL) combined with topography-guided photorefractive keratectomy (TG-PRK) to achieve near emmetropia in eyes with low-grade keratoconus. Twenty-two eyes from 15 patients (11 women, 4 men) were included in a prospective, nonrandomized, noncontrolled clinical study. Mean patient age was 26.6±6.07 years (range: 19 to 40 years). Inclusion criteria were low-grade keratoconus with evidence of progression, transparent cornea, corrected distance visual acuity (CDVA) 0.8 (decimal) or better, corneal thickness >440 μm, and maximum keratometry readings (K-max) PRK with CXL. Study parameters were uncorrected distance visual acuity, CDVA, manifest refractive error, manifest and topographic (corneal) astigmatism, patient satisfaction, and efficacy and safety of the treatment. Follow-up was 1 year. After 1 year, statistically significant improvement was noted in all study parameters (PPRK with CXL is an effective and safe treatment with remarkable visual and topographic outcomes in patients with low-grade keratoconus who meet the recommended inclusion criteria. Copyright 2012, SLACK Incorporated.

Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the athens protocol.

Science.gov (United States)

Kanellopoulos, Anastasios John; Binder, Perry S

2011-05-01

To evaluate a series of patients with corneal ectasia after LASIK that underwent the Athens Protocol: combined topography-guided photorefractive keratectomy (PRK) to reduce or eliminate induced myopia and astigmatism followed by sequential, same-day ultraviolet A (UVA) corneal collagen cross-linking (CXL). Thirty-two consecutive corneal ectasia cases underwent transepithelial PRK (WaveLight ALLEGRETTO) immediately followed by CXL (3 mW/cm(2)) for 30 minutes using 0.1% topical riboflavin sodium phosphate. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, keratometry, central ultrasonic pachymetry, corneal tomography (Oculus Pentacam), and endothelial cell counts were analyzed. Mean follow-up was 27 months (range: 6 to 59 months). Twenty-seven of 32 eyes had an improvement in UDVA and CDVA of 20/45 or better (2.25 logMAR) at last follow-up. Four eyes showed some topographic improvement but no improvement in CDVA. One of the treated eyes required a subsequent penetrating keratoplasty. Corneal haze grade 2 was present in 2 eyes. Combined, same-day, topography-guided PRK and CXL appeared to offer tomographic stability, even after long-term follow-up. Only 2 of 32 eyes had corneal ectasia progression after the intervention. Seventeen of 32 eyes appeared to have improvement in UDVA and CDVA with follow-up >1.5 years. This technique may offer an alternative in the management of iatrogenic corneal ectasia. Copyright 2011, SLACK Incorporated.

Corneal collagen cross-linking in the stabilization of PRK, LASIK, thermal keratoplasty, and orthokeratology.

Science.gov (United States)

Nguyen, Michelle K; Chuck, Roy S

2013-07-01

To describe the use of corneal collagen cross-linking (CXL) and its efficacy in the stabilization of keratorefractive procedures, including PRK, laser in-situ keratomileusis (LASIK), thermal keratoplasty, and orthokeratology. Since its introduction, CXL has quickly gained interest in the treatment of ectactic disorders due to its ability to increase the biomechanical stability of the cornea. In its earliest use, it has shown to be effective in the treatment of both keratoconus and post-LASIK ectasia. More recent studies of CXL in combination with keratorefractive procedures have shown varying degrees of success. CXL with PRK has shown to be effective in slowing or halting the progression of keratoconus, pellucid marginal degeneration, and post-LASIK ectasia, in addition to potentially decreasing or delaying the need for penetrating keratoplasty. Several small case series have also demonstrated improved stability and efficacy of PRK and LASIK when combined with CXL, as well as a potentially decreased risk of postprocedure ectasia. In conjunction with thermokeratoplasty and orthokeratology, CXL has shown improved but only temporary results in the treatment of keratoconus. Future studies are needed to determine the efficacy and long-term stability of CXL in combination with keratorefractive procedures, as well as to address possible complications.

Simultaneous topography-guided PRK followed by corneal collagen cross-linking after lamellar keratoplasty for keratoconus

Directory of Open Access Journals (Sweden)

Spadea L

2012-11-01

Full Text Available Leopoldo Spadea,1 Marino Paroli21University of L’Aquila, Department of Biotechnological and Applied Clinical Sciences, Eye Clinic, L’Aquila, 2La Sapienza University, Department of Biotechnology and Medical-Surgical Sciences, Latina, ItalyBackground: The purpose of this paper is to report the results of using combined treatment of customized excimer laser-assisted photorefractive keratectomy (PRK and prophylactic corneal collagen crosslinking (CXL for residual refractive error in a group of patients who had previously undergone lamellar keratoplasty for keratoconus.Methods: The study included 14 eyes from 14 patients who had originally been treated for keratoconus in one eye by excimer laser-assisted lamellar keratoplasty (ELLK, and subsequently presented with residual ametropia (-6.11 D ± 2.48, range -2.50 to -9.50. After a mean 40.1 ± 12.4 months since ELLK they underwent combined simultaneous corneal regularization treatment with topographically guided transepithelial excimer laser PRK (central corneal regularization and corneal CXL induced by riboflavin-ultraviolet A.Results: After a mean 15 ± 6.5 (range 6–24 months, all eyes gained at least one Snellen line of uncorrected distance visual acuity (range 1–10. No patient lost lines of corrected distance visual acuity, and four patients gained three lines of corrected distance visual acuity. Mean manifest refractive spherical equivalent was -0.79 ± 2.09 (range +1 to -3.0 D, and topographic keratometric astigmatism was 5.02 ± 2.93 (range 0.8–8.9 D. All the corneas remained clear (haze < 1.Conclusion: The combination of customized PRK and corneal CXL provided safe and effective results in the management of corneal regularization for refractive purposes after ELLK for keratoconus.Keywords: corneal collagen crosslinking, excimer laser-assisted lamellar keratoplasty, photorefractive keratectomy

A study comparing standard and transepithelial collagen cross-linking riboflavin solutions: epithelial findings and pain scores.

Science.gov (United States)

Yuksel, Erdem; Novruzlu, Shahin; Ozmen, Mehmet C; Bilgihan, Kamil

2015-06-01

To evaluate epithelial signs and pain after epithelial-on corneal collagen cross-linking (Epi-on CCL) with new transepithelial riboflavin formulation and epithelial-off corneal collagen cross-linking (Epi-off CCL) with standard riboflavin formulation and to compare pain and duration of epithelial healing between both techniques. Thirty-nine eyes of 39 patients undergoing Epi-on CCL and 39 eyes of 39 patients undergoing Epi-off CCL were evaluated. Corneal epithelial signs and durations of corneal epithelial healing and subjective pain scores after the procedures were recorded and compared between 2 groups. Total epithelialization was observed after 2.7 ± 0.7 days in Epi-on CCL and 2.3 ± 0.4 days in Epi-off CCL (P = 0.006). The mean pain score on the first day was 3.1 ± 0.6 in Epi-on CCL and 2.3 ± 0.4 in Epi-off CCL with a significant difference (P = 0.0001). The epithelial damage was observed in both procedures; also, the epithelial healing time was longer in Epi-on CCL and it is of great importance that the patients should have therapeutic contact lenses until the epithelium heals in both procedures. The Epi-off CCL group had less pain scores than the Epi-on CCL group and more pain problems after Epi-on CCL still remains. The patient should be informed about pain, even if the Epi-on CCL procedure was performed.

Optical coherence elastography for evaluating customized riboflavin/UV-A corneal collagen crosslinking

Science.gov (United States)

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

2017-09-01

UV-induced collagen cross-linking is a promising treatment for keratoconus that stiffens corneal tissue and prevents further degeneration. Since keratoconus is generally localized, the efficacy of collagen cross-linking (CXL) treatments could be improved by stiffening only the weakened parts of the cornea. Here, we demonstrate that optical coherence elastography (OCE) can spatially resolve transverse variations in corneal stiffness. A short duration (≤1 ms) focused air-pulse induced low amplitude (≤10 μm) deformations in the samples that were detected using a phase-stabilized optical coherence tomography system. A two-dimensional map of material stiffness was generated by measuring the damped natural frequency (DNF) of the air-pulse induced response at various transverse locations of a heterogeneous phantom mimicking a customized CXL treatment. After validation on the phantoms, similar OCE measurements were made on spatially selective CXL-treated in situ rabbit corneas. The results showed that this technique was able to clearly distinguish the untreated and CXL-treated regions of the cornea, where CXL increased the DNF of the cornea by ˜51%. Due to the noncontact nature and minimal excitation force, this technique may be valuable for in vivo assessments of corneal biomechanical properties.

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

Corneal Collagen Cross-Linking Combined with an Artiflex Iris-Fixated Anterior Chamber Phakic Intraocular Lens Implantation in a Patient with Progressive Keratoconus

Directory of Open Access Journals (Sweden)

Sharif Hashmani

2017-10-01

Full Text Available We present here the case of a 24-year-old male who experienced progressive keratoconus and vision loss which adversely affected his ability to carry out everyday tasks. This landed him in the Hashmanis Hospital for consultation. He had a preoperative best corrected visual acuity of 6/12. He underwent multiple Oculus Pentacam examinations, which showed progressive keratoconus. Corneal collagen cross-linking (CXL was performed to stabilize his cornea and, subsequently, an Artiflex anterior chamber iris-fixated phakic intraocular lens (ACIF-PIOL was implanted to alleviate his refractive errors. The patient achieved a postoperative uncorrected visual acuity of 6/12. This report shows that CXL combined with ACIF-PIOL can be safe and effective in those with progressive keratoconus.

Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane ...

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane – An Excellent Cell Substratum. The KERATINOCYTE proliferation and Differentiation into multiple layers is due to the presence of type - IV collagen in the amnion. Cultured FIBROBLASTS had good ...

Safety and Efficacy of Epithelium-On Corneal Collagen Cross-Linking Using a Multifactorial Approach to Achieve Proper Stromal Riboflavin Saturation

Directory of Open Access Journals (Sweden)

Aleksandar Stojanovic

2012-01-01

Full Text Available Purpose. To evaluate the efficacy and safety of epithelium-on corneal collagen cross-linking (CXL using a multifactorial approach to achieve proper stromal riboflavin saturation. Methods. This non-randomized retrospective study comprised 61 eyes with progressive keratoconus treated with epithelium-on CXL. Chemical epithelial penetration enhancement (benzalkonium chloride-containing local medication and hypotonic riboflavin solution, mechanical disruption of the superficial epithelium, and prolongation of the riboflavin-induction time until verification of stromal saturation were used before the UVA irradiation. Uncorrected and corrected distance visual acuity (UDVA, CDVA, refraction, corneal topography, and aberrometry were evaluated at baseline and at 1, 3, 6, and 12 months postoperative. Results. At 12-month, UDVA and CDVA improved significantly. None of the eyes lost lines of CDVA, while 27.4% of the eyes gained 2 or more lines. Mean spherical equivalent decreased by 0.74 D, and mean cylindrical reduction was 1.15 D. Irregularity index and asymmetry from Scheimpflug-based topography and Max-K at the location of cone from Placido-based topography showed a significant decrease. Higher-order-aberration data demonstrated a slight reduction in odd-order aberrations S 3, 5,7 (=0.04. Postoperative pain without other complications was recorded. Conclusion. Epithelium-on CXL with our novel protocol appeared to be safe and effective in the treatment of progressive keratoconus.

Simultaneous topography-guided PRK followed by corneal collagen cross-linking after lamellar keratoplasty for keratoconus.

Science.gov (United States)

Spadea, Leopoldo; Paroli, Marino

2012-01-01

The purpose of this paper is to report the results of using combined treatment of customized excimer laser-assisted photorefractive keratectomy (PRK) and prophylactic corneal collagen crosslinking (CXL) for residual refractive error in a group of patients who had previously undergone lamellar keratoplasty for keratoconus. The study included 14 eyes from 14 patients who had originally been treated for keratoconus in one eye by excimer laser-assisted lamellar keratoplasty (ELLK), and subsequently presented with residual ametropia (-6.11 D ± 2.48, range -2.50 to -9.50). After a mean 40.1 ± 12.4 months since ELLK they underwent combined simultaneous corneal regularization treatment with topographically guided transepithelial excimer laser PRK (central corneal regularization) and corneal CXL induced by riboflavin-ultraviolet A. After a mean 15 ± 6.5 (range 6-24) months, all eyes gained at least one Snellen line of uncorrected distance visual acuity (range 1-10). No patient lost lines of corrected distance visual acuity, and four patients gained three lines of corrected distance visual acuity. Mean manifest refractive spherical equivalent was -0.79 ± 2.09 (range +1 to -3.0) D, and topographic keratometric astigmatism was 5.02 ± 2.93 (range 0.8-8.9) D. All the corneas remained clear (haze PRK and corneal CXL provided safe and effective results in the management of corneal regularization for refractive purposes after ELLK for keratoconus.

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. © 2014 Wiley Periodicals, Inc.

Collagen cross-linking: insights on the evolution of metazoan extracellular matrix.

Science.gov (United States)

Rodriguez-Pascual, Fernando; Slatter, David Anthony

2016-11-23

Collagens constitute a large family of extracellular matrix (ECM) proteins that play a fundamental role in supporting the structure of various tissues in multicellular animals. The mechanical strength of fibrillar collagens is highly dependent on the formation of covalent cross-links between individual fibrils, a process initiated by the enzymatic action of members of the lysyl oxidase (LOX) family. Fibrillar collagens are present in a wide variety of animals, therefore often being associated with metazoan evolution, where the emergence of an ancestral collagen chain has been proposed to lead to the formation of different clades. While LOX-generated collagen cross-linking metabolites have been detected in different metazoan families, there is limited information about when and how collagen acquired this particular modification. By analyzing telopeptide and helical sequences, we identified highly conserved, potential cross-linking sites throughout the metazoan tree of life. Based on this analysis, we propose that they have importantly contributed to the formation and further expansion of fibrillar collagens.

Comparison of Aqueous Humor Nitric Oxide Levels After Different Corneal Collagen Cross-Linking Methods.

Science.gov (United States)

Yuksel, Nilay; Ozel-Turkcu, Ummuhani; Yalinbas, Duygu; Novruzlu, Sahin; Bilgihan, Ayse; Bilgihan, Kamil

2016-12-01

Nitric oxide production can cause either apoptotic or necrotic cell death through oxidative stress. We aimed to investigate the nitrite oxide metabolites (NO x ) and nitrite levels in the aqueous humor of rabbit eyes after different methods of corneal collagen cross-linking (CXL). Twenty-four eyes of 12 adult New Zealand rabbits were used. They were assigned into four groups, each including six eyes. Group 1 (control) consisted of eyes with no treatment. Group 2 received UV-A power setting at 3 mW/cm 2 for 30 minutes of continuous exposure and named as standard CXL group. Group 3 received UV-A power setting at 30 mW/cm 2 for 3 minutes of continuous exposure and named as accelerated CXL (A-CXL) group. Group 4 received UV-A power setting at 30 mW/cm 2 for 6 minutes of pulsed exposure (1 sec on, 1 sec off) and named as pulse-light accelerated CXL (PLA-CXL). Aqueous humors were aspirated from anterior chamber with a 27G needle after 1 hour UV-A exposure. NO x and nitrite levels were measured Results: The nitrite levels in aqueous humor were significantly increased in Group 2 and Group 3 when compared with Group 1 (p = 0.000, p = 0.036, respectively). When treatment modalities were compared with each other, high nitrite level in Group 2 was statistically significant when compared with Group 4 (p = 0.019). NO x levels were higher in Group 2 when compared with Group 1 (p = 0.006). Numerous studies investigated the physiological and pathophysiological roles of NO. NO is considered one of the most important molecule for ocular health. According to NO x level in aqueous humor, it seems that PLA-CXL is the safest method due to the similar results with control group.

Laser-induced corneal cross-linking upon photorefractive ablation with riboflavin

Directory of Open Access Journals (Sweden)

Kornilovskiy IM

2016-04-01

Full Text Available Igor M Kornilovskiy,1 Elmar M Kasimov,2 Ayten I Sultanova,2 Alexander A Burtsev1 1Department of Eye Diseases, Federal State Budgetary Institution “National Pirogov Medical Surgical Centre”, Ministry of Health, Moscow, Russia; 2Department of Eye Diseases, Zarifa Aliyeva National Ophthalmology Center, Ministry of Health, Baku, Azerbaijan Aim: To estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with riboflavin.Methods: Excimer laser ablation studies were performed ex vivo (32 eyes of 16 rabbits by phototherapeutic keratectomy (PTK and in vivo (24 eyes of 12 rabbits by transepithelial photorefractive keratectomy (TransPRK, with and without riboflavin saturation of the stroma. Then, we performed corneal optical coherence tomography on 36 eyes of 18 patients with varying degrees of myopia at different times after the TransPRK was performed with riboflavin saturation of the stroma.Results: Biomechanical testing of corneal samples saturated with riboflavin revealed cross-linking effect accompanied by the increase in tensile strength and maximum strength. PTK showed increase in tensile strength from 5.1±1.4 to 7.2±1.6 MPa (P=0.001, while TransPRK showed increase in tensile strength from 8.8±0.9 to 12.8±1.3 MPa (P=0.0004. Maximum strength increased from 8.7±2.5 to 12.0±2.8 N (P=0.005 in PTK and from 12.8±1.6 to 18.3±1.2 N (P=0.0004 in TransPRK. Clinical optical coherence tomography studies of the biomicroscopic transparent cornea at different times after TransPRK showed increased density in the surface layers of the stroma and membrane-like structure beneath the epithelium.Conclusion: Photorefractive ablation of the preliminary corneal stroma saturation with riboflavin causes the effect of laser-induced cross-linking, which is attended with an increase in corneal tensile strength, maximum strength, increased density in the surface layers of the stroma, and formation of

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

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

Stabilization of collagen nanofibers with l-lysine improves the ability of carbodiimide cross-linked amniotic membranes to preserve limbal epithelial progenitor cells

Directory of Open Access Journals (Sweden)

Lai JY

2014-11-01

provide a useful strategy to assist in the development of carbodiimide cross-linked amniotic membrane as a stable stem cell niche for corneal epithelial tissue engineering.Keywords: amniotic membrane, L-lysine-pretreated concentration, collagen nanofiber stabilization, limbal progenitor cell preservation, corneal epithelial tissue engineering

The Effect of Riboflavin/UVA Collagen Cross-linking Therapy on the Structure and Hydrodynamic Behaviour of the Ungulate and Rabbit Corneal Stroma

Science.gov (United States)

Hayes, Sally; Kamma-Lorger, Christina S.; Boote, Craig; Young, Robert D.; Quantock, Andrew J.; Rost, Anika; Khatib, Yasmeen; Harris, Jonathan; Yagi, Naoto; Terrill, Nicholas; Meek, Keith M.

2013-01-01

Purpose To examine the effect of riboflavin/UVA corneal crosslinking on stromal ultrastructure and hydrodynamic behaviour. Methods One hundred and seventeen enucleated ungulate eyes (112 pig and 5 sheep) and 3 pairs of rabbit eyes, with corneal epithelium removed, were divided into four treatment groups: Group 1 (28 pig, 2 sheep and 3 rabbits) were untreated; Group 2 (24 pig) were exposed to UVA light (3.04 mW/cm2) for 30 minutes and Group 3 (29 pig) and Group 4 (31 pig, 3 sheep and 3 rabbits) had riboflavin eye drops applied to the corneal surface every 5 minutes for 35 minutes. Five minutes after the initial riboflavin instillation, the corneas in Group 4 experienced a 30 minute exposure to UVA light (3.04 mW/cm2). X-ray scattering was used to obtain measurements of collagen interfibrillar spacing, spatial order, fibril diameter, D-periodicity and intermolecular spacing throughout the whole tissue thickness and as a function of tissue depth in the treated and untreated corneas. The effect of each treatment on the hydrodynamic behaviour of the cornea (its ability to swell in saline solution) and its resistance to enzymatic digestion were assessed using in vitro laboratory techniques. Results Corneal thickness decreased significantly following riboflavin application (priboflavin/UVA therapy occur predominantly at the collagen fibril surface and in the protein network surrounding the collagen. PMID:23349690

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

NARCIS (Netherlands)

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

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

Cross-linking of dermal sheep collagen 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

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

Two-photon induced collagen cross-linking in bioartificial cardiac tissue

Science.gov (United States)

Kuetemeyer, Kai; Kensah, George; Heidrich, Marko; Meyer, Heiko; Martin, Ulrich; Gruh, Ina; Heisterkamp, Alexander

2011-08-01

Cardiac tissue engineering is a promising strategy for regenerative therapies to overcome the shortage of donor organs for transplantation. Besides contractile function, the stiffness of tissue engineered constructs is crucial to generate transplantable tissue surrogates with sufficient mechanical stability to withstand the high pressure present in the heart. Although several collagen cross-linking techniques have proven to be efficient in stabilizing biomaterials, they cannot be applied to cardiac tissue engineering, as cell death occurs in the treated area. Here, we present a novel method using femtosecond (fs) laser pulses to increase the stiffness of collagen-based tissue constructs without impairing cell viability. Raster scanning of the fs laser beam over riboflavin-treated tissue induced collagen cross-linking by two-photon photosensitized singlet oxygen production. One day post-irradiation, stress-strain measurements revealed increased tissue stiffness by around 40% being dependent on the fibroblast content in the tissue. At the same time, cells remained viable and fully functional as demonstrated by fluorescence imaging of cardiomyocyte mitochondrial activity and preservation of active contraction force. Our results indicate that two-photon induced collagen cross-linking has great potential for studying and improving artificially engineered tissue for regenerative therapies.

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.

Combined application of prophylactic corneal cross-linking and laser in-situ keratomileusis - a review of literature.

Science.gov (United States)

Chan, Tommy C Y; Ng, Alex L K; Chan, Karen K W; Cheng, George P M; Wong, Ian Y H; Jhanji, Vishal

2017-11-01

Laser in-situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross-linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross-linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea. During the procedure, riboflavin is directly applied to the corneal stroma, thereby reducing the need of de-epithelialization as in the conventional protocol for keratoconus. Currently, there is still no consensus regarding the indication of CXL during refractive procedure, nor any standardized treatment protocol. This article aims to summarize the current evidence regarding the use of adjuvant CXL in LASIK. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

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�

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

Directory of Open Access Journals (Sweden)

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

Collagen and elastin cross-linking is altered during aberrant late lung development associated with hyperoxia.

Science.gov (United States)

Mižíková, Ivana; Ruiz-Camp, Jordi; Steenbock, Heiko; Madurga, Alicia; Vadász, István; Herold, Susanne; Mayer, Konstantin; Seeger, Werner; Brinckmann, Jürgen; Morty, Rory E

2015-06-01

Maturation of the lung extracellular matrix (ECM) plays an important role in the formation of alveolar gas exchange units. A key step in ECM maturation is cross-linking of collagen and elastin, which imparts stability and functionality to the ECM. During aberrant late lung development in bronchopulmonary dysplasia (BPD) patients and animal models of BPD, alveolarization is blocked, and the function of ECM cross-linking enzymes is deregulated, suggesting that perturbed ECM cross-linking may impact alveolarization. In a hyperoxia (85% O2)-based mouse model of BPD, blunted alveolarization was accompanied by alterations to lung collagen and elastin levels and cross-linking. Total collagen levels were increased (by 63%). The abundance of dihydroxylysinonorleucine collagen cross-links and the dihydroxylysinonorleucine-to-hydroxylysinonorleucine ratio were increased by 11 and 18%, respectively, suggestive of a profibrotic state. In contrast, insoluble elastin levels and the abundance of the elastin cross-links desmosine and isodesmosine in insoluble elastin were decreased by 35, 30, and 21%, respectively. The lung collagen-to-elastin ratio was threefold increased. Treatment of hyperoxia-exposed newborn mice with the lysyl oxidase inhibitor β-aminopropionitrile partially restored normal collagen levels, normalized the dihydroxylysinonorleucine-to-hydroxylysinonorleucine ratio, partially normalized desmosine and isodesmosine cross-links in insoluble elastin, and partially restored elastin foci structure in the developing septa. However, β-aminopropionitrile administration concomitant with hyperoxia exposure did not improve alveolarization, evident from unchanged alveolar surface area and alveoli number, and worsened septal thickening (increased by 12%). These data demonstrate that collagen and elastin cross-linking are perturbed during the arrested alveolarization of developing mouse lungs exposed to hyperoxia. Copyright © 2015 the American Physiological Society.

Primary Outcomes of Accelerated Epithelium-Off Corneal Cross-Linking in Progressive Keratoconus in Children: A 1-Year Prospective Study

Directory of Open Access Journals (Sweden)

Sherif A. Eissa

2017-01-01

Full Text Available Purpose. To evaluate corneal transparency following accelerated collagen cross-linking (ACXL in pediatric keratoconus. Design. A prospective interventional case series. Methods. This study included 47 eyes (25 patients, aged 9–14 years, with documented progressive keratoconus. After applying 0.1% riboflavin drops, ACXL was performed. Assessment included corrected distance visual acuity (CDVA, uncorrected visual acuity (UCVA, corneal haze, and corneal densitometry in grayscale units (GSU. Result. The mean baseline and corneal densitometry peaked at 3 months post-ACXL while central and posterior densitometry showed a statistically significant increase (P<0.05 and peaked at 8 months postoperatively. By 12 months, densitometry in all corneal layers (P≥0.99 and concentric zones (P≥0.97 reached near baseline values. Slit-lamp graded haze peaked at 1 month to 1.82 ± 0.65 (P<0.05 and declined to near baseline at 12 months (0.39 ± 0.58. There was a statistically significant increase in the mean UCVA and CDVA at 12 months. Conclusion. Total and anterior corneal densitometry peaked after 3 months, while central and posterior densitometry peaked after 8 months. Maximum haze was at 1 month post-ACXL. All corneal layers, concentric zone densitometry and haze reached near baseline values after 1 year. Scheimpflug densitometry showed weak correlation with CDVA over the 12-month follow-up period (r=−0.193.

The mechanism of collagen cross-linking in diabetes: a puzzle nearing resolution.

Science.gov (United States)

Monnier, V M; Glomb, M; Elgawish, A; Sell, D R

1996-07-01

Considerable interest has been focused in recent years on the mechanism of collagen cross-linking by high glucose in vitro and in vivo. Experiments in both diabetic humans and in animals have shown that over time collagen becomes less soluble, less digestible by collagenase, more stable to heat-induced denaturation, and more glycated. In addition, collagen becomes more modified by advanced products of the Maillard reaction, i.e., immunoreactive advanced glycation end products and the glycoxidation markers carboxymethyllysine and pentosidine. Mechanistic studies have shown that collagen cross-linking in vitro can be uncoupled from glycation by the use of antioxidants and chelating agents. Experiments in the authors' laboratory revealed that approximately 50% of carboxymethyllysine formed in vitro originates from pathways other than oxidation of Amadori products, i.e., most likely the oxidation of Schiff base-linked glucose. In addition, the increase in thermal stability of rat tail tendons exposed to high glucose in vitro or in vivo was found to strongly depend on H2O2 formation. The final missing piece of the puzzle is that of the structure of the major cross-link. We speculate that it is a nonfluorescent nonultraviolet active cross-link between two lysine residues, which includes a fragmentation product of glucose linked in a nonreducible bond labile to both strong acids and bases.

The theory and art of corneal cross-linking.

Science.gov (United States)

McQuaid, Rebecca; Cummings, Arthur B; Mrochen, Michael

2013-08-01

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.

Efficacy of iontophoresis-assisted epithelium-on corneal cross-linking for keratoconus

Directory of Open Access Journals (Sweden)

Hong-Zhen Jia

2018-04-01

Full Text Available Corneal cross-linking (CXL is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is accomplished by ultraviolet A (UVA radiation of the cornea, which is first saturated with photosensitizing riboflavin. It has been shown that standard epithelium-off CXL (S-CXL is efficacious, and it has been recommended as the standard of care procedure for keratoconus. However, epithelial removal leads to pain, transient vision loss, and a higher risk of corneal infection. To avoid these disadvantages, transepithelial CXL was developed. Recently, iontophoresis has been adopted to increase riboflavin penetration through the epithelium. Several clinical observations have demonstrated the safety and efficacy of iontophoresis-assisted epithelium-on CXL (I-CXL for keratoconus. This review aimed to provide a comprehensive summary of the published studies regarding I-CXL and a comparison between I-CXL and S-CXL. All articles used in this review were mainly retrieved from the PubMed database. Original articles and reviews were selected if they were related to the I-CXL technique or related to the comparison between I-CXL and S-CXL.

The theory and art of corneal cross-linking

Directory of Open Access Journals (Sweden)

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.

Corneal-Wavefront guided transepithelial photorefractive keratectomy after corneal collagen cross linking in keratoconus

Directory of Open Access Journals (Sweden)

Massimo Camellin

2017-01-01

Conclusions: Corneal-Wavefront guided transepithelial PRK ablation profiles after conventional CXL yields to good visual, optical, and refractive results. These treatments are safe and efficacious for the correction of refracto-therapeutic problems in keratoconic patients.

Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen.

Science.gov (United States)

Terajima, Masahiko; Taga, Yuki; Chen, Yulong; Cabral, Wayne A; Hou-Fu, Guo; Srisawasdi, Sirivimol; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Kurie, Jonathan M; Marini, Joan C; Yamauchi, Mitsuo

2016-04-29

Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1-3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Cyclophilin-B Modulates Collagen Cross-linking by Differentially Affecting Lysine Hydroxylation in the Helical and Telopeptidyl Domains of Tendon Type I Collagen*

Science.gov (United States)

Terajima, Masahiko; Taga, Yuki; Chen, Yulong; Cabral, Wayne A.; Hou-Fu, Guo; Srisawasdi, Sirivimol; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Kurie, Jonathan M.; Marini, Joan C.; Yamauchi, Mitsuo

2016-01-01

Covalent intermolecular cross-linking provides collagen fibrils with stability. The cross-linking chemistry is tissue-specific and determined primarily by the state of lysine hydroxylation at specific sites. A recent study on cyclophilin B (CypB) null mice, a model of recessive osteogenesis imperfecta, demonstrated that lysine hydroxylation at the helical cross-linking site of bone type I collagen was diminished in these animals (Cabral, W. A., Perdivara, I., Weis, M., Terajima, M., Blissett, A. R., Chang, W., Perosky, J. E., Makareeva, E. N., Mertz, E. L., Leikin, S., Tomer, K. B., Kozloff, K. M., Eyre, D. R., Yamauchi, M., and Marini, J. C. (2014) PLoS Genet. 10, e1004465). However, the extent of decrease appears to be tissue- and molecular site-specific, the mechanism of which is unknown. Here we report that although CypB deficiency resulted in lower lysine hydroxylation in the helical cross-linking sites, it was increased in the telopeptide cross-linking sites in tendon type I collagen. This resulted in a decrease in the lysine aldehyde-derived cross-links but generation of hydroxylysine aldehyde-derived cross-links. The latter were absent from the wild type and heterozygous mice. Glycosylation of hydroxylysine residues was moderately increased in the CypB null tendon. We found that CypB interacted with all lysyl hydroxylase isoforms (isoforms 1–3) and a putative lysyl hydroxylase-2 chaperone, 65-kDa FK506-binding protein. Tendon collagen in CypB null mice showed severe size and organizational abnormalities. The data indicate that CypB modulates collagen cross-linking by differentially affecting lysine hydroxylation in a site-specific manner, possibly via its interaction with lysyl hydroxylases and associated molecules. This study underscores the critical importance of collagen post-translational modifications in connective tissue formation. PMID:26934917

Peripheral hepatic arterial embolization with cross-linked collagen fibers

International Nuclear Information System (INIS)

Daniels, J.R.; Kerlan, R.K. Jr.; Dodds, L.; McLaughlin, P.; La Berge, J.M.; Harrington, D.; Daniels, A.M.; Ring, E.J.

1986-01-01

Hepatic artery embolization with a nonimmunogenic, cross-linked collagen preparation (Angiostat, collagen for embolization, Target Therapeutics) was studied in mongrel dogs. Flow-directed technique was used to achieve complete distal arterial occlusion. Serial liver function evaluation demonstrated marked alterations at 48 to 72 hours, partial correction at 1 week, and resolution of abnormalities by 1 month. Restoration of large-vessel blood flow was angiographically demonstrable at 1 week. Recanalization, achieved by migration of endothelial cells around the collagen, resulted in complete restoration of normal hepatic vascular and tissue anatomy at 1 month. Repeated embolization at biweekly intervals was well tolerated

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

Glutaraldehyde cross-linking of amniotic membranes affects their nanofibrous structures and limbal epithelial cell culture characteristics.

Science.gov (United States)

Lai, Jui-Yang; Ma, David Hui-Kang

2013-01-01

Given that the cells can sense nanometer dimensions, the chemical cross-linking-mediated alteration in fibrillar structure of collagenous tissue scaffolds is critical to determining their cell culture performances. This article explores, for the first time, the effect of nanofibrous structure of glutaraldehyde (GTA) cross-linked amniotic membrane (AM) on limbal epithelial cell (LEC) cultivation. Results of ninhydrin assays demonstrated that the amount of new cross-links formed between the collagen chains is significantly increased with increasing the cross-linking time from 1 to 24 hours. By transmission electron microscopy, the AM treated with GTA for a longer duration exhibited a greater extent of molecular aggregation, thereby leading to a considerable increase in nanofiber diameter and resistance against collagenase degradation. In vitro biocompatibility studies showed that the samples cross-linked with GTA for 24 hours are not well-tolerated by the human corneal epithelial cell cultures. When the treatment duration is less than 6 hours, the biological tissues cross-linked with GTA for a longer time may cause slight reductions in 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt, and anti-inflammatory activities. Nevertheless, significant collagen molecular aggregation also enhances the stemness gene expression, indicating a high ability of these AM matrices to preserve the progenitors of LECs in vitro. It is concluded that GTA cross-linking of collagenous tissue materials may affect their nanofibrous structures and corneal epithelial stem cell culture characteristics. The AM treated with GTA for 6 hours holds promise for use as a niche for the expansion and transplantation of limbal epithelial progenitor cells.

Collagen cross-linking in sun-exposed and unexposed sites of aged human skin

Science.gov (United States)

Yamauchi, M.; Prisayanh, P.; Haque, Z.; Woodley, D. T.

1991-01-01

A recently described nonreducible, acid-heat stable compound, histidinohydroxylysinonorleucine (HHL), is a collagen cross-link isolated from mature skin tissue. Its abundance is related to chronologic aging of skin. The present communication describes the quantity of HHL from aged human skin of the same individuals in sun-exposed (wrist) and unexposed (buttock) sites. Punch biopsies were obtained from these sites from nine people of age 60 or older. HHL contents (moles/mole of collagen) at these sites were for wrist 0.13 +/- 0.07 and for buttock 0.69 +/- 0.17 (mean +/- SD, p less than 0.001). In addition, it was found that acute irradiation of the cross-linked peptides with UVA (up to 250 J/cm2) and UVB (up to 1 J/cm2) had no effect on HHL structure. The same treatment significantly degraded another nonreducible, stable collagen cross-link, pyridinoline. The results suggest that chronic sunlight exposure may be associated with an impediment to normal maturation of human dermal collagen resulting in tenuous amount of HHL. Thus, the process of photoaging in dermal collagen is different from that of chronologic aging in human skin.

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

Thermal and infrared-diode laser effects on indocyanine-green-treated corneal collagen

Science.gov (United States)

Timberlake, George T.; Patmore, Ann; Shallal, Assaad; McHugh, Dominic; Marshall, John

1993-07-01

It has been suggested that laser welds of collagenous tissues form by interdigitation and chemical bonding of thermally 'unraveled' collagen fibrils. We investigated this proposal by attempting to weld highly collagenous, avascular corneal tissue with an infrared (IR) diode laser as follows. First, the temperature at which corneal collagen shrinks and collagen fibrils 'split' into subfibrillary components was determined. Second, since use of a near-IR laser wavelength necessitated addition of an absorbing dye (indocyanine green (ICG) to the cornea, we measured absorption spectra of ICG-treated tissue to ensure that peak ICG absorbance did not change markedly when ICG was present in the cornea. Third, using gel electrophoresis of thermally altered corneal collagen, we searched for covalently crosslinked compounds predicted by the proposed welding mechanism. Finally, we attempted to weld partial thickness corneal incisions infused with ICG. Principal experimental findings were as follows: (1) Human corneal (type I) collagen splits into subfibrillary components at approximately 63 degree(s)C, the same temperature that produces collagen shrinkage. (2) Peak ICG absorption does not change significantly in corneal stroma or with laser heating. (3) No evidence was found for the formation of novel compounds or the loss of proteins as a result of tissue heating. All tissue treated with ICG, however, exhibited a novel 244 kD protein band indicating chemical activity between collagen and corneal stromal components. (4) Laser welding corneal incisions was unsuccessful possibly due to shrinkage of the sides of the incision, lack of incision compression during heating, or a less than optimal combination of ICG concentration and radiant exposure. In summary, these experiments demonstrate the biochemical and morphological complexity of ICG-enhanced IR laser-tissue welding and the need for further investigation of laser welding mechanisms.

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.

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.

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.

Evaluation of nanohydroxyapaptite (nano-HA) coated epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes.

Science.gov (United States)

Chu, Chenyu; Deng, Jia; Man, Yi; Qu, Yili

2017-09-01

Collagen is the main component of extracellular matrix (ECM) with desirable biological activities and low antigenicity. Collagen materials have been widely utilized in guided bone regeneration (GBR) surgery due to its abilities to maintain space for hard tissue growth. However, pure collagen lacks optimal mechanical properties. In our previous study, epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes, with better biological activities and enhanced mechanical properties, may promote osteoblast proliferation, but their effect on osteoblast differentiation is not very significant. Nanohydroxyapatite (nano-HA) is the main component of mineral bone, which possesses exceptional bioactivity properties including good biocompatibility, high osteoconductivity and osteoinductivity, non-immunogenicity and non-inflammatory behavior. Herein, by analyzing the physical and chemical properties as well as the effects on promoting bone regeneration, we have attempted to present a novel EGCG-modified collagen membrane with nano-HA coating, and have found evidence that the novel collagen membrane may promote bone regeneration with a better surface morphology, without destroying collagen backbone. To evaluate the surface morphologies, chemical and mechanical properties of pure collagen membranes, epigallocatechin-3-gallate (EGCG) cross-linked collagen membranes, nano-HA coated collagen membranes, nano-HA coated EGCG-collagen membranes, (ii) to evaluate the bone regeneration promoted by theses membranes. In the present study, collagen membranes were divided into 4 groups: (1) untreated collagen membranes (2) EGCG cross-linked collagen membranes (3) nano-HA modified collagen membranes (4) nano-HA modified EGCG-collagen membranes. Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to evaluate surface morphologies and chemical properties, respectively. Mechanical properties were determined by differential scanning calorimeter (DSC

Late onset of a persistent, deep stromal scarring after PRK and corneal cross-linking in a patient with forme fruste keratoconus.

Science.gov (United States)

Güell, Jose L; Verdaguer, Paula; Elies, Daniel; Gris, Oscar; Manero, Felicidad

2014-04-01

To present a case of a late, deep stromal scar in a 22-year-old patient with forme fruste keratoconus who underwent combined corneal cross-linking and photorefractive keratectomy (PRK). Topography-guided corneal cross-linking combined with corneal PRK (without complications) was performed in both eyes with a delay of 2 weeks between each eye. At the 5-month postoperative examination of the right eye, a localized corneal haze was circumscribed to the posterior deep stroma, signifying a decrease of visual acuity. However, this improved partially and temporarily when treated with topical corticoids during 2 years of follow-up and then reoccurred, affecting the corrected distance visual acuity. To the authors' knowledge, this is the first documented, clinical case presenting a deep stromal affectation without endothelial decompensation and visual acuity affectation as a postoperative complication following topography-guided PRK and corneal cross-linking. Copyright 2014, SLACK Incorporated.

Corneal collagen crosslinking and pigment dispersion syndrome.

Science.gov (United States)

LaHood, Benjamin R; Moore, Sacha

2017-03-01

We describe the case of a keratoconus patient with pigment dispersion syndrome (PDS) who was treated for progressive corneal ectasia with corneal collagen crosslinking (CXL). Pigment dispersion syndrome has been shown to have associated morphologic changes of the corneal endothelium. Corneal CXL has the potential to cause toxicity to the corneal endothelium, and adjacent pigment might increase the likelihood of damage. In this case, the presence of PDS had no detrimental effect on the outcome of treatment, and no complications were observed at 12 months follow-up, indicating that it may be safe to perform corneal CXL in the setting of PDS. This is an important observation as the number of indications for corneal CXL grows. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Cross-linking in collagen by nonenzymatic glycation increases the matrix stiffness in rabbit achilles tendon.

Science.gov (United States)

Reddy, G Kesava

2004-01-01

Nonenzymatic glycation of connective tissue matrix proteins is a major contributor to the pathology of diabetes and aging. Previously the author and colleagues have shown that nonenzymatic glycation significantly enhances the matrix stability in the Achilles tendon (Reddy et al., 2002, Arch. Biochem. Biophys., 399, 174-180). The present study was designed to gain further insight into glycation-induced collagen cross-linking and its relationship to matrix stiffness in the rabbit Achilles tendon. The glycation process was initiated by incubating the Achilles tendons (n = 6) in phosphate-buffered saline containing ribose, whereas control tendons (n = 6) were incubated in phosphate-buffered saline without ribose. Eight weeks following glycation, the biomechanical attributes as well as the degree of collagen cross-linking were determined to examine the potential associations between matrix stiffness and molecular properties of collagen. Compared to nonglycated tendons, the glycated tendons showed increased maximum load, stress, strain, Young's modulus of elasticity, and toughness indicating that glycation increases the matrix stiffness in the tendons. Glycation of tendons resulted in a considerable decrease in soluble collagen content and a significant increase in insoluble collagen and pentosidine. Analysis of potential associations between the matrix stiffness and degree of collagen cross-linking showed that both insoluble collagen and pentosidine exhibited a significant positive correlation with the maximum load, stress, and strain, Young's modulus of elasticity, and toughness (r values ranging from.61 to.94) in the Achilles tendons. However, the soluble collagen content present in neutral salt buffer, acetate buffer, and acetate buffer containing pepsin showed an inverse relation with the various biomechanical attributes tested (r values ranging from.22 to.84) in the Achilles tendons. The results of the study demonstrate that glycation-induced collagen cross-linking

Effect of corneal cross-linking on contact lens tolerance in keratoconus.

Science.gov (United States)

Ünlü, Metin; Yüksel, Erdem; Bilgihan, Kamil

2017-07-01

The aim was to investigate changes in corneal sensation and rigid gas-permeable (RGP) contact lens tolerance after corneal cross-linking (CXL) on patients with keratoconus. Thirty eyes of 30 patients, who were RGP lens intolerant, were treated with CXL. The main outcome measures were corneal sensation evaluation by Cochet-Bonnet esthesiometry, sub-basal nerve fibre assessment by corneal in vivo confocal microscopy and RGP contact lens tolerance evaluation with the Likert scale and wearing time. All eyes were evaluated preoperatively and post-operatively at one, three and six months after CXL procedure. The mean age was 25.3 ± 6.2 years. Preoperatively, the maximum keratometry (Kmax) in study eyes was 56.89 ± 4.60 D. Six months after CXL, it reduced to 56.03 ± 4.85 D (p = 0.01). Preoperative mean corneal sensation was 0.44 ± 0.05 g/mm 2 , (range: 0.40 to 0.55); it was significantly decreased at the first month and increased to preoperative values after six months. The sub-basal nerve plexus could not be visualised in 90 per cent of the patients by confocal microscopy at one month post-operatively. Gradual restoration of corneal innervation with almost similar preoperative levels at post-operative month six was noted. There were significant differences in Likert scores between preoperative and third and sixth months after CXL. Likert scale scores correlated significantly with corneal sensitivity. It can be concluded that increased RGP contact lens tolerance after CXL may be associated with the potential role of decreased corneal sensitivity and corneal flattening after CXL. © 2016 Optometry Australia.

SECONDARY CYTOTOXICITY OF CROSS-LINKED DERMAL SHEEP COLLAGENS DURING REPEATED EXPOSURE TO HUMAN FIBROBLASTS

NARCIS (Netherlands)

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

1992-01-01

We investigated commercially available dermal sheep collagen either cross-linked with hexamethylenedlisocyanate, or cross-linked with glutaraldehyde. In previous in vitro studies we could discriminate primary, i.e. extractable, and secondary cytotoxicity, due to cell-biomaterial interactions, i.e.

Accelerated corneal collagen cross-linking in pediatric keratoconus: One year study

Directory of Open Access Journals (Sweden)

Amani E. Badawi

2017-01-01

Conclusion: Accelerated CXL shows a stabilization and beneficial clinical outcomes in pediatric keratoconus. It seems an effective and safe procedure in this age group. Effects of accelerated CXL on the posterior corneal surface will need further evaluation.

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.

Glutaraldehyde cross-linking of amniotic membranes affects their nanofibrous structures and limbal epithelial cell culture characteristics

Directory of Open Access Journals (Sweden)

Lai JY

2013-10-01

Full Text Available Jui-Yang Lai,1–3 David Hui-Kang Ma4,5 1Institute of Biochemical and Biomedical Engineering, 2Biomedical Engineering Research Center, 3Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan; 4Limbal Stem Cell Laboratory, Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan; 5Department of Chinese Medicine, Chang Gung University, Taoyuan, Taiwan Abstract: Given that the cells can sense nanometer dimensions, the chemical cross-linking-mediated alteration in fibrillar structure of collagenous tissue scaffolds is critical to determining their cell culture performances. This article explores, for the first time, the effect of nanofibrous structure of glutaraldehyde (GTA cross-linked amniotic membrane (AM on limbal epithelial cell (LEC cultivation. Results of ninhydrin assays demonstrated that the amount of new cross-links formed between the collagen chains is significantly increased with increasing the cross-linking time from 1 to 24 hours. By transmission electron microscopy, the AM treated with GTA for a longer duration exhibited a greater extent of molecular aggregation, thereby leading to a considerable increase in nanofiber diameter and resistance against collagenase degradation. In vitro biocompatibility studies showed that the samples cross-linked with GTA for 24 hours are not well-tolerated by the human corneal epithelial cell cultures. When the treatment duration is less than 6 hours, the biological tissues cross-linked with GTA for a longer time may cause slight reductions in 3-(4,5-dimethylthiazol-2-yl-5-(3-carboxymethoxyphenyl-2-(4-sulfophenyl-2H-tetrazolium, inner salt, and anti-inflammatory activities. Nevertheless, significant collagen molecular aggregation also enhances the stemness gene expression, indicating a high ability of these AM matrices to preserve the progenitors of LECs in vitro. It is concluded that GTA cross-linking of collagenous tissue materials may affect their nanofibrous

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.

Investigation on fibrous collagen modifications during corneal laser welding by second harmonic generation microscopy

Science.gov (United States)

Matteini, Paolo; Ratto, Fulvio; Rossi, Francesca; Cicchi, Riccardo; Stringari, Chiara; Kapsokalyvas, Dimitrios; Pavone, Francesco S.; Pini, Roberto

2009-02-01

The structural modifications in the collagen lattice of corneal stroma induced by near-infrared laser welding were investigated with second-harmonic generation (SHG) imaging. The corneal laser welding procedure is performed by staining the wound edges with a saturated water solution of Indocyanine Green (ICG) followed by irradiation with a 810 nm diode laser operated in continuous (CWLW: continuous wave laser welding) or pulsed (PLW: pulsed laser welding) mode. Both these procedures can provide closure of corneal wounds by inducing different structural modifications in the extracellular matrix. SHG imaging of native corneal stroma revealed collagen bundles composed of many regularly aligned collagen fibrils. After CWLW the regular lamellar arrangement was lost; collagen bundles appeared densely packed with an increasing disordered arrangement toward the welded cut. The weld was characterized by a loss of details; nevertheless, the observation of the second harmonic signal at this site indicated the lack of collagen denaturation. By contrast, PLW mode produced welding spots at the interface between donor and recipient corneal layers, which were characterized by a severe loss of the SHG signal, suggesting the occurrence of a complete collagen denaturation. SHG imaging appeared to be a powerful tool for visualizing the supramolecular morphological modifications in the collagen matrix after laser welding.

