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Sample records for gd-conjugated dendrimer nanoclusters

  1. UV luminescence of dendrimer-encapsulated gold nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Hyeong Seop; Kim, Jun Myung; Sohn, So Hyeong; Han, Noh Soo; Park, Seung Min [Dept. of Chemistry, Kyung Hee University, Seoul (Korea, Republic of)

    2016-10-15

    Size-dependent luminescence color is one of the interesting properties of metal nanocrystals, whose sizes are in the dimension of the Fermi wavelength of an electron. Despite the short Fermi wavelength of electrons in gold (-0.7 nm), luminescence of gold nanoclusters has been reported to range from the near-infrared to near-ultraviolet, depending on the number of atoms in the nanoclusters. The photoluminescence of G4-OH (Au) obtained by the excitation of 266 nm showed UV emission in addition to the well-known blue emission. The higher intensity and red-shifted emission of the gold nanoclusters was distinguished from the emission of dendrimers. The UV emission at 352 nm matched the emission energy of Au{sub 4} in the spherical jellium model, rather than the planar Au{sub 8}, which supported the emission of Au{sub 4} formed in G4-OH. Despite the change of [HAuCl{sub 4} ]/[G4-OH], the relative population between Au{sub 4} and Au{sub 8} was similar in G4-OH(Au), which indicated that the closed electronic and geometric structures stabilized the magic number of Au{sub 4}.

  2. Platinum and Other Transition Metal Nanoclusters (Pd, Rh) Stabilized by PAMAM Dendrimer as Excellent Heterogeneous Catalysts: Application to the Methylcyclopentane (MCP) Hydrogenative Isomerization.

    Science.gov (United States)

    Deraedt, Christophe; Melaet, Gérôme; Ralston, Walter T; Ye, Rong; Somorjai, Gabor A

    2017-03-08

    Pt, Rh, and Pd nanoclusters stabilized by PAMAM dendrimer are used for the first time in a gas flow reactor at high temperature (150-250 °C). Pt nanoclusters show a very high activity for the hydrogenation of the methylcyclopentane (MCP) at 200-225 °C with turnover freqency (TOF) up to 334 h(-1) and selectivity up to 99.6% for the ring opening isomerization at very high conversion (94%). Rh nanoclusters show different selectivity for the reaction, that is, ring opening isomerization at 175 °C and cracking at higher temperature whereas Pd nanoclusters perform ring enlargement plus dehydrogenation, while maintaining a high activity. The difference in these results as compared to unsupported/uncapped nanoparticles, demonstrates the crucial role of dendrimer. The tunability of the selectivity of the reaction as well as the very high activity of the metal nanoclusters stabilized by dendrimer under heterogeneous conditions open a new application for dendrimer catalysts.

  3. Dendrimer Prodrugs

    Directory of Open Access Journals (Sweden)

    Soraya da Silva Santos

    2016-05-01

    Full Text Available The main objective of this review is to describe the importance of dendrimer prodrugs in the design of new drugs, presenting numerous applications of these nanocomposites in the pharmaceutical field. Therefore, the use of dendrimer prodrugs as carrier for drug delivery, to improve pharmacokinetic properties of prototype, to promote drug sustained-release, to increase selectivity and, consequently, to decrease toxicity, are just some examples of topics that have been extensively reported in the literature, especially in the last decade. The examples discussed here give a panel of the growing interest dendrimer prodrugs have been evoking in the scientific community.

  4. Dendrimers in drug research

    DEFF Research Database (Denmark)

    Boas, Ulrik; Heegaard, Peter M. H.

    2004-01-01

    Dendrimers are versatile, derivatisable, well-defined, compartmentalised chemical polymers with sizes and physicochemical properties resembling those of biomolecules e.g. proteins. The present critical review (citing 158 references) briefly describes dendrimer design, nomenclature and divergent/c...

  5. Dendrimers in drug research

    DEFF Research Database (Denmark)

    Boas, Ulrik; Heegaard, Peter M. H.

    2004-01-01

    Dendrimers are versatile, derivatisable, well-defined, compartmentalised chemical polymers with sizes and physicochemical properties resembling those of biomolecules e.g. proteins. The present critical review (citing 158 references) briefly describes dendrimer design, nomenclature and divergent/c...

  6. Dendrimer-surfactant interactions.

    Science.gov (United States)

    Cheng, Yiyun; Zhao, Libo; Li, Tianfu

    2014-04-28

    In this article, we reviewed the interactions between dendrimers and surfactants with particular focus on the interaction mechanisms and physicochemical properties of the yielding dendrimer-surfactant aggregates. In order to provide insight into the behavior of dendrimers in biological systems, the interactions of dendrimers with bio-surfactants such as phospholipids in bulk solutions, in solid-supported bilayers and at the interface of phases or solid-states were discussed. Applications of the dendrimer-surfactant aggregates as templates to guide the synthesis of nanoparticles and in drug or gene delivery were also mentioned.

  7. Carbosilane and Carbosiloxane Dendrimers

    Directory of Open Access Journals (Sweden)

    Jang Hwan Hong

    2009-09-01

    Full Text Available This review focuses on novel carbosilane dendrimers containing branches with Si-C and Si-O-C bonds. Introduction of organic moieties into the dendrimers is performed by hydrosilation of carbon-carbon double/triple bonds. Versatile organic or organometallic moieties are introduced onto the peripheral regions of dendrimers by coupling and complexation reactions, which clearly demonstrates their potential for variation.

  8. Dendrimers in Medicine

    DEFF Research Database (Denmark)

    Wu, Linping; Ficker, Mario; Christensen, Jørn Bolstad

    2015-01-01

    Dendrimers are three-dimensional macromolecular structures originating from a central core molecule and surrounded by successive addition of branching layers (generation). These structures exhibit a high degree of molecular uniformity, narrow molecular weight distribution, tunable size and shape ...... as challenging issues surrounding the future development of dendrimer-based medicines....

  9. Size-selective synthesis of immobilized copper oxide nanoclusters on silica

    Energy Technology Data Exchange (ETDEWEB)

    Lomnicki, Slawo M., E-mail: slomni1@lsu.edu [Louisiana State University, Department of Chemistry, 232 Choppin Hall, Baton Rouge, LA 70803-1804 (United States); Wu, Hongyi; Osborne, Scott N.; Pruett, Jeff M.; McCarley, Robin L.; Poliakoff, Erwin; Dellinger, Barry [Louisiana State University, Department of Chemistry, 232 Choppin Hall, Baton Rouge, LA 70803-1804 (United States)

    2010-11-25

    We report a straightforward route for preparing bulk quantities of size-controlled and low size dispersity copper oxide nanoclusters on amorphous silica. Adsorption of the copper-dendrimer complex on the silica surface minimizes aggregation, which results in previously unachieved low size dispersity of the nanoclusters. Copper oxide nanoclusters with mean diameters of 1-5 nm with size dispersities of only 8-15% were prepared by calcination of silica impregnated with Cu(II)-poly(propylene imine) dendrimer complexes of varying stoichiometry. The size and size distribution of the copper oxide nanoparticles are tunably controlled by the ratio of the Cu(II) to the terminal primary amines in the copper-dendrimer complex, DAB-Am{sub n}-Cu(II){sub x}, the surface coverage of the DAB-Am{sub n}-Cu(II){sub x}, and the impregnation procedure. This method is anticipated to be useful in the preparation of other metal oxide nanoparticles, e.g., Ni and Fe, and with other oxide substrates.

  10. Size-selective synthesis of immobilized copper oxide nanoclusters on silica.

    Science.gov (United States)

    Lomnicki, Slawo M; Wu, Hongyi; Osborne, Scott N; Pruett, Jeff M; McCarley, Robin L; Poliakoff, Erwin; Dellinger, Barry

    2010-11-25

    We report a straightforward route for preparing bulk quantities of size-controlled and low size dispersity copper oxide nanoclusters on amorphous silica. Adsorption of the copper-dendrimer complex on the silica surface minimizes aggregation, which results in previously unachieved low size dispersity of the nanoclusters. Copper oxide nanoclusters with mean diameters of 1-5 nm with size dispersities of only 8-15% were prepared by calcination of silica impregnated with Cu(II)-poly(propylene imine) dendrimer complexes of varying stoichiometry. The size and size distribution of the copper oxide nanoparticles are tunably controlled by the ratio of the Cu(II) to the terminal primary amines in the copper-dendrimer complex, DAB-Am n -Cu(II) x , the surface coverage of the DAB-Am n -Cu(II) x , and the impregnation procedure. This method is anticipated to be useful in the preparation of other metal oxide nanoparticles, e.g., Ni and Fe, and with other oxide substrates.

  11. Supramolecular Organization of Functional Dendrimers

    Institute of Scientific and Technical Information of China (English)

    D.Guillon; B.Donnio

    2007-01-01

    1 Results The possibility to develop large multifunctional macromolecular structures which can further self-assemble into nanosized objects,makes liquid-crystalline dendrimers highly attractive candidates in the field of materials science and may represent an original strategy for the realisation of molecular electronic-based devices[1-2].Sophisticated nanostructures obtained with dendrimers where mesogenic groups are not only located at the periphery of the dendrimer[3] but also at the branching points...

  12. DENDRIMER CONJUGATES FOR SELECTIVE OF PROTEIN AGGREGATES

    DEFF Research Database (Denmark)

    2004-01-01

    Dendrimer conjugates are presented, which are formed between a dendrimer and a protein solubilising substance. Such dendrimer conjugates are effective in the treatment of protein aggregate-related diseases (e.g. prion-related diseases). The protein solubilising substance and the dendrimer together...

  13. Precise Synthesis of Organometallic Dendrimers

    Institute of Scientific and Technical Information of China (English)

    K. Onitsuka; S. Takahashi

    2005-01-01

    @@ 1Introduction Dendrimers possessing a regularly branched architecture and large spherical dimensions have attracted significant attention because of their unique and tunable properties as well as their potential applications. The incorporation of organometallic species into dendritic molecules has been attracting much attention, because the addition of properties characteristic of organometallic complexes, such as magnetic, electronic, and photo-optical properties, as well as reactivity may lead to the realization of new functionalized dendrimers. Although there are many examples of organometallic dendrimers that contain metallic species at the core or at the periphery, dendrimers composed of organometallic complexes in each generation are still limited. We present here convergent and divergent approaches to novel organometallic dendrimers, of which the skeletons were built up with platinum-acetylide units.

  14. Entanglement in Anderson Nanoclusters

    CERN Document Server

    Samuelsson, Peter

    2007-01-01

    We investigate the two-particle spin entanglement in magnetic nanoclusters described by the periodic Anderson model. An entanglement phase diagram is obtained, providing a novel perspective on a central property of magnetic nanoclusters, namely the temperature dependent competition between local Kondo screening and nonlocal Ruderman-Kittel-Kasuya-Yoshida spin ordering. We find that multiparticle entangled states are present for finite magnetic field as well as in the mixed valence regime and away from half filling. Our results emphasize the role of charge fluctuations.

  15. Phosphorus dendrimers and photodynamic therapy. Spectroscopic studies on two dendrimer-photosensitizer complexes: Cationic phosphorus dendrimer with rose bengal and anionic phosphorus dendrimer with methylene blue.

    Science.gov (United States)

    Dabrzalska, Monika; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

    2015-08-15

    Dendrimers due to their unique architecture may play an important role in drug delivery systems including chemotherapy, gene therapy and recently, photodynamic therapy as well. We investigated two dendrimer-photosensitizer systems in context of potential use of these systems in photodynamic therapy. The mixtures of an anionic phosphorus dendrimer of the second generation and methylene blue were studied by UV-vis spectroscopy while that of a cationic phosphorus dendrimer (third generation) and rose bengal were investigated by spectrofluorimetric methods. Spectroscopic analysis of these two systems revealed the formation of dendrimer-photosensitizer complexes via electrostatic interactions as well as π stacking. The stoichiometry of the rose bengal-cationic dendrimer complex was estimated to be 7:1 and 9:1 for the methylene blue-anionic dendrimer complex. The results suggest that these polyanionic or polycationic phosphorus dendrimers can be promising candidates as carriers in photodynamic therapy.

  16. Fluorous Mixture Synthesis of Asymmetric Dendrimers

    Science.gov (United States)

    Jiang, Zhong-Xing; Yu, Yihua Bruce

    2010-01-01

    A divergent fluorous mixture synthesis (FMS) of asymmetric fluorinated dendrimers has been developed. Four generations of fluorinated dendrimers with the same fluorinated moiety were prepared with high efficiency, yield and purity. Comparison of the physicochemical properties of these dendrimers provided valuable information for their application and future optimization. This strategy has not only provided a practical method for the synthesis and purification of dendrimers, but also established the possibility of utilizing the same fluorinated moiety for FMS. PMID:20170088

  17. Dynamics and Thermodynamics of Nanoclusters

    Directory of Open Access Journals (Sweden)

    Karo Michaelian

    2015-10-01

    Full Text Available The dynamic and thermodynamic properties of nanoclusters are studied in two different environments: the canonical and microcanonical ensembles. A comparison is made to thermodynamic properties of the bulk. It is shown that consistent and reproducible results on nanoclusters can only be obtained in the canonical ensemble. Nanoclusters in the microcanonical ensemble are trapped systems, and inconsistencies will be found if thermodynamic formalism is applied. An analytical model is given for the energy dependence of the phase space volume of nanoclusters, which allows the prediction of both dynamical and thermodynamical properties.

  18. Polyester Dendrimers: Smart Carriers for Drug Delivery

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    Jean–d’Amour K. Twibanire

    2014-01-01

    Full Text Available Polyester dendrimers have been shown to be outstanding candidates for biomedical applications. Compared to traditional polymeric drug vehicles, these biodegradable dendrimers show excellent advantages especially as drug delivery systems because they are non-toxic. Here, advances on polyester dendrimers as smart carriers for drug delivery applications have been surveyed. Both covalent and non-covalent incorporation of drugs are discussed.

  19. Dendrimer a versatile polymer in drug delivery

    Directory of Open Access Journals (Sweden)

    Singh Shakti

    2009-01-01

    Full Text Available Dendrimers are a unique class of synthetic macromolecules having highly branched, three-dimensional, nanoscale architecture with very low polydispersity and high functionality. Structural advantages allow dendrimers to play an important role in the fields of nanotechnology, pharmaceutical and medicinal chemistry. This review discusses several aspects of dendrimers, including preparation, dendrimer-drug coupling chemistry, structural models of dendrimer-based drug delivery systems, and physicochemical and toxicological properties. Dendrimers have emerged as one of the most interesting themes for researchers as a result of their unique architecture and macromolecular characteristics. Several groups are involved in exploring their potential as versatile carriers in drug delivery. The use of dendrimers in drug delivery has been reviewed extensively. The increasing relevance of the potential of dendrimers in drug delivery emphasizes the need to explore the routes by which they can be administered. The high level of control possible over the architectural design of dendrimers; their size, shape, branching length/density, and their surface functionality clearly distinguish these structures as unique and optimum carriers in those applications. The bioactive agents may be encapsulated into the interior of the dendrimers or chemically attached/physically adsorbed onto the dendrimer surface, with the option of tailoring the carrier to the specific needs of the active material and its therapeutic applications. This review clearly demonstrates the potential of this new fourth major class of polymer architecture and indeed substantiates the high hopes for the future of dendrimers.

  20. Synthesis and characterization of colloidal fluorescent silver nanoclusters.

    Science.gov (United States)

    Huang, Sherry; Pfeiffer, Christian; Hollmann, Jana; Friede, Sebastian; Chen, Justin Jin-Ching; Beyer, Andreas; Haas, Benedikt; Volz, Kerstin; Heimbrodt, Wolfram; Montenegro Martos, Jose Maria; Chang, Walter; Parak, Wolfgang J

    2012-06-19

    Ultrasmall water-soluble silver nanoclusters are synthesized, and their properties are investigated. The silver nanoclusters have high colloidal stability and show fluorescence in the red. This demonstrates that like gold nanoclusters also silver nanoclusters can be fluorescent.

  1. The specific contribution of phosphorus in dendrimer chemistry.

    Science.gov (United States)

    Majoral, Jean-Pierre; Caminade, Anne-Marie; Maraval, Valérie

    2002-12-21

    Besides properties commonly found for all types of dendrimers, phosphorus-containing dendrimers possess some specific properties seldom or never found for other types of dendrimers. Emphasis will be put on these specificities.

  2. Glycopeptide dendrimers as Pseudomonas aeruginosa biofilm inhibitors.

    Science.gov (United States)

    Reymond, Jean-Louis; Bergmann, Myriam; Darbre, Tamis

    2013-06-01

    Synthetic glycopeptide dendrimers composed of a branched oligopeptide tree structure appended with glycosidic groups at its multiple N-termini were investigated for binding to the Pseudomonas aeruginosa lectins LecB and LecA. These lectins are partly responsible for the formation of antibiotic resistant biofilms in the human pathogenic bacterium P. aeruginosa, which causes lethal airway infections in immune-compromised and cystic fibrosis patients. Glycopeptide dendrimers with high affinity to the lectins were identified by screening of combinatorial libraries. Several of these dendrimers, in particular the LecB specific glycopeptide dendrimers FD2 and D-FD2 and the LecA specific glycopeptide dendrimers GalAG2 and GalBG2, also efficiently block P. aeruginosa biofilm formation and induce biofilm dispersal in vitro. Structure-activity relationship and structural studies are reviewed, in particular the observation that multivalency is essential to the anti-biofilm effect in these dendrimers.

  3. Electrochemically induced nanocluster migration

    Energy Technology Data Exchange (ETDEWEB)

    Hartl, Katrin [Lehrstuhl Physikalische Chemie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85748 Garching (Germany); Department of Chemistry, CS06, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen O (Denmark); Nesselberger, Markus [Department of Chemistry, CS06, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen O (Denmark); Mayrhofer, Karl J.J. [MPI fuer Eisenforschung, Abt. Grenzflaechenchemie und Oberflaechentechnik, Max-Planck-Strasse 1, D-40237 Duesseldorf (Germany); Kunz, Sebastian; Schweinberger, Florian F.; Kwon, GiHan [Lehrstuhl Physikalische Chemie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85748 Garching (Germany); Hanzlik, Marianne [Institut fuer Elektronenmikroskopie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85748 Garching (Germany); Heiz, Ueli [Lehrstuhl Physikalische Chemie, Technische Universitaet Muenchen, Lichtenbergstr. 4, D-85748 Garching (Germany); Arenz, Matthias, E-mail: m.arenz@kemi.ku.d [Department of Chemistry, CS06, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen O (Denmark)

    2010-12-30

    In the presented study the influence of electrochemical treatments on size-selected Pt nanoclusters (NCs) supported on amorphous carbon is investigated by means of transmission electron microscopy (TEM). Well-defined Pt NCs are prepared by an ultra-high vacuum (UHV) laser vaporization source and deposited with low kinetic energy ({<=}10 eV/cluster) onto TEM gold grids covered by a thin (2 nm) carbon film. After transfer out of UHV Pt NCs are verified to be uniform in size and randomly distributed on the support. Subsequently, the TEM grids are employed as working electrodes in a standard electrochemical three electrode setup and the Pt nanoclusters are subjected to different electrochemical treatments. It is found that the NC arrangement is not influenced by potential hold conditions (at 0.40 V vs. RHE) or by potential cycling in a limited potential window (V{sub max} = 0.55 V vs. RHE). Upon potential cycling to 1.05 V vs. RHE, however, the NCs migrate on the carbon support. Interestingly, migration in oxygen or argon saturated electrolyte leads to NC coalescence, a mechanism discussed for being responsible for performance degradation of low temperature fuel cells, whereas in carbon monoxide saturated electrolyte the Pt NC agglomerate, but remain separated from each other and thus form distinctive structures.

  4. Synthesis Nano Dendrimer Supramolecular with Melamine Core

    Directory of Open Access Journals (Sweden)

    Samaneh Maghsoodi,

    2016-12-01

    Full Text Available Dendrimers are a family of three-dimensional polymers and in nano dimension which are characterized by spherical structure. Excellent structural properties of dendrimers have distinguished them completely from linear polymers. Dendrimers have monodispersity characteristic and their size and molecular weight is controllable exactly during synthesis such as PAMAM dendrimers.Melamine can be used for synthetic core dendrimer through various methods including divergent. Melamine and related derivatives are able to form self-assembling compound via organized intramolecular networks of hydrogen bonds and provide useful molecular scaffolding components which are exploited by the field of supramolecular chemistry; which is beyond covalent bonding. In this study, the dendrimers of generated 0.5 and 1 with ester and primary amine-terminated groups with melamine and methyl acrylate were synthesized. The Synthesized dendrimer is able to form hydrogen bonding due to its nitrogen, oxygen and hydrogen atoms which was led to supramolecule characteristic. The reaction products were identified with H NMR, and 13C NMR, FT-IR, MASS spectroscopic techniques. Also nano properties of the supramoleculs were determined by X-ray diffraction method.Supramolecular characteristics of synthesized dendrimer can be studied by shifts in H-NMR peaks and also flattening of FT-IR spectrum.The synthesized dendrimer derivatives are promising for environmental and medical applications. Also, such compounds might be reacting with transition metals as ligand and could be served as catalysts.

  5. High Fluorescent Porphyrin-PAMAM-Fluorene Dendrimers.

    Science.gov (United States)

    Garfias-Gonzalez, Karla I; Organista-Mateos, Ulises; Borja-Miranda, Andrés; Gomez-Vidales, Virginia; Hernandez-Ortega, Simon; Cortez-Maya, Sandra; Martínez-García, Marcos

    2015-05-13

    Two new classes of dendrimers bearing 8 and 32 fluorene donor groups have been synthesized. The first and second generations of these porphyrin-PAMAM-fluorene dendrimers were characterized by 1H-NMR, 13C-NMR, FTIR, UV-vis spectroscopy, elemental analyses and MALDI-TOF mass spectrometry. The UV-vis spectra showed that the individual properties of donor and acceptor moieties were preserved, indicating that the new dendrimers could be used as photosynthetic antennae. Furthermore, for fluorescent spectroscopy, these dendrimers showed good energy transfer.

  6. Orientational relaxation in semiflexible dendrimers.

    Science.gov (United States)

    Kumar, Amit; Biswas, Parbati

    2013-12-14

    The orientational relaxation dynamics of semiflexible dendrimers are theoretically calculated within the framework of optimized Rouse-Zimm formalism. Semiflexibility is modeled through appropriate restrictions in the direction and orientation of the respective bond vectors, while the hydrodynamic interactions are included via the preaveraged Oseen tensor. The time autocorrelation function M(i)(1)(t) and the second order orientational autocorrelation function P(i)(2)(t) are analyzed as a function of the branch-point functionality and the degree of semiflexibility. Our approach of calculating M(i)(1)(t) is completely different from that of the earlier studies (A. Perico and M. Guenza J. Chem. Phys., 1985, 83, 3103; J. Chem. Phys., 1986, 84, 510), where the expression of M(i)(1)(t) obtained from earlier studies does not demarcate the flexible dendrimers from the semiflexible ones. The component of global motion of the time autocorrelation function exhibits a strong dependence on both degree of semiflexibility and branch-point functionality, while the component of pulsation motion depends only on the degree of semiflexibility. But it is difficult to distinguish the difference in the extent of pulsation motion among the compressed (0 qualitative behavior of P(i)(2)(t) obtained from our calculations closely matches with the expression for P(exact)(2)(t) in the earlier studies. Theoretically calculated spectral density, J(ω), is found to depend on the degree of semiflexibility and the branch-point functionality for the compressed and expanded conformations of semiflexible dendrimers as a function of frequency, especially in the high frequency regime, where J(ω) decays with frequency for both compressed and expanded conformations of semiflexible dendrimers. This decay of the spectral density occurs after displaying a cross-over behavior with the variation in the degree of semiflexibility in the intermediate frequency regime. The characteristic area increases with the

  7. Uses of Dendrimers for DNA Microarrays

    Science.gov (United States)

    Caminade, Anne-Marie; Padié, Clément; Laurent, Régis; Maraval, Alexandrine; Majoral, Jean-Pierre

    2006-01-01

    Biosensors such as DNA microarrays and microchips are gaining an increasing importance in medicinal, forensic, and environmental analyses. Such devices are based on the detection of supramolecular interactions called hybridizations that occur between complementary oligonucleotides, one linked to a solid surface (the probe), and the other one to be analyzed (the target). This paper focuses on the improvements that hyperbranched and perfectly defined nanomolecules called dendrimers can provide to this methodology. Two main uses of dendrimers for such purpose have been described up to now; either the dendrimer is used as linker between the solid surface and the probe oligonucleotide, or the dendrimer is used as a multilabeled entity linked to the target oligonucleotide. In the first case the dendrimer generally induces a higher loading of probes and an easier hybridization, due to moving away the solid phase. In the second case the high number of localized labels (generally fluorescent) induces an increased sensitivity, allowing the detection of small quantities of biological entities.

  8. Nanocluster technologies for electronics design

    CERN Document Server

    Parker, A J

    2001-01-01

    based electronic systems. The work presented in this thesis covers an investigation into the use of metal nanoclusters in nanoelectronics design. Initial studies explored the interactions of the dodecanethiol passivated gold nanocluster, held in solution with toluene, and the native oxide covered silicon surface. Deposition of the clusters is achieved by pippetting mu-litre quantities of the solution onto the surface, and allowing the solvent to evaporate leaving the clusters as residue. Patterning of the surface with micron scale photoresist structures prior to cluster exposure, led to the selective aggregation of cluster deposits along the resist boundaries. An extension of this technique, examined the flow of the cluster solution along photoresist structures which extended beyond the solution droplet. Investigation into the electronic properties of nanocluster arrays generated non-linear current-voltage curves, which are explained in terms of two very simple models. These results cast doubt over the suitab...

  9. Conductive dendrimers obtained by click chemistry

    Science.gov (United States)

    Lewis, Donald G.; Krasnova, Larissa B.; Skinner, Philip J.; Fokin, Valery V.

    2010-08-01

    First generation dendrimers having a high level of size/shape/symmetry homogeneity were fabricated using a synthetic scheme that employs highly quantitative copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions in combination with a molecular architecture that favors homogeneity. An "outside-in" or convergent synthetic approach was employed wherein dendrons having Sierpinski triangular fractal architectures were coupled to core structures having D2h or D3h point group symmetries to form the desired dendrimers. The individual dendrons consisted of branched-backbone conductive polymers having benzene branch points and 1,2,3-triazole linkages with uninterrupted π-electron cloud overlap throughout. Each dendron was then coupled to a benzene core structure having acetylene substituents by means of a CuAAC reaction so as to extend the uninterrupted π-conjugation from the dendron to the core structure for imparting conductivity throughout the entire dendrimer. The resulting dendrimers maintained the point group symmetry of their core structure, with the core structure serving to electronically couple the dendrons to one another by extension of their uninterrupted π-electron systems. Synthesis of these first generation dendrimers provides a proof of principle for the synthesis of higher generation conductive dendrimers. Since the nanophotonic properties of conductive dendrimers may be dependent, at least in some instances, upon their size, shape, and symmetry, enhancements with respect to their homogeneity may unmask new nanophotonic properties.

  10. The Olefin Metathesis Reactions in Dendrimers

    Science.gov (United States)

    Astruc, Didier

    Dendrimers containing terminal olefins or ruthenium-benzylidene terminal groups undergo olefin metathesis reactions (RCM and ROMP types), and essentially results from our group are reviewed here. Dendrimers have been loaded at their periphery with ruthenium-chelating bis-phosphines, which leads to the formation of dendrimer-cored stars by ring-opening-metathesis polymerization (ROMP). CpFe+-induced perallylation of polymethylaromatics (Cp = η5-C5H5) followed by ring-closing metathesis (RCM) and/or cross metathesis (CM) leads to poly-ring, cage, oligomeric and polymeric architectures. In the presence of acrylic acid or metha-crylate, stereospecific CM inhibits oligomerization, and dendritic olefins yield polyacid dendrimers. Finally, cros-metahesis reactions with dendronic acrylate allow dendritic construction and growth.

  11. On Topological Indices of Certain Dendrimer Structures

    Science.gov (United States)

    Aslam, Adnan; Bashir, Yasir; Ahmad, Safyan; Gao, Wei

    2017-05-01

    A topological index can be considered as transformation of chemical structure in to real number. In QSAR/QSPR study, physicochemical properties and topological indices such as Randić, Zagreb, atom-bond connectivity ABC, and geometric-arithmetic GA index are used to predict the bioactivity of chemical compounds. Dendrimers are highly branched, star-shaped macromolecules with nanometer-scale dimensions. Dendrimers are defined by three components: a central core, an interior dendritic structure (the branches), and an exterior surface with functional surface groups. In this paper we determine generalised Randić, general Zagreb, general sum-connectivity indices of poly(propyl) ether imine, porphyrin, and zinc-Porphyrin dendrimers. We also compute ABC and GA indices of these families of dendrimers.

  12. New dendrimer - Peptide host - Guest complexes: Towards dendrimers as peptide carriers

    DEFF Research Database (Denmark)

    Boas, Ulrik; Sontjens, S.H.M.; Jensen, Knud Jørgen;

    2002-01-01

    Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions...

  13. DNA Condensation by Partially Acetylated Poly(amido amine Dendrimers: Effects of Dendrimer Charge Density on Complex Formation

    Directory of Open Access Journals (Sweden)

    Ronald G. Larson

    2013-09-01

    Full Text Available The ability of poly(amido amine (or PAMAM dendrimers to condense semiflexible dsDNA and penetrate cell membranes gives them great potential in gene therapy and drug delivery but their high positive surface charge makes them cytotoxic. Here, we describe the effects of partial neutralization by acetylation on DNA condensation using light scattering, circular dichroism, and single molecule imaging of dendrimer-DNA complexes combed onto surfaces and tethered to those surfaces under flow. We find that DNA can be condensed by generation-five (G5 dendrimers even when the surface charges are more than 65% neutralized, but that such dendrimers bind negligibly when an end-tethered DNA is stretched in flow. We also find that when fully charged dendrimers are introduced by flow to end-tethered DNA, all DNA molecules become equally highly coated with dendrimers at a rate that becomes very fast at high dendrimer concentration, and that dendrimers remain bound during subsequent flow of dendrimer-free buffer. These results suggest that the presence of dendrimer-free DNA coexisting with dendrimer-bound DNA after bulk mixing of the two in solution may result from diffusion-limited irreversible dendrimer-DNA binding, rather than, or in addition to, the previously proposed cooperative binding mechanism of dendrimers to DNA.

  14. Oligothia dendrimers for the formation of gold nanoparticles

    NARCIS (Netherlands)

    d'Aleo, A.; Williams, R.M.; Osswald, F.; Edamana, P.; Hahn, U.; van Heyst, J.; Tichelaar, F.D.; Voegtle, F.; De Cola, L.

    2004-01-01

    The synthesis and characterization of oligothia dendrimers and their use for the formation of gold nanoparticles is described. The role played by these dendrimers in controlling the stability and size of the particles is discussed. It is shown that the generation of the dendrimers, as well as the

  15. Oligothia dendrimers for the formation of gold nanoparticles

    NARCIS (Netherlands)

    d'Aleo, A.; Williams, R.M.; Osswald, F.; Edamana, P.; Hahn, U.; van Heyst, J.; Tichelaar, F.D.; Voegtle, F.; De Cola, L.

    2004-01-01

    The synthesis and characterization of oligothia dendrimers and their use for the formation of gold nanoparticles is described. The role played by these dendrimers in controlling the stability and size of the particles is discussed. It is shown that the generation of the dendrimers, as well as the po

  16. Phosphorescent Nanocluster Light-Emitting Diodes.

    Science.gov (United States)

    Kuttipillai, Padmanaban S; Zhao, Yimu; Traverse, Christopher J; Staples, Richard J; Levine, Benjamin G; Lunt, Richard R

    2016-01-13

    Devices utilizing an entirely new class of earth abundant, inexpensive phosphorescent emitters based on metal-halide nanoclusters are reported. Light-emitting diodes with tunable performance are demonstrated by varying cation substitution to these nanoclusters. Theoretical calculations provide insight about the nature of the phosphorescent emitting states, which involves a strong pseudo-Jahn-Teller distortion.

  17. Transition Metal Catalysis Using Functionalized Dendrimers.

    Science.gov (United States)

    Oosterom, G. Eric; Reek, Joost N. H.; Kamer, Paul C. J.; van Leeuwen, Piet W. N. M.

    2001-05-18

    Dendrimers are well-defined hyperbranched macromolecules with characteristic globular structures for the larger systems. These novel polymers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them. The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers, resulting in a rapid development of dendrimer chemistry. The position of the catalytic site(s) as well as the spatial separation of the catalysts appears to be of crucial importance. Dendrimers that are functionalized with transition metals in the core potentially can mimic the properties of enzymes, their efficient natural counterparts, whereas the surface-functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis. This might yield superior catalysts with novel properties, that is, special reactivity or stability. Both the core and periphery strategies lead to catalysts that are sufficiently larger than most substrates and products, thus separation by modern membrane separation techniques can be applied. These novel homogeneous catalysts can be used in continuous membrane reactors, which will have major advantages particularly for reactions that benefit from low substrate concentrations or suffer from side reactions of the product. Here we review the recent progress and breakthroughs made with these promising novel transition metal functionalized dendrimers that are used as catalysts, and we will discuss the architectural concepts that have been applied.

  18. PREPARATION OF CHEMICALLY WELL-DEFINED CARBOHYDRATE DENDRIMER CONJUGATES

    DEFF Research Database (Denmark)

    2004-01-01

    A method for the synthesis of dendrimer conjugates having a well-defined chemical structure, comprising one or more carbohydrate moieties and one or more immunomodulating substances coupled to a dendrimer, is presented. First, the carbohydrate is bound to the dendrimer in a chemoselective manner....... Subsequently, the immunomodulating substance is also bound in a chemoselective manner, to give a dendrimer conjugate with a well-defined structure and connectivity and containing a precise, pre-determined ratio of carbohydrate to immunomodulating substance. The invention also relates to novel dendrimer...

  19. Tetrahedron DNA dendrimers and their encapsulation of gold nanoparticles.

    Science.gov (United States)

    Zhou, Tao; Wang, Yijie; Dong, Yuanchen; Chen, Chun; Liu, Dongsheng; Yang, Zhongqiang

    2014-08-15

    DNA dendrimers have achieved increasing attention recently. Previously reported DNA dendrimers used Y-DNA as monomers. Tetrahedron DNA is a rigid tetrahedral cage made of DNA. Herein, we use tetrahedron DNA as monomers to prepare tetrahedron DNA dendrimers. The prepared tetrahedron DNA dendrimers have larger size compared with those made of Y-DNA. In addition, thanks to the central cavity of tetrahedron DNA monomers, some nanoscale structures (e.g., gold nanoparticles) can be encapsulated within tetrahedron DNA monomers. Tetrahedron DNA encapsulated with gold nanoparticles can be further assembled into dendrimers, guiding gold nanoparticles into clusters.

  20. Comparison of generation 3 polyamidoamine dendrimer and generation 4 polypropylenimine dendrimer on drug loading, complex structure, release behavior, and cytotoxicity

    Directory of Open Access Journals (Sweden)

    Shao N

    2011-12-01

    Full Text Available Naimin Shao1, Yunzhang Su1, Jingjing Hu2, Jiahai Zhang3, Hongfeng Zhang1, Yiyun Cheng1,41School of Life Sciences, East China Normal University, Shanghai, 2CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, Hefei,  3School of Life Sciences, University of Science and Technology of China, Hefei, 4Shanghai Key Laboratory of Magnetic Resonance, Department of Physics, East China Normal University, Shanghai, ChinaBackground: Polyamidoamine (PAMAM and polypropylenimine (PPI dendrimers are the commercially available and most widely used dendrimers in pharmaceutical sciences and biomedical engineering. In the present study, the loading and release behaviors of generation 3 PAMAM and generation 4 PPI dendrimers with the same amount of surface amine groups (32 per dendrimer were compared using phenylbutazone as a model drug.Methods: The dendrimer-phenylbutazone complexes were characterized by 1H nuclear magnetic resonance and nuclear Overhauser effect techniques, and the cytotoxicity of each dendrimer was evaluated.Results: Aqueous solubility results suggest that the generation 3 PAMAM dendrimer has a much higher loading ability towards phenylbutazone in comparison with the generation 4 PPI dendrimer at high phenylbutazone-dendrimer feeding ratios. Drug release was much slower from the generation 3 PAMAM matrix than from the generation 4 PPI dendrimer. In addition, the generation 3 PAMAM dendrimer is at least 50-fold less toxic than generation 4 PPI dendrimer on MCF-7 and A549 cell lines.Conclusion: Although the nuclear Overhauser effect nuclear magnetic resonance results reveal that the generation 4 PPI dendrimer with a more hydrophobic interior encapsulates more phenylbutazone, the PPI dendrimer-phenylbutazone inclusion is not stable in aqueous solution, which poses a great challenge during drug development.Keywords: dendrimer, polyamidoamine, polypropylenimine, drug delivery, cytotoxicity

  1. Molecular Dynamics Study of the Structure, Flexibility, and Hydrophilicity of PETIM Dendrimers: A Comparison with PAMAM Dendrimers.