Impact of corneal cross-linking combined with photorefractive keratectomy on blurring strength

OpenAIRE

Labiris, Georgios; Sideroudi, Haris; Angelonias, Dimitris; Georgantzoglou, Kimonas; Kozobolis, Vassilios P

2016-01-01

Georgios Labiris,1,2 Haris Sideroudi,2 Dimitris Angelonias,2 Kimonas Georgantzoglou,2 Vassilios P Kozobolis1,21Department of Ophthalmology, University Hospital of Alexandroupolis, 2Eye Institute of Thrace, Alexandroupolis, GreecePurpose: The aim of this study was to evaluate the impact of corneal cross-linking combined with photorefractive keratectomy (PRK) on blurring strength.Methods: A total of 63 patients with keratoconus were recruited for this study, and two study groups were formed acc...

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).

Science.gov (United States)

Kanellopoulos, Anastasios John

2012-01-01

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. 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. 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. 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.

5-year follow-up of combined non-topography guided photorefractive keratectomy and corneal collagen cross linking for keratoconus

Directory of Open Access Journals (Sweden)

Abdulrahman Mohammed Al-Amri

2018-01-01

Full Text Available AIM: To evaluate the visual outcomes of simultaneous non-topography guided photorefractive keratectomy (PRK and corneal collagen cross-linking (CXL in eyes with keratoconus 5y after the procedure. METHODS: Prospective, interventional, non-randomized, and non-controlled case series design was used. Sixty eyes of 30 patients (16 males and 14 females; age: 21-41y with mild, non-progressive (stages 1-2 keratoconus were enrolled. Refraction, uncorrected distance visual acuity (UDVA and corrected distance visual acuity (CDVA , flat and steep keratometry readings, and adverse events were evaluated preoperatively and postoperatively. Data were collected preoperatively and postoperatively at 3mo, 1, 2, 3, 4, and 5y follow-up visits after combined non-topography-guided PRK with CXL was performed. All patients had at least 5y of follow-up. RESULTS: All study parameters showed a statistically significant improvement at 5y over baseline values. The mean follow-up time was 68.20±4.71mo (range: 60-106mo. Patients showed a significant improvement in UDVA from 1.24±0.79 logMAR prior to combined non-TG-PRK+CXL to 0.06±0.15 logMAR postoperatively at the time of their last follow-up visit. CDVA significantly increased from 0.06±0.19 logMAR preoperatively to 0.03±0.12 logMAR postoperatively. A significant decrease in the mean spherical equivalent (SE refraction was observed from -2.28±1.8 to -0.79±0.93 diopters (D (P<0.05, and the manifest sphere decreased from -1.62±1.23 to -0.27±0.21 D (P=0.001. The manifest cylinder significantly decreased from -1.73±0.86 to -0.29±0.34 D postoperatively (P=0.001. The mean steep keratometry was 45.13±1.32 vs 47.28±2.12 D preoperatively (P<0.05, and the preoperative mean steepest keratometry (Kmax 48.6±3.1 was reduced significantly to 46.8±2.9 postoperatively (P<0.05. CONCLUSION: Combined non-TG-PRK with 15min CXL is an effective and safe option for correcting mild refractive error and improving visual acuity in

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

were higher in OM than in YM (73 +/- 13 vs. 11 +/- 2 mmol/mol; P appreciably influence the dimensions or mechanical properties of the human patellar tendon in vivo. Collagen concentration was reduced, whereas both enzymatic......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...

Engineering of Corneal Tissue through an Aligned PVA/Collagen Composite Nanofibrous Electrospun Scaffold.

Science.gov (United States)

Wu, Zhengjie; Kong, Bin; Liu, Rui; Sun, Wei; Mi, Shengli

2018-02-24

Corneal diseases are the main reason of vision loss globally. Constructing a corneal equivalent which has a similar strength and transparency with the native cornea, seems to be a feasible way to solve the shortage of donated cornea. Electrospun collagen scaffolds are often fabricated and used as a tissue-engineered cornea, but the main drawback of poor mechanical properties make it unable to meet the requirement for surgery suture, which limits its clinical applications to a large extent. Aligned polyvinyl acetate (PVA)/collagen (PVA-COL) scaffolds were electrospun by mixing collagen and PVA to reinforce the mechanical strength of the collagen electrospun scaffold. Human keratocytes (HKs) and human corneal epithelial cells (HCECs) inoculated on aligned and random PVA-COL electrospun scaffolds adhered and proliferated well, and the aligned nanofibers induced orderly HK growth, indicating that the designed PVA-COL composite nanofibrous electrospun scaffold is suitable for application in tissue-engineered cornea.

Effect of the Regenerative Agent Poly(Carboxymethylglucose Sulfate) on Corneal Wound Healing After Corneal Cross-Linking for Keratoconus.

Science.gov (United States)

Kymionis, George D; Liakopoulos, Dimitrios A; Grentzelos, Michael A; Tsoulnaras, Konstantinos I; Detorakis, Efstathios T; Cochener, Béatrice; Tsilimbaris, Miltiadis K

2015-08-01

To evaluate the effect of a regenerative agent (RGTA) [Cacicol20-poly(carboxymethyl glucose sulfate); OTR3, Paris, France] on corneal reepithelialization and pain after corneal cross-linking (CXL) for keratoconus. In this prospective comparative (contralateral) clinical study, patients with bilateral progressive keratoconus underwent CXL treatment. The corneal epithelium during CXL was removed using transepithelial phototherapeutic keratectomy (Cretan protocol). One eye of each patient was randomly instilled with an RGTA (Cacicol20) once a day (study group), whereas the fellow eye was instilled with artificial tears (control group). Patients were examined daily until complete reepithelialization. Postoperative examinations included slit-lamp biomicroscopy to assess the epithelial defect size and subjective evaluation of pain. The study enrolled 18 patients (36 eyes). The mean epithelial defect size for study and control groups was 19.6 ± 4.2 mm versus 21.5 ± 2.8 mm, respectively, at day 1 (P = 0.019) and 6.4 ± 3.4 mm versus 7.9 ± 4.3 mm, respectively, at day 2 (P = 0.014). At day 3 postoperatively, 61.1% of study eyes were fully reepithelialized, compared with 11.1% of control eyes (P = 0.002). RGTA (Cacicol20) instillation seems to result in faster corneal reepithelialization after CXL in this study. However, there was no significant effect in subjective pain/discomfort.

Modification of mature non-reducible collagen cross-link concentrations in bovine m. gluteus medius and semitendinosus with steer age at slaughter, breed cross and growth promotants.

Science.gov (United States)

Roy, B C; Sedgewick, G; Aalhus, J L; Basarab, J A; Bruce, H L

2015-12-01

Increased meat toughness with animal age has been attributed to mature trivalent collagen cross-link formation. Intramuscular trivalent collagen cross-link content may be decreased by reducing animal age at slaughter and/or inducing muscle re-modeling with growth promotants. This hypothesis was tested in m. gluteus medius (GM) and m. semitendinosus (ST) from 112 beef steers finished at either 12 to 13 (rapid growth) or 18 to 20 (slow growth) months of age. Hereford-Aberdeen Angus (HAA) or Charolais-Red Angus (CRA) steers were randomly assigned to receive implants (IMP), ractopamine (RAC), both IMP and RAC, or none (control). RAC decreased pyridinoline (mol/mol collagen) and IMP increased Ehrlich chromogen (EC) (mol/mol collagen) in the GM. In the ST, RAC increased EC (mol/mol collagen) but decreased EC (nmol/g raw muscle) in slow growing CRA steers. Also, IMP increased ST pyridinoline (nmol/g raw muscle) of slow-growing HAA steers. Results indicated alteration of perimysium collagen cross-links content in muscle in response to growth promotants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Automated Detection and Classification of Corneal Haze Using Optical Coherence Tomography in Patients With Keratoconus After Cross-Linking.

Science.gov (United States)

Dhaini, Ahmad R; Abdul Fattah, Maamoun; El-Oud, Sara Maria; Awwad, Shady T

2018-03-13

To evaluate a proposed technology for offering objective grading and mapping of corneal haze as detected by corneal spectral domain optical coherence tomography after corneal cross-linking. This was a retrospective study to evaluate corneal optical coherence tomography images performed on 44 eyes of 44 patients who underwent corneal cross-linking between January 2014 and May 2015, at the American University of Beirut Medical Center. Overall average brightness of the cornea was markedly increased from 43.4% (±6.0) at baseline to 50.2% (±4.4) at 1 month, 47.9% (±4.4) at 3 months, and 46.4% (±5.7) at 6 months with P <0.001, <0.001, and 0.005, respectively. In the anterior stroma, the average brightness significantly increased at 1, 3, and 6 months with values of 54.8% (±3.9), 52.5% (±5.2), and 49.7% (±6.9) with P <0.001, <0.001, and 0.003, respectively. In the mid stroma, the change was clinically significant at 1 and 3 months, whereas in the posterior stroma, it was only significant at 1 month compared with baseline (P = 0.003). Overall, haze was mostly present at 1 month after surgery in all regions, especially in the anterior (32.1%; ±19.2) and mid stromal regions (9.1%; ±18.8), P <0.001 and 0.001, respectively. In contrast, haze in the posterior stromal region peaks at 3 and 6 months after surgery. Anterior stromal haze was the greatest in intensity and area and it was present for a longer time span than mid and posterior stromal haze. At 12 months, the anterior stroma had still more haze intensity than preoperatively. This image-based software can provide objective and valuable quantitative measurements of corneal haze, which may impact clinical decision-making after different corneal surgeries.

Cross-Linking GPVI-Fc by Anti-Fc Antibodies Potentiates Its Inhibition of Atherosclerotic Plaque- and Collagen-Induced Platelet Activation

Directory of Open Access Journals (Sweden)

Janina Jamasbi, RPh

2016-04-01

Full Text Available To enhance the antithrombotic properties of recombinant glycoprotein VI fragment crystallizable (GPVI-Fc, the authors incubated GPVI-Fc with anti-human Fc antibodies to cross-link the Fc tails of GPVI-Fc. Cross-linking potentiated the inhibition of human plaque- and collagen-induced platelet aggregation by GPVI-Fc under static and flow conditions without increasing bleeding time in vitro. Cross-linking with anti-human-Fc Fab2 was even superior to anti-human-Fc immunoglobulin G (IgG. Advanced optical imaging revealed a continuous sheath-like coverage of collagen fibers by cross-linked GPVI-Fc complexes. Cross-linking of GPVI into oligomeric complexes provides a new, highly effective, and probably safe antithrombotic treatment as it suppresses platelet GPVI-plaque interaction selectively at the site of acute atherothrombosis.

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)

Abou Samra, Waleed Ali; 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 PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

Human Bone Derived Collagen for the Development of an Artificial Corneal Endothelial Graft. In Vivo Results in a Rabbit Model.

Directory of Open Access Journals (Sweden)

Natalia Vázquez

Full Text Available Corneal keratoplasty (penetrating or lamellar using cadaveric human tissue, is nowadays the main treatment for corneal endotelial dysfunctions. However, there is a worldwide shortage of donor corneas available for transplantation and about 53% of the world's population have no access to corneal transplantation. Generating a complete cornea by tissue engineering is still a tough goal, but an endothelial lamellar graft might be an easier task. In this study, we developed a tissue engineered corneal endothelium by culturing human corneal endothelial cells on a human purified type I collagen membrane. Human corneal endothelial cells were cultured from corneal rims after corneal penetrating keratoplasty and type I collagen was isolated from remnant cancellous bone chips. Isolated type I collagen was analyzed by western blot, liquid chromatography -mass spectrometry and quantified using the exponentially modified protein abundance index. Later on, collagen solution was casted at room temperature obtaining an optically transparent and mechanically manageable membrane that supports the growth of human and rabbit corneal endothelial cells which expressed characteristic markers of corneal endothelium: zonula ocluddens-1 and Na+/K+ ATPase. To evaluate the therapeutic efficiency of our artificial endothelial grafts, human purified type I collagen membranes cultured with rabbit corneal endothelial cells were transplanted in New Zealand white rabbits that were kept under a minimal immunosuppression regimen. Transplanted corneas maintained transparency for as long as 6 weeks without obvious edema or immune rejection and maintaining the same endothelial markers that in a healthy cornea. In conclusion, it is possible to develop an artificial human corneal endothelial graft using remnant tissues that are not employed in transplant procedures. This artificial endothelial graft can restore the integrality of corneal endothelium in an experimental model of

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.

Role of Decorin Core Protein in Collagen Organisation in Congenital Stromal Corneal Dystrophy (CSCD.

Directory of Open Access Journals (Sweden)

Christina S Kamma-Lorger

Full Text Available The role of Decorin in organising the extracellular matrix was examined in normal human corneas and in corneas from patients with Congenital Stromal Corneal Dystrophy (CSCD. In CSCD, corneal clouding occurs due to a truncating mutation (c.967delT in the decorin (DCN gene. Normal human Decorin protein and the truncated one were reconstructed in silico using homology modelling techniques to explore structural changes in the diseased protein. Corneal CSCD specimens were also examined using 3-D electron tomography and Small Angle X-ray diffraction (SAXS, to image the collagen-proteoglycan arrangement and to quantify fibrillar diameters, respectively. Homology modelling showed that truncated Decorin had a different spatial geometry to the normal one, with the truncation removing a major part of the site that interacts with collagen, compromising its ability to bind effectively. Electron tomography showed regions of abnormal stroma, where collagen fibrils came together to form thicker fibrillar structures, showing that Decorin plays a key role in the maintenance of the order in the normal corneal extracellular matrix. Average diameter of individual fibrils throughout the thickness of the cornea however remained normal.

Technical advances in the sectioning of dental tissue and of on-section cross-linked collagen detection in mineralized teeth.

Science.gov (United States)

Singhrao, Sim K; Sloan, Alastair J; Smith, Emma L; Archer, Charles W

2010-08-01

Immunohistochemical detection of cross-linked fibrillar collagens in mineralized tissues is much desired for exploring the mechanisms of biomineralization in health and disease. Mineralized teeth are impossible to section when embedded in conventional media, thus limiting on-section characterization of matrix proteins by immunohistochemistry. We hypothesized that by using an especially formulated acrylic resin suitable for mineralized dental tissues, not only sectioning of teeth would be possible, but also our recently developed immunofluorescence labeling technique would be amenable to fully calcified tissues for characterization of dentinal fibrillar collagens, which remains elusive. The hypothesis was tested on fixed rodent teeth embedded in Technovit 9100 New. It was possible to cut thin (1 mum) sections of mineralized teeth, and immunofluorescence characterization of cross-linked type I fibrillar collagen was selected due to its abundance in dentine. Decalcified samples of teeth embedded in paraffin wax were also used to compare immunolabeling from either method using the same immunoreagents in equivalent concentrations. In the decalcified tissue sections, type I collagen labeling in the dentine along the tubules was "patchy" and the signal in the predentine was very weak. However, enhanced signal in mineralized samples with type I collagen was detected not only in the predentine but also at the limit between intertubular dentine, within the elements of the enamel organ and subgingival stroma. This report offers advances in sectioning mineralized dental tissues and allows the application of immunofluorescence not only for on-section protein detection but importantly for detecting cross-linked fibrous collagens in both soft and mineralized tissue sections.

[Dynamics of riboflavin level in aqueous humour of anterior chamber of experimental animals under standard stroma saturation by ultraviolet corneal cross-linking solutions].

Science.gov (United States)

Bikbov, M M; Shevchuk, N E; Khalimov, A R; Bikbova, G M

To evaluate the dynamics of riboflavin changes in the aqueous humour of the anterior chamber (AHAC) of rabbits' eyes during standard ultraviolet (UV) cross-linking with account to the area of corneal debridement. Forty two rabbits were studied sequentially. The following solutions of riboflavin were used for cornea saturation: IR - 0.1% isosmotic riboflavin, D - Dextralink (0.1% riboflavin with 20% dextran), R - 0.1% riboflavin with 1.0% hydroxypropylmethylcellulose (HPMC). Each solution was evaluated in 3 groups that differed in the diameter of corneal debridement: group 1 - Epi-Off 3 mm (IR-3, D-3, P-3), group 2 - Epi-Off 6 mm (IR-6, D-6, R-6), and group 3 - Epi-Off 9 mm (IR-9, D-9, R-9). Aqueous humour sampling (252 samples in total) was performed in 10-minute intervals within a 60 minute period. Riboflavin levels were measured by enzyme-linked immunoassay (ID-Vit microbiological test system; Immundiagnostik, Germany). Stable growth rates of riboflavin level in the AHAC (with maximum values reached at 30-40 min) were observed for solutions D and R, regardless of the variant of corneal debridement. Moreover, throughout the whole follow-up period and regardless of the area of corneal debridement, the solution D provided a relatively lower concentration of riboflavin in the AHAC as compared to the two other solutions. At 30 minutes, when the cornea was considered ready for UV irradiation, the riboflavin level in the AHAC ranged from 385±26.1 μg/l (D-9) to 665±28 μg/l (R-9). In groups IR-9, IR-6, P-6, IR-3, and P-3 riboflavin levels were found to be in the same range starting at 20 minutes. However, even a sufficient concentration of riboflavin in the cornea or AHAC cannot guarantee safe and effective UV cross-linking, since the removed epithelium limits the area of the stroma that can be saturated with riboflavin, while the area of UV exposure is 8-10 mm. Safe and efficient standard UV cross-linking may be performed only under sufficient saturation of the

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

Microscopic characterization of collagen modifications induced by low-temperature diode-laser welding of corneal tissue.

Science.gov (United States)

Matteini, Paolo; Rossi, Francesca; Menabuoni, Luca; Pini, Roberto

2007-08-01

Laser welding of corneal tissue that employs diode lasers (810 nm) at low power densities (12-20 W/cm(2)) in association with Indocyanine Green staining of the wound is a technique proposed as an alternative to conventional suturing procedures. The aim of this study is to evaluate, by means of light (LM) and transmission electron microscopy (TEM) analyses, the structural modifications induced in laser-welded corneal stroma. Experiments were carried out in 20 freshly enucleated pig eyes. A 3.5 mm in length full-thickness cut was produced in the cornea, and was then closed by laser welding. Birefringence modifications in samples stained with picrosirius red dye were analyzed by polarized LM to assess heat damage. TEM analysis was performed on ultra-thin slices, contrasted with uranyl acetate and lead citrate, in order to assess organization and size of type I collagen fibrils after laser welding. LM evidenced bridges of collagen bundles between the wound edges, with a loss of regular lamellar organization at the welded site. Polarized LM indicated that birefringence properties were mostly preserved after laser treatment. TEM examinations revealed the presence of quasi-ordered groups of fibrils across the wound edges preserving their interfibrillar spacing. These fibrils appeared morphologically comparable to those in the control tissue, indicating that type I collagen was not denatured during the diode laser corneal welding. The preservation of substantially intact, undenatured collagen fibrils in laser-welded corneal wounds supported the thermodynamic studies that we carried out recently, which indicated temperatures below 66 degrees C at the weld site under laser irradiation. This observation enabled us to hypothesize that the mechanism, proposed in the literature, of unwinding of collagen triple helixes followed by fibrils "interdigitation" is not likely to occur in the welding process that we set up for the corneal suturing.

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

Directory of Open Access Journals (Sweden)

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

Transepithelial Riboflavin Absorption in an Ex Vivo Rabbit Corneal Model.

Science.gov (United States)

Gore, Daniel M; O'Brart, David; French, Paul; Dunsby, Chris; Allan, Bruce D

2015-07-01

To measure depth-specific riboflavin concentrations in corneal stroma using two-photon fluorescence microscopy and compare commercially available transepithelial corneal collagen cross-linking (CXL) protocols. Transepithelial CXL riboflavin preparations--MedioCross TE, Ribocross TE, Paracel plus VibeX Xtra, and iontophoresis with Ricrolin+--were applied to the corneal surface of fresh postmortem rabbit eyes in accordance with manufacturers' recommendations for clinical use. Riboflavin 0.1% (VibeX Rapid) was applied after corneal epithelial debridement as a positive control. After riboflavin application, eyes were snap frozen in liquid nitrogen. Corneal cross sections 35-μm thick were cut on a cryostat, mounted on a slide, and imaged by two-photon fluorescence microscopy. Mean (SD) concentrations were calculated from five globes tested for each protocol. Peak riboflavin concentration of 0.09% (± 0.01) was observed within the most superficial stroma (stromal depth 0-10 μm) in positive controls (epithelium-off). At the same depth, peak stromal riboflavin concentrations for MedioCross TE, Ricrolin+, Paracel/Xtra, and Ribocross TE were 0.054% (± 0.01), 0.031% (0.003), 0.021% (± 0.001), and 0.015% (± 0.004), respectively. At a depth of 300 μm (within the demarcation zone commonly seen after corneal cross-linking), the stromal concentration in epithelium-off positive controls was 0.075% (± 0.006), while at the same depth MedioCross TE and Ricrolin+ achieved 0.018% (± 0.006) and 0.016% (0.002), respectively. None of the remaining transepithelial protocols achieved concentrations above 0.005% at this same 300-μm depth. Overall, MedioCross TE was the best-performing transepithelial formulation. Corneal epithelium is a significant barrier to riboflavin absorption into the stroma. Existing commercial transepithelial CXL protocols achieve relatively low riboflavin concentrations in the anterior corneal stroma when compared to gold standard epithelium-off absorption

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

International Nuclear Information System (INIS)

Liu, Yang; Ren, Li; Wang, Yingjun

2014-01-01

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

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.

Comparison of sequential vs same-day simultaneous collagen cross-linking and topography-guided PRK for treatment of keratoconus.

Science.gov (United States)

Kanellopoulos, Anastasios John

2009-09-01

The safety and efficacy of corneal collagen cross-linking (CXL) and topography-guided photorefractive keratectomy (PRK) using a different sequence and timing were evaluated in consecutive keratoconus cases. This study included a total of 325 eyes with keratoconus. Eyes were divided into two groups. The first group (n=127 eyes) underwent CXL with subsequent topography-guided PRK performed 6 months later (sequential group) and the second group (n=198 eyes) underwent CXL and PRK in a combined procedure on the same day (simultaneous group). Statistical differences were examined for pre- to postoperative changes in uncorrected (UCVA, logMAR) and best-spectacle-corrected visual acuity (BSCVA, logMAR), manifest refraction spherical equivalent (MRSE), keratometry (K), topography, central corneal thickness, endothelial cell count, corneal haze, and ectatic progression. Mean follow-up was 36+/-18 months (range: 24 to 68 months). At last follow-up in the sequential group, the mean UCVA improved from 0.9+/-0.3 logMAR to 0.49+/-0.25 logMAR, and mean BSCVA from 0.41+/-0.25 logMAR to 0.16+/-0.22 logMAR. Mean reduction in spherical equivalent refraction was 2.50+/-1.20 diopters (D), mean haze score was 1.2+/-0.5, and mean reduction in K was 2.75+/-1.30 D. In the simultaneous group, mean UCVA improved from 0.96+/-0.2 logMAR to 0.3+/-0.2 logMAR, and mean BSCVA from 0.39+/-0.3 logMAR to 0.11+/-0.16 logMAR. Mean reduction in spherical equivalent refraction was 3.20+/-1.40 D, mean haze score was 0.5+/-0.3, and mean reduction in K was 3.50+/-1.3 D. Endothelial cell count preoperatively and at last follow-up was unchanged (PPRK and CXL appears to be superior to sequential CXL with later PRK in the visual rehabilitation of progressing keratoconus. Copyright 2009, SLACK Incorporated.

[The status quo and expectation of corneal research in China].

Science.gov (United States)

Shi, Weiyun; Xie, Lixin

2014-09-01

In China, corneal disease is currently the second leading cause of blindness. Severe donor shortage, insufficient technique supports and promotion, and the lack of corneal disease specialists due to poor systematic training are all urgent problems to be resolved. The last 5 years have witnessed a considerable progress in basic and clinical researches of corneal disease. Investigations on the pathogenesis and treatment of fungal keratitis have won an international reputation. Results from the study of corneal reconstruction with tissue-engineered and acellular matrix corneas have been tested in clinical trials with good preliminary performance. Moreover, the clinical researches of corneal refractive surgery have kept pace with the latest international progresses. However, Descemet's membrane endothelial keratoplasty needs further promotion, and the development and application of keratoprosthesis remains a blank. Although keratoprosthesis and corneal collagen cross-linking have been widely applied in Europe with satisfactory clinical efficacy, they are still under assessment by China Food and Drug Administration for approval of use.

Effect of pore size and cross-linking of a novel collagen-elastin dermal substitute on wound healing

NARCIS (Netherlands)

Boekema, B.K.H.L.; Vlig, M.; Damink, L.O.; Middelkoop, E.; Eummelen, L.; Buhren, A.V.; Ulrich, M.M.W.

2014-01-01

Collagen-elastin (CE) scaffolds are frequently used for dermal replacement in the treatment of full-thickness skin defects such as burn wounds. But little is known about the optimal pore size and level of cross-linking. Different formulations of dermal substitutes with unidirectional pores were

Confocal microscopy evaluation of stromal fluorescence intensity after standard and accelerated iontophoresis-assisted corneal cross-linking.

Science.gov (United States)

Lanzini, Manuela; Curcio, Claudia; Spoerl, Eberhard; Calienno, Roberta; Mastropasqua, Alessandra; Colasante, Martina; Mastropasqua, Rodolfo; Nubile, Mario; Mastropasqua, Leonardo

2017-02-01

The aim of this study is to determine modifications in stromal fluorescence intensity after different corneal cross-linking (CXL) procedures and to correlate stromal fluorescence to corneal biomechanical resistance. For confocal microscopy study, 15 human cadaver corneas were examined. Three served as control (group 1), three were just soaked with iontophoresis procedure (group 2), three were treated with standard epi-off technique (group 3), and six underwent iontophoresis imbibition. Three of later six were irradiated for 30 min with 3 mW/cm 2 UVA (group 4) and three for 9 min at 10 mW/cm 2 UVA (group 5). Confocal microscopy was performed to quantify the fluorescence intensity in the cornea at different stromal depths. For biomechanical study, 30 human cadaver corneas were randomly divided into five groups and treated as previously described. Static stress-strain measurements of the corneas were performed. Iontophoresis imbibition followed by 10mW/cm 2 irradiation proved to increase stromal fluorescence into the corneal stroma and significant differences were revealed between group 3 and 5 both at 100 (p = 0.0171) and 250 µm (p = 0.0024), respectively. Biomechanical analysis showed an improvement of corneal resistance in group 5. Iontophoresis imbibition followed by accelerated irradiation increased the stromal fluorescence and is related to an improvement of biomechanical resistance. This approach may represent a new strategy to achieve greater concentrations of riboflavin without removing corneal epithelium and improve clinical results while reducing the side effects of CXL.

Evaluation of Biomechanical Changes in Myopia Patients with Unsatisfactory Corneas After Femto Second-Laser In Situ Keratomileusis (FS-LASIK) Concurrent with Accelerated Corneal Collagen Cross-Linking Using Corvis-ST: Two-Year Follow-Up Results.

Science.gov (United States)

Xu, Weiwei; Tao, Ye; Wang, Liqiang; Huang, Yifei

2017-07-27

BACKGROUND Some myopia patients with unsatisfactory corneas consider corneal refractive surgery for different reasons. Accelerated corneal collagen crosslinking (ACXL) is an effective method to enhance the resistance of the cornea. The present investigation was designed to evaluate the changes of biomechanical properties in patients with myopia and thin corneas after femtosecond-laser in situ keratomileusis (FS-LASIK) concurrent with ACXL. MATERIAL AND METHODS A prospective study was designed. A total of 22 eyes of 11 myopia astigmatism patients with unsatisfactory corneas were enrolled. The patients were assigned to femtosecond-laser in situ keratomileusis concurrent with accelerated corneal collagen crosslinking (FS-LASIK-ACXL). The follow-up duration was 24 months. Manifest refraction, uncorrected (UDVA), and corrected distance visual acuity (CDVA), ultra-high-speed camera (Corvis-ST), corneal topography, anterior segment OCT (AS-OCT), Pentacam, and endothelial cell density (ECD) were examined before and after the operation. The corneal biomechanical and refractive data was analyzed using SAS9.3. Data were analyzed through normal distribution test and variance of analysis. The difference was considered as statistically significant when pLASIK-ACXL operation. The values of first applanation length (A1L), the second applanation length (A2L), the first applanation velocity (A1V), the second applanation velocity (A2V), deformation amplitude (DA), highest concavity peak distance (PD), and radius of curvature at the time of highest concavity (HCR) did not show significant difference after the operation. CONCLUSIONS FS-LASIK-ACXL is an effective and safe surgery for improving visual acuity for myopic patients with thin corneas, and it does not increase the risk of iatrogenic keratectasia.

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

Plastic compressed collagen as a novel carrier for expanded human corneal endothelial cells for transplantation.

Directory of Open Access Journals (Sweden)

Hannah J Levis

Full Text Available Current treatments for reversible blindness caused by corneal endothelial cell failure involve replacing the failed endothelium with donor tissue using a one donor-one recipient strategy. Due to the increasing pressure of a worldwide donor cornea shortage there has been considerable interest in developing alternative strategies to treat endothelial disorders using expanded cell replacement therapy. Protocols have been developed which allow successful expansion of endothelial cells in vitro but this approach requires a supporting material that would allow easy transfer of cells to the recipient. We describe the first use of plastic compressed collagen as a highly effective, novel carrier for human corneal endothelial cells. A human corneal endothelial cell line and primary human corneal endothelial cells retained their characteristic cobblestone morphology and expression of tight junction protein ZO-1 and pump protein Na+/K+ ATPase α1 after culture on collagen constructs for up to 14 days. Additionally, ultrastructural analysis suggested a well-integrated endothelial layer with tightly opposed cells and apical microvilli. Plastic compressed collagen is a superior biomaterial in terms of its speed and ease of production and its ability to be manipulated in a clinically relevant manner without breakage. This method provides expanded endothelial cells with a substrate that could be suitable for transplantation allowing one donor cornea to potentially treat multiple patients.

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.

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

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

Directory of Open Access Journals (Sweden)

Waleed Ali Abou Samra

2016-01-01

Full Text Available 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<0.001. A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions. WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.

Chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines formed by cross-link of bone and synovium collagen.

Science.gov (United States)

Anastasia, Luigi; Rota, Paola; Anastasia, Mario; Allevi, Pietro

2013-09-21

This review focuses on the chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines (Pyds), fluorescent collagen cross-links, with a pyridinium salt structure. Pyds derive from the degradation of bone collagen and have attracted attention for their use as biochemical markers of bone resorption and to assess fracture risk prediction in persons suffering from osteoporosis, bone cancer and other bone or collagen diseases. We consider and critically discuss all reported syntheses of free and glycosylated Pyds evidencing an unrevised chemistry, original and of general utility, analysis of which allows us to also support a previously suggested non-enzymatic formation of Pyds in collagen better rationalizing and justifying the chemical events.

Collagen VII deficient mice show morphologic and histologic corneal changes that phenotypically mimic human dystrophic epidermolysis bullosa of the eye.

Science.gov (United States)

Chen, Vicki M; Shelke, Rajani; Nyström, Alexander; Laver, Nora; Sampson, James F; Zhiyi, Cao; Bhat, Najma; Panjwani, Noorjahan

2018-06-16

Absence of collagen VII causes blistering of the skin, eyes and many other tissues. This disease is termed dystrophic epidermolysis bullosa (DEB). Corneal fibrosis occurs in up to 41% and vision loss in up to 64% of patients. Standard treatments are supportive and there is no cure. The immune-histologic and morphologic changes in the corneas of the mouse model for this disease have not been described in the literature. Our purpose is to characterize the eyes of these mice to determine if this is an appropriate model for study of human therapeutics. Western blot analysis (WB) and immunohistochemistry (IHC) were performed to assess the relative collagen VII protein levels and its location within the cornea. Additional IHC for inflammatory and fibrotic biomarkers alpha-smooth muscle actin (α-SMA), transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), proteinase 3, tenascin C and collagen III were performed. Clinical photographs documenting opacification of the corneas of animals of differing ages were assessed and scored independently by 2 examiners. Histology was then used to investigate morphologic changes. IHC and WB confirmed that these mice are deficient in collagen VII production at the level of the basement membrane when compared with wild-types. IHC showed anomalous deposition of collagen III throughout the stroma. Of the 5 biomarkers tested, TGF-β showed the strongest and most consistently staining. Photographs documented corneal opacities only in mice older than 10 weeks, opacities were not seen in younger animals. Histology showed multiple abnormalities, including epithelial hyperplasia, ulceration, fibrosis, edema, dysplasia, neovascularization and bullae formation. The collagen VII hypomorphic mouse shows reduced collagen VII production at the level of the corneal basement membrane. Corneal changes are similar to pathology seen in humans with this disease. The presence of anomalous stromal collagen III and TGF-β appear to be

Cross-Linking in Collagen by Nonenzymatic Glycation Increases the Matrix Stiffness in Rabbit Achilles Tendon

OpenAIRE

Reddy, G. Kesava

2004-01-01

Nonenzymatic glycation of connective tissue matrix proteins is a major contributor to the pathology of diabetes and aging. Previously the author and colleagues have shown that nonenzymatic glycation significantly enhances the matrix stability in the Achilles tendon (Reddy et al., 2002, Arch. Biochem. Biophys., 399, 174–180). The present study was designed to gain further insight into glycation-induced collagen cross-linking and its relationship to matrix stiffness in the rabbit Achilles tendo...

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

Directory of Open Access Journals (Sweden)

Craig Boote

Full Text Available To quantify long-term changes in stromal collagen ultrastructure following penetrating keratoplasty (PK, and evaluate their possible implications for corneal biomechanics.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.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.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-host interface in the long term.

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

Effect of pore size and cross-linking of a novel collagen-elastin dermal substitute on wound healing.

Science.gov (United States)

Boekema, Bouke K H L; Vlig, Marcel; Olde Damink, Leon; Middelkoop, Esther; Eummelen, Lizette; Bühren, Anne V; Ulrich, Magda M W

2014-02-01

Collagen-elastin (CE) scaffolds are frequently used for dermal replacement in the treatment of full-thickness skin defects such as burn wounds. But little is known about the optimal pore size and level of cross-linking. Different formulations of dermal substitutes with unidirectional pores were tested in porcine full-thickness wounds in combination with autologous split skin mesh grafts (SSG). Effect on wound healing was evaluated both macro- and microscopically. CE scaffolds with a pore size of 80 or 100 μm resulted in good wound healing after one-stage grafting. Application of scaffolds with a larger average pore size (120 μm) resulted in more myofibroblasts and more foreign body giant cells (FBGC). Moderate crosslinking impaired wound healing as it resulted in more wound contraction, more FBGC and increased epidermal thickness compared to no cross-linking. In addition, take rate and redness were negatively affected compared to SSG only. Vascularization and the number of myofibroblasts were not affected by cross-linking. Surprisingly, stability of cross-linked scaffolds was not increased in the wound environment, in contrast to in vitro results. Cross-linking reduced the proliferation of fibroblasts in vitro, which might explain the reduced clinical outcome. The non-cross-linked CE substitute with unidirectional pores allowed one-stage grafting of SSG, resulting in good wound healing. In addition, only a very mild foreign body reaction was observed. Cross-linking of CE scaffolds negatively affected wound healing on several important parameters. The optimal non-cross-linked CE substitute is a promising candidate for future clinical evaluation.

Corneal Cross-Linking Has No Effect on Matrix Metalloproteinase 9 and 13 Levels During Fungal Keratitis on the Early Stage.

Science.gov (United States)

Kalkanci, Ayse; Bilgihan, Kamil; Ozdemir, Huseyin Baran; Yar Saglam, Atiye Seda; Karakurt, Funda; Erdogan, Merve

2018-04-01

The aim of our study was to investigate matrix metalloproteinases, MMP-9 and MMP-13 levels, in the rabbit model of Fusarium and Candida keratitis treated by corneal cross-linking (PACK-CXL). Rabbit corneas were inoculated with fungal inoculum for keratitis. Each group divided into four subgroups, including un-treated group, PACK-CXL group, voriconazole group and PACK-CXL plus voriconazole group. PACK-CXL was applied with 0.25% riboflavin in accelerated Dresden protocol, and 0.1% voriconazole drops were administered. All corneal buttons excised at tenth day after ophthalmological examination. Fungal cell counts and Scheiber scores were determined in all groups. Corneal tissue MMP mRNA levels were evaluated quantitative reverse transcriptase PCR. The difference in MMP-9 and MMP-13 levels at all groups was not statistically significant (p > 0.05). PACK-CXL with 0.25% riboflavin either alone or combined with antifungal drops was unable to provide decline in inflammatory findings in both macroscopic and microscopic levels similar to medical antifungal treatment.

Absence of FKBP10 in recessive type XI osteogenesis imperfecta leads to diminished collagen cross-linking and reduced collagen deposition in extracellular matrix.

Science.gov (United States)

Barnes, Aileen M; Cabral, Wayne A; Weis, MaryAnn; Makareeva, Elena; Mertz, Edward L; Leikin, Sergey; Eyre, David; Trujillo, Carlos; Marini, Joan C

2012-11-01

Recessive osteogenesis imperfecta (OI) is caused by defects in genes whose products interact with type I collagen for modification and/or folding. We identified a Palestinian pedigree with moderate and lethal forms of recessive OI caused by mutations in FKBP10 or PPIB, which encode endoplasmic reticulum resident chaperone/isomerases FKBP65 and CyPB, respectively. In one pedigree branch, both parents carry a deletion in PPIB (c.563_566delACAG), causing lethal type IX OI in their two children. In another branch, a child with moderate type XI OI has a homozygous FKBP10 mutation (c.1271_1272delCCinsA). Proband FKBP10 transcripts are 4% of control and FKBP65 protein is absent from proband cells. Proband collagen electrophoresis reveals slight band broadening, compatible with ≈10% over-modification. Normal chain incorporation, helix folding, and collagen T(m) support a minimal general collagen chaperone role for FKBP65. However, there is a dramatic decrease in collagen deposited in culture despite normal collagen secretion. Mass spectrometry reveals absence of hydroxylation of the collagen telopeptide lysine involved in cross-linking, suggesting that FKBP65 is required for lysyl hydroxylase activity or access to type I collagen telopeptide lysines, perhaps through its function as a peptidylprolyl isomerase. Proband collagen to organics ratio in matrix is approximately 30% of normal in Raman spectra. Immunofluorescence shows sparse, disorganized collagen fibrils in proband matrix. Published 2012 Wiley Periodicals, Inc.*This article is a US Government work and, as such, is in the public domain of the United States of America.

The spectra character of photodegraded the pyridinoline cross-links by Hypocrellin B

International Nuclear Information System (INIS)

Zhang Jucheng; Chen Rui; Liu Wei; Chen Zhuo; Shu Lidan; Liu Yingji

2011-01-01

Pyridinoline cross-links is one of the cross-link formation in collagen which in cell matrix, many research shown that this cross-link cause the fibrosis. Hypocrellin B (HB) is one of the nature photosensitizers, this work investigated the pyridinoline cross-link in collagen was photodegraded by HB. The result shown HB can degrade the pyridinoline cross-link with photo. This is to say, HB may be use as the photodynamic reagent to study the fibrosis.

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

Epithelium-on photorefractive intrastromal cross-linking (PiXL for reduction of low myopia

Directory of Open Access Journals (Sweden)

Lim WK

2017-06-01

Full Text Available Wee Kiak Lim,1,2 Zhi Da Soh,1 Harold Kah Yen Choi,1 Julian Thiam Siew Theng1,3 1Eagle Eye Centre, Mount Alvernia Hospital, 2Department of Ophthalmology, Tan Tock Seng Hospital, 3Department of Ophthalmology, Khoo Teck Puat Hospital, Singapore Purpose: To report the 9–12-month outcomes of a novel procedure for reduction of low myopia through epithelium-on photorefractive intrastromal cross-linking (PiXL with customized control of topographic distribution of ultraviolet (UV-fluence. Method: Myopic patients with normal (non-ectatic corneas underwent the PiXL procedure for reduction of low myopia. PiXL treatments were delivered through selective application of UVA light based on the refractive error of each patient. Clinical evaluation included safety (corrected distance visual acuity, endothelial cell count, central corneal thickness, anterior ocular health and efficacy (uncorrected distance visual acuity, manifest refraction, K-mean examinations. In addition, a patient satisfaction survey was conducted at 9 months post-procedure to evaluate patients’ subjective experience with the procedure. Results: Fourteen myopic eyes (mean manifest refraction spherical equivalent –1.62±0.6D; range –0.75 to –2.65D of 8 subjects (mean age 30 years old; range 24–51 years old were enrolled in the study. At 12 months post-procedure, a mean manifest refraction spherical equivalent reduction of 0.72±0.43D (P<0.001 was observed, with a corresponding gain in uncorrected visual acuity of 0.25 logMAR and mean K-mean flattening of 0.47±0.46D. All patients achieved best corrected visual acuity of 20/20 or better from 1 month onward. There were no cases of ocular infection or secondary changes to the crystalline lens and retina due to UV exposure, while transient corneal haze subsided gradually. Conclusion: The epithelium-on PiXL procedure was safe and effective in reducing myopic refractive error in this study with up to 12 months follow-up. Early results of

Characterization of elasticity and hydration of composite hydrogel based on collagen-iota carrageenan as a corneal tissue engineering

Science.gov (United States)

Rinawati, M.; Triastuti, J.; Pursetyo, K. T.

2018-04-01

The cornea is a refractive element of the eye that serves to continue the stimulation of light into the eye it has a clear, transparent, elastic and relatively thick tissue. Factors caused corneal blindness, are dystrophy, keratoconus, corneal scaring. Hydrogels can be made from polysaccharide derivatives that have gelation properties such as iota carrageenan. Therefore, it is a need to develop composite hydrogel based collagen-iota carragenan as an engineeried corneal tissue with high elasticity and hydration properties. Collagen hydrogel has a maximum water content an has equlibrium up to 40 %, less than the human cornea, 81 % and under normal hydration conditions, the human cornea can transmit 87 % of visible light. In addition, the refractive index on the surface of the cornea with air is 1.375-1.380. Based on this study, it is necessary to conduct research on the development and composition of hydrogel composite collagen-iota carrageen hydrogen based on. The best result was K5 (5:5) treatment, which has the equilibrium water content of 87.07 % and viscosity of 10.7346 Pa.s.

Quantification of Collagen Ultrastructure after Penetrating Keratoplasty – Implications for Corneal Biomechanics

Science.gov (United States)

Gardner, Steven J.; Kamma-Lorger, Christina S.; Hayes, Sally; Nielsen, Kim; Hjortdal, Jesper; Sorensen, Thomas; Terrill, Nicholas J.; Meek, Keith M.

2013-01-01

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-host interface in the

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.

Preparation and characterization of malonic acid cross-linked chitosan and collagen 3D scaffolds: an approach on non-covalent interactions.

Science.gov (United States)

Mitra, Tapas; Sailakshmi, G; Gnanamani, A; Mandal, A B

2012-05-01

The present study emphasizes the influence of non-covalent interactions on the mechanical and thermal properties of the scaffolds of chitosan/collagen origin. Malonic acid (MA), a bifuncitonal diacid was chosen to offer non-covalent cross-linking. Three dimensional scaffolds was prepared using chitosan at 1.0% (w/v) and MA at 0.2% (w/v), similarly collagen 0.5% (w/v) and MA 0.2% (w/v) and characterized. Results on FT-IR, TGA, DSC, SEM and mechanical properties (tensile strength, stiffness, Young's modulus, etc.) assessment demonstrated the existence of non-covalent interaction between MA and chitosan/collagen, which offered flexibility and high strength to the scaffolds suitable for tissue engineering research. Studies using NIH 3T3 fibroblast cells suggested biocompatibility nature of the scaffolds. Docking simulation study further supports the intermolecular hydrogen bonding interactions between MA and chitosan/collagen.

Development of a human corneal epithelium model utilizing a collagen vitrigel membrane and the changes of its barrier function induced by exposing eye irritant chemicals.

Science.gov (United States)

Takezawa, Toshiaki; Nishikawa, Kazunori; Wang, Pi-Chao

2011-09-01

The brief TEER (trans-epithelial electrical resistance) assay after exposing chemicals to corneal epithelium in vivo is known as a suitable method for evaluating corneal irritancy and permeability quantitatively and continuously. A collagen vitrigel membrane we previously developed is a thin (about 20 μm thick) and transparent membrane composed of high density collagen fibrils equivalent to connective tissues in vivo, e.g. corneal Bowman's membrane. To develop such a TEER assay system in vitro utilizing a human corneal epithelial model, HCE-T cells (a human corneal epithelial cell line) were cultured on the collagen vitrigel membrane substratum prepared in a Millicell chamber suitable for TEER measurement. Human corneal epithelium model possessing 5-6 cell layers sufficient for TEER assay was successfully reconstructed on the substratum in the Millicell chamber by culturing the cells in monolayer for 2 days and subsequently in air-liquid interface for 7 days. The exposure of chemicals to the model induced the time-dependent relative changes of TEER in response to the characteristic of each chemical within a few minutes. These results suggest that the TEER assay using the human corneal epithelial model is very useful for an ocular irritancy evaluation as an alternative to the Draize eye irritation test. Copyright © 2011 Elsevier Ltd. All rights reserved.

A comparison study of Riboflavin/UV-A and Rose-Bengal/Green light cross-linking of the rabbit corneas using optical coherence elastography

Science.gov (United States)

Li, Jiasong; Singh, Manmohan; Han, Zhaolong; Vantipalli, Srilatha; Liu, Chih-Hao; Wu, Chen; Raghunathan, Raksha; Kazemi, Tina; Twa, Michael D.; Larin, Kirill V.

2016-03-01

The biomechanical properties of the cornea are critical factors which determine its health and subsequent visual acuity. Keratoconus is a structural degeneration of the cornea which can diminish vision quality. Riboflavin/UV-A corneal collagen cross-linking (UV-CXL) is an emerging treatment that increases the stiffness of the cornea and improves its ability to resist further degeneration. While UV-CXL has shown great promise for effective therapy of the keratoconus, there are concerns associated with the UV irradiation, such as keratocyte cytotoxicity. Rose-bengal/green light corneal collagen cross-linking (RGX) has been proposed as an alternative to UV-CXL. Because of the high absorbance of the rose-bengal dye at green wavelengths, the treatment time is significantly shorter than with UV-CXL. Moreover, because green light is used in lieu of UV irradiation, there are no cytotoxic side-effects. In this study, noncontact optical coherence elastography (OCE) was used to compare the outcomes of UV-CXL and RGX treatment in rabbit cornea. Low-amplitude (micrometer scale) elastic waves were induced by a focused air-pulse loading system. The elastic wave propagation was then imaged by a phase-stabilized swept source OCE (PhS-SSOCE) system. The changes in the viscoelasticity of the corneas were quantified by a previously developed modified Rayleigh Lamb frequency model. The depth-resolved micro-scale phase-velocity distribution in the cornea was used to reveal the depth-wise heterogeneity before and after both cross-linking techniques. Our results show that UV-CXL and RGX increased the stiffness of the corneas by ~54% and ~5% while reducing the viscosity by ~42% and ~17%, respectively. The depth-wise phase velocities showed that UV-CXL affected the anterior ~1/3 of the corneas, while RGX only affected the anterior ~1/7 of the corneas.

Fabrication of Collagen Gel Hollow Fibers by Covalent Cross-Linking for Construction of Bioengineering Renal Tubules.