    Science.gov (United States)

    Kanchi, Subbarao; Suresh, Gorle; Priyakumar, U Deva; Ayappa, K G; Maiti, Prabal K

    2015-10-15

    A new class of dendrimers, the poly(propyl ether imine) (PETIM) dendrimer, has been shown to be a novel hyperbranched polymer having potential applications as a drug delivery vehicle. Structure and dynamics of the amine terminated PETIM dendrimer and their changes with respect to the dendrimer generation are poorly understood. Since most drugs are hydrophobic in nature, the extent of hydrophobicity of the dendrimer core is related to its drug encapsulation and retention efficacy. In this study, we carry out fully atomistic molecular dynamics (MD) simulations to characterize the structure of PETIM (G2-G6) dendrimers in salt solution as a function of dendrimer generation at different protonation levels. Structural properties such as radius of gyration (Rg), radial density distribution, aspect ratio, and asphericity are calculated. In order to assess the hydrophilicity of the dendrimer, we compute the number of bound water molecules in the interior of dendrimer as well as the number of dendrimer-water hydrogen bonds. We conclude that PETIM dendrimers have relatively greater hydrophobicity and flexibility when compared with their extensively investigated PAMAM counterparts. Hence PETIM dendrimers are expected to have stronger interactions with lipid membranes as well as improved drug encapsulation and retention properties when compared with PAMAM dendrimers. We compute the root-mean-square fluctuation of dendrimers as well as their entropy to quantify the flexibility of the dendrimer. Finally we note that structural and solvation properties computed using force field parameters derived based on the CHARMM general purpose force field were in good quantitative agreement with those obtained using the generalized Amber force field (GAFF).

  2. Brief Timelapse on Dendrimer Chemistry: Advances, Limitations, and Expectations

    KAUST Repository

    Ornelas, Catia

    2015-12-09

    © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Dendrimers are well-defined branched macromolecules that have been studied for a wide variety of applications. Possibility to add multiple functionalities in precise locations of the dendritic structure generated great expectations for the application of dendrimers in nanomedicine, however, the number of dendrimer-based formulations that advance to clinical studies has been somewhat deceiving. This is partially due to the nonreproducible pharmokinetic behavior observed for multifunctional dendrimers synthesized through the random-statistical approach that leads to mixtures of products. Therefore, it is crucial to develop multifunctional dendrimers with well-defined structures in order to increase the chances of meeting the clinical expectations placed on dendrimers. This talent article will give an overview of the dendrimer field, discussing the application of dendrimers in nanomedicine, light-harvesting systems, sensing and catalysis, with a critical analysis on the expectations, limitations, advances, current challenges and future directions. Dendrimer timelapse demonstrates constant evolution in dendrimer chemistry enabling their application in nanomedicine, protein mimic, catalysis, light harvesting systems, and sensing. Increasing the variety of functionalities in dendrimers located at precise sites of the dendritic backbone result in versatile multifunctional nanomaterials that in the future might approach the conceptual nanobots.

  3. Synthesis and properties of new amphoteric poly(amidoamine dendrimers

    Directory of Open Access Journals (Sweden)

    2009-08-01

    Full Text Available A series of new amphoteric dendrimers have been synthesized by attaching dimethylbenzylaminoethyl acrylate chloride (Bz80, sodium acrylic acid (SAA and modified polyoxyethylene (MPEO units to a third-generation poly(amidoamine (PAMAM dendrimer core via Michael addition reaction. The structure of the dendrimers was confirmed by Fourier transform infrared (FTIR, proton nuclear magnetic resonance (1H NMR, carbon 13 nuclear magnetic resonance (13C NMR spectroscopy and by elemental analysis. Thermal stability and intrinsic viscosity were investigated. The applicable experiment exhibited the amphoteric dendrimers have high flocculation efficiency, which could be significantly improved by combining amphoteric dendrimers with polyacrylamide (PAM. The suitable mass ratio of the dendrimers and PAM was 2:3. The study would promote the use of amphoteric dendrimers as a flocculant in treating wastewater and as a new paper retention aid in papermaking.

  4. Uses of Dendrimers for DNA Microarrays

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Majoral

    2006-08-01

    Full Text Available Biosensors such as DNA microarrays and microchips are gaining an increasingimportance in medicinal, forensic, and environmental analyses. Such devices are based onthe detection of supramolecular interactions called hybridizations that occur betweencomplementary oligonucleotides, one linked to a solid surface (the probe, and the other oneto be analyzed (the target. This paper focuses on the improvements that hyperbranched andperfectly defined nanomolecules called dendrimers can provide to this methodology. Twomain uses of dendrimers for such purpose have been described up to now; either thedendrimer is used as linker between the solid surface and the probe oligonucleotide, or thedendrimer is used as a multilabeled entity linked to the target oligonucleotide. In the firstcase the dendrimer generally induces a higher loading of probes and an easier hybridization,due to moving away the solid phase. In the second case the high number of localized labels(generally fluorescent induces an increased sensitivity, allowing the detection of smallquantities of biological entities.

  5. Multivalent supramolecular dendrimer-based drugs.

    Science.gov (United States)

    Galeazzi, Simone; Hermans, Thomas M; Paolino, Marco; Anzini, Maurizio; Mennuni, Laura; Giordani, Antonio; Caselli, Gianfranco; Makovec, Francesco; Meijer, E W; Vomero, Salvatore; Cappelli, Andrea

    2010-01-11

    Supramolecular complexes consisting of a hydrophobic dendrimer host [DAB-dendr-(NHCONH-Ad)(64)] as well as solubilizing and bioactive guest molecules have been synthesized using a noncovalent approach. The guest-host supramolecular assembly is first preassembled in chloroform and transferred via the neat phase to aqueous solution. The bioactive guest molecules can bind to a natural (serotonin 5-HT(3)) receptor with nanomolar affinity as well as to the synthetic dendrimer receptor in aqueous solution, going toward a dynamic multivalent supramolecular construct capable of adapting itself to a multimeric receptor motif.

  6. Dendrimers for Vaccine and Immunostimulatory Uses

    DEFF Research Database (Denmark)

    Heegaard, Peter M. H.; Boas, Ulrik; Sørensen, Nanna Skall

    2010-01-01

    for efficient immunostimulating compounds (adjuvants) that can increase the efficiency of vaccines, as dendrimers can provide molecularly defined multivalent scaffolds to produce highly defined conjugates with small molecule immunostimulators and/or antigens. The review gives an overview on the use...... of dendrimers as molecularly defined carriers/presenters of small antigens, including constructs that have built-in immunostimulatory (adjuvant) properties, and as stand-alone adjuvants that can be mixed with antigens to provide efficient vaccine formulations. These approaches allow the preparation...... of molecularly defined vaccines with highly predictable and specific properties and enable knowledge-based vaccine design substituting the traditional empirically based approaches for vaccine development and production....

  7. Dendrimer based nanotherapeutics for ocular drug delivery

    Science.gov (United States)

    Kambhampati, Siva Pramodh

    PAMAM dendrimers are a class of well-defined, hyperbranched polymeric nanocarriers that are being investigated for ocular drug and gene delivery. Their favorable properties such as small size, multivalency and water solubility can provide significant opportunities for many biologically unstable drugs and allows potentially favorable ocular biodistribution. This work exploits hydroxyl terminated dendrimers (G4-OH) as drug/gene delivery vehicles that can target retinal microglia and pigment epithelium via systemic delivery with improved efficacy at much lower concentrations without any side effects. Two different drugs Triamcinolone acetonide (TA) and N-Acetyl Cysteine (NAC) conjugated to G4-OH dendrimers showed tailorable sustained release in physiological relevant solutions and were evaluated in-vitro and in-vivo. Dendrimer-TA conjugates enhanced the solubility of TA and were 100 fold more effective at lower concentrations than free TA in its anti-inflammatory activity in activated microglia and in suppressing VEGF production in hypoxic RPE cells. Dendrimers targeted activated microglia/macrophages and RPE and retained for a period of 21 days in I/R mice model. The relative retention of intravitreal and intravenous dendrimers was comparable, if a 30-fold intravenous dose is used; suggesting intravenous route targeting retinal diseases are possible with dendrimers. D-NAC when injected intravenously attenuated retinal and choroidal inflammation, significantly reduced (˜73%) CNV growth at early stage of AMD in rat model of CNV. A combination therapy of D-NAC + D-TA significantly suppressed microglial activation and promoted CNV regression in late stages of AMD without causing side-effects. G4-OH was modified with linker having minimal amine groups and incorporation of TA as a nuclear localization enhancer resulted in compact gene vectors with favorable safety profile and achieved high levels of transgene expression in hard to transfect human retinal pigment

  8. Generation 3 PAMAM dendrimer TAMRA conjugates containing precise dye/dendrimer ratios

    Science.gov (United States)

    Manono, Janet; Dougherty, Casey A.; Jones, Kirsten; DeMuth, Joshua; Holl, Mark M. Banaszak; DiMaggio, Stassi

    2015-01-01

    The synthesis, isolation, and characterization of generation 3 poly(amidoamine) (G3 PAMAM) dendrimer containing precise ratios of 5-carboxytetramethylrhodamine succinimidyl ester (TAMRA) dye (n = 1–3) per polymer particle are reported. Stochastic conjugation of TAMRA dye to the dendrimer was followed by separation into precise dye-polymer ratios using rp-HPLC. The isolated materials were characterized by rp-UPLC, MALDI-TOF-MS, and 1H NMR spectroscopy, UV–vis, and fluorescence spectroscopies. PMID:26549978

  9. Nanoclusters a bridge across disciplines

    CERN Document Server

    Jena, Purusottam

    2010-01-01

    This comprehensive book on Nanoclusters comprises sixteen authoritative chapters written by leading researchers in the field. It provides insight into topics that are currently at the cutting edge of cluster science, with the main focus on metal and metal compound systems that are of particular interest in materials science, and also on aspects related to biology and medicine. While there are numerous books on clusters, the focus on clusters as a bridge across disciplines sets this book apart from others. Delivers cutting edge coverage of cluster science Covers a broad range of topics in

  10. Dendrimers in Layer-by-Layer Assemblies: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Katsuhiko Sato

    2013-07-01

    Full Text Available We review the synthesis of dendrimer-containing layer-by-layer (LbL assemblies and their applications, including biosensing, controlled drug release, and bio-imaging. Dendrimers can be built into LbL films and microcapsules by alternating deposition of dendrimers and counter polymers on the surface of flat substrates and colloidal microparticles through electrostatic bonding, hydrogen bonding, covalent bonding, and biological affinity. Dendrimer-containing LbL assemblies have been used to construct biosensors, in which electron transfer mediators and metal nanoparticles are often coupled with dendrimers. Enzymes have been successfully immobilized on the surface of electrochemical and optical transducers by forming enzyme/dendrimer LbL multilayers. In this way, high-performance enzyme sensors are fabricated. In addition, dendrimer LbL films and microcapsules are useful for constructing drug delivery systems because dendrimers bind drugs to form inclusion complexes or the dendrimer surface is covalently modified with drugs. Magnetic resonance imaging of cancer cells by iron oxide nanoparticles coated with dendrimer LbL film is also discussed.

  11. Design of Dendrimer Modified Carbon Nanotubes for Gene Delivery

    Institute of Scientific and Technical Information of China (English)

    PAN Bi-feng; BAO Chen-chen; GAO Feng; HE Rong; SHU Meng-jun; MA Yong-jie; CUI Da-xiang; XU Ping; CHEN Hao; LIU Feng-tao; LI Qing; HUANG Tuo; YOU Xiao-gang; SHAO Jun

    2007-01-01

    Objective: To investigate the efficiency of polyamidoamine dendrimer grafted carbon nanotube (dendrimer-CNT) mediated entrance of anti-survivin oligonucleotide into MCF-7 cells, and its effects on the growth of MCF-7 cells. Methods: Antisense survivin oligonucleotide was anchored onto polyamidoamine dendrimer grafted carbon nanotubes to form dendrimer-CNT-asODN complex and the complex was characterized by Zeta potential, AFM, TEM, and 1% agarose gel electrophoresis analysis. Dendrimer-CNT-asODN complexes were added into the medium and incubated with MCF-7 cells. MTT method was used to detect the effects of asODN and dendrimer-CNT-asODN on the growth of MCF-7 cells. TEM was used to observe the distribution of dendrimer-CNT-asODN complex within MCF-7 cells. Results: Successful synthesis of dendrimer-CNT-asODN complexes was proved by TEM, AFM and agarose gel electrophoresis. TEM showed that the complexes were located in the cytoplasm, endosome, and lysosome within MCF-7 cells. When dendrimer-CNT-asODN (1.0 μmol/L) and asODN (1.0 μmol/L) were used for 120 h incubation, the inhibitory rates of MCF-7 cells were (28.22±3.5)% for dendrimer-CNT-asODN complex group, (9.23±0.56)% for only asODN group, and (3.44±0.25)% for dendrimer-CNT group. Dendrimer-CNT-asODN complex at 3.0 μmol/L inhibited MCF-7 cells by (30.30±10.62)%, and the inhibitory effects were in a time- and concentration- dependent manner. Conclusion: Dendrimer-CNT nanoparticles may serve as a gene delivery vector with high efficiency, which can bring foreign gene into cancer cells, inhibiting cancer cell proliferation and markedly enhancing the cancer therapy effects.

  12. Dendrimer effects on peptide and protein fibrillation

    DEFF Research Database (Denmark)

    Heegaard, Peter M. H.; Boas, Ulrik; Otzen, Daniel E.

    2007-01-01

    Dendrimers are synthetic, symmetrically branched polymers that can be manufactured to a high degree of definition and therefore present themselves as monodisperse entities. Flexible and globular in shape and compartementalized into a partly inaccessible interior and a highly exposed surface, they...

  13. Fluorescent Self-Assembled Polyphenylene Dendrimer Nanofibers

    NARCIS (Netherlands)

    Liu, Daojun; Feyter, Steven De; Cotlet, Mircea; Wiesler, Uwe-Martin; Weil, Tanja; Herrmann, Andreas; Müllen, Klaus; Schryver, Frans C. De

    2003-01-01

    A second-generation polyphenylene dendrimer 1 self-assembles into nanofibers on various substrates such as HOPG, silicon, glass, and mica from different solvents. The investigation with noncontact atomic force microscopy (NCAFM) and scanning electron microscopy (SEM) shows that the morphology of the

  14. Chemical sensors based on surface-confined dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Tokuhisa, Hideo; Crooks, R.M. [Texas A& M Univ., College Station, TX (United States). Dept. of Chemistry; Ricco, A.J.; Osbourn, G.C. [Sandia National Labs., Albuquerque, NM (United States)

    1997-10-01

    The use of dendrimers for preparing chemically sensitive interfaces for detecting volatile organic compounds (VOCs) using surface acoustic wave (SAW) device transducers is described. Specifically, the synthesis of the dendrimers and the means by which they are affixed to SAW devices is discussed, followed by a detailed spectroscopic analysis of the surface-confined dendrimers and a discussion of their interaction with different VOCs. Most of these preliminary experiments focus on dendrimer surface modification using benzoylchloride, which leads to phenyl terminal groups linked to the dendrimer via amide groups. The results of this study lead us to conclude that dendrimers: (1) provide general specificity towards classes of functional groups and are therefore suitable for array-based sensing schemes; (2) are intermediate in structure between monolayers and polymers and exhibit the desirable properties of both; (3) can be straightforwardly attached to the surfaces of acoustic wave devices.

  15. Influence of PAMAM dendrimers on the human insulin

    Science.gov (United States)

    Nowacka, Olga; Miłowska, Katarzyna; Ionov, Maksim; Bryszewska, Maria

    2015-12-01

    Dendrimers are specific class of polymeric macromolecules with wide spectrum of properties. One of the promising activities of dendrimers involves inhibition of protein fibril formation. Aggregation and fibrillation of insulin occurs in insulin-dependent diabetic patients after repeated administration, due to these processes being very easily triggered by the conditions of drug administration. The aim of this work was to study the influence of various generations PAMAM dendrimers on human insulin zeta potential, secondary structure and dithiotreitol (DTT)-induced aggregation. We observed the dependence between the number of positive charges on the surface of the PAMAM dendrimer and the values of zeta potential. Addition of dendrimers to insulin caused insignificant changes in the secondary structure. There was a small decrease in ellipticity, but it did not result in alterations in the circular dichroism (CD) spectrum shape. Dendrimers neither induced protein aggregation nor inhibited the aggregation process induced by DTT, except for 0.01 µmol/l concentration.

  16. Electrostatic theory of the assembly of PAMAM dendrimers and DNA.

    Science.gov (United States)

    Perico, Angelo

    2016-05-01

    The electrostatic interactions mediated by counterions between a cationic PAMAM dendrimer, modelized as a sphere of radius and cationic surface charge highly increasing with generation, and a DNA, modelized as an anionic elastic line, are analytically calculated in the framework of condensation theory. Under these interactions the DNA is wrapped around the sphere. For excess phosphates relative to dendrimer primary amines, the free energy of the DNA-dendrimer complex displays an absolute minimum when the complex is weakly negatively overcharged. This overcharging opposes gene delivery. For a highly positive dendrimer and a DNA fixed by experimental conditions to a number of phosphates less than the number of dendrimer primary amines, excess amine charges, the dendrimer may at the same time bind stably DNA and interact with negative cell membranes to activate cell transfection in fair agreement with molecular simulations and experiments.

  17. Electron correlations and silicon nanocluster energetics

    OpenAIRE

    2016-01-01

    The first-principle prediction of nanocluster stable structure is often hampered by the existence of many isomer configurations with energies close to the ground state. This fact attaches additional importance to many-electron effects going beyond density functional theory (DFT), because their contributions may change a subtle energy order of competitive structures. To analyze this problem, we consider, as an example, the energetics of silicon nanoclusters passivated by hydrogen Si$_{10}$H$_{...

  18. An ultrafast look at Au nanoclusters.

    Science.gov (United States)

    Yau, Sung Hei; Varnavski, Oleg; Goodson, Theodore

    2013-07-16

    In the past 20 years, researchers studying nanomaterials have uncovered many new and interesting properties not found in bulk materials. Extensive research has focused on metal nanoparticles (>3 nm) because of their potential applications, such as in molecular electronics, image markers, and catalysts. In particular, the discovery of metal nanoclusters (properties for nanomaterials are intriguing, because for metal nanosystems in this size regime both size and shape determine electronic properties. Remarkably, changes in the optical properties of nanomaterials have provided tremendous insight into the electronic structure of nanoclusters. The success of synthesizing monolayer protected clusters (MPCs) in the condensed phase has allowed scientists to probe the metal core directly. Au MPCs have become the "gold" standard in nanocluster science, thanks to the rigorous structural characterization already accomplished. The use of ultrafast laser spectroscopy on MPCs in solution provides the benefit of directly studying the chemical dynamics of metal nanoclusters (core), and their nonlinear optical properties. In this Account, we investigate the optical properties of MPCs in the visible region using ultrafast spectroscopy. Based on fluorescence up-conversion spectroscopy, we propose an emission mechanism for these nanoclusters. These clusters behave differently from nanoparticles in terms of emission lifetimes as well as two-photon cross sections. Through further investigation of the transient (excited state) absorption, we have found many unique phenomena of nanoclusters, such as quantum confinement effects and vibrational breathing modes. In summary, based on the differences in the optical properties, the distinction between nanoclusters and nanoparticles appears at a size near 2.2 nm. This is consistent with simulations from a free-electron model proposed for MPCs. The use of ultrafast techniques on these nanoclusters can answer many of the fundamental questions about

  19. Synthesis and Spectral Studies of CdTe–Dendrimer Conjugates

    OpenAIRE

    Ghosh Srabanti; Saha Abhijit

    2009-01-01

    Abstract In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH2-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decr...

  20. Enhanced Bioactivity of Internally Functionalized Cationic Dendrimers with PEG Cores

    Science.gov (United States)

    2012-11-09

    precipitation or dialysis as the only means of purification , greatly simplifying the synthetic process. Dendrimer−Cell Interactions. Previous studies...synthesis of dendrimers is still considered to be a time-consuming process requiring rigorous purification processes.14 Furthermore, partial...for the divergent synthesis of dendrimers.16−18 These strategies rely on the solubility of the PEG core to simplify purification of the PEG-dendrimer

  1. A nanocluster beacon based on the template transformation of DNA-templated silver nanoclusters.

    Science.gov (United States)

    Teng, Ye; Jia, Xiaofang; Zhang, Shan; Zhu, Jinbo; Wang, Erkang

    2016-01-28

    In this work, we developed a novel light-up nanocluster beacon (NCB) based on shuttling dark silver nanoclusters (NCs) to a bright scaffold through hybridization. The fluorescence enhancement was as high as 70-fold when the two templates were on the opposite sides of the duplexes, enabling sensitive and selective detection of DNA.

  2. Alternating deposition films of a polymer and dendrimers bearing diphenylanthracene

    Institute of Scientific and Technical Information of China (English)

    SUN Jing; WANG Liyan; GAO Jian; YU Xi; WANG Zhiqiang

    2005-01-01

    Two generations of carboxyl-terminated poly (aryl ether) dendrimers bearing 9,10-diphenylanthracene cores are designed and synthesized. Alternating deposition of two dendrimers and poly(4-vinylpyridine) is studied with UV-Vis spectroscopy, FT-IR spectroscopy and atomic force microscopy. Experimental results indicate that this method to introduce chromophore into multilayer film can effectively prevent desorption of dye molecule. Moreover, it is found that dendrimer can inhibit the aggregation of fluorophore in film using fluorescence spectroscopy. Increase of dendrimer's generation can enhance fluorescence intensity of each fluorophore. This provides a new approach to design luminescent thin film.

  3. In vivo toxicity of poly(propyleneimine) dendrimers.

    Science.gov (United States)

    Ziemba, Barbara; Janaszewska, Anna; Ciepluch, Karol; Krotewicz, Maria; Fogel, Wiesława A; Appelhans, Dietmar; Voit, Brigitte; Bryszewska, Maria; Klajnert, Barbara

    2011-11-01

    Dendrimers are highly branched macromolecules with the potential to be used for biomedical applications. Several dendrimers are toxic owing to their positively charged surfaces. However, this toxicity can be reduced by coating these peripheral cationic groups with carbohydrate residues. In this study, the toxicity of three types of 4th generation poly (propyleneimine) dendrimers were investigated in vivo; uncoated (PPI-g4) dendrimers, and dendrimers in which 25% or 100% of surface amino groups were coated with maltotriose (PPI-g4-25%m or PPI-g4-100%m), were administered to Wistar rats. Body weight, food and water consumption, and urine excretion were monitored daily. Blood was collected to investigate biochemical and hematological parameters, and the general condition and behavior of the animals were analyzed. Unmodified PPI dendrimers caused changes in the behavior of rats, a decrease in food and water consumption, and lower body weight gain. In the case of PPI-g4 and PPI-g4-25%m dendrimers, disturbances in urine and hematological and biochemical profiles returned to normal during the recovery period. PPI-g4-100%m was harmless to rats. The PPI dendrimers demonstrated dose- and sugar-modification-degree dependent toxicity. A higher dose of uncoated PPI dendrimers caused toxicity, but surface modification almost completely abolished this toxic effect.

  4. Cationic PAMAM dendrimers aggressively initiate blood clot formation.

    Science.gov (United States)

    Jones, Clinton F; Campbell, Robert A; Brooks, Amanda E; Assemi, Shoeleh; Tadjiki, Soheyl; Thiagarajan, Giridhar; Mulcock, Cheyanne; Weyrich, Andrew S; Brooks, Benjamin D; Ghandehari, Hamidreza; Grainger, David W

    2012-11-27

    Poly(amidoamine) (PAMAM) dendrimers are increasingly studied as model nanoparticles for a variety of biomedical applications, notably in systemic administrations. However, with respect to blood-contacting applications, amine-terminated dendrimers have recently been shown to activate platelets and cause a fatal, disseminated intravascular coagulation (DIC)-like condition in mice and rats. We here demonstrate that, upon addition to blood, cationic G7 PAMAM dendrimers induce fibrinogen aggregation, which may contribute to the in vivo DIC-like phenomenon. We demonstrate that amine-terminated dendrimers act directly on fibrinogen in a thrombin-independent manner to generate dense, high-molecular-weight fibrinogen aggregates with minimal fibrin fibril formation. In addition, we hypothesize this clot-like behavior is likely mediated by electrostatic interactions between the densely charged cationic dendrimer surface and negatively charged fibrinogen domains. Interestingly, cationic dendrimers also induced aggregation of albumin, suggesting that many negatively charged blood proteins may be affected by cationic dendrimers. To investigate this further, zebrafish embryos were employed to more specifically determine the speed of this phenomenon and the pathway- and dose-dependency of the resulting vascular occlusion phenotype. These novel findings show that G7 PAMAM dendrimers significantly and adversely impact many blood components to produce rapid coagulation and strongly suggest that these effects are independent of classic coagulation mechanisms. These results also strongly suggest the need to fully characterize amine-terminated PAMAM dendrimers in regard to their adverse effects on both coagulation and platelets, which may contribute to blood toxicity.

  5. Atomically Precise Metal Nanoclusters for Catalytic Application

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Rongchao [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-11-18

    The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily high selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au25(SR)18, Au28(SR)20, Au38(SR)24, Au99(SR)42, Au144(SR)60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our

  6. Trapping in dendrimers and regular hyperbranched polymers

    CERN Document Server

    Wu, Bin; Zhang, Zhongzhi; Chen, Guanrong

    2012-01-01

    Dendrimers and regular hyperbranched polymers are two classic families of macromolecules, which can be modeled by Cayley trees and Vicsek fractals, respectively. In this paper, we study the trapping problem in Cayley trees and Vicsek fractals with different underlying geometries, focusing on a particular case with a perfect trap located at the central node. For both networks, we derive the exact analytic formulas in terms of the network size for the average trapping time (ATT)---the average of node-to-trap mean first-passage time over the whole networks. The obtained closed-form solutions show that for both Cayley trees and Vicsek fractals, the ATT display quite different scalings with various system sizes, which implies that the underlying structure plays a key role on the efficiency of trapping in polymer networks. Moreover, the dissimilar scalings of ATT may allow to differentiate readily between dendrimers and hyperbranched polymers.

  7. IMMUNOSTIMULATORY PROPERTIES OF DENDRIMERS MULTIVALENTLY PRESENTING MURAMYLDIPEPTIDE

    DEFF Research Database (Denmark)

    Objectives: Many pathogens will only be efficiently neutralized by the induction of cell-mediated immunity, and with the enhanced use of subunit-vaccine approaches there is a strong need for the development of efficient and safe Th1-biassing adjuvants. Pathogen-associated molecular patterns (PAMP...... to employ dendrimers in the synthesis of molecularly defined globular PAMP-mimics or “artificial microbes” with controlled immunostimulatory properties....

  8. [Advancement of research on polyamidoamine dendrimers].

    Science.gov (United States)

    Xu, Jing; Zhang, Longzhen

    2012-10-01

    Polyamidoamine (PAMAM) dendrimers is synthesized by the American scientist, Tomalia, in 1985 and is now used widely in many fields such as gene carriers, photoelectric sensor, wastewater treatment, drug carriers and catalyst. The present paper mainly reviews the structure and methods of synthesis, celluar cytotoxicity, achievements of gene and drug carriers research, advancement and prospect of PAMAM as a carrier in glioma therapy. Besides, it also involves an outline for the future research of the radiotherapy for glioma.

  9. Synthesis of Novel Carbosilane Dendrimers with Myo-inositol Cores

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The preparation of carbosilane dendrimers with cores of myo-inositol and the outmost periphery groups of allyl groups has been reported.By using alternate hydrosilylation and alkenylation reactions, the dendrimer have been carried up to the third generation with 48 allyl groups on the periphery.

  10. Wiring of heme enzymes by methylene-blue labeled dendrimers

    DEFF Research Database (Denmark)

    Álvarez-Martos, Isabel; Shahdost-fard, Faezeh; Ferapontova, Elena

    2017-01-01

    - and molibdopterin-containing sulfite oxidase (SOx), wired to gold by the methylene blue (MB)-labeled polyamidoamine (PAMAM) dendrimers. The enzymes’ electrochemical transformation and bioelectrocatalytic function could be followed at both unlabeled and MB-labeled dendrimer-modified electrodes with the formal redox...

  11. Periphery-Functionalized Organometallic Dendrimers for Homogeneous Catalysis

    NARCIS (Netherlands)

    Koten, G. van; Jastrzebski, J.T.B.H.

    1999-01-01

    The use of carbosilane based dendrimers as molecular scaffolds for the attachment of organomettallic Ni 'pincer' complexes that are active as a catalyst in the Kharasch addition reaction is described. It is shown that increasing steric crowding at the dendrimer periphery results in decreased catalys

  12. Surface-Induced Melting of Metal Nanoclusters

    Institute of Scientific and Technical Information of China (English)

    YANG Quan-Wen; ZHU Ru-Zeng; WEI Jiu-An; WEN Yu-Hua

    2004-01-01

    @@ We investigate the size effect on melting of metal nanoclusters by molecular dynamics simulation and thermodynamic theory based on Kofman's melt model. By the minimization of the free energy of metal nanoclusters with respect to the thickness of the surface liquid layer, it has been found that the nanoclusters of the same metal have the same premelting temperature Tpre = T0 - T0(γsv -γlv -γst)/(ρLξ) (T0 is the melting point of bulk metal, γsv the solid-vapour interfacial free energy, γlv the liquid-vapour interfacial free energy, γsl the solid-liquid interfacial free energy, ρ the density of metal, L the latent heat of bulk metal, and ξ the characteristic length of surface-interface interaction) to be independent of the size of nanoclusters, so that the characteristic length ξ ofa metal can be obtained easily by Tpre, which can be obtained by experiments or molecular dynamics (MD) simulations. The premelting temperature Tpre of Cu is obtained by MD simulations, then ξ is obtained.The melting point Tcm is further predicted by free energy analysis and is in good agreement with the result of our MD simulations. We also predict the maximum premelting-liquid width of Cu nanoclusters with various sizes and the critical size, below which there is no premelting.

  13. Synthesis and Spectral Studies of CdTe–Dendrimer Conjugates

    Directory of Open Access Journals (Sweden)

    Ghosh Srabanti

    2009-01-01

    Full Text Available Abstract In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH2-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decrease in luminescence intensity of CdTe quantum dots owing to noncovalent binding with dendrimer limits further utilization of these nanoassemblies. Hence, an attempt is made, for the first time, to synthesize stable, highly luminescent, covalently linked CdTe–Dendrimer conjugate in aqueous medium using glutaric dialdehyde (G linker. Conjugate has been characterized through Fourier transform infrared spectroscopy and transmission electron microscopy. In this strategy, photoluminescence quantum efficiency of CdTe quantum dots with narrow emission bandwidths remained unaffected after formation of the conjugate.

  14. Synthesis and Spectral Studies of CdTe-Dendrimer Conjugates

    Science.gov (United States)

    Ghosh, Srabanti; Saha, Abhijit

    2009-08-01

    In order to couple high cellular uptake and target specificity of dendrimer molecule with excellent optical properties of semiconductor nanoparticles, the interaction of cysteine-capped CdTe quantum dots with dendrimer was investigated through spectroscopic techniques. NH2-terminated dendrimer molecule quenched the photoluminescence of CdTe quantum dots. The binding constants and binding capacity were calculated, and the nature of binding was found to be noncovalent. Significant decrease in luminescence intensity of CdTe quantum dots owing to noncovalent binding with dendrimer limits further utilization of these nanoassemblies. Hence, an attempt is made, for the first time, to synthesize stable, highly luminescent, covalently linked CdTe-Dendrimer conjugate in aqueous medium using glutaric dialdehyde (G) linker. Conjugate has been characterized through Fourier transform infrared spectroscopy and transmission electron microscopy. In this strategy, photoluminescence quantum efficiency of CdTe quantum dots with narrow emission bandwidths remained unaffected after formation of the conjugate.

  15. Characterization of crystalline dendrimer-stabilized gold nanoparticles

    Science.gov (United States)

    Shi, Xiangyang; Ganser, T. Rose; Sun, Kai; Balogh, Lajos P.; Baker, James R., Jr.

    2006-02-01

    Monodispersed, highly crystalline dendrimer-stabilized gold nanoparticles (Au DSNPs) were synthesized via hydrazine reduction chemistry and stabilized using primary amine-terminated poly(amidoamine) (PAMAM) dendrimers of different generations (generations 2-6) with the same molar ratios of dendrimer terminal nitrogen ligands/gold atoms. The sizes of the synthesized Au DSNPs decrease with the increase of the number of dendrimer generations. These Au DSNPs are fluorescent and display strong blue emission intensity at 458 nm. Polyacrylamide gel electrophoresis (PAGE) analysis indicates that all Au DSNPs are stable and both metal NPs and dendrimer stabilizers do not separate from each other during the electrophoresis process. The synthesized inorganic/organic hybrid Au DSNPs provide new nanoplatforms that will be further modified with various biological ligands for the application of biosensing and targeted cancer therapeutics.

  16. Dendrimer D5 is a vector for peptide transport to brain cells.

    Science.gov (United States)

    Sarantseva, S V; Bolshakova, O I; Timoshenko, S I; Kolobov, A A; Schwarzman, A L

    2011-02-01

    Dendrimers are a new class of nonviral vectors for gene or drug transport. Dendrimer capacity to penetrate through the blood-brain barrier remaines little studied. Biotinylated polylysine dendrimer D5, similarly to human growth hormone biotinylated fragment covalently bound to D5 dendrimer, penetrates through the blood-brain barrier and accumulates in Drosophila brain after injection into the abdomen. Hence, D5 dendrimer can serve as a vector for peptide transport to brain cells.

  17. Investigation of the interaction of polyamidoamine dendrimers with nicotinic acid as solubility enhancer

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Objective Polyamidoamine(PAMAM) dendrimers enhance the solubility of nicotinic acid. Methods PAMAM dendrimers of generation 1 to 6 were prepared and the effect of pH and concentration of the dendrimers on the solubility enhancement of nicotinic acid was investigated. Results The pH and concentration of the dendrimers influence the solubility enhancement of nicotinic acid. Conclusions Electrostatic interaction between the carboxyl group of the nicotinic acid and the amine groups of the dendrimers is involved.

  18. Plasmon tsunamis on metallic nanoclusters.

    Science.gov (United States)

    Lucas, A A; Sunjic, M

    2012-03-14

    A model is constructed to describe inelastic scattering events accompanying electron capture by a highly charged ion flying by a metallic nanosphere. The electronic energy liberated by an electron leaving the Fermi level of the metal and dropping into a deep Rydberg state of the ion is used to increase the ion kinetic energy and, simultaneously, to excite multiple surface plasmons around the positively charged hole left behind on the metal sphere. This tsunami-like phenomenon manifests itself as periodic oscillations in the kinetic energy gain spectrum of the ion. The theory developed here extends our previous treatment (Lucas et al 2011 New J. Phys. 13 013034) of the Ar(q+)/C(60) charge exchange system. We provide an analysis of how the individual multipolar surface plasmons of the metallic sphere contribute to the formation of the oscillatory gain spectrum. Gain spectra showing characteristic, tsunami-like oscillations are simulated for Ar(15+) ions capturing one electron in distant collisions with Al and Na nanoclusters.

  19. Fluorescent DNA Stabilized Silver Nanoclusters as Biosensors

    Directory of Open Access Journals (Sweden)

    Alfonso Latorre

    2013-01-01

    Full Text Available DNA stabilized fluorescent silver nanoclusters are promising materials, of which fluorescent properties can be exploited to develop sensors. Particularly, the presence of a DNA strand in the structure has promoted the development of gene sensors where one part of the sensor is able to recognize the target gene sequence. Moreover, since oligonucleotides can be designed to have binding properties (aptamers a variety of sensors for proteins and cells have been developed using silver nanoclusters. In this review the applications of this material as sensors of different biomolecules are summarized.

  20. Chirality in Bare and Passivated Gold Nanoclusters

    CERN Document Server

    Garzon, I L; Rodrigues-Hernandez, J I; Sigal, I; Beltran, M R; Michaelian, K

    2002-01-01

    Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$ and Au$_{38}$(SCH$_{3}$)$_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.

  1. Surface mediated assembly of small, metastable gold nanoclusters

    Science.gov (United States)

    Pettibone, John M.; Osborn, William A.; Rykaczewski, Konrad; Talin, A. Alec; Bonevich, John E.; Hudgens, Jeffrey W.; Allendorf, Mark D.

    2013-06-01

    The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The

  2. Silver nanoclusters emitting weak NIR fluorescence biomineralized by BSA

    Science.gov (United States)

    Li, Baoshun; Li, Jianjun; Zhao, Junwu

    2015-01-01

    Noble metal (e.g., gold and silver) nanomaterials possess unique physical and chemical properties. In present work, silver nanoclusters (also known as silver quantum clusters or silver quantum dots) were synthesized by bovine serum albumin (BSA) biomineralization. The synthesized silver nanoclusters were characterized by UV-VIS absorption spectroscopy, fluorescence spectroscopy, upconversion emission spectroscopy, TEM, HRTEM and FTIR spectroscopy. TEM results showed that the average size of the silver nanoclusters was 2.23 nm. Fluorescence results showed that these silver nanoclusters could emit weak near-infrared (NIR) fluorescence (the central emission wavelength being about 765 nm). And the central excitation wavelength was about 395 nm, in the UV spectral region. These silver nanoclusters showed an extraordinarily large gap (about 370 nm) between the central excitation wavelength and central emission wavelength. In addition, it was found that these silver nanoclusters possess upconversion emission property. Upconversion emission results showed that the upconversion emission spectrum of the silver nanoclusters agreed well with their normal fluorescence emission spectrum. The synthesized silver nanoclusters showed high stability in aqueous solution and it was considered that they might be confined in BSA molecules. It was found that silver nanoclusters might enhance and broaden the absorption of proteins, and the protein absorption peak showed an obvious red shift (being 7 nm) after the formation of silver nanoclusters.

  3. Photochromism of 36-Armed Liquid Crystalline Dendrimer

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The photochromism of a 36-armed liquid crystalline dendrimer D6 was briefly described in this paper. The molar absorption coefficient, photoisomerization and photo back-isomerization of D6 in solution were investigated by UV/Vis absorption spectra. The results indicate that the photochromism and photo back-isomerization of D6 in chloroform (CHCl3) and tetrahydrofuran (THF) solutions are in accordance with the first order kinetics. The photochromism rate constants of D6 are 10-1 s-1, it is 107 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties.

  4. IMMUNOSTIMULATORY PROPERTIES OF DENDRIMERS MULTIVALENTLY PRESENTING MURAMYLDIPEPTIDE

    DEFF Research Database (Denmark)

    a theoretical number of 16 and 32 MDP molecules, respectively. These conjugates were tested for cytotoxicity, and for their ability to induce cytokines and upregulate MHC and costimulatory molecules in porcine peripheral blood mononuclear cells. Results: Both MDP-PPI and MDP-PAMAM conjugates induced...... an upregulation of B7 and MHC class II after 24 hours of culture in medium. However, after culture with PGN or MDP-conjugated dendrimers, the monocytes had down-regulated both markers to a degree that corresponded with the magnitude of cytokine production. Conclusion: These results indicate that it is possible...

  5. The Nanocluster Trap endstation at BESSY II

    Directory of Open Access Journals (Sweden)

    Tobias Lau

    2017-05-01

    Full Text Available The Nanocluster Trap endstation at BESSY II combines a cryogenic linear radio-frequency ion trap with an applied magnetic field for x-ray magnetic circular dichroism studies of cold and size-selected trapped ions. Applications include atomic, molecular, and cluster ions as well as ionic complexes.

  6. Exciton migration and quenching in poly(propylene imine) dendrimers

    Science.gov (United States)

    Minevičiūtė, I.; Gulbinas, V.; Franckevičius, M.; Vaišnoras, R.; Marcos, M.; Serrano, J. L.

    2009-05-01

    Exciton migration between chromophore groups of the poly(propylene imine) dendrimer in chloroform solution and in solid state has been investigated by means of the time-resolved fluorescence measurements. Fluorescence decay kinetics, dynamic band shift and the depolarization rate have been analyzed. Exciton migration in a single dendrimer was found to be slow in comparison with temperature-dependent chromophore reorientation time of 150-600 ps. In a solid state chromophore groups form collective excitonic states responsible for the dendrimer film fluorescence. Exciton migration and localization to the lowest energy sites within the distributed density of states take place on a subnanosecond-nanosecond time scale.

  7. Dendrimers - from organic synthesis to pharmaceutical applications: an update.

    Science.gov (United States)

    Kalhapure, Rahul S; Kathiravan, Muthu K; Akamanchi, Krishnacharya G; Govender, Thirumala

    2015-01-01

    Dendrimers are a relatively new class of monodisperse polymers, which have tree-like spherical structures with well-defined sizes and shapes. Their unique structure has a significant impact on their physical and chemical properties. Research on dendrimers is of significant interest to scientists from all areas and their utility in various scientific fields, including pharmaceuticals, is expanding. The present review is comprehensive and covers different aspects of dendrimers viz. (1) synthesis, (2) properties and (3) pharmaceutical applications. The emphasis is on their applications as well as the current ongoing research status for drug targeting.

  8. The effect of dendrimer on cotton dyeability with direct dyes

    Directory of Open Access Journals (Sweden)

    Khakzar Bafrooei F.

    2014-01-01

    Full Text Available Pretreatment of cotton fabric with poly(propylene imine dendrimer enhanced its colour strength using C.I. Direct Red 81 and C.I. Direct Blue 78. Application of this dendrimer and the direct dye simultaneously on cotton fabric by the exhaust and the continuous dyeing method were studied; slight improvements in the dyeing results were obtained. Pretreatment of the cotton fabric with dendrimer in an emulsion form using the pad-dry method followed by continuous dyeing markedly increased the colour strength. In addition, level dyeing was obtained, and no negative effects on the fastness properties of the dyes used were observed.

  9. Continuous-time quantum walks on multilayer dendrimer networks

    Science.gov (United States)

    Galiceanu, Mircea; Strunz, Walter T.

    2016-08-01

    We consider continuous-time quantum walks (CTQWs) on multilayer dendrimer networks (MDs) and their application to quantum transport. A detailed study of properties of CTQWs is presented and transport efficiency is determined in terms of the exact and average return probabilities. The latter depends only on the eigenvalues of the connectivity matrix, which even for very large structures allows a complete analytical solution for this particular choice of network. In the case of MDs we observe an interplay between strong localization effects, due to the dendrimer topology, and good efficiency from the linear segments. We show that quantum transport is enhanced by interconnecting more layers of dendrimers.

  10. Magnetic Ordering in Gold Nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Agrachev, Mikhail; Antonello, Sabrina; Dainese, Tiziano; Ruzzi, Marco; Zoleo, Alfonso; Aprà, Edoardo; Govind, Niranjan; Fortunelli, Alessandro; Sementa, Luca; Maran, Flavio

    2017-06-12

    Several research groups have observed magnetism in monolayer-protected gold-cluster samples, but the results were often contradictory and thus a clear understanding of this phenomenon is still missing. We used Au25(SCH2CH2Ph)180, which is a paramagnetic cluster that can be prepared with atomic precision and whose structure is known precisely. Previous magnetometry studies only detected paramagnetism. We used samples representing a range of crystallographic orders and studied their magnetic behaviors by electron paramagnetic resonance (EPR). As a film, Au25(SCH2CH2Ph)180 displays paramagnetic behavior but, at low temperature, ferromagnetic interactions are detectable. One or few single crystals undergo physical reorientation with the applied field and display ferromagnetism, as detected through hysteresis experiments. A large collection of microcrystals is magnetic even at room temperature and shows distinct paramagnetic, superparamagnetic, and ferromagnetic behaviors. Simulation of the EPR spectra shows that both spin-orbit coupling and crystal distortion are important to determine the observed magnetic behaviors. DFT calculations carried out on single cluster and periodic models predict values of spin6orbit coupling and crystal6splitting effects in agreement with the EPR derived quantities. Magnetism in gold nanoclusters is thus demonstrated to be the outcome of a very delicate balance of factors. To obtain reproducible results, the samples must be (i) controlled for composition and thus be monodispersed with atomic precision, (ii) of known charge state, and (iii) well defined also in terms of crystallinity and experimental conditions. This study highlights the efficacy of EPR spectroscopy to provide a molecular understanding of these phenomena

  11. Design of interior-functionalized fully acetylated dendrimers for anticancer drug delivery.

    Science.gov (United States)

    Hu, Jingjing; Su, Yunzhang; Zhang, Hongfeng; Xu, Tongwen; Cheng, Yiyun

    2011-12-01

    In this study, dendrimers was synthesized by introducing functional groups into the interior pockets of fully acetylated dendrimers. NMR techniques including COSY and 2D-NOESY revealed the molecular structures of the synthesized dendrimers and the encapsulation of guest molecule such as methotrexate within their interior pockets. The synthesized polymeric nanocarriers showed much lower cytotoxicity on two cell lines than cationic dendrimers, and exhibited better performance than fully acetylated dendrimers in the sustained release of methotrexate. The results provided a new strategy in the design of non-toxic dendrimers with high performance in the delivery of anti-cancer drugs for clinical applications.

  12. From dendrimers to fractal polymers and beyond

    Directory of Open Access Journals (Sweden)

    Charles N. Moorefield

    2013-01-01

    Full Text Available The advent of dendritic chemistry has facilitated materials research by allowing precise control of functional component placement in macromolecular architecture. The iterative synthetic protocols used for dendrimer construction were developed based on the desire to craft highly branched, high molecular weight, molecules with exact mass and tailored functionality. Arborols, inspired by trees and precursors of the utilitarian macromolecules known as dendrimers today, were the first examples to employ predesigned, 1 → 3 C-branched, building blocks; physical characteristics of the arborols, including their globular shapes, excellent solubilities, and demonstrated aggregation, combined to reveal the inherent supramolecular potential (e.g., the unimolecular micelle of these unique species. The architecture that is a characteristic of dendritic materials also exhibits fractal qualities based on self-similar, repetitive, branched frameworks. Thus, the fractal design and supramolecular aspects of these constructs are suggestive of a larger field of fractal materials that incorporates repeating geometries and are derived by complementary building block recognition and assembly. Use of terpyridine-M2+-terpyridine (where, M = Ru, Zn, Fe, etc connectivity in concert with mathematical algorithms, such as forms the basis for the Seirpinski gasket, has allowed the beginning exploration of fractal materials construction. The propensity of the fractal molecules to self-assemble into higher order architectures adds another dimension to this new arena of materials and composite construction.

  13. Thermodynamic stability of ligand-protected metal nanoclusters

    Science.gov (United States)

    Taylor, Michael G.; Mpourmpakis, Giannis

    2017-01-01

    Despite the great advances in synthesis and structural determination of atomically precise, thiolate-protected metal nanoclusters, our understanding of the driving forces for their colloidal stabilization is very limited. Currently there is a lack of models able to describe the thermodynamic stability of these ‘magic-number’ colloidal nanoclusters as a function of their atomic-level structural characteristics. Herein, we introduce the thermodynamic stability theory, derived from first principles, which is able to address stability of thiolate-protected metal nanoclusters as a function of the number of metal core atoms and thiolates on the nanocluster shell. Surprisingly, we reveal a fine energy balance between the core cohesive energy and the shell-to-core binding energy that appears to drive nanocluster stabilization. Our theory applies to both charged and neutral systems and captures a large number of experimental observations. Importantly, it opens new avenues for accelerating the discovery of stable, atomically precise, colloidal metal nanoclusters. PMID:28685777

  14. Metal/Metal-Oxide Nanoclusters for Gas Sensor Applications

    Directory of Open Access Journals (Sweden)

    Ahmad I. Ayesh

    2016-01-01

    Full Text Available The development of gas sensors that are based on metal/metal-oxide nanoclusters has attracted intensive research interest in the last years. Nanoclusters are suitable candidates for gas sensor applications because of their large surface-to-volume ratio that can be utilized for selective and rapid detection of various gaseous species with low-power consuming electronics. Herein, nanoclusters are used as building blocks for the construction of gas sensor where the electrical conductivity of the nanoclusters changes dramatically upon exposure to the target gas. In this review, recent progress in the fabrication of size-selected metallic nanoclusters and their utilization for gas sensor applications is presented. Special focus will be given to the enhancement of the sensing performance through the rational functionalization and utilization of different nanocluster materials.

  15. Thermodynamic stability of ligand-protected metal nanoclusters

    Science.gov (United States)

    Taylor, Michael G.; Mpourmpakis, Giannis

    2017-07-01

    Despite the great advances in synthesis and structural determination of atomically precise, thiolate-protected metal nanoclusters, our understanding of the driving forces for their colloidal stabilization is very limited. Currently there is a lack of models able to describe the thermodynamic stability of these `magic-number' colloidal nanoclusters as a function of their atomic-level structural characteristics. Herein, we introduce the thermodynamic stability theory, derived from first principles, which is able to address stability of thiolate-protected metal nanoclusters as a function of the number of metal core atoms and thiolates on the nanocluster shell. Surprisingly, we reveal a fine energy balance between the core cohesive energy and the shell-to-core binding energy that appears to drive nanocluster stabilization. Our theory applies to both charged and neutral systems and captures a large number of experimental observations. Importantly, it opens new avenues for accelerating the discovery of stable, atomically precise, colloidal metal nanoclusters.

  16. Metal/Metal-Oxide Nanoclusters for Gas Sensor Applications

    OpenAIRE

    Ayesh, Ahmad I.

    2016-01-01

    The development of gas sensors that are based on metal/metal-oxide nanoclusters has attracted intensive research interest in the last years. Nanoclusters are suitable candidates for gas sensor applications because of their large surface-to-volume ratio that can be utilized for selective and rapid detection of various gaseous species with low-power consuming electronics. Herein, nanoclusters are used as building blocks for the construction of gas sensor where the electrical conductivity of the...

  17. Dendrimer-entrapped metal colloids as imaging agents.

    Science.gov (United States)

    Li, Du; Wen, Shihui; Shi, Xiangyang

    2015-01-01

    This review reports the recent advances in dendrimer-entrapped metal colloids as contrast agents for biomedical imaging applications. The versatile dendrimer scaffolds with 3-dimensional spherical shape, highly branched internal cavity, tunable surface conjugation chemistry, and excellent biocompatibility and nonimmunogenicity afford their uses as templates to create multifunctional dendrimer-entrapped metal colloids for mono- or multi- mode molecular imaging applications. In particular, multifunctional dendrimer-entrapped gold nanoparticles with different surface modifications have been used for fluorescence imaging, targeted tumor computed tomography (CT) imaging, enhanced blood pool CT imaging, dual mode CT/MR imaging, and tumor theranostics (combined CT imaging and chemotherapy) will be introduced and discussed in detail. © 2015 Wiley Periodicals, Inc.

  18. Thermodynamic properties of a liquid crystal carbosilane dendrimer

    Science.gov (United States)

    Samosudova, Ya. S.; Markin, A. V.; Smirnova, N. N.; Ogurtsov, T. G.; Boiko, N. I.; Shibaev, V. P.

    2016-11-01

    The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6-370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C p ° ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) are calculated from the obtained experimental data for the region of T → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at T = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.

  19. An emerging class of amphiphilic dendrimers for pharmaceutical and biomedical applications: Janus amphiphilic dendrimers.

    Science.gov (United States)

    Sikwal, Dhiraj R; Kalhapure, Rahul S; Govender, Thirumala

    2017-01-15

    In recent years, a new class of dendrimer, known as Janus dendrimers (JDs), has attracted much attention due to their different structures and properties to the conventional symmetric forms. The broken symmetry of JDs offers the opportunity to form complex self-assembled materials, and presents new sets of properties that are presently inconceivable for homogeneous or symmetrical dendrimers. Due to their unique features, JDs have a promising future in pharmaceutical and biomedical fields, as seen from the recent interest in their application in conjugating multiple drugs and targeting moieties, forming supramolecular hydrogels, enabling micellar delivery systems, and preparing nano-vesicles, known as dendrimersomes, for drug encapsulation. The present paper is the first review, with an emphasis on various emerging applications of JDs, in the drug delivery and biomedical field reported so far. In addition, the paper describes different synthetic methods for producing JDs that can guide the design of new biocompatible forms with pharmacological activities, and that have the potential to be nano drug delivery vehicles. Furthermore, future studies to optimize the applications of JDs in drug delivery sciences and biomedical field to realize their potential to treat various disease conditions are identified and highlighted. Overall, this review identifies the current status of JDs in terms of their synthesis and applications, as well as the future research for their translation into macromolecules for clinical applications to solve health problems. It highlights the future combined efforts needed to be taken by dendrimer chemists, formulation scientist and microbiologists to develop novel antibacterials and nanomedicines from JDs. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Synthesis of Dendrimer Containing Carbazole Unit as a Core Chromophore

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Choul; Lee, Jae Wook [Dong-A Univ., Busan (Korea, Republic of); Jin, Sungho [Pusan National Univ., Busan (Korea, Republic of)

    2012-10-15

    Dendrimers, which are prepared by repetition of a given set of reactions using either divergent or convergent strategies, are highly branched and regular macromolecules with well-defined structures and have served as functional objects in nanotechnology and nano-materials science. Following conventional organic small molecules and polymers, dendrimers are now regarded as the third class of materials for use in organic light-emitting diodes (OLEDs) and have attracted much attention due to their distinguished properties. Dendrimers contain three distinct structural parts that are the core, end-groups, and branched units connecting core and periphery. For light-emitting dendrimers, the core is usually selected as the luminescent chromophore, and the dendrons and their periphery are charge transporting units and can also tune the solubility. In contrast to linear polymers, dendrimers are sphere-like with dimensions of the order of nanometers depending on the generation number. By careful structural design, dendrimers combine the potential advantages of both small molecules and polymers. Therefore, the innovative strategy different from conventional convergent and divergent routes has been required to simplify dendrimer synthesis. Recent solid chemistry is the click chemistry which is the copper-catalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide developed by Sharpless and Tornφe. This reaction has many advantages: very high yields, mild and simple reaction conditions, oxygen and water tolerance, and easy isolation of product. This reaction is clearly a breakthrough in the synthesis of dendrimers and dendritic and polymer materials. We have developed the fusion and stitching methods for the synthesis of various dendrimers using click chemistry between an alkyne and an azide. Overall, this method was found to be a straightforward strategy for the synthesis of triazole-based dendrimers. Taking advantage of this fact, herein we report a feasible route

  1. Conformational Analysis of Triazine Dendrimers: Using NMR Spectroscopy To Probe the Choreography of a Dendrimer's Dance.

    Science.gov (United States)

    Moreno, Karlos X; Simanek, Eric E

    2008-06-24

    One-dimensional (1D) and two-dimensional (2D) NMR studies are used to probe the conformation of a melamine dendrimer bearing unique NMR signals from the core to the periphery. Four conceptual anchors for dendrimer conformation emerge from these experiments. First, changes in isomer populations observed by (1)H NMR reveal the onset of globular structure. Second, NOE complexity emerges with globular structure: variable temperature NOESY studies show that the peripheral groups, BOC-protected aliphatic amines, fold back into the globular core of the macromolecule at 75 degrees C in DMSO-d(6). Third, variable temperature coefficients measured for NH protons suggest that solvent is largely excluded from the interior of the dendrimer: the carbamate NH groups of the periphery are most sensitive to temperature while the NHs nearest the core show little temperature dependence. Conformation is influenced by solvent choice: backfolding is observed in DMSO-d(6), but not in either CDCl(3) or CD(3)OD. Finally, relaxation studies show that peripheral groups are more dynamic than groups at the core. These anchors consolidate observations made by many groups on disparate systems within a common architecture.

  2. Carbosilane dendrimers bearing globotriaoses: syntheses of globotrioasyl derivative and introduction into carbosilane dendrimers.

    Science.gov (United States)

    Matsuoka, Koji; Terabatake, Mikiko; Umino, Atsushi; Esumi, Yasuaki; Hatano, Ken; Terunuma, Daiyo; Kuzuhara, Hiroyoshi

    2006-08-01

    As an application of a one-pot reaction involving Birch reduction and subsequent S(N)2 reaction in liquid ammonia, synthetic assembly of trisaccharidic moieties of globotriaosyl ceramide onto carbosilane dendrimers was accomplished using tris(3-bromopropyl)phenylsilane and tris[tris(3-bromopropyl)silylpropyl]phenylsilane as the core scaffolds. The common globotriaosyl derivative having benzylsulfide functionality at the terminal of the aglycon was efficiently prepared from d-galactose and d-lactose as starting materials. The glycosyl donor derived from galactose and the glycosyl acceptor derived from lactose were condensed in the presence of silver triflate as the best promoter to provide corresponding trisaccharide with newly formed alpha-1-4 linkages in 90% yield. Fully benzylated protection of the trisaccharide was deprotected under the Birch reduction condition followed by acetylation to give an acetate in which alkene was converted into benzyl sulfide by radical addition of alpha-toluenethiol in high yields. On the other hand, carbosilane dendrimers were prepared from appropriate chlorosilanes as starting materials by a combination of hydrosylation followed by alkenylation. The terminal C=C double bonds of the carbosilanes were converted into corresponding alcohols by means of the usual hydroboration reaction, and the alcohols underwent further chemical manipulation to give carbosilane dendrimers with peripheral bromine atoms.

  3. Dendrimers in drug delivery and targeting: Drug-dendrimer interactions and toxicity issues

    Directory of Open Access Journals (Sweden)

    Kanika Madaan

    2014-01-01

    Full Text Available Dendrimers are the emerging polymeric architectures that are known for their defined structures, versatility in drug delivery and high functionality whose properties resemble with biomolecules. These nanostructured macromolecules have shown their potential abilities in entrapping and/or conjugating the high molecular weight hydrophilic/hydrophobic entities by host-guest interactions and covalent bonding (prodrug approach respectively. Moreover, high ratio of surface groups to molecular volume has made them a promising synthetic vector for gene delivery. Owing to these properties dendrimers have fascinated the researchers in the development of new drug carriers and they have been implicated in many therapeutic and biomedical applications. Despite of their extensive applications, their use in biological systems is limited due to toxicity issues associated with them. Considering this, the present review has focused on the different strategies of their synthesis, drug delivery and targeting, gene delivery and other biomedical applications, interactions involved in formation of drug-dendrimer complex along with characterization techniques employed for their evaluation, toxicity problems and associated approaches to alleviate their inherent toxicity.

  4. Biological properties of water-soluble phosphorhydrazone dendrimers

    Directory of Open Access Journals (Sweden)

    Anne-Marie Caminade

    2013-01-01

    Full Text Available Dendrimers are hyperbranched and perfectly defined macromolecules, constituted of branches emanating from a central core in an iterative fashion. Phosphorhydrazone dendrimers constitute a special family of dendrimers, possessing one phosphorus atom at each branching point. The internal structure of these dendrimers is hydrophobic, but hydrophilic terminal groups can induce the solubility of the whole structure in water. Indeed, the properties of these compounds are mainly driven by the type of terminal groups their bear; this is especially true for the biological properties. For instance, positively charged terminal groups are efficient for transfection experiments, as drug carriers, as anti-prion agents, and as inhibitor of the aggregation of Alzheimer's peptides, whereas negatively charged dendrimers have anti-HIV properties and can influence the human immune system, leading to anti-inflammatory properties usable against rheumatoid arthritis. This review will give the most representative examples of the biological properties of water-soluble phosphorhydrazone dendrimers, organized depending on the type of terminal groups they bear.

  5. Gene Transfer in Eukaryotic Cells Using Activated Dendrimers

    Science.gov (United States)

    Dennig, Jörg

    Gene transfer into eukaryotic cells plays an important role in cell biology. Over the last 30 years a number of transfection methods have been developed to mediate gene transfer into eukaryotic cells. Classical methods include co-precipitation of DNA with calcium phosphate, charge-dependent precipitation of DNA with DEAE-dextran, electroporation of nucleic acids, and formation of transfection complexes between DNA and cationic liposomes. Gene transfer technologies based on activated PAMAM-dendrimers provide another class of transfection reagents. PAMAM-dendrimers are highly branched, spherical molecules. Activation of newly synthesized dendrimers involves hydrolytic removal of some of the branches, and results in a molecule with a higher degree of flexibility. Activated dendrimers assemble DNA into compact structures via charge interactions. Activated dendrimer - DNA complexes bind to the cell membrane of eukaryotic cells, and are transported into the cell by non-specific endocytosis. A structural model of the activated dendrimer - DNA complex and a potential mechanism for its uptake into cells will be discussed.

  6. DESIGN AND PHOTOFUNCTIONS OF DENDRIMER-ENCAPSULATED POLY(PHENYLENEETHYNYLENE)S

    Institute of Scientific and Technical Information of China (English)

    Dong-lin Jiang; Takafumi Sato; Takuzo Aida

    2001-01-01

    A series of dendrimer-encapsulated poly(phenyleneethynylene)s 4~6 were synthesized. The light-harvesting antenna fimctions of dendrimer frameworks together with the blue-light emitting activities of 4~6 were highlighted.

  7. Electrochemistry of polyamidoamine dendrimers ester gel electrolytes

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong; MO Zunli

    2004-01-01

    This paper described the first example of polyamidoamine dendrimers ester (PAMAM) used as a gel electrolyte with a short-chain polyethylene glycol (MPEG-400) as a plasticizer. The polymer films are solid and sticky. Background cyclic voltammetry (CV) shows a potential window between +0.7 and -0.7 V vs. Ag/AgCl. The voltammetry of ferrocene and 7,7,8,8-tetracyanoquinodimethane (TCNQ) indicates that diffusion coefficients are in the range of 10-a-10-9 cm2/s.Ionic conductivities are approximately 10-6 S/cm. Similar films using dimethyl sulfoxide (DMSO) as a plasticizer instead of MPEG-400 have demonstrated ionic conductivities of 10-4 S/cra and reversible voltammetry. However, UV spectrophotometry shows that 70% of the DMSO is lost under vacuum, indicating the difficulty in quantifying the DMSO content when exposed to vacuum.

  8. Improving the Stability of Fluorescent Silver Nanoclusters

    Science.gov (United States)

    Swanson, Nicholas; Stanko, Danielle; Campbell, Ian; Wittmershaus, Bruce

    The quantum mechanical nature of noble metal nanoparticles results in them having optical properties much different from the bulk metal. Silver nanoclusters (AgNC), groups of 4 to 20 atoms, are characterized by strong optical transitions in the visible part of the spectrum giving them an appearance like fluorescent organic dyes. These nanoclusters can also have fluorescence quantum yields over 90%. Following the analysis of published results of DNA templated nanoclusters, we created a procedure for synthesizing AgNC. The AgNC have a high fluorescence quantum yield but degrade with a lifetime of only a few days when in solution at room temperature. Our goal in this study was to increase the stability of the AgNC towards improving their value as a fluorescent material in various applications, such as luminescent solar concentrators. To increase their stability, we've chosen to modify our procedure by removing oxygen from the solution after the sample has reacted. Oxygen removal caused a significant increase in the stability of the clusters over a given period of time. This material is based upon work supported by the National Science Foundation under Grant Number NSF-ECCS-1306157.

  9. Photoactivity and pH sensitivity of methyl orange functionalized poly(propyleneamine) dendrimers

    NARCIS (Netherlands)

    Dirksen, A.; Zuidema, E.; Williams, R.M.; De Cola, L.; Kauffmann, C.; Vögtle, F.; Roque, A.; Pina, F.

    2002-01-01

    For the first time a pH indicator that responds to two different external stimuli, i.e. pH and light, namely methyl orange, has been implemented in a dendrimer. Six generations (G0-G5) of methyl orange-functionalized poly(propyleneamine) dendrimers ("MO dendrimers") have been synthesized and

  10. Photoactivity and pH sensitivity of methyl orange functionalized poly(propyleneamine) dendrimers

    NARCIS (Netherlands)

    Dirksen, A.; Zuidema, E.; Williams, R.M.; De Cola, L.; Kauffmann, C.; Vögtle, F.; Roque, A.; Pina, F.

    2002-01-01

    For the first time a pH indicator that responds to two different external stimuli, i.e. pH and light, namely methyl orange, has been implemented in a dendrimer. Six generations (G0-G5) of methyl orange-functionalized poly(propyleneamine) dendrimers ("MO dendrimers") have been synthesized and charact

  11. Synthesis and Catalytic Evaluation of Dendrimer-Encapsulated Cu Nanoparticles: An Undergraduate Experiment Exploring Catalytic Nanomaterials

    Science.gov (United States)

    Feng, Z. Vivian; Lyon, Jennifer L.; Croley, J. Sawyer; Crooks, Richard M.; Vanden Bout, David A.; Stevenson, Keith J.

    2009-01-01

    Copper nanoparticles were synthesized using generation 4 hydroxyl-terminated (G4-OH) poly(amidoamine) (PAMAM) dendrimers as templates. The synthesis is conducted by coordinating copper ions with the interior amines of the dendrimer, followed by chemical reduction to form dendrimer-encapsulated copper nanoparticles (Cu-DEN). The catalytic…

  12. Formation of solid Kr nanoclusters in MgO

    NARCIS (Netherlands)

    van Huis, MA; van Veen, A; Schut, H; Kooi, BJ; De Hosson, JTM

    2003-01-01

    The phenomenon of positron confinement enables us to investigate the electronic structure of nanoclusters embedded in host matrices. Solid Kr nanoclusters are a very interesting subject of investigation because of the very low predicted value of the positron affinity of bulk Kr. In this work,

  13. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.

    2016-06-22

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  14. Molecular interactions in particular Van der Waals nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Jungclas, Hartmut; Schmidt, Lothar [Marburg Univ. (Germany). Chemistry Dept.; Komarov, Viacheslav V.; Popova, Anna M. [Marburg Univ. (Germany). Chemistry Dept.; Lomonosov Moscow State Univ. (Russian Federation). Skobeltzin Inst. of Nuclear Physics

    2017-04-01

    A method is presented to analyse the interaction energies in a nanocluster, which is consisting of three neutral molecules bound by non-covalent long range Van der Waals forces. One of the molecules (M{sub 0}) in the nanocluster has a permanent dipole moment, whereas the two other molecules (M{sub 1} and M{sub 2}) are non-polar. Analytical expressions are obtained for the numerical calculation of the dispersion and induction energies of the molecules in the considered nanocluster. The repulsive forces at short intermolecular distances are taken into account by introduction of damping functions. Dispersion and induction energies are calculated for a nanocluster with a definite geometry, in which the polar molecule M{sub 0} is a linear hydrocarbon molecule C{sub 5}H{sub 10} and M{sub 1} and M{sub 2} are pyrene molecules. The calculations are done for fixed distances between the two pyrene molecules. The results show that the induction energies in the considered three-molecular nanocluster are comparable with the dispersion energies. Furthermore, the sum of induction energies in the substructure (M{sub 0}, M{sub 1}) of the considered nanocluster is much higher than the sum of induction energies in a two-molecular nanocluster with similar molecules (M{sub 0}, M{sub 1}) because of the absence of an electrostatic field in the latter case. This effect can be explained by the essential intermolecular induction in the three-molecular nanocluster.

  15. Passivation of cobalt nanocluster assembled thin films with hydrogen

    DEFF Research Database (Denmark)

    Romero, C.P.; Volodin, A.; Di Vece, M.

    2012-01-01

    The effect of hydrogen passivation on bare and Pd capped cobalt nanocluster assembled thin films was studied with Rutherford backscattering spectrometry (RBS) and magnetic force microscopy (MFM) after exposure to ambient conditions. The nanoclusters are produced in a laser vaporization cluster...

  16. Interaction of nucleic acids with carbon nanotubes and dendrimers.

    Science.gov (United States)

    Nandy, Bidisha; Santosh, Mogurampelly; Maiti, Prabal K

    2012-07-01

    Nucleic acid interaction with nanoscale objects like carbon nanotubes (CNTs) and dendrimers is of fundamental interest because of their potential application in CNT separation, gene therapy and antisense therapy. Combining nucleic acids with CNTs and dendrimers also opens the door towards controllable self-assembly to generate various supra-molecular and nano-structures with desired morphologies. The interaction between these nanoscale objects also serve as a model system for studying DNA compaction, which is a fundamental process in chromatin organization. By using fully atomistic simulations, here we report various aspects of the interactions and binding modes of DNA and small interfering RNA (siRNA) with CNTs, graphene and dendrimers. Our results give a microscopic picture and mechanism of the adsorption of single- and double-strand DNA (ssDNA and dsDNA) on CNT and graphene. The nucleic acid-CNT interaction is dominated by the dispersive van der Waals (vdW) interaction. In contrast, the complexation of DNA (both ssDNA and dsDNA) and siRNA with various generations of poly-amido-amine (PAMAM) dendrimers is governed by electrostatic interactions. Our results reveal that both the DNA and siRNA form stable complex with the PAMAM dendrimer at a physiological pH when the dendrimer is positively charged due to the protonation of the primary amines. The size and binding energy of the complex increase with increase in dendrimer generation. We also give a summary of the current status in these fields and discuss future prospects.

  17. Interaction of nucleic acids with carbon nanotubes and dendrimers

    Indian Academy of Sciences (India)

    Bidisha Nandy; Mogurampelly Santosh; Prabal K Maiti

    2012-07-01

    Nucleic acid interaction with nanoscale objects like carbon nanotubes (CNTs) and dendrimers is of fundamental interest because of their potential application in CNT separation, gene therapy and antisense therapy. Combining nucleic acids with CNTs and dendrimers also opens the door towards controllable self-assembly to generate various supra-molecular and nano-structures with desired morphologies. The interaction between these nanoscale objects also serve as a model system for studying DNA compaction, which is a fundamental process in chromatin organization. By using fully atomistic simulations, here we report various aspects of the interactions and binding modes of DNA and small interfering RNA (siRNA) with CNTs, graphene and dendrimers. Our results give a microscopic picture and mechanism of the adsorption of single- and double-strand DNA (ssDNA and dsDNA) on CNT and graphene. The nucleic acid–CNT interaction is dominated by the dispersive van der Waals (vdW) interaction. In contrast, the complexation of DNA (both ssDNA and dsDNA) and siRNA with various generations of poly-amido-amine (PAMAM) dendrimers is governed by electrostatic interactions. Our results reveal that both the DNA and siRNA form stable complex with the PAMAM dendrimer at a physiological pH when the dendrimer is positively charged due to the protonation of the primary amines. The size and binding energy of the complex increase with increase in dendrimer generation. We also give a summary of the current status in these fields and discuss future prospects.

  18. Potential Antitumor Dendrimers: Synthesis and Characterizations of Rhenium(Ⅰ) and Cis-platin Containing Dendrimers

    Institute of Scientific and Technical Information of China (English)

    Zhao Xinxin; Chit-Kay Chu

    2005-01-01

    @@ 1Introduction The chemistry of dendrimers is a fast developing field and has brought about a tsunami of research activity since Vogtle reported the first preparation in 1978. These hyperbranched macromolecules have grown out of chemists' imagination and have challenged synthetic chemists with their architectural complexity and intriguity. The potentials of these macromolecules are extensive and are synthesized using both organic and inorganic cores from which different scaffoldings are built, and upon which functionalities are attached for specific applications. The synthesis and characterizations of cisplatin and rhenium(Ⅰ) containing PAMAM derivatives will be discussed.

  19. Mechanism of PAMAM Dendrimers Internalization in Hippocampal Neurons.

    Science.gov (United States)

    Vidal, Felipe; Vásquez, Pilar; Díaz, Carola; Nova, Daniela; Alderete, Joel; Guzmán, Leonardo

    2016-10-03

    Polyamidoamine (PAMAM) dendrimers are hyperbranched macromolecules which have been described as one of the most promising drug nanocarrier systems. A key process to understand is their cellular internalization mechanism because of its direct influence on their intracellular distribution, association with organelles, entry kinetics, and cargo release. Despite that internalization mechanisms of dendrimers have been studied in different cell types, in the case of neurons they are not completely described. Considering the relevance of central nervous system (CNS) diseases and neuropharmacology, the aim of this report is to describe the molecular internalization mechanism of different PAMAM-based dendrimer systems in hippocampal neurons. Four dendrimers based on fourth generation PAMAM with different surface properties were studied: unmodified G4, with a positively charged surface; PP50, with a substitution of the 50% of amino surface groups with polyethylene glycol neutral groups; PAc, with a substitution of the 30% of amino surface groups with acrylate anionic groups; and PFO, decorated with folic acid groups in a 25% of total terminal groups. Confocal images show that both G4 and PFO are able to enter the neurons, but not PP50 and PAc. Colocalization study with specific endocytosis markers and specific endocytosis inhibitor assay demonstrate that clathrin-mediated endocytosis would be the main internalization mechanism for G4, whereas clathrin- and caveolae-mediated endocytosis would be implicated in PFO internalization. These results show the existence of different internalization mechanisms for PAMAM dendrimers in neurons and the possibility to control their internalization properties with specific chemical modifications.