Science.gov (United States)

Shen, Chong; Zhang, Guoliang; Wang, Qichen; Meng, Qin

2015-09-09

Collagen, the most used natural biomacromolecule, has been extensively utilized to make scaffolds for cell cultures in tissue engineering, but has never been fabricated into the configuration of a hollow fiber (HF) for cell culture due to its poor mechanical properties. In this study, renal tubular cell-laden collagen hollow fiber (Col HF) was fabricated by dissolving sacrificial Ca-alginate cores from collagen shells strengthened by carbodiimide cross-linking. The inner/outer diameters of the Col HF were precisely controlled by the flow rates of core alginate/shell collagen solution in the microfluidic device. As found, the renal tubular cells self-assembled into renal tubules with diameters of 50-200 μm post to the culture in Col HF for 10 days. According to the 3D reconstructed confocal images or HE staining, the renal cells appeared as a tight tubular monolayer on the Col HF inner surface, sustaining more 3D cell morphology than the cell layer on the 2D flat collagen gel surface. Moreover, compared with the cultures in either a Transwell or polymer HF membrane, the renal tubules in Col HF exhibited at least 1-fold higher activity on brush border enzymes of alkaline phosphatase and γ-glutamyltransferase, consistent with their gene expressions. The enhancement occurred similarly on multidrug resistance protein 2 and glucose uptake. Such bioengineered renal tubules in Col HF will present great potential as alternatives to synthetic HF in both clinical use and pharmaceutical investigation.

Evaluation of the shifting of the line of sight and higher order aberrations of eyes with keratoconus after corneal cross-linking.

Science.gov (United States)

Kosekahya, Pinar; Koc, Mustafa; Tekin, Kemal; Uzel, Murat; Atilgan, Cemile Ucgul; Caglayan, Mehtap; Yilmazbas, Pelin

2017-10-01

To evaluate changes in the coordinates of the line of sight (LoS) and higher order aberrations (HOAs) of eyes with keratoconus, following corneal cross-linking (CXL). All patients (93 eyes) underwent detailed ophthalmologic examination and Pentacam HR measurements at baseline and at 3, 6, and 12 months after corneal CXL. LoS coordinates on the horizontal (x) and vertical (y) axes, vertical coma, vertical trefoil, spherical aberration, total root-mean square (RMS), and HOA-RMS values were recorded along with visual acuity and topographical parameters. LoS significantly shifted to the nasal region after corneal CXL in both right and left eyes (p=0.003 and p=0.01, respectively). Horizontal axis values of both eyes significantly shifted to the temporal region at postoperative 6th months compared to the baseline measurements (p=0.02 and p=0.02, respectively) and remained the same between postoperative 6th months and 12th months (p=1.00 and p=0.97, respectively). Total-RMS, HOA-RMS, vertical coma, and spherical aberration values significantly improved after corneal CXL (pbaseline measurements (p=0.003, p=0.02, p0.05 for all values). The changes in horizontal-axis coordinates in left eyes were significantly correlated with anterior elevation, anterior astigmatism, total-RMS and HOA-RMS changes (r 2 =0.20, p=0.03; r 2 =0.35, pshifted to the nasal region and HOAs improved after corneal CXL and these changes stabilized 6th months after corneal CXL. It would be more better to perform refractive surgery in crosslinked corneas at least 6th months after corneal CXL. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Highly concentrated collagen solutions leading to transparent scaffolds of controlled three-dimensional organizations for corneal epithelial cell colonization.

Science.gov (United States)

Tidu, Aurélien; Ghoubay-Benallaoua, Djida; Teulon, Claire; Asnacios, Sophie; Grieve, Kate; Portier, François; Schanne-Klein, Marie-Claire; Borderie, Vincent; Mosser, Gervaise

2018-05-29

This study aimed at controlling both the organization and the transparency of dense collagen scaffolds making use of the lyotropic mesogen properties of collagen. Cholesteric or plywood-like liquid crystal phases were achieved using mixtures of acetic and hydrochloric acids as solvents. The critical pH at which the switch between the two phases occurred was around pH = 3. The use of the two acids led to fibrillated collagen I scaffolds, whose visual aspect ranged from opaque to transparent. Rheological investigations showed that viscoelastic properties of the plywood-like solutions were optimized for molding due to faster recovery. They also confirmed the correlation between the elastic modulus and the diameter of collagen fibrils obtained after fibrillogenesis under ammonia vapor. Human corneal epithelial cells, grown from donor limbal explants, were cultured both on transparent plywood-like matrices and on human amniotic membranes for 14 days. The development of corneal epithelium and the preservation of epithelial stem cells were checked by optical microscopy, colony formation assay, immuno-fluorescence and quantitative polymerase chain reaction. A higher level of amplification of limbal stem cells was obtained with collagen matrices compared with amniotic membranes, showing the high biocompatibility of our scaffolds. We therefore suggest that collagen solutions presenting both plywood-like organization and transparency might be of interest for biomedical applications in ophthalmology.

Topography-guided transepithelial PRK after intracorneal ring segments implantation and corneal collagen CXL in a three-step procedure for keratoconus.

Science.gov (United States)

Coskunseven, Efekan; Jankov, Mirko R; Grentzelos, Michael A; Plaka, Argyro D; Limnopoulou, Aliki N; Kymionis, George D

2013-01-01

To present the results of topography-guided transepithelial photorefractive keratectomy (PRK) after intracorneal ring segments implantation followed by corneal collagen cross-linking (CXL) for keratoconus. In this prospective case series, 10 patients (16 eyes) with progressive keratoconus were included. All patients underwent topography-guided transepithelial PRK after Keraring intracorneal ring segments (Mediphacos Ltda) implantation, followed by CXL treatment. The follow-up period was 6 months after the last procedure for all patients. Time interval between both intracorneal ring segments implantation and CXL and between CXL and topography-guided transepithelial PRK was 6 months. LogMAR mean uncorrected distance visual acuity and mean corrected distance visual acuity were significantly improved (PPRK with intracorneal ring segments implantation and CXL in a three-step procedure seems to be an effective, promising treatment sequence offering patients a functional visual acuity and ceasing progression of the ectatic disorder. A longer follow-up and larger case series are necessary to thoroughly evaluate safety, stability, and efficacy of this innovative procedure. Copyright 2013, SLACK Incorporated.

Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Keratoconus Eyes after Accelerated Corneal Collagen Crosslinking

Directory of Open Access Journals (Sweden)

David P. Piñero

2017-01-01

Full Text Available Purpose. To analyze the errors associated to corneal power calculation using the keratometric approach in keratoconus eyes after accelerated corneal collagen crosslinking (CXL surgery and to obtain a model for the estimation of an adjusted corneal refractive index nkadj minimizing such errors. Methods. Potential differences (ΔPc among keratometric (Pk and Gaussian corneal power (PcGauss were simulated. Three algorithms based on the use of nkadj for the estimation of an adjusted keratometric corneal power (Pkadj were developed. The agreement between Pk1.3375 (keratometric power using the keratometric index of 1.3375, PcGauss, and Pkadj was evaluated. The validity of the algorithm developed was investigated in 21 keratoconus eyes undergoing accelerated CXL. Results. Pk1.3375 overestimated corneal power between 0.3 and 3.2 D in theoretical simulations and between 0.8 and 2.9 D in the clinical study (ΔPc. Three linear equations were defined for nkadj to be used for different ranges of r1c. In the clinical study, differences between Pkadj and PcGauss did not exceed ±0.8 D nk=1.3375. No statistically significant differences were found between Pkadj and PcGauss (p>0.05 and Pk1.3375 and Pkadj (p<0.001. Conclusions. The use of the keratometric approach in keratoconus eyes after accelerated CXL can lead to significant clinical errors. These errors can be minimized with an adjusted keratometric approach.

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.

The degree of collagen crosslinks in medical collagen membranes determined by water absorption

International Nuclear Information System (INIS)

Braczko, M.; Tederko, A.; Grzybowski, J.

1994-01-01

Collagen membranes were crosslinked by using three agents: glutaraldehyde, hexametylenediisocyanate, and UV irradiation. The increasing concentrations of above chemical agents or longer time of UV exposition resulted in the higher cross-links degree and in the decrease of collagen membranes swelling (measured as water absorption), their elasticity and mechanical resistance. According to American standards, the degree of collagen biomaterial cross-links is determined by measuring of the digestion time by pepsin. However, that method is very time-consuming. In our study, we have that a simple, linear regression between logarithm of digestion time by pepsin exists and it was identical for all three cross-linking agents used. We have concluded that determination of water absorption can be an alternative, simple and fast method for examination of collagen membrane cross-links degree. (author). 16 refs, 7 figs, 1 tab

Regulation of corneal stroma extracellular matrix assembly.

Science.gov (United States)

Chen, Shoujun; Mienaltowski, Michael J; Birk, David E

2015-04-01

The transparent cornea is the major refractive element of the eye. A finely controlled assembly of the stromal extracellular matrix is critical to corneal function, as well as in establishing the appropriate mechanical stability required to maintain corneal shape and curvature. In the stroma, homogeneous, small diameter collagen fibrils, regularly packed with a highly ordered hierarchical organization, are essential for function. This review focuses on corneal stroma assembly and the regulation of collagen fibrillogenesis. Corneal collagen fibrillogenesis involves multiple molecules interacting in sequential steps, as well as interactions between keratocytes and stroma matrix components. The stroma has the highest collagen V:I ratio in the body. Collagen V regulates the nucleation of protofibril assembly, thus controlling the number of fibrils and assembly of smaller diameter fibrils in the stroma. The corneal stroma is also enriched in small leucine-rich proteoglycans (SLRPs) that cooperate in a temporal and spatial manner to regulate linear and lateral collagen fibril growth. In addition, the fibril-associated collagens (FACITs) such as collagen XII and collagen XIV have roles in the regulation of fibril packing and inter-lamellar interactions. A communicating keratocyte network contributes to the overall and long-range regulation of stromal extracellular matrix assembly, by creating micro-domains where the sequential steps in stromal matrix assembly are controlled. Keratocytes control the synthesis of extracellular matrix components, which interact with the keratocytes dynamically to coordinate the regulatory steps into a cohesive process. Mutations or deficiencies in stromal regulatory molecules result in altered interactions and deficiencies in both transparency and refraction, leading to corneal stroma pathobiology such as stromal dystrophies, cornea plana and keratoconus. Copyright © 2014 Elsevier Ltd. All rights reserved.

Iontophoresis Transcorneal Delivery Technique for Transepithelial Corneal Collagen Crosslinking With Riboflavin in a Rabbit Model.

Science.gov (United States)

Cassagne, Myriam; Laurent, Camille; Rodrigues, Magda; Galinier, Anne; Spoerl, Eberhard; Galiacy, Stéphane D; Soler, Vincent; Fournié, Pierre; Malecaze, François

2016-02-01

We compared an iontophoresis riboflavin delivery technique for transepithelial corneal collagen crosslinking (I-CXL) with a conventional CXL (C-CXL). We designed three experimental sets using 152 New Zealand rabbits to study riboflavin application by iontophoresis using charged riboflavin solution (Ricrolin+) with a 1-mA current for 5 minutes. The first set was to compare riboflavin concentration measured by HPLC in corneas after iontophoresis or conventional riboflavin application. The second set was to analyze autofluorescence and stromal collagen modification immediately and 14 days after I-CXL or C-CXL, by using nonlinear two-photon microscopy (TP) and second harmonic generation (SHG). In the third set, physical modifications after I-CXL and C-CXL were evaluated by stress-strain measurements and by studying corneal resistance against collagenase digestion. Based on HPLC analysis, we found that iontophoresis allowed riboflavin diffusion with 2-fold less riboflavin concentration than conventional application (936.2 ± 312.5 and 1708 ± 908.3 ng/mL, respectively, P riboflavin delivery in crosslinking treatments, preserving the epithelium.

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

Directory of Open Access Journals (Sweden)

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

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.

Can possible toxic effect of ultraviolet-A after corneal cross-linking be prevented? In vitro transmittance study of contact lenses at 370 nm wavelength.

Science.gov (United States)

Bilgihan, Kamil; Yuksel, Erdem; Deniz, Nuriye Gokcen; Yuksel, Nilay

2015-01-01

Corneal collagen cross linking (CCL) with ultraviolet A (UVA) has been proposed as a treatment for the progression of corneal ectasia associated with keratoconus and post-laser-assisted in situ keratomileusis (LASIK) ectasia. Despite the reports about safety of procedure, we consider that UVA of sunlight can effect riboflavin saturated and de-epitelizated cornea early after CCL. To evaluate the UVA blockage capability of 11 different silicone hydrogel contact lenses which are widely used after CCL treatment. Eleven different silicone hydrogel and daily disposable contact lenses were evaluated. The UVA light at 365 nm wavelength for UVA source and UV light meter to measure UVA radiation were used. 3, 9 and 18 mW/cm(2) power of UV radiance was applied centrally to the each type of contact lenses. The power of UVA transmittance for each radiance and percentage of blockage were evaluated for each brand. Also, protection factor (PF) was calculated. The senofilcon A and narafilcon A had the highest blockage and lowest transmittance (p = 0.02). PF was significantly higher in the senofilcon A and narafilcon A at 3, 9 and 18 mW/cm(2) (p = 0.0001). And also, the hilafilcon B, filcon IV, nelfilcon A, enfilcon A, lotrafilcon A and lotrafilcon B had the highest UVA transmittance. The narafilcon A and the senofilcon A may be a good options for epithelial healing after CCL procedure to protect the cornea from UVA of sunlight. And also, the hilafilcon B, filcon IV, nelfilcon A, enfilcon A, lotrafilcon A and lotrafilcon B contact lenses that have high-UVA transmittance feature can be a treatment choice for contact lens-assisted CCL technique in thin corneas.

Corneal biomechanical properties from air-puff corneal deformation imaging

Science.gov (United States)

Marcos, Susana; Kling, Sabine; Bekesi, Nandor; Dorronsoro, Carlos

2014-02-01

The combination of air-puff systems with real-time corneal imaging (i.e. Optical Coherence Tomography (OCT), or Scheimpflug) is a promising approach to assess the dynamic biomechanical properties of the corneal tissue in vivo. In this study we present an experimental system which, together with finite element modeling, allows measurements of corneal biomechanical properties from corneal deformation imaging, both ex vivo and in vivo. A spectral OCT instrument combined with an air puff from a non-contact tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal deformation of the corneal apex. Quantitative analysis allows direct extraction of several deformation parameters, such as apex indentation across time, maximal indentation depth, temporal symmetry and peak distance at maximal deformation. The potential of the technique is demonstrated and compared to air-puff imaging with Scheimpflug. Measurements ex vivo were performed on 14 freshly enucleated porcine eyes and five human donor eyes. Measurements in vivo were performed on nine human eyes. Corneal deformation was studied as a function of Intraocular Pressure (IOP, 15-45 mmHg), dehydration, changes in corneal rigidity (produced by UV corneal cross-linking, CXL), and different boundary conditions (sclera, ocular muscles). Geometrical deformation parameters were used as input for inverse finite element simulation to retrieve the corneal dynamic elastic and viscoelastic parameters. Temporal and spatial deformation profiles were very sensitive to the IOP. CXL produced a significant reduction of the cornea indentation (1.41x), and a change in the temporal symmetry of the corneal deformation profile (1.65x), indicating a change in the viscoelastic properties with treatment. Combining air-puff with dynamic imaging and finite element modeling allows characterizing the corneal biomechanics in-vivo.

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

A Comparison of Different Corneal Iontophoresis Protocols for Promoting Transepithelial Riboflavin Penetration.

Science.gov (United States)

Gore, Daniel M; O'Brart, David P; French, Paul; Dunsby, Chris; Allan, Bruce D

2015-12-01

To measure corneal riboflavin penetration using different transepithelial iontophoresis protocols. Freshly enucleated rabbit eyes were divided into nine treatment groups of 4 eyes. One group, in which 0.1% wt/vol riboflavin was applied for 30 minutes without iontophoresis after corneal epithelial debridement, acted as a control. The remaining groups were treated with an intact epithelium using different riboflavin formulations and varying iontophoresis current, soak, and rinse times. After riboflavin application, eyes were snap frozen in liquid nitrogen. Corneal cross sections 35 μm thick were then imaged immediately by two-photon fluorescence microscopy, using image processing software to quantify stromal riboflavin concentration at different corneal depths. In the epithelium-on iontophoresis treatment groups, greater stromal riboflavin penetration was achieved with higher-concentration riboflavin solutions, greater iontophoresis dosage, and longer solution contact times. A protocol utilizing 0.25% wt/vol riboflavin with benzalkonium chloride (BAC) 0.01% and two cycles of applied current and subsequent soaking (1 mA 5 minutes, soak 5 minutes; 0.5 mA 5 minutes, soak 5 minutes) achieved similar stromal riboflavin penetration to epithelium-off controls. The best-performing non-BAC-containing protocol produced stromal riboflavin penetration approximately 60% that of epithelium-off controls. Riboflavin solutions containing saline resulted in minimal stromal penetration. Riboflavin loading within the epithelium was equivalent to or higher than that in the subjacent stroma, despite rinsing the ocular surface with balanced salt solution. Modified iontophoresis protocols can significantly improve transepithelial riboflavin penetration in experimental corneal collagen cross-linking.

The effects of different cross-linking conditions on collagen-based nanocomposite scaffolds—an in vitro evaluation using mesenchymal stem cells

International Nuclear Information System (INIS)

Suchý, Tomáš; Šupová, Monika; Sucharda, Zbyněk; Rýglová, Šárka; Žaloudková, Margit; Sauerová, Pavla; Kalbáčová, Marie Hubálek; Verdánová, Martina; Sedláček, Radek

2015-01-01

Nanocomposite scaffolds which aimed to imitate a bone extracellular matrix were prepared for bone surgery applications. The scaffolds consisted of polylactide electrospun nano/sub-micron fibres, a natural collagen matrix supplemented with sodium hyaluronate and natural calcium phosphate nano-particles (bioapatite). The mechanical properties of the scaffolds were improved by means of three different cross-linking agents: N-(3-dimethylamino propyl)-N’-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide in an ethanol solution (EDC/NHS/EtOH), EDC/NHS in a phosphate buffer saline solution (EDC/NHS/PBS) and genipin. The effect of the various cross-linking conditions on the pore size, structure and mechanical properties of the scaffolds were subsequently studied. In addition, the mass loss, the swelling ratio and the pH of the scaffolds were determined following their immersion in a cell culture medium. Furthermore, the metabolic activity of human mesenchymal stem cells (hMSCs) cultivated in scaffold infusions for 2 and 7 days was assessed. Finally, studies were conducted of cell adhesion, proliferation and penetration into the scaffolds. With regard to the structural stability of the tested scaffolds, it was determined that EDC/NHS/PBS and genipin formed the most effectively cross-linked materials. Moreover, it was discovered that the genipin cross-linked scaffold also provided the best conditions for hMSC cultivation. In addition, the infusions from all the scaffolds were found to be non-cytotoxic. Thus, the genipin and EDC/NHS/PBS cross-linked scaffolds can be considered to be promising biomaterials for further in vivo testing and bone surgery applications. (paper)

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.

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

Directory of Open Access Journals (Sweden)

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.

Comparing Change in Anterior Curvature after Corneal Cross-Linking Using Scanning-Slit and Scheimpflug Technology.

Science.gov (United States)

Lang, Paul Z; Thulasi, Praneetha; Khandelwal, Sumitra S; Hafezi, Farhad; Randleman, J Bradley

2018-05-02

To evaluate the correlation between anterior axial curvature difference maps following corneal cross-linking (CXL) for progressive keratoconus obtained from Scheimpflug-based tomography and Placido-based topography. Between-devices reliability analysis of randomized clinical trial data METHODS: Corneal imaging was collected at a single center institution pre-operatively and at 3, 6, and 12 months post-operatively using Scheimpflug-based tomography (Pentacam, Oculus Inc., Lynnwood, WA) and Scanning-slit, Placido-based topography (Orbscan II, Bausch & Lomb, Rochester, NY) in patients with progressive keratoconus receiving standard protocol CXL (3mW/cm 2 for 30 minutes). Regularization index (RI), absolute maximum keratometry (K Max), and change in (ΔK Max) were compared between the two devices at each time point. 51 eyes from 36 patients were evaluated at all time points. values were significantly different at all time points [56.01±5.3D Scheimpflug vs. 55.04±5.1D scanning-slit pre-operatively (p=0.003); 54.58±5.3D Scheimpflug vs. 53.12±4.9D scanning-slit at 12 months (pdevices (r=0.90-0.93) at all time points. The devices were not significantly different at any time point for either ΔK Max or RI but were poorly correlated at all time points (r=0.41-0.53 for ΔK Max, r=0.29-0.48 for RI). At 12 months, 95% LOA was 7.51D for absolute, 8.61D for ΔK Max, and 19.86D for RI. Measurements using Scheimpflug and scanning-slit Placido-based technology are correlated but not interchangeable. Both devices appear reasonable for separately monitoring the cornea's response to CXL; however, caution should be used when comparing results obtained with one measuring technology to the other. Copyright © 2018 Elsevier Inc. All rights reserved.

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.

Evaluating the Toxicity/Fixation Balance for Corneal Cross-Linking With Sodium Hydroxymethylglycinate (SMG) and Riboflavin-UVA (CXL) in an Ex Vivo Rabbit Model Using Confocal Laser Scanning Fluorescence Microscopy.

Science.gov (United States)

Kim, Su-Young; Babar, Natasha; Munteanu, Emilia Laura; Takaoka, Anna; Zyablitskaya, Mariya; Nagasaki, Takayuki; Trokel, Stephen L; Paik, David C

2016-04-01

To develop methods to delineate the relationship between endothelial cell toxicity and tissue fixation (toxicity/fixation) using sodium hydroxymethylglycinate (SMG), a formaldehyde releaser, and riboflavin-UVA photochemical corneal cross-linking (CXL) for therapeutic tissue cross-linking of the cornea. Eleven fresh cadaveric rabbit heads were used for ex vivo corneal cross-linking simulation. After epithelial debridement, the tissue was exposed to 1/4 max (9.8 mM) or 1/3 max (13 mM) SMG at pH 8.5 for 30 minutes or riboflavin-UVA (CXL). The contralateral cornea served as a paired control. Postexposure, cross-linking efficacy was determined by thermal denaturation temperature (Tm) and endothelial damage was assessed using calcein AM and ethidium homodimer staining (The Live/Dead Kit). Confocal laser scanning fluorescence microscopy was used to generate live/dead cell counts using a standardized algorithm. The ΔTm after CXL, 1/3 SMG, and 1/4 SMG was 2.2 ± 0.9°C, 1.3 ± 0.5°C, and 1.1 ± 0.5°C, respectively. Endothelial cell damage was expressed as the percent of dead cells/live + dead cells counted per high-power field. The values were 3 ± 1.7% (control) and 8.9 ± 11.1% (CXL) (P = 0.390); 1 ± 0.2% (control) and 19.5 ± 32.2% (1/3 max SMG) (P = 0.426); and 2.7 ± 2.4% (control) and 2.8 ± 2.2% (1/4 max SMG) (P = 0.938). The values for endothelial toxicity were then indexed over the shift in Tm to yield a toxicity/fixation index. The values were as follows: 2.7 for CXL, 14 for 1/3 max, and 0.1 for 1/4 max. Quarter max (1/4 max = 9.8 mM) SMG effectively cross-linked tissue and was nontoxic to endothelial cells. Thus, SMG is potentially a compound that could achieve both desired effects.

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

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

Pirfenidone nanoparticles improve corneal wound healing and prevent scarring following alkali burn.

Directory of Open Access Journals (Sweden)

Sushovan Chowdhury

Full Text Available To evaluate the effects of pirfenidone nanoparticles on corneal re-epithelialization and scarring, major clinical challenges after alkali burn.Effect of pirfenidone on collagen I and α-smooth muscle actin (α-SMA synthesis by TGFβ induced primary corneal fibroblast cells was evaluated by immunoblotting and immunocytochemistry. Pirfenidone loaded poly (lactide-co-glycolide (PLGA nanoparticles were prepared, characterized and their cellular entry was examined in primary corneal fibroblast cells by fluorescence microscopy. Alkali burn was induced in one eye of Sprague Dawley rats followed by daily topical treatment with free pirfenidone, pirfenidone nanoparticles or vehicle. Corneal re-epithelialization was assessed daily by flourescein dye test; absence of stained area indicated complete re-epithelialization and the time for complete re-epithelialization was determined. Corneal haze was assessed daily for 7 days under slit lamp microscope and graded using a standard method. After 7 days, collagen I deposition in the superficial layer of cornea was examined by immunohistochemistry.Pirfenidone prevented (P<0.05 increase in TGF β induced collagen I and α-SMA synthesis by corneal fibroblasts in a dose dependent manner. Pirfenidone could be loaded successfully within PLGA nanoparticles, which entered the corneal fibroblasts within 5 minutes. Pirfenidone nanoparticles but not free pirfenidone significantly (P<0.05 reduced collagen I level, corneal haze and the time for corneal re-epithelialization following alkali burn.Pirfenidone decreases collagen synthesis and prevents myofibroblast formation. Pirfenidone nanoparticles improve corneal wound healing and prevent fibrosis. Pirfenidone nanoparticles are of potential value in treating corneal chemical burns and other corneal fibrotic diseases.

EXPERIMENTAL REPAIR OF DEEP CORNEAL DEFECTS USING A BIO-CONSTRUCT COMPRISING A COLLAGEN TYPE I MATRIX LOADED WITH BUCCAL EPITHELIAL CELLS

Directory of Open Access Journals (Sweden)

N. S. Egorova

2017-01-01

Full Text Available The  research  objective was  to study the  reparative effects of  the  collagen  type  I bio-construct loaded  with buccal epithelial cells, on the rabbit cornea after experimental keratectomy at various stages of treatment (on the 3rd, 7th, 14th, 3 0th days.Material  and methods.  The  experiments were  conducted on 20 rabbits  of  the  Chinchilla breed that  were  operated on cornea of both eyes aiming to inflict epithelial and stromal cornea defects. The collagen-based bio-construct bearing buccal epithelial cells was placed  over the cornea of the experimental eyes. The  cornea of the control  eyes was covered with smooth contact lens. After the surgery, a temporal blepharorrhaphy was performed and kept for 3 days. We studied macroand microscopic pattern of corneal regeneration at 3, 7, 14, and 30 days of experiment.Results. When  using the collaged-based bio-construct containing buccal epithelial cells, the complete epithelialization of the corneal defect occurred at mean 7 days earlier compared to that in the control eyes. Thus, the offered bio-construct stimulated the cell migration and proliferation at early stages of treatment (3–7 days reducing the inflammation activity.Conclusion. The bio-construct comprising a collagen type  I matrix loaded with buccal epithelial cells can provide an effective treatment option for corneal defects.

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

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.

Donor cross-linking for keratoplasty: a laboratory evaluation.

Science.gov (United States)

Mukherjee, Achyut; Hayes, Sally; Aslanides, Ioannis; Lanchares, Elena; Meek, Keith M

2015-12-01

This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty. Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups. In the cross-linked group, donor corneas underwent riboflavin/UVA cross-linking prior to being trephined and sutured to untreated hosts. In the conventional keratoplasty group, both host and donor corneas remained untreated prior to keratoplasty. Topographic and corneal wavefront measurements were performed following surgery, and technical aspects of the procedure evaluated. Mean keratometric astigmatism was significantly lower in the cross-linked donor group at 3.67D (SD 1.8 D), vs. 8.43 D (SD 2.4 D) in the conventional keratoplasty group (p < 0.005). Mean wavefront astigmatism was also significantly reduced in the cross-linked donor group 4.71 D (SD 2.1) vs. 8.29D (SD 3.6) in the conventional keratoplasty group (p < 0.005). Mean RMS higher order aberration was significantly lower in the cross-linked donor group at 1.79 um (SD 0.98), vs. 3.05 um (SD 1.9) in the conventional keratoplasty group (P = 0.02). Qualitative analysis revealed less tissue distortion at the graft-host junction in the cross-linked group. Cross-linking of donor corneas prior to keratoplasty reduces intraoperative induced astigmatism and aberrations in an animal model. Further studies are indicated to evaluate the implications of this potential modification of keratoplasty surgery.

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

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......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 8 MPa to 39 MPa. The mechanical effects of glutaraldehyde at the tendon fibril level...

The ratio 1660/1690 cm(-1) measured by infrared microspectroscopy is not specific of enzymatic collagen cross-links in bone tissue.

Science.gov (United States)

Farlay, Delphine; Duclos, Marie-Eve; Gineyts, Evelyne; Bertholon, Cindy; Viguet-Carrin, Stéphanie; Nallala, Jayakrupakar; Sockalingum, Ganesh D; Bertrand, Dominique; Roger, Thierry; Hartmann, Daniel J; Chapurlat, Roland; Boivin, Georges

2011-01-01

In postmenopausal osteoporosis, an impairment in enzymatic cross-links (ECL) occurs, leading in part to a decline in bone biomechanical properties. Biochemical methods by high performance liquid chromatography (HPLC) are currently used to measure ECL. Another method has been proposed, by Fourier Transform InfraRed Imaging (FTIRI), to measure a mature PYD/immature DHLNL cross-links ratio, using the 1660/1690 cm(-1) area ratio in the amide I band. However, in bone, the amide I band composition is complex (collagens, non-collagenous proteins, water vibrations) and the 1660/1690 cm(-1) by FTIRI has never been directly correlated with the PYD/DHLNL by HPLC. A study design using lathyritic rats, characterized by a decrease in the formation of ECL due to the inhibition of lysyl oxidase, was used in order to determine the evolution of 1660/1690 cm(-1) by FTIR Microspectroscopy in bone tissue and compare to the ECL quantified by HPLC. The actual amount of ECL was quantified by HPLC on cortical bone from control and lathyritic rats. The lathyritic group exhibited a decrease of 78% of pyridinoline content compared to the control group. The 1660/1690 cm(-1) area ratio was increased within center bone compared to inner bone, and this was also correlated with an increase in both mineral maturity and mineralization index. However, no difference in the 1660/1690 cm(-1) ratio was found between control and lathyritic rats. Those results were confirmed by principal component analysis performed on multispectral infrared images. In bovine bone, in which PYD was physically destructed by UV-photolysis, the PYD/DHLNL (measured by HPLC) was strongly decreased, whereas the 1660/1690 cm(-1) was unmodified. In conclusion, the 1660/1690 cm(-1) is not related to the PYD/DHLNL ratio, but increased with age of bone mineral, suggesting that a modification of this ratio could be mainly due to a modification of the collagen secondary structure related to the mineralization process.

The Ratio 1660/1690 cm−1 Measured by Infrared Microspectroscopy Is Not Specific of Enzymatic Collagen Cross-Links in Bone Tissue

Science.gov (United States)

Farlay, Delphine; Duclos, Marie-Eve; Gineyts, Evelyne; Bertholon, Cindy; Viguet-Carrin, Stéphanie; Nallala, Jayakrupakar; Sockalingum, Ganesh D.; Bertrand, Dominique; Roger, Thierry; Hartmann, Daniel J.; Chapurlat, Roland; Boivin, Georges

2011-01-01

In postmenopausal osteoporosis, an impairment in enzymatic cross-links (ECL) occurs, leading in part to a decline in bone biomechanical properties. Biochemical methods by high performance liquid chromatography (HPLC) are currently used to measure ECL. Another method has been proposed, by Fourier Transform InfraRed Imaging (FTIRI), to measure a mature PYD/immature DHLNL cross-links ratio, using the 1660/1690 cm−1 area ratio in the amide I band. However, in bone, the amide I band composition is complex (collagens, non-collagenous proteins, water vibrations) and the 1660/1690 cm−1 by FTIRI has never been directly correlated with the PYD/DHLNL by HPLC. A study design using lathyritic rats, characterized by a decrease in the formation of ECL due to the inhibition of lysyl oxidase, was used in order to determine the evolution of 1660/1690 cm−1 by FTIR Microspectroscopy in bone tissue and compare to the ECL quantified by HPLC. The actual amount of ECL was quantified by HPLC on cortical bone from control and lathyritic rats. The lathyritic group exhibited a decrease of 78% of pyridinoline content compared to the control group. The 1660/1690 cm−1 area ratio was increased within center bone compared to inner bone, and this was also correlated with an increase in both mineral maturity and mineralization index. However, no difference in the 1660/1690 cm−1 ratio was found between control and lathyritic rats. Those results were confirmed by principal component analysis performed on multispectral infrared images. In bovine bone, in which PYD was physically destructed by UV-photolysis, the PYD/DHLNL (measured by HPLC) was strongly decreased, whereas the 1660/1690 cm−1 was unmodified. In conclusion, the 1660/1690 cm−1 is not related to the PYD/DHLNL ratio, but increased with age of bone mineral, suggesting that a modification of this ratio could be mainly due to a modification of the collagen secondary structure related to the mineralization process. PMID:22194900

The carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen in serum as a marker of bone resorption

DEFF Research Database (Denmark)

Hassager, C; Jensen, L T; Pødenphant, J

1994-01-01

Carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP) in serum has recently been proposed as a new biochemical marker of bone resorption. In the present study we compared serum ICTP with radiopharmaceutical and histomorphometric measurements of bone turnover...... in postmenopausal women with mild osteoporosis, and assessed the effect of hormone replacement therapy (HRT) (2 mg 17 beta-estradiol plus 1 mg norethisterone daily) and anabolic steroid therapy (50 mg nandrolone decanoate (ND) i.m. every 3 weeks) on serum ICTP in two double-blind placebo-controlled studies with 55...... to 75-year-old women. Serum ICTP measured by radioimmunoassay (RIA) correlated significantly with the 24-hour whole body retention of 99m-technetium diphosphonate (Rho = 0.47, P

The Influence of Lamellar Orientation on Corneal Material Behavior: Biomechanical and Structural Changes in an Avian Corneal Disorder

Science.gov (United States)

Elsheikh, Ahmed; Kassem, Wael; Kamma-Lorger, Christina S.; Hocking, Paul M.; White, Nick; Inglehearn, Chris F.; Ali, Manir; Meek, Keith M.

2011-01-01

Purpose. Retinopathy, globe enlarged (RGE) is an inherited genetic disease of chickens with a corneal phenotype characterized by loss of tissue curvature and changes in peripheral collagen fibril alignment. This study aimed to characterize the material behavior of normal and RGE chicken corneas under inflation and compare this with new spatial- and depth-resolved microstructural information to investigate how stromal fibril architecture determines corneal behavior under intraocular pressure (IOP). Methods. Six RGE chicken corneas and six age-matched normal controls were tested using trephinate inflation and their stress-strain behavior determined as a function of posterior pressure. Second harmonic generation mulitphoton microscopy was used to compare the in-plane appearance and degree of through-plane interlacing of collagen lamellae between normal and mutant corneas. Results. RGE corneas displayed a 30–130% increase in material stiffness [Etangent(RGE) = 0.94 ± 0.18 MPa to 3.09 ± 0.66 MPa; Etangent(normals) = 0.72 ± 0.13 MPa to 1.34 ± 0.35 MPa] (P ≤ 0.05). The normal in-plane disposition of anterior collagen in the peripheral cornea was altered in RGE but through-plane lamellar interlacing was unaffected. Conclusions. This article demonstrates changes in corneal material behavior in RGE that are qualitatively consistent with microstructural collagen alterations identified both herein and previously. This study indicates that, in general, changes in stromal fibril orientation may significantly affect corneal material behavior and thereby its response to IOP. PMID:21051696

Effects of advanced glycation end-product inhibition and cross-link breakage in diabetic rats

DEFF Research Database (Denmark)

Oturai, P S; Christensen, M; Rolin, B

2000-01-01

), and a breaker of already formed AGE cross-links, N-phenacylthiazolium bromide (PTB), were investigated in streptozotocin-diabetic female Wistar rats. Diabetes for 24 weeks resulted in decreased tail collagen pepsin solubility, reflecting the formation of AGE cross-linking. Collagen solubility was significantly...... ameliorated by treatment with NNC39-0028, whereas PTB had no effect. Increased urinary albumin excretion (UAE) in diabetic rats was observed in serial measurements throughout the study period, and was not reduced by any treatment. Vascular dysfunction in the eye, measured as increased clearance of 125I......-albumin, was induced by diabetes. NNC39-0028 did not affect this abnormality. This study demonstrated a pharmacological inhibition of collagen solubility alterations in diabetic rats without affecting diabetes-induced pathophysiology such as the increase in UAE or albumin clearance. Treatment with PTB, a specific...

Intracorneal ring segments implantation followed by same-day topography-guided PRK and corneal collagen CXL in low to moderate keratoconus.

Science.gov (United States)

Al-Tuwairqi, Waleed; Sinjab, Mazen M

2013-01-01

To evaluate the safety and efficacy of intrastromal corneal ring segments (ICRS) implantation followed by same-day topography-guided photorefractive keratectomy (PRK) and ultraviolet-A/riboflavin collagen cross-linking (CXL) in patients with low to moderate keratoconus. Patients with low to moderate keratoconus and contact lens intolerance were included in the study. All patients first underwent femtosecond laser-enabled placement of ICRS (Keraring, Mediphacos) (first step). Same-day topography-guided PRK and CXL (second step) were subsequently performed in all patients after the refraction was stable (average 6 months [range: 3 to 11 months]). Thirteen eyes from 13 patients were included in the study. Based on values before the first step and 6 months after the second step, significant improvements were noted in uncorrected distance visual acuity (0.7±0.32 logMAR vs 0.08±0.08 logMAR), corrected distance visual acuity (CDVA) (0.16±0.19 logMAR vs 0.02±0.04 log-MAR), sphere (-3.65±3.08 diopters [D] vs 0.06±1.6 D), astigmatism (-3.31±1.5 D vs -0.98±0.75 D), average K (47.28±1.99 D vs 41.42±3.22 D), and coma (2.36±1.23 μm vs 1.47±0.68 μm) (PPRK/CXL may be a reasonable option for improving visual acuity in patients with low to moderate keratoconus. Copyright 2013, SLACK Incorporated.

Uncoupling of collagen II metabolism in newly diagnosed, untreated rheumatoid arthritis is linked to inflammation and antibodies against cyclic citrullinated peptides

DEFF Research Database (Denmark)

Christensen, Anne Friesgaard; Hørslev-Petersen, Kim; Christgau, Stephan

2010-01-01

. METHODS: One hundred sixty patients with newly diagnosed, untreated RA entered the Cyclosporine, Methotrexate, Steroid in RA (CIMESTRA) trial. Disease activity and radiograph status were measured at baseline and 4 years. The N-terminal propeptide of collagen IIA (PIIANP) and the cross-linked C...... associations of collagen II anabolism (PIIANP) and collagen II degradation (CTX-II) with anti-CCP, synovitis, and radiographic progression indicate that at this early stage of RA, cartilage collagen degradation is mainly driven by synovitis, while anti-CCP antibodies may interfere with cartilage regeneration...

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

Directory of Open Access Journals (Sweden)

Ferial M. Zeraid

2014-10-01

Full Text Available AIM:To present the results of same-day topography-guided 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 twenty-one 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; Kflat value decreased from:48.44±3.66 D to 43.71±1.95 D; Ksteep value decreased from 45.61±2.40 D to 41.56±2.05 D; Kaverage also decreased from 47.00±2.66 D to 42.42±2.07 D (P<0.05 for all. The mean sphere and cylinder 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 post-ISCR, 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.

Building blocks of Collagen based biomaterial devices

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Building blocks of Collagen based biomaterial devices. Collagen as a protein. Collagen in tissues and organs. Stabilizing and cross linking agents. Immunogenicity. Hosts (drugs). Controlled release mechanisms of hosts. Biodegradability, workability into devices ...

Matrix cross-linking lysyl oxidases are induced in response to myocardial infarction and promote cardiac dysfunction

DEFF Research Database (Denmark)

González-Santamaría, José; Villalba, María; Busnadiego, Oscar

2016-01-01

arrhythmias, and sudden cardiac death. Cardiac fibrosis is characterized by extensive deposition of collagen and also by increased stiffness as a consequence of enhanced collagen cross-linking. Members of the lysyl oxidase (LOX) family of enzymes are responsible for the formation of collagen cross......-links. This study investigates the contribution of LOX family members to the heart response to MI. METHODS AND RESULTS: Experimental MI was induced in C57BL/6 mice by permanent ligation of the left anterior descending coronary artery. The expression of LOX isoforms (LOX and LOXL1-4) was strongly increased upon MI...... resulted in reduced ventricular dilatation and improved cardiac function. CONCLUSION: LOX family members contribute significantly to the detrimental effects of cardiac remodelling, highlighting LOX inhibition as a potential therapeutic strategy for post-infarction recovery....

New Details of the Human Corneal Limbus Revealed With Second Harmonic Generation Imaging.

Science.gov (United States)

Park, Choul Yong; Lee, Jimmy K; Zhang, Cheng; Chuck, Roy S

2015-09-01

To report novel findings of the human corneal limbus by using second harmonic generation (SHG) imaging. Corneal limbus was imaged by using an inverted two-photon excitation fluorescence microscope. Laser (Ti:Sapphire) was tuned at 850 nm for two-photon excitation. Backscatter signals of SHG and autofluorescence (AF) were collected through a 425/30-nm emission filter and a 525/45-emission filter, respectively. Multiple, consecutive, and overlapping image stacks (z-stack) were acquired for the corneal limbal area. Two novel collagen structures were revealed by SHG imaging at the limbus: an anterior limbal cribriform layer and presumed anchoring fibers. Anterior limbal cribriform layer is an intertwined reticular collagen architecture just beneath the limbal epithelial niche and is located between the peripheral cornea and Tenon's/scleral tissue. Autofluorescence imaging revealed high vascularity in this structure. Central to the anterior limbal cribriform layer, radial strands of collagen were found to connect the peripheral cornea to the limbus. These presumed anchoring fibers have both collagen and elastin and were found more extensively in the superficial layers than deep layer and were absent in very deep limbus near Schlemm's canal. By using SHG imaging, new details of the collagen architecture of human corneal limbal area were elucidated. High resolution images with volumetric analysis revealed two novel collagen structures.

Diffusion of ionic and non-ionic contrast agents in articular cartilage with increased cross-linking--contribution of steric and electrostatic effects.

Science.gov (United States)

Kulmala, K A M; Karjalainen, H M; Kokkonen, H T; Tiitu, V; Kovanen, V; Lammi, M J; Jurvelin, J S; Korhonen, R K; Töyräs, J

2013-10-01

To investigate the effect of threose-induced collagen cross-linking on diffusion of ionic and non-ionic contrast agents in articular cartilage. Osteochondral plugs (Ø=6mm) were prepared from bovine patellae and divided into two groups according to the contrast agent to be used in contrast enhanced computed tomography (CECT) imaging: (I) anionic ioxaglate and (II) non-ionic iodixanol. The groups I and II contained 7 and 6 sample pairs, respectively. One of the paired samples served as a reference while the other was treated with threose to induce collagen cross-linking. The equilibrium partitioning of the contrast agents was imaged after 24h of immersion. Fixed charge density (FCD), water content, contents of proteoglycans, total collagen, hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent) cross-links were determined as a reference. The equilibrium partitioning of ioxaglate (group I) was significantly (p=0.018) lower (-23.4%) in threose-treated than control samples while the equilibrium partitioning of iodixanol (group II) was unaffected by the threose-treatment. FCD in the middle and deep zones of the cartilage (pionic iodixanol showed no changes in partition after cross-linking, in contrast to anionic ioxaglate, we conclude that the cross-linking induced changes in charge distribution have greater effect on diffusion compared to the cross-linking induced changes in steric hindrance. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

Large proteoglycan complexes and disturbed collagen architecture in the corneal extracellular matrix of mucopolysaccharidosis type VII (Sly syndrome).

Science.gov (United States)

Young, Robert D; Liskova, Petra; Pinali, Christian; Palka, Barbara P; Palos, Michalis; Jirsova, Katerina; Hrdlickova, Enkela; Tesarova, Marketa; Elleder, Milan; Zeman, Jiri; Meek, Keith M; Knupp, Carlo; Quantock, Andrew J

2011-08-24

Deficiencies in enzymes involved in proteoglycan (PG) turnover underlie a number of rare mucopolysaccharidoses (MPS), investigations of which can considerably aid understanding of the roles of PGs in corneal matrix biology. Here, the authors analyze novel pathologic changes in MPS VII (Sly syndrome) to determine the nature of PG-collagen associations in stromal ultrastructure. Transmission electron microscopy and electron tomography were used to investigate PG-collagen architectures and interactions in a cornea obtained at keratoplasty from a 22-year-old man with MPS VII, which was caused by a compound heterozygous mutation in the GUSB gene. Transmission electron microscopy showed atypical morphology of the epithelial basement membrane and Bowman's layer in MPS VII. Keratocytes were packed with cytoplasmic vacuoles containing abnormal glycosaminoglycan (GAG) material, and collagen fibrils were thinner than in normal cornea and varied considerably throughout anterior (14-32 nm), mid (13-42 nm), and posterior (17-39 nm) regions of the MPS VII stroma. PGs viewed in three dimensions were striking in appearance in that they were significantly larger than PGs in normal cornea and formed highly extended linkages with multiple collagen fibrils. Cellular changes in the MPS VII cornea resemble those in other MPS. However, the wide range of collagen fibril diameters throughout the stroma and the extensive matrix presence of supranormal-sized PG structures appear to be unique features of this disorder. The findings suggest that the accumulation of stromal chondroitin-, dermatan-, and heparan-sulfate glycosaminoglycans in the absence of β-glucuronidase-mediated degradation can modulate collagen fibrillogenesis.

Second Harmonic Generation Imaging Analysis of Collagen Arrangement in Human Cornea.

Science.gov (United States)

Park, Choul Yong; Lee, Jimmy K; Chuck, Roy S

2015-08-01

To describe the horizontal arrangement of human corneal collagen bundles by using second harmonic generation (SHG) imaging. Human corneas were imaged with an inverted two photon excitation fluorescence microscope. The excitation laser (Ti:Sapphire) was tuned to 850 nm. Backscatter signals of SHG were collected through a 425/30-nm bandpass emission filter. Multiple, consecutive, and overlapping image stacks (z-stacks) were acquired to generate three dimensional data sets. ImageJ software was used to analyze the arrangement pattern (irregularity) of collagen bundles at each image plane. Collagen bundles in the corneal lamellae demonstrated a complex layout merging and splitting within a single lamellar plane. The patterns were significantly different in the superficial and limbal cornea when compared with deep and central regions. Collagen bundles were smaller in the superficial layer and larger in deep lamellae. By using SHG imaging, the horizontal arrangement of corneal collagen bundles was elucidated at different depths and focal regions of the human cornea.

Chemical Stabilisation of Collagen as a Biomimetic

Directory of Open Access Journals (Sweden)

R. Gordon Paul

2003-01-01

Full Text Available Collagen is the most abundant protein in animals and because of its high mechanical strength and good resistance to degradation has been utilized in a wide range of products in industry whilst its low antigenicity has resulted in its widespread use in medicine. Collagen products can be purified from fibres, molecules reconstituted as fibres or from specific recombinant polypeptides with preferred properties. A common feature of all these biomaterials is the need for stable chemical cross-linking to control the mechanical properties and the residence time in the body, and to some extent the immunogenicity of the device. This can be achieved by a number of different cross-linking agents that react with specific amino acid residues on the collagen molecule imparting individual biochemical, thermal and mechanical characteristics to the biomaterial. In this review we have summarised the major techniques for testing these characteristics and the mechanisms involved in the variety of cross-linking reactions to achieve particular properties..

Are the surgeons safe during UV-A radiation exposure in collagen cross-linking procedure?

Science.gov (United States)

Shetty, Rashmi; Shetty, Rohit; Mahendradas, Padmamalini; Shetty, Bhujang K

2012-02-01

To quantify the effect of scattered UV-A radiation used in the collagen cross-linking (CXL) procedure and the amount of radiation reaching the surgeon and the surrounding area and to estimate the dampening effect by various protective devices. In this case series, 3 patients [aged 25-30 (±2.5) years] with keratoconus underwent a CXL procedure with UV-A light and riboflavin. Irradiance was measured using a spectrometer (Model USB2000; Ocean Optics, Inc) for various distances from the source, at various angles, and for different durations of radiation. The spectrometer was also used to measure the dampening effect produced by gown, latex gloves, and UV-protective glasses. Maximum UV-A radiation (1.4 × 10(-9) mW/cm(2)) was measured at 2 cm from the limbus, when the probe was held at a 45-degree angle to the floor. UV-A radiation reaching the surgeon's eye and the abdomen was 3.403 × 10(-11) and 2.36 × 10(-11) mW/cm(2), respectively. Gown, latex gloves, and UV-protective glasses showed dampening effects of 99.58%, 95.01%, and 99.73%, respectively. CXL appears to be a safe procedure with respect to UV-A radiation exposure to the surgeon. Further safety can be ensured by UV-protective devices.