  20. Cationic PAMAM dendrimers as pore-blocking binary toxin inhibitors.

    Science.gov (United States)

    Förstner, Philip; Bayer, Fabienne; Kalu, Nnanya; Felsen, Susanne; Förtsch, Christina; Aloufi, Abrar; Ng, David Y W; Weil, Tanja; Nestorovich, Ekaterina M; Barth, Holger

    2014-07-14

    Dendrimers are unique highly branched macromolecules with numerous groundbreaking biomedical applications under development. Here we identified poly(amido amine) (PAMAM) dendrimers as novel blockers for the pore-forming B components of the binary anthrax toxin (PA63) and Clostridium botulinum C2 toxin (C2IIa). These pores are essential for delivery of the enzymatic A components of the internalized toxins from endosomes into the cytosol of target cells. We demonstrate that at low μM concentrations cationic PAMAM dendrimers block PA63 and C2IIa to inhibit channel-mediated transport of the A components, thereby protecting HeLa and Vero cells from intoxication. By channel reconstitution and high-resolution current recording, we show that the PAMAM dendrimers obstruct transmembrane PA63 and C2IIa pores in planar lipid bilayers at nM concentrations. These findings suggest a new potential role for the PAMAM dendrimers as effective polyvalent channel-blocking inhibitors, which can protect human target cells from intoxication with binary toxins from pathogenic bacteria.

  1. The application of poly(amidoamine dendrimers for modification of jute yarns: Preparation and dyeing properties

    Directory of Open Access Journals (Sweden)

    Ali Akbar Zolriasatein

    2015-03-01

    Full Text Available In this study, poly(amidoamine (PAMAM G-2 dendrimer was used for jute yarn. Fourier transform infrared spectroscopy (FT-IR revealed that all carbonyl groups of jute fibers reacted with amino groups of polyamidoamine dendrimers. SEM observation indicated the good dispersion PAMAM dendrimers. Jute yarns pretreated with PAMAM dendrimer displayed markedly enhanced color strength with reactive dyes, even when dyeing had been carried out in the absence of electrolyte or alkali. Dendrimer-treated jute yarn showed much better light-fastness than untreated jute yarn.

  2. The influence of PAMAM dendrimers surface groups on their interaction with porcine pepsin.

    Science.gov (United States)

    Ciolkowski, Michal; Rozanek, Monika; Bryszewska, Maria; Klajnert, Barbara

    2013-10-01

    In this study the ability of three polyamidoamine (PAMAM) dendrimers with different surface charge (positive, neutral and negative) to interact with a negatively charged protein (porcine pepsin) was examined. It was shown that the dendrimer with a positively charged surface (G4 PAMAM-NH2), as well as the dendrimer with a neutral surface (G4 PAMAM-OH), were able to inhibit enzymatic activity of pepsin. It was also found that these dendrimers act as mixed partially non-competitive pepsin inhibitors. The negatively charged dendrimer (G3.5 PAMAM-COOH) was not able to inhibit the enzymatic activity of pepsin, probably due to the electrostatic repulsion between this dendrimer and the protein. No correlation between changes in enzymatic activity of pepsin and alterations in CD spectrum of the protein was observed. It indicates that the interactions between dendrimers and porcine pepsin are complex, multidirectional and not dependent only on disturbances of the secondary structure.

  3. MONODISPERSED AND NANOSIZED DENDRIMER/POLYSTYRENE LATEX PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Changfeng Yi; Zushun Xu; Warren T. Ford

    2004-01-01

    Emulsion polymerization of styrene was carried out using dendrimer DAB-dendr-(NH2)64 as seed. The size and size distribution of the emulsion particles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the effects of emulsion polymerization conditions on the preparation of emulsion particle were investigated. It has been found that the nanosized dendrimer/polystyrene polymer emulsion particles obtained were in the range of 26~64 nm in diameter, and were monodisperse; the size and size distribution of emulsion particles were influenced by the contents of dendrimer DAB-dendr-(NH2)64, emulsifier and initiator, as well as the pH value.

  4. On Forgotten Topological Indices of Some Dendrimers Structure.

    Science.gov (United States)

    Bashir, Yasir; Aslam, Adnan; Kamran, Muhammad; Qureshi, Muhammad Imran; Jahangir, Adnan; Rafiq, Muhammad; Bibi, Nargis; Muhammad, Nazeer

    2017-05-24

    A series of previously conducted experiments pertaining to various chemicals and drugs uncover a natural linkage between the molecular structures and the bio-medical and pharmacological characteristics. The forgotten topological index computed for the molecular structures of various chemical compounds and drugs has proven significant in medical and pharmaceutical fields by predicting biological features of new chemical compounds and drugs. A topological index can be considered as the transformation of chemical structure into a real number. Dendrimers are highly-branched star-shaped macromolecules with nanometer-scale dimensions. Dendrimers are defined by three components: a central core, an interior dendritic structure (the branches), and an exterior surface with functional surface groups. In this paper, we determine forgotten topological indices of poly(propyl) ether imine, porphyrin, and zinc-porphyrin dendrimers.

  5. On Topological Indices of Certain Families of Nanostar Dendrimers.

    Science.gov (United States)

    Husin, Mohamad Nazri; Hasni, Roslan; Arif, Nabeel Ezzulddin; Imran, Muhammad

    2016-06-24

    A topological index of graph G is a numerical parameter related to G which characterizes its molecular topology and is usually graph invariant. In the field of quantitative structure-activity (QSAR)/quantitative structure-activity structure-property (QSPR) research, theoretical properties of the chemical compounds and their molecular topological indices such as the Randić connectivity index, atom-bond connectivity (ABC) index and geometric-arithmetic (GA) index are used to predict the bioactivity of different chemical compounds. A dendrimer is an artificially manufactured or synthesized molecule built up from the branched units called monomers. In this paper, the fourth version of ABC index and the fifth version of GA index of certain families of nanostar dendrimers are investigated. We derive the analytical closed formulas for these families of nanostar dendrimers. The obtained results can be of use in molecular data mining, particularly in researching the uniqueness of tested (hyper-branched) molecular graphs.

  6. Recent advances in click chemistry applied to dendrimer synthesis.

    Science.gov (United States)

    Arseneault, Mathieu; Wafer, Caroline; Morin, Jean-François

    2015-05-20

    Dendrimers are monodisperse polymers grown in a fractal manner from a central point. They are poised to become the cornerstone of nanoscale devices in several fields, ranging from biomedicine to light-harvesting. Technical difficulties in obtaining these molecules has slowed their transfer from academia to industry. In 2001, the arrival of the "click chemistry" concept gave the field a major boost. The flagship reaction, a modified Hüisgen cycloaddition, allowed researchers greater freedom in designing and building dendrimers. In the last five years, advances in click chemistry saw a wider use of other click reactions and a notable increase in the complexity of the reported structures. This review covers key developments in the click chemistry field applied to dendrimer synthesis from 2010 to 2015. Even though this is an expert review, basic notions and references have been included to help newcomers to the field.

  7. Structural properties of star-like dendrimers in solution

    Energy Technology Data Exchange (ETDEWEB)

    Rathgeber, S. [Forschungszentrum Juelich GmbH, IFF Weiche Materie, 52425 Juelich (Germany); Gast, A.P. [Stanford University, Stanford, CA 94305-5025 (United States); Hedrick, J.L. [IBM Almaden Research Center, San Jose, CA 95120-6099 (United States)

    2002-07-01

    We measured the form factor of star-like poly-{epsilon}-caprolactone dendrimers under good solvent conditions with small-angle neutron scattering (SANS). The parameters varied in the experiment were the dendrimer generation g=1,2,3 and the number of segments between the branching units n=5,10,15,20. The results are discussed in the frame work of the Beaucage model from which we cannot only derive the radius of gyration R{sub g} of the dendrimers but also their fractal dimensions. Decreasing the number of spacer units between the branching points results in a strong stretching of the dendrons. The fractal dimension increases monotonically with increasing generation and spacer number between the limit expected for a low-functionality star P{approx}5/3 (loose, polymeric structure) and that expected for a high-functionality star P{approx}3 (compact shape). (orig.)

  8. Structural properties of star-like dendrimers in solution

    Science.gov (United States)

    Rathgeber, S.; Gast, A. P.; Hedrick, J. L.

    We measured the form factor of star-like poly-ɛ-caprolactone dendrimers under good solvent conditions with small-angle neutron scattering (SANS). The parameters varied in the experiment were the dendrimer generation g=1,2,3 and the number of segments between the branching units n=5,10,15,20. The results are discussed in the frame work of the Beaucage model from which we cannot only derive the radius of gyration Rg of the dendrimers but also their fractal dimensions. Decreasing the number of spacer units between the branching points results in a strong stretching of the dendrons. The fractal dimension increases monotonically with increasing generation and spacer number between the limit expected for a low-functionality star P 5/3 (loose, polymeric structure) and that expected for a high-functionality star P 3 (compact shape).

  9. Dendrimer Templates for the Formation of Silver Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    LI Guo-ping; LUO Yun-jun; XU Hou-cai; TAN Hui-min

    2006-01-01

    In order to control the size and shape of Ag nanoparticles obtained by using poly(amidoamine) (PAMAM) dendrimer as template, the complexation between Ag+ ions and dendrimer studied extensively by UVVis spectroscopy and FTIR. After the Ag+/PAMAM demdrimer being reduced by direct chemical reduction,Ag (0) nanoparticles was formed, whose structure and characterization were studied by UV-Vis spectroscopy,transmission electron microscopy (TEM) and electron diffraction (ED) respectively. The results reveal that Ag nanoparticles is a kind of face center cubic crystal and its average size is 4.5 nm. The solubility and stability of the solution containing Ag nanoparticles also indicate that dendrimer is a good kind of template, as well as a protective agent.

  10. Recent Advances in Click Chemistry Applied to Dendrimer Synthesis

    Directory of Open Access Journals (Sweden)

    Mathieu Arseneault

    2015-05-01

    Full Text Available Dendrimers are monodisperse polymers grown in a fractal manner from a central point. They are poised to become the cornerstone of nanoscale devices in several fields, ranging from biomedicine to light-harvesting. Technical difficulties in obtaining these molecules has slowed their transfer from academia to industry. In 2001, the arrival of the “click chemistry” concept gave the field a major boost. The flagship reaction, a modified Hüisgen cycloaddition, allowed researchers greater freedom in designing and building dendrimers. In the last five years, advances in click chemistry saw a wider use of other click reactions and a notable increase in the complexity of the reported structures. This review covers key developments in the click chemistry field applied to dendrimer synthesis from 2010 to 2015. Even though this is an expert review, basic notions and references have been included to help newcomers to the field.

  11. In Vivo Renal Clearance, Biodistribution, Toxicity of Gold nanoclusters

    CERN Document Server

    Zhang, Xiao-Dong; Shen, Xiu; Liu, Pei-Xun; Fan, Fei-Yue; Fan, Sai-Jun; 10.1016/j.biomaterials.2012.03.020

    2012-01-01

    Gold nanoparticles have shown great prospective in cancer diagnosis and therapy, but they can not be metabolized and prefer to accumulate in liver and spleen due to their large size. The gold nanoclusters with small size can penetrate kidney tissue and have promise to decrease in vivo toxicity by renal clearance. In this work, we explore the in vivo renal clearance, biodistribution, and toxicity responses of the BSA- and GSH-protected gold nanoclusters for 24 hours and 28 days. The BSA-protected gold nanoclusters have low-efficient renal clearance and only 1% of gold can be cleared, but the GSH-protected gold nanoclusters have high-efficient renal clearance and 36 % of gold can be cleared after 24 hours. The biodistribution further reveals that 94% of gold can be metabolized for the GSH-protected nanoclusters, but only less than 5% of gold can be metabolized for the BSA-protected nanoclusters after 28 days. Both of the GSH- and BSA-protected gold nanoclusters cause acute infection, inflammation, and kidney fu...

  12. Impact of Dendrimers on Solubility of Hydrophobic Drug Molecules

    Directory of Open Access Journals (Sweden)

    Sonam Choudhary

    2017-05-01

    Full Text Available Adequate aqueous solubility has been one of the desired properties while selecting drug molecules and other bio-actives for product development. Often solubility of a drug determines its pharmaceutical and therapeutic performance. Majority of newly synthesized drug molecules fail or are rejected during the early phases of drug discovery and development due to their limited solubility. Sufficient permeability, aqueous solubility and physicochemical stability of the drug are important for achieving adequate bioavailability and therapeutic outcome. A number of different approaches including co-solvency, micellar solubilization, micronization, pH adjustment, chemical modification, and solid dispersion have been explored toward improving the solubility of various poorly aqueous-soluble drugs. Dendrimers, a new class of polymers, possess great potential for drug solubility improvement, by virtue of their unique properties. These hyper-branched, mono-dispersed molecules have the distinct ability to bind the drug molecules on periphery as well as to encapsulate these molecules within the dendritic structure. There are numerous reported studies which have successfully used dendrimers to enhance the solubilization of poorly soluble drugs. These promising outcomes have encouraged the researchers to design, synthesize, and evaluate various dendritic polymers for their use in drug delivery and product development. This review will discuss the aspects and role of dendrimers in the solubility enhancement of poorly soluble drugs. The review will also highlight the important and relevant properties of dendrimers which contribute toward drug solubilization. Finally, hydrophobic drugs which have been explored for dendrimer assisted solubilization, and the current marketing status of dendrimers will be discussed.

  13. Two Dimensional Aggregation Behaviors of Quinoxaline Dendrimers.

    Science.gov (United States)

    Choi, Soyoung; Lee, Hoik; Kim, Hwan Kyu; Lee, Sang Uck; Sohn, Daewon

    2015-02-01

    This study focuses on the molecular behavior of two dendrimers containing a hydrophilic core group (carboxyl group) and hydrophobic branches (quinoxaline and methoxyphenyl groups), 2,3-bis(4-(2,3- bis(4-methoxyphenyl)quinoxalin-6-yloxy)phenyl)quinoxaline-6-carb-oxylic acid (G2) and 2,3-bis(4-(2,3-bis(4-(2,3-bis(4-methoxyphenyl)quinoxalin-6-yloxy)phe-nyl)quinoxalin-6-y-oxy)phenyl) quin oxaline-6-carboxylic acid (G3) at the air-water interface. To understand the mechanism of the self-assembly of these molecules, we measured the surface pressure-area (III-A) isotherm and investigated the surface morphology of Langmuir-Blodgett films transferred onto hydrophilic silicon wafers using atomic force microscopy (AFM). Upon compression, G2 molecules stand up and steadily make close-packed monolayer whereas G3 molecules form circular domains and gradually make aggregates of domains. These results were confirmed by the X-ray Reflectivity (XRR) profiles of G2 and G3 monolayers transferred onto silicon substrates.

  14. Nanoclusters and Microparticles in Gases and Vapors

    CERN Document Server

    Smirnov, Boris M

    2012-01-01

    Research of processes involving Nanoclusters and Microparticleshas been developing fastin many fields of rescent research, in particular in materials science. To stay at the cutting edge of this development, a sound understanding of the processes is needed. In this work, several processes involving small particles are described, such as transport processes in gases, charging of small particles in gases, chemical processes, atom attachment and quenching of excited atomic particles on surfaces, nucleation, coagulation, coalescence and growth processes for particles and aggregates. This work pres

  15. Peptide-stabilized, fluorescent silver nanoclusters

    DEFF Research Database (Denmark)

    Gregersen, Simon; Vosch, Tom André Jos; Jensen, Knud Jørgen

    2016-01-01

    . Herein, we demonstrate how solid-phase methods can increase throughput dramatically in peptide ligand screening and in initial evaluation of fluorescence intensity and chemical stability of peptide-stabilized AgNCs (P-AgNCs). 9-Fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis......Few-atom silver nanoclusters (AgNCs) can exhibit strong fluorescence; however, they require ligands to prevent aggregation into larger nanoparticles. Fluorescent AgNCs in biopolymer scaffolds have so far mainly been synthesized in solution, and peptides have only found limited use compared to DNA...

  16. Preparation and termination of carbosilane dendrimer based on siloxane tetramer

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chung Kyun; Park, Eun Mi [Donga Univ., Pusan (Korea, Republic of)

    1998-02-01

    Dendritic macromolecules of the first to fourth generation were synthesized, using alkenylation and hydrosilation cycles with allylmagnesium bromide and dichloromethylsilane as building blocks and siloxane tetramer (Me(CH{sub 2}=CH)SiO){sub 4} as core molecule. By the reaction of the dichloromethylsilyl-capped generation (G4P) with p-bromophenol, p-phenylphenol and lithium phenyethynylide, dendrimers with specific functions (G4P-BP) (Mw: 16,300), G4P-PP (16,121), and G4P-PA (11,764) have been produced. Analysis of new dendrimers by NMR, UV and MALDI mass spectrometry suggests that they are pure and unified.

  17. Electrical Properties of Multi-Pyrene/Porphyrin-Dendrimers.

    Science.gov (United States)

    Martínez-Klimov, Mark Euguenii; Organista-Mateos, Ulises; Borja-Miranda, Andrés; Rivera, Margarita; Amelines-Sarria, Oscar; Martínez-García, Marcos

    2015-09-22

    Dendrimers bearing pyrene donor groups have been obtained and act as efficient light-harvesting antennae capable of transferring light energy through space from their periphery to their core. The light-harvesting ability increases with each generation due to an increase in the number of peripheral pyrenes. In order to evaluate the photovoltaic properties of the compounds, thermal evaporated thin films were produced and the voltage response in the presence of visible light was obtained. The energy transfer efficiency was found to be almost quantitative for the first and second generations. The dendrimers have the potential to become integral components of molecular photonic devices.

  18. Electrical Properties of Multi-Pyrene/Porphyrin-Dendrimers

    Directory of Open Access Journals (Sweden)

    Mark Euguenii Martínez-Klimov

    2015-09-01

    Full Text Available Dendrimers bearing pyrene donor groups have been obtained and act as efficient light-harvesting antennae capable of transferring light energy through space from their periphery to their core. The light-harvesting ability increases with each generation due to an increase in the number of peripheral pyrenes. In order to evaluate the photovoltaic properties of the compounds, thermal evaporated thin films were produced and the voltage response in the presence of visible light was obtained. The energy transfer efficiency was found to be almost quantitative for the first and second generations. The dendrimers have the potential to become integral components of molecular photonic devices.

  19. M-Polynomial and Related Topological Indices of Nanostar Dendrimers

    Directory of Open Access Journals (Sweden)

    Mobeen Munir

    2016-09-01

    Full Text Available Dendrimers are highly branched organic macromolecules with successive layers of branch units surrounding a central core. The M-polynomial of nanotubes has been vastly investigated as it produces many degree-based topological indices. These indices are invariants of the topology of graphs associated with molecular structure of nanomaterials to correlate certain physicochemical properties like boiling point, stability, strain energy, etc. of chemical compounds. In this paper, we first determine M-polynomials of some nanostar dendrimers and then recover many degree-based topological indices.

  20. On the fluctuation mechanism of melting of supported gold nanoclusters.

    Science.gov (United States)

    Pushkin, M A; Troyan, V I; Borisyuk, P V; Borman, V D; Tronin, V N

    2012-11-01

    The size dependence of the melting temperature of Au nanoclusters deposited on SiO2 and HOPG substrates, measured by the elastic-peak electron spectroscopy (EPES) is discussed. The observed behavior of the melting temperature with decrease in clusters' size is qualitatively explained in the framework of the fluctuation mechanism for surface melting. The interaction of nanoclusters with substrate is taken into account by means of the effective surface tension for spherical-segment shaped particles, corresponding to the contact angle of supported nanocluster.

  1. Nonlinear analysis of nano-cluster doped fiber

    Institute of Scientific and Technical Information of China (English)

    LIU Gang; ZHANG Ru

    2007-01-01

    There are prominent nonlinear characteristics that we hope for the semiconductor nano-clusters doped fiber. Refractive index of fiber core can be effectively changed by adulteration. This technology can provide a new method for developing photons components. Because the semiconductor nano-cluster has quantum characteristics,Based on first-order perturbation theory and classical theory of fiber,we deduced refractive index expressions of fiber core,which was semiconductor nano-cluster doped fiber. Finally,third-order nonlinear coefficient equation was gained. Using this equation,we calculated SMF-28 fiber nonlinear coefficient. The equation shows that new third-order coefficient was greater.

  2. Efficiency of genomic DNA extraction dependent on the size of magnetic nanoclusters

    Science.gov (United States)

    Cho, Hyun Ah; Hyun Min, Ji; Hua Wu, Jun; Woo Jang, Jin; Lim, Chae-Seung; Keun Kim, Young

    2014-05-01

    We report the efficiency of genomic DNA extraction as a function of particle size and quantity. For DNA extraction, we synthesized magnetic nanoclusters of various sizes and coated the surface of these magnetic nanoclusters with meso-2,3-dimercaptosuccinic acid. We showed that the nanoclusters had a tight particle size distribution and high crystallinity. Furthermore, we observed that the three types of magnetic nanoclusters studied exhibited ferrimagnetic behavior and that larger nanoclusters showed larger saturation magnetization values. The resultant efficiency of DNA extraction is inversely proportional to particle size in the range of nanoclusters tested, due to the fact that the surface-to-volume ratio decreases as particle size increases.

  3. Coarse-grained simulations of poly(propylene imine) dendrimers in solution

    Science.gov (United States)

    Smeijers, A. F.; Markvoort, A. J.; Pieterse, K.; Hilbers, P. A. J.

    2016-02-01

    The behavior of poly(propylene imine) (PPI) dendrimers in concentrated solutions has been investigated using molecular dynamics simulations containing up to a thousand PPI dendrimers of generation 4 or 5 in explicit water. To deal with large system sizes and time scales required to study the solutions over a wide range of dendrimer concentrations, a previously published coarse-grained model was applied. Simulation results on the radius of gyration, structure factor, intermolecular spacing, dendrimer interpenetration, and water penetration are compared with available experimental data, providing a clear concentration dependent molecular picture of PPI dendrimers. It is shown that with increasing concentration the dendrimer volume diminishes accompanied by a reduction of internalized water, ultimately resulting in solvent filled cavities between stacked dendrimers. Concurrently dendrimer interpenetration increases only slightly, leaving each dendrimer a separate entity also at high concentrations. Moreover, we compare apparent structure factors, as calculated in experimental studies relying on the decoupling approximation and the constant atomic form factor assumption, with directly computed structure factors. We demonstrate that these already diverge at rather low concentrations, not because of small changes in form factor, but rather because the decoupling approximation fails as monomer positions of separate dendrimers become correlated at concentrations well below the overlap concentration.

  4. Interaction of PAMAM dendrimers with bovine insulin depends on nanoparticle end-groups

    Energy Technology Data Exchange (ETDEWEB)

    Nowacka, Olga; Milowska, Katarzyna, E-mail: milowska@biol.uni.lodz.pl; Bryszewska, Maria

    2015-06-15

    We have looked at the interactions between polyamidoamine (PAMAM) dendrimers with different terminal groups (−COOH, −NH{sub 2}, −OH) and bovine insulin. The influence of PAMAM dendrimers on insulin was tested by measuring zeta potential and fluorescence quenching. The secondary structure of insulin in the presence of dendrimers was examined by circular dichroism. The effect of dendrimers on dithiotreitol-induced aggregation of insulin was investigated by spectrophotometry. Dendrimers quenched the fluorescence of insulin, but did not change its secondary structure. Thus dendrimers neither induce hormone aggregation nor inhibit the aggregation process induced by dithiotreitol (DTT), except at 0.01 µmol/l. Dendrimers–insulin interactions are mainly electrostatic. - Highlight: • The interactions between PAMAM dendrimers and insulin were investigated. • The PAMAM dendrimers can quench the fluorescence of insulin. • The PAMAM dendrimers did not change the secondary structure of insulin. • Dendrimers did not induce aggregation of hormone. • Dendrimers–insulin interaction is mainly electrostatic.

  5. A thermochromic silver nanocluster exhibiting dual emission character

    Science.gov (United States)

    Xu, Qing-Qing; Dong, Xi-Yan; Huang, Ren-Wu; Li, Bo; Zang, Shuang-Quan; Mak, Thomas C. W.

    2015-01-01

    A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow.A Ag12(SCH2C10H7)6(CF3CO2)6(CH3CN)6 (1) nanocluster modified using naphthalen-2-yl-methanethiol was synthesized and structurally characterized by single crystal X-ray analysis. The targeted luminescent nanocluster displays dual emission with the property of reversible thermochromism spanning from red to bright yellow. Electronic supplementary information (ESI) available: Experimental section and supporting Fig. S1-S6. CCDC 1004246. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr05122j

  6. Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity.

    Science.gov (United States)

    Dabrzalska, Monika; Janaszewska, Anna; Zablocka, Maria; Mignani, Serge; Majoral, Jean Pierre; Klajnert-Maculewicz, Barbara

    2017-02-23

    The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer-methylene blue (MB). As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS) generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an) was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

  7. Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity

    Directory of Open Access Journals (Sweden)

    Monika Dabrzalska

    2017-02-01

    Full Text Available The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer—methylene blue (MB. As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

  8. Polyphenylene Dendrimers with Perylene Diimide as a Luminescent Core

    NARCIS (Netherlands)

    Herrmann, Andreas; Weil, Tanja; Sinigersky, Veselin; Wiesler, Uwe-Martin; Vosch, Tom; Hofkens, Johan; Schryver, Frans C. De; Müllen, Klaus

    2001-01-01

    A novel synthesis is presented of a fourfold ethynyl-substituted perylene diimide dye 4, which acts as a core molecule for the buildup of polyphenylene dendrimers. Around the luminescent core 4, a first-generation (5), a second-generation (6), and a third-generation (7) polyphenylene dendritic envir

  9. Antiviral mechanism of polyanionic carbosilane dendrimers against HIV-1

    Science.gov (United States)

    Vacas-Córdoba, Enrique; Maly, Marek; De la Mata, Francisco J; Gómez, Rafael; Pion, Marjorie; Muñoz-Fernández, Mª Ángeles

    2016-01-01

    Nanotechnology-derived platforms, such as dendrimers, are very attractive in several biological applications. In the case of human immunodeficiency virus (HIV) infection, polyanionic carbosilane dendrimers have shown great potential as antiviral agents in the development of novel microbicides to prevent the sexual transmission of HIV-1. In this work, we studied the mechanism of two sulfated and naphthylsulfonated functionalized carbosilane dendrimers, G3-S16 and G2-NF16. They are able to inhibit viral infection at fusion and thus at the entry step. Both compounds impede the binding of viral particles to target cell surface and membrane fusion through the blockage of gp120–CD4 interaction. In addition, and for the first time, we demonstrate that dendrimers can inhibit cell-to-cell HIV transmission and difficult infectious synapse formation. Thus, carbosilane dendrimers’ mode of action is a multifactorial process targeting several proteins from viral envelope and from host cells that could block HIV infection at different stages during the first step of infection. PMID:27103798

  10. Dendrimer-coated magnetic particles for radionuclide separation

    NARCIS (Netherlands)

    Grüttner, Cordula; Böhmer, Volker; Casnati, Alessandro; Dozol, Jean-Francois; Reinhoudt, David; Reinoso garcia, M.M.; Rudershausen, Sandra; Teller, Joachim; Ungaro, Rocco; Verboom, Willem; Wang, Pingshan

    2005-01-01

    Magnetic particles were synthesised for radionuclide removal from nuclear wastes by magnetic separation. Dendrimers with terminal amino groups attached to the particle surface were used to bind chelating groups for lanthanides and actinides. This led to a 50–400-fold increase of the distribution

  11. Designing Dendrimers to Offer Micelle-Type Nanocontainers

    Science.gov (United States)

    King, Angela G.

    2005-01-01

    The properties of a dendrimer with hydrophobic and hydrophilic substituents on an orthogonal plane is synthesized and studied. The resulting polymer contains one of the substituents in its concave interior and the other at the convex surface and the design promotes micelle-like behavior in polar solvent and inverted micelle arrangement in…

  12. Fluorophore-cored dendrimers for patterns in metalloprotein sensing.

    Science.gov (United States)

    Jiwpanich, Siriporn; Sandanaraj, Britto S; Thayumanavan, S

    2009-02-21

    In fluorophore-cored dendrimers with peripheral binding functionalities, the effect of generation upon protein binding-induced fluorescence quenching can be unpredictable; this is because the increase in fluorophore-binding functionality distance with generation is also accompanied by an increase in the number of binding moieties and the interplay between the two features is utilized to create patterns for metalloprotein sensing.

  13. A New Convergent Approach to Unsymmetrically Branched Polyether Dendrimers

    Institute of Scientific and Technical Information of China (English)

    GAO Xiaoping; WANG Feng; WANG Xiaolong; ZHOU Zhaoli

    2001-01-01

    @@ Dendrimers are perfect monodisperse macromolecules with a regular and highly branched three-dimensional architecture. The combination of discrete numbers of functionality in one molecular and high densities of active groups, typical for dendritic molecules, has attracted a lot of attention in the fields of medicinal chenistry (e.g. in drug delivery system), host-guest chemistry and catalysis chemistry[1].

  14. Controlled nanoclustering of magnetic nanoparticles using telechelic polysiloxane and disiloxane

    Energy Technology Data Exchange (ETDEWEB)

    Thong-On, Bandit; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha, E-mail: methar@nu.ac.th [Naresuan University, Department of Chemistry, Faculty of Science (Thailand)

    2015-06-15

    Diacrylate-terminated polydimethylsiloxane (PDMS) and disiloxane were synthesized and used for controlling degree of nanoclustering of magnetite nanoparticles (MNPs). PDMS was synthesized via a ring-opening polymerization of octamethylcyclotetrasiloxane (D{sub 4}), followed by end functionalization with diacrylate groups. Diacrylate-terminated disiloxane was separately synthesized in a similar fashion without the use of D{sub 4} in the reaction. They were then reacted with amino-coated MNPs to obtain MNP-embedded siloxane nanoclusters. Transmission electron microscopy showed the formation of MNP-siloxane nanoclusters with the size of 70–200 nm. Degree of MNP nanoclustering can be adjusted by varying the MNP-to-siloxane ratio to obtain hydrodynamic size ranging from 200 to 2400 nm. Using the same ratio of MNPs to the siloxanes, PDMS resulted in the nanoclusters with smaller D{sub h} and more stable in toluene than those coated with disiloxane. These novel nanoclusters with controllable size might be ideal candidates for biomedical and other advanced applications after suitable surface modification.

  15. Surface modification of adamantane-terminated gold nanoclusters using cyclodextrins.

    Science.gov (United States)

    Yan, Chunyang; Liu, Chao; Abroshan, Hadi; Li, Zhimin; Qiu, Renhua; Li, Gao

    2016-08-17

    The surface functionality of Au38S2(SAdm)20 nanoclusters (-SAdm = adamantanethiolate) in the presence of α-, β-, and γ-cyclodextrins (CDs) is studied. The supramolecular chemistry and host-guest interactions of CDs and the protecting ligands of nanoclusters are investigated using UV-vis and NMR spectroscopies, MALDI mass spectrometry, and molecular dynamics simulations. In contrast to α- and γ-CDs, the results show that β-CDs are capable of efficiently chemisorbing onto the Au38S2(SAdm)20 nanoclusters to yield Au38S2(SAdm)20-(β-CD)2 conjugates. MD simulations revealed that two -SAdm ligands of the nanoparticle with the least steric hindrance are capable to selectively be accommodated into hydrophobic cavity of β-CDs, as furthermore confirmed by NMR spectroscopy. The conjugates largely improve the stability of the nanoclusters in the presence of strong oxidants (e.g., TBHP). Further, the electrochemical properties of Au38S2(SAdm)20 nanoclusters and Au38S2(SAdm)20-(β-CD)2 conjugates are compared. The charge transfer to the redox probe molecules (e.g., K3Fe(CN)6) in solution was monitored by cyclic voltammetry. It is found that β-CDs act as an umbrella to cover the fragile metal cores of the nanoclusters, thereby blocking direct interaction with destabilizing agents and hence quenching the charge transfer process.

  16. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Vega, A. Estrada de la; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2016-01-15

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  17. Fluorescence study on the interactions of PAMAM dendrimers and their derivatives with bovine serum albumin

    Institute of Scientific and Technical Information of China (English)

    WANG Yanming; SONG Yu; KONG Deling; YU Yaoting

    2005-01-01

    The interactions of amino-terminated, and ethylenediamine core poly(amidoamine) (PAMAM) dendrimers and their derivatives with bovine serum albumin (BSA) were investigated by fluorescence spectroscopy. Experimental results showed that the fluorescence intensity of BSA decreased after the addition of different modified dendrimers, and the extent of the fluorescence quenching caused by various modified dendrimers strongly depends upon the different functional groups on their surfaces. We also investigated the influence of pH and ionic strength on the interaction between various modified dendrimers and BSA. Circular dichroism (CD) spectroscopic measurements showed that the content of α-helix structure of BSA decreased after the addition of different modified dendrimers, which indicated that dendrimers induced changes in the secondary structure of BSA.

  18. Structural characterization of poly(amino)ester dendrimers and related impurities by electrospray tandem mass spectrometry.

    Science.gov (United States)

    Tintaru, Aura; Monnier, Valérie; Bouillon, Camille; Giordanengo, Rémi; Quéléver, Gilles; Peng, Ling; Charles, Laurence

    2010-08-15

    An acid-terminated poly(amino)ester dendrimer was studied by electrospray ionization tandem mass spectrometry to establish its fragmentation pathways, with the aim of using them to investigate the structure of any defective molecules generated during the dendrimer synthesis. This poly(amino)ester dendrimer could be ionized in both polarities but the most structurally relevant dissociation pathways were found from the deprotonated molecule in negative ion mode. The dissociation pattern of this dendrimer is fully described and supported by accurate mass measurements. The main dissociation reactions of the negatively charged polyacidic dendrimer were shown to consist of (i) the release of carbon dioxide and ethene within a branch, which proceeds as many times as intact neutral branches are available; and (ii) the elimination of an entire dendrimer arm. Monitoring the occurrence of these reactions together with any deviation from these two main routes allowed six major dendritic impurities to be structurally characterized.

  19. Interaction of phosphorus dendrimers with HIV peptides—Fluorescence studies of nano-complexes formation

    Energy Technology Data Exchange (ETDEWEB)

    Ciepluch, Karol, E-mail: ciepluch@biol.uni.lodz.pl [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland); Ionov, Maksim [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland); Majoral, Jean-Pierre [Laboratoire de Chimie de Coordination du CNRS (LCC), 205 Route de Narbonne, F-31077 Toulouse cedex 4 (France); Muñoz-Fernández, Maria Angeles [Laboratorio InmunoBiología Molecular, Hospital General Universitario Gregorio Marañón, Madrid (Spain); Bryszewska, Maria [Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska Street 141/143, 90-236 Lodz (Poland)

    2014-04-15

    In this study, dendrimers emerge as an alternative approach for delivery of HIV peptides to dendritic cells. Gp160, NH-EIDNYTNTIYTLLEE-COOH; P24, NH-DTINEEAAEW-COOH and Nef, NHGMDDPEREVLEWRFDSRLAF-COOH peptides were complexed with two types of positively charged phosphorus-containing dendrimers (CPD). Fluorescence polarization, dynamic light scattering, transmission and electron microscopy (TEM) techniques were chosen to evaluate the dendriplexes stability. We were able to show that complexes were stable in time and temperature. This is crucial for using these peptide/dendrimer nano-complexes in a new vaccine against HIV-1 infection. -- Highlights: • The phosphorus dendrimers as nanocarriers of HIV-peptides are proposed. • The complexes of dendrimers and HIV-peptides were stable in time, temperature. • The results convince that phosphorus dendrimers could be consider as anti-HIV vaccine candidates.

  20. Solubility improvement of an anthelmintic benzimidazole carbamate by association with dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, L.; Sigal, E.; Santo, M., E-mail: msanto@exa.unrc.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto (Argentina); Otero, L.; Silber, J. J. [Departamento de Quimica. Facultad de Ciencias Exactas Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Rio Cuarto (Argentina)

    2011-10-15

    The improvement of aqueous solubility of methyl (5-[propylthio]-1H-benzimidazole-2-yl) carbamate, albendazole (ABZ) using polyamidoamine (PAMAM) dendrimers as solubility enhancers was investigated. Full generation PAMAM dendrimers with amine terminal groups, (G3), with hydroxyl terminal groups (G3OH) and half generation PAMAM dendrimers with carboxylate terminal groups (G2.5 and G3.5), were chosen for this study. The nature of dendrimer-ABZ association was investigated by UV absorption, fluorescence emission measurements and by {sup 1}H-NMR spectroscopy. The results obtained show that these polymeric structures have the capacity to enhance the solubility of ABZ, both lipophilic and specific hydrogen bond interactions contributing to the guest-host association. Although all studied dendrimers have hydrophobic internal nanoenvironments with similar dimensions, their surfaces differ significantly and the nature and the localization of the interactions involved in ABZ-dendrimer association depend on the type of terminal groups. (author)

  1. pH controlled gating of toxic protein pores by dendrimers

    Science.gov (United States)

    Mandal, Taraknath; Kanchi, Subbarao; Ayappa, K. G.; Maiti, Prabal K.

    2016-06-01

    Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent bacterial strains, on a target cell membrane is a challenging and active area of research. Here we demonstrate that PAMAM dendrimers can act as effective pH controlled gating devices once the pore has been formed. We have used fully atomistic molecular dynamics (MD) simulations to characterize the cytolysin A (ClyA) protein pores modified with fifth generation (G5) PAMAM dendrimers. Our results show that the PAMAM dendrimer, in either its protonated (P) or non-protonated (NP) states can spontaneously enter the protein lumen. Protonated dendrimers interact strongly with the negatively charged protein pore lumen. As a consequence, P dendrimers assume a more expanded configuration efficiently blocking the pore when compared with the more compact configuration adopted by the neutral NP dendrimers creating a greater void space for the passage of water and ions. To quantify the effective blockage of the protein pore, we have calculated the pore conductance as well as the residence times by applying a weak force on the ions/water. Ionic currents are reduced by 91% for the P dendrimers and 31% for the NP dendrimers. The preferential binding of Cl- counter ions to the P dendrimer creates a zone of high Cl- concentration in the vicinity of the internalized dendrimer and a high concentration of K+ ions in the transmembrane region of the pore lumen. In addition to steric effects, this induced charge segregation for the P dendrimer effectively blocks ionic transport through the pore. Our investigation shows that the bio-compatible PAMAM dendrimers can potentially be used to develop therapeutic protocols based on the pH sensitive gating of pores formed by pore forming toxins to mitigate bacterial infections.Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent

  2. Evidence of guest encapsulation within G8 and G10 dendrimers using NMR techniques.

    Science.gov (United States)

    Shao, Naimin; Dai, Tianjiao; Liu, Yan; Li, Lei; Cheng, Yiyun

    2014-12-07

    Encapsulation of guest molecules within the interior cavities of dendrimers is promising, but high generation dendrimers show limited encapsulation capacity due to their dense surface shell. Here, for the first time, we prove that high generation polyamidoamine dendrimers, such as generation 8 and generation 10, are able to encapsulate hydrophobic guests using NMR spectroscopy. Guest molecules such as phenylbutazone, dexamethasone sodium phosphate and 9-anthracenecarboxylic acid with molecular weights up to 516 Da are in close proximity to the interior scaffold protons of high generation dendrimers. This encapsulation behavior depends on guest hydrophobicity. Chemical defects and back-folding of terminal groups make it possible for these guest molecules to penetrate through the dense surface shell of high generation dendrimers. These results provide new insights into the host-guest chemistry of dendrimers.

  3. Synthesis and self-assembly of PAMAM/PAA Janus dendrimers

    Science.gov (United States)

    Gao, Chunmei; Liu, Mingzhu; Lü, Shaoyu; Zhang, Xinjie; Chen, Yuanmou

    2014-03-01

    Janus dendrimers have two differently functionalized segments which are located on opposite sides. They have many excellent properties and broad application prospects. In this study, poly(amido amine)/poly(acrylic acid) (PAMAM/PAA) Janus dendrimers were prepared by click chemistry. One of the first steps taken was the synthesis of N-Boc-G3.0 PAMAM dendrimers with primary amine groups at the periphery. Second, by amide coupling between propargylic acid and N-Boc-G3.0 PAMAM, PAMAM dendrimers with alkyne were successfully synthesized. After being dissolved in aqueous solutions with different pH, Janus dendrimers spontaneously form flowerlike micellar, Janus particles, and spherical micelles due to primary amino, tertiary amino, and carboxyl groups in the dendrimers. This self-assembly behavior depending on pH changes has a number of potential applications in the field of materials.

  4. Diffusion of Alexa Fluor 488-conjugated dendrimers in rat aortic tissue.

    Science.gov (United States)

    Cho, Brenda S; Roelofs, Karen J; Majoros, Istvan J; Baker, James R; Stanley, James C; Henke, Peter K; Upchurch, Gilbert R

    2006-11-01

    In this study, the distribution of labeled dendrimers in native and aneurysmal rat aortic tissue was examined. Adult male rats underwent infrarenal aorta perfusion with generation 5 (G5) acetylated Alexa Fluor 488-conjugated dendrimers for varying lengths of time. In a second set of experiments, rats underwent aortic elastase perfusion followed by aortic dendrimer perfusion 7 days later. Aortic diameters were measured prior to and postelastase perfusion, and again on the day of harvest. Aortas were harvested 0, 12, or 24 h postperfusion, fixed, and mounted. Native aortas were harvested and viewed as negative controls. Aortic cross-sections were viewed and imaged using confocal microscopy. Dendrimers were quantified (counts/high-powered field). Results were evaluated by repeated measures ANOVA and Student's t-test. We found that in native aortas, dendrimers penetrated the aortic wall in all groups. For all perfusion times, fewer dendrimers were present as time between dendrimer perfusion and aortic harvest increased. Longer perfusion times resulted in increased diffusion of dendrimers throughout the aortic wall. By 24 h, the majority of the dendrimers were through the wall. Dendrimers in aneurysmal aortas, on day 0 postdendrimer perfusion, diffused farther into the aortic wall than controls. In conclusion, this study documents labeled dendrimers delivered intra-arterially to native rat aortas in vivo, and the temporal diffusion of these molecules within the aortic wall. Increasing perfusion time and length of time prior to harvest resulted in continued dendrimer diffusion into the aortic wall. These preliminary data provide a novel mechanism whereby local inhibitory therapy may be delivered locally to aortic tissue.

  5. Study on tunable resonator using a cantilevered carbon nanotube encapsulating a copper nanocluster

    Science.gov (United States)

    Kang, Jeong Won; Kim, Ki-Sub; Park, Jungchul; Hwang, Ho Jung

    2011-02-01

    We investigated an ultrahigh frequency carbon nanotube resonator encapsulating a nanocluster, as another tunable resonator, via classical molecular dynamics simulations and continuum models. The fundamental frequency of cantilevered carbon nanotube resonator encapsulating a copper nanocluster could be adjusted by controlling the position of the encapsulated copper nanocluster. Data obtained from the molecular dynamics simulations were analyzed with continuum theory, and we found that statistically the change in the effective mass factor was greatly correlated with the position change of the encapsulated nanocluster.

  6. Size dependence of thermoelectric power of Au, Pd, Pt nanoclusters deposited onto HOPG surface

    OpenAIRE

    Borisyuk, P. V.; V. I. Troyan; Lebedinskii, Yu Yu; Vasilyev, O S

    2016-01-01

    The paper presents the study of tunnel current-voltage characteristics of Au, Pd and Pt nanoclusters deposited onto the highly oriented pyrolytic graphite (HOPG) surface by pulsed laser deposition. The analysis of tunnel current-voltage characteristics obtained by scanning tunneling spectroscopy (STS) allowed to recover the thermoelectric power value of nanoclusters. It was found that the value of thermoelectric power of pulsed laser deposited nanoclusters depends on nanocluster material and ...

  7. Modelling nano-clusters and nucleation.

    Science.gov (United States)

    Catlow, C Richard A; Bromley, Stefan T; Hamad, Said; Mora-Fonz, Miguel; Sokol, Alexey A; Woodley, Scott M

    2010-01-28

    We review the growing role of computational techniques in modelling the structures and properties of nano-particulate oxides and sulphides. We describe the main methods employed, including those based on both electronic structure and interatomic potential approaches. Particular attention is paid to the techniques used in searching for global minima in the energy landscape defined by the nano-particle cluster. We summarise applications to the widely studied ZnO and ZnS systems, to silica nanochemistry and to group IV oxides including TiO(2). We also consider the special case of silica cluster chemistry in solution and its importance in understanding the hydrothermal synthesis of microporous materials. The work summarised, together with related experimental studies, demonstrates a rich and varied nano-cluster chemistry for these materials.

  8. Silver Nanocluster Reparative Effect in Hernioplasty

    Directory of Open Access Journals (Sweden)

    Nikolay M. Anichkov

    2014-06-01

    Full Text Available Background: The acceleration of re-epithelialization and fibroblast differentiation were noted during the experiments with silver nanoclusters (SNs by interrupting the negative development of inflammation at the level of cytokines and promoting a positive course of reparative processes. The aim of this work was to elaborate the experimental model of prosthesis hernioplasty in subcutaneous and intraperitoneal locations of hernioprostheses with SNs, which allowed us to study the course of reparative reactions in all layers of the anterior abdominal wall. Material and Methods: We used a modified hernioprosthesis made from polyester fibers coated with a metal-polymer composition, including the stabilized SN in a concentration of 6.8 and 11.3 mg per 1 g of the hernioprosthesis mesh. During this research we used guinea pigs to study the in vivo tissue reactions. The clinical part of the study included the group of 212 patients who underwent removal of an inguinal hernia. We have identified various factors associated with infectious and toxic effects on the body by determining the level of the serum glutamate-pyruvate-transaminase (SGPT. Results: In implantation of the hernioprostheses, including the high concentration of SN in the laparotomy wound, the exudative component of the inflammation was weakly expressed. It was mostly the proliferative changes that took place. We did not find either CD8-positive type T lymphocytes or PAX5-positive type B activated cells in the exudate. Conclusion: Our research has shown that the use of hernioprostheses that include silver nanoclusters leads to the reduction of inflammation in the exudative phase and to a more favorable course of reparative processes.

  9. Multiscale Modeling of Dendrimers and Their Interactions with Bilayers and Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Ronald G. Larson

    2009-01-01

    Full Text Available Recent advances in molecular dynamics simulation methodologies and computational power have allowed accurate predictions of dendrimer size, shape, and interactions with bilayers and polyelectrolytes with modest computational effort. Atomistic and coarse-grained (CG models show strong interactions of cationic dendrimers with lipid bilayers. The CG simulations with explicit lipid and water capture bilayer penetration and pore formation, showing that pore formation is enhanced at high dendrimer concentration, but suppressed at low temperature and high salt concentration, in agreement with experiments. Cationic linear polymers have also been simulated, but do not perforate membranes, evidently because by deforming into a pancake, the charges on a linear polymer achieve intimate contact with a single bilayer leaflet. The relatively rigid dendrimers, on the other hand, penetrate the bilayer, because only by interacting with both leaflets can they achieve a similar degree of contact between charged groups. Also, a “dendrimer-filled vesicle” structure for the dendrimer-membrane interaction is predicted by mesoscale thermodynamic simulations, in agreement with a picture derived from experimental observations. In simulations of complexes of dendrimer and polyelectrolyte, anionic linear chains wrap around the cationic dendrimer and penetrate inside it. Overall, these new results indicate that simulations can now provide predictions in excellent agreement with experimental observations, and provide atomic-scale insights into dendrimer structure and dynamics.

  10. Novel PH Sensitive Nanocarrier Agents Based on Citric Acid Dendrimers Containing Conjugated β-Cyclodextrins

    Directory of Open Access Journals (Sweden)

    Hassan Namazi

    2011-06-01

    Full Text Available Introduction: In this work, the use of β-cyclodextrine (β-CD-modified dendrimers as a nanocapsule with a biocompatible shell have studied. β-CD-modified dendrimers have designed and synthesized to enhance the loading capacity of the final dendrimers with encapsulation properties. Methods: To achieve β-CD-modified dendrimers, first citric acid dendrimers were synthesized and then the end functional groups of dendrimers were grafted to β-CD through ester linkages. The molecular structures of resulted dendrimers were verified using common spectroscopic methods such as 1H NMR, FT-IR and the diameters of obtained nanocarriers were evaluated with using dynamic light scattering (DLS experiments. The isolated dendrimers were utilized as the drug delivery agents and the encapsulation and the controlled release of guest drug molecule Naltrexone (NLX was investigated in different pH’s using UV spectroscopy method. Results: It was established that the loading capacity of dendrimers depend on several factors such as their generation and the structure and number of conjugated modifier end groups. Conclusion: Increasing in the number of branches and the size of interior voids and number of conjugated β-CDs cause to enhance the loading capacity.

  11. Poly(amidoamine) (PAMAM) dendrimers: from biomimicry to drug delivery and biomedical applications.

    Science.gov (United States)

    Esfand, R; Tomalia, D A.

    2001-04-01

    Poly(amidoamine) (PAMAM) dendrimers are the first complete dendrimer family to be synthesized, characterized and commercialized. Based on this extensive activity, they are recognized as a unique new class of synthetic nanostructures. Dendrimers allow the precise control of size, shape and placement of functional groups that is desirable for many life science applications. From this perspective, this review focuses on crucial properties of biomimetic dendrimers that will broaden the potential for their use as macromolecular vectors in novel drug delivery and biomedical applications.

  12. Preparation and Biophysical Characterization of Poly(amidoamine) Dendrimer-Poly(acrylic acid) Graft.

    Science.gov (United States)

    Dung, Tran Huu; Do, Le Thanh; Loan, Ta Thi; Yoo, Hoon

    2015-01-01

    A series of PAMAM dendrimer generation 5-poly(acrylic acid) grafts were prepared to evaluate the potential use of dendritic grafts as a drug encapsulated nanocarrier. The structural features of the synthesized polymer graft were identified by FT-IR and 1H-NMR spectra and the biophysical properties were characterized by measuring its particle size and zeta potential. The prepared dendrimer G5-PAA grafts had particle size in the range of 600 to 900 nm and the size increased proportionally with the number of PAA on dendrimer surface. The electrostatic property of the dendrimer G5-PAA, carried out by HPLC reversed phase column analysis and the measurement of zeta potential, revealed that both migration time and zeta potential were dependent on the number of grafted PAA. The number of free amino groups on dendrimer G5-PAA, determined quantitatively by fluorescamine assay, was in a reverse order with the reaction mole ratio of dendrimer to PAA. In addition, dendrimer G5-PAA showed a pH-dependent solubility in aqueous solution with characteristic pH region of solubility, depending on the dendrimer generation. The observed biophysical properties indicate that PAMAM dendrimer G5-PAA is promising as a drug encapsulated nanocarrier.

  13. Rendering poly(amidoamine) or poly(propylenimine) dendrimers temperature sensitive.

    Science.gov (United States)

    Haba, Yasuhiro; Harada, Atsushi; Takagishi, Toru; Kono, Kenji

    2004-10-13

    The poly(amidoamine) dendrimers having terminal isobutyramide (IBAM) groups were prepared by the reaction of isobutyric acid and the amine-terminated poly(amidoamine) dendrimers with generations (G) of 2 to 5 by using a condensing agent, 1,3-dicyclohexylcarbodiimide. 1H and 13C NMR revealed that an IBAM group was attached to essentially every chain end of the dendrimers. While the IBAM-terminated G2 dendrimer was soluble in water, the IBAM-terminated G3, G4, and G5 dendrimers exhibited the lower critical solution temperatures (LCSTs) at 75, 61, and 43 degrees C, respectively. Because the density of the terminal IBAM groups in the periphery of the dendrimer progressively increases with increasing dendrimer generation, the interaction of the IBAM groups might take place more efficiently, resulting in a remarkable decrease in the LCST. In addition, attachment of IBAM groups to poly(propylenimine) dendrimers could give the temperature-sensitive property, indicating that this is an efficient method to render dendrimers temperature sensitive.

  14. Synthesis of crystalline Ge nanoclusters in PE-CVD-deposited SiO2 films

    DEFF Research Database (Denmark)

    Leervad Pedersen, T.P.; Skov Jensen, J.; Chevallier, J.

    2005-01-01

    The synthesis of evenly distributed Ge nanoclusters in plasma-enhanced chemical-vapour-deposited (PE-CVD) SiO2 thin films containing 8 at. % Ge is reported. This is of importance for the application of nanoclusters in semiconductor technology. The average diameter of the Ge nanoclusters can...

  15. Transcorneal iontophoresis of dendrimers: PAMAM corneal penetration and dexamethasone delivery.

    Science.gov (United States)

    Souza, Joel G; Dias, Karina; Silva, Silas A M; de Rezende, Lucas C D; Rocha, Eduardo M; Emery, Flavio S; Lopez, Renata F V

    2015-02-28

    Iontophoresis of nanocarriers in the eye has been proposed to sustain drug delivery and maintain therapeutic concentrations. Fourth generation polyamidoamine (PAMAM) dendrimers are semi-rigid nanoparticles with surface groups that are easily modified. These dendrimers are known to modulate tight junctions, increase paracellular transport of small molecules and be translocated across epithelial barriers, exhibiting high uptake by different cell lines. The first aim of this study was to investigate the effect of iontophoresis on PAMAM penetration and distribution into the cornea. The second aim was to evaluate, ex vivo and in vivo, the effect of these dendrimers in dexamethasone (Dex) transcorneal iontophoresis. Anionic (PAMAM G3.5) and cationic (PAMAM G4) dendrimers were labeled with fluorescein isothiocyanate (FITC), and their distribution in the cornea was investigated using confocal microscopy after ex vivo anodal and cathodal iontophoresis for various application times. The particle size distribution and zeta potential of the dendrimers in an isosmotic solution were determined using dynamic light scattering and Nanoparticle Tracking Analysis (NTA), where the movement of small particles and the formation of large aggregates, from 5 to 100 nm, could be observed. Transcorneal iontophoresis increased the intensity and depth of PAMAM-FITC fluorescence in the cornea, suggesting improved transport of the dendrimers across the epithelium toward the stroma. PAMAM complexes with Dex were characterized by (13)C-NMR, (1)H-NMR and DOSY. PAMAM G3.5 and PAMAM G4 increased the aqueous solubility of Dex by 10.3 and 3.9-fold, respectively; however, the particle size distribution and zeta potential remained unchanged. PAMAM G3.5 decreased the Dex diffusion coefficient 48-fold compared with PAMAM G4. The ex vivo studies showed that iontophoresis increased the amount of Dex that penetrated into the cornea by 2.9, 5.6 and 3.0-fold for Dex, Dex-PAMAM G4 and Dex-PAMAM G3

  16. In Silico Characterization of the Binding Affinity of Dendrimers to Penicillin-Binding Proteins (PBPs): Can PBPs be Potential Targets for Antibacterial Dendrimers?

    Science.gov (United States)

    Ahmed, Shaimaa; Vepuri, Suresh B; Ramesh, Muthusamy; Kalhapure, Rahul; Suleman, Nadia; Govender, Thirumala

    2016-04-01

    We have shown that novel silver salts of poly (propyl ether) imine (PETIM) dendron and dendrimers developed in our group exhibit preferential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus. This led us to examine whether molecular modeling methods could be used to identify the key structural design principles for a bioactive lead molecule, explore the mechanism of binding with biological targets, and explain their preferential antibacterial activity. The current article reports the conformational landscape as well as mechanism of binding of generation 1 PETIM dendron and dendrimers to penicillin-binding proteins (PBPs) in order to understand the antibacterial activity profiles of their silver salts. Molecular dynamics at different simulation protocols and conformational analysis were performed to elaborate on the conformational features of the studied dendrimers, as well as to create the initial structure for further binding studies. The results showed that for all compounds, there were no significant conformational changes due to variation in simulation conditions. Molecular docking calculations were performed to investigate the binding theme between the studied dendrimers and PBPs. Interestingly, in significant accordance with the experimental data, dendron and dendrimer with aliphatic cores were found to show higher activity against S. aureus than the dendrimer with an aromatic core. The latter showed higher activity against MRSA. The findings from this computational and molecular modeling report together with the experimental results serve as a road map toward designing more potent antibacterial dendrimers against resistant bacterial strains.

  17. Comparative toxicological assessment of PAMAM and thiophosphoryl dendrimers using embryonic zebrafish

    Directory of Open Access Journals (Sweden)

    Pryor JB

    2014-04-01

    Full Text Available Joseph B Pryor,1 Bryan J Harper,1 Stacey L Harper1,21Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, USA; 2School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, USAAbstract: Dendrimers are well-defined, polymeric nanomaterials currently being investigated for biomedical applications such as medical imaging, gene therapy, and tissue targeted therapy. Initially, higher generation (size dendrimers were of interest because of their drug carrying capacity. However, increased generation was associated with increased toxicity. The majority of studies exploring dendrimer toxicity have focused on a small range of materials using cell culture methods, with few studies investigating the toxicity across a wide range of materials in vivo. The objective of the present study was to investigate the role of surface charge and generation in dendrimer toxicity using embryonic zebrafish (Danio rerio as a model vertebrate. Due to the generational and charge effects observed at the cellular level, higher generation cationic dendrimers were hypothesized to be more toxic than lower generation anionic or neutral dendrimers with the same core composition. Polyamidoamine (PAMAM dendrimers elicited significant morbidity and mortality as generation was decreased. No significant adverse effects were observed from the suite of thiophosphoryl dendrimers studied. Exposure to ≥50 ppm cationic PAMAM dendrimers G3-amine, G4-amine, G5-amine, and G6-amine caused 100% mortality by 24 hours post-fertilization. Cationic PAMAM G6-amine at 250 ppm was found to be statistically more toxic than both neutral PAMAM G6-amidoethanol and anionic PAMAM G6-succinamic acid at the same concentration. The toxicity observed within the suite of varying dendrimers provides evidence that surface charge may be the best indicator of dendrimer toxicity. Dendrimer class and generation are other potential

  18. NanoClusters Enhance Drug Delivery in Mechanical Ventilation

    Science.gov (United States)

    Pornputtapitak, Warangkana

    The overall goal of this thesis was to develop a dry powder delivery system for patients on mechanical ventilation. The studies were divided into two parts: the formulation development and the device design. The pulmonary system is an attractive route for drug delivery since the lungs have a large accessible surface area for treatment or drug absorption. For ventilated patients, inhaled drugs have to successfully navigate ventilator tubing and an endotracheal tube. Agglomerates of drug nanoparticles (also known as 'NanoClusters') are fine dry powder aerosols that were hypothesized to enable drug delivery through ventilator circuits. This Thesis systematically investigated formulations of NanoClusters and their aerosol performance in a conventional inhaler and a device designed for use during mechanical ventilation. These engineered powders of budesonide (NC-Bud) were delivered via a MonodoseRTM inhaler or a novel device through commercial endotracheal tubes, and analyzed by cascade impaction. NC-Bud had a higher efficiency of aerosol delivery compared to micronized stock budesonide. The delivery efficiency was independent of ventilator parameters such as inspiration patterns, inspiration volumes, and inspiration flow rates. A novel device designed to fit directly to the ventilator and endotracheal tubing connections and the MonodoseRTM inhaler showed the same efficiency of drug delivery. The new device combined with NanoCluster formulation technology, therefore, allowed convenient and efficient drug delivery through endotracheal tubes. Furthermore, itraconazole (ITZ), a triazole antifungal agent, was formulated as a NanoCluster powder via milling (top-down process) or precipitation (bottom-up process) without using any excipients. ITZ NanoClusters prepared by wet milling showed better aerosol performance compared to micronized stock ITZ and ITZ NanoClusters prepared by precipitation. ITZ NanoClusters prepared by precipitation methods also showed an amorphous state

  19. Effect of Terminal Groups of Dendrimers in the Complexation with Antisense Oligonucleotides and Cell Uptake

    Science.gov (United States)

    Márquez-Miranda, Valeria; Peñaloza, Juan Pablo; Araya-Durán, Ingrid; Reyes, Rodrigo; Vidaurre, Soledad; Romero, Valentina; Fuentes, Juan; Céric, Francisco; Velásquez, Luis; González-Nilo, Fernando D.; Otero, Carolina

    2016-02-01

    Poly(amidoamine) dendrimers are the most recognized class of dendrimer. Amino-terminated (PAMAM-NH2) and hydroxyl-terminated (PAMAM-OH) dendrimers of generation 4 are widely used, since they are commercially available. Both have different properties, mainly based on their different overall charges at physiological pH. Currently, an important function of dendrimers as carriers of short single-stranded DNA has been applied. These molecules, known as antisense oligonucleotides (asODNs), are able to inhibit the expression of a target mRNA. Whereas PAMAM-NH2 dendrimers have shown to be able to transfect plasmid DNA, PAMAM-OH dendrimers have not shown the same successful results. However, little is known about their interaction with shorter and more flexible molecules such as asODNs. Due to several initiatives, the use of these neutral dendrimers as a scaffold to introduce other functional groups has been proposed. Because of its low cytotoxicity, it is relevant to understand the molecular phenomena involving these types of dendrimers. In this work, we studied the behavior of an antisense oligonucleotide in presence of both types of dendrimers using molecular dynamics simulations, in order to elucidate if they are able to form stable complexes. In this manner, we demonstrated at atomic level that PAMAM-NH2, unlike PAMAM-OH, could form a well-compacted complex with asODN, albeit PAMAM-OH can also establish stable interactions with the oligonucleotide. The biological activity of asODN in complex with PAMAM-NH2 dendrimer was also shown. Finally, we revealed that in contact with PAMAM-OH, asODN remains outside the cells as TIRF microscopy results showed, due to its poor interaction with this dendrimer and cell membranes.

  20. Effect of Terminal Groups of Dendrimers in the Complexation with Antisense Oligonucleotides and Cell Uptake.

    Science.gov (United States)

    Márquez-Miranda, Valeria; Peñaloza, Juan Pablo; Araya-Durán, Ingrid; Reyes, Rodrigo; Vidaurre, Soledad; Romero, Valentina; Fuentes, Juan; Céric, Francisco; Velásquez, Luis; González-Nilo, Fernando D; Otero, Carolina

    2016-12-01

    Poly(amidoamine) dendrimers are the most recognized class of dendrimer. Amino-terminated (PAMAM-NH2) and hydroxyl-terminated (PAMAM-OH) dendrimers of generation 4 are widely used, since they are commercially available. Both have different properties, mainly based on their different overall charges at physiological pH. Currently, an important function of dendrimers as carriers of short single-stranded DNA has been applied. These molecules, known as antisense oligonucleotides (asODNs), are able to inhibit the expression of a target mRNA. Whereas PAMAM-NH2 dendrimers have shown to be able to transfect plasmid DNA, PAMAM-OH dendrimers have not shown the same successful results. However, little is known about their interaction with shorter and more flexible molecules such as asODNs. Due to several initiatives, the use of these neutral dendrimers as a scaffold to introduce other functional groups has been proposed. Because of its low cytotoxicity, it is relevant to understand the molecular phenomena involving these types of dendrimers. In this work, we studied the behavior of an antisense oligonucleotide in presence of both types of dendrimers using molecular dynamics simulations, in order to elucidate if they are able to form stable complexes. In this manner, we demonstrated at atomic level that PAMAM-NH2, unlike PAMAM-OH, could form a well-compacted complex with asODN, albeit PAMAM-OH can also establish stable interactions with the oligonucleotide. The biological activity of asODN in complex with PAMAM-NH2 dendrimer was also shown. Finally, we revealed that in contact with PAMAM-OH, asODN remains outside the cells as TIRF microscopy results showed, due to its poor interaction with this dendrimer and cell membranes.

  1. Design, synthesis, characterization and drug release kinetics of PAMAM dendrimer based drug formulations

    Science.gov (United States)

    Kurtoglu, Yunus Emre

    The drug release characteristics of G4-polyamidoamine (PAMAM) dendrimer-ibuprofen conjugates with ester, amide, and peptide linkers were investigated, in addition to a linear PEG-ibuprofen conjugate to understand the effect of architecture and linker on drug release. Ibuprofen was directly conjugated to NH2 -terminated dendrimer by an amide bond and OH-terminated dendrimer by an ester bond. A tetra-peptide linked dendrimer conjugate and a linear mPEG-ibuprofen conjugate were also studied for comparison to direct linked dendrimer conjugates. It is demonstrated that the 3-D nanoscale architecture of PAMAM dendrimer-drug conjugates, along with linking chemistry govern the drug release mechanisms as well as kinetics. Understanding these structural effects on their drug release characteristics is crucial for design of dendrimer conjugates with high efficacy such as poly(amidoamine) dendrimer-N-Acetylcysteine conjugates with disulfide linkages. N-Acetylcysteine (NAC) is an anti-inflammatory agent with significant potential for clinical use in the treatment of neuroinflammation, stroke and cerebral palsy. A poly(amidoamine) dendrimer-NAC conjugate that contains a disulfide linkage was synthesized and evaluated for its release kinetics in the presence of glutathione (GSH), Cysteine (Cys), and bovine serum albumin (BSA) at both physiological and lysosomal pH. FITC-labeled conjugates showed that they enter cells rapidly and localize in the cytoplasm of lipopolysaccharide (LPS)-activated microglial cells. The efficacy of the dendrimer-NAC conjugate was measured in activated microglial cells using reactive oxygen species (ROS) assays. The conjugates showed an order of magnitude increase in anti-oxidant activity compared to free drug. When combined with intrinsic and ligand-based targeting with dendrimers, these types of GSH sensitive nanodevices can lead to improved drug release profiles and in vivo efficacy.

  2. Sodium sensing in neurons with a dendrimer-based nanoprobe.

    Science.gov (United States)

    Lamy, Christophe M; Sallin, Olivier; Loussert, Céline; Chatton, Jean-Yves

    2012-02-28

    Ion imaging is a powerful methodology to assess fundamental biological processes in live cells. The limited efficiency of some ion-sensing probes and their fast leakage from cells are important restrictions to this approach. In this study, we present a novel strategy based on the use of dendrimer nanoparticles to obtain better intracellular retention of fluorescent probes and perform prolonged fluorescence imaging of intracellular ion dynamics. A new sodium-sensitive nanoprobe was generated by encapsulating a sodium dye in a PAMAM dendrimer nanocontainer. This nanoprobe is very stable and has high sodium sensitivity and selectivity. When loaded in neurons in live brain tissue, it homogenously fills the entire cell volume, including small processes, and stays for long durations, with no detectable alterations of cell functional properties. We demonstrate the suitability of this new sodium nanosensor for monitoring physiological sodium responses such as those occurring during neuronal activity.

  3. Photoinduced electron transfer between benzyloxy dendrimer phthalocyanine and benzoquinone

    Science.gov (United States)

    Zhang, Tiantian; Ma, Dongdong; Pan, Sujuan; Wu, Shijun; Jiang, Yufeng; Zeng, Di; Yang, Hongqin; Peng, Yiru

    2016-10-01

    Photo-induced electron transfer (PET) is an important and fundamental process in natural photosynthesis. To mimic such interesting PET process, a suitable donor and acceptor couple were properly chosen. Dendrimer phthalocyanines and their derivatives have emerged as promising materials for artificial photosynthesis systems. In this paper, the electron transfer between the light harvest dendrimer phthalocyanine (donor) and the 1,4-benzoquinone (acceptor) was studied by UV/Vis and fluorescence spectroscopic methods. It was found that fluorescence of phthalocyanine was quenched by benzoquinone (BQ) via excited state electron transfer, from the phthalocyanine to the BQ upon excitation at 610 nm. The Stern-Volmer constant (KSV) of electron transfer was calculated. Our study suggests that this dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential artificial photosynthesis system.

  4. Understanding Peptide Dendrimer Interactions with Model Cell Membrane Mimics

    DEFF Research Database (Denmark)

    Lind, Tania Kjellerup

    membranes or highly conserved motifs, effectively making resistance due to mutations less likely to develop and spread. For this we studied the conditions to form supported lipid bilayers with basic systems and further established a protocol for producing biomimetic bacterial model membranes via the vesicle...... fusion method, which presents improved means for studying drug-membrane interactions in the future. The interaction mechanism of a family of dendrimers was examined and in particular one dendrimer (BALY) was extensively studied by the combined use of quartz crystal microbalance, atomic force microscopy...... and neutron reection. The application of several complementary surface-sensitive techniques allowed for systematically addressing the interface-related processes and gain insights into different aspects of the interaction. BALY was found to interact via a uidity-dependent mechanism. It inserted into the outer...

  5. Relaxation path of metastable nanoclusters in oxide dispersion strengthened materials

    Science.gov (United States)

    Ribis, J.; Thual, M. A.; Guilbert, T.; de Carlan, Y.; Legris, A.

    2017-02-01

    ODS steels are a promising class of structural materials for sodium cooled fast reactor application. The ultra-high density of the strengthening nanoclusters dispersed within the ferritic matrix is responsible of the excellent creep properties of the alloy. Fine characterization of the nanoclusters has been conducted on a Fe-14Cr-0.3Ti-0.3Y2O3 ODS material using High Resolution and Energy Filtered Transmission Electron Microscopy. The nanoclusters exhibit a cubic symmetry possibly identified as f.c.c and display a non-equilibrium YTiCrO chemical composition thought to be stabilized by a vacancy supersaturation. These nanoclusters undergo relaxation towards the Y2Ti2O7-like state as they grow. A Cr shell is observed around the relaxed nano-oxides, this size-dependent shell may form after the release of Cr by the particles. The relaxation energy barrier appears to be higher for the smaller particles probably owing to a volume/surface ratio effect in reason to the full coherency of the nanoclusters.

  6. Hydrogels for osteochondral repair based on photocrosslinkable carbamate dendrimers.

    Science.gov (United States)

    Degoricija, Lovorka; Bansal, Prashant N; Söntjens, Serge H M; Joshi, Neel S; Takahashi, Masaya; Snyder, Brian; Grinstaff, Mark W

    2008-10-01

    First generation, photocrosslinkable dendrimers consisting of natural metabolites (i.e., succinic acid, glycerol, and beta-alanine) and nonimmunogenic poly(ethylene glycol) (PEG) were synthesized divergently in high yields using ester and carbamate forming reactions. Aqueous solutions of these dendrimers were photocrosslinked with an eosin-based photoinitiator to afford hydrogels. The hydrogels displayed a range of mechanical properties based on their structure, generation size, and concentration in solution. All of the hydrogels showed minimal swelling characteristics. The dendrimer solutions were then photocrosslinked in situ in an ex vivo rabbit osteochondral defect (3 mm diameter and 10 mm depth), and the resulting hydrogels were subjected to physiologically relevant dynamic loads. Magnetic resonance imaging (MRI) showed the hydrogels to be fixated in the defect site after the repetitive loading regimen. The ([G1]-PGLBA-MA) 2-PEG hydrogel was chosen for the 6 month pilot in vivo rabbit study because this hydrogel scaffold could be prepared at low polymer weight (10 wt %) and possessed the largest compressive modulus of the 10% formulations, a low swelling ratio, and contained carbamate linkages, which are more hydrolytically stable than the ester linkages. The hydrogel-treated osteochondral defects showed good attachment in the defect site and histological analysis showed the presence of collagen II and glycosaminoglycans (GAGs) in the treated defects. By contrast, the contralateral unfilled defects showed poor healing and negligible GAG or collagen II production. Good mechanical properties, low swelling, good attachment to the defect site, and positive in vivo results illustrate the potential of these dendrimer-based hydrogels as scaffolds for osteochondral defect repair.

  7. Controlling Androgen receptor nuclear localization by dendrimer conjugates

    Science.gov (United States)

    Wang, Haoyu

    Androgen Receptor (AR) antagonists, such as bicalutamide and flutamide have been used widely in the treatment of prostate cancer. Although initial treatment is effective, prostate cancer cells often acquire antiandrogen resistance with prolonged treatment. AR over-expression and AR mutations contribute to the development of antiandrogen resistant cancer. Second generation antiandrogens such as enzalutamide are more effective and show reduced AR nuclear localization. In this study, derivatives of PAN52, a small molecule antiandrogen previously developed in our lab, were conjugated to the surface of generation 4 and generation 6 PAMAM dendrimers to obtain antiandrogen PAMAM dendrimer conjugates (APDC). APDCs readily enter cells and associate with AR in the cytoplasm. Due to their large size and positive charge, they can not enter the nucleus, thus retaining AR in the cytoplasm. In addition, APDCs are effective in decreasing AR mediated transcription and cell proliferation. APDC is the first AR antagonists that inhibit DHT-induced nuclear localization of AR. By inhibiting AR nuclear localization, APDC represents a new class of antiandrogens that offer an alternative approach to addressing antiandrogen-resistant prostate cancer. Lysine post-translational modification of AR Nuclear Localization Sequence (NLS) has great impact on AR cellular localization. It is of interest to understand which modifications modulate AR translocation into the nucleus. In this study, we prepared dendrimer-based acetyltransferase mimetic (DATM), DATM is able to catalytically acetylate AR in CWR22Rv1 cells, which will be a useful tool for studying AR modification effect on AR cellular localization. Derivatives of DATM, which transfer other chemical groups to AR, can be prepared similarly, and with more dendrimer based AR modification tools prepared in future, we will be able to understand and control AR cellular localization through AR modification.