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.

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.

Proteases, proteolysis and inflammatory molecules in the tears of people with keratoconus.

Science.gov (United States)

Balasubramanian, Sivaraman Arumugam; Mohan, Sujatha; Pye, David Cecil; Willcox, Mark Duncan Perry

2012-06-01

To investigate the expression of proteases, proteolytic activity and cytokines in the tear film of people with keratoconus. Basal tears from people with keratoconus, from individuals who had undergone corneal collagen cross-linking for the treatment of keratoconus, and from normal controls were collected using a capillary tube. Corneal curvature of each subject was mapped. The total protein in tears was estimated. Levels and activity of proteases in the tears were analysed using specific antibody arrays and activity assays. The total tear protein level was significantly reduced in keratoconus (4.1 ± 0.9 mg/ml) compared with normals (6.7 ± 1.4 mg/ml) (p tear expression of matrix metalloproteinases (MMP) -1, -3, -7, -13, interleukins (IL) -4, -5, -6, -8 and tumour necrosis factor (TNF) -α, -β were evident in keratoconus. Tear IL-6 was the only cytokine significantly (p tears of keratoconus subjects compared with the collagen cross-linked group. No significant difference in tear proteases were observed between the normal and the cross-linked groups, although the expression of TNF-α was significantly (p tears from keratoconus compared with normal subjects. The activity of tear gelatinases (69.6 ± 22.2 FIU) and collagenases (5.7 ± 3.3 FIU) in the collagen cross-linked group was not significantly different compared with either keratoconus or normals. Tears of people with keratoconus had 1.9 times higher levels of proteolytic activity and over expression of several MMPs and cytokines compared with tears from controls. Further investigations are required to study the possible implications of these changes and whether they can be used to monitor disease progression or determine the success of corneal collagen cross-linking. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

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.

The synthesis and coupling of photoreactive collagen-based peptides to restore integrin reactivity to an inert substrate, chemically-crosslinked collagen

Science.gov (United States)

Malcor, Jean-Daniel; Bax, Daniel; Hamaia, Samir W.; Davidenko, Natalia; Best, Serena M.; Cameron, Ruth E.; Farndale, Richard W.; Bihan, Dominique

2016-01-01

Collagen is frequently advocated as a scaffold for use in regenerative medicine. Increasing the mechanical stability of a collagen scaffold is widely achieved by cross-linking using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). However, this treatment consumes the carboxylate-containing amino acid sidechains that are crucial for recognition by the cell-surface integrins, abolishing cell adhesion. Here, we restore cell reactivity to a cross-linked type I collagen film by covalently linking synthetic triple-helical peptides (THPs), mimicking the structure of collagen. These THPs are ligands containing an active cell-recognition motif, GFOGER, a high-affinity binding site for the collagen-binding integrins. We end-stapled peptide strands containing GFOGER by coupling a short diglutamate-containing peptide to their N-terminus, improving the thermal stability of the resulting THP. A photoreactive Diazirine group was grafted onto the end-stapled THP to allow covalent linkage to the collagen film upon UV activation. Such GFOGER-derivatized collagen films showed restored affinity for the ligand-binding I domain of integrin α2β1, and increased integrin-dependent cell attachment and spreading of HT1080 and Rugli cell lines, expressing integrins α2β1 and α1β1, respectively. The method we describe has wide application, beyond collagen films or scaffolds, since the photoreactive diazirine will react with many organic carbon skeletons. PMID:26854392

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...

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

Directory of Open Access Journals (Sweden)

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.

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-lin...

Construction of a human corneal stromal equivalent with non-transfected human corneal stromal cells and acellular porcine corneal stromata.

Science.gov (United States)

Diao, Jin-Mei; Pang, Xin; Qiu, Yue; Miao, Ying; Yu, Miao-Miao; Fan, Ting-Jun

2015-03-01

A tissue-engineered human corneal stroma (TE-HCS) has been developed as a promising equivalent to the native corneal stroma for replacement therapy. However, there is still a crucial need to improve the current approaches to render the TE-HCS equivalent more favorable for clinical applications. At the present study, we constructed a TE-HCS by incubating non-transfected human corneal stromal (HCS) cells in an acellular porcine corneal stromata (aPCS) scaffold in 20% fetal bovine serum supplemented DMEM/F12 (1:1) medium at 37 °C with 5% CO2in vitro. After 3 days of incubation, the constructed TE-HCS had a suitable tensile strength for transplantation, and a transparency that is comparable to native cornea. The TE-HCS had a normal histological structure which contained regularly aligned collagen fibers and differentiated HCS cells with positive expression of marker and functional proteins, mimicking a native HCS. After transplantation into rabbit models, the TE-HCS reconstructed normal corneal stroma in vivo and function well in maintaining corneal clarity and thickness, indicating that the completely biological TE-HCS could be used as a HCS equivalent. The constructed TE-HCS has promising potentials in regenerative medicine and treatment of diseases caused by corneal stromal disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

A Comparative Study of Vertebrate Corneal Structure: The Evolution of a Refractive Lens.

Science.gov (United States)

Winkler, Moritz; Shoa, Golroxan; Tran, Stephanie T; Xie, Yilu; Thomasy, Sarah; Raghunathan, Vijay K; Murphy, Christopher; Brown, Donald J; Jester, James V

2015-04-01

Although corneal curvature plays an important role in determining the refractive power of the vertebrate eye, the mechanisms controlling corneal shape remain largely unknown. To address this question, we performed a comparative study of vertebrate corneal structure to identify potential evolutionarily based changes that correlate with the development of a corneal refractive lens. Nonlinear optical (NLO) imaging of second-harmonic-generated (SHG) signals was used to image collagen and three-dimensionally reconstruct the lamellar organization in corneas from different vertebrate clades. Second-harmonic-generated images taken normal to the corneal surface showed that corneal collagen in all nonmammalian vertebrates was organized into sheets (fish and amphibians) or ribbons (reptiles and birds) extending from limbus to limbus that were oriented nearly orthogonal (ranging from 77.7°-88.2°) to their neighbors. The slight angular offset (2°-13°) created a rotational pattern that continued throughout the full thickness in fish and amphibians and to the very posterior layers in reptiles and birds. Interactions between lamellae were limited to "sutural" fibers in cartilaginous fish, and occasional lamellar branching in fish and amphibians. There was a marked increase in lamellar branching in higher vertebrates, such that birds ≫ reptiles > amphibians > fish. By contrast, mammalian corneas showed a nearly random collagen fiber organization with no orthogonal, chiral pattern. Our data indicate that nonmammalian vertebrate corneas share a common orthogonal collagen structural organization that shows increased lamellar branching in higher vertebrate species. Importantly, mammalian corneas showed a different structural organization, suggesting a divergent evolutionary background.

New composite materials prepared by calcium phosphate precipitation in chitosan/collagen/hyaluronic acid sponge cross-linked by EDC/NHS.

Science.gov (United States)

Kaczmarek, B; Sionkowska, A; Kozlowska, J; Osyczka, A M

2018-02-01

Nowadays, fabrication of composite materials based on biopolymers is a rising field due to potential for bone repair and tissue engineering application. Blending of different biopolymers and incorporation of inorganic particles in the blend can lead to new materials with improved physicochemical properties and biocompatibility. In this work 3D porous structures called scaffolds based on chitosan, collagen and hyaluronic acid were obtained through the lyophilization process. Scaffolds were cross-linked by EDC/NHS. Infrared spectra for the materials were made, the percentage of swelling, scaffolds porosity and density, mechanical parameters, thermal stability were studied. Moreover, the scaffolds were used as matrixes for the calcium phosphate in situ precipitation. SEM images were taken and EDX analysis was carried out for calcium and phosphorous content determination in the scaffold. In addition, the adhesion and proliferation of human osteosarcoma SaOS-2 cells was examined on obtained scaffolds. The results showed that the properties of 3D composites cross-linked by EDC/NHS were altered after the addition of 1, 2 and 5% hyaluronic acid. Mechanical parameters, thermal stability and porosity of scaffolds were improved. Moreover, calcium and phosphorous were found in each kind of scaffold. SEM images showed that the precipitation was homogeneously carried in the whole volume of samples. Attachment of SaOS-2 cells to all modified materials was better compared to unmodified control and proliferation of these cells was markedly increased on scaffolds with precipitated calcium phosphate. Obtained materials can provide the support useful in tissue engineering and regenerative medicine. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantitative Assessment of Ultrastructure and Light Scatter in Mouse Corneal Debridement Wounds

Science.gov (United States)

Boote, Craig; Du, Yiqin; Morgan, Sian; Harris, Jonathan; Kamma-Lorger, Christina S.; Hayes, Sally; Lathrop, Kira L.; Roh, Danny S.; Burrow, Michael K.; Hiller, Jennifer; Terrill, Nicholas J.; Funderburgh, James L.; Meek, Keith M.

2012-01-01

Purpose. The mouse has become an important wound healing model with which to study corneal fibrosis, a frequent complication of refractive surgery. The aim of the current study was to quantify changes in stromal ultrastructure and light scatter that characterize fibrosis in mouse corneal debridement wounds. Methods. Epithelial debridement wounds, with and without removal of basement membrane, were produced in C57BL/6 mice. Corneal opacity was measured using optical coherence tomography, and collagen diameter and matrix order were quantified by x-ray scattering. Electron microscopy was used to visualize proteoglycans. Quantitative PCR (Q-PCR) measured mRNA transcript levels for several quiescent and fibrotic markers. Results. Epithelial debridement without basement membrane disruption produced a significant increase in matrix disorder at 8 weeks, but minimal corneal opacity. In contrast, basement membrane penetration led to increases in light scatter, matrix disorder, and collagen diameter, accompanied by the appearance of abnormally large proteoglycans in the subepithelial stroma. This group also demonstrated upregulation of several quiescent and fibrotic markers 2 to 4 weeks after wounding. Conclusions. Fibrotic corneal wound healing in mice involves extensive changes to collagen and proteoglycan ultrastructure, consistent with deposition of opaque scar tissue. Epithelial basement membrane penetration is a deciding factor determining the degree of ultrastructural changes and resulting opacity. PMID:22467580

[Riboflavin photoprotection with cross-linking effect in photorefractive ablation of the cornea].

Science.gov (United States)

Kornilovskiy, I M; Sultanova, A I; Burtsev, A A

2016-01-01

Photorefractive ablation is inevitably accompanied by oxidative stress of the cornea and weakening of its biomechanical and photoprotective properties. To validate the expediency of riboflavin use in photorefractive ablation for photoprotection of the cornea and cross-linking. The effects of riboflavin use in photorefractive ablation was first studied in a series of in vitro and in vivo experiments performed on 56 eyes of 28 rabbits, and then on 232 eyes of 142 patients with different degrees of myopia. Biomechanical testing of corneal samples was performed with Zwick/RoellВZ 2.5/TN1S tensile-testing machine. Transepithelial photorefractive keratectomy (TransPRK) and femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) were performed on Wavelight-Allegretto200, MEL-80, and WaveLight-EX500 excimer laser systems and also VisuMax and WaveLight-FS200 femtosecond lasers. For preliminary examinations, an appropriate set of diagnostic tools was used. In vivo experiments have proved that, in the absence of conservative therapy, riboflavin is able to produce both photoprotective and cross-linking effects to the cornea. Corneal syndrome was thus reduced and re-epithelialization after TransPRK accelerated. Biomechanical testing of corneal samples revealed an increase in tolerated load from 12.9±1.4 N to 18.3±1.2 N (p=0.0002) and tensile strength from 8.6±1.7 MPa to 12.4±1.7 MPa (p=0.007). Clinical studies conducted in a group of patients with mild to moderate myopia have also confirmed the photoprotective effect of riboflavin at months 1-12 after TransPRK. There were no significant differences in uncorrected visual acuity (ranged from 0.80±0.16 to 0.85±0.15) and corrected visual acuity at baseline (0.83±0.14). Evaluation of the optical and refractive effect achieved after Femto-LASIK with riboflavin photoprotection in the fellow eye has shown that this technique is not inferior to the traditional one as to its refractive accuracy, but provides better

Cyclophilin B Deficiency Causes Abnormal Dentin Collagen Matrix.

Science.gov (United States)

Terajima, Masahiko; Taga, Yuki; Cabral, Wayne A; Nagasawa, Masako; Sumida, Noriko; Hattori, Shunji; Marini, Joan C; Yamauchi, Mitsuo

2017-08-04

Cyclophilin B (CypB) is an endoplasmic reticulum-resident protein that regulates collagen folding, and also contributes to prolyl 3-hydroxylation (P3H) and lysine (Lys) hydroxylation of collagen. In this study, we characterized dentin type I collagen in CypB null (KO) mice, a model of recessive osteogenesis imperfecta type IX, and compared to those of wild-type (WT) and heterozygous (Het) mice. Mass spectrometric analysis demonstrated that the extent of P3H in KO collagen was significantly diminished compared to WT/Het. Lys hydroxylation in KO was significantly diminished at the helical cross-linking sites, α1/α2(I) Lys-87 and α1(I) Lys-930, leading to a significant increase in the under-hydroxylated cross-links and a decrease in fully hydroxylated cross-links. The extent of glycosylation of hydroxylysine residues was, except α1(I) Lys-87, generally higher in KO than WT/Het. Some of these molecular phenotypes were distinct from other KO tissues reported previously, indicating the dentin-specific control mechanism through CypB. Histological analysis revealed that the width of predentin was greater and irregular, and collagen fibrils were sparse and significantly smaller in KO than WT/Het. These results indicate a critical role of CypB in dentin matrix formation, suggesting a possible association between recessive osteogenesis imperfecta and dentin defects that have not been clinically detected.

The roles of TGF-beta1 gene transfer on collagen formation during Achilles tendon healing.

Science.gov (United States)

Hou, Yu; Mao, ZeBing; Wei, XueLei; Lin, Lin; Chen, LianXu; Wang, HaiJun; Fu, Xin; Zhang, JiYing; Yu, ChangLong

2009-05-29

Collagen content and cross-linking are believed to be major determinants of tendon structural integrity and function. The current study aimed to investigate the effects of transforming growth factor (TGF)-beta1 on the collagen content and cross-linking of Achilles tendons, and on the histological and biomechanical changes occurring during Achilles tendon healing in rabbits. Bone marrow-derived mesenchymal stem cells (BMSCs) transfected with the TGF-beta1 gene were surgically implanted into experimentally injured Achilles tendons. Collagen proteins were identified by immunohistochemical staining and fiber bundle accumulation was revealed by Sirius red staining. Achilles tendons treated with TGF-beta1-transfected BMSCs showed higher concentrations of collagen I protein, more rapid matrix remodeling, and larger fiber bundles. Thus TGF-beta1 can promote mechanical strength in healing Achilles tendons by regulating collagen synthesis, cross-link formation, and matrix remodeling.

Corneal Collagen Crosslinking Combined with Phototherapeutic Keratectomy and Photorefractive Keratectomy for Corneal Ectasia after Laser in situ Keratomileusis.

Science.gov (United States)

Zhu, Wei; Han, Yunfei; Cui, Changxia; Xu, Wenwen; Wang, Xuan; Dou, Xiaoxiao; Xu, Linlin; Xu, Yanyun; Mu, Guoying

2018-01-01

The aim of this study was to analyze the effects of corneal crosslinking (CXL) combined with phototherapeutic keratectomy (PTK) and photorefractive keratectomy (PRK) in halting the progression and improving the visual function of corneal ectasia after laser in situ keratomileusis (LASIK). PTK-PRK-CXL was performed on 14 eyes of 14 patients who developed corneal ectasia after LASIK. The visual acuity, spherical refraction and cylinder, corneal topography indices, thinnest corneal thickness (TCT), and endothelial cell count were evaluated at baseline and at 1, 3, 6, and 12 months postoperatively. The mean uncorrected visual acuity improved significantly from 0.64 ± 0.36 logMAR preoperatively to 0.19 ± 0.12 logMAR at 12 months of follow-up (p 0.05) beyond 6 months after treatment. PTK-PRK-CXL is a promising procedure to halt the progression of post-LASIK keratectasia with significant visual quality improvement. © 2018 S. Karger AG, Basel.

Shear bond strength of composite to deep dentin after treatment with two different collagen cross-linking agents at varying time intervals.

Science.gov (United States)

Srinivasulu, S; Vidhya, S; Sujatha, M; Mahalaxmi, S

2012-01-01

This in vitro study evaluated the shear bond strength of composite resin to deep dentin using a total etch adhesive after treatment with two collagen cross-linking agents at varying time intervals. Thirty freshly extracted human maxillary central incisors were sectioned longitudinally into equal mesial and distal halves (n=60). The proximal deep dentin was exposed, maintaining a remaining dentin thickness (RDT) of approximately 1 mm. The specimens were randomly divided into three groups based on the surface treatment of dentin prior to bonding as follows: group I (n=12, control): no prior dentin surface treatment; group II (n=24): dentin surface pretreated with 10% sodium ascorbate; and group III (n=24): dentin surface pretreated with 6.5% proanthocyanidin. Groups II and III were further subdivided into two subgroups of 12 specimens each, based on the pretreatment time of five minutes (subgroup A) and 10 minutes (subgroup B). Shear bond strength of the specimens was tested with a universal testing machine, and the data were statistically analyzed. Significantly higher shear bond strength to deep dentin was observed in teeth treated with 10% sodium ascorbate (group II) and 6.5% proanthocyanidin (group III) compared to the control group (group I). Among the collagen cross-linkers used, specimens treated with proanthocyanidin showed significantly higher shear bond strength values than those treated with sodium ascorbate. No significant difference was observed between the five-minute and 10-minute pretreatment times in groups II and III. It can be concluded that dentin surface pretreatment with both 10% sodium ascorbate and 6.5% proanthocyanidin resulted in significant improvement in bond strength of resin composite to deep dentin.

Collagen organization in the chicken cornea and structural alterations in the retinopathy, globe enlarged (rge) phenotype--an X-ray diffraction study.

Science.gov (United States)

Boote, Craig; Hayes, Sally; Jones, Simon; Quantock, Andrew J; Hocking, Paul M; Inglehearn, Chris F; Ali, Manir; Meek, Keith M

2008-01-01

An investigation into the collagenous structure of the mature avian cornea is presented. Wide-angle X-ray diffraction is employed to assess collagen organization in 9-month-old chicken corneas. The central 2-4mm corneal region features a preponderance of fibrils directed along the superior-inferior and nasal-temporal orthogonal meridians. More peripherally the orientation of fibrils alters in favor of a predominantly tangential arrangement. The chicken cornea appears to be circumscribed by an annulus of fibrils that extends into the limbus. The natural arrangement of collagen in the chicken cornea is discussed in relation to corneal shape and the mechanical requirements of avian corneal accommodation. Equivalent data are also presented from age-matched blind chickens affected with the retinopathy, globe enlarged (rge) mutation, characterized by an abnormally thick and flat cornea. The data indicate considerable realignment and redistribution of collagen lamellae in the peripheral rge cornea. In contrast to normal chickens, no obvious tangential collagen alignment was evident in the periphery of rge corneas. In mammals, the presence of a limbal fibril annulus is believed to be important in corneal shape preservation. We postulate that corneal flattening in rge chickens may be related to biomechanical changes brought about by an alteration in collagen arrangement at the corneal periphery.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

Physiochemical properties and resorption progress of porcine skin-derived collagen membranes: In vitro and in vivo analysis.

Science.gov (United States)

An, Yin-Zhe; Kim, You-Kyoung; Lim, Su-Min; Heo, Yeong-Ku; Kwon, Mi-Kyung; Cha, Jae-Kook; Lee, Jung-Seok; Jung, Ui-Won; Choi, Seong-Ho

2018-03-30

The aim of the present study was to evaluate the physiochemical properties and resorption progress of two cross-linked, porcine skin-derived collagen membranes and compare their features with those of a membrane without cross-linking (Bio-Gide ® [BG], Geistlich Biomaterials, Wolhusen, Switzerland). Three porcine skin-derived collagen membranes, dehydrothermally (DHT) cross-linked (experimental), DHT and 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide (DHT/EDC) cross-linked (experimental) and BG were investigated for their morphology, enzyme resistance, and tensile strength in vitro and biodegradation in vivo. DHT and DHT/EDC membranes exhibited irregular, interconnected macro- and micropores that formed a 3D mesh, whereas BG exhibited individual collagen fibrils interlaced to form coarse collagen strands. In enzyme resistance and tensile strength tests, DHT and DHT/EDC membranes demonstrated good resistance and mechanical properties compared with BG. In vivo, all three membranes were well integrated into the surrounding connective tissue. Thus, the DHT membrane exhibited its potential as a barrier membrane for guided bone and tissue regeneration.

Bone Collagen: New Clues to its Mineralization Mechanism From Recessive Osteogenesis Imperfecta

Science.gov (United States)

Eyre, David R.; Ann Weis, Mary

2013-01-01

Until 2006 the only mutations known to cause osteogenesis imperfecta (OI) were in the two genes coding for type I collagen chains. These dominant mutations affecting the expression or primary sequence of collagen α1(I) and α2(I) chains account for over 90% of OI cases. Since then a growing list of mutant genes causing the 5–10% of recessive cases has rapidly emerged. They include CRTAP, LEPRE1 and PPIB, which encode three proteins forming the prolyl 3-hydroxylase complex; PLOD2 and FKBP10, which encode respectively lysyl hydroxylase 2 and a foldase required for its activity in forming mature cross-links in bone collagen; SERPIN H1, which encodes the collagen chaperone HSP47; SERPIN F1, which encodes pigment epithelium-derived factor required for osteoid mineralization; and BMP1, which encodes the type I procollagen C-propeptidase. All cause fragile bone in infancy, which can include over-mineralization or under-mineralization defects as well as abnormal collagen post-translational modifications. Consistently both dominant and recessive variants lead to abnormal cross-linking chemistry in bone collagen. These recent discoveries strengthen the potential for a common pathogenic mechanism of misassembled collagen fibrils. Of the new genes identified, eight encode proteins required for collagen post-translational modification, chaperoning of newly synthesized collagen chains into native molecules or transport through the endoplasmic reticulum and Golgi for polymerization, cross-linking and mineralization. In reviewing these findings, we conclude that a common theme is emerging in the pathogenesis of brittle bone disease of mishandled collagen assembly with important insights on post-translational features of bone collagen that have evolved to optimize it as a biomineral template. PMID:23508630

Overhydroxylation of Lysine of Collagen Increases Uterine Fibroids Proliferation: Roles of Lysyl Hydroxylases, Lysyl Oxidases, and Matrix Metalloproteinases

Directory of Open Access Journals (Sweden)

Marwa Kamel

2017-01-01

Full Text Available The role of the extracellular matrix (ECM in uterine fibroids (UF has recently been appreciated. Overhydroxylation of lysine residues and the subsequent formation of hydroxylysylpyridinoline (HP and lysylpyridinoline (LP cross-links underlie the ECM stiffness and profoundly affect tumor progression. The aim of the current study was to investigate the relationship between ECM of UF, collagen and collagen cross-linking enzymes [lysyl hydroxylases (LH and lysyl oxidases (LOX], and the development and progression of UF. Our results indicated that hydroxyl lysine (Hyl and HP cross-links are significantly higher in UF compared to the normal myometrial tissues accompanied by increased expression of LH (LH2b and LOX. Also, increased resistance to matrix metalloproteinases (MMP proteolytic degradation activity was observed. Furthermore, the extent of collagen cross-links was positively correlated with the expression of myofibroblast marker (α-SMA, growth-promoting markers (PCNA; pERK1/2; FAKpY397; Ki-67; and Cyclin D1, and the size of UF. In conclusion, our study defines the role of overhydroxylation of collagen and collagen cross-linking enzymes in modulating UF cell proliferation, differentiation, and resistance to MMP. These effects can establish microenvironment conducive for UF progression and thus represent potential target treatment options of UF.

Collagen turnover after tibial fractures

DEFF Research Database (Denmark)

Joerring, S; Krogsgaard, M; Wilbek, H

1994-01-01

Collagen turnover after tibial fractures was examined in 16 patients with fracture of the tibial diaphysis and in 8 patients with fracture in the tibial condyle area by measuring sequential changes in serological markers of turnover of types I and III collagen for up to 26 weeks after fracture....... The markers were the carboxy-terminal extension peptide of type I procollagen (PICP), the amino-terminal extension peptide of type III procollagen (PIIINP), and the pyridinoline cross-linked carboxy-terminal telopeptide of type I collagen (ICTP). The latter is a new serum marker of degradation of type I...... collagen. A group comparison showed characteristic sequential changes in the turnover of types I and III collagen in fractures of the tibial diaphysis and tibial condyles. The turnover of type III collagen reached a maximum after 2 weeks in both groups. The synthesis of type I collagen reached a maximum...

Manipulation of in vitro collagen matrix architecture for scaffolds of improved physiological relevance

Science.gov (United States)

Hapach, Lauren A.; VanderBurgh, Jacob A.; Miller, Joseph P.; Reinhart-King, Cynthia A.

2015-12-01

Type I collagen is a versatile biomaterial that is widely used in medical applications due to its weak antigenicity, robust biocompatibility, and its ability to be modified for a wide array of applications. As such, collagen has become a major component of many tissue engineering scaffolds, drug delivery platforms, and substrates for in vitro cell culture. In these applications, collagen constructs are fabricated to recapitulate a diverse set of conditions. Collagen fibrils can be aligned during or post-fabrication, cross-linked via numerous techniques, polymerized to create various fibril sizes and densities, and copolymerized into a wide array of composite scaffolds. Here, we review approaches that have been used to tune collagen to better recapitulate physiological environments for use in tissue engineering applications and studies of basic cell behavior. We discuss techniques to control fibril alignment, methods for cross-linking collagen constructs to modulate stiffness, and composite collagen constructs to better mimic physiological extracellular matrix.

Light-induced cross-linking and post-cross-linking modification of polyglycidol.

Science.gov (United States)

Marquardt, F; Bruns, M; Keul, H; Yagci, Y; Möller, M

2018-02-08

The photoinduced radical generation process has received renewed interest due to its economic and ecological appeal. Herein the light-induced cross-linking of functional polyglycidol and its post-cross-linking modification are presented. Linear polyglycidol was first functionalized with a tertiary amine in a two-step reaction. Dimethylaminopropyl functional polyglycidol was cross-linked in a UV-light mediated reaction with camphorquinone as a type II photoinitiator. The cross-linked polyglycidol was further functionalized by quaternization with various organoiodine compounds. Aqueous dispersions of the cross-linked polymers were investigated by means of DLS and zeta potential measurements. Polymer films were evaluated by DSC and XPS.

Efectividad del crosslinking del colágeno corneal en el tratamiento del queratocono Effectiveness of the corneal collagen crosslinking in the treatment of keratoconus

Directory of Open Access Journals (Sweden)

Madelyn Jareño Ochoa

2012-12-01

Full Text Available Objetivo: determinar la efectividad del tratamiento de crosslinking del colágeno corneal en pacientes con queratocono progresivo en el Instituto Cubano de Oftalmología "Ramón Pando Ferrer". Métodos: estudio descriptivo, retrospectivo, en 30 pacientes (30 ojos con queratocono progresivo que se les realizó el crosslinking del colágeno corneal. Se recogieron los datos en el preoperatorio, al mes, 3 meses, 6 meses y al año. Las variables estudiadas fueron: edad, sexo, estadio del queratocono, mejor agudeza visual corregida, equivalente esférico, queratometría máxima topográfica, algunos índices topográficos de diagnóstico de queratocono, el coma y la paquimetría óptica. Resultados: predominó el sexo femenino, grupo de 20 a 29 años de edad y el estadio II del queratocono. La mejor agudeza visual corregida se incrementa de 0,65 ±0,25 en el preoperatorio a 0,74 ±0,23 al año. El equivalente esférico disminuye de -7,25 ±4,48 a -6,39 ±4,20 dioptrías. La queratometría máxima topográfica de 50,76 ±3,81 a 49,26 ±3,31 dioptrías. Los índices topográficos disminuyeron sus valores. El error cuadrático medio del coma se modificó de 0,59 ±0,43 a 0,45 ±0,32 micras. La paquimetría óptica del centro de la pupila varió de 494 ±39,75 a 466 ±44,24 micras y la de la posición más delgada de 484 ±45,86 a 450 ±51,12 micras. Todos los resultados al año mostraron diferencias estadísticamente significativas. Conclusiones: el crosslinking es un tratamiento efectivo para el queratocono progresivo que permite detener la evolución de esta enfermedad ectásica.Objective: to determine the effectiveness of corneal collagen crosslinking in patients with progressive keratoconus performed at “Ramón Pando Ferrer” Cuban Institute of Ophthalmology. Methods: a retrospective and descriptive study was performed in 30 patients (30 eyes with progressive keratoconus, who underwent the corneal collagen crosslinking. Data were collected

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

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)

Glutaraldehyde-induced remineralization improves the mechanical properties and biostability of dentin collagen

Energy Technology Data Exchange (ETDEWEB)

Chen, Chaoqun; Mao, Caiyun; Sun, Jian; Chen, Yi; Wang, Wei [Department of Stomatology, The First Affiliated Hospital, College of Medicine, Zhejiang University (China); Pan, Haihua; Tang, Ruikang [Centre for Biopathways and Biomaterials, Department of Chemistry, Zhejiang University (China); Gu, Xinhua [Department of Stomatology, The First Affiliated Hospital, College of Medicine, Zhejiang University (China)

2016-10-01

The purpose of this study was to induce a biomimetic remineralization process by using glutaraldehyde (GA) to reconstruct the mechanical properties and biostability of demineralized collagen. Demineralized dentin disks (35% phosphoric acid, 10 s) were pretreated with a 5% GA solution for 3 min and then cultivated in a calcium phosphate remineralization solution. The remineralization kinetics and superstructure of the remineralization layer were evaluated by Raman spectroscopy, transmission electron microscopy, scanning electron microscopy and nanoindentation tests. The biostability was examined by enzymatic degradation experiments. A significant difference was found in dentin remineralization process between dentin with and without GA pretreating. GA showed a specific affinity to dentin collagen resulting in the formation of a cross-linking superstructure. GA pretreating could remarkably shorten remineralization time from 7 days to 2 days. The GA-induced remineralized collagen fibrils were well encapsulated by newly formed hydroxyapatite mineral nanocrystals. With the nano-hydroxyapatite coating, both the mechanical properties (elastic modulus and hardness) and the biostability against enzymatic degradation of the collagen were significantly enhanced, matching those of natural dentin. The results indicated that GA cross-linking of dentin collagen could promote dentin biomimetic remineralization, resulting in an improved mechanical properties and biostability. It may provide a promising tissue-engineering technology for dentin repair. - Highlights: • GA cross-linking can promote the remineralization kinetics of dentin collagen. • GA-induced remineralization can reshape the demineralized dentin collagen layer. • The GA-induced remineralization enhances the degradation resistance of collagen. • GA-induced remineralization provides a new approach to improve bonding durability.

Glutaraldehyde-induced remineralization improves the mechanical properties and biostability of dentin collagen

International Nuclear Information System (INIS)

Chen, Chaoqun; Mao, Caiyun; Sun, Jian; Chen, Yi; Wang, Wei; Pan, Haihua; Tang, Ruikang; Gu, Xinhua

2016-01-01

The purpose of this study was to induce a biomimetic remineralization process by using glutaraldehyde (GA) to reconstruct the mechanical properties and biostability of demineralized collagen. Demineralized dentin disks (35% phosphoric acid, 10 s) were pretreated with a 5% GA solution for 3 min and then cultivated in a calcium phosphate remineralization solution. The remineralization kinetics and superstructure of the remineralization layer were evaluated by Raman spectroscopy, transmission electron microscopy, scanning electron microscopy and nanoindentation tests. The biostability was examined by enzymatic degradation experiments. A significant difference was found in dentin remineralization process between dentin with and without GA pretreating. GA showed a specific affinity to dentin collagen resulting in the formation of a cross-linking superstructure. GA pretreating could remarkably shorten remineralization time from 7 days to 2 days. The GA-induced remineralized collagen fibrils were well encapsulated by newly formed hydroxyapatite mineral nanocrystals. With the nano-hydroxyapatite coating, both the mechanical properties (elastic modulus and hardness) and the biostability against enzymatic degradation of the collagen were significantly enhanced, matching those of natural dentin. The results indicated that GA cross-linking of dentin collagen could promote dentin biomimetic remineralization, resulting in an improved mechanical properties and biostability. It may provide a promising tissue-engineering technology for dentin repair. - Highlights: • GA cross-linking can promote the remineralization kinetics of dentin collagen. • GA-induced remineralization can reshape the demineralized dentin collagen layer. • The GA-induced remineralization enhances the degradation resistance of collagen. • GA-induced remineralization provides a new approach to improve bonding durability.

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

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......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...

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

Directory of Open Access Journals (Sweden)

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.

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

Science.gov (United States)

Ng, Alex L K; Chan, Tommy C Y; Cheng, George P M; Jhanji, Vishal; Ye, Cong; Woo, Victor C P; Lai, Jimmy S M

2016-01-01

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 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 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.

Occlusal loading and cross-linking effects on dentin collagen degradation in physiological conditions.

Science.gov (United States)

Turco, Gianluca; Frassetto, Andrea; Fontanive, Luca; Mazzoni, Annalisa; Cadenaro, Milena; Di Lenarda, Roberto; Tay, Franklin R; Pashley, David H; Breschi, Lorenzo

2016-02-01

This study evaluated the ability of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) to improve the stability of demineralized dentin collagen matrices when subjected to mechanical cycling by means of Chewing Simulation (CS). Demineralized dentin disks were randomly assigned to four groups (N=4): (1) immersion in artificial saliva at 37°C for 30 days; (2) pre-treatment with 0.5 M EDC for 60 s, then stored as in Group 1; (3) CS challenge (50 N occlusal load, 30 s occlusal time plus 30 s with no load, for 30 days); (4) pre-treatment with 0.5 M EDC as in Group 2 and CS challenge as in Group 3. Collagen degradation was evaluated by sampling storage media for ICTP and CTX telopeptides. EDC treated specimens showed no significant telopeptides release, irrespective of the aging method. Cyclic stressing of EDC-untreated specimens caused significantly higher ICTP release at day 1, compared to static storage, while by days 3 and 4, the ICTP release in the cyclic group fell significantly below the static group, and then remained undetectable from 5 to 30 days. CTX release in the cyclic groups, on EDC-untreated control specimens was always lower than in the static group in days 1-4, and then fell to undetectable for 30 days. This study showed that chewing stresses applied to control untreated demineralized dentin increased degradation of collagen in terms of CTX release, while collagen crosslinking agents may prevent dentin collagen degradation, irrespective of simulated occlusal function. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Corneal structure and transparency

Science.gov (United States)

Meek, Keith M.; Knupp, Carlo

2015-01-01

The corneal stroma plays several pivotal roles within the eye. Optically, it is the main refracting lens and thus has to combine almost perfect transmission of visible light with precise shape, in order to focus incoming light. Furthermore, mechanically it has to be extremely tough to protect the inner contents of the eye. These functions are governed by its structure at all hierarchical levels. The basic principles of corneal structure and transparency have been known for some time, but in recent years X-ray scattering and other methods have revealed that the details of this structure are far more complex than previously thought and that the intricacy of the arrangement of the collagenous lamellae provides the shape and the mechanical properties of the tissue. At the molecular level, modern technologies and theoretical modelling have started to explain exactly how the collagen fibrils are arranged within the stromal lamellae and how proteoglycans maintain this ultrastructure. In this review we describe the current state of knowledge about the three-dimensional stromal architecture at the microscopic level, and about the control mechanisms at the nanoscopic level that lead to optical transparency. PMID:26145225

Dermal regeneration in native non-cross-linked collagen sponges with different extracellular matrix molecules

NARCIS (Netherlands)

de Vries, H. J.; Middelkoop, E.; Mekkes, J. R.; Dutrieux, R. P.; Wildevuur, C. H.; Westerhof, H.

1994-01-01

Collagenous dermal templates can prevent scarring and wound contraction in the healing of full-thickness defects. In a porcine wound model, full-thickness wounds were substituted by reconstituted and native collagen sponges in combination with autologous split-skin mesh grafts and covered with a

Altered corneal stromal matrix organization is associated with mucopolysaccharidosis I, III and VI.

Science.gov (United States)

Alroy, J; Haskins, M; Birk, D E

1999-05-01

The presence of cloudy corneas is a prominent feature of mucopolysaccharidosis (MPS) types I and VI, but not MPS IIIA or IIIB. The cause of corneal cloudiness in MPS I and VI is speculative. Transparency of the cornea is dependent on the uniform diameter and the regular spacing and arrangement of the collagen fibrils within the stroma. Alterations in the spacing of collagen fibrils in a variety of conditions including corneal edema, scars, and macular corneal dystrophy is clinically manifested as corneal opacity. The purpose of this study was to compare the structural organization of the stromal extracellular matrix of normal corneas with that of MPS corneas. The size and arrangement of collagen fibrils in cloudy corneas from patients with MPS I were examined. The alterations observed were an increased mean fibril diameter with a broader distribution in the MPS corneas. The MPS I corneas also had altered fibril spacing and more irregular packing compared with normal control corneas. The clear corneas of patients with MPS IIIA and IIIB also showed increases in mean fibril diameter and fibril spacing. However, there was less variation indicating more regularity than seen in MPS I. In addition, corneas from cat models of certain MPS were compared to the human corneas. Cats with MPS I and VI, as well as normal control cats, were examined. Structural alterations comparable to those seen in human MPS corneas were seen in MPS I and VI cats relative to normal clear corneas. The findings suggest that cloudy corneas in MPS I and VI are in part a consequence of structural alterations in the corneal stroma, including abnormal spacing, size, and arrangement of collagen fibrils. Copyright 1999 Academic Press.

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. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Applications of biomaterials in corneal wound healing

Directory of Open Access Journals (Sweden)

I-Lun Tsai

2015-04-01

Full Text Available Disease affecting the cornea is a common cause of blindness worldwide. To date, the amniotic membrane (AM is the most widely used clinical method for cornea regeneration. However, donor-dependent differences in the AM may result in variable clinical outcomes. To overcome this issue, biomaterials are currently under investigation for corneal regeneration in vitro and in vivo. In this article, we highlight the recent advances in hydrogels, bioengineered prosthetic devices, contact lenses, and drug delivery systems for corneal regeneration. In clinical studies, the therapeutic effects of biomaterials, including fibrin and collagen-based hydrogels and silicone contact lenses, have been demonstrated in damaged cornea. The combination of cells and biomaterials may provide potential treatment in corneal wound healing in the future.

Clinical evaluation and induced corneal vascularization study by native and anionic collagen membranes in rabbits corneas Avaliação clínica e estudo da vascularização corneal induzida pelas membranas de colágeno nativo e aniônico em córneas de coelhos

Directory of Open Access Journals (Sweden)

Thaís Eliane Binotto

2009-12-01

Full Text Available PURPOSE: To evaluate the corneal vascularization (CV and the clinical aspects induced by interlamellar graft with native (NCM and anionic (ACM collagen membranes in rabbits corneas. METHODS: An interlamellar graft with a 0.25 x 0.25 cm NCM (group 1 or ACM (group 2 fragment was performed in the right eye (treated eye. In the left eye, an estromal tunnel was done (control eye. Sixteen rabbits were used, and they were subdivided into two experimental groups of eight animals each. The clinical evaluation was performed at the 1st, 3rd, 7th, 15th and 30th postoperative days. Corneal vascularization analysis was performed after 30 days by the Images Analizator System Leica Qwin-550®. RESULTS: After 7 days, corneal vascularization was observed at about 2.25 ± 0.71 mm (NCM and at about 1.0 ± 1.69 mm (ACM, respectively, from the limbus in direction to the central cornea. After 15 days, CV increased in both groups (5.25 ± 1.03 mm - NCM; 2.0 ± 2.39 mm - ACM and then progressively decreased until day 30 (2.25 ± 2.10 mm - NCM; 0.75 ± 2.12 mm - ACM. The statistical analysis indicated that the averages of the distances from the limb vessels to the grafts observed after 7 and 15 days had not differed statistically (p=0.17, and after 15 and 30 postoperative days had a tendency to differ statistically (p=0.09. The control eyes did not present any changes. CONCLUSION: The interlamellar graft with native and anionic collagen membranes induced corneal vascularization when applied to rabbit corneas, but anionic collagen membrane induced a smaller corneal vascularization when compared to native collagen membrane. Although further studies are required, the results found in this study demonstrated the usefulness of interlamellar graft with native and anionic collagen membranes in keratoplasties. These membranes consists in one more graft option for the surgical treatment of corneal repair in rabbits and others animals, when other forms of medical and surgical

Secondary cytotoxicity of (crosslinked) dermal sheep collagen during repeated exposure to human fibroblasts

NARCIS (Netherlands)

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

1992-01-01

We investigated commercially available dermal sheep collagen either cross-linked with hexamethylenediisocyanate, or cross-linked with glutaraldehyde. In previous in vitro studies we could discriminate primary, i.e. extractable, and secondary cytotoxicity, due to cell-biomaterial interactions, i.e.

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

Fish collagen is an important panallergen in the Japanese population.

Science.gov (United States)

Kobayashi, Y; Akiyama, H; Huge, J; Kubota, H; Chikazawa, S; Satoh, T; Miyake, T; Uhara, H; Okuyama, R; Nakagawara, R; Aihara, M; Hamada-Sato, N

2016-05-01

Collagen was identified as a fish allergen in early 2000s. Although its allergenic potential has been suggested to be low, risks associated with collagen as a fish allergen have not been evaluated to a greater extent. In this study, we aimed to clarify the importance of collagen as a fish allergen. Our results showed that 50% of Japanese patients with fish allergy had immunoglobulin E (IgE) against mackerel collagen, whereas 44% had IgE against mackerel parvalbumin. IgE inhibition assay revealed high cross-reactivity of mackerel collagen to 22 fish species (inhibition rates: 87-98%). Furthermore, a recently developed allergy test demonstrated that collagen triggered IgE cross-linking on mast cells. These data indicate that fish collagen is an important and very common panallergen in fish consumed in Japan. The high rate of individuals' collagen allergy may be attributable to the traditional Japanese custom of raw fish consumption. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Surface modification of electrospun PLGA scaffold with collagen for bioengineered skin substitutes

Energy Technology Data Exchange (ETDEWEB)

Sadeghi, A.R., E-mail: sadeghi_av@ymail.com [Materials Research Group, Iranian Academic Center for Education, Culture and Research, (ACECR), Mashhad Branch, Mashhad (Iran, Islamic Republic of); Nokhasteh, S. [Materials Research Group, Iranian Academic Center for Education, Culture and Research, (ACECR), Mashhad Branch, Mashhad (Iran, Islamic Republic of); Molavi, A.M. [Materials Research Group, Iranian Academic Center for Education, Culture and Research, (ACECR), Mashhad Branch, Mashhad (Iran, Islamic Republic of); Materials Engineering Department, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Khorsand-Ghayeni, M. [Materials Research Group, Iranian Academic Center for Education, Culture and Research, (ACECR), Mashhad Branch, Mashhad (Iran, Islamic Republic of); Naderi-Meshkin, H. [Stem Cell and Regenerative Medicine Research Department, Iranian Academic Center for Education, Culture and Research (ACECR), Mashhad Branch, Mashhad (Iran, Islamic Republic of); Mahdizadeh, A. [Nanotechnology Institute, University of Sistan and Baluchestan, Zahedan (Iran, Islamic Republic of)

2016-09-01

In skin tissue engineering, surface feature of the scaffolds plays an important role in cell adhesion and proliferation. In this study, non-woven fibrous substrate based on poly (lactic-co-glycolic acid) (PLGA) (75/25) were hydrolyzed in various concentrations of NaOH (0.05 N, 0.1 N, 0.3 N) to increase carboxyl and hydroxyl groups on the fiber surfaces. These functional groups were activated by EDC/NHS to create chemical bonding with collagen. To improve bioactivity, the activated substrates were coated with a collagen solution (2 mg/ml) and cross-linking was carried out using the EDC/NHS in MES buffer. The effectiveness of the method was evaluated by contact angle measurements, porosimetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile and degradation tests as well as in vitro cell attachment and cytotoxicity assays. Cell culture results of human dermal fibroblasts (HDF) and keratinocytes cell line (HaCat) revealed that the cells could attach to the scaffold. Further investigation with MTT assay showed that the cell proliferation of HaCat significantly increases with collagen coating. It seems that sufficient stability of collagen on the surface due to proper chemical bonding and cross-linking has increased the bioactivity of surface remarkably which can be promising for bioengineered skin applications. - Highlights: • Surface activation was carried out by hydrolysis of PLGA fibers. • To improve bioactivity, the activated samples were coated with a collagen solution. • Functional groups were activated by EDC/NHS to create chemical bonding with collagen. • Cross-linking of collagen was carried out using EDC/NHS in MES buffer. • The coated samples exhibited better adhesion and proliferation of epidermal cells.

Surface modification of electrospun PLGA scaffold with collagen for bioengineered skin substitutes

International Nuclear Information System (INIS)

Sadeghi, A.R.; Nokhasteh, S.; Molavi, A.M.; Khorsand-Ghayeni, M.; Naderi-Meshkin, H.; Mahdizadeh, A.

2016-01-01

In skin tissue engineering, surface feature of the scaffolds plays an important role in cell adhesion and proliferation. In this study, non-woven fibrous substrate based on poly (lactic-co-glycolic acid) (PLGA) (75/25) were hydrolyzed in various concentrations of NaOH (0.05 N, 0.1 N, 0.3 N) to increase carboxyl and hydroxyl groups on the fiber surfaces. These functional groups were activated by EDC/NHS to create chemical bonding with collagen. To improve bioactivity, the activated substrates were coated with a collagen solution (2 mg/ml) and cross-linking was carried out using the EDC/NHS in MES buffer. The effectiveness of the method was evaluated by contact angle measurements, porosimetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), tensile and degradation tests as well as in vitro cell attachment and cytotoxicity assays. Cell culture results of human dermal fibroblasts (HDF) and keratinocytes cell line (HaCat) revealed that the cells could attach to the scaffold. Further investigation with MTT assay showed that the cell proliferation of HaCat significantly increases with collagen coating. It seems that sufficient stability of collagen on the surface due to proper chemical bonding and cross-linking has increased the bioactivity of surface remarkably which can be promising for bioengineered skin applications. - Highlights: • Surface activation was carried out by hydrolysis of PLGA fibers. • To improve bioactivity, the activated samples were coated with a collagen solution. • Functional groups were activated by EDC/NHS to create chemical bonding with collagen. • Cross-linking of collagen was carried out using EDC/NHS in MES buffer. • The coated samples exhibited better adhesion and proliferation of epidermal cells.

The evaluation of collagen gel with various connection states by using MRI

International Nuclear Information System (INIS)

Kudo, Hiroki; Mukai, Naoki; Gouping, Chen; Numanno, Tomokazu; Honma, Kazuhiro; Tateishi, Tetsuya; Miyanaga, Yutaka; Miyakawa, Syumpei

2008-01-01

To noninvasively evaluate the connection states of collagen fiber, a characterizing factor of the physical property, is considered to be helpful in the evaluation of cartilage functions. The purpose of this study was to examine how the connection states of collagen influence the MRI parameters by evaluating the collagen gel with various connection states using MRI. MRI was performed to six type I collagen gel samples with various connection status and a water sample. The evaluation parameters included T1 relaxation time, T2 relaxation time, and diffusion coefficient. With regard to gel samples with cross-links, the T2 relaxation time was shortened in proportion to the dose of glutaraldehyde. It is considered that as the glutaraldehyde concentration increases, the distance between protons in water molecules decreases; this is followed by a stronger bipole-bipole interaction, resulting in a shorter T2 relaxation time. The diffusion coefficient for gel samples with cross-links also decreased with increasing glutaraldehyde concentrations. However, gel samples without glutaraldehyde were almost the same as that of the water. This result suggested that the degree of entrapment of water inside the gel samples without cross-links, even when it converted into gel, was found to be nearly equal to that of the free water

Collagen and mineral deposition in rabbit cortical bone during maturation and growth: effects on tissue properties.

Science.gov (United States)

Isaksson, Hanna; Harjula, Terhi; Koistinen, Arto; Iivarinen, Jarkko; Seppänen, Kari; Arokoski, Jari P A; Brama, Pieter A; Jurvelin, Jukka S; Helminen, Heikki J

2010-12-01

We characterized the composition and mechanical properties of cortical bone during maturation and growth and in adult life in the rabbit. We hypothesized that the collagen network develops earlier than the mineralized matrix. Growth was monitored, and the rabbits were euthanized at birth (newborn), and at 1, 3, 6, 9, and 18 months of age. The collagen network was assessed biochemically (collagen content, enzymatic and non-enzymatic cross-links) in specimens from the mid-diaphysis of the tibia and femur and biomechanically (tensile testing) from decalcified whole tibia specimens. The mineralized matrix was analyzed using pQCT and 3-point bend tests from intact femur specimens. The collagen content and the Young's modulus of the collagen matrix increased significantly until the rabbits were 3 months old, and thereafter remained stable. The amount of HP and LP collagen cross-links increased continuously from newborn to 18 months of age, whereas PEN cross-links increased after 6 months of age. Bone mineral density and the Young's modulus of the mineralized bone increased until the rabbits were at least 6 months old. We concluded that substantial changes take place during the normal process of development in both the biochemical and biomechanical properties of rabbit cortical bone. In cortical bone, the collagen network reaches its mature composition and mechanical strength prior to the mineralized matrix. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

A Rare Form of Corneal Opacity Associated with Spondyloepiphyseal Dysplasia Congenita

Directory of Open Access Journals (Sweden)

Yuichiro Ishida

2018-02-01

Full Text Available A 13-year-old Japanese female diagnosed with spondyloepiphyseal dysplasia congenita (SEDC was referred for ophthalmologic evaluation. Examination with slit-lamp and optical coherence tomography revealed bilateral thin cornea with diffuse corneal opacity which was localised at the posterior stromal depth in the central cornea. Unlike the two previously reported cases of diffuse and nodular patterns of corneal opacity in SEDC, the current case exhibited a rare form of corneal opacity. SEDC is one of the type II collagenopathies, characterised by dwarfism because the mutations in COL2A1 prevent bone growth. Although the existence of type II collagen has not been reported in the human corneal stroma, the aetiology of the opacity in the corneal stroma in SEDC type II collagenopathy is of interest.

AN ANALYTICAL STUDY OF EFFICACY OF CORNEAL COLLAGEN CROSSLINKING C3R PROCEDURE IN PROGRESSIVE KERATOCONUS PATIENTS

Directory of Open Access Journals (Sweden)

Rajasekar K

2017-10-01

Full Text Available BACKGROUND Keratoconus affects a significant number of the general population with conical weakened protruded area from the cornea due to weakening of the corneal stroma by a genetically premeditated preponderance. We see keratoconus as a standalone disease or accompanying other syndrome manifestations in patients. Mainly, the inferotemporal cornea is affected and the conical protrusion causes profound high irregular myopic astigmatism as a refractive error, which is very difficult to correct in progressed advanced stages. Especially in economically productive age group patients, the poor vision becomes very difficult to live with. Corneal collagen crosslinking procedure is a novel tool in the armamentarium of treatment procedures against this malady. MATERIALS AND METHODS This analytical study was conducted at cornea services, Regional Institute of Ophthalmology and Government Ophthalmic Hospital, Chennai, for a period of 14 months. Forty five eyes of forty patients with early progressive keratoconus who presented to cornea services were subjected to riboflavin UVA collagen crosslinking procedures using a standard protocol after getting an informed consent. Further response to treatment were assessed in the follow up period. RESULTS Out of 40 patients in our series, 23 were males and 17 were females. The maximum patients in our series were in the age group between 10 to 25 yrs. Epi-off procedure was done in 31 eyes and epi-on procedure was done in 14 eyes. The patients with pachymetry 400-450 microns underwent epi-on procedure and more than 450 microns underwent epi-off C3R procedure. The K values in our series were between 49D to maximum 63D. The topographic flattening was seen in 52% in epi-on and epi-off procedures. Vision improvement in our series was 57% following epi-on and 65% following epi-off procedures. CONCLUSION C3R is a very promising therapeutic modality that may halt the progression of ectatic process. It is a less invasive mode

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.

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...... of prostatic bone metastases. Blood samples were obtained prior to biopsy or TURP. Serum PICP, PIIINP and ICTP were measured with commercial available RIAs and PSA by IRMA. Serum PSA was increased in patients with local prostatic cancer compared with patients with hyperplasia (p

Distinct characteristics of mandibular bone collagen relative to long bone collagen: relevance to clinical dentistry.

Science.gov (United States)

Matsuura, Takashi; Tokutomi, Kentaro; Sasaki, Michiko; Katafuchi, Michitsuna; Mizumachi, Emiri; Sato, Hironobu

2014-01-01

Bone undergoes constant remodeling throughout life. The cellular and biochemical mechanisms of bone remodeling vary in a region-specific manner. There are a number of notable differences between the mandible and long bones, including developmental origin, osteogenic potential of mesenchymal stem cells, and the rate of bone turnover. Collagen, the most abundant matrix protein in bone, is responsible for determining the relative strength of particular bones. Posttranslational modifications of collagen, such as intermolecular crosslinking and lysine hydroxylation, are the most essential determinants of bone strength, although the amount of collagen is also important. In comparison to long bones, the mandible has greater collagen content, a lower amount of mature crosslinks, and a lower extent of lysine hydroxylation. The great abundance of immature crosslinks in mandibular collagen suggests that there is a lower rate of cross-link maturation. This means that mandibular collagen is relatively immature and thus more readily undergoes degradation and turnover. The greater rate of remodeling in mandibular collagen likely renders more flexibility to the bone and leaves it more suited to constant exercise. As reviewed here, it is important in clinical dentistry to understand the distinctive features of the bones of the jaw.

Distinct Characteristics of Mandibular Bone Collagen Relative to Long Bone Collagen: Relevance to Clinical Dentistry

Directory of Open Access Journals (Sweden)

Takashi Matsuura

2014-01-01

Full Text Available Bone undergoes constant remodeling throughout life. The cellular and biochemical mechanisms of bone remodeling vary in a region-specific manner. There are a number of notable differences between the mandible and long bones, including developmental origin, osteogenic potential of mesenchymal stem cells, and the rate of bone turnover. Collagen, the most abundant matrix protein in bone, is responsible for determining the relative strength of particular bones. Posttranslational modifications of collagen, such as intermolecular crosslinking and lysine hydroxylation, are the most essential determinants of bone strength, although the amount of collagen is also important. In comparison to long bones, the mandible has greater collagen content, a lower amount of mature crosslinks, and a lower extent of lysine hydroxylation. The great abundance of immature crosslinks in mandibular collagen suggests that there is a lower rate of cross-link maturation. This means that mandibular collagen is relatively immature and thus more readily undergoes degradation and turnover. The greater rate of remodeling in mandibular collagen likely renders more flexibility to the bone and leaves it more suited to constant exercise. As reviewed here, it is important in clinical dentistry to understand the distinctive features of the bones of the jaw.

Construction of Anterior Hemi-Corneal Equivalents Using Nontransfected Human Corneal Cells and Transplantation in Dog Models.

Science.gov (United States)

Xu, Bin; Song, Zhan; Fan, Tingjun

2017-11-01

Tissue-engineered human anterior hemi-cornea (TE-aHC) is a promising equivalent for treating anterior lamellar keratopathy to surmount the severe shortage of donated corneas. This study was intended to construct a functional TE-aHC with nontransfected human corneal stromal (ntHCS) and epithelial (ntHCEP) cells using acellular porcine corneal stromata (aPCS) as a carrier scaffold, and evaluate its biological functions in a dog model. To construct a TE-aHC, ntHCS cells were injected into an aPCS scaffold and cultured for 3 days; then, ntHCEP cells were inoculated onto the Bowman's membrane of the scaffold and cultured for 5 days under air-liquid interface condition. After its morphology and histological structure were characterized, the constructed TE-aHC was transplanted into dog eyes via lamellar keratoplasty. The corneal transparency, thickness, intraocular pressure, epithelial integrity, and corneal regeneration were monitored in vivo, and the histological structure and histochemical property were examined ex vivo 360 days after surgery, respectively. The results showed that the constructed TE-aHC was highly transparent and composed of a corneal epithelium of 7-8 layer ntHCEP cells and a corneal stroma of regularly aligned collagen fibers and well-preserved glycosaminoglycans with sparsely distributed ntHCS cells, mimicking a normal anterior hemi-cornea (aHC). Moreover, both ntHCEP and ntHCS cells maintained positive expression of their marker and functional proteins. After transplantation into dog eyes, the constructed TE-aHC acted naturally in terms of morphology, structure and inherent property, and functioned well in maintaining corneal clarity, thickness, normal histological structure, and composition in dog models by reconstructing a normal aHC, which could be used as a promising aHC equivalent in corneal regenerative medicine and aHC disorder therapy. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Unilateral congenital corneal keloid with anterior segment mesenchymal dysgenesis and subluxated lens: case report and review of literature.

Science.gov (United States)

Vanathi, M; Sen, Seema; Panda, Anita; Dada, Tanuj; Behera, Geeta; Khokhar, Sudharshan

2007-01-01

To report the unusual association of unilateral congenital corneal keloid with anterior-segment mesenchymal dysgenesis and bilateral subluxated lens. A 20-year old man presented with a mass lesion involving the left cornea. The corneal lesion had been present since birth. On biomicroscopic examination, a well-defined vascularized, grayish-white mass occupying the whole of the left cornea was seen. The right eye showed multiple peripheral corneal opacities with iridocorneal adhesions, a poorly defined supranasal limbus, and a subluxated lens. Excision biopsy of the mass was done for histopathologic examination. Histopathologic examination of the excised corneal mass showed features consistent with that of a corneal keloid: thickened keratinized epithelium, absent Bowman membrane layer, and fibrovascular hyperplasia composed of hyalinized collagen fibers with irregular orientation of the collagen lamellae. During penetrating keratoplasty of the left eye, an anomalous iris pattern with poorly defined angle and a supranasal subluxated lens was also observed. Extraction of the subluxated lens was also done. The graft failed subsequent to a nonhealing persistent epithelial defect. Our case report highlights the rare association of a unilateral congenital corneal keloid with anterior-segment mesenchymal dysgenesis and bilateral subluxated lens.

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

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

Structure of collagen-glycosaminoglycan matrix and the influence to its integrity and stability.

Science.gov (United States)

Bi, Yuying; Patra, Prabir; Faezipour, Miad

2014-01-01

Glycosaminoglycan (GAG) is a chain-like disaccharide that is linked to polypeptide core to connect two collagen fibrils/fibers and provide the intermolecular force in Collagen-GAG matrix (C-G matrix). Thus, the distribution of GAG in C-G matrix contributes to the integrity and mechanical properties of the matrix and related tissue. This paper analyzes the transverse isotropic distribution of GAG in C-G matrix. The angle of GAGs related to collagen fibrils is used as parameters to qualify the GAGs isotropic characteristic in both 3D and 2D rendering. Statistical results included that over one third of GAGs were perpendicular directed to collagen fibril with symmetrical distribution for both 3D matrix and 2D plane cross through collagen fibrils. The three factors tested in this paper: collagen radius, collagen distribution, and GAGs density, were not statistically significant for the strength of Collagen-GAG matrix in 3D rendering. However in 2D rendering, a significant factor found was the radius of collagen in matrix for the GAGs directed to orthogonal plane of Collagen-GAG matrix. Between two cross-section selected from Collagen-GAG matrix model, the plane cross through collagen fibrils was symmetrically distributed but the total percentage of perpendicular directed GAG was deducted by decreasing collagen radius. There were some symmetry features of GAGs angle distribution in selected 2D plane that passed through space between collagen fibrils, but most models showed multiple peaks in GAGs angle distribution. With less GAGs directed to perpendicular of collagen fibril, strength in collagen cross-section weakened. Collagen distribution was also a factor that influences GAGs angle distribution in 2D rendering. True hexagonal collagen packaging is reported in this paper to have less strength at collagen cross-section compared to quasi-hexagonal collagen arrangement. In this work focus is on GAGs matrix within the collagen and its relevance to anisotropy.

The Role of Titanium Surface Microtopography on Adhesion, Proliferation, Transformation, and Matrix Deposition of Corneal Cells.

Science.gov (United States)

Zhou, Chengxin; Lei, Fengyang; Chodosh, James; Paschalis, Eleftherios I

2016-04-01

Titanium (Ti) is an excellent implantable biomaterial that can be further enhanced by surface topography optimization. Despite numerous data from orthopedics and dentistry, the effect of Ti surface topography on ocular cells is still poorly understood. In light of the recent adaptation of Ti in the Boston Keratoprosthesis artificial cornea, we attempted to perform an extended evaluation of the effect of Ti surface topography on corneal cell adhesion, proliferation, cytotoxicity, transformation, and matrix deposition. Different surface topographies were generated on medical grade Ti-6Al-4V-ELI (extra-low interstitial), with linearly increased roughness (polished to grit blasted). Biological response was evaluated in vitro using human corneal limbal epithelial (HCLE) cells, stromal fibroblasts (HCF), and endothelial cells (HCEnC). None of the Ti surface topographies caused cytotoxicity to any of the three corneal cell types. However, rough Ti surface inhibited HCLE and HCF cell adhesion and proliferation, while HCEnC proliferation was unaffected. Long-term experiments with HCF revealed that rough Ti surface with R(a) (the arithmetic average of the profile height from the mean line) ≥ 1.15 μm suppressed HCF focal adhesion kinase phosphorylation, changed fibroblast morphology, and caused less aligned and reduced deposition of collagen matrix as compared to smooth Ti (R(a) ≤ 0.08 μm). In the presence of transforming growth factor β1 (TGFβ1) stimulation, rough Ti inhibited alpha-smooth muscle actin (α-SMA) expression and collagen deposition, leading to decreased myofibroblast transformation and disorganization of the collagen fibrils as compared to smooth Ti. This study suggests that Ti surface topography regulates corneal cell behavior in a tissue-dependent manner that varies across the corneal strata. Contrary to the accepted paradigm, smooth surface topography can enhance cell adhesion and proliferation and increase matrix deposition by corneal cells.

The Collagen-Binding Adhesin Is a Virulence Factor in Staphylococcus aureus Keratitis

Science.gov (United States)

Rhem, Marcus N.; Lech, Elizabeth M.; Patti, Joseph M.; McDevitt, Damien; Höök, Magnus; Jones, Dan B.; Wilhelmus, Kirk R.

2000-01-01

A collagen-binding strain of Staphylococcus aureus produced suppurative inflammation in a rabbit model of soft contact lens-associated bacterial keratitis more often than its collagen-binding-negative isogenic mutant. Reintroduction of the cna gene on a multicopy plasmid into the mutant helped it regain its corneal adherence and infectivity. The topical application of a collagen-binding peptide before bacterial challenge decreased S. aureus adherence to deepithelialized corneas. These data suggest that the collagen-binding adhesin is involved in the pathogenesis of S. aureus infection of the cornea. PMID:10816547

Fluorescence studies on the aggregation behaviors of collagen modified with NHS-activated poly(γ-glutamic acid).

Science.gov (United States)

Zhang, Min; Yang, Junhui; Yang, Qili; Huang, Liulian; Wu, Hui; Chen, Lihui; Ding, Cuicui

2018-06-01

The poly(γ-glutamic acid)-NHS (γ-PGA-NHS) esters were used to endow collagen with both of excellent water-solubility and thermal stability via cross-linking reaction between γ-PGA-NHS and collagen. In the present work, the effect of γ-PGA-NHS on the aggregation of collagen molecules was studied by fluorescence techniques. The fluorescence emission spectra of pyrene in collagen solutions and the intrinsic fluorescence emission spectra of collagen suggested different effects of γ-PGA-NHS on collagen molecules: inhibiting aggregation below critical aggregation concentration (CAC) and promoting aggregation above CAC. The two-dimensional (2D) fluorescence correlation spectra indicated that the intermolecular hydrogen bonding and cross-linking between γ-PGA-NHS and collagen would influence the aggregation of collagen molecules. By the ultra-sensitive differential scanning calorimeter (VP-DSC), it was found that the main denaturational transition temperature (T m2 ) of modified collagen increased, while its calorimetric enthalpy changes (ΔH 2 ) decreased compared to those of native collagen, further indicating that the modification of γ-PGA-NHS influenced the aggregation of collagen molecules. The study provide useful information for the utilizing and or the processing of water-soluble collagen in aqueous solution in the fields such as cosmetics, health care products, tissue engineering and biomedical materials, etc. Copyright © 2018 Elsevier B.V. All rights reserved.

The biochemical changes of bone collagen after high-dose irradiation

International Nuclear Information System (INIS)

Tajiri, Ken

1980-01-01

In our clinic, patients with malignant bone tumors have been treated by high-dose irradiation therapy, 10,000-20,000 rads, for primary lesions. In order to study the biochemical changes of normal bone around tumor tissue, especially bone collagen, after high-dose irradiation, the author performed the following experiments. The right knee joint of rabbits was irradiated with either 6,000, 10,000, or 15,000 rads by 60 Co-γ ray. The cortical bone of the right tibial metaphysis was used for analyses and compared with the left tibia of the same rabbit. These studies were followed for one year after the final irradiation. The calcium, phosphorous and collagen contents of irradiated bone were remarkably changed. These data indicate that collagen biosynthesis of irradiated bone was decreased and the calcification was disturbed. An increase in the amount of total soluble collagen and a decrease in the amount of hydroxylysine bound sugar were observed. The ratio of β to α chains of the collagen molecule was also changed by the irradiation. The amount of reducible cross-links per hydroxyproline residue was strikingly increased three months after the final irradiation. These changes were remarkable especially in the 10,000 and 15,000 rads irradiated group and found to be recovered approximately six months to one year after the final irradiation. These findings indicate that high-dose irradiation reduces the stability of bone collagen both with the destruction of sugar bonds of hydroxylysine residues and the replacement of matured collagen matrix to immatured one which contain mostly labile reducible cross-links. (author)

Influence of tetrahydrocurcumin on tail tendon collagen contents and its properties in rats with streptozotocin-nicotinamide-induced type 2 diabetes.

Science.gov (United States)

Pari, Leelavinothan; Murugan, Pidaran

2007-12-01

Changes in the structural and functional properties of collagen caused by advanced glycation might be of importance for the etiology of late-stage complications in diabetics. Curcumin is the most active component of turmeric. It is believed that curcumin is a potent antioxidant and anti-inflammatory agent. Tetrahydrocurcumin (THC) is one of the major metabolites of curcumin, exhibiting many of the same physiological and pharmacological activities of curcumin and in some systems may exert greater antioxidant activity than curcumin. In diabetic rats, hydroxyproline and collagen content as well as its degree of cross-linking were increased, as shown by increased extent of glycation, collagen-linked fluorescence, neutral salt collagen, and decreased acid and pepsin solubility. Administration of THC for 45 days to diabetic rats significantly reduced the accumulation and cross-linking of collagen. The effects of THC were comparable with those of curcumin. In conclusion, administration of THC had a positive influence on the content of collagen and its properties in streptozotocin- and nicotinamide-induced diabetic rats. THC was found to be more effective than curcumin.

CrossWork: Software-assisted identification of cross-linked peptides

DEFF Research Database (Denmark)

Rasmussen, Morten; Refsgaard, Jan; Peng, Li

2011-01-01

Work searches batches of tandem mass-spectrometric data, and identifies cross-linked and non-cross-linked peptides using a standard PC. We tested CrossWork by searching mass-spectrometric datasets of cross-linked complement factor C3 against small (1 protein) and large (1000 proteins) search spaces, and show...

Fracture mechanics of collagen fibrils

DEFF Research Database (Denmark)

Svensson, Rene B; Mulder, Hindrik; Kovanen, Vuokko

2013-01-01

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...

The Antifibrosis Effects of Peroxisome Proliferator-Activated Receptor δ on Rat Corneal Wound Healing after Excimer Laser Keratectomy

Directory of Open Access Journals (Sweden)

Yun Gu

2014-01-01

Full Text Available Corneal stromal fibrosis characterized by myofibroblasts and abnormal extracellular matrix (ECM is usually the result of inappropriate wound healing. The present study tested the hypothesis that the ligand activation of peroxisome proliferator-activated receptor (PPAR δ had antifibrosis effects in a rat model of corneal damage. Adult Sprague-Dawley rats underwent bilateral phototherapeutic keratectomy (PTK. The eyes were randomized into four groups: PBS, GW501516 (a selective agonist of PPARδ, GSK3787 (a selective antagonist of PPARδ, or GW501516 combined with GSK3787. The agents were subconjunctivally administered twice a week until sacrifice. The cellular aspects of corneal wound healing were evaluated with in vivo confocal imaging and postmortem histology. A myofibroblast marker (α-smooth muscle actin and ECM production (fibronectin, collagen type III and collagen type I were examined by immunohistochemistry and RT-PCR. At the early stages of wound healing, GW501516 inhibited reepithelialization and promoted angiogenesis. During the remodeling phase of wound healing, GW501516 attenuated the activation and proliferation of keratocytes, which could be reversed by GSK3787. GW501516 decreased transdifferentiation from keratocytes into myofibroblasts, ECM synthesis, and corneal haze. These results demonstrate that GW501516 controls corneal fibrosis and suggest that PPARδ may potentially serve as a therapeutic target for treating corneal scars.

Cross-linking of polymeric materials

International Nuclear Information System (INIS)

Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.

1991-01-01

The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

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.

Biocompatibility and Biomechanical Effect of Single Wall Carbon Nanotubes Implanted in the Corneal Stroma: A Proof of Concept Investigation

Directory of Open Access Journals (Sweden)

Alfredo Vega-Estrada

2016-01-01

Full Text Available Corneal ectatic disorders are characterized by a progressive weakening of the tissue due to biomechanical alterations of the corneal collagen fibers. Carbon nanostructures, mainly carbon nanotubes (CNTs and graphene, are nanomaterials that offer extraordinary mechanical properties and are used to increase the rigidity of different materials and biomolecules such as collagen fibers. We conducted an experimental investigation where New Zealand rabbits were treated with a composition of CNTs suspended in balanced saline solution which was applied in the corneal tissue. Biocompatibility of the composition was assessed by means of histopathology analysis and mechanical properties by stress-strain measurements. Histopathology samples stained with blue Alcian showed that there were no fibrous scaring and no alterations in the mucopolysaccharides of the stroma. It also showed that there were no signs of active inflammation. These were confirmed when Masson trichrome staining was performed. Biomechanical evaluation assessed by means of tensile test showed that there is a trend to obtain higher levels of rigidity in those corneas implanted with CNTs, although these changes are not statistically significant (p>0.05. Implanting CNTs is biocompatible and safe procedure for the corneal stroma which can lead to an increase in the rigidity of the collagen fibers.

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.

Production and in vitro characterization of 3D porous scaffolds made of magnesium carbonate apatite (MCA)/anionic collagen using a biomimetic approach

International Nuclear Information System (INIS)

Sader, Marcia S.; Martins, Virginia C.A.; Gomez, Santiago; LeGeros, Racquel Z.; Soares, Gloria A.

2013-01-01

3D porous scaffolds are relevant biomaterials to bone engineering as they can be used as templates to tissue reconstruction. The aim of the present study was to produce and characterize in vitro 3D magnesium-carbonate apatite/collagen (MCA/col) scaffolds. They were prepared by using biomimetic approach, followed by cross-linking with 0.25% glutaraldehyde solution (GA) and liofilization. Results obtained with Fourier-transform infrared spectroscopy (FT-IR) confirmed the type-B carbonate substitution, while by X-ray diffraction (XRD), a crystallite size of ∼ 10 nm was obtained. Optical and electron microscopy showed that the cylindrical samples exhibited an open-porous morphology, with apatite nanocrystals precipitated on collagen fibrils. The cross-linked 3D scaffolds showed integrity when immersed in culture medium up to 14 days. Also, the immersion of such samples into an acid buffer solution, to mimic the osteoclastic resorption environment, promotes the release of important ions for bone repair, such as calcium, phosphorus and magnesium. Bone cells (SaOs2) adhered, and proliferated on the 3D composite scaffolds, showing that synthesis and the cross-linking processes did not induce cytotoxicity. Highlights: • 3D scaffolds of Mg-carbonate–apatite and anionic-collagen were produced. • The biomimetic approach and the cross-linking with 0.25% GA solution were employed. • The scaffolds showed open-porous structure and apatite crystals on collagen fibrils. • The cross-linked scaffolds exhibited integrity when immersed in culture medium. • SaOs2 cells adhered and proliferated on the cross-linked scaffolds confirming no cytotoxicity

Production and in vitro characterization of 3D porous scaffolds made of magnesium carbonate apatite (MCA)/anionic collagen using a biomimetic approach

Energy Technology Data Exchange (ETDEWEB)

Sader, Marcia S., E-mail: msader@metalmat.ufrj.br [Prog. Engenharia Metalúrgica e Materiais, COPPE/UFRJ, RJ (Brazil); Martins, Virginia C.A. [Depto. de Química e Física Molecular, IQSC/USP, SP (Brazil); Gomez, Santiago [Dept. Anatomía Patológica, Universidad de Cádiz, Cadiz (Spain); LeGeros, Racquel Z. [Department of Biomaterials and Biomimetics, New York University College of Dentistry, NY (United States); Soares, Gloria A. [Prog. Engenharia Metalúrgica e Materiais, COPPE/UFRJ, RJ (Brazil)

2013-10-15

3D porous scaffolds are relevant biomaterials to bone engineering as they can be used as templates to tissue reconstruction. The aim of the present study was to produce and characterize in vitro 3D magnesium-carbonate apatite/collagen (MCA/col) scaffolds. They were prepared by using biomimetic approach, followed by cross-linking with 0.25% glutaraldehyde solution (GA) and liofilization. Results obtained with Fourier-transform infrared spectroscopy (FT-IR) confirmed the type-B carbonate substitution, while by X-ray diffraction (XRD), a crystallite size of ∼ 10 nm was obtained. Optical and electron microscopy showed that the cylindrical samples exhibited an open-porous morphology, with apatite nanocrystals precipitated on collagen fibrils. The cross-linked 3D scaffolds showed integrity when immersed in culture medium up to 14 days. Also, the immersion of such samples into an acid buffer solution, to mimic the osteoclastic resorption environment, promotes the release of important ions for bone repair, such as calcium, phosphorus and magnesium. Bone cells (SaOs2) adhered, and proliferated on the 3D composite scaffolds, showing that synthesis and the cross-linking processes did not induce cytotoxicity. Highlights: • 3D scaffolds of Mg-carbonate–apatite and anionic-collagen were produced. • The biomimetic approach and the cross-linking with 0.25% GA solution were employed. • The scaffolds showed open-porous structure and apatite crystals on collagen fibrils. • The cross-linked scaffolds exhibited integrity when immersed in culture medium. • SaOs2 cells adhered and proliferated on the cross-linked scaffolds confirming no cytotoxicity.

Effects of Genipin Concentration on Cross-Linked Chitosan Scaffolds for Bone Tissue Engineering: Structural Characterization and Evidence of Biocompatibility Features

Directory of Open Access Journals (Sweden)

Simona Dimida

2017-01-01

Full Text Available Genipin (GN is a natural molecule extracted from the fruit of Gardenia jasminoides Ellis according to modern microbiological processes. Genipin is considered as a favorable cross-linking agent due to its low cytotoxicity compared to widely used cross-linkers; it cross-links compounds with primary amine groups such as proteins, collagen, and chitosan. Chitosan is a biocompatible polymer that is currently studied in bone tissue engineering for its capacity to promote growth and mineral-rich matrix deposition by osteoblasts in culture. In this work, two genipin cross-linked chitosan scaffolds for bone repair and regeneration were prepared with different GN concentrations, and their chemical, physical, and biological properties were explored. Scanning electron microscopy and mechanical tests revealed that nonremarkable changes in morphology, porosity, and mechanical strength of scaffolds are induced by increasing the cross-linking degree. Also, the degradation rate was shown to decrease while increasing the cross-linking degree, with the high cross-linking density of the scaffold disabling the hydrolysis activity. Finally, basic biocompatibility was investigated in vitro, by evaluating proliferation of two human-derived cell lines, namely, the MG63 (human immortalized osteosarcoma and the hMSCs (human mesenchymal stem cells, as suitable cell models for bone tissue engineering applications of biomaterials.

The effect of riboflavin/UVA cross-linking on anti-degeneration and promoting angiogenic capability of decellularized liver matrix.

Science.gov (United States)

Xiang, Junxi; Liu, Peng; Zheng, Xinglong; Dong, Dinghui; Fan, Shujuan; Dong, Jian; Zhang, Xufeng; Liu, Xuemin; Wang, Bo; Lv, Yi

2017-10-01

Weak mechanical property and unstable degradation rate limited the application of decellularized liver matrix in tissue engineering. The aim of this study was to explore a new method for improving the mechanical properties, anti-degeneration and angiogenic capability of decellularized liver matrix. This was achieved by a novel approach using riboflavin/ultraviolet A treatment to induce collagen cross-linking of decellularized matrix. Histological staining and scanning electron microscope showed that the diameter of cross-linked fibers significantly increased compared with the control group. The average peak load and Young's modulus of decellularized matrix were obviously improved after cross-linking. Then we implanted the modified matrix into the rat hepatic injury model to test the anti-degeneration and angiogenic capability of riboflavin/UVA cross-linked decellularized liver scaffolds in vivo. The results indicated that cross-linked scaffolds degrade more slowly than those in the control group. In the experiment group, average microvessel density in the implanted matrix was higher than that in the control group since the first week after implantation. In conclusion, we initiated the method to improve the biomechanical properties of decellularized liver scaffolds by riboflavin/UVA cross-linking, and more importantly, its improvement on anti-degeneration and angiogenesis was identified. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2662-2669, 2017. © 2017 Wiley Periodicals, Inc.

Imaging and modeling of collagen architecture in living tissue with polarized light transfer (Conference Presentation)

Science.gov (United States)

Ramella-Roman, Jessica C.; Stoff, Susan; Chue-Sang, Joseph; Bai, Yuqiang

2016-03-01

The extra-cellular space in connective tissue of animals and humans alike is comprised in large part of collagen. Monitoring of collagen arrangement and cross-linking has been utilized to diagnose a variety of medical conditions and guide surgical intervention. For example, collagen monitoring is useful in the assessment and treatment of cervical cancer, skin cancer, myocardial infarction, and non-arteritic anterior ischemic optic neuropathy. We have developed a suite of tools and models based on polarized light transfer for the assessment of collagen presence, cross-linking, and orientation in living tissue. Here we will present some example of such approach applied to the human cervix. We will illustrate a novel Mueller Matrix (MM) imaging system for the study of cervical tissue; furthermore we will show how our model of polarized light transfer through cervical tissue compares to the experimental findings. Finally we will show validation of the methodology through histological results and Second Harmonic imaging microscopy.

Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases

NARCIS (Netherlands)

Iglesias, A.I. (Adriana I.); A. Mishra (Aniket); V. Vitart (Veronique); Y. Bykhovskaya (Yelena); R. Höhn (René); H. Springelkamp (Henriët); G. Cuellar-Partida (Gabriel); P. Gharahkhani (Puya); Bailey, J.N.C. (Jessica N. Cooke); Willoughby, C.E. (Colin E.); X. Li (Xiaohui); S. Yazar (Seyhan); A. Nag (Abhishek); A.P. Khawaja (Anthony); O. Polasek (Ozren); D.S. Siscovick (David); Mitchell, P. (Paul); Y.C. Tham (Yih Chung); J.L. Haines (Jonathan); L.S. Kearns (Lisa S.); C. Hayward (Caroline); Shi, Y. (Yuan); Van Leeuwen, E.M. (Elisabeth M.); K.D. Taylor (Kent); Wang, J.J. (Jie Jin); E. Rochtchina (Elena); J. Attia (John); Scott, R. (Rodney); E.G. Holliday (Elizabeth); P.N. Baird (Paul); Xie, J. (Jing); Inouye, M. (Michael); Viswanathan, A. (Ananth); X. Sim (Xueling); P.W.M. Bonnemaijer (Pieter); J.I. Rotter (Jerome I.); Martin, N.G. (Nicholas G.); T. Zeller (Tanja); R.A. Mills (Richard); S.E. Staffieri (Sandra E.); Jonas, J.B. (Jost B.); Schmidtmann, I. (Irene); T. Boutin (Thibaud); Kang, J.H. (Jae H.); S.E.M. Lucas (Sionne E.M.); Wong, T.Y. (Tien Yin); Beutel, M.E. (Manfred E.); Wilson, J.F. (James F.); R.R. Allingham (R Rand); M.H. Brilliant (Murray H.); D.L. Budenz (Donald L.); W.G. Christen (William G.); J. Fingert (John); D.S. Friedman (David); Gaasterland, D. (Douglas); T. Gaasterland (Terry); M.A. Hauser (Michael); P. Kraft (Peter); Lee, R.K. (Richard K.); P.A. Lichter (Paul A.); Liu, Y. (Yutao); S.J. Loomis (Stephanie J.); S.E. Moroi (Sayoko); M.A. Pericak-Vance (Margaret); A. Realini (Anthony); Richards, J.E. (Julia E.); J.S. Schuman (Joel S.); W.K. Scott (William); K. Singh (Kuldev); A.J. Sit (Arthur J.); D. Vollrath (Douglas); R.N. Weinreb (Robert N.); G. Wollstein (Gadi); D.J. Zack (Donald); K. Zhang (Kang); Donnelly, P. (Peter); I.E. Barroso (Inês); Blackwell, J.M. (Jenefer M.); E. Bramon (Elvira); M.A. Brown (Matthew); J.P. Casas (Juan); A. Corvin (Aiden); Deloukas, P. (Panos); A. Duncanson (Audrey); Jankowski, J. (Janusz); H.S. Markus (Hugh); J. Mathew (Joseph); C.N.A. Palmer (Colin); R. Plomin (Robert); A. Rautanen (Anna); S.J. Sawcer (Stephen); R.C. Trembath (Richard); Wood, N.W. (Nicholas W.); C.C.A. Spencer (Chris C.); G. Band (Gavin); C. Bellenguez (Céline); Freeman, C. (Colin); F.A. Hellenthal; E. Giannoulatou (Eleni); M. Pirinen (Matti); R. Pearson (Ruth); A. Strange (Amy); Z. Su (Zhan); D. Vukcevic (Damjan); Langford, C. (Cordelia); Hunt, S.E. (Sarah E.); T. Edkins (Ted); R. Gwilliam (Rhian); H. Blackburn (Hannah); S. Bumpstead (Suzannah); S. Dronov (Serge); M. Gillman (Matthew); E. Gray (Emma); N. Hammond (Naomi); A. Jayakumar (Alagurevathi); O.T. McCann (Owen); J. Liddle (Jennifer); S.C. Potter (Simon); Ravindrarajah, R. (Radhi); Ricketts, M. (Michelle); P. Waller (Patrick); P. Weston (Paul); S. Widaa (Sara); Whittaker, P. (Pamela); A.G. Uitterlinden (André); E.N. Vithana (Eranga); P.J. Foster (Paul); P.G. Hysi (Pirro); Hewitt, A.W. (Alex W.); C.C. Khor; L.R. Pasquale (Louis); Montgomery, G.W. (Grant W.); C.C.W. Klaver (Caroline); T. Aung (Tin); A.F.H. Pfeiffer (Andreas); D.A. Mackey (David); C.J. Hammond (Christopher); Cheng, C.-Y. (Ching-Yu); J.E. Craig (Jamie); Y.S. Rabinowitz (Yaron); J.L. Wiggs (Janey L.); K.P. Burdon (Kathryn); C.M. van Duijn (Cornelia); MacGregor, S. (Stuart)

2018-01-01

textabstractCentral corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. In addition to adding support for known connective tissue-related

Efficient Generation of Human Embryonic Stem Cell-Derived Corneal Endothelial Cells by Directed Differentiation.

Directory of Open Access Journals (Sweden)

Kathryn L McCabe

Full Text Available To generate human embryonic stem cell derived corneal endothelial cells (hESC-CECs for transplantation in patients with corneal endothelial dystrophies.Feeder-free hESC-CECs were generated by a directed differentiation protocol. hESC-CECs were characterized by morphology, expression of corneal endothelial markers, and microarray analysis of gene expression.hESC-CECs were nearly identical morphologically to primary human corneal endothelial cells, expressed Zona Occludens 1 (ZO-1 and Na+/K+ATPaseα1 (ATPA1 on the apical surface in monolayer culture, and produced the key proteins of Descemet's membrane, Collagen VIIIα1 and VIIIα2 (COL8A1 and 8A2. Quantitative PCR analysis revealed expression of all corneal endothelial pump transcripts. hESC-CECs were 96% similar to primary human adult CECs by microarray analysis.hESC-CECs are morphologically similar, express corneal endothelial cell markers and express a nearly identical complement of genes compared to human adult corneal endothelial cells. hESC-CECs may be a suitable alternative to donor-derived corneal endothelium.

Human stem cell based corneal tissue mimicking structures using laser-assisted 3D bioprinting and functional bioinks.

Science.gov (United States)

Sorkio, Anni; Koch, Lothar; Koivusalo, Laura; Deiwick, Andrea; Miettinen, Susanna; Chichkov, Boris; Skottman, Heli

2018-07-01

There is a high demand for developing methods to produce more native-like 3D corneal structures. In the present study, we produced 3D cornea-mimicking tissues using human stem cells and laser-assisted bioprinting (LaBP). Human embryonic stem cell derived limbal epithelial stem cells (hESC-LESC) were used as a cell source for printing epithelium-mimicking structures, whereas human adipose tissue derived stem cells (hASCs) were used for constructing layered stroma-mimicking structures. The development and optimization of functional bioinks was a crucial step towards successful bioprinting of 3D corneal structures. Recombinant human laminin and human sourced collagen I served as the bases for the functional bioinks. We used two previously established LaBP setups based on laser induced forward transfer, with different laser wavelengths and appropriate absorption layers. We bioprinted three types of corneal structures: stratified corneal epithelium using hESC-LESCs, lamellar corneal stroma using alternating acellular layers of bioink and layers with hASCs, and finally structures with both a stromal and epithelial part. The printed constructs were evaluated for their microstructure, cell viability and proliferation, and key protein expression (Ki67, p63α, p40, CK3, CK15, collagen type I, VWF). The 3D printed stromal constructs were also implanted into porcine corneal organ cultures. Both cell types maintained good viability after printing. Laser-printed hESC-LESCs showed epithelial cell morphology, expression of Ki67 proliferation marker and co-expression of corneal progenitor markers p63α and p40. Importantly, the printed hESC-LESCs formed a stratified epithelium with apical expression of CK3 and basal expression of the progenitor markers. The structure of the 3D bioprinted stroma demonstrated that the hASCs had organized horizontally as in the native corneal stroma and showed positive labeling for collagen I. After 7 days in porcine organ cultures, the 3D bioprinted

From Nano to Macro: Studying the Hierarchical Structure of the Corneal Extracellular Matrix

Science.gov (United States)

Quantock, Andrew J.; Winkler, Moritz; Parfitt, Geraint J.; Young, Robert D.; Brown, Donald J.; Boote, Craig; Jester, James V.

2014-01-01

In this review, we discuss current methods for studying ocular extracellular matrix (ECM) assembly from the ‘nano’ to the ‘macro’ levels of hierarchical organization. Since collagen is the major structural protein in the eye, providing mechanical strength and controlling ocular shape, the methods presented focus on understanding the molecular assembly of collagen at the nanometer level using x-ray scattering through to the millimeter to centimeter level using nonlinear optical (NLO) imaging of second harmonic generated (SHG) signals. Three-dimensional analysis of ECM structure is also discussed, including electron tomography, serial block face scanning electron microscopy (SBF-SEM) and digital image reconstruction. Techniques to detect non-collagenous structural components of the ECM are also presented, and these include immunoelectron microscopy and staining with cationic dyes. Together, these various approaches are providing new insights into the structural blueprint of the ocular ECM, and in particular that of the cornea, which impacts upon our current understanding of the control of corneal shape, pathogenic mechanisms underlying ectatic disorders of the cornea and the potential for corneal tissue engineering. PMID:25819457

Corneal markers of diabetic neuropathy.

Science.gov (United States)

Pritchard, Nicola; Edwards, Katie; Shahidi, Ayda M; Sampson, Geoff P; Russell, Anthony W; Malik, Rayaz A; Efron, Nathan

2011-01-01

Diabetic neuropathy is a significant clinical problem that currently has no effective therapy, and in advanced cases, leads to foot ulceration and lower limb amputation. The accurate detection, characterization and quantification of this condition are important in order to define at-risk patients, anticipate deterioration, monitor progression, and assess new therapies. This review evaluates novel corneal methods of assessing diabetic neuropathy. Two new noninvasive corneal markers have emerged, and in cross-sectional studies have demonstrated their ability to stratify the severity of this disease. Corneal confocal microscopy allows quantification of corneal nerve parameters and noncontact corneal esthesiometry, the functional correlate of corneal structure, assesses the sensitivity of the cornea. Both these techniques are quick to perform, produce little or no discomfort for the patient, and are suitable for clinical settings. Each has advantages and disadvantages over traditional techniques for assessing diabetic neuropathy. Application of these new corneal markers for longitudinal evaluation of diabetic neuropathy has the potential to reduce dependence on more invasive, costly, and time-consuming assessments, such as skin biopsy.

Aloe vera: an in vitro study of effects on corneal wound closure and collagenase activity.

Science.gov (United States)

Curto, Elizabeth M; Labelle, Amber; Chandler, Heather L

2014-11-01

To evaluate the in vitro effects of an aloe vera solution on (i) the viability and wound healing response of corneal cells and (ii) the ability to alter collagenase and gelatinase activities. Primary cultures of corneal epithelial cells and fibroblasts were prepared from grossly normal enucleated canine globes and treated with an aloe solution (doses ranging from 0.0-2 mg/mL). Cellular viability was evaluated using a colorimetric assay. A corneal wound healing model was used to quantify cellular ingrowth across a defect made on the confluent surface. Anticollagenase and antigelatinase activities were evaluated by incubating a bacterial collagenase/gelatinase with aloe solution (doses ranging from 0.0-500 μg/mL) and comparing outcome measures to a general metalloproteinase inhibitor, 1, 10-phenanthroline, and canine serum (doses ranging from 0.0-100%). None of the concentrations of aloe solution tested significantly affected the viability of corneal epithelial cells or fibroblasts. Concentrations ≤175 μg/mL slightly accelerated corneal epithelial cell wound closure; this change was not significant. Concentrations ≥175 μg/mL significantly (P ≤ 0.001) slowed the rate of corneal fibroblast wound closure, while aloe concentrations Aloe solution did not alter the ability for collagenase to degrade gelatin or collagen Type I but increased the ability for collagenase to degrade Type IV collagen. Although additional experiments are required, lower concentrations of aloe solution may be beneficial in healing of superficial corneal wounds to help decrease fibrosis and speed epithelialization. An increase in collagenase activity with aloe vera warrants further testing before considering in vivo studies. © 2014 American College of Veterinary Ophthalmologists.

The effect of vitamin C deficiency and chronic ultraviolet-B exposure on corneal ultrastructure: a preliminary investigation

Science.gov (United States)

Hayes, Sally; Cafaro, Thamara A.; Boguslawska, Patrycja J.; Kamma-Lorger, Christina S.; Boote, Craig; Harris, Jonathan; Young, Robert; Hiller, Jennifer; Terrill, Nicholas; Meek, Keith M.

2011-01-01

Purpose In the visually debilitating condition of climatic droplet keratopathy, corneal transparency is progressively lost. Although the precise cause of the disease and the mechanism by which it progresses are not known, a lifetime exposure to high solar radiation and a vitamin C–deficient diet may be involved in its development. This study examines the effect of dietary ascorbate levels and ultraviolet (UV)-B exposure on corneal stromal structure. Methods Eight guinea pigs were divided into four treatment groups (A, B, C, and D). For 15 weeks, Groups A and C were fed an ascorbate-rich diet (2 mg/100 g bodyweight/day), while Groups B and D received an ascorbate-deficient diet (0.07 mg/100 g bodyweight/day). For the last 12 weeks of the study, Groups C and D also experienced chronic UVB exposure (0.12 J/cm2 for 40 min/day). Following euthanasia, the corneas were enucleated and their stromal ultrastructure examined using X-ray scattering and electron microscopy. Results UVB exposure resulted in an increased corneal thickness (p<0.001), but this was not accompanied by a widespread expansion of the collagen fibrillar array, and in the case of ascorbate-deficient animals, stromal thickening was associated with the compaction of collagen fibrils (p<0.01). Neither UVB exposure nor ascorbic acid deficiency caused any change in the average diameter or D-periodicity of the stromal collagen fibrils. Conclusions UVB-induced changes in the corneal ultrastructure were most pronounced in animals fed an ascorbic acid–deficient diet. This suggests that ascorbic acid may play a vital role in protecting the corneal stroma from the harmful effects of UVB. PMID:22171156

Mechanisms of lamellar collagen formation in connective tissues.

Science.gov (United States)

Ghazanfari, Samaneh; Khademhosseini, Ali; Smit, Theodoor H

2016-08-01

The objective of tissue engineering is to regenerate functional tissues. Engineering functional tissues requires an understanding of the mechanisms that guide the formation and evolution of structure in the extracellular matrix (ECM). In particular, the three-dimensional (3D) collagen fiber arrangement is important as it is the key structural determinant that provides mechanical integrity and biological function. In this review, we survey the current knowledge on collagen organization mechanisms that can be applied to create well-structured functional lamellar tissues and in particular intervertebral disc and cornea. Thus far, the mechanisms behind the formation of cross-aligned collagen fibers in the lamellar structures is not fully understood. We start with cell-induced collagen alignment and strain-stabilization behavior mechanisms which can explain a single anisotropically aligned collagen fiber layer. These mechanisms may explain why there is anisotropy in a single layer in the first place. However, they cannot explain why a consecutive collagen layer is laid down with an alternating alignment. Therefore, we explored another mechanism, called liquid crystal phasing. While dense concentrations of collagen show such behavior, there is little evidence that the conditions for liquid crystal phasing are actually met in vivo. Instead, lysyl aldehyde-derived collagen cross-links have been found essential for correct lamellar matrix deposition. Furthermore, we suggest that supra-cellular (tissue-level) shear stress may be instrumental in the alignment of collagen fibers. Understanding the potential mechanisms behind the lamellar collagen structure in connective tissues will lead to further improvement of the regeneration strategies of functional complex lamellar tissues. Copyright © 2016 Elsevier Ltd. All rights reserved.

Applications of corneal topography and tomography: a review.

Science.gov (United States)

Fan, Rachel; Chan, Tommy Cy; Prakash, Gaurav; Jhanji, Vishal

2018-03-01

Corneal imaging is essential for diagnosing and management of a wide variety of ocular diseases. Corneal topography is used to characterize the shape of the cornea, specifically, the anterior surface of the cornea. Most corneal topographical systems are based on Placido disc that analyse rings that are reflected off the corneal surface. The posterior corneal surface cannot be characterized using Placido disc technology. Imaging of the posterior corneal surface is useful for diagnosis of corneal ectasia. Unlike corneal topographers, tomographers generate a three-dimensional recreation of the anterior segment and provide information about the corneal thickness. Scheimpflug imaging is one of the most commonly used techniques for corneal tomography. The cross-sectional images generated by a rotating Scheimpflug camera are used to locate the anterior and posterior corneal surfaces. The clinical uses of corneal topography include, diagnosis of corneal ectasia, assessment of corneal astigmatism, and refractive surgery planning. This review will discuss the applications of corneal topography and tomography in clinical practice. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

Can Riboflavin Penetrate Stroma Without Disrupting Integrity of Corneal Epithelium in Rabbits? Iontophoresis and Ultraperformance Liquid Chromatography With Electrospray Ionization Tandem Mass Spectrometry.