  8. A New Convergent Approach to Unsymmetrically Branched Polyether Dendrimers

    Institute of Scientific and Technical Information of China (English)

    GAO; Xiaoping

    2001-01-01

    Dendrimers are perfect monodisperse macromolecules with a regular and highly branched three-dimensional architecture. The combination of discrete numbers of functionality in one molecular and high densities of active groups, typical for dendritic molecules, has attracted a lot of attention in the fields of medicinal chenistry (e.g. in drug delivery system), host-guest chemistry and catalysis chemistry[1].  ……

  9. Design and Evaluation of Tumor-Specific Dendrimer Epigenetic Therapeutics

    Science.gov (United States)

    Zong, Hong; Shah, Dhavan; Selwa, Katherine; Tsuchida, Ryan E; Rattan, Rahul; Mohan, Jay; Stein, Adam B; Otis, James B; Goonewardena, Sascha N

    2015-01-01

    Histone deacetylase inhibitors (HDACi) are promising therapeutics for cancer. HDACi alter the epigenetic state of tumors and provide a unique approach to treat cancer. Although studies with HDACi have shown promise in some cancers, variable efficacy and off-target effects have limited their use. To overcome some of the challenges of traditional HDACi, we sought to use a tumor-specific dendrimer scaffold to deliver HDACi directly to cancer cells. Here we report the design and evaluation of tumor-specific dendrimer–HDACi conjugates. The HDACi was conjugated to the dendrimer using an ester linkage through its hydroxamic acid group, inactivating the HDACi until it is released from the dendrimer. Using a cancer cell model, we demonstrate the functionality of the tumor-specific dendrimer–HDACi conjugates. Furthermore, we demonstrate that unlike traditional HDACi, dendrimer–HDACi conjugates do not affect tumor-associated macrophages, a recently recognized mechanism through which drug resistance emerges. We anticipate that this new class of cell-specific epigenetic therapeutics will have tremendous potential in the treatment of cancer. PMID:26246996

  10. Partially PEGylated PAMAM dendrimers as solubility enhancers of Silybin.

    Science.gov (United States)

    Diaz, Carola; Guzmán, José; Jiménez, Verónica A; Alderete, Joel B

    2017-04-19

    PEGylated PAMAM-G4 dendrimers with substitution percentages of 50% and intermediate size PEG chains (0.55 and 2.0 kDa) were synthesized and evaluated as solubility enhancers and potential supramolecular carriers for the poorly soluble drug Silybin (SIL). Aqueous solubility profiles revealed that the PEGylated system with 2.0 kDa chains induced a five-fold solubility increase for SIL and the largest drug-loading capacity within the systems under study with an average complex stoichiometry of 71:1 according to the Higuchi-Connors formulation for multiple binding sites. The supramolecular interaction between SIL and PEGylated PAMAM-G4 dendrimers was confirmed by 2D-NOESY experiments, which evidenced the simultaneous complexation of the drug in both PAMAM-G4 branches and outermost PEG chains. In vitro release studies showed that 2.0 kDa PEG chains induced a more extended release time compared with 0.5 kDa PEG chains. This result was attributed to the enhancement of PEG assistance to SIL complexation in systems with longer PEG chains, which are able to self-penetrate into dendrimer cavities and cooperate in the stabilization of SIL complexes, thus delaying the release of SIL from the supramolecular host. These results are valuable for the future design and development of novel PAMAM-based systems for SIL complexation and delivery.

  11. Elasticity of DNA and the effect of Dendrimer Binding

    CERN Document Server

    Mogurampelly, Santosh; Netz, Roland R; Maiti, Prabal K

    2013-01-01

    Negatively charged DNA can be compacted by positively charged dendrimers and the degree of compaction is a delicate balance between the strength of the electrostatic interaction and the elasticity of DNA. We report various elastic properties of short double stranded DNA (dsDNA) and the effect of dendrimer binding using fully atomistic molecular dynamics and numerical simulations. In equilibrium at room temperature, the contour length distribution P(L) and end-to-end distance distribution P(R) are nearly Gaussian, the former gives an estimate of the stretch modulus {\\gamma}_1 of dsDNA in quantitative agreement with the literature value. The bend angle distribution P({\\theta}) of the dsDNA also has a Gaussian form and allows to extract a persistence length, L_p of 43 nm. When the dsDNA is compacted by positively charged dendrimer, the stretch modulus stays invariant but the effective bending rigidity estimated from the end-to-end distance distribution decreases dramatically due to backbone charge neutralization...

  12. Fluorescent Dendrimer Nanoconjugates as Advanced Probes for Biological Imaging

    Science.gov (United States)

    Reilly, Daniel; Kim, Sung Hoon; Katzenellenbogen, John A.; Schroeder, Charles M.

    2014-03-01

    Recent advances in fluorescence microscopy have enabled improvements in spatial resolution for biological imaging. However, there is a strong need for development of advanced fluorescent probes to enable a molecular-scale understanding of biological events. In this work, we report the development of a new class of probes for fluorescence imaging based on dye-conjugated dendrimer nanoconjugates. We utilize molecular-scale dendritic scaffolds as fluorescent probes, thereby enabling conjugation of multiple dyes and linkers to the scaffold periphery. In particular, we use polyamidoamine dendrimers as molecular scaffolds, wherein dye conjugation can be varied over a wide range. Single molecule fluorescence imaging shows that dendrimer nanoconjugates are far brighter than single fluorophores, resulting in increased localization precision. In addition, we further developed a new set of remarkably photostable probes by conjugating photoprotective triplet state quenchers directly onto the dendritic scaffold. We observe large increases in the photobleaching times compared to single dyes and reduced transient dark states (blinking). Overall, we believe that these new probes will allow for single molecule imaging over long time scales, enabling new vistas in biological imaging.

  13. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Directory of Open Access Journals (Sweden)

    Silvia Varela-Aramburu

    2016-09-01

    Full Text Available Gold nanoclusters are small (1–3 nm nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery.

  14. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    Science.gov (United States)

    Varela-Aramburu, Silvia; Wirth, Richard; Lai, Chian-Hui; Orts-Gil, Guillermo

    2016-01-01

    Summary Gold nanoclusters are small (1–3 nm) nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery. PMID:27826501

  15. Dendrimers destabilize proteins in a generation-dependent manner involving electrostatic interactions

    DEFF Research Database (Denmark)

    Gichm, Lise; Christensen, Casper; Boas, Ulrik

    2008-01-01

    Dendrimers are well-defined chemical polymers with a characteristic branching pattern that gives rise to attractive features such as antibacterial and antitumor activities as well as drug delivery properties. In addition, dendrimers can solubilize prion protein aggregates at very low concentratio...

  16. PAMAM dendrimer with 4-carbomethoxypyrrolidone - In vitro assessment of neurotoxicity

    DEFF Research Database (Denmark)

    Janaszewska, Anna; Studzian, Maciej; Petersen, Johannes Fabritius;

    2015-01-01

    Cytotoxicity of cationic amino-terminated PAMAM dendrimer and modified PAMAM-pyrrolidone dendrimer was compared. LDH assay and cell visualization technique were employed. Mouse embryonic hippocampal cells (mHippoE-18) were used. The experiments were performed in FBS-deprived medium. Pyrrolidone-m...

  17. Electron Transfer in Methylene-Blue-Labeled G3 Dendrimers Tethered to Gold

    DEFF Research Database (Denmark)

    Álvarez-Martos, Isabel; Kartashov, Andrey; Ferapontova, Elena

    2016-01-01

    , and their dependence on the dendrimer surface packing, contribute to both mechanistic pathways. Electrical wiring of horse-radish peroxidase and hexose oxidase by using MB-labeled dendrimers allowed the bioelectrocatalytic reduction of H2O2 and oxidation of glucose by these enzymes. The demonstrated electrical...

  18. Expand classical drug administration ways by emerging routes using dendrimer drug delivery systems: a concise overview.

    Science.gov (United States)

    Mignani, Serge; El Kazzouli, Saïd; Bousmina, Mosto; Majoral, Jean-Pierre

    2013-10-01

    Drugs are introduced into the body by numerous routes such as enteral (oral, sublingual and rectum administration), parenteral (intravascular, intramuscular, subcutaneous and inhalation administration), or topical (skin and mucosal membranes). Each route has specific purposes, advantages and disadvantages. Today, the oral route remains the preferred one for different reasons such as ease and compliance by patients. Several nanoformulated drugs have been already approved by the FDA, such as Abelcet®, Doxil®, Abraxane® or Vivagel®(Starpharma) which is an anionic G4-poly(L-lysine)-type dendrimer showing potent topical vaginal microbicide activity. Numerous biochemical studies, as well as biological and pharmacological applications of both dendrimer based products (dendrimers as therapeutic compounds per se, like Vivagel®) and dendrimers as drug carriers (covalent conjugation or noncovalent encapsulation of drugs) were described. It is widely known that due to their outstanding physical and chemical properties, dendrimers afforded improvement of corresponding carried-drugs as dendrimer-drug complexes or conjugates (versus plain drug) such as biodistribution and pharmacokinetic behaviors. The purpose of this manuscript is to review the recent progresses of dendrimers as nanoscale drug delivery systems for the delivery of drugs using enteral, parenteral and topical routes. In particular, we focus our attention on the emerging and promising routes such as oral, transdermal, ocular and transmucosal routes using dendrimers as delivery systems.

  19. Peptide and glycopeptide dendrimer apple trees as enzyme models and for biomedical applications.

    Science.gov (United States)

    Reymond, Jean-Louis; Darbre, Tamis

    2012-02-28

    Solid phase peptide synthesis (SPPS) provides peptides with a dendritic topology when diamino acids are introduced in the sequences. Peptide dendrimers with one to three amino acids between branches can be prepared with up to 38 amino acids (MW ~ 5,000 Da). Larger peptide dendrimers (MW ~ 30,000) were obtained by a multivalent chloroacetyl cysteine (ClAc) ligation. Structural studies of peptide dendrimers by CD, FT-IR, NMR and molecular dynamics reveal molten globule states containing up to 50% of α-helix. Esterase and aldolase peptide dendrimers displaying dendritic effects and enzyme kinetics (k(cat)/k(uncat) ~ 10(5)) were designed or discovered by screening large combinatorial libraries. Strong ligands for Pseudomonas aeruginosa lectins LecA and LecB able to inhibit biofilm formation were obtained with glycopeptide dendrimers. Efficient ligands for cobalamin, cytotoxic colchicine conjugates and antimicrobial peptide dendrimers were also developed showing the versatility of dendritic peptides. Complementing the multivalency, the amino acid composition of the dendrimers strongly influenced the catalytic or biological activity obtained demonstrating the importance of the "apple tree" configuration for protein-like function in peptide dendrimers.

  20. Redox controlled interaction of biferrocenyl-terminated dendrimers with Beta-cyclodextrin molecular printboards

    NARCIS (Netherlands)

    Nijhuis, C.A.; Dolatowska, Karolina A.; Ravoo, B.J.; Huskens, Jurriaan; Reinhoudt, David

    2007-01-01

    This paper describes the synthesis and electrochemistry of biferrocenyl-terminated dendrimers and their β-cyclodextrin (β-CD) inclusion complexes in aqueous solution and at surfaces. Three generations of poly(propylene imine) (PPI) dendrimers, decorated with 4, 8, and 16 biferrocenyl (BFc) units,

  1. Dendrimer nanofluids in the concentrated regime: from polymer melts to soft spheres.

    Science.gov (United States)

    Pilkington, Georgia A; Pedersen, Jan S; Briscoe, Wuge H

    2015-03-24

    Understanding dendrimer structures and their interactions in concentrated solutions is important to a wide range of applications, such as drug delivery and lubrication. However, controversy has persisted concerning whether, when confined to proximity, dendrimers would entangle as observed for polymer systems, or act as deformable spheres. Furthermore, how such behavior may be related to their size-dependent molecular architecture remains unclear. Using small-angle X-ray scattering (SAXS), the intermolecular interactions and structures in aqueous nanofluids containing three generations of carboxyl-terminated poly(amidoamine) (PAMAM) dendrimers (G0.5, Rg = 9.3 Å; G3.5, Rg = 22.6 Å; G5.5, Rg = 39.9 Å, where Rg is the radius of gyration) over a mass fraction range 0.005 ≤ x ≤ 0.316 have been studied. In the highly concentrated regime (x ≥ 0.157), we observe that the solution properties depend on the dendrimer generation. Our results suggest that the smaller G0.5 dendrimers form a highly entangled polymer melt, while the larger dendrimers, G3.5 and G5.5, form densely packed and ordered structures, in which the individual dendrimers exhibit some degree of mutual overlap or deformation. Our results demonstrate the tunability of interdendrimer interactions via their molecular architecture, which in turn may be harnessed to control and tailor the physical properties of dendrimer nanofluids.

  2. Pegylated dendrimer and its effect in fluorouracil loading and release for enhancing antitumor activity.

    Science.gov (United States)

    Ly, Tu Uyen; Tran, Ngoc Quyen; Hoang, Thi Kim Dung; Phan, Kim Ngoc; Truong, Hai Nhung; Nguyen, Cuu Khoa

    2013-02-01

    Dendrimer, a new class of hyper-branched polymer with predetermined molecular weight, is being received much attention in nano biomedical applications such as anticancer drug delivery, gene therapy, disease diagnosis and etc. In this study, polyamidoamine (PAMAM)-based dendrimer generation 3.0 (G 3.0) was synthesized and subsequently pegylated. Obtained results showed that pegylation degree of the dendrimer was around 31% for its external amine groups. TEM image of the pegylated dendrimer exhibited spherical shape and nano sizes ranging from 30 to 40 nm. The fluorouracil (5-FU)-loaded pegylated dendrimer showed a slow release profile of the drug. In vitro study, at the primary screening concentration of 100 microg/mL, the PAMAM dendrimer presented higher toxicity in MCF-7 cells as compared to its pegylated counterpart. Meanwhile, the (5-FU)-loaded pegylated dendrimer exhibited the antiproliferative activity against the cell line with the IC50 of 9.92 +/- 0.19 microg/mL. In vivo tumor xenograft study, we succeeded in generating MCF-7 cells-derived cancer tumors on mice that was well-confirmed by using flow cytometer assay. The 5-FU encapsulated pegylated dendrimer exhibited a significant decrement in volume of the tumors which was generated by MCF-7 cancer cells.

  3. Redox-Controlled Interaction of Biferrocenyl-Terminated Dendrimers with β-Cyclodextrin Molecular Printboards

    NARCIS (Netherlands)

    Nijhuis, Christian A.; Dolatowska, Karolina A.; Ravoo, Bart Jan; Huskens, Jurriaan; Reinhoudt, David N.

    2007-01-01

    This paper describes the synthesis and electrochemistry of biferrocenyl-terminated dendrimers and their β-cyclodextrin (β-CD) inclusion complexes in aqueous solution and at surfaces. Three generations of poly(propylene imine) (PPI) dendrimers, decorated with 4, 8, and 16 biferrocenyl (BFc) units, re

  4. Dendrimer-based organic/inorganic hybrid nanoparticles in biomedical applications

    Science.gov (United States)

    Shen, Mingwu; Shi, Xiangyang

    2010-09-01

    This review reports some recent advances on the synthesis, self-assembly, and biofunctionalization of various dendrimer-based organic/inorganic hybrid nanoparticles (NPs) for various biomedical applications, including but not limited to protein immobilization, gene delivery, and molecular diagnosis. In particular, targeted molecular imaging of cancer using dendrimer-based organic/inorganic hybrid NPs will be introduced in detail.

  5. Unexpected Temperature Behavior of Polyethylene Glycol Spacers in Copolymer Dendrimers in Chloroform

    Science.gov (United States)

    Markelov, Denis A.; Matveev, Vladimir V.; Ingman, Petri; Nikolaeva, Marianna N.; Penkova, Anastasia V.; Lahderanta, Erkki; Boiko, Natalia I.; Chizhik, Vladimir I.

    2016-04-01

    We have studied copolymer dendrimer structure: carbosilane dendrimers with terminal phenylbenzoate mesogenic groups attached by poly(ethylene) glycol (PEG) spacers. In this system PEG spacers are additional tuning to usual copolymer structure: dendrimer with terminal mesogenic groups. The dendrimer macromolecules were investigated in a dilute chloroform solution by 1H NMR methods (spectra and relaxations). It was found that the PEG layer in G = 5 generations dendrimer is “frozen” at high temperatures (above 260 K), but it unexpectedly becomes “unfrozen” at temperatures below 250 K (i.e., melting when cooling). The transition between these two states occurs within a small temperature range (~10 K). Such a behavior is not observed for smaller dendrimer generations (G = 1 and 3). This effect is likely related to the low critical solution temperature (LCST) of PEG and is caused by dendrimer conformations, in which the PEG group concentration in the layer increases with growing G. We suppose that the unusual behavior of PEG fragments in dendrimers will be interesting for practical applications such as nanocontainers or nanoreactors.

  6. Ligand-Induced Stability of Gold Nanoclusters: Thiolate versus Selenolate.

    Science.gov (United States)

    Kurashige, Wataru; Yamaguchi, Masaki; Nobusada, Katsuyuki; Negishi, Yuichi

    2012-09-20

    Thiolate-protected gold nanoclusters have attracted considerable attention as building blocks for new functional materials and have been extensively researched. Some studies have reported that changing the ligand of these gold nanoclusters from thiolate to selenolate increases cluster stability. To confirm this, in this study, we compare the stabilities of precisely synthesized [Au25(SC8H17)18](-) and [Au25(SeC8H17)18](-) against degradation in solution, thermal dissolution, and laser fragmentation. The results demonstrate that changing the ligand from thiolate to selenolate increases cluster stability in reactions involving dissociation of the gold-ligand bond but reduces cluster stability in reactions involving intramolecular dissociation of the ligand. These results reveal that using selenolate ligands makes it possible to produce gold clusters that are more stable against degradation in solution than thiolate-protected gold nanoclusters.

  7. Superconducting state of metallic nanoclusters and Josephson tunneling networks

    Energy Technology Data Exchange (ETDEWEB)

    Kresin, Vladimir, E-mail: vzkresin@lbl.gov [Lawrence Berkeley Laboratory, University of California at Berkeley, CA 94720 (United States); Ovchinnikov, Yurii [L. Landau Institute for Theoretical Physics, RAN, Moscow 117334 (Russian Federation)

    2014-11-15

    Highlights: • Specific nanoclusters form a new family of high T{sub c} superconductors. • For an isolated cluster the pairing affects its energy spectrum. • Nano-based Josephson tunneling network can transfer a macroscopic superconducting current at high temperatures. • A.c. tunneling network can be synchronized and radiates as a single junction. - Abstract: Metallic nanoclusters form a new family of high temperature superconductors. In principle, the value of T{sub c} can be raised up to room temperature. In addition, one can observe the Josephson tunneling between two clusters. One can build the nanocluster-based tunneling network capable to transfer a macroscopic supercurrent at high temperatures. Such a network can be synchronized and radiate as single junction.

  8. Atomic level insights into realistic molecular models of dendrimer-drug complexes through MD simulations

    Science.gov (United States)

    Jain, Vaibhav; Maiti, Prabal K.; Bharatam, Prasad V.

    2016-09-01

    Computational studies performed on dendrimer-drug complexes usually consider 1:1 stoichiometry, which is far from reality, since in experiments more number of drug molecules get encapsulated inside a dendrimer. In the present study, molecular dynamic (MD) simulations were implemented to characterize the more realistic molecular models of dendrimer-drug complexes (1:n stoichiometry) in order to understand the effect of high drug loading on the structural properties and also to unveil the atomistic level details. For this purpose, possible inclusion complexes of model drug Nateglinide (Ntg) (antidiabetic, belongs to Biopharmaceutics Classification System class II) with amine- and acetyl-terminated G4 poly(amidoamine) (G4 PAMAM(NH2) and G4 PAMAM(Ac)) dendrimers at neutral and low pH conditions are explored in this work. MD simulation analysis on dendrimer-drug complexes revealed that the drug encapsulation efficiency of G4 PAMAM(NH2) and G4 PAMAM(Ac) dendrimers at neutral pH was 6 and 5, respectively, while at low pH it was 12 and 13, respectively. Center-of-mass distance analysis showed that most of the drug molecules are located in the interior hydrophobic pockets of G4 PAMAM(NH2) at both the pH; while in the case of G4 PAMAM(Ac), most of them are distributed near to the surface at neutral pH and in the interior hydrophobic pockets at low pH. Structural properties such as radius of gyration, shape, radial density distribution, and solvent accessible surface area of dendrimer-drug complexes were also assessed and compared with that of the drug unloaded dendrimers. Further, binding energy calculations using molecular mechanics Poisson-Boltzmann surface area approach revealed that the location of drug molecules in the dendrimer is not the decisive factor for the higher and lower binding affinity of the complex, but the charged state of dendrimer and drug, intermolecular interactions, pH-induced conformational changes, and surface groups of dendrimer do play an

  9. Lactose-Functionalized Dendrimers Arbitrate the Interaction of Galectin-3/MUC1 Mediated Cancer Cellular Aggregation

    Science.gov (United States)

    Michel, Anna K.; Nangia-Makker, Pratima; Raz, Avraham

    2015-01-01

    By using lactose-functionalized poly(amidoamine) dendrimers as a tunable multivalent platform, we studied cancer cell aggregation in three different cell lines (A549, DU-145, and HT-1080) with galectin-3. We found that small lactose-functionalized G(2)-dendrimer 1 inhibited galectin-3-induced aggregation of the cancer cells. In contrast, dendrimer 4 (a larger, generation 6 dendrimer with 100 carbohydrate end groups) caused cancer cells to aggregate through a galectin-3 pathway. This study indicates that inhibition of cellular aggregation occurred because 1 provided competitive binding sites for galectin-3 (compared to its putative cancer cell ligand, TF-antigen on MUC1). Dendrimer 4, in contrast, provided an excess of ligands for galectin-3 binding; this caused crosslinking and aggregation of cells to be increased. PMID:25138772

  10. Fourier transform infrared spectroscopy (FTIR) characterization of the interaction of anti-cancer photosensitizers with dendrimers.

    Science.gov (United States)

    Dabrzalska, Monika; Benseny-Cases, Nuria; Barnadas-Rodríguez, Ramon; Mignani, Serge; Zablocka, Maria; Majoral, Jean-Pierre; Bryszewska, Maria; Klajnert-Maculewicz, Barbara; Cladera, Josep

    2016-01-01

    The systemic or local administration of a photosensitizer for photodynamic therapy is highly limited by poor selectivity, rapid deactivation and long-lasting skin toxicity due to unfavorable biodistribution. Drug delivery systems based on nanocarriers may help specific and effective delivery of photosensitizers. In the present paper, the interaction of two photosensitizers, methylene blue and rose bengal, with phosphorous cationic and anionic dendrimers as potential nanocarriers, has been characterized. A novel method is presented based on the analysis of the infrared spectra of mixtures of photosensitizer and dendrimer. The capacity of dendrimers to bind the photosensitizers has been evaluated by obtaining the corresponding binding curves. It is shown that methylene blue interacts with both cationic and anionic dendrimers, whereas rose bengal only binds to the cationic ones. Dendrimers are shown to be potential nanocarriers for a specific delivery of both photosensitizers.

  11. Small-angle x-ray scattering study of polymer structure: Carbosilane dendrimers in hexane solution

    Science.gov (United States)

    Shtykova, E. V.; Feigin, L. A.; Volkov, V. V.; Malakhova, Yu. N.; Streltsov, D. R.; Buzin, A. I.; Chvalun, S. N.; Katarzhanova, E. Yu.; Ignatieva, G. M.; Muzafarov, A. M.

    2016-09-01

    The three-dimensional organization of monodisperse hyper-branched macromolecules of regular structure—carbosilane dendrimers of zero, third, and sixth generations—has been studied by small-angle X-ray scattering (SAXS) in solution. The use of modern methods of SAXS data interpretation, including ab initio modeling, has made it possible to determine the internal architecture of the dendrimers in dependence of the generation number and the number of cyclosiloxane end groups (forming the shell of dendritic macromolecules) and show dendrimers to be spherical. The structural results give grounds to consider carbosilane dendrimers promising objects for forming crystals with subsequent structural analysis and determining their structure with high resolution, as well as for designing new materials to be used in various dendrimer-based technological applications.

  12. Dendrimers as a promising tool in ocular therapeutics: Latest advances and perspectives.

    Science.gov (United States)

    Rodríguez Villanueva, Javier; Navarro, Manuel Guzmán; Rodríguez Villanueva, Laura

    2016-09-10

    Dendrimers have called the attention of scientists in the area of drug and gene delivery over the last two decades for their versatility, complexity and multibranching properties. Some strategies for optimizing drug pharmacokinetics and site-specific targeting using dendrimers have been proposed. Among them, those related to treating and managing ocular diseases are of special interest. Ocular therapies suffer from significant disadvantages, including frequent administration, poor penetration and/or rapid elimination. This review provides an overview of the recent and promising progress in the dendrimers field, focusing on both the anterior and posterior segments of the eye ocular targets, the use of dendrimers as a strategy for overcoming obstacles to the traditional treatment of ocular diseases and an outlook on future directions. Finally, a first approach to ocular safety with dendrimers is intended that accounts for the state-of-the-art science to date.

  13. A fluorinated dendrimer achieves excellent gene transfection efficacy at extremely low nitrogen to phosphorus ratios

    Science.gov (United States)

    Wang, Mingming; Liu, Hongmei; Li, Lei; Cheng, Yiyun

    2014-01-01

    Polymers have shown great promise in the design of high efficient and low cytotoxic gene vectors. Here we synthesize fluorinated dendrimers for use as gene vectors. Fluorinated dendrimers achieve excellent gene transfection efficacy in several cell lines (higher than 90% in HEK293 and HeLa cells) at extremely low N/P ratios. These polymers show superior efficacy and biocompatibility compared with several commercial transfection reagents such as Lipofectamine 2000 and SuperFect. Fluorination enhances the cellular uptake of the dendrimer/DNA polyplexes and facilitates their endosomal escape. In addition, the fluorinated dendrimer shows excellent serum resistance and exhibits high gene transfection efficacy even in medium containing 50% FBS. The results suggest that fluorinated dendrimers are a new class of highly efficient gene vectors and fluorination is a promising strategy to design gene vectors without involving sophisticated syntheses.

  14. Quasi-elastic light scattering of platinum dendrimer-encapsulated nanoparticles.

    Science.gov (United States)

    Wales, Christina H; Berger, Jacob; Blass, Samuel; Crooks, Richard M; Asherie, Neer

    2011-04-05

    Platinum dendrimer-encapsulated nanoparticles (DENs) containing an average 147 atoms were prepared within sixth-generation, hydroxyl-terminated poly(amidoamine) dendrimers (G6-OH). The hydrodynamic radii (R(h)) of the dendrimer/nanoparticle composites (DNCs) were determined by quasi-elastic light scattering (QLS) at high (pH ∼10) and neutral pH for various salt concentrations and identities. At high pH, the size of the DNC (R(h) ∼4 nm) is close to that of the empty dendrimer. At neutral pH, the size of the DNC approximately doubles (R(h) ∼8 nm) whereas that of the empty dendrimer remains unchanged. Changes in ionic strength also alter the size of the DNCs. The increase in size of the DNC is likely due to electrostatic interactions involving the metal nanoparticle.

  15. Synthesis of poly(amidoamine-dendrimer-silver nanoparticles composite for application as bactericides

    Directory of Open Access Journals (Sweden)

    Shahla Namazkar

    2014-04-01

    Full Text Available As awareness of sanitation, disease transmission factors and personal protection increases, researchers have focused on developing materials with antibacterial properties. Silver-PAMAM-dendrimer has unique antibacterial properties that make it an ideal candidate for medical applications. In this study, poly (amidoamine (PAMAM dendrimers from Generations 0.5- 4.0 were synthesized using divergent methods. Silver was combined with PAMAM dendrimers from the Generation 2.0, 3.0 and 4.0 to form colloidal solutions. The antimicrobial capabilities of Silver-PAMAM-dendrimer (Generation 2.0 were tested against four types of gram positive and negative bacteria. Its bactericidal activities were revealed for all four types of bacteria that could not grow in samples containing 600 ppm of Silver-PAMAM-dendrimer (Generation 2.0.

  16. Poly(Propylene Imine Dendrimers and Amoxicillin as Dual-Action Antibacterial Agents

    Directory of Open Access Journals (Sweden)

    Natalia Wrońska

    2015-10-01

    Full Text Available Besides acting as antimicrobial compounds, dendrimers can be considered as agents that improve the therapeutic effectiveness of existing antibiotics. In this work we present a new approach to using amoxicillin (AMX against reference strains of common Gram-negative pathogens, alone and in combination with poly(propylene imine (PPI dendrimers, or derivatives thereof, in which 100% of the available hydrogen atoms are substituted with maltose (PPI 100%malG3. The concentrations of dendrimers used remained in the range non-toxic to eukaryotic cells. The results indicate that PPI dendrimers significantly enhance the antibacterial effect of amoxicillin alone, allowing antibiotic doses to be reduced. It is important to reduce doses of amoxicillin because its widespread use in medicine could lead to the development of bacterial resistance and environmental pollution. This is the first report on the combined antibacterial activity of PPI surface-modified maltose dendrimers and amoxicillin.

  17. Electron-transfer processes in dendrimers and their implication in biology, catalysis, sensing and nanotechnology

    Science.gov (United States)

    Astruc, Didier

    2012-04-01

    The extraordinary development of the design and synthesis of dendrimers has allowed scientists to locate redox sites at precise positions (core, focal points, branching points, termini, cavities) of these perfectly defined macromolecules, which have generation-controlled sizes and topologies matching those of biomolecules. Redox-dendrimer engineering has led to fine modelling studies of electron-transfer metalloproteins, in which the branches of the dendrimers hinder access to the active site in a manner reminiscent of that of the protein. It has also enabled the construction of remarkable catalysts, sensors and printboards, including by sophisticated design of the interface between redox dendrimers and solid-state devices -- for example by functionalizing electrodes and other surfaces. Electron-transfer processes between dendrimers and a variety of other molecules hold promising applications in diverse areas that range from bio-engineering to sensing, catalysis and energy materials.

  18. Polymerization of a divalent/tetravalent metal-storing atom-mimicking dendrimer.

    Science.gov (United States)

    Albrecht, Ken; Hirabayashi, Yuki; Otake, Masaya; Mendori, Shin; Tobari, Yuta; Azuma, Yasuo; Majima, Yutaka; Yamamoto, Kimihisa

    2016-12-01

    The phenylazomethine dendrimer (DPA) has a layer-by-layer electron density gradient that is an analog of the Bohr atom (atom mimicry). In combination with electron pair mimicry, the polymerization of this atom-mimicking dendrimer was achieved. The valency of the mimicked atom was controlled by changing the chemical structure of the dendrimer. By mimicking a divalent atom, a one-dimensional (1D) polymer was obtained, and by using a planar tetravalent atom mimic, a 2D polymer was obtained. These poly(dendrimer) polymers could store Lewis acids (SnCl2) in their unoccupied orbitals, thus indicating that these poly(dendrimer) polymers consist of a series of nanocontainers.

  19. Magnetic properties of colloidal cobalt nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Torchio, R; Meneghini, C; Mobilio, S; Capellini, G [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Prieto, A Garcia; Alonso, J; Fdez-Gubieda, M L [Departamento de Electricidad y Electronica y Fisica Aplicada I, Universidad del PaIs Vasco (Spain); Liveri, V Turco; Ruggirello, A M [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Longo, A [ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo (Italy); Neisius, T, E-mail: torchio@fis.uniroma3.i [Universite Paul CEZANNE, Faculte des Sciences et Techniques, Marseille (France)

    2010-01-01

    Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co{sub 3}O{sub 4}with metallic Co and some Co{sup 2+} bound to the surfactant. The presence of antiferromagnetic Co{sub 3}O{sub 4} explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

  20. Quantum confinement in GaP nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Laurich, B.K.; Smith, D.C.; Healy, M.D.

    1994-06-01

    We have prepared GaP and GaAs nanoclusters from organometallic condensation reactions of E[Si(ChH{sub 3})3]3 (E = P, As) and GaCl{sub 3}. The size of the as synthesized clusters is 10 {Angstrom} to 15 {Angstrom}. Larger clusters of 20 {Angstrom} to 30 {Angstrom} size were obtained by thermal annealing of the as grown material. X-ray diffraction and transmission electron microscopy confirm the high crystalline quality. A lattice contraction of 6.7% could be seen for 10 {Angstrom} sized GaAs clusters. The clusters are nearly spherical in shape. Optical absorption spectra show a distinct line which can be assigned to the fundamental transition of the quantum confined electronic state. The measured blue shift, with respect to the GaP bulk absorption edge is 0.53 eV. As the cluster is smaller than the exciton radius, we can calculate the cluster size from this blue shift and obtain 20.2 {Angstrom}, consistent with the results from X-ray diffraction of 19.5 {Angstrom} for the same sample.

  1. Fractal Electronic Circuits Assembled From Nanoclusters

    Science.gov (United States)

    Fairbanks, M. S.; McCarthy, D.; Taylor, R. P.; Brown, S. A.

    2009-07-01

    Many patterns in nature can be described using fractal geometry. The effect of this fractal character is an array of properties that can include high internal connectivity, high dispersivity, and enhanced surface area to volume ratios. These properties are often desirable in applications and, consequently, fractal geometry is increasingly employed in technologies ranging from antenna to storm barriers. In this paper, we explore the application of fractal geometry to electrical circuits, inspired by the pervasive fractal structure of neurons in the brain. We show that, under appropriate growth conditions, nanoclusters of Sb form into islands on atomically flat substrates via a process close to diffusion-limited aggregation (DLA), establishing fractal islands that will form the basis of our fractal circuits. We perform fractal analysis of the islands to determine the spatial scaling properties (characterized by the fractal dimension, D) of the proposed circuits and demonstrate how varying growth conditions can affect D. We discuss fabrication approaches for establishing electrical contact to the fractal islands. Finally, we present fractal circuit simulations, which show that the fractal character of the circuit translates into novel, non-linear conduction properties determined by the circuit's D value.

  2. Catalytic photooxidation of pentachlorophenol using semiconductor nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    WILCOXON,JESS P.

    2000-04-17

    Pentachlorophenol (PCP) is a toxic chlorinated aromatic molecule widely used as fungicide, a bactericide and a wood preservation, and thus ubiquitous in the environment. The authors report photo-oxidation of PCP using a variety of nanosize semiconductor metal oxides and sulfides in both aqueous and polar organic solvents and compare the photo-oxidation kinetics of these nanoclusters to widely studied bulk powders like Degussa P-25 TiO{sub 2} and CdS. They study both the light intensity dependence of PCP photooxidation for nanosize SnO{sub 2} and the size dependence of PCP photooxidation for both nanosize SnO{sub 2} and MoS{sub 2}. They find an extremely strong size dependence for the latter which they attribute to its size-dependent band gap and the associated change in redox potentials due to quantum confinement of the hole-electron pair. The authors show that nanosize MoS{sub 2} with a diameter of d=3.0 nm and an absorbance edge of {approximately}450 nm is a very effective photooxidation catalyst for complete PCP mineralization, even when using only visible light irradiation.

  3. Correlation effects in Auger spectra of Ni and Cu nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Troyan, V.I.; Borisyuk, P.V.; Kashurnikov, V.A. [National Research Nuclear University (MEPhI), 31 Kashirskoye shosse, 115409, Moscow (Russian Federation); Krasavin, A.V., E-mail: avkrasavin@gmail.com [National Research Nuclear University (MEPhI), 31 Kashirskoye shosse, 115409, Moscow (Russian Federation); Borman, V.D.; Tronin, V.I. [National Research Nuclear University (MEPhI), 31 Kashirskoye shosse, 115409, Moscow (Russian Federation)

    2013-01-17

    Results of experimental research of exciton-like two-hole states in nanoclusters of narrow-band metals (Ni, Cu) on surface of high-oriented pyrolitic graphite by X-ray photoelectron and Auger electron spectroscopy are presented. It was found that the evolution of the electronic structure in Ni nanoclusters with the decreasing of their sizes can lead to appearance of long-living two-hole states in the valence band. One-particle and two-particle density of states are analyzed, and the Auger-electron spectra confirming the presence of the bound and localized states are obtained.

  4. Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.

    Science.gov (United States)

    Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

    2014-07-07

    Nanohybrids consisting of Au nanocluster and polythiophene nanowire assemblies exhibit unique thermal-responsive optical behaviors and charge-transfer controlled magnetic and optoelectronic properties. The ultrasmall Au nanocluster enhanced photoabsorption and conductivity effectively improves the photocurrent of nanohybrid based photovoltaics, leading to an increase of power conversion efficiency by 14 % under AM 1.5 illumination. In addition, nanohybrids exhibit electric field controlled spin resonance and magnetic field sensing behaviors, which open up the potential of charge-transfer complex system where the magnetism and optoelectronics interact.