Science.gov (United States)

Novruzlu, Şahin; Türkcü, Ümmühani Özel; Kvrak, İbrahim; Kvrak, Şeyda; Yüksel, Erdem; Deniz, Nuriye Gökçen; Bilgihan, Ayşe; Bilgihan, Kamil

2015-08-01

To examine riboflavin concentrations in corneas and aqueous humor from rabbits with standard and transepithelial methods and iontophoresis without disrupting the integrity of the corneal epithelium before corneal collagen cross-linking. Twenty-four eyes of 12 adult New Zealand rabbits were used. They were assigned to 4 groups, each including 6 eyes. Group 1 was exposed to the standard method and given riboflavin 0.1% after epithelial debridement. Group 2 was exposed to the transepithelial method and given benzalkonium chloride (BAC), ethylenediaminetetraacetic acid (EDTA), trometamol (TRIS), hydroxypropylmethylcellulose (HPMC), and riboflavin 0.2% 3 times at 1.5-minute intervals followed by riboflavin 0.2%. Group 3 was given riboflavin 0.1% by using 1-mA electric current for 10 minutes with the help of iontophoresis without using substances disrupting the integrity of the corneal epithelium. Group 4 received the same treatment as did group 3, except that it was given riboflavin 0.2%. Following these treatments, riboflavin concentrations in aqueous humor and corneas were measured with ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). Riboflavin concentrations in the cornea and aqueous humor were higher in group 1 (42.4 ± 5.4 μg/g) than in the other groups. They were significantly higher in group 4 (34.2 ± 6.6 μg/g) than in group 2 (24.4 ± 1.2 μg/g) (P = 0.009) and group 3 (23.6 ± 6.1 μg/g) (P = 0.026). There was not a significant difference in corneal riboflavin concentrations between group 2 and group 3 (P = 0.937). Intrastromal and aqueous riboflavin concentrations after administration of riboflavin 0.2% through iontophoresis without disrupting the integrity of the corneal epithelium were lower than those after the standard method, but higher than those after the transepithelial method. In this study, in which riboflavin concentrations were measured with a very sensitive method

Stability of Collagen Scaffold Implants for Animals with Iatrogenic Articular Cartilage Defects

Directory of Open Access Journals (Sweden)

Josef Jančář

2009-01-01

Full Text Available Synthesis and characterization of biodegradable hydrogels based on collagen modified by addition of synthetic biodegradable copolymer intended for preparation of porous scaffolds for mesenchymal stem cells used for possible implantation to animals with articular surface defects was investigated. The synthetic biodegradable tri-block copolymer used was the block copolymer of polyethylene glycol (PEG, polylactic acid (PLA, polyglycolic acid (PGA (PEG-PLGA endcapped with itaconic acid (ITA. The water-soluble carbodiimide and N-hydroxysuccimide system (EDC-NHS was chosen as the cross-linking agent used to control the rate of hydrogel resorption. Dependence of the physical properties of the prepared hydrogels on the concentration of the EDC-NHS cross-linker, reaction time and concentration of PEG-PLGA-ITA copolymer was examined. Swelling behaviour, thermal stability, surface morphology and degradation rate were also characterized. Based on the obtained results, it can be concluded that increase in concentration of the cross-linking agent, as well as prolonged cross-linking time and increased amount of synthetic copolymer lead to enhanced thermal stability of the gels together with a reduced swelling ratio and degradation rate in saline. The resorption rate of these gels used in preparation of cartilage scaffolds can be controlled over a wide time interval by varying the collagen/(PEG-PLGA-ITA blend composition or the conditions of the cross-linking reaction.

Association between anterior corneal astigmatism and posterior corneal astigmatism across age groups: a cross-sectional analysis

Directory of Open Access Journals (Sweden)

Vijay Shetty

2017-11-01

Full Text Available AIM: To assess the anterior corneal astigmatism(ACAand posterior corneal astigmatism(PCApatterns across various age groups. We also evaluated the association between magnitudes and axes of the ACA and PCA across these age groups. METHODS: The present study was a cross-sectional analysis of clinical data of 381 eyes. We converted the clinical astigmatic notation to vector notation for analysis of ACA and PCA. We estimated the correlation between magnitude and axes of the ACA and PCA in the whole population and in four age groups(5-19, 20-39, 40-59, and ≥ 60y. We used random effects linear regression models for estimating the association between the magnitudes of ACA and PCA.RESULTS: The mean of the magnitude of the ACA(3.59Dand the PCA(0.50Dwas highest in children(5 to 9y. Overall, the magnitude of the ACA ranged from 0D to 10.0 Diopters(Dand the magnitude of the PCA ranged from 0 to 3.5 D. There was a significant correlation between the ACA and the PCA in the younger age group(r=0.85, PP=0.03with each unit increase in the ACA, the increase was the smallest in this age group.CONCLUSION: It will be prudent to measure the both the magnitude and axis of the PCA, particularly in those above 60y rather than rely on rule-of-thumb calculations based on ACA parameters for IOL power calculation.

Characterization of the degree of cross-linking in radiation cross-linked low and high density polyethylenes

International Nuclear Information System (INIS)

Posselt, K.; Haedrich, W.

1986-01-01

In practice the cross-linking of irradiated polyethylene is mostly characterized by solubility and thermomechanical data. The irradiation of samples of a LDPE and a HDPE yields very different gel-dose curves. But for a quantitative comparison the complicated connection between the gel values and the corresponding densities of cross-links, especially the dependence on the initial molecular size distribution, has to take into consideration. The analysis of the solubility data according to the statistical theory of cross-linking developed by Inokuti and Saito shows that at equal doses in both investigated PE types in spite of the different gel values nearly the same densities of cross-links are present. That result is confirmed by the densities of cross-links determined from stress-strain measurements at 423 K. (author)

A constitutive model of soft tissue: From nanoscale collagen to tissue continuum

KAUST Repository

Tang, Huang

2009-04-08

Soft collagenous tissue features many hierarchies of structure, starting from tropocollagen molecules that form fibrils, and proceeding to a bundle of fibrils that form fibers. Here we report the development of an atomistically informed continuum model of collagenous tissue. Results from full atomistic and molecular modeling are linked with a continuum theory of a fiber-reinforced composite, handshaking the fibril scale to the fiber and continuum scale in a hierarchical multi-scale simulation approach. Our model enables us to study the continuum-level response of the tissue as a function of cross-link density, making a link between nanoscale collagen features and material properties at larger tissue scales. The results illustrate a strong dependence of the continuum response as a function of nanoscopic structural features, providing evidence for the notion that the molecular basis for protein materials is important in defining their larger-scale mechanical properties. © 2009 Biomedical Engineering Society.

Current review and a simplified "five-point management algorithm" for keratoconus

Directory of Open Access Journals (Sweden)

Rohit Shetty

2015-01-01

Full Text Available Keratoconus is a slowly progressive, noninflammatory ectatic corneal disease characterized by changes in corneal collagen structure and organization. Though the etiology remains unknown, novel techniques are continuously emerging for the diagnosis and management of the disease. Demographical parameters are known to affect the rate of progression of the disease. Common methods of vision correction for keratoconus range from spectacles and rigid gas-permeable contact lenses to other specialized lenses such as piggyback, Rose-K or Boston scleral lenses. Corneal collagen cross-linking is effective in stabilizing the progression of the disease. Intra-corneal ring segments can improve vision by flattening the cornea in patients with mild to moderate keratoconus. Topography-guided custom ablation treatment betters the quality of vision by correcting the refractive error and improving the contact lens fit. In advanced keratoconus with corneal scarring, lamellar or full thickness penetrating keratoplasty will be the treatment of choice. With such a wide spectrum of alternatives available, it is necessary to choose the best possible treatment option for each patient. Based on a brief review of the literature and our own studies we have designed a five-point management algorithm for the treatment of keratoconus.

Mimicking corneal stroma using keratocyte-loaded photopolymerizable methacrylated gelatin hydrogels.

Science.gov (United States)

Kilic Bektas, Cemile; Hasirci, Vasif

2018-04-01

Cell-laden methacrylated gelatin (GelMA) hydrogels with high (approximately 90%) transparency were prepared to mimic the natural form and function of corneal stroma. They were synthesized from GelMA with a methacrylation degree of 70% as determined by nuclear magnetic resonance. Hydrogels were strong enough to withstand handling. Stability studies showed that 87% of the GelMA hydrogels remained after 21 days in phosphate buffered saline (PBS). Cell viability in the first 2 days was over 90% for the human keratocytes loaded in the gels as determined with the live-dead analysis. Cells in the hydrogel elongated and connected to each other as observed by confocal laser scanning microscopy (CLSM) images and scanning electron microscope analysis after 3 weeks in the culture medium and cells were seen to be distributed throughout the hydrogel bulk. Cells were found to synthesize collagen Types I and V, decorin, and biglycan (representative collagens and proteoglycans of human corneal stroma, respectively) showing that keratocytes maintained their functions and preserved their phenotypes in the hydrogels. Transparency of cell-loaded and cell-free hydrogels after 21 days was found to be over 90% at all time points in the visible light range and was comparable to the transparency of the native cornea. The corneal stroma equivalent produced in this study that has cells entrapped in it leads to a product with homogenous distribution of cells. It was transparent at the very beginning and is expected to allow better vision than nontransparent substrates. It, therefore, has a significant potential to be used as an alternative to the current products used to treat corneal blindness. Copyright © 2017 John Wiley & Sons, Ltd.

Validation of Na,K-ATPase pump function of corneal endothelial cells for corneal regenerative medicine.

Science.gov (United States)

Hatou, Shin; Higa, Kazunari; Inagaki, Emi; Yoshida, Satoru; Kimura, Erika; Hayashi, Ryuhei; Tsujikawa, Motokazu; Tsubota, Kazuo; Nishida, Kohji; Shimmura, Shigeto

2013-12-01

Tissue-engineering approaches to cultivate corneal endothelial cells (CECs) or induce CECs from stem cells are under investigation for the treatment of endothelial dysfunction. Before clinical application, a validation method to determine the quality of these cells is required. In this study, we quantified the endothelial pump function required for maintaining the corneal thickness using rabbit CECs (RCECs) and a human CEC line (B4G12). The potential difference of RCECs cultured on a permeable polyester membrane (Snapwell), B4G12 cells on Snapwell, or B4G12 cells on a collagen membrane (CM6) was measured by an Ussing chamber system, and the effect of different concentrations of ouabain (Na,K-ATPase specific inhibitor) was obtained. A mathematical equation derived from the concentration curve revealed that 2 mM ouabain decreases pump function of RCECs to 1.0 mV, and 0.6 mM ouabain decreases pump function of B4G12 on CM6 to 1.0 mV. Ouabain injection into the anterior chamber of rabbit eyes at a concentration of pump function >1.0 mV is required to maintain the corneal thickness. These results can be used for standardization of CEC pump function and validation of tissue-engineered CEC sheets for clinical use.

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.

Investigation of Overrun-Processed Porous Hyaluronic Acid Carriers in Corneal Endothelial Tissue Engineering.

Directory of Open Access Journals (Sweden)

Jui-Yang Lai

Full Text Available Hyaluronic acid (HA is a linear polysaccharide naturally found in the eye and therefore is one of the most promising biomaterials for corneal endothelial regenerative medicine. This study reports, for the first time, the development of overrun-processed porous HA hydrogels for corneal endothelial cell (CEC sheet transplantation and tissue engineering applications. The hydrogel carriers were characterized to examine their structures and functions. Evaluations of carbodiimide cross-linked air-dried and freeze-dried HA samples were conducted simultaneously for comparison. The results indicated that during the fabrication of freeze-dried HA discs, a technique of introducing gas bubbles in the aqueous biopolymer solutions can be used to enlarge pore structure and prevent dense surface skin formation. Among all the groups studied, the overrun-processed porous HA carriers show the greatest biological stability, the highest freezable water content and glucose permeability, and the minimized adverse effects on ionic pump function of rabbit CECs. After transfer and attachment of bioengineered CEC sheets to the overrun-processed HA hydrogel carriers, the therapeutic efficacy of cell/biopolymer constructs was tested using a rabbit model with corneal endothelial dysfunction. Clinical observations including slit-lamp biomicroscopy, specular microscopy, and corneal thickness measurements showed that the construct implants can regenerate corneal endothelium and restore corneal transparency at 4 weeks postoperatively. Our findings suggest that cell sheet transplantation using overrun-processed porous HA hydrogels offers a new way to reconstruct the posterior corneal surface and improve endothelial tissue function.

Low temperature corneal laser welding investigated by atomic force microscopy

Science.gov (United States)

Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

2009-02-01

The structural modifications in the stromal matrix induced by low-temperature corneal laser welding were investigated by atomic force microscopy (AFM). This procedure consists of staining the wound with Indocyanine Green (ICG), followed by irradiation with a near-infrared laser operated at low-power densities. This induces a local heating in the 55-65 °C range. In welded tissue, extracellular components undergo heat-induced structural modifications, resulting in a joining effect between the cut edges. However, the exact mechanism generating the welding, to date, is not completely understood. Full-thickness cuts, 3.5 mm in length, were made in fresh porcine cornea samples, and these were then subjected to laser welding operated at 16.7 W/cm2 power density. AFM imaging was performed on resin-embedded semi-thin slices once they had been cleared by chemical etching, in order to expose the stromal bulk of the tissue within the section. We then carried out a morphological analysis of characteristic fibrillar features in the laser-treated and control samples. AFM images of control stromal regions highlighted well-organized collagen fibrils (36.2 +/- 8.7 nm in size) running parallel to each other as in a typical lamellar domain. The fibrils exhibited a beaded pattern with a 22-39 nm axial periodicity. Laser-treated corneal regions were characterized by a significant disorganization of the intralamellar architecture. At the weld site, groups of interwoven fibrils joined the cut edges, showing structural properties that were fully comparable with those of control regions. This suggested that fibrillar collagen is not denatured by low-temperature laser welding, confirming previous transmission electron microscopy (TEM) observations, and thus it is probably not involved in the closure mechanism of corneal cuts. The loss of fibrillar organization may be related to some structural modifications in some interfibrillar substance as proteoglycans or collagen VI. Furthermore, AFM

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

Shape-Memory Effects in Biopolymer Networks with Collagen-Like Transient Nodes

NARCIS (Netherlands)

Skrzeszewska, P.J.; Jong, L.N.; Wolf, de F.A.; Stuart, M.A.C.; Gucht, van der J.

2011-01-01

In this article we study shape-memory behavior of hydrogels, formed by biodegradable and biocompatible recombinant telechelic polypeptides, with collagen-like end blocks and a random coil-like middle block. The programmed shape of these hydrogels was achieved by chemical cross-linking of lysine

Interference figures of polarimetric interferometry analysis of the human corneal stroma.

Directory of Open Access Journals (Sweden)

Rodolfo Mastropasqua

Full Text Available A rotating polarimetric 90°-cross linear-filter interferometry system was used to detect the morphological characteristics and features of interference patterns produced in in-vivo corneal stroma in healthy human corneas of 23 subjects. The characteristic corneal isogyres presenting with an evident cross-shaped pattern, grossly aligned with the fixation axis, were observed in all patients with centers within the pupillary dark area, impeding the exact determination of the center point. During the rotational scan in 78.3% of the eyes the cross-shaped pattern of the isogyre gradually separated to form two distinct hyperbolic arcs in opposite quadrants, reaching their maximal separation at 45 degrees with respect to angle of cross-shaped pattern formation. The corneal cross and hyperbolic-pattern repeated every 90° throughout the 360° rotational scan. While the interpretation of the isogyres presents particular difficulties, two summary parameters can be extracted for each cornea: the presence/orientation of a single or two dark areas in post-processed images and isochromes. However, the development of dedicated software for semi-quantitative analysis of these parameters and enantiomorphism may become available in the near future. The possible application of polarimetric interferometry in the field of both corneal pathologies and corneal surgery may be of great interest for clinical purposes.

Disorganized collagen scaffold interferes with fibroblast mediated deposition of organized extracellular matrix in vitro.

Science.gov (United States)

Saeidi, Nima; Guo, Xiaoqing; Hutcheon, Audrey E K; Sander, Edward A; Bale, Shyam Sundar; Melotti, Suzanna A; Zieske, James D; Trinkaus-Randall, Vickery; Ruberti, Jeffrey W

2012-10-01

Many tissue engineering applications require the remodeling of a degradable scaffold either in vitro or in situ. Although inefficient remodeling or failure to fully remodel the temporary matrix can result in a poor clinical outcome, very few investigations have examined in detail, the interaction of regenerative cells with temporary scaffoldings. In a recent series of investigations, randomly oriented collagen gels were directly implanted into human corneal pockets and followed for 24 months. The resulting remodeling response exhibited a high degree of variability which likely reflects differing regenerative/synthetic capacity across patients. Given this variability, we hypothesize that a disorganized, degradable provisional scaffold could be disruptive to a uniform, organized reconstruction of stromal matrix. In this investigation, two established corneal stroma tissue engineering culture systems (collagen scaffold-based and scaffold-free) were compared to determine if the presence of the disorganized collagen gel influenced matrix production and organizational control exerted by primary human corneal fibroblast cells (PHCFCs). PHCFCs were cultured on thin disorganized reconstituted collagen substrate (RCS--five donors: average age 34.4) or on a bare polycarbonate membrane (five donors: average age 32.4 controls). The organization and morphology of the two culture systems were compared over the long-term at 4, 8, and 11/12 weeks. Construct thickness and extracellular matrix organization/alignment was tracked optically with bright field and differential interference contrast (DIC) microscopy. The details of cell/matrix morphology and cell/matrix interaction were examined with standard transmission, cuprolinic blue and quick-freeze/deep-etch electron microscopy. Both the scaffold-free and the collagen-based scaffold cultures produced organized arrays of collagen fibrils. However, at all time points, the amount of organized cell-derived matrix in the scaffold

Collagen Fibrils: Nature's Highly Tunable Nonlinear Springs.

Science.gov (United States)

Andriotis, Orestis G; Desissaire, Sylvia; Thurner, Philipp J

2018-03-21

Tissue hydration is well known to influence tissue mechanics and can be tuned via osmotic pressure. Collagen fibrils are nature's nanoscale building blocks to achieve biomechanical function in a broad range of biological tissues and across many species. Intrafibrillar covalent cross-links have long been thought to play a pivotal role in collagen fibril elasticity, but predominantly at large, far from physiological, strains. Performing nanotensile experiments of collagen fibrils at varying hydration levels by adjusting osmotic pressure in situ during atomic force microscopy experiments, we show the power the intrafibrillar noncovalent interactions have for defining collagen fibril tensile elasticity at low fibril strains. Nanomechanical tensile tests reveal that osmotic pressure increases collagen fibril stiffness up to 24-fold in transverse (nanoindentation) and up to 6-fold in the longitudinal direction (tension), compared to physiological saline in a reversible fashion. We attribute the stiffening to the density and strength of weak intermolecular forces tuned by hydration and hence collagen packing density. This reversible mechanism may be employed by cells to alter their mechanical microenvironment in a reversible manner. The mechanism could also be translated to tissue engineering approaches for customizing scaffold mechanics in spatially resolved fashion, and it may help explain local mechanical changes during development of diseases and inflammation.

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.

Effects of edible bird's nest (EBN on cultured rabbit corneal keratocytes

Directory of Open Access Journals (Sweden)

Hun Lee

2011-10-01

Full Text Available Abstract Background There has been no effective treatment or agent that is available for corneal injury in promoting corneal wound healing. Previous studies on edible bird's nest extract (EBN had reported the presence of hormone-like substance; avian epidermal growth factor that could stimulate cell division and enhance regeneration. This study aimed to investigate the effects of EBN on corneal keratocytes proliferative capacity and phenotypical changes. Methods Corneal keratocytes from six New Zealand White Rabbits were isolated and cultured until Passage 1. The proliferative effects of EBN on corneal keratocytes were determined by MTT assay in serum-containing medium (FDS and serum-free medium (FD. Keratocytes phenotypical changes were morphologically assessed and gene expression of aldehyde dehydrogenase (ALDH, collagen type 1 and lumican were determined through RT-PCR. Results The highest cell proliferation was observed when both media were supplemented with 0.05% and 0.1% EBN. Cell proliferation was also consistently higher in FDS compared to FD. Both phase contrast micrographs and gene expression analysis confirmed the corneal keratocytes retained their phenotypes with the addition of EBN. Conclusions These results suggested that low concentration of EBN could synergistically induce cell proliferation, especially in serum-containing medium. This could be a novel breakthrough as both cell proliferation and functional maintenance are important during corneal wound healing. The in vitro test is considered as a crucial first step for nutri-pharmaceutical formation of EBN-based eye drops before in vivo application.

Controlling human corneal stromal stem cell contraction to mediate rapid cell and matrix organization of real architecture for 3-dimensional tissue equivalents.

Science.gov (United States)

Mukhey, Dev; Phillips, James B; Daniels, Julie T; Kureshi, Alvena K

2018-02-01

The architecture of the human corneal stroma consists of a highly organized extracellular matrix (ECM) interspersed with keratocytes. Their progenitor cells; corneal stromal stem cells (CSSC) are located at the periphery, in the limbal stroma. A highly organized corneal ECM is critical for effective transmission of light but this structure may be compromised during injury or disease, resulting in loss of vision. Re-creating normal organization in engineered tissue equivalents for transplantation often involves lengthy culture times that are inappropriate for clinical use or utilisation of synthetic substrates that bring complications such as corneal melting. CSSC have great therapeutic potential owing to their ability to reorganize a disorganized matrix, restoring transparency in scarred corneas. We examined CSSC contractile behavior to assess whether this property could be exploited to rapidly generate cell and ECM organization in Real Architecture For 3D Tissues (RAFT) tissue equivalents (TE) for transplantation. Free-floating collagen gels were characterized to assess contractile behavior of CSSC and establish optimum cell density and culture times. To mediate cell and collagen organization, tethered collagen gels seeded with CSSC were cultured and subsequently stabilized with the RAFT process. We demonstrated rapid creation of biomimetic RAFT TE with tunable structural properties. These displayed three distinct regions of varying degrees of cellular and collagen organization. Interestingly, increased organization coincided with a dramatic loss of PAX6 expression in CSSC, indicating rapid differentiation into keratocytes. The organized RAFT TE system could be a useful bioengineering tool to rapidly create an organized ECM while simultaneously controlling cell phenotype. For the first time, we have demonstrated that human CSSC exhibit the phenomenon of cellular self-alignment in tethered collagen gels. We found this mediated rapid co-alignment of collagen fibrils

Collagen-Gold Nanoparticle Conjugates for Versatile Biosensing

Directory of Open Access Journals (Sweden)

Sarah Unser

2017-02-01

Full Text Available Integration of noble metal nanoparticles with proteins offers promising potential to create a wide variety of biosensors that possess both improved selectivity and versatility. The multitude of functionalities that proteins offer coupled with the unique optical properties of noble metal nanoparticles can allow for the realization of simple, colorimetric sensors for a significantly larger range of targets. Herein, we integrate the structural protein collagen with 10 nm gold nanoparticles to develop a protein-nanoparticle conjugate which possess the functionality of the protein with the desired colorimetric properties of the nanoparticles. Applying the many interactions that collagen undergoes in the extracellular matrix, we are able to selectively detect both glucose and heparin with the same collagen-nanoparticle conjugate. Glucose is directly detected through the cross-linking of the collagen fibrils, which brings the attached nanoparticles into closer proximity, leading to a red-shift in the LSPR frequency. Conversely, heparin is detected through a competition assay in which heparin-gold nanoparticles are added to solution and compete with heparin in the solution for the binding sites on the collagen fibrils. The collagen-nanoparticle conjugates are shown to detect both glucose and heparin in the physiological range. Lastly, glucose is selectively detected in 50% mouse serum with the collagen-nanoparticle devices possessing a linear range of 3–25 mM, which is also within the physiologically relevant range.

Intrastromal corneal ring implants for corneal thinning disorders: an evidence-based analysis.

Science.gov (United States)

2009-01-01

progressively thins causing a cone-like bulge or forward protrusion in response to the normal pressure of the eye. Thinning occurs primarily in the stoma layers and is believed to be a breakdown in the collagen network. This bulging can lead to an irregular shape or astigmatism of the cornea and, because the anterior part of the cornea is largely responsible for the focusing of light on the retina, results in loss of visual acuity. This can make even simple daily tasks, such as driving, watching television or reading, difficult to perform. Keratoconus (KC) is the most common form of corneal thinning disorder and is a noninflammatory chronic disease process. Although the specific causes of the biomechanical alterations that occur in KC are unknown, there is a growing body of evidence to suggest that genetic factors may play an important role. KC is a rare condition (management for this condition follows a step-wise approach depending on disease severity. Contact lenses are the primary treatment of choice when there is irregular astigmatism associated with the disease. When patients can no longer tolerate contact lenses or when lenses no longer provide adequate vision, patients are referred for corneal transplant. Keratoconus is one of the leading indications for corneal transplants and has been so for the last three decades. Yet, despite high graft survival rates of up to 20 years, there are reasons to defer receiving transplants for as long as possible. Patients with keratoconus are generally young and life-long term graft survival would be an important consideration. The surgery itself involves lengthy time off work and there are potential complications from long term steroid use following surgery, as well as the risk of developing secondary cataracts, glaucoma etc. After transplant, recurrent KC is possible with need for subsequent intervention. Residual refractive errors and astigmatism can remain challenging after transplantation and high refractive surgery rates and re

The potential role of bioengineering and three-dimensional printing in curing global corneal blindness.

Science.gov (United States)

Ludwig, Parker E; Huff, Trevor J; Zuniga, Jorge M

2018-01-01

An insufficiency of accessible allograft tissue for corneal transplantation leaves many impaired by untreated corneal disease. There is promise in the field of regenerative medicine for the development of autologous corneal tissue grafts or collagen-based scaffolds. Another approach is to create a suitable corneal implant that meets the refractive needs of the cornea and is integrated into the surrounding tissue but does not attempt to perfectly mimic the native cornea on a cellular level. Materials that have been investigated for use in the latter concept include natural polymers such as gelatin, semisynthetic polymers like gelatin methacrylate, and synthetic polymers. There are advantages and disadvantages inherent in natural and synthetic polymers: natural polymers are generally more biodegradable and biocompatible, while synthetic polymers typically provide greater control over the characteristics or property adjustment of the materials. Additive manufacturing could aid in the precision production of keratoprostheses and the personalization of implants.

Effect of Vaginal or Systemic Estrogen on Dynamics of Collagen Assembly in the Rat Vaginal Wall1

Science.gov (United States)

Montoya, T. Ignacio; Maldonado, P. Antonio; Acevedo, Jesus F.; Word, R. Ann

2014-01-01

ABSTRACT The objective of this study was to compare the effects of systemic and local estrogen treatment on collagen assembly and biomechanical properties of the vaginal wall. Ovariectomized nulliparous rats were treated with estradiol or conjugated equine estrogens (CEEs) either systemically, vaginal CEE, or vaginal placebo cream for 4 wk. Low-dose local CEE treatment resulted in increased vaginal epithelial thickness and significant vaginal growth without uterine hyperplasia. Furthermore, vaginal wall distensibility increased without compromise of maximal force at failure. Systemic estradiol resulted in modest increases in collagen type I with no change in collagen type III mRNA. Low-dose vaginal treatment, however, resulted in dramatic increases in both collagen subtypes whereas moderate and high dose local therapies were less effective. Consistent with the mRNA results, low-dose vaginal estrogen resulted in increased total and cross-linked collagen content. The inverse relationship between vaginal dose and collagen expression may be explained in part by progressive downregulation of estrogen receptor-alpha mRNA with increasing estrogen dose. We conclude that, in this menopausal rat model, local estrogen treatment increased total and cross-linked collagen content and markedly stimulated collagen mRNA expression in an inverse dose-effect relationship. High-dose vaginal estrogen resulted in downregulation of estrogen receptor-alpha and loss of estrogen-induced increases in vaginal collagen. These results may have important clinical implications regarding the use of local vaginal estrogen therapy and its role as an adjunctive treatment in women with loss of vaginal support. PMID:25537371

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.

Lithium polymer cell assembled by in situ chemical cross-linking of ionic liquid electrolyte with phosphazene-based cross-linking agent

International Nuclear Information System (INIS)

Choi, Ji-Ae; Kang, Yongku; Kim, Dong-Won

2013-01-01

Highlights: ► Ionic liquid-based cross-linked gel polymer electrolytes were synthesized and their electrochemical properties were investigated. ► Lithium polymer cells with in situ cross-linked gel polymer electrolytes exhibited reversible cycling behavior with good capacity retention. ► The use of ionic liquid-based cross-linked gel polymer electrolytes significantly improved the thermal stability of the cells. -- Abstract: Ionic liquid-based cross-linked gel polymer electrolytes were prepared with a phosphazene-based cross-linking agent, and their electrochemical properties were investigated. Lithium polymer cells composed of lithium anode and LiCoO 2 cathode were assembled with ionic liquid-based cross-linked gel polymer electrolyte and their cycling performance was evaluated. The interfacial adhesion between the electrodes and the electrolyte by in situ chemical cross-linking resulted in stable capacity retention of the cell. A reduction in the ionic mobility in both the electrolyte and the electrode adversely affected discharge capacity and high rate performance of the cell. DSC studies demonstrated that the use of ionic liquid-based cross-linked gel polymer electrolytes provided a significant improvement in the thermal stability of the cell

Alpha-ketoglutarate decreases serum levels of C-terminal cross-linking telopeptide of type I collagen (CTX) in postmenopausal women with osteopenia: six-month study.

Science.gov (United States)

Filip, Rafał S; Pierzynowski, Stefan G; Lindegard, Birger; Wernerman, Jan; Haratym-Maj, Agnieszka; Podgurniak, Małgorzata

2007-03-01

Several studies have shown that alpha-ketoglutaric acid (AKG) increases serum levels of proline and has beneficial effects on skeletal development. We studied the effect of alpha-ketoglutaric (AKG) acid calcium salt (6 g AKG and 1.68 Ca/day) or calcium alone (1.68 Ca/day) on serum C-terminal cross-linked telopeptide of type I collagen (CTX) and osteocalcin (OC), as well as on lumbar spine bone mineral density (BMD) in a randomized, parallel group, double-blind, 6-month study conducted on 76 postmenopausal women with osteopenia. The maximum decrease of the mean CTX level in the AKG-Ca group was observed after 24 weeks (37.0%, p = 0.006). The differences in CTX between study groups were statistically significant after 12 and 24 weeks. The OC serum level was not affected by treatments. The BMD of the AKG-Ca group increased by 1.6% from baseline; however, the difference between treatment groups was estimated as 0.9% (non-significant). This study suggests the potential usefulness of AKG-Ca in osteopenic postmenopausal women. AKG-Ca induced beneficial changes in serum CTX, which was consistent with preserving the bone mass in the lumbar spine; however, the long-term effect needs to be further investigated.

Mechanisms of Plastic Deformation in Collagen Networks Induced by Cellular Forces.

Science.gov (United States)

Ban, Ehsan; Franklin, J Matthew; Nam, Sungmin; Smith, Lucas R; Wang, Hailong; Wells, Rebecca G; Chaudhuri, Ovijit; Liphardt, Jan T; Shenoy, Vivek B

2018-01-23

Contractile cells can reorganize fibrous extracellular matrices and form dense tracts of fibers between neighboring cells. These tracts guide the development of tubular tissue structures and provide paths for the invasion of cancer cells. Here, we studied the mechanisms of the mechanical plasticity of collagen tracts formed by contractile premalignant acinar cells and fibroblasts. Using fluorescence microscopy and second harmonic generation, we quantified the collagen densification, fiber alignment, and strains that remain within the tracts after cellular forces are abolished. We explained these observations using a theoretical fiber network model that accounts for the stretch-dependent formation of weak cross-links between nearby fibers. We tested the predictions of our model using shear rheology experiments. Both our model and rheological experiments demonstrated that increasing collagen concentration leads to substantial increases in plasticity. We also considered the effect of permanent elongation of fibers on network plasticity and derived a phase diagram that classifies the dominant mechanisms of plasticity based on the rate and magnitude of deformation and the mechanical properties of individual fibers. Plasticity is caused by the formation of new cross-links if moderate strains are applied at small rates or due to permanent fiber elongation if large strains are applied over short periods. Finally, we developed a coarse-grained model for plastic deformation of collagen networks that can be employed to simulate multicellular interactions in processes such as morphogenesis, cancer invasion, and fibrosis. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Cross-ancestry genome-wide association analysis of corneal thickness strengthens link between complex and Mendelian eye diseases

OpenAIRE

Iglesias, Adriana I; Mishra, Aniket; Vitart, Veronique; Bykhovskaya, Yelena; Höhn, René; Springelkamp, Henriët; Cuellar-Partida, Gabriel; Gharahkhani, Puya; Bailey, Jessica N Cooke; Willoughby, Colin E; Li, Xiaohui; Yazar, Seyhan; Nag, Abhishek; Khawaja, Anthony P.; Polasek, Ozren

2018-01-01

Central corneal thickness (CCT) is a highly heritable trait associated with complex eye diseases such as keratoconus and glaucoma. We perform a genome-wide association meta-analysis of CCT and identify 19 novel regions. Pathway analyses uncover new, as well as supported the role of connective tissue-related, pathways. Remarkably, >20% of the CCT-loci are near or within Mendelian disorder genes. These included FBN1, ADAMTS2 and TGFB2 which associate with connective tissue disorders (Marfan,...

Intrastromal corneal ring segments for management of keratoconus

Directory of Open Access Journals (Sweden)

Sri Ganesh

2013-01-01

Full Text Available Keratoconus is a progressive corneal ectasia, which can be managed both by conservative measures like glasses or contact lenses in non-progressive cases or surgical procedures like collagen crosslinking (CXL with or without adjuvant measures like intrastromal corneal rings segments (ICRS or topography guided ablation. Various kinds of ICRS are available to the surgeon, but it is most essential to be able to plan the implantation of the ring to optimize outcomes. Aims: The aim of this study is to evaluate the visual outcome and progression in patients of keratoconus implanted with ICRS. Materials and Methods: Two different types of ICRS-Intacs (Addition Technology and Kerarings (Mediphacos Inc. were implanted in 2 different cohorts of patients and were followed-up to evaluate the outcome of the procedure. All patients underwent a complete ocular examination including best spectacle corrected visual acuity, slit lamp examination fundus examination, corneal topography and pachymetry. The ICRS implantation is done with CXL to stop the progression of the disease. Improvement in uncorrected visual acuity (UCVA, best spectacle corrected visual acuity and topographic changes were analyzed. Results: A significant improvement in keratometry and vision was seen in both groups. Conclusion: ICRS have been found to reduce corneal irregularity and flatten keratometry with improvement in UCVA and best corrected visual acuity.

Mycobacterial laminin-binding histone-like protein mediates collagen-dependent cytoadherence

Directory of Open Access Journals (Sweden)

André Alves Dias

2012-12-01

Full Text Available When grown in the presence of exogenous collagen I, Mycobacterium bovis BCG was shown to form clumps. Scanning electron microscopy examination of these clumps revealed the presence of collagen fibres cross-linking the bacilli. Since collagen is a major constituent of the eukaryotic extracellular matrices, we assayed BCG cytoadherence in the presence of exogenous collagen I. Collagen increased the interaction of the bacilli with A549 type II pneumocytes or U937 macrophages, suggesting that BCG is able to recruit collagen to facilitate its attachment to host cells. Using an affinity chromatography approach, we have isolated a BCG collagen-binding protein corresponding to the previously described mycobacterial laminin-binding histone-like protein (LBP/Hlp, a highly conserved protein associated with the mycobacterial cell wall. Moreover, Mycobacterium leprae LBP/Hlp, a well-characterized adhesin, was also able to bind collagen I. Finally, using recombinant fragments of M. leprae LBP/Hlp, we mapped the collagen-binding activity within the C-terminal domain of the adhesin. Since this protein was already shown to be involved in the recognition of laminin and heparan sulphate-containing proteoglycans, the present observations reinforce the adhesive activities of LBP/Hlp, which can be therefore considered as a multifaceted mycobacterial adhesin, playing an important role in both leprosy and tuberculosis pathogenesis.

Collagen crosslinking for ectasia following PRK performed in excimer laser-assisted keratoplasty for keratoconus.

Science.gov (United States)

Spadea, Leopoldo

2012-01-01

To report the results of corneal collagen crosslinking (CXL) in a patient with corneal ectasia developed after excimer laser-assisted lamellar keratoplasty for keratoconus and a secondary photorefractive keratectomy (PRK) for residual refractive error. A 33-year-old woman, who had originally been treated for keratoconus in the right eye by excimer laser-assisted lamellar keratoplasty, subsequently had her residual ametropia treated by topographically guided, transepithelial excimer laser PRK. Five years after PRK, the patient developed corneal ectasia showing concomitant visual changes of best spectacle-corrected visual acuity (BSCVA) reduced to 20/33 with a refraction of -6.00 +6.00 × 30. The minimum corneal thickness at the ectasia apex was 406 µm. A treatment of riboflavin-UVA-induced corneal CXL was performed on the right eye. Two years after the CXL treatment, the right eye improved to 20/20 BSCVA with a refraction of plano +1.00 × 50 while exhibiting a clear lamellar graft. Corneal CXL provided safe and effective management of ectasia developed after excimer laser-assisted lamellar keratoplasty and PRK.

Type II collagen-hyaluronan hydrogel – a step towards a scaffold for intervertebral disc tissue engineering

Directory of Open Access Journals (Sweden)

L Calderon

2010-09-01

Full Text Available Intervertebral disc regeneration strategies based on stem cell differentiation in combination with the design of functional scaffolds is an attractive approach towards repairing/regenerating the nucleus pulposus. The specific aim of this study was to optimise a composite hydrogel composed of type II collagen and hyaluronic acid (HA as a carrier for mesenchymal stem cells. Hydrogel stabilisation was achieved by means of 1-ethyl-3(3-dimethyl aminopropyl carbodiimide (EDC and N-hydroxysuccinimide (NHS cross-linking. Optimal hydrogel properties were determined by investigating different concentrations of EDC (8mM, 24mM and 48mM. Stable hydrogels were obtained independent of the concentration of carbodiimide used. The hydrogels cross-linked by the lowest concentration of EDC (8mM demonstrated high swelling properties. Additionally, improved proliferation of seeded rat mesenchymal stem cells (rMSCs and hydrogel stability levels in culture were observed with this 8mM cross-linked hydrogel. Results from this study indicate that EDC/NHS (8mM cross-linked type II collagen/HA hydrogel was capable of supporting viability of rMSCs, and furthermore their differentiation into a chondrogenic lineage. Further investigations should be conducted to determine its potential as scaffold for nucleus pulposus regeneration/repair.

University students' knowledge of corneal donation and willingness to donate corneas in the occupied Palestinian territory: a cross-sectional study.

Science.gov (United States)

Al-Labadi, Liana; Gammoh, Yazan; Shehada, Reham; Shahin, Reem; Jbarah, Walaa; Amro, Madleen; Athamny, Hanan

2018-02-21

Access to corneal transplantation is limited worldwide because of poor knowledge. Ethical, religious, and cultural barriers contribute to low rates of corneal donation. In the occupied Palestinian territory, limited information is available on factors affecting corneal donation. The aim of this study was to assess the knowledge and willingness towards corneal donation in Palestinian students. This cross-sectional study included university students selected through convenience sampling in Nablus in the summer of 2016. The sample size was determined using the sample formulae and a 15% non-response rate. All students registered in obligatory courses were included in the study after verbal consent. Each participant was given a self-administered questionnaire consisting of 14 questions to assess knowledge, awareness, and willingness toward corneal donation. Frequencies were used for descriptive analysis, and associations were determined using multivariate analysis and χ 2 test, with a p value of less than 0·05 considered significant. Of the 634 students completing the questionnaire, 411 (65%) were women, 614 (97%) were Muslims, and 155 (25%) were health or medical students. 592 (93%) respondents were unaware of eye bank availability, and 407 (69%; p=0.002) of these respondents did not show willingness towards corneal donation. 431 (67%) respondents were aware of a lack in corneal donation, but 274 (64%; p=0·01) of these respondents did not show willingness towards corneal donation. 429 (68%) respondents were not willing to donate their corneas, the most common reasons being disapproval by family members and poor awareness. We found no association between sociodemographic factors and willingness was determined. Palestinian students are aware of the lack of local cornea donation but are unwilling to donate their corneas. The study results are not representative of the entire population because of the homogeneous nature of the sample. Large efforts are needed locally to

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...

Chitosan and thiolated chitosan: Novel therapeutic approach for preventing corneal haze after chemical injuries.

Science.gov (United States)

Zahir-Jouzdani, Forouhe; Mahbod, Mirgholamreza; Soleimani, Masoud; Vakhshiteh, Faezeh; Arefian, Ehsan; Shahosseini, Saeed; Dinarvand, Rasoul; Atyabi, Fatemeh

2018-01-01

Corneal haze, commonly caused by deep physical and chemical injuries, can greatly impair vision. Growth factors facilitate fibroblast proliferation and differentiation, which leads to haze intensity. In this study, the potential effect of chitosan (CS) and thiolated-chitosan (TCS) nanoparticles and solutions on inhibition of fibroblast proliferation, fibroblast to myofibroblast differentiation, neovascularization, extracellular matrix (ECM) deposition, and pro-fibrotic cytokine expression was examined. Transforming growth factor beta-1 (TGFβ 1 ) was induced by interleukin-6 (IL6) in human corneal fibroblasts and expression levels of TGFβ 1 , Platelet-derived growth factor (PDGF), α-smooth muscle actins (α-SMA), collagen type I (Col I), fibronectin (Fn) and vascular endothelial growth factor (VEGF) were quantified using qRT-PCR. To assess wound-healing capacity, TCS-treated mice were examined for α-SMA positive cells, collagen deposition, inflammatory cells and neovascularization through pathological immunohistochemistry. The results revealed that CS and TCS could down-regulate the expression levels of TGFβ 1 and PDGF comparable to that of TGFβ 1 knockdown experiment. However, down-regulation of TGFβ 1 was not regulated through miR29b induction. Neovascularization along with α-SMA and ECM deposition were significantly diminished. According to these findings, CS and TCS can be considered as potential anti-fibrotic and anti-angiogenic therapeutics. Furthermore, TCS, thiolated derivative of CS, will increase mucoadhesion of the polymer at the corneal surface which makes the polymer efficient and non-toxic therapeutic approach for corneal injuries. Copyright © 2017 Elsevier Ltd. All rights reserved.

Altered corneal biomechanical properties in children with osteogenesis imperfecta.

Science.gov (United States)

Lagrou, Lisa M; Gilbert, Jesse; Hannibal, Mark; Caird, Michelle S; Thomas, Inas; Moroi, Sayoko E; Bohnsack, Brenda L

2018-04-07

To evaluate biomechanical corneal properties in children with osteogenesis imperfecta (OI). A prospective, observational, case-control study was conducted on children 6-19 years of age diagnosed with OI. Patients with OI and healthy control subjects underwent complete ophthalmic examinations. Additional tests included Ocular Response Analyzer (ORA) and ultrasonic pachymetry. Primary outcomes were central corneal thickness (CCT), corneal hysteresis (CH), and corneal resistance factor (CRF). Intraocular pressure (IOP) was measured directly by either iCare or Goldmann applanation and indirectly by the ORA (Goldmann-correlated and corneal-compensated IOP). Statistically significant differences between OI and control groups were determined using independent samples t test. A total of 10 of 18 OI cases (mean age, 13 ± 4.37 years; 8 males) and 30 controls (mean age, 12.76 ± 2.62 years; 16 males) were able to complete the corneal biomechanics and pachymetry testing. Children with OI had decreased CH (8.5 ± 1.0 mm Hg vs 11.6 ± 1.2 mm Hg [P < 0.001]), CRF (9.0 ± 1.9 mm Hg vs 11.5 ± 1.5 [P < 0.001]) and CCT (449.8 ± 30.8 μm vs 568 ± 47.6 μm [P < 0.001]) compared to controls. The corneal-compensated IOP was significantly higher in OI cases (18.8 ± 3.1 mm Hg) than in controls (15.0 ± 1.6 mm Hg, P < 0.004), but there was no significant difference in Goldmann-correlated IOP (16.3 ± 4.2 mm Hg vs 15.8 ± 2.2 mm Hg). Collagen defects in OI alter corneal structure and biomechanics. Children with OI have decreased CH, CRF, and CCT, resulting in IOPs that are likely higher than measured by tonometry. These corneal alterations are present at a young age in OI. Affected individuals should be routinely screened for glaucoma and corneal pathologies. Copyright © 2018 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.

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.

Validity of autorefractor based screening method for irregular astigmatism compared to the corneal topography- a cross sectional study

Directory of Open Access Journals (Sweden)

Alicia Galindo-Ferreiro

2017-09-01

Full Text Available AIM: To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography. METHODS: This cross-sectional validity study was conducted in 2013 at an eye hospital in Spain. A tabletop autorefractor (test 1 was used to measure the refractive status of the anterior surface of the cornea at two corneal meridians of each eye. Then corneal topography (test 2 and Bogan’s classification was used to group eyes into those with regular or no astigmatism (GRI and irregular astigmatism (GRII. Test 1 provided a single absolute value for the greatest cylinder difference (Vr. The receiver operating characteristic (ROC were plotted for the Vr values measured by test 1 for GRI and GRII eyes. On the basis a Vr value of 1.25 D as cut off, sensitivity, specificity were also calculated. RESULTS: The study sample was comprised of 260 eyes (135 patients. The prevalence of irregular astigmatism was 42% [95% confidence interval (CI: 36, 48]. Based on test 2, there were 151 eyes in GRI and 109 eyes in GRII. The median Vr was 0.75 D (25% quartile, 0.5 D for GRI and 1.75 D (25% quartile, 1.25 D for GRII. The area under curve was 0.171 for GRI and 0.83 for GRII. The sensitivity of test I was 78.1% and the specificity was 76.1%. CONCLUSION: A conventional autorefractor can be effective as a first level screening method to detect irregular corneal astigmatism in places where corneal topography facilities are not available.

In vitro evaluation of the interactions between human corneal endothelial cells and extracellular matrix proteins

International Nuclear Information System (INIS)

Choi, Jin San; Kim, Eun Young; Kim, Min Jeong; Giegengack, Matthew; Khan, Faraaz A; Soker, Shay; Khang, Gilson

2013-01-01

The corneal endothelium is the innermost cell layer of the cornea and rests on Descemet's membrane consisting of various extracellular matrix (ECM) proteins which can directly affect the cellular behaviors such as cell adhesion, proliferation, polarity, morphogenesis and function. The objective of this study was to investigate the interactions between the ECM environment and human corneal endothelial cells (HCECs), with the ultimate goal to improve cell proliferation and function in vitro. To evaluate the interaction of HCECs with ECM proteins, cells were seeded on ECM-coated tissue culture dishes, including collagen type I (COL I), collagen type IV (COL IV), fibronectin (FN), FNC coating mix (FNC) and laminin (LM). Cell adhesion and proliferation of HCECs on each substratum and expression of CEC markers were studied. The results showed that HCECs plated on the COL I, COL IV, FN and FNC-coated plates had enhanced cell adhesion initially; the number for COL I, COL IV, FN and FNC was significantly higher than the control (P < 0.05). In addition, cells grown on ECM protein-coated dishes showed more compact cellular morphology and CEC marker expression compared to cells seeded on uncoated dishes. Collectively, our results suggest that an adequate ECM protein combination can provide a long-term culture environment for HCECs for corneal endothelium transplantation. (paper)

Prevalence and causes of corneal blindness.