  5. Evaluation of the activity of new cationic carbosilane dendrimers on trophozoites and cysts of Acanthamoeba polyphaga.

    Science.gov (United States)

    Heredero-Bermejo, Irene; Copa-Patiño, Jose Luis; Soliveri, Juan; Fuentes-Paniagua, Elena; de la Mata, Francisco Javier; Gomez, Rafael; Perez-Serrano, Jorge

    2015-02-01

    Dendrimers are repetitively branched molecules with a broad spectrum of applications, mainly for their antimicrobial properties and as nanocarriers for other molecules. Recently, our research group have synthesized and studied their activity against Acanthamoeba sp., causative agent of a severe ocular disease in humans: Acanthamoeba keratitis. New cationic carbosilane dendrimers were tested against the protozoa forms at different concentrations and for different incubation times. Trophozoite viability was determined by manual counting and cyst viability by observing excystment in microplates with fresh culture medium. Cytotoxicity was checked on HeLa cells using the microculture tetrazolium assay. Alterations were observed by optical microscopy and by flow cytometry staining with propidium iodide. Six out of the 18 dendrimers tested were non-cytotoxic and effective against the trophozoite form, having one of them (dendrimer 14 with an IC50 of 2.4 + 0.1 mg/L) a similar activity to chlorhexidine digluconate (IC50 1.7 + 0.1 mg/L). This dendrimer has a polyphenoxo core and a sulphur atom close to the six -NH3+ terminal groups. On the other hand, only two dendrimers showed some effect against cysts (dendrimers 14 and 17). However, their minimum cysticidal concentrations were cytotoxic and less effective than the control drug. The alterations on the amoeba morphology produced by the treatment with dendrimers were size reduction, increased complexity, loss of acanthopodia and cell membrane disruption. In conclusion, these results suggest that some dendrimers may be studied in animal models to test their effect and that new dendrimers with similar features should be synthesized.

  6. The adsorption-desorption transition of double-stranded DNA interacting with an oppositely charged dendrimer induced by multivalent anions.

    Science.gov (United States)

    Jiang, Yangwei; Zhang, Dong; Zhang, Yaoyang; Deng, Zhenyu; Zhang, Linxi

    2014-05-28

    The adsorption-desorption transition of DNA in DNA-dendrimer solutions is observed when high-valence anions, such as hexavalent anions, are added to the DNA-dendrimer solutions. In the DNA-dendrimer solutions with low-valence anions, dendrimers bind tightly with the V-shaped double-stranded DNA. When high-valence anions, such as pentavalent or hexavalent anions, are added to the DNA-dendrimer solutions, the double-stranded DNA chains can be stretched straightly and the dendrimers are released from the double-stranded DNA chains. In fact, adding high-valence anions to the solutions can change the charge spatial distribution in the DNA-dendrimer solutions, and weaken the electrostatic interactions between the positively charged dendrimers and the oppositely charged DNA chains. Adsorption-desorption transition of DNA is induced by the overcharging of dendrimers. This investigation is capable of helping us understand how to control effectively the release of DNA in gene/drug delivery because an effective gene delivery for dendrimers includes non-covalent DNA-dendrimer binding and the effective release of DNA in gene therapy.

  7. The first peripherally masked thiol dendrimers: a facile and highly efficient functionalization strategy of polyester dendrimers via one-pot xanthate deprotection/thiol-acrylate Michael addition reactions.

    Science.gov (United States)

    Auty, Sam E R; Andrén, Oliver; Malkoch, Michael; Rannard, Steven P

    2014-06-25

    Introducing multiple reactive functional groups at the periphery of dendrimer materials presents considerable challenges if the functionality is able to self-react. An efficient and facile approach to introducing masked thiols at the surface of polyester dendrimers is presented. One-pot, deprotection/thiol-acrylate Michael addition from the xanthate-functional dendritic substrates (generation zero to two) has been achieved for the first time, with high efficiency demonstrated using three acrylates of varying chemistry and avoiding disulfide formation.

  8. Structure-activity relationship of dendrimers engineered with twenty common amino acids in gene delivery.

    Science.gov (United States)

    Wang, Fei; Hu, Ke; Cheng, Yiyun

    2016-01-01

    Systematic explorations on the structure-activity relationship of surface-engineered dendrimers are essential to design high efficient and safe gene vectors. The chemical diversity of residues in naturally occurring amino acids allows us to generate a library of dendrimers with various surface properties. Here, we synthesized a total number of 40 dendrimers engineered with the twenty common amino acids and investigated their performances in gene delivery. The results show that gene transfection efficacy of the synthesized materials depends on both the type of amino acid and the conjugation ratio. Dendrimers engineered with cationic and hydrophobic amino acids possess relatively higher transfection efficacies. Engineering dendrimers with cationic amino acids such as arginine and lysine facilitates polyplex formation and cellular uptake, with histidine improves endosomal escape of the polyplexes, and with hydrophobic amino acids such as tyrosine and phenylalanine modulates the balance between hydrophobicity and hydrophilicity on dendrimer surface, which is beneficial for efficient cellular internalization. Dendrimers engineered with anionic or hydrophilic amino acids show limited transfection efficacy due to poor DNA binding capacity and/or limited cellular uptake. In the aspect of cytotoxicity, dendrimers engineered with arginine, lysine, tyrosine, phenylalanine and tryptophan show much higher cytotoxicity than other engineered dendrimers. These results are helpful for us to tailor the surface chemistry of dendrimers for efficient gene delivery. Cationic polymers such as dendrimers were widely used as gene vectors but are limited by relatively low delivery efficacy and high toxicity. To achieve efficient and low toxic gene delivery, the polymers were modified with various ligands. However, these ligand-modified polymers in gene delivery are reported by independent researchers using different polymer scaffolds and cell lines. It is hard to provide structure

  9. On the formation of copper nanoparticles in nanocluster aggregation source

    NARCIS (Netherlands)

    Dutka, Mikhail V.; Turkin, Anatoliy A.; Vainchtein, David I.; De Hosson, Jeff Th. M.

    2015-01-01

    The influence of pressure and type of inert gas (Ar and Kr) on the morphology and size distribution of nanoparticles produced in a nanocluster source is studied experimentally. The experimental data are used to validate the model of cluster formation from a supersaturated atomic vapor in an inert bu

  10. On the formation of copper nanoparticles in nanocluster aggregation source

    NARCIS (Netherlands)

    Dutka, Mikhail V.; Turkin, Anatoliy A.; Vainchtein, David I.; De Hosson, Jeff Th. M.

    The influence of pressure and type of inert gas (Ar and Kr) on the morphology and size distribution of nanoparticles produced in a nanocluster source is studied experimentally. The experimental data are used to validate the model of cluster formation from a supersaturated atomic vapor in an inert

  11. Surface Segregation in Supported Pd-Pt Nanoclusters and Alloys

    NARCIS (Netherlands)

    van den Oetelaar, L.C.A.; Nooij, O.W.; Oerlemans, S.; Denier van der Gon, A.W.; Brongersma, H.H.; Lefferts, Leonardus; Roosenbrand, A.G.; van Veen, J.A.R.

    1998-01-01

    Surface segregation processes in Pd-Pt alloys and bimetallic Pd-Pt nanoclusters on alumina and carbon supports (technical catalysts) have been investigated by determining the metal surface composition of these systems by low-energy ion scattering (LEIS). Both Pd-rich (Pd80Pt20) and Pt-rich

  12. Enhanced fluorescence of silver nanoclusters stabilized with branched oligonucleotides.

    Science.gov (United States)

    Latorre, Alfonso; Lorca, Romina; Zamora, Félix; Somoza, Álvaro

    2013-05-28

    DNA stabilized silver nanoclusters (AgNCs) are promising optical materials, whose fluorescence properties can be tuned by the selection of the DNA sequence employed. In this work we have used modified oligonucleotides in the preparation of AgNCs. The fluorescent intensity obtained was 60 times higher than that achieved with standard oligonucleotides.

  13. Nanoclustering as a dominant feature of plasma membrane organization

    NARCIS (Netherlands)

    Garcia-Parajo, M.F.; Cambi, A.; Torreno-Pina, J.A.; Thompson, N.; Jacobson, K.

    2014-01-01

    Early studies have revealed that some mammalian plasma membrane proteins exist in small nanoclusters. The advent of super-resolution microscopy has corroborated and extended this picture, and led to the suggestion that many, if not most, membrane proteins are clustered at the plasma membrane at

  14. Ultrafast coherence transfer in DNA-templated silver nanoclusters

    DEFF Research Database (Denmark)

    Thyrhaug, Erling; Bogh, Sidsel Ammitzbøll; Carro, Miguel

    2017-01-01

    DNA-templated silver nanoclusters of a few tens of atoms or less have come into prominence over the last several years due to very strong absorption and efficient emission. Applications in microscopy and sensing have already been realized, however little is known about the excited-state structure...

  15. On the formation of copper nanoparticles in nanocluster aggregation source

    NARCIS (Netherlands)

    Dutka, Mikhail V.; Turkin, Anatoliy A.; Vainchtein, David I.; De Hosson, Jeff Th. M.

    2015-01-01

    The influence of pressure and type of inert gas (Ar and Kr) on the morphology and size distribution of nanoparticles produced in a nanocluster source is studied experimentally. The experimental data are used to validate the model of cluster formation from a supersaturated atomic vapor in an inert bu

  16. PHOTOOXIDATION OF ORGANIC WASTES USING SEMICONDUCTOR NANOCLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Wilcoxon, Jess P.

    2000-12-31

    It would be a major boon to have a visible light absorbing semiconductor catalytic material available, which is also photostable and non-toxic. Such a photocatalyst would make it possible to exploit sunlight as the sole energy source required for detoxification. To this end we have employed our expertise in nanocluster synthesis and processing to make and purify nanoparticles of MoS2. The band-gap and absorbance edges of these nanoparticles can be adjusted by particle size based upon the quantum confinement of the electron-hole pair. In a recent paper we demonstrated the use of these new photocatalysts to destroy phenol, and demonstrated a strong effect of size or band-gap on the rate of photo-oxidation.5 In this research we investigate the photooxidation kinetics and products formed for a standard material, Degussa P-25 TiO2, as compared to nanosize TiO2, SnO2, and MoS2. We examined the light intensity dependence for nanosize SnO2 compared to TiO2 (Degussa), and the effect o f size on photooxidation kinetics for both SnO2 and MoS2. We studied photooxidation in aqueous systems and, for the first time, a system consisting almost entirely of a polar organic, acetonitrile. Our primary objective was to develop an entirely new class of material: nanosize semiconductors with visible bandgaps and to engineer these material's properties to allow us to photooxidize toxic organic compounds in water on a reasonable time scale ({approx}8 hrs). A second objective was to study how certain material properties such as size, surface treatment, and material type affect the efficiency of the photocatalytic process as well as optimizing these features.

  17. Polarization properties of fluorescent BSA protected Au25 nanoclusters

    Science.gov (United States)

    Raut, Sangram; Chib, Rahul; Rich, Ryan; Shumilov, Dmytro; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2013-03-01

    BSA protected gold nanoclusters (Au25) are attracting a great deal of attention due to their unique spectroscopic properties and possible use in biophysical applications. Although there are reports on synthetic strategies, spectroscopy and applications, little is known about their polarization behavior. In this study, we synthesized the BSA protected Au25 nanoclusters and studied their steady state and time resolved fluorescence properties including polarization behavior in different solvents: glycerol, propylene glycol and water. We demonstrated that the nanocluster absorption spectrum can be separated from the extinction spectrum by subtraction of Rayleigh scattering. The nanocluster absorption spectrum is well approximated by three Gaussian components. By a comparison of the emissions from BSA Au25 clusters and rhodamine B in water, we estimated the quantum yield of nanoclusters to be higher than 0.06. The fluorescence lifetime of BSA Au25 clusters is long and heterogeneous with an average value of 1.84 μs. In glycerol at -20 °C the anisotropy is high, reaching a value of 0.35. However, the excitation anisotropy strongly depends on the excitation wavelengths indicating a significant overlap of the different transition moments. The anisotropy decay in water reveals a correlation time below 0.2 μs. In propylene glycol the measured correlation time is longer and the initial anisotropy depends on the excitation wavelength. BSA Au25 clusters, due to long lifetime and high polarization, can potentially be used in studying large macromolecules such as protein complexes with large molecular weight.BSA protected gold nanoclusters (Au25) are attracting a great deal of attention due to their unique spectroscopic properties and possible use in biophysical applications. Although there are reports on synthetic strategies, spectroscopy and applications, little is known about their polarization behavior. In this study, we synthesized the BSA protected Au25 nanoclusters and

  18. Rational design of dendrimer/lipid nanoassemblies in drug delivery for cancer chemotherapy

    Science.gov (United States)

    Sun, Qihang

    Nanocarriers can minimize the side effects and improve therapeutic efficacy of anticancer drugs. Although some success has been achieved via active or passive drug delivery to tumor cells, the known nanocarriers are far from satisfying therapeutic efficacy expectations. This is because they usually fail in one of the four crucial requirements, that is, to retain drug in blood circulation but release it reliably in tumor cells and to be stealthy in transport in circulation and tumor tissue but sticky upon arrival at the tumor cell. Therefore, the goal of this work is to fabricate nanoassemblies of dendrimers and lipids to address all these challenges. Particularly, nanoassemblies designed and prepared in this work are illustrated to improve the tumor tissue penetration. Examples of dendrimers synthesized in this work are water-insoluble, pH-dependent water-insoluble and water-soluble biodegradable polyester dendrimers. These dendrimers are shown to be encapsulated by commonly used fusogenic and long-circulating lipids to form reliable nanoassemblies. The dendrimer/lipid nanocarriers are used to demonstrate a cascade drug delivery. They are expected to be stable in circulation, due to their appropriately large size, but to release the drug-loaded dendrimers in tumor tissue. The released dendrimers carrying drugs are much smaller and hence expected to have a much deeper penetration throughout the tumor tissue.

  19. Synthesis, Radiolabeling, and In Vivo Imaging of PEGylated High-Generation Polyester Dendrimers.

    Science.gov (United States)

    McNelles, Stuart A; Knight, Spencer D; Janzen, Nancy; Valliant, John F; Adronov, Alex

    2015-09-14

    A fifth generation aliphatic polyester dendrimer was functionalized with vinyl groups at the periphery and a dipicolylamine Tc(I) chelate at the core. This structure was PEGylated with three different molecular weight mPEGs (mPEG160, mPEG350, and mPEG750) using thiol-ene click chemistry. The size of the resulting macromolecules was evaluated using dynamic light scattering, and it was found that the dendrimer functionalized with mPEG750 was molecularly dispersed in water, exhibiting a hydrodynamic diameter of 9.2 ± 2.1 nm. This PEGylated dendrimer was subsequently radiolabeled using [(99m)Tc(CO)3(H2O)3](+) and purified to high (>99%) radiochemical purity. Imaging studies were initially performed on healthy rats to allow comparison to previous Tc-labeled dendrimers and then on xenograft murine tumor models, which collectively showed that the dendrimers circulated in the blood for an extended period of time (up to 24 h). Furthermore, the radiolabeled dendrimer accumulated in H520 xenograft tumors, which could be visualized by single-photon emission computed tomography (SPECT). The reported PEGylated aliphatic polyester dendrimers represent a new platform for developing tumor-targeted molecular imaging probes and therapeutics.

  20. Encapsulation of 2-methoxyestradiol within multifunctional poly(amidoamine) dendrimers for targeted cancer therapy.

    Science.gov (United States)

    Wang, Yin; Guo, Rui; Cao, Xueyan; Shen, Mingwu; Shi, Xiangyang

    2011-04-01

    We report here a general approach to using multifunctional poly(amidoamine) (PAMAM) dendrimer-based platform to encapsulate a potential anticancer drug for targeted cancer therapy. In this approach, amine-terminated generation 5 (G5) PAMAM dendrimers were sequentially modified with fluorescein isothiocyanate (FI) and folic acid (FA) via covalent conjugation, followed by an acetylation reaction to neutralize the remaining amines of the dendrimer surfaces. The synthesized multifunctional dendrimers (G5.NHAc-FI-FA) were then used to complex a potential anticancer drug, 2-methoxyestradiol (2-ME) for targeted delivery of the drugs to cancer cells overexpressing high-affinity folic acid receptors (FAR). We show that the formed G5.NHAc-FI-FA/2-ME complexes with each dendrimer encapsulating approximately 3.7 2-ME molecules are water soluble and stable. In vitro release studies show that 2-ME complexed with the multifunctional dendrimers can be released in a sustained manner. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in conjunction with cell morphology observation demonstrates that the G5.NHAc-FI-FA/2-ME complexes can specifically target and display specific therapeutic efficacy to cancer cells overexpressing high-affinity FAR. Findings from this study suggest that multifunctional dendrimers may be used as a general drug carrier to encapsulate various cancer drugs for targeted therapy of different types of cancer.

  1. Interaction of a patterned amphiphilic polyphenylene dendrimer with a lipid monolayer: electrostatic interactions dominate.

    Science.gov (United States)

    Okuno, Masanari; Mezger, Markus; Stangenberg, René; Baumgarten, Martin; Müllen, Klaus; Bonn, Mischa; Backus, Ellen H G

    2015-02-17

    Dendrimeric macromolecules with defined shape and size are promising candidates for delivering drug or DNA molecules into cells. In this work we study the influence of an amphiphilic polyphenylene dendrimer on a model cell membrane consisting of a condensed 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid monolayer. A small surface pressure decrease is observed when the dendrimer solution is injected into the aqueous phase below the monolayer. X-ray reflectivity measurements show that the surface monolayer remains intact. The molecular-scale picture is obtained with sum-frequency generation spectroscopy. With this technique, we observe that the tails of the surfactant molecules become less ordered upon interaction with the amphiphilic polyphenylene dendrimer. In contrast, the water molecules below the DPPC layer become more ordered. Our observations suggest that electrostatic interactions between the negative charge of the dendrimer and the positively charged part of the DPPC headgroup keep the dendrimer located below the headgroup. No evidence of dendrimer insertion into the membrane has been observed. Apparently before entering the cell membrane the dendrimer can stick at the hydrophilic part of the lipids.

  2. Development of TREN dendrimers over mesoporous SBA-15 for CO 2 adsorption

    Science.gov (United States)

    Bhagiyalakshmi, Margandan; Park, Sang Do; Cha, Wang Seog; Jang, Hyun Tae

    2010-09-01

    Mesoporous SBA-15 was synthesized using rice husk ash (RHA) as the silica source and their defective Si-OH groups were grafted with tris(2-aminoethyl) amine (TREN) dendrimers generation through step-wise growth technique. The X-ray diffraction (XRD) and nitrogen adsorption/desorption results of parent SBA-15 obtained from RHA, suggests its resemblance with SBA-15 synthesized using conventional silica sources. Furthermore, the nitrogen adsorption/desorption results of SBA-15/TREN dendrimer generations (G1-G3) illustrates the growth of dendrimer inside the mesopores of SBA-15 and their CO 2 adsorption capacity was determined at 25 °C. The maximum CO 2 adsorption capacity of 5-6 and 7-8 wt% over second and third dendrimer generation was observed which is discernibly higher than the reported melamine and PAMAM dendrimers. The experimental CO 2 adsorption capacity was found to be less than theoretically calculated CO 2 adsorption capacity due to inter and intra molecular amidation as result of steric hindrance during the dendrimer growth. These SBA-15/TREN dendrimer generations also exhibit thermal stability up to 350 °C and CO 2 adsorption capacity remains unaltered upon seven consecutive runs.

  3. Uptake, efflux, and mass transfer coefficient of fluorescent PAMAM dendrimers into pancreatic cancer cells.

    Science.gov (United States)

    Opitz, Armin W; Czymmek, Kirk J; Wickstrom, Eric; Wagner, Norman J

    2013-02-01

    Targeted delivery of imaging agents to cells can be optimized with the understanding of uptake and efflux rates. Cellular uptake of macromolecules is studied frequently with fluorescent probes. We hypothesized that the internalization and efflux of fluorescently labeled macromolecules into and out of mammalian cells could be quantified by confocal microscopy to determine the rate of uptake and efflux, from which the mass transfer coefficient is calculated. The cellular influx and efflux of a third generation poly(amido amine) (PAMAM) dendrimer labeled with an Alexa Fluor 555 dye was measured in Capan-1 pancreatic cancer cells using confocal fluorescence microscopy. The Capan-1 cells were also labeled with 5-chloromethylfluorescein diacetate (CMFDA) green cell tracker dye to delineate cellular boundaries. A dilution curve of the fluorescently labeled PAMAM dendrimer enabled quantification of the concentration of dendrimer in the cell. A simple mass transfer model described the uptake and efflux behavior of the PAMAM dendrimer. The effective mass transfer coefficient was found to be 0.054±0.043μm/min, which corresponds to a rate constant of 0.035±0.023min(-1) for uptake of the PAMAM dendrimer into the Capan-1 cells. The effective mass transfer coefficient was shown to predict the efflux behavior of the PAMAM dendrimer from the cell if the fraction of labeled dendrimer undergoing non-specific binding is accounted for. This work introduces a novel method to quantify the mass transfer behavior of fluorescently labeled macromolecules into mammalian cells.

  4. Carboxymethyl chitosan-poly(amidoamine) dendrimer core-shell nanoparticles for intracellular lysozyme delivery.

    Science.gov (United States)

    Zhang, Xiaoyang; Zhao, Jun; Wen, Yan; Zhu, Chuanshun; Yang, Jun; Yao, Fanglian

    2013-11-06

    Intracellular delivery of native, active proteins is challenging due to the fragility of most proteins. Herein, a novel polymer/protein polyion complex (PIC) nanoparticle with core-shell structure was prepared. Carboxymethyl chitosan-grafted-terminal carboxyl group-poly(amidoamine) (CM-chitosan-PAMAM) dendrimers were synthesized by amidation and saponification reactions. (1)H NMR was used to characterize CM-chitosan-PAMAM dendrimers. The TEM images and results of lysozyme loading efficiency indicated that CM-chitosan-PAMAM dendrimers could self-assemble into core-shell nanoparticles, and lysozyme was efficiently encapsulated inside the core of CM-chitosan-PAMAM dendrimer nanoparticles. Activity of lysozyme was completely inhibited by CM-chitosan-PAMAM Dendrimers at physiological pH, whereas it was released into the medium and exhibited a significant enzymatic activity in an acidic intracellular environment. Moreover, the CM-chitosan-PAMAM dendrimer nanoparticles did not exhibit significant cytotoxicity in the range of concentrations below 3.16 mg/ml. The results indicated that these CM-chitosan-PAMAM dendrimers have excellent properties as highly potent and non-toxic intracellular protein carriers, which would create opportunities for novel applications in protein delivery.

  5. Development of a Topical Resveratrol Formulation for Commercial Applications Using Dendrimer Nanotechnology.

    Science.gov (United States)

    Pentek, Tyler; Newenhouse, Eric; O'Brien, Brennin; Chauhan, Abhay Singh

    2017-01-14

    Resveratrol (RSV) is well known for its anti-oxidant and anti-aging properties. However, resveratrol is insoluble in water and has stability issues. Recently, efforts were placed to prepare a resveratrol-based advanced anti-aging topical product but it contains harsh organic solvents and oils that could be harmful to the human body and the environment. Hence, we propose the use of a multifunctional dendrimer to solve the solubility and stability issues of resveratrol. A dendrimer-resveratrol complex was prepared, optimized and tested for solubility enhancement, stability in solution and cream dosage forms. We have also developed a high performance liquid chromatography method to measure the resveratrol within the final product. PAMAM dendrimers increased the solubility and stability of resveratrol in water and semisolid dosage forms. Therefore, this product would be water based 'green' formulation devoid of harsh organic solvents and oils and can be safely applied to the skin. Additionally, we have shown that the dendrimer helped to increase overall RSV loading and skin penetration of resveratrol. The dendrimer-RSV formulation was successfully scaled up towards commercialization. Dendrimer with RSV has led to an innovation in anti-aging cream and solutions that could be commercially marketed. Dendrimer-RSV complex could also be added to other product forms for additional purposes and applications.

  6. Nanoparticulate platinum films on gold using dendrimer-based wet chemical method

    Indian Academy of Sciences (India)

    S Raghu; Sheela Berchmans; K L N Phani; V Yegnaraman

    2005-11-01

    There is a growing interest in devising wet chemical alternatives for physical deposition methods for applications involving thin films, e.g., catalysis. Deposition of platinum on thin gold films is often a problem leading to incomplete coverage and improper adhesion to solid surfaces. Gold substrates often need pre-activation for achieving complete coverage. We demonstrate here that dendrimers with proper functionalities and size work as well-defined nucleating agents and adhesion promoters. This feature is demonstrated using an amine-terminated dendrimer of generation 4.0. This approach allows one to obtain adherent nanoparticulate films of platinum on gold. Unlike other nucleating agents and adhesion promoting compounds, dendrimers have a well-defined ordered structure in terms of their space filling ability. The stability of the films obtained with adsorbed dendrimers is emonstrated using the electrocatalytic reactions of fuels like methanol. The films formed without dendrimers cannot sustain the electro-oxidation currents due to the instability of the films while the films formed with dendrimers can sustain currents for longer duration and for several cycles. The dendrimer-derived Pt films exhibit higher catalytic activity compared to other methods.

  7. Phosphorus Dendrimers as Carriers of siRNA—Characterisation of Dendriplexes

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Majoral

    2013-04-01

    Full Text Available There are many types of dendrimers used as nanomolecules for gene delivery but there is still an ongoing search for ones that are able to effectively deliver drugs to cells. The possibility of gene silencing using siRNA gives hope for effective treatment of numerous diseases. The aim of this work was to investigate in vitro biophysical properties of dendriplexes formed by siRNA and cationic phosphorus dendrimers of 3rd and 4th generation. First, using the ethidium bromide intercalation method, it was examined whether dendrimers have an ability to form complexes with siRNA. Next, the characterisation of dendriplexes formed at different molar ratios was carried out using biophysical methods. The effects of zeta potential, size and changes of siRNA conformation on the complexation with dendrimers were examined. It was found that both phosphorus dendrimers interacted with siRNA. The zeta potential values of dendriplexes ranged from negative to positive and the hydrodynamic diameter depended on the number of dendrimer molecules in the complex. Furthermore, using circular dichroism spectroscopy it was found that cationic phosphorus dendrimers changed only slightly the shape of siRNA CD spectra, thus they did not induce significant changes in the nucleic acid secondary structure during complex formation.

  8. "Lego" chemistry for the straightforward synthesis of dendrimers.

    Science.gov (United States)

    Maraval, Valérie; Pyzowski, Jaroslaw; Caminade, Anne-Marie; Majoral, Jean-Pierre

    2003-07-25

    A new straightforward method of synthesis of dendrimers, using two branched monomers (CA(2) and DB(2)), is described. Each generation is obtained in a single quantitative step, with only N(2) or H(2)O as byproducts; generation 4 is obtained in only four steps. The end groups are alternatively phosphines and hydrazines; their versatile reactivity is illustrated by the reaction of generation 4 with a branched CD(5) monomer, which increases the number of end groups in a single step from 48 to 250.

  9. Photosensitizer and peptide-conjugated PAMAM dendrimer for targeted in vivo photodynamic therapy

    Directory of Open Access Journals (Sweden)

    Narsireddy A

    2015-11-01

    Full Text Available Amreddy Narsireddy,1 Kurra Vijayashree,2 Mahesh G Adimoolam,1 Sunkara V Manorama,1 Nalam M Rao21CSIR – Indian Institute of Chemical Technology, 2CSIR – Centre for Cellular and Molecular Biology, Hyderabad, IndiaAbstract: Challenges in photodynamic therapy (PDT include development of efficient near infrared-sensitive photosensitizers (5,10,15,20-tetrakis(4-hydroxyphenyl-21H,23H-porphine [PS] and targeted delivery of PS to the tumor tissue. In this study, a dual functional dendrimer was synthesized for targeted PDT. For targeting, a poly(amidoamine dendrimer (G4 was conjugated with a PS and a nitrilotriacetic acid (NTA group. A peptide specific to human epidermal growth factor 2 was expressed in Escherichia coli with a His-tag and was specifically bound to the NTA group on the dendrimer. Reaction conditions were optimized to result in dendrimers with PS and the NTA at a fractional occupancy of 50% and 15%, respectively. The dendrimers were characterized by nuclear magnetic resonance, matrix-assisted laser desorption/ionization, absorbance, and fluorescence spectroscopy. Using PS fluorescence, cell uptake of these particles was confirmed by confocal microscopy and fluorescence-activated cell sorting. PS-dendrimers are more efficient than free PS in PDT-mediated cell death assays in HER2 positive cells, SK-OV-3. Similar effects were absent in HER2 negative cell line, MCF-7. Compared to free PS, the PS-dendrimers have shown significant tumor suppression in a xenograft animal tumor model. Conjugation of a PS with dendrimers and with a targeting agent has enhanced photodynamic therapeutic effects of the PS.Keywords: photodynamic therapy, dendrimers, nanoparticle, targeted delivery, Affibody, xenograft animal model

  10. Synthesis and Characterization of Poly(Amidoamine Dendrimers Encapsulatd 198Au Nanoparticles

    Directory of Open Access Journals (Sweden)

    R. Ritawidya1,2

    2012-12-01

    Full Text Available Brachytherapy or internal radiotherapy is one of many methods used for treatment of cancer. This modality requires an agent with radionuclides that emits  or β particle with a proper energy. 198Au (99% β max = 0.96 MeV and t1/2 = 2.69 days is one of radionuclides that has been considered to be effective for the above-mentioned purpose. The purpose of this research was to synthesis and characterize poly(amidoamine (PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles as a new brachytherapy agent. PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles was successfully synthesized by a bottom-up method using sodium borohydride as a reductor. Purification was then performed by a size exclusion chromatography in order to separate large Au nanoparticles that were formed outside the cavity of PAMAM G3.0 dendrimers. Prior to the synthesis of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles, the synthetic procedure was first established by using a non-radioactive Au. The PAMAM G3.0 dendrimers encapsulated Au nanoparticles produced was then characterized by using an UV-Vis spectroscopy, a transmission electron microscopy (TEM, particle size analyzer (PSA, and an atomic absorption spectroscopy (AAS. Characterization results revealed that PAMAM G3.0 dendrimers encapsulated Au nanoparticles that were prepared from a reaction mixture of PAMAM G3.0 dendrimers and Au HAuCl4 with mol ratio of 2.8, was found to be a proper formula. It produced PAMAM G3.0 dendrimers encapsulated Au nanoparticles with diameter of 1.743 nm, spheris, uniform and drug loading value of 26.34%. This formula was then used in synthesis using radioactive Au, 198Au. Characterization results of PAMAM G3.0 dendrimers encapsulated 198Au nanoparticles gave a radiochemical purity of 99.4% and zero charge.

  11. Ion-tuned DNA/Ag fluorescent nanoclusters as versatile logic device.

    Science.gov (United States)

    Li, Tao; Zhang, Libing; Ai, Jun; Dong, Shaojun; Wang, Erkang

    2011-08-23

    A novel kind of versatile logic device has been constructed utilizing ion-tuned DNA/Ag fluorescent nanoclusters, with K(+) and H(+) as two inputs. A well-chosen hairpin DNA with a poly-C loop serves as the template for synthesizing two species of Ag nanoclusters. Several G-tracts and C-tracts on its two terminals enable the hairpin DNA to convert into the G-quadruplex and/or i-motif structures upon input of K(+) and H(+). Such a structural change remarkably influences the spectral behaviors of Ag nanoclusters. In particular, different species of Ag nanoclusters have distinct fluorescence responses to the input of K(+) and H(+). These unique features of DNA/Ag nanoclusters enable multiple logic operations via multichannel fluorescence output, indicating the versatility as a molecular logic device. By altering the specific sequence of the hairpin DNA, more logic gates can be constructed utilizing Ag nanoclusters. © 2011 American Chemical Society

  12. Enhancement of muramyldipeptide (MDP) immunostimulatory activity by controlled multimerization on dendrimers.

    Science.gov (United States)

    Sorensen, Nanna S; Boas, Ulrik; Heegaard, Peter M H

    2011-11-10

    Peptidoglycan is a widespread bacterial PAMP molecule and a powerful initiator of innate immune responses. It consists of repeating units of MDP, which as a monomer is only weakly immunostimulatory. Here, MDP-coupled dendrimers were prepared and investigated for stimulation of pig blood mononuclear cells. Compared to monomeric MDP, MDP-dendrimers induced a markedly enhanced production of IL-12 p40, IL-1β and IL-6 and completely down-regulated surface expression of B7 and MHC class II. These results suggest a possible novel strategy based on controlled multimerization of minimal PAMP motifs on dendrimers for preparing molecularly defined immunostimulators with predictable bioactivities.

  13. Dendrimer-Mediated Adhesion between Vapor-Deposited Au and Glass or Si Wafers.

    Science.gov (United States)

    Baker, L A; Zamborini, F P; Sun, L; Crooks, R M

    1999-10-01

    Here, we report the use of amine-terminated poly(amidoamine) (PAMAM) dendrimers as adhesion promoters between vapor-deposited Au films and Si-based substrates. This method is relatively simple, requiring only substrate cleaning, dipping, and rinsing. Proof of concept is illustrated by coating glass slides and single-crystal Si wafers with monolayers of PAMAM dendrimers and then evaporating adherent, 150-nm-thick Au films atop the dendritic adhesion promoter. Scanning tunneling microscopy and cyclic voltammetry have been used to assess the surface roughness and electrochemical stability of the Au films. The effectiveness of the dendrimer adhesion layer is demonstrated using standard adhesive-tape peel tests.

  14. Electron Transfer in Methylene-Blue-Labeled G3 Dendrimers Tethered to Gold

    DEFF Research Database (Denmark)

    Álvarez-Martos, Isabel; Kartashov, Andrey; Ferapontova, Elena

    2016-01-01

    Redox-modified branched 3D dendrimeric nanostructures are considered a proper tool for the wiring of redox enzymes be-cause they provide both an enzyme-friendly environment and exquisite electron transfer (ET) mediation. ET rates in G3 poly-(amido)amine (PAMAM) dendrimers, covalently attached......,the ET mechanism switched from surface-confined ET (electron tunneling) in dilute monolayers to diffusional ET (electron hopping) at higher surface populations of dendrimers. Structural changes in the positively charged dendrimers electrostatically compressed at negative charges of the electrode surface...

  15. Study of the complexation of oxacillin in 1-(4-Carbomethoxypyrrolidone)-terminated PAMAM dendrimers

    DEFF Research Database (Denmark)

    Hansen, Jon Stefan; Ficker, Mario; Petersen, Johannes Fabritius

    2013-01-01

    The complexation of oxacillin to three generations of 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimers was studied with NMR in CD3OD and CDCl3. The stochiometries, which were determined from Job plots, were found to be both solvent- and generation-dependent. The dissociation constants (Kd......) and Gibbs energies for complexation of oxacillin into the 1-(4-carbomethoxypyrrolidone)-terminated PAMAM dendrimer hosts were determined by (1)H NMR titrations and showed weaker binding of oxacillin upon increasing the size (generation) of the dendrimer....

  16. Poly(amido)amine (PAMAM) dendrimer-cisplatin complexes for chemotherapy of cisplatin-resistant ovarian cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Yellepeddi, Venkata Kashyap; Vangara, Kiran Kumar; Palakurthi, Srinath, E-mail: palakurthi@tamhsc.edu [Texas A and M Health Science Center, Irma Lerma Rangel College of Pharmacy (United States)

    2013-09-15

    Dendrimer-cisplatin complexes were prepared using PAMAM dendrimers with terminal -NH{sub 2} and -COOH groups as well as biotin-conjugated dendrimers. Preformulation parameters of dendrimer-cisplatin complexes were studied using differential scanning calorimetry (DSC) and inductively coupled plasma-mass spectrometry (ICP-MS). Cytotoxicity and mechanism of cytotoxicity of dendrimer-cisplatin complexes was investigated in OVCAR-3, SKOV, A2780 and cisplatin-resistant CP70 human ovarian cancer cell lines. The loading of cisplatin in dendrimers was {approx}11 % (w/w). PAMAM G4 dendrimers with amine surface groups (biotinylated and native) have shown 2.5- to 3.0-fold reduction in IC{sub 50} values in ovarian cancer cells when compared with carboxylate surface dendrimers (p < 0.05). A correlation was observed among cytotoxicity of the complexes, cellular uptake, and platinum-DNA adduct formation. Treatment with dendrimer-cisplatin complexes resulted in a 7.0-fold increase (p < 0.05) in expression of apoptotic genes (Bcl2, Bax, p53) and 13.2- to 27.1-fold increase (p < 0.05) in the activity of caspases 3, 8, and 9 in vitro. Results suggest that PAMAM dendrimers can be used as potential carrier for cisplatin chemotherapy of ovarian cancer.