Science.gov (United States)

Wang, Haijing; Zhang, Yaoguang; Li, Zhijian; Wang, Tiebin; Liu, Ping

2014-04-01

The study aimed to assess the prevalence and causes of corneal blindness in a rural northern Chinese population. Cross-sectional study. The cluster random sampling method was used to select the sample. This population-based study included 11 787 participants of all ages in rural Heilongjiang Province, China. These participants underwent a detailed interview and eye examination that included the measurement of visual acuity, slit-lamp biomicroscopy and direct ophthalmoscopy. An eye was considered to have corneal blindness if the visual acuity was blindness and low vision. Among the 10 384 people enrolled in the study, the prevalence of corneal blindness is 0.3% (95% confidence interval 0.2-0.4%). The leading cause was keratitis in childhood (40.0%), followed by ocular trauma (33.3%) and keratitis in adulthood (20.0%). Age and illiteracy were found to be associated with an increased prevalence of corneal blindness. Blindness because of corneal diseases in rural areas of Northern China is a significant public health problem that needs to be given more attention. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

Development of a nanofiltration method for bone collagen {sup 14}C AMS dating

Energy Technology Data Exchange (ETDEWEB)

Boudin, Mathieu, E-mail: mathieu.boudin@ugent.be [Royal Institute for Cultural Heritage, Jubelpark 1, B-1000 Brussels (Belgium); Ghent University, Faculty of Bioscience Engineering, Laboratory of Applied Physical Chemistry, Coupure Links 653, B-9000 Ghent (Belgium); Boeckx, Pascal [Ghent University, Faculty of Bioscience Engineering, Laboratory of Applied Physical Chemistry, Coupure Links 653, B-9000 Ghent (Belgium); Buekenhoudt, Anita [Flemish Institute for Technological Research, Separation and Conversion Technology, Boeretang 200, B-2400 Mol (Belgium); Vandenabeele, Peter [Ghent University, Department of Archaeology, Sint-Pietersnieuwstraat 35, B-9000 Ghent (Belgium); Van Strydonck, Mark [Royal Institute for Cultural Heritage, Jubelpark 1, B-1000 Brussels (Belgium)

2013-01-15

Radiocarbon dating of bones is usually performed on the collagen fraction. However, this collagen can contain exogenous molecules, including humic substances (HSs) and/or other soil components that may have a different age than the bone. Incomplete removal can result in biased {sup 14}C dates. Ultrafiltration of collagen, dissolved as gelatin (molecular weight (MW) {approx}100,000 Dalton), has received considerable attention to obtain more reliable dates. Ultrafiltration is an effective method of removal of low-molecular weight contaminants from bone collagen but it does not remove high-molecular weight contaminants, such as cross-linked humic collagen complexes. However, comparative dating studies have raised the question whether this cleaning step itself may introduce contamination with carbon from the filters used. In this study, a nanofiltration method was developed using a ceramic filter to avoid a possible extraneous carbon contamination introduced by the filter. This method should be applicable to various protein materials e.g. collagen, silk, wool, leather and should be able to remove low-molecular and high molecular weight HSs. In this study bone collagen was hot acid hydrolyzed to amino acids and nanofiltrated. A filter with a molecular weight cutoff (MWCO) of 450 Dalton was chosen in order to collect the amino acids in the permeate and the HSs in the retentate. Two pilot studies were set up. Two nanofiltration types were tested in pilot study 1: dead end and cross flow filtration. Humic substance (HS)-solutions with fossil carbon and modern hydrolyzed collagen contaminated with HSs were filtrated and analyzed with spectrofluorescence to determine the HS removal. Cross flow nanofiltration showed the most efficient HS removal. A second pilot study based upon these results was set up wherein only cross flow filtration was performed. {sup 14}C measurements of the permeates of hydrolyzed modern collagen contaminated with fossil HSs demonstrate a significant

An age-related study of morphology and cross-link composition of collagen fibrils in the digital flexor tendons of young thoroughbred horses.

Science.gov (United States)

Patterson-Kane, J C; Parry, D A; Birch, H L; Goodship, A E; Firth, E C

1997-01-01

The superficial digital flexor tendon is the most commonly injured tendon in the racing Thoroughbred. Despite the clinical significance of this structure, only limited data exist regarding normal age-related morphology of the tensile units, the collagen fibrils. The age at which these collagen fibrils become mature in composition and structure may be of importance. Consequently, the association of age and collagen fibril crosslink composition, diameter distribution and crimp morphology in the superficial and deep digital flexor tendons of Thoroughbreds up to and including three years of age has been studied. Replacement of immature crosslinks, peaking of the collagen fibril mass-average diameter and collagen fibril index, and stabilization of collagen crimp morphology changes supported the hypothesis that both digital flexor tendons become mature in structure by two years of age.

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.

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.

Bilateral congenital corneal keloids and anterior segment mesenchymal dysgenesis in a case of Rubinstein-Taybi syndrome.

Science.gov (United States)

Rao, Srinivas K; Fan, Dorothy S P; Pang, C P; Li, Winnie W Y; Ng, Joan S K; Good, William V; Lam, Dennis S C

2002-01-01

To report the unusual association of bilateral corneal keloids and anterior segment mesenchymal dysgenesis in a child with Rubinstein-Taybi syndrome. Case report of a 2-year-old boy. Excision of the epicorneal mass in the right eye was followed by recurrence of the lesion. Multiple penetrating keratoplasties were unsuccessful in reconstructing the anterior segment because of recurrent corneal epithelial breakdown, suggesting limbal stem cell insufficiency. Histopathology and electron microscopy of the excised mass lesion showed features typical of a corneal keloid: thickened keratinized epithelium, absent Bowman's layer, and fibrovascular hyperplasia, with haphazard orientation of the collagen lamellae. Ultrasound biomicroscopy and intraoperative findings suggested a diagnosis of Peter anomaly, but genetic analysis did not show a PAX6 mutation. The findings in our patient add to the spectrum of ocular changes described in Rubinstein-Taybi syndrome and confirm earlier reports of poor ocular prognosis in corneal keloids and Rubinstein-Taybi syndrome.

Removal of the basement membrane enhances corneal wound healing.

Science.gov (United States)

Pal-Ghosh, Sonali; Pajoohesh-Ganji, Ahdeah; Tadvalkar, Gauri; Stepp, Mary Ann

2011-12-01

Recurrent corneal erosions are painful and put patients' vision at risk. Treatment typically begins with debridement of the area around the erosion site followed by more aggressive treatments. An in vivo mouse model has been developed that reproducibly induces recurrent epithelial erosions in wild-type mice spontaneously within two weeks after a single 1.5 mm corneal debridement wound created using a dulled-blade. This study was conducted to determine whether 1) inhibiting MMP9 function during healing after dulled-blade wounding impacts erosion development and 2) wounds made with a rotating-burr heal without erosions. Oral or topical inhibition of MMPs after dulled-blade wounding does not improve healing. Wounds made by rotating-burr heal with significantly fewer erosions than dulled-blade wounds. The localization of MMP9, β4 integrin and basement membrane proteins (LN332 and type VII collagen), immune cell influx, and reinnervation of the corneal nerves were compared after both wound types. Rotating-burr wounds remove the anterior basement membrane centrally but not at the periphery near the wound margin, induce more apoptosis of corneal stromal cells, and damage more stromal nerve fibers. Despite the fact that rotating-burr wounds do more damage to the cornea, fewer immune cells are recruited and significantly more wounds resolve completely. Copyright © 2011 Elsevier Ltd. All rights reserved.

Nitric oxide-induced interstrand cross-links in DNA.

Science.gov (United States)

Caulfield, Jennifer L; Wishnok, John S; Tannenbaum, Steven R

2003-05-01

The DNA damaging effects of nitrous acid have been extensively studied, and the formation of interstrand cross-links have been observed. The potential for this cross-linking to occur through a common nitrosating intermediate derived from nitric oxide is investigated here. Using a HPLC laser-induced fluorescence (LIF) system, the amount of interstrand cross-link formed on nitric oxide treatment of the 5'-fluorescein-labeled oligomer ATATCGATCGATAT was determined. This self-complimentary sequence contains two 5'-CG sequences, which is the preferred site for nitrous acid-induced cross-linking. Nitric oxide was delivered to an 0.5 mM oligomer solution at 15 nmol/mL/min to give a final nitrite concentration of 652 microM. The resulting concentration of the deamination product, xanthine, in this sample was found to be 211 +/- 39 nM, using GC/MS, and the amount of interstrand cross-link was determined to be 13 +/- 2.5 nM. Therefore, upon nitric oxide treatment, the cross-link is found at approximately 6% of the amount of the deamination product. Using this system, detection of the cross-link is also possible for significantly lower doses of nitric oxide, as demonstrated by treatment of the same oligomer with NO at a rate of 18 nmol/mL/min resulting in a final nitrite concentration of 126 microM. The concentration of interstrand cross-link was determined to be 3.6 +/- 0.1 nM in this sample. Therefore, using the same dose rate, when the total nitric oxide concentration delivered drops by a factor of approximately 5, the concentration of cross-link drops by a factor of about 4-indicating a qausi-linear response. It may now be possible to predict the number of cross-links in a small genome based on the number of CpG sequences and the yield of xanthine derived from nitrosative deamination.

Response of human corneal fibroblasts on silk film surface patterns.

Science.gov (United States)

Gil, Eun Seok; Park, Sang-Hyug; Marchant, Jeff; Omenetto, Fiorenzo; Kaplan, David L

2010-06-11

Transparent, biodegradable, mechanically robust, and surface-patterned silk films were evaluated for the effect of surface morphology on human corneal fibroblast (hCF) cell proliferation, orientation, and ECM deposition and alignment. A series of dimensionally different surface groove patterns were prepared from optically graded glass substrates followed by casting poly(dimethylsiloxane) (PDMS) replica molds. The features on the patterned silk films showed an array of asymmetric triangles and displayed 37-342 nm depths and 445-3 582 nm widths. hCF DNA content on all patterned films were not significantly different from that on flat silk films after 4 d in culture. However, the depth and width of the grooves influenced cell alignment, while the depth differences affected cell orientation; overall, deeper and narrower grooves induced more hCF orientation. Over 14 d in culture, cell layers and actin filament organization demonstrated that confluent hCFs and their cytoskeletal filaments were oriented along the direction of the silk film patterned groove axis. Collagen type V and proteoglycans (decorin and biglycan), important markers of corneal stromal tissue, were highly expressed with alignment. Understanding corneal stromal fibroblast responses to surface features on a protein-based biomaterial applicable in vivo for corneal repair potential suggests options to improve corneal tissue mimics. Further, the approaches provide fundamental biomaterial designs useful for bioengineering oriented tissue layers, an endemic feature in most biological tissue structures that lead to critical tissue functions.

Application of Collagen Scaffold in Tissue Engineering: Recent Advances and New Perspectives

Directory of Open Access Journals (Sweden)

Chanjuan Dong

2016-02-01

Full Text Available Collagen is the main structural protein of most hard and soft tissues in animals and the human body, which plays an important role in maintaining the biological and structural integrity of the extracellular matrix (ECM and provides physical support to tissues. Collagen can be extracted and purified from a variety of sources and offers low immunogenicity, a porous structure, good permeability, biocompatibility and biodegradability. Collagen scaffolds have been widely used in tissue engineering due to these excellent properties. However, the poor mechanical property of collagen scaffolds limits their applications to some extent. To overcome this shortcoming, collagen scaffolds can be cross-linked by chemical or physical methods or modified with natural/synthetic polymers or inorganic materials. Biochemical factors can also be introduced to the scaffold to further improve its biological activity. This review will summarize the structure and biological characteristics of collagen and introduce the preparation methods and modification strategies of collagen scaffolds. The typical application of a collagen scaffold in tissue engineering (including nerve, bone, cartilage, tendon, ligament, blood vessel and skin will be further provided. The prospects and challenges about their future research and application will also be pointed out.

Halogens are key cofactors in building of collagen IV scaffolds outside the cell.

Science.gov (United States)

Brown, Kyle L; Hudson, Billy G; Voziyan, Paul A

2018-05-01

The purpose of this review is to highlight recent advances in understanding the molecular assembly of basement membranes, as exemplified by the glomerular basement membrane (GBM) of the kidney filtration apparatus. In particular, an essential role of halogens in the basement membrane formation has been discovered. Extracellular chloride triggers a molecular switch within non collagenous domains of collagen IV that induces protomer oligomerization and scaffold assembly outside the cell. Moreover, bromide is an essential cofactor in enzymatic cross-linking that reinforces the stability of scaffolds. Halogenation and halogen-induced oxidation of the collagen IV scaffold in disease states damage scaffold function. Halogens play an essential role in the formation of collagen IV scaffolds of basement membranes. Pathogenic damage of these scaffolds by halogenation and halogen-induced oxidation is a potential target for therapeutic interventions.

Effect of Cycloplegia on Corneal Biometrics and Refractive State.

Science.gov (United States)

Bagheri, Abbas; Feizi, Mohadeseh; Shafii, Aliakbar; Faramarzi, Amir; Tavakoli, Mehdi; Yazdani, Shahin

2018-01-01

To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system. In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia. Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia ( P biometrics should be considered before cataract and refractive surgeries.

Force Spectroscopy of Collagen Fibers to Investigate Their Mechanical Properties and Structural Organization

OpenAIRE

Gutsmann, Thomas; Fantner, Georg E.; Kindt, Johannes H.; Venturoni, Manuela; Danielsen, Signe; Hansma, Paul K.

2004-01-01

Tendons are composed of collagen and other molecules in a highly organized hierarchical assembly, leading to extraordinary mechanical properties. To probe the cross-links on the lower level of organization, we used a cantilever to pull substructures out of the assembly. Advanced force probe technology, using small cantilevers (length

Preparation and properties of silk sericin/cellulose cross-linking films

Directory of Open Access Journals (Sweden)

Wang Kunyan

2017-01-01

Full Text Available Silk sericin/cellulose cross-linked films were successfully prepared using glutaraldehyde as cross-linkinger. FTIR was applied to characterize the chemical structure of films. Cross-linked silk sericin film was found the peak intensity of FTIR for cross-linked film decreased markedly compared to pure silk sericin, which indicating cross-linking reaction has been occurred. The increasing value of swelling ratio also indicated the cross-linking has been happened. The cross-linking reaction increased the thermal decomposition temperature.

Cross-linked structure of network evolution

International Nuclear Information System (INIS)

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

2014-01-01

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

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.

Ultra B2 - Promoção de ligações covalentes do colágeno corneal (Corneal cross-linking) no tratamento de ceratocone: resultados preliminares

OpenAIRE

Jankov, Mirko R; Hafezi, Farhad; Beko, Maja; Ignjatovic, Zora; Djurovic, Branislav; Markovic, Vujica; Schor, Paulo

2008-01-01

OBJETIVO: Apresentar os resultados visuais e ceratométricos, seis meses após tratamento foto-terapêutico com luz ultravioleta (UV) e vitamina B2 (Ultra B2), em pacientes com ceratocone progressivo. MÉTODOS: Vinte e cinco olhos de 20 pacientes (15 homens e 5 mulheres) com ceratocone progressivo, determinado pelo aumento de curvatura em exames seriados de topografia corneal, nos últimos seis meses foram avaliados. Acuidade visual não corrigida (UVA), acuidade visual melhor corrigida com óculos ...

Shaped articles of cross-linked fluorocarbon polymers

International Nuclear Information System (INIS)

Gotcher, A.J.; Germeraad, P.B.

1981-01-01

A process is described which comprises (1) contacting (a) a shaped article of a polymeric composition wherein the polymer is a fluorocarbon polymer having a melting point of at least 200 0 C, the article having a tensile strength of at least 3,000 psi, with (b) a fluid composition comprising a cross-linking agent, until the article contains at least 2.5% by weight of the cross-linking agent; and (2) irradiating the shaped article with ionising radiation to a dosage not exceeding 50 Mrads under conditions such that the composition is cross-linked sufficiently to impart thereto an M 100 value of at least 300 psi, while maintaining a tensile strength of at least 3000 psi, the shaped article containing a specified proportion of the cross-linking agent. (author)

Cell therapy of congenital corneal diseases with umbilical mesenchymal stem cells: lumican null mice.

Directory of Open Access Journals (Sweden)

Hongshan Liu

Full Text Available BACKGROUND: Keratoplasty is the most effective treatment for corneal blindness, but suboptimal medical conditions and lack of qualified medical personnel and donated cornea often prevent the performance of corneal transplantation in developing countries. Our study aims to develop alternative treatment regimens for congenital corneal diseases of genetic mutation. METHODOLOGY/PRINCIPAL FINDINGS: Human mesenchymal stem cells isolated from neonatal umbilical cords were transplanted to treat thin and cloudy corneas of lumican null mice. Transplantation of umbilical mesenchymal stem cells significantly improved corneal transparency and increased stromal thickness of lumican null mice, but human umbilical hematopoietic stem cells failed to do the same. Further studies revealed that collagen lamellae were re-organized in corneal stroma of lumican null mice after mesenchymal stem cell transplantation. Transplanted umbilical mesenchymal stem cells survived in the mouse corneal stroma for more than 3 months with little or no graft rejection. In addition, these cells assumed a keratocyte phenotype, e.g., dendritic morphology, quiescence, expression of keratocyte unique keratan sulfated keratocan and lumican, and CD34. Moreover, umbilical mesenchymal stem cell transplantation improved host keratocyte functions, which was verified by enhanced expression of keratocan and aldehyde dehydrogenase class 3A1 in lumican null mice. CONCLUSIONS/SIGNIFICANCE: Umbilical mesenchymal stem cell transplantation is a promising treatment for congenital corneal diseases involving keratocyte dysfunction. Unlike donated corneas, umbilical mesenchymal stem cells are easily isolated, expanded, stored, and can be quickly recovered from liquid nitrogen when a patient is in urgent need.

Anatomical characterization of central, apical and minimal corneal thickness

Directory of Open Access Journals (Sweden)

Federico Saenz-Frances

2014-08-01

Full Text Available AIM: To anatomically locate the points of minimum corneal thickness and central corneal thickness (pupil center in relation to the corneal apex.METHODS: Observational, cross-sectional study, 299 healthy volunteers. Thickness at the corneal apex (AT, minimum corneal thickness (MT and corneal thickness at the pupil center (PT were determined using the pentacam. Distances from the corneal apex to MT (MD and PT (PD were calculated and their quadrant position (taking the corneal apex as the reference determined:point of minimum thickness (MC and point of central thickness (PC depending on the quadrant position. Two multivariate linear regression models were constructed to examine the influence of age, gender, power of the flattest and steepest corneal axes, position of the flattest axis, corneal volume (determined using the Pentacam and PT on MD and PD. The effects of these variables on MC and PC were also determined in two multinomial regression models.RESULTS: MT was located at a mean distance of 0.909 mm from the apex (79.4% in the inferior-temporal quadrant. PT was located at a mean distance of 0.156 mm from the apex. The linear regression model for MD indicated it was significantly influenced by corneal volume (B=-0.024; 95%CI:-0.043 to -0.004. No significant relations were identified in the linear regression model for PD or the multinomial logistic regressions for MC and PC.CONCLUSION: MT was typically located at the inferior-temporal quadrant of the cornea and its distance to the corneal apex tended to decrease with the increment of corneal volume.

Measurement of cross-linked elastin synthesis in bleomycin-induced pulmonary fibrosis using a highly sensitive assay for desmosine and isodesmosine

International Nuclear Information System (INIS)

Cantor, J.O.; Osman, M.; Keller, S.; Cerreta, J.M.; Mandl, I.; Turino, G.M.

1984-01-01

Cross-linked elastin synthesis was measured in the intratracheal bleomycin model of interstitial pulmonary fibrosis by incorporation of 14C-lysine into the elastin-specific crosslinks, desmosine and isodesmosine. Detection of the labeled crosslinks was facilitated by development of a highly sensitive assay utilizing thin-layer electrophoresis. The results indicate that crosslinked elastin synthesis is significantly elevated from controls (p less than 0.05) at 1 to 3 weeks after exposure to bleomycin and returns to normal by 5 weeks. The increases in labeled elastin synthesis are not directly related to changes in either total lung protein synthesis or the pool size of the 14C-lysine. In comparison with collagen and glycosaminoglycan synthesis in this model of lung injury, maximal increases in cross-linked elastin formation occur later, but overlap with the elevated synthesis of these other connective tissue components. The marked increase from normal in cross-linked elastin synthesis in this model suggests that this tissue component is an important part of the fibrotic response of the pulmonary parenchyma and may play a role in the observed alterations in lung structure and function

Corneal Laceration

Medline Plus

Full Text Available ... Eye Health A-Z Symptoms Glasses & Contacts Tips & Prevention News Ask an Ophthalmologist Patient Stories Español Eye ... Causes Corneal Laceration? Corneal Laceration Diagnosis Corneal Laceration Treatment What Is Corneal Laceration? Leer en Español: ¿Qué ...

Biocatalytic cross-linking of pectic polysaccharides for designed food functionality

DEFF Research Database (Denmark)

Zaidel, Dayang Norulfairuz Abang; Meyer, Anne S.

2012-01-01

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......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...... specific enzymatic reactions, and highlights the most recent data concerning enzyme catalyzed engineering of cross-links for in situ structural design of functional properties of foods....

Multiphoton tomography of the human eye

Science.gov (United States)

König, Karsten; Batista, Ana; Hager, Tobias; Seitz, Berthold

2017-02-01

Multiphoton tomography (MPT) is a novel label-free clinical imaging method for non-invasive tissue imaging with high spatial (300 nm) and temporal (100 ps) resolutions. In vivo optical histology can be realized due to the nonlinear excitation of endogenous fluorophores and second-harmonic generation (SHG) of collagen. Furthermore, optical metabolic imaging (OMI) is performed by two-photon autofluorescence lifetime imaging (FLIM). So far, applications of the multiphoton tomographs DermaInspect and MPTflex were limited to dermatology. Novel applications include intraoperative brain tumor imaging as well as cornea imaging. In this work we describe two-photon imaging of ex vivo human corneas unsuitable for transplantation. Furthermore, the cross-linking (CXL) process of corneal collagen based on UVA exposure and 0.1 % riboflavin was studied. The pharmacokinetics of the photosensitizer could be detected with high spatial resolution. Interestingly, an increase in the stromal autofluorescence intensity and modifications of the autofluorescence lifetimes were observed in the human corneal samples within a few days following CXL.

N-Isopropylacrylamide-co-glycidylmethacrylate as a Thermoresponsive Substrate for Corneal Endothelial Cell Sheet Engineering

Directory of Open Access Journals (Sweden)

Bernadette K. Madathil

2014-01-01

Full Text Available Endothelial keratoplasty is a recent shift in the surgical treatment of corneal endothelial dystrophies, where the dysfunctional endothelium is replaced whilst retaining the unaffected corneal layers. To overcome the limitation of donor corneal shortage, alternative use of tissue engineered constructs is being researched. Tissue constructs with intact extracellular matrix are generated using stimuli responsive polymers. In this study we evaluated the feasibility of using the thermoresponsive poly(N-isopropylacrylamide-co-glycidylmethacrylate polymer as a culture surface to harvest viable corneal endothelial cell sheets. Incubation below the lower critical solution temperature of the polymer allowed the detachment of the intact endothelial cell sheet. Phase contrast and scanning electron microscopy revealed the intact architecture, cobble stone morphology, and cell-to-cell contact in the retrieved cell sheet. Strong extracellular matrix deposition was also observed. The RT-PCR analysis confirmed functionally active endothelial cells in the cell sheet as evidenced by the positive expression of aquaporin 1, collagen IV, Na+-K+ ATPase, and FLK-1. Na+-K+ ATPase protein expression was also visualized by immunofluorescence staining. These results suggest that the in-house developed thermoresponsive culture dish is a suitable substrate for the generation of intact corneal endothelial cell sheet towards transplantation for endothelial keratoplasty.

Spontaneous Corneal Hydrops in a Patient with a Corneal Ulcer

Directory of Open Access Journals (Sweden)

Hatim Batawi

2016-01-01

Full Text Available Purpose: We report the case of a 77-year-old man with no history of keratoconus or other ectatic disorders who presented with corneal hydrops in the setting of a corneal ulcer. The risk factors, pathogenesis and treatment options of corneal hydrops are discussed. Method: This is an observational case report study. Results: A 77-year-old man presented with a 1-day history of severe pain, redness, mucous discharge and photophobia in the right eye. A slit-lamp examination of the right eye showed an area of focal corneal edema and protrusion. Within the area of edema and protrusion, there was an infiltrate with an overlying epithelial defect consistent with an infectious corneal ulcer. The Seidel test showed no leakage, so a clinical diagnosis of corneal hydrops associated with nonperforated corneal ulcer was made. With appropriate antibiotic treatment, the corneal ulcer and hydrops both resolved over a 1-month period. Conclusion: Corneal hydrops can occur in the setting of corneal infections.

Corneal changes with accommodation using dual Scheimpflug photography.

Science.gov (United States)

Sisó-Fuertes, Irene; Domínguez-Vicent, Alberto; del Águila-Carrasco, Antonio; Ferrer-Blasco, Teresa; Montés-Micó, Robert

2015-05-01

To assess whether corneal parameters and aberrations are affected by accommodation. Optics Department, University of Valencia, Valencia, Spain. Prospective cross-sectional study. The Galilei G4 dual Scheimpflug device was used to obtain data on the anterior and posterior axial curvatures, total corneal power (TCP), and corneal pachymetry from 3 corneal zones (central: 0.0 up to 4.0 mm; paracentral or mid: 4.0 up to 7.0 mm; peripheral: 7.0 up to 10.0 mm) in young emmetropic eyes in the unaccommodated and 4 accommodated states (from -1.0 to -4.0 diopters [D] in 1.0 D steps). The 2nd-, 3rd-, and 4th-order aberrations as well as the root mean square (RMS) were also determined for the entire cornea at the same accommodative demands. The study evaluated 7 subjects (12 eyes). No significant changes in any measured parameter were found during accommodation for any corneal zone (P > .05). Statistically significant differences were found in the various corneal zones when it was assumed they were constant with accommodation (P the high standard deviation values. Different parameters in various zones of the cornea as well as corneal aberrations were stable during accommodation. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

Embryonic chicken cornea and cartilage synthesize type IX collagen molecules with different amino-terminal domains.

OpenAIRE

Svoboda, K K; Nishimura, I; Sugrue, S P; Ninomiya, Y; Olsen, B R

1988-01-01

We have analyzed embryonic chicken cornea for the presence of type IX collagen mRNA and protein. Using RNA transfer blot analysis, we demonstrate that alpha 1(IX) and alpha 2(IX) mRNAs are expressed by corneal epithelial cells at the time that the primary stromal components are synthesized. The levels of the mRNAs decrease with increasing developmental age and are barely detectable at day 11 of development. In contrast, type IX collagen protein is detectable by immunofluorescence at days 5 an...

Controlled release of an extract of Calendula officinalis flowers from a system based on the incorporation of gelatin-collagen microparticles into collagen I scaffolds: design and in vitro performance.

Science.gov (United States)

Jiménez, Ronald A; Millán, Diana; Suesca, Edward; Sosnik, Alejandro; Fontanilla, Marta R

2015-06-01

Aiming to develop biological skin dresses with improved performance in the treatment of skin wounds, acellular collagen I scaffolds were modified with polymeric microparticles and the subsequent loading of a hydroglycolic extract of Calendula officinalis flowers. Microparticles made of gelatin-collagen were produced by a water-in-oil emulsion/cross-linking method. Thereafter, these microparticles were mixed with collagen suspensions at three increasing concentrations and the resulting mixtures lyophilized to make microparticle-loaded porous collagen scaffolds. Resistance to enzymatic degradation, ability to associate with the C. officinalis extract, and the extract release profile of the three gelatin-collagen microparticle-scaffold prototypes were assessed in vitro and compared to collagen scaffolds without microparticles used as control. Data indicated that the incorporation of gelatin-collagen microparticles increased the resistance of the scaffolds to in vitro enzymatic degradation, as well as their association with the C. officinalis flower extract. In addition, a sharp decrease in cytotoxicity, as well as more prolonged release of the extract, was attained. Overall results support the potential of these systems to develop innovative dermal substitutes with improved features. Furthermore, the gelatin-collagen mixture represents a low-cost and scalable alternative with high clinical transferability, especially appealing in developing countries.

Corneal Laceration

Medline Plus

Full Text Available ... Ophthalmology/Strabismus Ocular Pathology/Oncology Oculoplastics/Orbit Refractive ... Corneal Laceration Sections What Is Corneal Laceration? Corneal Laceration Symptoms What Causes ...

Evaluation of changes in skin biophysical parameters and appearance after pneumatic injections of non-cross-linked hyaluronic acid in the face.

Science.gov (United States)

Cheng, Hai-Yan; Chen, Yu-Xin; Wang, Mei-Fang; Zhao, Jun-Ying; Li, Lin-Feng

2018-03-15

Pneumatic injections of non-cross-linked hyaluronic acid are effective in skin rejuvenation, however, the associated biophysical parameters and appearance have not been evaluated. To determine the changes in skin biophysical parameters after facial pneumatic injections of non-cross-linked hyaluronic acid. Twenty-eight healthy female volunteers received pneumatic injections of non-cross-linked hyaluronic acid into the face for consecutive 5 weeks. Skin biophysical parameter assessment and clinical evaluation were performed using the CK Multi-Probe Adapter and Visia system. Five of the volunteers also underwent retroauricular skin biopsy before and after the last treatment. The skin tissues were all stained with Masson-trichrome, Verhoeff-van Gieson stain, and hematoxylin-eosin to evaluate the changes in collagen, elastic fibers, and the epidermis, before and after the last treatment. Transepidermal water loss was significantly lower in week 4 (18.46 ± 4.70 g/h/m 2 ) than at the baseline (22.03 ± 7.15 g/h/m 2 , p pores also improved significantly at week 4 (934.07 ± 458.78) compared to the baseline (1024.57 ± 415.31, p pores, and wrinkles.

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.

Optimization of protein cross-linking in bicomponent electrospun scaffolds for therapeutic use

International Nuclear Information System (INIS)

Papa, Antonio; Guarino, Vincenzo; Cirillo, Valentina; Oliviero, Olimpia; Ambrosio, Luigi

2015-01-01

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

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.

Association of altered collagen content and lysyl oxidase expression in degenerative mitral valve disease.

Science.gov (United States)

Purushothaman, K-Raman; Purushothaman, Meerarani; Turnbull, Irene C; Adams, David H; Anyanwu, Anelechi; Krishnan, Prakash; Kini, Annapoorna; Sharma, Samin K; O'Connor, William N; Moreno, Pedro R

Collagen cross-linking is mediated by lysyl oxidase (LOX) enzyme in the extracellular matrix (ECM) of mitral valve leaflets. Alterations in collagen content and LOX protein expression in the ECM of degenerative mitral valve may enhance leaflet expansion and disease severity. Twenty posterior degenerative mitral valve leaflets from patients with severe mitral regurgitation were obtained at surgery. Five normal posterior mitral valve leaflets procured during autopsy served as controls. Valvular interstitial cells (VICs) density was quantified by immunohistochemistry, collagen Types I and III by picro-sirius red staining and immunohistochemistry, and proteoglycans by alcian blue staining. Protein expression of LOX and its mediator TGFβ1 were quantified by immunofluorescence and gene expression by PCR. VIC density was increased, structural Type I collagen density was reduced, while reparative Type III collagen and proteoglycan densities were increased (PDegenerative Mitral Valve Disease may be secondary to alterations in LOX protein expression, contributing to disorganization of ECM and disease severity. Copyright © 2017 Elsevier Inc. All rights reserved.

Using corneal topography design personalized cataract surgery programs

Directory of Open Access Journals (Sweden)

Jin-Ou Huang

2014-08-01

Full Text Available AIM:To investigate how to design personalized cataract surgery programs to achieve surgical correction of preoperative corneal astigmatism with surgical astigmatism under the guidance of corneal topography, improve postoperative visual quality and reduce the cost of treatment. METHODS: Totally 202 cases(226 eyescataract patients were divided into randomized treatment group and individualized treatment group. According to the method and location of the incision, randomized treatment group were divided into 8 groups. Surgical astigmatism after different incision were calculated with the use of preoperative and postoperative corneal astigmatism through vector analysis method. Individualized treatment groups were designed personably for surgical method with reference of every surgically induced astigmatism, the surgical method chooses the type of surgical incision based on close link between preoperative corneal astigmatism and surgically induced astigmatism, and the incision was located in the steep meridian. The postoperative corneal astigmatism of individualized treatment group was observed. RESULTS: Postoperative corneal astigmatism of individualized treatment group were lower than that of 3.0mm clear corneal tunnel incision in the randomized treatment group, there were statistically significance difference, while with 3.0mm sclera tunnel incision group there were no statistically significance difference. After 55.8% of patients with the use of individualized surgical plan could undergo the operation of extracapsular cataract extraction with relatively low cost and rigid intraocular lens implantation, the per capita cost of treatment could be reduced. CONCLUSION: Personalized cataract surgery programs are designed to achieve surgical correction of preoperative corneal astigmatism under the use of corneal topography, improve postoperative visual quality and reduce the cost of treatment.

Inelastic behaviour of collagen networks in cell–matrix interactions and mechanosensation

Science.gov (United States)

Mohammadi, Hamid; Arora, Pamma D.; Simmons, Craig A.; Janmey, Paul A.; McCulloch, Christopher A.

2015-01-01

The mechanical properties of extracellular matrix proteins strongly influence cell-induced tension in the matrix, which in turn influences cell function. Despite progress on the impact of elastic behaviour of matrix proteins on cell–matrix interactions, little is known about the influence of inelastic behaviour, especially at the large and slow deformations that characterize cell-induced matrix remodelling. We found that collagen matrices exhibit deformation rate-dependent behaviour, which leads to a transition from pronounced elastic behaviour at fast deformations to substantially inelastic behaviour at slow deformations (1 μm min−1, similar to cell-mediated deformation). With slow deformations, the inelastic behaviour of floating gels was sensitive to collagen concentration, whereas attached gels exhibited similar inelastic behaviour independent of collagen concentration. The presence of an underlying rigid support had a similar effect on cell–matrix interactions: cell-induced deformation and remodelling were similar on 1 or 3 mg ml−1 attached collagen gels while deformations were two- to fourfold smaller in floating gels of high compared with low collagen concentration. In cross-linked collagen matrices, which did not exhibit inelastic behaviour, cells did not respond to the presence of the underlying rigid foundation. These data indicate that at the slow rates of collagen compaction generated by fibroblasts, the inelastic responses of collagen gels, which are influenced by collagen concentration and the presence of an underlying rigid foundation, are important determinants of cell–matrix interactions and mechanosensation. PMID:25392399

Hydrogels Prepared from Cross-Linked Nanofibrillated Cellulose

Science.gov (United States)

Sandeep S. Nair; J.Y. Zhu; Yulin Deng; Arthur J. Ragauskas

2014-01-01

Nanocomposite hydrogels were developed by cross-linking nanofibrillated cellulose with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. The cross-linked hydrogels showed enhanced water absorption and gel content with the addition of nanocellulose. In addition, the thermal stability, mechanical strength, and modulus increased with an increase in the...

Photorefractive keratectomy with corneal collagen cross-linking 1 year after intrastromal corneal ring segment implantation for the treatment of keratoconus

Directory of Open Access Journals (Sweden)

Maha Elfayoumi

2016-01-01

Conclusion PRK with CXL can be used to enhance aided and unaided visual acuity after treatment of keratoconus with Intacs implants, with a stable refractive outcome, and could postpone penetrating or lamellar keratoplasty in patients with the visually disabling disease of moderate keratoconus.

DNA cross-linking by dehydromonocrotaline lacks apparent base sequence preference.

Science.gov (United States)

Rieben, W Kurt; Coulombe, Roger A

2004-12-01

Pyrrolizidine alkaloids (PAs) are ubiquitous plant toxins, many of which, upon oxidation by hepatic mixed-function oxidases, become reactive bifunctional pyrrolic electrophiles that form DNA-DNA and DNA-protein cross-links. The anti-mitotic, toxic, and carcinogenic action of PAs is thought to be caused, at least in part, by these cross-links. We wished to determine whether the activated PA pyrrole dehydromonocrotaline (DHMO) exhibits base sequence preferences when cross-linked to a set of model duplex poly A-T 14-mer oligonucleotides with varying internal and/or end 5'-d(CG), 5'-d(GC), 5'-d(TA), 5'-d(CGCG), or 5'-d(GCGC) sequences. DHMO-DNA cross-links were assessed by electrophoretic mobility shift assay (EMSA) of 32P endlabeled oligonucleotides and by HPLC analysis of cross-linked DNAs enzymatically digested to their constituent deoxynucleosides. The degree of DNA cross-links depended upon the concentration of the pyrrole, but not on the base sequence of the oligonucleotide target. Likewise, HPLC chromatograms of cross-linked and digested DNAs showed no discernible sequence preference for any nucleotide. Added glutathione, tyrosine, cysteine, and aspartic acid, but not phenylalanine, threonine, serine, lysine, or methionine competed with DNA as alternate nucleophiles for cross-linking by DHMO. From these data it appears that DHMO exhibits no strong base preference when forming cross-links with DNA, and that some cellular nucleophiles can inhibit DNA cross-link formation.

Reactive electrospinning and biodegradation of cross-linked methacrylated polycarbonate nanofibers

Energy Technology Data Exchange (ETDEWEB)

Wu Ruizhi; Zhang Jianfeng; Fan Yuwei; Xu Xiaoming [Department of Comprehensive Dentistry and Biomaterials, Louisiana State University Health Sciences Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States); Stoute, Diana; Lallier, Thomas, E-mail: xxu@lsuhsc.edu [Department of Cell Biology and Anatomy, Louisiana State University Health Science Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States)

2011-06-15

The objectives of this study were to fabricate cross-linked biodegradable polycarbonate nanofibers and to investigate their biodegradability by different enzymes. Poly(2,3-dihydroxycarbonate) was synthesized from naturally occurring l-tartaric acid. The hydroxyl groups on the functional polycarbonate were converted to methacrylate groups to enable the polymer to cross-link under UV irradiation. Smooth cross-linked methacrylated polycarbonate nanofibers (300-1800 nm) were fabricated by a reactive electrospinning process with in situ UV radiation from a mixed solution of linear methacrylated polycarbonate (MPC) and poly(ethylene oxide) (PEO) (MPC:PEO = 9:1) in methanol/chloroform (50/50). These cross-linked nanofibers have shown excellent solvent resistance and their solubility decreases with increasing degree of cross-linking. The thermal properties of linear and cross-linked polycarbonate nanofibers were investigated by differential scanning calorimetry and thermogravimetric analysis. The cross-linked polycarbonate nanofibers show no melting point below 200 {sup 0}C and their decomposition temperature increases with increasing cross-linking degree. Their biodegradation products by five different enzymes were analyzed using liquid chromatography-mass spectrometry (LC-MS). The biodegradability of the polycarbonate nanofibers decreases with increasing cross-linking degree. These nanofibers were found to support human fibroblast survival and to promote cell attachment. This study demonstrates that cross-linked biodegradable polycarbonate nanofibers with different chemical properties and biodegradability can be fabricated using the novel reactive electrospinning technology to meet the needs of different biomedical applications.

Manufacture of polyethylene foam by electron beam cross-linking

International Nuclear Information System (INIS)

Tamai, Isamu

1976-01-01

The manufacturing process of polyethylene foam, comparison between electron beam cross-linking process and chemical cross-linking process, the electron beam irradiation technique for continuous sheets, the characteristics and uses of polyethylene foam are reviewed. The pore diameter can be controlled by selecting the dose rate, because there is strong relationship between the pore diameter and the dose rate. As the dose if higher, the foam becomes finer. The electron accelerators having large capacity show the lowest cost as the radiation source, and are applicable industrially. If the production capacity exceeds about 200 tons per month, the costs of electron beam irradiation process may be more advantageous than that of chemical process according to the circumstances. It is difficult to obtain the uniform distribution of absorption dose in the direction of thickness. General characteristics of cross-linked polyethylene foam are listed. The special feature of electron beam process is that the degree of cross-linking can be controlled arbitrarily before foaming. The products obtained by the electron beam cross-linking process have finer foams and smoother surfaces than those obtained by the chemical process, because the separation of the decomposition of foaming agents from that of cross-linking agents in the chemical cross-linking is difficult. (Iwakiri, K.)

Composition of cross-linked 125I-follitropin-receptor complexes

Energy Technology Data Exchange (ETDEWEB)

Shin, J.; Ji, T.H.

1985-10-15

Both of the alpha and beta subunits of intact human follitropin (FSH) were radioiodinated with SVI-sodium iodide and chloramine-T and could be resolved on sodium dodecyl sulfate-polyacrylamide gels. Radioiodinated FSH was affinity-cross-linked with a cleavable (nondisulfide) homobifunctional reagent to its membrane receptor on the porcine granulosa cell surface as well as to a Triton X-100-solubilized form of the receptor. Cross-linked samples revealed three additional bands of slower electrophoretic mobility, corresponding to 65, 83, and 117 kDa, in addition to the hormone bands. The hormone alpha beta dimer band corresponded to 43 kDa. Formation of the three bands requires the SVI-hormone to bind specifically to the receptor with subsequent cross-linking. Binding was prevented by an excess of the native hormone but not by other hormones. A monofunctional analog of the cross-linking reagent failed to produce the three bands. Reagent concentration-dependent cross-linking revealed that their formation was sequential; smaller complexes formed first and then larger ones. When gels of cross-linked complexes were treated to cleave covalent cross-links and then electrophoresed in a second dimension, 18-, 22-, and 34-kDa components were released, in addition to the alpha and beta subunits of the hormone.

Influence of Crosslink Density and Stiffness on Mechanical Properties of Type I Collagen Gel

Directory of Open Access Journals (Sweden)

Shengmao Lin

2015-02-01

Full Text Available The mechanical properties of type I collagen gel vary due to different polymerization parameters. In this work, the role of crosslinks in terms of density and stiffness on the macroscopic behavior of collagen gel were investigated through computational modeling. The collagen fiber network was developed in a representative volume element, which used the inter-fiber spacing to regulate the crosslink density. The obtained tensile behavior of collagen gel was validated against published experimental data. Results suggest that the cross-linked fiber alignment dominated the strain stiffening effect of the collagen gel. In addition, the gel stiffness was enhanced approximately 40 times as the crosslink density doubled. The non-affine deformation was reduced with the increased crosslink density. A positive bilinear correlation between the crosslink density and gel stiffness was obtained. On the other hand, the crosslink stiffness had much less impact on the gel stiffness. This work could enhance our understanding of collagen gel mechanics and shed lights on designing future clinical relevant biomaterials with better control of polymerization parameters.

The insulin-like growth factor axis and collagen turnover in asthmatic children treated with inhaled budesonide

DEFF Research Database (Denmark)

Wolthers, O D; Juul, A; Hansen, M

1995-01-01

Serum concentrations of growth hormone-dependent insulin-like growth factor I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3), the carboxy terminal propeptide of type I procollagen (PICP), the carboxy terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP) and ...... the calculations (p reduced synthesis of type III collagen. A similar trend was observed in ICTP levels when the 400 micrograms period was excluded from the calculations (p = 0.05; z = -1.9). No other statistically significant variations were seen....

UV laser-induced cross-linking in peptides

Science.gov (United States)

Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

2013-01-01

RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

Enzyme-linked immunosorbent serum assay specific for the 7S domain of Collagen Type IV (P4NP 7S)

DEFF Research Database (Denmark)

Leeming, Diana J; Nielsen, Mette J; Dai, Yueqin

2012-01-01

Aim:  The present study describes the ability of a newly developed N-terminal pro-peptides of type IV collagen 7S domain (P4NP 7S) competitive enzyme-linked immunosorbent assay (ELISA) for describing liver fibrosis. The assay applies a monoclonal antibody specific for a PIVNP 7S epitope 100...... were significantly elevated in rat with liver fibrosis as seen by histology (CCL4: 283% elevated in the highest quartile of total hepatic collagen compared with controls, P = 0.001; BDL: 183% elevated at week 4 compared with sham, P type IV collagen...... expression in BDL rats (r = 0.49, P serum assay specific for P4NP 7S was highly related to liver fibrosis...

The effects of different cross-linking conditions on collagen-based nanocomposite scaffolds-an in vitro evaluation using mesenchymal stem cells

Czech Academy of Sciences Publication Activity Database

Suchý, Tomáš; Šupová, Monika; Sauerová, P.; Verdánová, M.; Sucharda, Zbyněk; Rýglová, Šárka; Žaloudková, Margit; Sedláček, R.; Hubálek Kalbáčová, M.

2015-01-01

Roč. 10, DEC (2015), č. článku 065008. ISSN 1748-6041 R&D Projects: GA MZd(CZ) NV15-25813A Institutional support: RVO:67985891 Keywords : cross-linking agents * nano-composite scaffolds * human mesenchymal stem cells * EDC/NHS * genipin Subject RIV: JI - Composite Materials Impact factor: 3.361, year: 2015

Modificaciones en la estructura celular por microscopia confocal en pacientes con queratocono tratados por crosslinking Changes in the cell structure of patients with keratoconus under cross-linking treatment by using confocal microscopy

Directory of Open Access Journals (Sweden)

Madelyn Jareño Ochoa

2012-12-01

Full Text Available Objetivo: describir las modificaciones en la estructura celular corneal después del tratamiento con crosslinking en pacientes con queratocono. Métodos: la muestra estuvo conformada por 30 pacientes (30 ojos con queratocono progresivo a los que se les realizó crosslinking del colágeno corneal y microscopia confocal. Se analizaron como variables las alteraciones en los plexos nerviosos sub-basal y subepitelial, en los nervios estromales, las modificaciones de los queratocitos en estroma anterior y medio, los cambios de las células endoteliales, la profundidad del tratamiento, así como la presencia y evolución del haze y el edema estromal. Resultados: los plexos nerviosos sub-basal y subepitelial estuvieron ausentes durante el primer mes, hubo una recuperación parcial a los 6 meses (73,3 % y total al año. Las fibras nerviosas estromales estuvieron ausentes al mes, a los 6 meses se recuperaron en 96,7 % y de manera total al año. Se encontró alteración de la morfología de los queratocitos del estroma anterior y medio en el primer mes (96,7 %, con inicio de la repoblación celular en 83,3 % a los 3 meses y al año se evidenció una regeneración total. El edema estromal estuvo presente en el primer mes en 83,3 % de los casos, solo en 3,3 % a los 6 meses y al año no hubo ningún paciente. El haze se observó al mes y a los tres meses en el 100 % de los pacientes, predominó al mes en el grado II, a los seis meses con grado I y disminuyó a 60 % sin haze al año. No se encontraron alteraciones en la morfología o densidad de las células endoteliales. Conclusiones: los resultados obtenidos reafirman los criterios de que el crosslinking del colágeno corneal es un método de tratamiento seguro.Objective: to describe the changes of the corneal cellular structure of patients with keratoconus after the cross-linking treatment. Methods: the sample was made up of 30 eyes from 30 patients, who had progressive keratoconus and were treated with

Reinforcement of a porous collagen scaffold with surface-activated PLA fibers.

Science.gov (United States)

Liu, Xi; Huang, Changbin; Feng, Yujie; Liang, Jie; Fan, Yujiang; Gu, Zhongwei; Zhang, Xingdong

2010-01-01

A hybrid porous collagen scaffold mechanically reinforced with surface-activated poly(lactic acid) (PLA) fiber was prepared. PLA fibers, 20 mum in diameter and 1 mm in length, were aminolyzed with hexanediamine to introduce free amino groups on the surfaces. After the amino groups were transferred to aldehyde groups by treatment with glutaraldehyde, different amounts (1.5, 3, 5 and 8 mg) of surface-activated PLA fibers were homogeneously mixed with 2 ml type-I collagen solution (pH 2.8, 0.6 wt%). This mixture solution was then freeze-dried and cross-linked to obtain collagen sponges with surface-activated PLA fiber. Scanning electron microscopy observation indicated that the collagen sponges had a highly interconnected porous structure with an average pore size of 170 mum, irrespective of PLA fiber incorporation. The dispersion of surface-activated PLA fibers was homogeneous in collagen sponge, in contrast to unactivated PLA fibers. The compression modulus test results showed that, compared with unactivated PLA fibers, the surface-activated PLA fibers enhanced the resistance of collagen sponge to compression more significantly. Cytotoxicity assay by MTT test showed no cytotoxicity of these collagen sponges. L929 mouse fibroblast cell-culture studies in vitro revealed that the number of L929 cells attached to the collagen sponge with surface-activated PLA fibers, both 6 h and 24 h after seeding, was higher than that in pure collagen sponge and sponge with unactivated PLA fibers. In addition, a better distribution of cells infiltrated in collagen sponge with surface-activated PLA fibers was observed by histological staining. These results indicated that the collagen sponge reinforced with surface-activated PLA fibers is a promising biocompatible scaffold for tissue engineering.

Safety and efficacy of collagen crosslinking for the treatment of keratoconus.

Science.gov (United States)

Kolli, Sai; Aslanides, Ioannis M

2010-11-01

Keratoconus is a condition that causes corneal ectasia and reduced vision in young adults. A proportion of these patients have progressive disease requiring corneal transplantation. A revolutionary new treatment that is purported to halt progression of keratoconus, known as collagen crosslinking (CXL), has recently been introduced into clinical practice. CXL involves the treatment of the cornea with riboflavin followed by photoactivation with UVA light leading to corneal strengthening. This article reviews the basic science, clinical protocols, safety aspects and clinical results of CXL. The reader will gain a comprehensive understanding of: i) the basic science of CXL; ii) the optimised protocols for clinical use of CXL; iii) the results of all the main clinical trials in the literature; iv) contraindications to treatment and v) full clinical safety profile of CXL. CXL represents a new treatment that uniquely allows the halt of progression of keratoconus, thus preventing visual loss and the need for surgical intervention. Available data suggest that this treatment has high efficacy and is very safe and may represent the future standard treatment for progressive keratoconus.

Quantitative analysis of the synthesis and secretion of type VII collagen in cultured human dermal fibroblasts with a sensitive sandwich enzyme-linked immunoassay.

Science.gov (United States)

Amano, Satoshi; Ogura, Yuki; Akutsu, Nobuko; Nishiyama, Toshio

2007-02-01

Type VII collagen is the major component of anchoring fibrils in the epidermal basement membrane. Its expression has been analyzed by immunostaining or Northern blotting, but rarely at the protein level. In this study, we have quantitatively examined the effects of ascorbic acid and various cytokines/growth factors on the protein synthesis and secretion of type VII collagen by human dermal fibroblasts in culture, using a developed, highly sensitive sandwich enzyme-linked immunoassay with two kinds of specific monoclonal antibodies against the non-collagenous domain-1. Ascorbic acid and its derivative induced a twofold increase in type VII collagen synthesis, and markedly increased the secretion of type VII collagen into the medium when compared with the control culture. This effect was not influenced by the presence of transforming growth factor-beta1 (TGF-beta1). The synthesis of type VII collagen was elevated by TGF-beta1, platelet-derived growth factor, tumor necrosis factor-alpha, and interleukin-1beta, but not by TGF-alpha. Thus, our data indicate that the synthesis and secretion of type VII collagen in human dermal fibroblasts are regulated by ascorbate and the enhancement of type VII collagen gene expression by cytokines/growth factors is accompanied with elevated production of type VII collagen at the protein level.

Collagen Accumulation in Osteosarcoma Cells lacking GLT25D1 Collagen Galactosyltransferase.

Science.gov (United States)

Baumann, Stephan; Hennet, Thierry

2016-08-26

Collagen is post-translationally modified by prolyl and lysyl hydroxylation and subsequently by glycosylation of hydroxylysine. Despite the widespread occurrence of the glycan structure Glc(α1-2)Gal linked to hydroxylysine in animals, the functional significance of collagen glycosylation remains elusive. To address the role of glycosylation in collagen expression, folding, and secretion, we used the CRISPR/Cas9 system to inactivate the collagen galactosyltransferase GLT25D1 and GLT25D2 genes in osteosarcoma cells. Loss of GLT25D1 led to increased expression and intracellular accumulation of collagen type I, whereas loss of GLT25D2 had no effect on collagen secretion. Inactivation of the GLT25D1 gene resulted in a compensatory induction of GLT25D2 expression. Loss of GLT25D1 decreased collagen glycosylation by up to 60% but did not alter collagen folding and thermal stability. Whereas cells harboring individually inactivated GLT25D1 and GLT25D2 genes could be recovered and maintained in culture, cell clones with simultaneously inactive GLT25D1 and GLT25D2 genes could be not grown and studied, suggesting that a complete loss of collagen glycosylation impairs osteosarcoma cell proliferation and viability. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Collagenous sprue cross-sectional imaging: a comparative blinded study.

Science.gov (United States)

Al-Bawardy, Badr; Sheedy, Shannon P; Herberts, Michelle B; Murray, Joseph A; Rubio-Tapia, Alberto; Rajan, Elizabeth; Bruining, David H; Hansel, Stephanie L; Barlow, John M; Fletcher, Joel G; Fidler, Jeff L

2017-02-01

Collagenous sprue (CS) is a rare enteropathy characterized by villous atrophy and a thickened subepithelial collagen band. The aim of this study is to describe the cross-sectional imaging findings of CS. A case-control, retrospective study with cases of all CS patients from January 2000 to 2015 was performed. Inclusion criteria were (1) Histopathologic diagnosis and (2) Imaging with computed tomography abdomen/pelvis (CT A/P), CT enterography (CTE), or magnetic resonance enterography within 6 months of small bowel (SB) biopsy. Control subjects were irritable bowel syndrome (IBS) patients who underwent CTE. Imaging studies were examined by two GI radiologists, blinded to patient data. 108 patients (54 CS; 54 IBS) were included. Mean age was 56.7 ± 16.5 years, and 68% were female (72% in CS group vs. 63% in IBS group; p = 0.3). CS patients were significantly older (67 ± 12 vs. 47 ± 15 year; p reversal (46% vs. 6%; p < 0.001), SB dilation (28% vs. 0%; p < 0.001), SB conformational change (28% vs. 6%; p = 0.002), SB wall thickening (13% vs. 2%; p = 0.03), and ulcerative jejunoileitis (4% vs. 0%; p = 0.01). Radiologists suspected malabsorption in 72% in the CS group and 2% in the IBS group (p < 0.001). Imaging findings suggestive of mucosal malabsorption are commonly demonstrated in CS.

Corneal densitometry and its correlation with age, pachymetry, corneal curvature, and refraction.

Science.gov (United States)

Garzón, Nuria; Poyales, Francisco; Illarramendi, Igor; Mendicute, Javier; Jáñez, Óscar; Caro, Pedro; López, Alfredo; Argüeso, Francisco

2017-12-01

To determine normative corneal densitometry values in relation to age, sex, refractive error, corneal thickness, and keratometry, measured using the Oculus Pentacam system. Three hundred and thirty-eight healthy subjects (185 men; 153 women) with no corneal disease underwent an exhaustive ocular examination. Corneal densitometry was expressed in standardized grayscale units (GSU). The mean corneal densitometry over the total area was 16.46 ± 1.85 GSU. The Pearson correlation coefficient for total densitometry was r = 0.542 (p  0.05). This is the first report of normative corneal densitometry values in relation to keratometry, corneal thickness, and spherical equivalent measured with the latest Oculus Pentacam software. Corneal densitometry increases with age, but corneal keratometry and refractive parameters do not affect light scattering in the human cornea.

Study of the Conformational State of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium chlorides) in Aqueous Solution by Fluorescence Probing

NARCIS (Netherlands)

Wang, Guang-Jia; Engberts, Jan B.F.N.

The aggregation behaviour of novel non-cross-linked and cross-linked poly(alkylmethyldiallylammonium chlorides) in aqueous solutions has been investigated by fluorescence spectroscopy using pyrene as a probe. These copolymers were found to exhibit similar aggregate properties as the corresponding

Radiation cross-linked polymers: Recent developments and new applications

International Nuclear Information System (INIS)

Rouif, Sophie

2005-01-01

The purpose of the present paper is to review the innovative and recent applications of radiation cross-linking of polymers that reinforces their dimensional stability in chemically aggressive and high temperature conditions. Radiation cross-linking can be applied to a great number of plastics: thermoplastics, elastomers and thermoplastic elastomers (TPE). Some of them can cross-link on their own, some others need to be formulated with a cross-linking agent (promoter) or to be modified during their polymerization. Some results of chemical and thermomechanical characterizations of radiation cross-linked plastics based on engineering polymers will be described, and their advantages will be emphasized in relation with their applications in various sectors: pipes and cables, packaging, automotive, electrical engineering and electronics, including connectors, surface mounted devices, integrated circuits, 3D-MID technology, etc. The paper will conclude with a short review of the industrial irradiation facilities (EB facilities and gamma plants) adapted to the treatment of such various products

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

Modified gum arabic cross-linked gelatin scaffold for biomedical applications

International Nuclear Information System (INIS)

Sarika, P.R.; Cinthya, Kuriakose; Jayakrishnan, A.; Anilkumar, P.R.; James, Nirmala Rachel

2014-01-01

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

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.

Proteomics of Fuchs' Endothelial Corneal Dystrophy support that the extracellular matrix of Descemet's membrane is disordered

DEFF Research Database (Denmark)

Poulsen, Ebbe Toftgaard; Dyrlund, Thomas F; Runager, Kasper

2014-01-01

Fuchs' endothelial corneal dystrophy (FECD) is a major corneal disorder affecting the innermost part of the cornea, leading to visual impairment. As the morphological changes in FECD are mainly observed in the extracellular matrix of the Descemet's membrane/endothelial layer we determined...... that the morphological changes observed in FECD is caused in part by an aberrant assembly of the extracellular matrix within the Descemet's membrane/endothelial layer......., respectively, of which 10 were significantly regulated. The results indicated that the level of type VIII collagen was unaltered even though the protein previously has been implicated in familial early onset forms of the disease. Using the second relative quantitation method iTRAQ we identified 22...

Cross-linking of wheat gluten using a water-soluble carbodiimide

NARCIS (Netherlands)

Tropini, V.; Lens, J.P.; Mulder, W.J.; Silvestre, F.

2000-01-01

Wheat gluten was cross-linked using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC). To enhance cross-linking, N-hydroxysuccinimide (NHS) was added to the reaction mixture. The cross-linking efficiency was evaluated by the decrease in the amount of amino groups, the solubility

Comparative Confocal and Histopathological Study of Corneal Changes in Multiple Myeloma.

Science.gov (United States)

Micali, Antonio; Roszkowska, Anna M; Postorino, Elisa I; Rania, Laura; Aragona, Emanuela; Wylegala, Edward; Nowinska, Anna; Ieni, Antonio; Calimeri, Sebastiano; Pisani, Antonina; Aragona, Pasquale; Puzzolo, Domenico

2017-01-01

Corneal opacities rarely occur in multiple myeloma (MM). Our study correlates the findings of in vivo confocal microscopy (IVCM), a useful diagnostic tool, with histopathological features of corneal opacities appearing in a patient with MM. Case report. A 53-year-old man developed corneal opacities in both eyes, more pronounced in the left eye. After IVCM examination, he underwent penetrating keratoplasty in the left eye, and the button was processed for light and electron microscopy and immunohistochemistry. The diagnosis of MM was made, as confirmed by the elevation of IgGk light chains. IVCM demonstrated hyperreflective areas at the epithelial level, hyperreflective keratocytes of dendritic and lamellar morphology in whole stroma, and hyperreflective endothelial cells. Histopathological examination disclosed many vacuoles in the epithelial cell cytoplasm and a homogenous granular material in the Bowman layer. In stroma, keratocytes of different shape and size, with vesicles laden with an abnormal material, were evident. In Descemet membrane, the posterior nonbanded zone had a honeycomb appearance because of the presence of many roundish spaces among wide-spaced collagen fibers. Endothelial cells demonstrated vesicles filled with a material of uneven electron density. Immunohistochemical analysis showed strong positivity for IgGk light chains in keratocytes and among stromal lamellae. This is the first study describing a correspondence between IVCM features and histopathological alterations observed in corneal opacities in MM. The results of this study improve the current understanding of the pictures obtained by IVCM studies.

Photoreactivities and thermal properties of psoralen cross-links

International Nuclear Information System (INIS)

Yeung, A.T.; Jones, B.K.; Chu, C.T.

1988-01-01

The authors have studied the photoreaction of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP), and 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) with a pair of 18-base-long oligonucleotides in which a 14-base region is complementary. Only one 5'TpA site, favored for both monoadduct and cross-link formation with psoralen, is present in this oligonucleotide pair. They have used this model system to demonstrate, for the first time, strand specificity in the photoreaction of psoralen with DNA. They found that the two types of cross-links which form at this site have large differences in thermal stabilities. In addition, the denaturation of each cross-links isomer duplex occurred in at least three stages, which can be visualized as three bands in thermal equilibrium under the conditions of a denaturing polyacrylamide gel. This novel observation suggests that there are several domains differing in thermal stability in a psoralen cross-link

Damage threshold in adult rabbit eyes after scleral cross-linking by riboflavin/blue light application.

Science.gov (United States)

Iseli, Hans Peter; Körber, Nicole; Karl, Anett; Koch, Christian; Schuldt, Carsten; Penk, Anja; Liu, Qing; Huster, Daniel; Käs, Josef; Reichenbach, Andreas; Wiedemann, Peter; Francke, Mike

2015-10-01

Several scleral cross-linking (SXL) methods were suggested to increase the biomechanical stiffness of scleral tissue and therefore, to inhibit axial eye elongation in progressive myopia. In addition to scleral cross-linking and biomechanical effects caused by riboflavin and light irradiation such a treatment might induce tissue damage, dependent on the light intensity used. Therefore, we characterized the damage threshold and mechanical stiffening effect in rabbit eyes after application of riboflavin combined with various blue light intensities. Adult pigmented and albino rabbits were treated with riboflavin (0.5 %) and varying blue light (450 ± 50 nm) dosages from 18 to 780 J/cm(2) (15 to 650 mW/cm(2) for 20 min). Scleral, choroidal and retinal tissue alterations were detected by means of light microscopy, electron microscopy and immunohistochemistry. Biomechanical changes were measured by shear rheology. Blue light dosages of 480 J/cm(2) (400 mW/cm(2)) and beyond induced pathological changes in ocular tissues; the damage threshold was defined by the light intensities which induced cellular degeneration and/or massive collagen structure changes. At such high dosages, we observed alterations of the collagen structure in scleral tissue, as well as pigment aggregation, internal hemorrhages, and collapsed blood vessels. Additionally, photoreceptor degenerations associated with microglia activation and macroglia cell reactivity in the retina were detected. These pathological alterations were locally restricted to the treated areas. Pigmentation of rabbit eyes did not change the damage threshold after a treatment with riboflavin and blue light but seems to influence the vulnerability for blue light irradiations. Increased biomechanical stiffness of scleral tissue could be achieved with blue light intensities below the characterized damage threshold. We conclude that riboflavin and blue light application increased the biomechanical stiffness of scleral tissue at

Cross-linked polyelectrolyte multilayers for marine antifouling applications

NARCIS (Netherlands)

Zhu, X.; Janczewski, D.; Lee, S.S.C.; Teo, S.L-M.; Vancso, Gyula J.

2013-01-01

A polyionic multilayer film was fabricated by layer-by-layer (LbL) sequential deposition followed by cross-linking under mild conditions on a substrate surface to inhibit marine fouling. A novel polyanion, featuring methyl ester groups for an easy cross-linking was used as a generic solution for

Enzymatic digestibility of peptides cross-linked by ionizing radiation

International Nuclear Information System (INIS)

Dizdaroglu, M.; Gajewski, E.; Simic, M.G.

1984-01-01

Digestibility by proteolytic enzymes of peptides cross-linked by ionizing radiation was investigated. Small peptides of alanine and phenylalanine were chosen as model compounds and aminopeptidases and carboxypeptidases were used as proteolytic enzymes. Peptides exposed to γ-radiation in aqueous solution were analysed by high-performance liquid chromatography before and after hydrolysis by aminopeptidase M, leucine aminopeptidase carboxypeptidase A and carboxypeptidase Y. The results obtained clearly demonstrate the different actions of these enzymes on cross-linked aliphatic and aromatic peptides. Peptide bonds of cross-linked dipeptides of alanine were completely resistant to enzymatic hydrolysis whereas the enzymes, except for carboxypeptidase Y, cleaved all peptide bonds of cross-linked peptides of phenylalanine. The actions of the enzymes on these particular compounds are discussed in detail. (author)

In vivo oxidation in remelted highly cross-linked retrievals.

Science.gov (United States)

Currier, B H; Van Citters, D W; Currier, J H; Collier, J P

2010-10-20

Elimination of free radicals to prevent oxidation has played a major role in the development and product differentiation of the latest generation of highly cross-linked ultra-high molecular weight polyethylene bearing materials. In the current study, we (1) examined oxidation in a series of retrieved remelted highly cross-linked ultra-high molecular weight polyethylene bearings from a number of device manufacturers and (2) compared the retrieval results with findings for shelf-stored control specimens. The hypothesis was that radiation-cross-linked remelted ultra-high molecular weight polyethylene would maintain oxidative stability in vivo comparable with the stability during shelf storage and in published laboratory aging tests. Fifty remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners and nineteen remelted highly cross-linked ultra-high molecular weight polyethylene tibial inserts were received after retrieval from twenty-one surgeons from across the U.S. Thirty-two of the retrievals had been in vivo for two years or more. Each was measured for oxidation with use of Fourier transform infrared spectroscopy. A control series of remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners from three manufacturers was analyzed with electron paramagnetic resonance spectroscopy to measure free radical content and with Fourier transform infrared spectroscopy to measure oxidation initially and after eight to nine years of shelf storage in air. The never-implanted, shelf-aged controls had no measurable free-radical content initially or after eight to nine years of shelf storage. The never-implanted controls showed no increase in oxidation during shelf storage. Oxidation measurements showed measurable oxidation in 22% of the retrieved remelted highly cross-linked liners and inserts after an average of two years in vivo. Because never-implanted remelted highly cross-linked ultra-high molecular weight

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

Heating tubes of cross-linked polyethylene

International Nuclear Information System (INIS)

Knoeppler, H.; Hoffmann, M.

1981-01-01

Oxygen permeability of plastic tubes for floor heating systems was measured as a function of the reduced oxygen content of water in plastic tubes at a flow rate of 0.5 m/s and a temperature of 30 0 C and as a function of oxygen uptake of low-oxygen water in floor heating tubes. Pipes of VEP, periodically cross-linked polyethylene (Engels process), polypropylene copolymeride, and polybutene were compared. The permeability of periodically cross-linked polyethylene is twice as high as that of VEP. Measurements, results, and consequences for floor heating systems are discussed. (KH) [de

Synthesis and Catalytic Properties of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium bromides) Having Decyl, Octyl, and Hexyl Side Chains

NARCIS (Netherlands)

Wang, G.J; Engberts, J.B.F.N.

1995-01-01

A family of non-cross-linked and cross-linked copolymers containing decyl, octyl, and hexyl groups as side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) were synthesized by radical-initiated cyclocopolymerization of alkylmethyldiallylammonium bromide monomers without and

Investigation of the influence of UV irradiation on collagen thin films by AFM imaging

Energy Technology Data Exchange (ETDEWEB)

Stylianou, Andreas, E-mail: styliand@mail.ntua.gr; Yova, Dido; Alexandratou, Eleni

2014-12-01

Collagen is the major fibrous extracellular matrix protein and due to its unique properties, it has been widely used as biomaterial, scaffold and cell-substrate. The aim of the paper was to use Atomic Force Microscopy (AFM) in order to investigate well-characterized collagen thin films after ultraviolet light (UV) irradiation. The films were also used as in vitro culturing substrates in order to investigate the UV-induced alterations to fibroblasts. A special attention was given in the alteration on collagen D-periodicity. For short irradiation times, spectroscopy (fluorescence/absorption) studies demonstrated that photodegradation took place and AFM imaging showed alterations in surface roughness. Also, it was highlighted that UV-irradiation had different effects when it was applied on collagen solution than on films. Concerning fibroblast culturing, it was shown that fibroblast behavior was affected after UV irradiation of both collagen solution and films. Furthermore, after a long irradiation time, collagen fibrils were deformed revealing that collagen fibrils are consisting of multiple shells and D-periodicity occurred on both outer and inner shells. The clarification of the effects of UV light on collagen and the induced modifications of cell behavior on UV-irradiated collagen-based surfaces will contribute to the better understanding of cell–matrix interactions in the nanoscale and will assist in the appropriate use of UV light for sterilizing and photo-cross-linking applications. - Highlights: • Collagen thin films were formed and exposed in UV irradiation. • Collagen thin films were formed from UV-irradiated collagen solution. • Nanocharacterization of collagen thin films by AFM • Fluorescence and absorption spectroscopy studies on collagen films • Investigation of fibroblast response on collagen films.

Investigation of the influence of UV irradiation on collagen thin films by AFM imaging

International Nuclear Information System (INIS)

Stylianou, Andreas; Yova, Dido; Alexandratou, Eleni

2014-01-01

Collagen is the major fibrous extracellular matrix protein and due to its unique properties, it has been widely used as biomaterial, scaffold and cell-substrate. The aim of the paper was to use Atomic Force Microscopy (AFM) in order to investigate well-characterized collagen thin films after ultraviolet light (UV) irradiation. The films were also used as in vitro culturing substrates in order to investigate the UV-induced alterations to fibroblasts. A special attention was given in the alteration on collagen D-periodicity. For short irradiation times, spectroscopy (fluorescence/absorption) studies demonstrated that photodegradation took place and AFM imaging showed alterations in surface roughness. Also, it was highlighted that UV-irradiation had different effects when it was applied on collagen solution than on films. Concerning fibroblast culturing, it was shown that fibroblast behavior was affected after UV irradiation of both collagen solution and films. Furthermore, after a long irradiation time, collagen fibrils were deformed revealing that collagen fibrils are consisting of multiple shells and D-periodicity occurred on both outer and inner shells. The clarification of the effects of UV light on collagen and the induced modifications of cell behavior on UV-irradiated collagen-based surfaces will contribute to the better understanding of cell–matrix interactions in the nanoscale and will assist in the appropriate use of UV light for sterilizing and photo-cross-linking applications. - Highlights: • Collagen thin films were formed and exposed in UV irradiation. • Collagen thin films were formed from UV-irradiated collagen solution. • Nanocharacterization of collagen thin films by AFM • Fluorescence and absorption spectroscopy studies on collagen films • Investigation of fibroblast response on collagen films

Intraocular pressure, corneal thickness, and corneal hysteresis in Steinert's myotonic dystrophy

Directory of Open Access Journals (Sweden)

Carlos Alexandre de A. Garcia Filho

2011-06-01

Full Text Available PURPOSE: Low intraocular pressure (IOP measured by Goldmann applanation tonometry (GAT is one of the ocular manifestations of Steinert's myotonic dystrophy. The goal of this study was to evaluate the corneal-compensated IOP as well as corneal properties (central corneal thickness and corneal hysteresis in patients with myotonic dystrophy. METHODS: A total of 12 eyes of 6 patients with Steinert's myotonic dystrophy (dystrophy group and 12 eyes of 6 age-, race-, and gender-matched healthy volunteers (control group were included in the study. GAT, Dynamic Contour Tonometry (DCT-Pascal and Ocular Response Analyzer (ORA were used to assess the IOP. Central corneal thickness was obtained by ultrasound pachymetry, and corneal hysteresis was analyzed using the ORA device. In light of the multiplicity of tests performed, the significance level was set at 0.01 rather than 0.05. RESULTS: The mean (standard deviation [SD] GAT, DCT, and corneal-compensated ORA IOP in the dystrophy group were 5.4 (1.4 mmHg, 9.7 (1.5 mmHg, and 10.1 (2.6 mmHg, respectively. The mean (SD GAT, DCT, and corneal-compensated ORA IOP in the control group was 12.6 (2.9 mmHg, 15.5 (2.7 mmHg, and 15.8 (3.4 mmHg, respectively. There were significant differences in IOP values between dystrophy and control groups obtained by GAT (mean, -7.2 mmHg; 99% confidence interval [CI], -10.5 to -3.9 mmHg; P<0.001, DCT (mean, -5.9 mmHg; 99% CI, -8.9 to -2.8 mmHg; P<0.001, and corneal-compensated ORA measurements (mean, -5.7 mmHg; 99% CI, -10.4 to -1.0 mmHg; P=0.003. The mean (SD central corneal thickness was similar in the dystrophy (542 [31] µm and control (537 [11] µm groups (P=0.65. The mean (SD corneal hysteresis in the dystrophy and control groups were 11.2 (1.5 mmHg and 9.7 (1.2 mmHg, respectively (P=0.04. CONCLUSIONS: Patients with Steinert's myotonic dystrophy showed lower Goldmann and corneal-compensated IOP in comparison with healthy individuals. Since central corneal thickness and

Keratoconus: current perspectives

Directory of Open Access Journals (Sweden)

Vazirani J

2013-10-01

Full Text Available Jayesh Vazirani, Sayan BasuCornea and Anterior Segment Services, LV Prasad Eye Institute, Hyderabad, IndiaAbstract: Keratoconus is characterized by progressive corneal protrusion and thinning, leading to irregular astigmatism and impairment in visual function. The etiology and pathogenesis of the condition are not fully understood. However, significant strides have been made in early clinical detection of the disease, as well as towards providing optimal optical and surgical correction for improving the quality of vision in affected patients. The past two decades, in particular, have seen exciting new developments promising to alter the natural history of keratoconus in a favorable way for the first time. This comprehensive review focuses on analyzing the role of advanced imaging techniques in the diagnosis and treatment of keratoconus and evaluating the evidence supporting or refuting the efficacy of therapeutic advances for keratoconus, such as newer contact lens designs, collagen crosslinking, deep anterior lamellar keratoplasty, intracorneal ring segments, photorefractive keratectomy, and phakic intraocular lenses.Keywords: keratoconus, corneal topography, hydrops, collagen cross-linking, keratoplasty, contact lenses

Fabrication of chemically cross-linked porous gelatin matrices.

Science.gov (United States)

Bozzini, Sabrina; Petrini, Paola; Altomare, Lina; Tanzi, Maria Cristina

2009-01-01

The aim of this study was to chemically cross-link gelatin, by reacting its free amino groups with an aliphatic diisocyanate. To produce hydrogels with controllable properties, the number of reacting amino groups was carefully determined. Porosity was introduced into the gelatin-based hydrogels through the lyophilization process. Porous and non-porous matrices were characterized with respect to their chemical structure, morphology, water uptake and mechanical properties. The physical, chemical and mechanical properties of the porous matrices are related to the extent of their cross-linking, showing that they can be controlled by varying the reaction parameters. Water uptake values (24 hours) vary between 160% and 200% as the degree of cross-linking increases. The flexibility of the samples also decreases by changing the extent of cross-linking. Young's modulus shows values between 0.188 KPa, for the highest degree, and 0.142 KPa for the lowest degree. The matrices are potential candidates for use as tissue-engineering scaffolds by modulating their physical chemical properties according to the specific application.

Practical application of thermoreversibly Cross-linked rubber products

Science.gov (United States)

Polgar, L. M.; Picchioni, F.; de Ruiter, E.; van Duin, M.

2017-07-01

Currently, rubber products cannot simply be reprocessed after their product life, due to the irreversible cross-linking methods traditionally applied. The purpose of this work is to investigate how thermoreversible cross-linking of rubbers via Diels Alder chemistry can be used for the development of recyclable rubber products. Unfortunately, the applicability of the thermoreversible EPM-g-furan/BM system appears to be limited to room temperature applications, because of the rapid deterioration of the compression set at elevated temperatures compared to irreversibly cross-linked EPM. However, the use of EPM rubber modified with thiophene or cyclopentadiene moieties may extend the temperature application range and results in rubber products with acceptable properties. Finally, rubber products generally comprise fillers such as silica, carbon black or fibers. In this context, the reinforcing effect of short cut aramid fibers on the material properties of the newly developed thermoreversibly cross-linked EPM rubbers was also studied. The material properties of the resulting products were found to be comparable to those of a fiber reinforced, peroxide cured reference sample.

On the Reproducibility of Label-Free Quantitative Cross-Linking/Mass Spectrometry

Science.gov (United States)

Müller, Fränze; Fischer, Lutz; Chen, Zhuo Angel; Auchynnikava, Tania; Rappsilber, Juri

2018-02-01

Quantitative cross-linking/mass spectrometry (QCLMS) is an emerging approach to study conformational changes of proteins and multi-subunit complexes. Distinguishing protein conformations requires reproducibly identifying and quantifying cross-linked peptides. Here we analyzed the variation between multiple cross-linking reactions using bis[sulfosuccinimidyl] suberate (BS3)-cross-linked human serum albumin (HSA) and evaluated how reproducible cross-linked peptides can be identified and quantified by LC-MS analysis. To make QCLMS accessible to a broader research community, we developed a workflow that integrates the established software tools MaxQuant for spectra preprocessing, Xi for cross-linked peptide identification, and finally Skyline for quantification (MS1 filtering). Out of the 221 unique residue pairs identified in our sample, 124 were subsequently quantified across 10 analyses with coefficient of variation (CV) values of 14% (injection replica) and 32% (reaction replica). Thus our results demonstrate that the reproducibility of QCLMS is in line with the reproducibility of general quantitative proteomics and we establish a robust workflow for MS1-based quantitation of cross-linked peptides.

Increased cartilage type II collagen degradation in patients with osteogenesis imperfecta used as a human model of bone type I collagen alterations.

Science.gov (United States)

Rousseau, Jean-Charles; Chevrel, Guillaume; Schott, Anne-Marie; Garnero, Patrick

2010-04-01

We investigated whether cartilage degradation is altered in adult patients with mild osteogenesis imperfecta (OI) used as a human model of bone type I collagen-related osteoarthritis (OA). Sixty-four adult patients with OI (39% women, mean age+/-SD: 37+/-12 years) and 64 healthy age-matched controls (54% women, 39+/-7 years) were included. We also compared data in 87 patients with knee OA (73% women, 63+/-8 years, mean disease duration: 6 years) and 291 age-matched controls (80% women, 62+/-10 years). Urinary C-terminal cross-linked telopeptide of type II collagen (CTX-II), a marker of cartilage degradation, urinary helical peptide of type I collagen (Helix-I), a marker of bone resorption, and the urinary ratio between non-isomerised/isomerised (alpha/beta CTX-I) type I collagen C-telopeptide, a marker of type I collagen maturation, were measured. Patients with OI had CTX-II levels similar to those of subjects with knee OA (p=0.89; mean+/-SEM; 460+/-57 ng/mmol Cr for OI group and 547+/-32 ng/mmol Cr for OA group) and significantly higher than both young (144+/-7.8 ng/mmol Cr, p<0.0001) and old controls (247+/-7 ng/mmol Cr, p<0.0001). In patients with OI, increased Helix-I (p<0.0001) and alpha/beta CTX-I (p=0.0067) were independently associated with increased CTX-II and together explained 26% of its variance (p< 0.0001). In patients with knee OA, increased levels of alpha/beta CTX-I ratio were also associated with higher CTX-II levels. Adult patients with OI or knee OA are characterized by increased cartilage type II collagen degradation, which is associated with increased type I collagen degradation for OI and lower type I collagen maturation for both OI and OA. These data suggest that both quantitative and qualitative alterations of bone type I collagen metabolism are involved in increased cartilage degradation in patients with OI or knee OA. Copyright 2009 Elsevier Inc. All rights reserved.

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.

Initiating fibro-proliferation through interfacial interactions of myoglobin colloids with collagen in solution.

Science.gov (United States)

Dhanasekaran, Madhumitha; Dhathathreyan, Aruna

2017-08-01

This work examines fibro-proliferation through interaction of myoglobin (Mb), a globular protein with collagen, an extracellular matrix fibrous protein. Designed colloids of Mb at pH 4.5 and 7.5 have been mixed with collagen solution at pH 7.5 and 4.5 in different concentrations altering their surface charges. For the Mb colloids, 100-200nm sizes have been measured from Transmission electron micrographs and zeta sizer. CD spectra shows a shift to beta sheet like structure for the protein in the colloids. Interaction at Mb/Collagen interface studied using Dilational rheology, Quartz crystal microbalance with dissipation and Differential Scanning calorimetry show that the perturbation is not only by the charge compensation arising from the difference in pH of the colloids and collagen, but also by the organized assembly of collagen at that particular pH. Results demonstrate that positive Mb colloids at pH 4.5, having more% of entrained water stabilize the collagen fibrils (pH 7.5) around them. Ensuing dehydration leads to effective cross-linking and inherently anisotropic growth of fibrils/fibres of collagen. In the case of Mb colloids at pH 7.5, the fibril formation seems to supersede the clustering of Mb suggesting that the fibro-proliferation is both pH and hydrophilic-hydrophobic balance dependent at the interface. Copyright © 2017 Elsevier B.V. All rights reserved.

UV cross-linking of polypeptides associated with 3'-terminal exons

International Nuclear Information System (INIS)

Stolow, D.T.; Berget, S.M.

1990-01-01

Association of nuclear proteins with chimeric vertebrate precursor RNAs containing both polyadenylation signals and an intron was examined by UV cross-linking. One major difference in cross-linking pattern was observed between this chimeric precursor RNA and precursors containing only polyadenylation or splicing signals. The heterogeneous nuclear ribonucleoprotein (hnRNP) polypeptide C cross-linked strongly to sequences downstream of the A addition site in polyadenylation precursor RNA containing only the polyadenylation signal from the simian virus 40 (SV40) late transcription unit. In contrast, the hnRNP C polypeptide cross-linked to chimeric RNA containing the same SV40 late poly(A) cassette very poorly, at a level less than 5% of that observed with the precursor RNA containing just the poly(A) site. Observation that cross-linking of the hnRNP C polypeptide to elements within the SV40 late poly(A) site was altered by the presence of an upstream intron suggests differences in the way nuclear factors associate with poly(A) sites in the presence and absence of an upstream intron. Cross-linking of C polypeptide to chimeric RNA increased with RNAs mutated for splicing or polyadenylation consensus sequences and under reaction conditions (high magnesium) that inhibited polyadenylation. Furthermore, cross-linking of hnRNP C polypeptide to precursors containing just the SV40 late poly(A) site was eliminated in the presence of competing poly(U); polyadenylation, however, was unaffected. Correlation of loss of activity with high levels of hnRNP C polypeptide cross-linking raises questions about the specificity of the interaction between the hnRNP C polypeptide and polyadenylation precursor RNAs in vitro

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.

Mussel-Inspired Self-Healing Double-Cross-Linked Hydrogels by Controlled Combination of Metal Coordination and Covalent Cross-Linking

DEFF Research Database (Denmark)

Andersen, Amanda; Krogsgaard, Marie; Birkedal, Henrik

2018-01-01

a catechol-based hydrogel design that allows for the degree of oxidative covalent cross-linking to be controlled. Double cross-linked hydrogels with tunable stiffness are constructed by adding the oxidizable catechol analogue, tannic acid, to an oxidation-resistant hydrogel construct held together...... by coordination of the dihydroxy functionality of 1-(2'-carboxyethyl)-2-methyl-3-hydroxy-4-pyridinone to trivalent metal ions. By varying the amount of tannic acid, the hydrogel stiffness can be customized to a given application while retaining the self-healing capabilities of the hydrogel's coordination chemical...

Impact of Facial Conformation on Canine Health: Corneal Ulceration

Science.gov (United States)

Packer, Rowena M. A.; Hendricks, Anke; Burn, Charlotte C.

2015-01-01

Concern has arisen in recent years that selection for extreme facial morphology in the domestic dog may be leading to an increased frequency of eye disorders. Corneal ulcers are a common and painful eye problem in domestic dogs that can lead to scarring and/or perforation of the cornea, potentially causing blindness. Exaggerated juvenile-like craniofacial conformations and wide eyes have been suspected as risk factors for corneal ulceration. This study aimed to quantify the relationship between corneal ulceration risk and conformational factors including relative eyelid aperture width, brachycephalic (short-muzzled) skull shape, the presence of a nasal fold (wrinkle), and exposed eye-white. A 14 month cross-sectional study of dogs entering a large UK based small animal referral hospital for both corneal ulcers and unrelated disorders was carried out. Dogs were classed as affected if they were diagnosed with a corneal ulcer using fluorescein dye while at the hospital (whether referred for this disorder or not), or if a previous diagnosis of corneal ulcer(s) was documented in the dogs’ histories. Of 700 dogs recruited, measured and clinically examined, 31 were affected by corneal ulcers. Most cases were male (71%), small breed dogs (mean± SE weight: 11.4±1.1 kg), with the most commonly diagnosed breed being the Pug. Dogs with nasal folds were nearly five times more likely to be affected by corneal ulcers than those without, and brachycephalic dogs (craniofacial ratio dogs. A 10% increase in relative eyelid aperture width more than tripled the ulcer risk. Exposed eye-white was associated with a nearly three times increased risk. The results demonstrate that artificially selecting for these facial characteristics greatly heightens the risk of corneal ulcers, and such selection should thus be discouraged to improve canine welfare. PMID:25969983

Collagen V expression is crucial in regional development of the supraspinatus tendon.

Science.gov (United States)

Connizzo, Brianne K; Adams, Sheila M; Adams, Thomas H; Birk, David E; Soslowsky, Louis J

2016-12-01

Manipulations in cell culture and mouse models have demonstrated that reduction of collagen V results in altered fibril structure and matrix assembly. A tissue-dependent role for collagen V in determining mechanical function was recently established, but its role in determining regional properties has not been addressed. The objective of this study was to define the role(s) of collagen V expression in establishing the site-specific properties of the supraspinatus tendon. The insertion and midsubstance of tendons from wild type, heterozygous and tendon/ligament-specific null mice were assessed for crimp morphology, fibril morphology, cell morphology, as well as total collagen and pyridinoline cross-link (PYD) content. Fibril morphology was altered at the midsubstance of both groups with larger, but fewer, fibrils and no change in cell morphology or collagen compared to the wild type controls. In contrast, a significant disruption of fibril assembly was observed at the insertion site of the null group with the presence of structurally aberrant fibrils. Alterations were also present in cell density and PYD content. Altogether, these results demonstrate that collagen V plays a crucial role in determining region-specific differences in mouse supraspinatus tendon structure. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2154-2161, 2016. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Interactions of cross-linked and uncross-linked chitosan hydrogels ...

African Journals Online (AJOL)

The swelling equilibrium of Chitosan and sodium tripolyphosphate (NaTPP) cross-linked chitosan hydrogels in aqueous solutions of surfactants differing in structure and hydrophobicity at 250C is reported. Anionic surfactant sodium dodecylsulfate (SDS), the cationic surfactant hexadecyltrimethylammonium bromide (HTAB) ...

Formaldehyde cross-linking and structural proteomics: Bridging the gap.

Science.gov (United States)

Srinivasa, Savita; Ding, Xuan; Kast, Juergen

2015-11-01

Proteins are dynamic entities constantly moving and altering their structures based on their functions and interactions inside and outside the cell. Formaldehyde cross-linking combined with mass spectrometry can accurately capture interactions of these rapidly changing biomolecules while maintaining their physiological surroundings. Even with its numerous established uses in biology and compatibility with mass spectrometry, formaldehyde has not yet been applied in structural proteomics. However, formaldehyde cross-linking is moving toward analyzing tertiary structure, which conventional cross-linkers have already accomplished. The purpose of this review is to describe the potential of formaldehyde cross-linking in structural proteomics by highlighting its applications, characteristics and current status in the field. Copyright © 2015 Elsevier Inc. All rights reserved.

Surface Topography and Mechanical Strain Promote Keratocyte Phenotype and Extracellular Matrix Formation in a Biomimetic 3D Corneal Model.

Science.gov (United States)

Zhang, Wei; Chen, Jialin; Backman, Ludvig J; Malm, Adam D; Danielson, Patrik

2017-03-01

The optimal functionality of the native corneal stroma is mainly dependent on the well-ordered arrangement of extracellular matrix (ECM) and the pressurized structure. In order to develop an in vitro corneal model, it is crucial to mimic the in vivo microenvironment of the cornea. In this study, the influence of surface topography and mechanical strain on keratocyte phenotype and ECM formation within a biomimetic 3D corneal model is studied. By modifying the surface topography of materials, it is found that patterned silk fibroin film with 600 grooves mm -1 optimally supports cell alignment and ECM arrangement. Furthermore, treatment with 3% dome-shaped mechanical strain, which resembles the shape and mechanics of native cornea, significantly enhances the expression of keratocyte markers as compared to flat-shaped strain. Accordingly, a biomimetic 3D corneal model, in the form of a collagen-modified, silk fibroin-patterned construct subjected to 3% dome-shaped strain, is created. Compared to traditional 2D cultures, it supports a significantly higher expression of keratocyte and ECM markers, and in conclusion better maintains keratocyte phenotype, alignment, and fusiform cell shape. Therefore, the novel biomimetic 3D corneal model developed in this study serves as a useful in vitro 3D culture model to improve current 2D cultures for corneal studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Newly identified interfibrillar collagen crosslinking suppresses cell proliferation and remodelling.

Science.gov (United States)

Marelli, Benedetto; Le Nihouannen, Damien; Hacking, S Adam; Tran, Simon; Li, Jingjing; Murshed, Monzur; Doillon, Charles J; Ghezzi, Chiara E; Zhang, Yu Ling; Nazhat, Showan N; Barralet, Jake E

2015-06-01

Copper is becoming recognised as a key cation in a variety of biological processes. Copper chelation has been studied as a potential anti-angiogenic strategy for arresting tumour growth. Conversely the delivery of copper ions and complexes in vivo can elicit a pro-angiogenic effect. Previously we unexpectedly found that copper-stimulated intraperitoneal angiogenesis was accompanied by collagen deposition. Here, in hard tissue, not only was healing accelerated by copper, but again enhanced deposition of collagen was detected at 2 weeks. Experiments with reconstituted collagen showed that addition of copper ions post-fibrillogenesis rendered plastically-compressed gels resistant to collagenases, enhanced their mechanical properties and increased the denaturation temperature of the protein. Unexpectedly, this apparently interfibrillar crosslinking was not affected by addition of glucose or ascorbic acid, which are required for crosslinking by advanced glycation end products (AGEs). Fibroblasts cultured on copper-crosslinked gels did not proliferate, whereas those cultured with an equivalent quantity of copper on either tissue culture plastic or collagen showed no effect compared with controls. Although non-proliferative, fibroblasts grown on copper-cross-linked collagen could migrate, remained metabolically active for at least 14 days and displayed a 6-fold increase in Mmps 1 and 3 mRNA expression compared with copper-free controls. The ability of copper ions to crosslink collagen fibrils during densification and independently of AGEs or Fenton type reactions is previously unreported. The effect on MMP susceptibility of collagen and the dramatic change in cell behaviour on this crosslinked ECM may contribute to shedding some light on unexplained phenomena as the apparent benefit of copper complexation in fibrotic disorders or the enhanced collagen deposition in response to localised copper delivery. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

Cross-linked polymeric membranes for carbon dioxide separation

Science.gov (United States)

Hong, Tao; Chatterjee, Sabornie; Mahurin, Shannon Mark; Long, Brian Keith; Jiang, De-en; Mays, Jimmy Wayne; Sokolov, Alexei P.; Saito, Tomonori

2018-01-23

A membrane useful in gas separation, the membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1.times.10.sup.-5 mol/cm.sup.3 to about 6.times.10.sup.-5 mol/cm.sup.3, where, in particular embodiments, the cross-linked polysiloxane structure has the following general structure: ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms; A.sup.1 and A.sup.2 are independently selected from cyclic hydrocarbon groups; L.sup.1 and L.sup.2 are linking groups or covalent bonds; n is an integer of at least 1; r and s are independently selected from integers of at least 1; and p is an integer of at least 10. The invention also includes methods for making and using the above-described membranes for gas separation.

A General Method for Targeted Quantitative Cross-Linking Mass Spectrometry.

Directory of Open Access Journals (Sweden)

Juan D Chavez

Full Text Available Chemical cross-linking mass spectrometry (XL-MS provides protein structural information by identifying covalently linked proximal amino acid residues on protein surfaces. The information gained by this technique is complementary to other structural biology methods such as x-ray crystallography, NMR and cryo-electron microscopy[1]. The extension of traditional quantitative proteomics methods with chemical cross-linking can provide information on the structural dynamics of protein structures and protein complexes. The identification and quantitation of cross-linked peptides remains challenging for the general community, requiring specialized expertise ultimately limiting more widespread adoption of the technique. We describe a general method for targeted quantitative mass spectrometric analysis of cross-linked peptide pairs. We report the adaptation of the widely used, open source software package Skyline, for the analysis of quantitative XL-MS data as a means for data analysis and sharing of methods. We demonstrate the utility and robustness of the method with a cross-laboratory study and present data that is supported by and validates previously published data on quantified cross-linked peptide pairs. This advance provides an easy to use resource so that any lab with access to a LC-MS system capable of performing targeted quantitative analysis can quickly and accurately measure dynamic changes in protein structure and protein interactions.

Development of new cross-linked polyethylene for atomic energy

International Nuclear Information System (INIS)

Fujimura, Shun-ichi; Ohya, Shingo; Kubo, Masaji; Tsutsumi, Yukihiro; Seguchi, Tadao.

1988-01-01

Cross-linked polyethylene is the material which is used most as the insulating material for electric wires and cables, but for the cables for nuclear power stations and the wiring materials within machinery and equipment, the cross-linked polyethylene which is hard to burn by mixing burning-retarding agent is frequently used as the disaster-preventing countermeasures. As the burning-retarding agent for cross-linked polyethylene, bromine system agent that gives high burning retardation, chlorine system agent that can prevent melting and dripping at the time of burning and so on have been used so as to meet the objective. However by the addition of burning-retarding agents, the electrical and mechanical characteristics of cross-linked polyethylene lower, therefore consideration must be given to the use. In this paper, the results of the examination on the application of condensed acenaphthylene bromide as a new burning-retarding agent to cross-linked polyethylene are reported. White lead was effective for catching HBr. It was confirmed that more than 30 parts of this agent ensured burning retardation. By mixing this agent, the tensile strength increased, but the elongation lowered. It was found that the good radiation resistance was obtained by adding this agent. (K.I.)

Molecular Model for HNBR with Tunable Cross-Link Density.

Science.gov (United States)

Molinari, N; Khawaja, M; Sutton, A P; Mostofi, A A

2016-12-15

We introduce a chemically inspired, all-atom model of hydrogenated nitrile butadiene rubber (HNBR) and assess its performance by computing the mass density and glass-transition temperature as a function of cross-link density in the structure. Our HNBR structures are created by a procedure that mimics the real process used to produce HNBR, that is, saturation of the carbon-carbon double bonds in NBR, either by hydrogenation or by cross-linking. The atomic interactions are described by the all-atom "Optimized Potentials for Liquid Simulations" (OPLS-AA). In this paper, first, we assess the use of OPLS-AA in our models, especially using NBR bulk properties, and second, we evaluate the validity of the proposed model for HNBR by investigating mass density and glass transition as a function of the tunable cross-link density. Experimental densities are reproduced within 3% for both elastomers, and qualitatively correct trends in the glass-transition temperature as a function of monomer composition and cross-link density are obtained.

Fibulin-4 E57K Knock-in Mice Recapitulate Cutaneous, Vascular and Skeletal Defects of Recessive Cutis Laxa 1B with both Elastic Fiber and Collagen Fibril Abnormalities.

Science.gov (United States)

Igoucheva, Olga; Alexeev, Vitali; Halabi, Carmen M; Adams, Sheila M; Stoilov, Ivan; Sasaki, Takako; Arita, Machiko; Donahue, Adele; Mecham, Robert P; Birk, David E; Chu, Mon-Li