  17. Interactions of dendrimers with biological drug targets: reality or mystery - a gap in drug delivery and development research.

    Science.gov (United States)

    Ahmed, Shaimaa; Vepuri, Suresh B; Kalhapure, Rahul S; Govender, Thirumala

    2016-07-21

    Dendrimers have emerged as novel and efficient materials that can be used as therapeutic agents/drugs or as drug delivery carriers to enhance therapeutic outcomes. Molecular dendrimer interactions are central to their applications and realising their potential. The molecular interactions of dendrimers with drugs or other materials in drug delivery systems or drug conjugates have been extensively reported in the literature. However, despite the growing application of dendrimers as biologically active materials, research focusing on the mechanistic analysis of dendrimer interactions with therapeutic biological targets is currently lacking in the literature. This comprehensive review on dendrimers over the last 15 years therefore attempts to identify the reasons behind the apparent lack of dendrimer-receptor research and proposes approaches to address this issue. The structure, hierarchy and applications of dendrimers are briefly highlighted, followed by a review of their various applications, specifically as biologically active materials, with a focus on their interactions at the target site. It concludes with a technical guide to assist researchers on how to employ various molecular modelling and computational approaches for research on dendrimer interactions with biological targets at a molecular level. This review highlights the impact of a mechanistic analysis of dendrimer interactions on a molecular level, serves to guide and optimise their discovery as medicinal agents, and hopes to stimulate multidisciplinary research between scientific, experimental and molecular modelling research teams.

  18. Hydrophilic magnetic nanoclusters with thermo-responsive properties and their drug controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Meerod, Siraprapa [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Rutnakornpituk, Boonjira; Wichai, Uthai [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Center of Excellence in Biomaterials, Faculty of Science, Naresuan University, Phitsanulok 65000 Thailand (Thailand); Rutnakornpituk, Metha, E-mail: methar@nu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Naresuan University, Phitsanulok 65000 (Thailand); Center of Excellence in Biomaterials, Faculty of Science, Naresuan University, Phitsanulok 65000 Thailand (Thailand)

    2015-10-15

    Synthesis and drug controlled release properties of thermo-responsive magnetic nanoclusters grafted with poly(N-isopropylacrylamide) (poly(NIPAAm)) and poly(NIPAAm-co-poly(ethylene glycol) methyl ether methacrylate) (PEGMA) copolymers were described. These magnetic nanoclusters were synthesized via an in situ radical polymerization in the presence of acrylamide-grafted magnetic nanoparticles (MNPs). Poly(NIPAAm) provided thermo-responsive properties, while PEGMA played a role in good water dispersibility to the nanoclusters. The ratios of PEGMA to NIPAAm in the (co)polymerization in the presence of the MNPs were fine-tuned such that the nanoclusters with good water dispersibility, good magnetic sensitivity and thermo responsiveness were obtained. The size of the nanoclusters was in the range of 50–100 nm in diameter with about 100–200 particles/cluster. The nanoclusters were well dispersible in water at room temperature and can be suddenly agglomerated when temperature was increased beyond the lower critical solution temperature (LCST) (32 °C). The release behavior of an indomethacin model drug from the nanoclusters was also investigated. These novel magnetic nanoclusters with good dispersibility in water and reversible thermo-responsive properties might be good candidates for the targeting drug controlled release applications. - Highlights: • Nanoclusters with good water dispersibility and magnetic response were prepared. • They were grafted with thermo-responsive poly(NIPAAm) and/or poly(PEGMA). • Poly(NIPAAm) provided thermo-responsive properties to the nanoclusters. • Poly(PEGMA) provided good water dispersibilityto the nanoclusters. • Accelerated and controllable releases of a drug from the nanoclusters were shown.

  19. Signal integration by lipid-mediated spatial cross talk between Ras nanoclusters.

    Science.gov (United States)

    Zhou, Yong; Liang, Hong; Rodkey, Travis; Ariotti, Nicholas; Parton, Robert G; Hancock, John F

    2014-03-01

    Lipid-anchored Ras GTPases form transient, spatially segregated nanoclusters on the plasma membrane that are essential for high-fidelity signal transmission. The lipid composition of Ras nanoclusters, however, has not previously been investigated. High-resolution spatial mapping shows that different Ras nanoclusters have distinct lipid compositions, indicating that Ras proteins engage in isoform-selective lipid sorting and accounting for different signal outputs from different Ras isoforms. Phosphatidylserine is a common constituent of all Ras nanoclusters but is only an obligate structural component of K-Ras nanoclusters. Segregation of K-Ras and H-Ras into spatially and compositionally distinct lipid assemblies is exquisitely sensitive to plasma membrane phosphatidylserine levels. Phosphatidylserine spatial organization is also modified by Ras nanocluster formation. In consequence, Ras nanoclusters engage in remote lipid-mediated communication, whereby activated H-Ras disrupts the assembly and operation of spatially segregated K-Ras nanoclusters. Computational modeling and experimentation reveal that complex effects of caveolin and cortical actin on Ras nanoclustering are similarly mediated through regulation of phosphatidylserine spatiotemporal dynamics. We conclude that phosphatidylserine maintains the lateral segregation of diverse lipid-based assemblies on the plasma membrane and that lateral connectivity between spatially remote lipid assemblies offers important previously unexplored opportunities for signal integration and signal processing.

  20. Ge nanoclusters in PECVD-deposited glass after heat treating and electron irradiation

    DEFF Research Database (Denmark)

    Ou, Haiyan; Rørdam, Troels Peter; Rottwitt, Karsten

    2007-01-01

    This paper reports the formation of Ge nanoclusters in silica glass thin films deposited by plasma-enhanced chemical vapor deposition (PECVD). We studied the samples by transmission electron microscopy (TEM) and Raman spectroscopy after annealing. TEM investigation shows that the Ge nanoclusters...... at two areaswere formed by different mechanisms. The Ge nanoclusters formed in a single row along the interface of a silicon substrate and the silica glass film by annealing during high-temperature heat treatment. Ge nanoclusters did not initially form in the bulk of the film but could be subsequently...

  1. Nano-clustered Pd catalysts formed on GaN surface for green chemistry

    Science.gov (United States)

    Hirayama, Motoi; Ueta, Yukiko; Konishi, Tomoya; Tsukamoto, Shiro

    2011-05-01

    We have succeeded in observing Pd nano-clusters, catalytic prime elements, on a GaN(0 0 0 1) surface by a scanning tunneling microscope for the first time. After the sample was reused, we found that nano-clusters (width: 11 nm, height: 2.2 nm) existed on the surface which still kept the catalytic activity, resulting that the neutral Pd atoms formed the nano-cluster. Moreover, the S-termination contributed to the formation of the dense and flat structure consisting of the Pd nano-clusters.

  2. On the possibility of controlling the hydrophilic/hydrophobic characteristics of toroid Mo138 nanocluster polyoxometalates

    Science.gov (United States)

    Grzhegorzhevskii, K. V.; Adamova, L. V.; Eremina, E. V.; Ostroushko, A. A.

    2017-03-01

    The possibility of changing the hydrophilic (polar) surfaces of toroid nanocluster polyoxomolibdates to hydrophobic (nonpolar) surfaces via the modification of Mo138 nanoclusters by surfactant molecules (dodecylpyridinium chloride) as a result of the interaction between these compounds in solutions is demonstrated. Benzene and methanol are used as molecular probes (indicators of the condition of nanocluster surfaces). Comparative characteristics of the equilibrium sorption of benzene and methanol vapors on the initial and modified surfaces of the solid polyoxometalate, and data on the sorption of organic molecules on the surfaces of Rhodamine B-modified nanoclusters of the toroid (Mo138) and keplerate (Mo132) types are obtained.

  3. Synthetic Strategies towards Fullerene-Rich Dendrimer Assemblies

    Directory of Open Access Journals (Sweden)

    Jean-François Nierengarten

    2012-02-01

    Full Text Available The sphere-shaped fullerene has attracted considerable interest not least due to the peculiar electronic properties of this carbon allotrope and the fascinating materials emanating from fullerene-derived structures. The rapid development and tremendous advances in organic chemistry allow nowadays the modification of C60 to a great extent by pure chemical means. It is therefore not surprising that the fullerene moiety has also been part of dendrimers. At the initial stage, fullerenes have been examined at the center of the dendritic structure mainly aimed at possible shielding effects as exerted by the dendritic environment and light-harvesting effects due to multiple chromophores located at the periphery of the dendrimer. In recent years, also many research efforts have been devoted towards fullerene-rich nanohybrids containing multiple C60 units in the branches and/or as surface functional groups. In this review, synthetic efforts towards the construction of dendritic fullerene-rich nanostructures have been compiled and will be summarized herein.

  4. Click chemistry with polymers, dendrimers, and hydrogels for drug delivery.

    Science.gov (United States)

    Lallana, Enrique; Fernandez-Trillo, Francisco; Sousa-Herves, Ana; Riguera, Ricardo; Fernandez-Megia, Eduardo

    2012-04-01

    During the last decades, great efforts have been devoted to design polymers for reducing the toxicity, increasing the absorption, and improving the release profile of drugs. Advantage has been also taken from the inherent multivalency of polymers and dendrimers for the incorporation of diverse functional molecules of interest in targeting and diagnosis. In addition, polymeric hydrogels with the ability to encapsulate drugs and cells have been developed for drug delivery and tissue engineering applications. In the long road to this successful story, pharmaceutical sciences have been accompanied by parallel advances in synthetic methodologies allowing the preparation of precise polymeric materials with enhanced properties. In this context, the introduction of the click concept by Sharpless and coworkers in 2001 focusing the attention on modularity and orthogonality has greatly benefited polymer synthesis, an area where reaction efficiency and product purity are significantly challenged. The purpose of this Expert Review is to discuss the impact of click chemistry in the preparation and functionalization of polymers, dendrimers, and hydrogels of interest in drug delivery.

  5. Organometallic Silicon-Containing Dendrimers and Their Electrochemical Applications

    Science.gov (United States)

    Cuadrado, Isabel

    Dendrimers constitute a unique class of macromolecular architectures that differs from all other synthetic macromolecules in its perfectly branched topology, which is constructed from a multifunctional central core and expands to the periphery that becomes denser with increasing generation number (see Chapter 1) [1-5]. Since the pioneering works published in the late 1970s and the mid-1980s [6-8], the design and synthesis of these tree-like, well-defined molecules, which exhibit a unique combination of chemical and physical properties, is a field which has sustained dramatic growth and has generated enthusiastic studies at the frontiers of organic, inorganic, supramolecular and polymer chemistry, and more recently in the fields of nanoscience, biotechnology and medicine [1-5, 9, 10]. Whereas the initial interest in dendrimers was focused on the synthetic and structural characterization challenges that pose their fractal geometries, nanometer sizes and monodisperse nature, in the last decade the emphasis has been placed mainly on modification of the properties of dendritic molecules by their functionalization

  6. Record Multiphoton Absorption Cross-Sections by Dendrimer Organometalation.

    Science.gov (United States)

    Simpson, Peter V; Watson, Laurance A; Barlow, Adam; Wang, Genmiao; Cifuentes, Marie P; Humphrey, Mark G

    2016-02-12

    Large increases in molecular two-photon absorption, the onset of measurable molecular three-photon absorption, and record molecular four-photon absorption in organic π-delocalizable frameworks are achieved by incorporation of bis(diphosphine)ruthenium units with alkynyl linkages. The resultant ruthenium alkynyl-containing dendrimers exhibit strong multiphoton absorption activity through the biological and telecommunications windows in the near-infrared region. The ligated ruthenium units significantly enhance solubility and introduce fully reversible redox switchability to the optical properties. Increasing the ruthenium content leads to substantial increases in multiphoton absorption properties without any loss of optical transparency. This significant improvement in multiphoton absorption performance by incorporation of the organometallic units into the organic π-framework is maintained when the relevant parameters are scaled by molecular weights or number of delocalizable π-electrons. The four-photon absorption cross-section of the most metal-rich dendrimer is an order of magnitude greater than the previous record value.

  7. Enzyme-linked DNA dendrimer nanosensors for acetylcholine

    Science.gov (United States)

    Walsh, Ryan; Morales, Jennifer M.; Skipwith, Christopher G.; Ruckh, Timothy T.; Clark, Heather A.

    2015-10-01

    It is currently difficult to measure small dynamics of molecules in the brain with high spatial and temporal resolution while connecting them to the bigger picture of brain function. A step towards understanding the underlying neural networks of the brain is the ability to sense discrete changes of acetylcholine within a synapse. Here we show an efficient method for generating acetylcholine-detecting nanosensors based on DNA dendrimer scaffolds that incorporate butyrylcholinesterase and fluorescein in a nanoscale arrangement. These nanosensors are selective for acetylcholine and reversibly respond to levels of acetylcholine in the neurophysiological range. This DNA dendrimer architecture has the potential to overcome current obstacles to sensing in the synaptic environment, including the nanoscale size constraints of the synapse and the ability to quantify the spatio-temporal fluctuations of neurotransmitter release. By combining the control of nanosensor architecture with the strategic placement of fluorescent reporters and enzymes, this novel nanosensor platform can facilitate the development of new selective imaging tools for neuroscience.

  8. Oxygen reduction catalyzed by gold nanoclusters supported on carbon nanosheets

    Science.gov (United States)

    Wang, Qiannan; Wang, Likai; Tang, Zhenghua; Wang, Fucai; Yan, Wei; Yang, Hongyu; Zhou, Weijia; Li, Ligui; Kang, Xiongwu; Chen, Shaowei

    2016-03-01

    Nanocomposites based on p-mercaptobenzoic acid-functionalized gold nanoclusters, Au102(p-MBA)44, and porous carbon nanosheets have been fabricated and employed as highly efficient electrocatalysts for oxygen reduction reaction (ORR). Au102(p-MBA)44 clusters were synthesized via a wet chemical approach, and loaded onto carbon nanosheets. Pyrolysis at elevated temperatures led to effective removal of the thiolate ligands and the formation of uniform nanoparticles supported on the carbon scaffolds. The nanocomposite structures were characterized by using a wide range of experimental techniques such as transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, UV-visible absorption spectroscopy, thermogravimetric analysis and BET nitrogen adsorption/desorption. Electrochemical studies showed that the composites demonstrated apparent ORR activity in alkaline media, and the sample with a 30% Au mass loading was identified as the best catalyst among the series, with a performance comparable to that of commercial Pt/C, but superior to those of Au102 nanoclusters and carbon nanosheets alone, within the context of onset potential, kinetic current density, and durability. The results suggest an effective approach to the preparation of high-performance ORR catalysts based on gold nanoclusters supported on carbon nanosheets.Nanocomposites based on p-mercaptobenzoic acid-functionalized gold nanoclusters, Au102(p-MBA)44, and porous carbon nanosheets have been fabricated and employed as highly efficient electrocatalysts for oxygen reduction reaction (ORR). Au102(p-MBA)44 clusters were synthesized via a wet chemical approach, and loaded onto carbon nanosheets. Pyrolysis at elevated temperatures led to effective removal of the thiolate ligands and the formation of uniform nanoparticles supported on the carbon scaffolds. The nanocomposite structures were characterized by using a wide range of experimental techniques such as

  9. Direct Synthesis and Morphological Characterization of Gold-Dendrimer Nanocomposites Prepared Using PAMAM Succinamic Acid Dendrimers: Preliminary Study of the Calcification Potential

    Directory of Open Access Journals (Sweden)

    E. Vasile

    2014-01-01

    Full Text Available Gold-dendrimer nanocomposites were obtained for the first time by a simple colloidal approach based on the use of polyamidoamine dendrimers with succinamic acid terminal groups and dodecanediamine core. Spherical and highly crystalline nanoparticles with dimensions between 3 nm and 60 nm, and size-polydispersity depending on the synthesis conditions, have been generated. The influence of the stoichiometric ratio and the structural and architectural features of the dendrimers on the properties of the nanocomposites has been described. The self-assembling behaviour of these materials produces gold-dendrimer nanostructured porous networks with variable density, porosity, and composition. The investigations of the reaction systems, by TEM, at two postsynthesis moments, allowed to preliminary establish the control over the properties of the nanocomposite products. Furthermore, this study allowed better understanding of the mechanism of nanocomposite generation. Impressively, in the early stages of the synthesis, the organization of gold inside the dendrimer molecules has been evidenced by micrographs. Growth and ripening mechanisms further lead to nanoparticles with typical characteristics. The potential of such nanocomposite particles to induce calcification when coating a polymer substrate was also investigated.

  10. Phosphorus-Based Dendrimer ABP Treats Neuroinflammation by Promoting IL-10-Producing CD4(+) T Cells.

    Science.gov (United States)

    Hayder, Myriam; Varilh, Marjorie; Turrin, Cédric-Olivier; Saoudi, Abdelhadi; Caminade, Anne-Marie; Poupot, Rémy; Liblau, Roland S

    2015-11-09

    Dendrimers are polyfunctional nano-objects of perfectly defined structure that can provide innovative alternatives for the treatment of chronic inflammatory diseases, including multiple sclerosis (MS). To investigate the efficiency of a recently described amino-bis(methylene phosphonate)-capped ABP dendrimer as a potential drug candidate for MS, we used the classical mouse model of MOG35-55-induced experimental autoimmune encephalomyelitis (EAE). Our study provides evidence that the ABP dendrimer prevents the development of EAE and inhibits the progression of established disease with a comparable therapeutic benefit as the approved treatment Fingolimod. We also show that the ABP dendrimer redirects the pathogenic myelin-specific CD4(+) T cell response toward IL-10 production.

  11. Kinetic and thermodynamic study of the transfer of anionic polyamidoamine dendrimers across two immiscible liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Fuentes, Miguel A.; Manriquez, J.; Antano-Lopez, R. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., Parque Tecnologico Queretaro Sanfandila, P.O. Box 064, Pedro Escobedo 76703, Queretaro (Mexico); Godinez, Luis A., E-mail: lgodinez@cideteq.mx [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica S.C., Parque Tecnologico Queretaro Sanfandila, P.O. Box 064, Pedro Escobedo 76703, Queretaro (Mexico)

    2011-10-01

    The kinetics and thermodynamics for the phase transfer of carboxyl-terminated polyamidoamine (PAMAM) dendrimers across the water/dichloroethane interface were analyzed by cyclic voltammetry and electrochemical impedance spectroscopy. A three phase junction was employed by inserting a cylindrical gold electrode through the liquid-liquid interface. The reversible redox species decamethylferrocene (DMFc) was used in the organic phase in order to promote dendrimer transfer. It was found that the electrochemical behaviour of DMFc at the gold/dichloroethane interface depends on the generation and concentration of the dendrimer species in the aqueous phase. In addition, it was observed that the electrochemically driven transfer of these macromolecules corresponds to a quasi-reversible process. The data obtained from thermodynamic studies indicate that dendrimers are transferred between the two phases under study by an entropy controlled process.

  12. Modular degradable dendrimers enable small RNAs to extend survival in an aggressive liver cancer model

    Science.gov (United States)

    Zhou, Kejin; Nguyen, Liem H.; Miller, Jason B.; Yan, Yunfeng; Kos, Petra; Xiong, Hu; Li, Lin; Hao, Jing; Minnig, Jonathan T.; Siegwart, Daniel J.

    2016-01-01

    RNA-based cancer therapies are hindered by the lack of delivery vehicles that avoid cancer-induced organ dysfunction, which exacerbates carrier toxicity. We address this issue by reporting modular degradable dendrimers that achieve the required combination of high potency to tumors and low hepatotoxicity to provide a pronounced survival benefit in an aggressive genetic cancer model. More than 1,500 dendrimers were synthesized using sequential, orthogonal reactions where ester degradability was systematically integrated with chemically diversified cores, peripheries, and generations. A lead dendrimer, 5A2-SC8, provided a broad therapeutic window: identified as potent [EC50 75 mg/kg dendrimer repeated dosing). Delivery of let-7g microRNA (miRNA) mimic inhibited tumor growth and dramatically extended survival. Efficacy stemmed from a combination of a small RNA with the dendrimer’s own negligible toxicity, therefore illuminating an underappreciated complication in treating cancer with RNA-based drugs. PMID:26729861

  13. Theoretical Investigation of Nonlinear Optical Properties of Organic and Transition Metal Hybrid Azobenzene Dendrimers

    Institute of Scientific and Technical Information of China (English)

    LIU Cai-Ping; LIU Ping; WU Ke-Chen

    2008-01-01

    In this work, we report a theoretical exploration of the responses of organic azo-benzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers (GO), and the first, second and third generation (G1, G2 and G3, respectively) are investigated by semi-empirical methods. The calculated results show that the nonlinear optical (NLO)properties of these organic dendrimers are mainly determined by the azobenzene chromospheres.Additionally, the values of β and γ increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers (core-hybrid and branch-end hybrid according to the sites combined with transition metals) are simulated and discussed in detail in the framework of time-dependent density functional theory (TDDFT). The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.

  14. Dendrimers: General Aspects, Applications and Structural Exploitations as Prodrug/ Drug-delivery Vehicles in Current Medicine.

    Science.gov (United States)

    Mariyam, Merina; Ghosal, Kajal; George, Anne; Thomas, Sabu; Kalarikkal, Nandakumar; S Latha, Mahima

    2017-05-11

    Dendrimers are hyper branched macro molecules with well-defined structure and high degree of functionality on the surface. The dendrimer architecture allows control over properties such as shape, size, density, polarity, reactivity, solubility etc. This can be manipulated to design molecules with desired properties in biomedical applications. Recent advancement in correlating structure to biodegradability and invivo performance opens up new avenue for these molecules in biological applications like drug delivery and tissue engineering. The unique structure of dendrimers provides enough attachment sites for drugs in drug delivery applications. It is possible to tune the molecule in such a way as to encapsulate drug molecule outside target area and release in the local environment of targets. This review presents the general aspects of dendrimers and how these properties are exploited for drug delivery applications. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  15. A functionalized fluorescent dendrimer as a pesticide nanocarrier: application in pest control

    Science.gov (United States)

    Liu, Xiaoxia; He, Bicheng; Xu, Zejun; Yin, Meizhen; Yang, Wantai; Zhang, Huaijiang; Cao, Jingjun; Shen, Jie

    2014-12-01

    We report the delivery of a hydrophobic pesticide, thiamethoxam, by water-soluble nanosized cationic dendrimers that contain hydrophobic dendritic polyesters and peripheral amines, demonstrated by DLS, spectral analysis and ITC. The dendrimer-based nanocarrier can efficiently deliver the pesticide into the live cells and largely increase the cytotoxicity of the drug.We report the delivery of a hydrophobic pesticide, thiamethoxam, by water-soluble nanosized cationic dendrimers that contain hydrophobic dendritic polyesters and peripheral amines, demonstrated by DLS, spectral analysis and ITC. The dendrimer-based nanocarrier can efficiently deliver the pesticide into the live cells and largely increase the cytotoxicity of the drug. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05733c

  16. Catalytic Peptide Dendrimers as Artificial Proteins: Functional Selection and Optimization from Combinatorial Libraries

    Institute of Scientific and Technical Information of China (English)

    Jean-Louis Reymond

    2005-01-01

    @@ 1Introduction In de novo protein design one attempts to create artificial proteins with defined structure and function from first principles, usually with the help of trial-and-error procedures that scan a large number of possible amino acid sequences. Our approach to de novo protein design is based on peptide dendrimers. Dendrimers are tree-like structures that adopt a globular or disk-shaped structure as a consequence of topology rather than folding. Our peptide dendrimers are obtained by alternating alpha-aminoacids with branching diaminoacids[1].Dendrimers containing combinations of histidine, serine and aspartate display enzyme-like catalytic properties for the hydrolysis of esters, including enantiomeric discrimination[1d]. The catalytic effect involves cooperative substrate binding and catalysis by a positive dendritic effect[1d].

  17. Synthesis of Dendrimer Containing Dialkylated-fluorene Unit as a Core Chromophore via Click Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Choul; Lee, Jae Wook [Dong-A University, Busan (Korea, Republic of); Jin, Sung Ho [Pusan National University, Busan (Korea, Republic of)

    2012-01-15

    The convergent synthetic strategy for the emissive dendrimers having the chromophore at core via the coppercatalyzed 1,3-dipolar cycloaddition reaction between alkyne and azide was described. 2,7-Diazido-9,9-dioctyl- 9H-fluorene, designed to serve as the core in dendrimer, was stitched with the alkyne-functionalized Frechettype and PAMAM dendrons by the click chemistry leading to the formation of the corresponding fluorescent dendrimers in high yields. The preliminary photoluminescence studies indicated that 2,7-diazido-9,9-dioctyl- 9H-fluorene showed no fluorescence due to the quenching effect from the electron-rich α-nitrogen of the azido group but the dendrimers fluoresced due to the elimination of the quenching through the formation of the triazole ring.

  18. Functional properties of fluorescent poly(amidoamine) dendrimers in nematic liquid crystalline media

    Science.gov (United States)

    Grabchev, Ivo; Sali, Seher; Chovelon, Jean-Marc

    2006-05-01

    The effectiveness of poly(amidoamine) dendrimers from zero generation as a fluorescent guest for liquid crystal displays of the 'guest-host' type is discussed on the basis of their absorption and fluorescent properties. It has been shown that the dendrimers at concentration of 0.3 wt% do not destabilize the orientation of the liquid crystal matrix. The orientation order parameters SA and SF depends on the nature of the substituent at C-4 position of the 1,8-naphthalimide. The effect that poly(amidoamine) dendrimers have upon the phase transition temperature and the electro-optical properties of the LC/dendrimer mixtures has been also presented. All investigations reported have been carried out in surface stabilized display cells.

  19. Brain Targeting of a Water Insoluble Antipsychotic Drug Haloperidol via the Intranasal Route Using PAMAM Dendrimer.

    Science.gov (United States)

    Katare, Yogesh K; Daya, Ritesh P; Sookram Gray, Christal; Luckham, Roger E; Bhandari, Jayant; Chauhan, Abhay S; Mishra, Ram K

    2015-09-01

    Delivery of therapeutics to the brain is challenging because many organic molecules have inadequate aqueous solubility and limited bioavailability. We investigated the efficiency of a dendrimer-based formulation of a poorly aqueous soluble drug, haloperidol, in targeting the brain via intranasal and intraperitoneal administration. Aqueous solubility of haloperidol was increased by more than 100-fold in the developed formulation. Formulation was assessed via different routes of administration for behavioral (cataleptic and locomotor) responses, and for haloperidol distribution in plasma and brain tissues. Dendrimer-based formulation showed significantly higher distribution of haloperidol in the brain and plasma compared to a control formulation of haloperidol administered via intraperitoneal injection. Additionally, 6.7 times lower doses of the dendrimer-haloperidol formulation administered via the intranasal route produced behavioral responses that were comparable to those induced by haloperidol formulations administered via intraperitoneal injection. This study demonstrates the potential of dendrimer in improving the delivery of water insoluble drugs to brain.

  20. Fate and transformation products of amine-terminated PAMAM dendrimers under ozonation and irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Santiago-Morales, Javier [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Rosal, Roberto, E-mail: roberto.rosal@uah.es [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Hernando, María D. [Spanish National Institute for Agricultural and Food Research and Technology – INIA, Crta. de la Coruña, km 7.5, 28040 Madrid (Spain); Ulaszewska, Maria M. [Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); García-Calvo, Eloy [Department of Chemical Engineering, University of Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Fernández-Alba, Amadeo R. [Advanced Study Institute of Madrid, IMDEA Agua, Parque Científico Tecnológico, 28805 Alcalá de Henares, Madrid (Spain); Pesticide Residue Research Group, Department of Hydrogeology and Analytical Chemistry, University of Almería, 04120 Almería (Spain)

    2014-02-15

    Highlights: • We detected transformation products from dendrimer under ozonation and irradiation. • Retro-Michael fragmentation pathway with highly oxygenated structures. • High toxicity of G3 PAMAM dendrimer for green algae. • Reactive oxygen species were associated with the toxic damage. • Transformation mixtures could be more toxic than the parent dendrimer. -- Abstract: This article deals with the degradation of a third-generation (G3) poly(amidoamine) (PAMAM) dendrimer under ozonation and irradiation. The identification and quantification of G3 PAMAM dendrimer and its transformation products has been performed by liquid chromatography–electrospray ionization-hybrid quadrupole time-of-flight-mass spectrometry. The dendrimer was completely depleted by ozone in less than 1 min. The effect of ultraviolet irradiation was attributed to hydroxyl-mediated oxidation. The transformation products were attributed to the oxidation of amines, which resulted in highly oxidized structures with abundance of carboxylic acids, which started from the formation of amine oxide and the scission of the C-N bond of the amide group. We studied the toxicity of treated mixtures for six different organisms: the acute toxicity for the bacterium Vibrio fischeri and the microcrustacean Daphnia magna, the multigenerational growth inhibition of the alga Pseudokirchneriella subcapitata, and the seed germination phytotoxicity of Licopersicon esculentum, Lactuca sativa and Lolium perenne. Ozonation and irradiation originated transformation products are more toxic than the parent dendrimer. The toxicity of the dendrimer for the green alga was linked to a strong increase of intracellular reactive oxygen species with intense lipid peroxidation.

  1. Cobaltocenium-functionalized poly(propylene imine) dendrimers: redox and electromicrogravimetric studies and AFM imaging.

    Science.gov (United States)

    Takada, K; Díaz, D J; Abruña, H D; Cuadrado, I; González, B; Casado, C M; Alonso, B; Morán, M; Losada, J

    2001-03-02

    The first four generations of cobaltocenium-functionalized, diaminobutane-based poly(propylene imine) dendrimers DAB-dend-Cb,(PFb)x (x = 4, 8, 16, and 32; Cb=[Co(eta5-C5H4CONH)(eta5-C5H5)] (1-4) have been synthesized and characterized. The redox activity of the cobaltocenium centers in 1-4 has been characterized by using cyclic voltammetry and the electrochemical quartz-crystal microbalance (EQCM). All of the dendrimers exhibit reversible redox chemistry associated with the cobaltocenium/cobaltocene redox couple. Upon reduction. the dendrimers exhibit a tendency to electrodeposit onto the electrode surface, which is more pronounced for the higher generations. Pt and glassy carbon electrodes could be modified with films derived from 1-4,exhibiting a well-defined and persistent electrochemical response. EQCM measurements show that the dendrimers adsorb, at open circuit, onto platinum surfaces at monolayer or submonolayer coverage. Cathodic potential scanning past -0.75 V at which the cobaltocenium sites are reduced, gave rise to the electrodeposition of multilayer equivalents of the dendrimers. The additional material gradually desorbs upon re-oxidation so that only a monolayer equivalent remains on the electrode surface. Changes in film morphology as a function of dendrimer generation and surface coverage were studied by using admittance measurements of the quartz-crystal resonator on the basis of its electrical equivalent circuit, especially in terms of its resistance parameter. In general, we find that films of the lower dendrimer generation 1 behave rigidly, whereas those of the higher generation 4 exhibit viscoelastic behavior with an intermediate behavior being exhibited by 2 and 3. Using tapping-mode atomic force microscopy (AFM). we have been able to obtain molecularly resolved images of dendrimer 4 adsorbed on a Pt(111) electrode.

  2. The Application of Suzuki Coupling Reaction on the Preparation of Carbosilane Dendrimers with 4-(Naphthalen-1-yl)phenyl Core

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Carbosilane dendrimers with p-bromophenyl core were synthesized by alternating Grignard and hydrosilylation reaction. And the α-naphthalenyl was connected to the core by the Suzuki coupling reaction. A new carbosilane dendrimer with big π-conjugated structure[4-(naphthalen-1-yl)phenyl core] was given. It shows Suzuki coupling reaction is an effective and powerful core-functionalization method and the satisfactory result can be obtained through prolonging the reaction time with the increase of the generation of dendrimer.

  3. A study of many-body phenomena in metal nanoclusters (Au, Cu) close to their transition to the nonmetallic state

    NARCIS (Netherlands)

    Borman, VD; Borisyuk, PV; Lebid'ko, VV; Pushkin, AA; Tronin, VN; Troyan, [No Value; Antonov, DA; Filatov, DO

    2006-01-01

    The results of a study of many-body phenomena in gold and copper nanoclusters are presented. The measured conductivity as a function of nanocluster height h was found to have a minimum at h approximate to 0.6 nm. Conductivity was local in character at nanocluster sizes l infinity) to nonmetallic (ep

  4. Size Dependence of Atomically Precise Gold Nanoclusters in Chemoselective Hydrogenation and Active Site Structure

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gao [Carnegie Mellon University (CMU); Jiang, Deen [ORNL; Kumar, Santosh [Carnegie Mellon University (CMU); Chen, Yuxiang [Carnegie Mellon University (CMU); Jin, Rongchao [Carnegie Mellon University (CMU)

    2014-01-01

    We here investigate the catalytic properties of water-soluble Aun(SG)m nanocluster catalysts (H-SG = glutathione) of different sizes, including Au15(SG)13, Au18(SG)14, Au25(SG)18, Au38(SG)24, and captopril-capped Au25(Capt)18 nanoclusters. These Aun(SR)m nanoclusters (-SR represents thiolate generally) are used as homogeneous catalysts (i.e., without supports) in the chemoselective hydrogenation of 4-nitrobenzaldehyde (4-NO2PhCHO) to 4-nitrobenzyl alcohol (4-NO2PhCH2OH) in water with H2 gas (20 bar) as the hydrogen source. These nanocluster catalysts, except Au18(SG)14, remain intact after the catalytic reaction, evidenced by UV-vis spectra which are characteristic of each sized nanoclusters and thus serve as spectroscopic fingerprints . We observe a drastic size-dependence and steric effect of protecting ligands on the gold nanocluster catalysts in the hydrogenation reaction. Density functional theory (DFT) modeling of the 4-nitrobenzaldehyde adsorption shows that both the CHO and NO2 groups are in close interact with the S-Au-S staples on the gold nanocluster surface; the adsorption of the 4-nitrobenzaldehyde molecule on the four different sized Aun(SR)m nanoclusters are moderately strong and similar in strength. The DFT results suggest that the catalytic activity of the Aun(SR)m nanoclusters is primarily determined by the surface area of the Au nanocluster, consistent with the observed trend of the conversion of 4-nitrobenzaldehyde versus the cluster size. Overall, this work offers the molecular insight into the hydrogenation of 4-nitrobenzaldehyde and the catalytically active site structure on gold nanocluster catalysts.

  5. COMPUTER SIMULATION OF LOCAL MOBILITY IN DENDRIMERS WITH ASYMMETRIC BRANCHING BY BROWNIAN DYNAMICS METHOD

    Directory of Open Access Journals (Sweden)

    O. V. Shavykin

    2016-09-01

    Full Text Available The Brownian dynamics method has been used to study the effect of the branching asymmetry on the local orientational mobility of segments and bonds in dendrimers in good solvent. “Coarse-grained” models of flexible dendrimers with different branching symmetry but with the same average segment length were considered. The frequency dependences of the rate of the spin-lattice relaxation nuclear magnetic resonance (NMR [1/T1H(H] for segments or bonds located at different distances from terminal monomers were calculated. After the exclusion of the contribution of the overall dendrimer rotation the position of the maxima of the frequency dependences [1/T1H(ωH] for different segments with the same length doesn’t depend on their location inside a dendrimer both for phantom models and for models with excluded volume interactions. This effect doesn’t depend also on the branching symmetry, but the position of the maximum [1/T1H(ωH] is determined by the segment length. For bonds inside segments the positions of the maximum [1/T1H(ωH] coincide for all models considered. Therefore, the obtained earlier conclusion about the weak influence of the excluded volume interactions on the local dynamics in the flexible symmetric dendrimers can be generalized for dendrimers with an asymmetric branching.

  6. Synthesis of New Functionalized Citric Acid-based Dendrimers as Nanocarrier Agents for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Sanaz Motamedi

    2011-06-01

    Full Text Available Introduction: Citric acid-polyethylene glycol-citric acid (CPEGC triblock dendrimers can serve as potential delivery systems. Methods: In this investigation, CPEGC triblock dendrimers were synthesized and then imidazole groups were conjugated onto the surface of the G1, G2 and G3 of the obtained dendrimers. In order to study the type of the interactions between the functionalized dendrimers and a drug molecule, Naproxen which contains acidic groups, was examined as a hydrophobic drug in which the interactions would be of the electrostatic kind between its acidic groups and the lone pair electrons of nitrogen atom in imidazole groups. The quantity of the trapped drug and also the amount of its release were measured with UV spectrometric method in pH 1, 7.4 and 10. The average diameter of the nanocarriers was measured by Dynamic Light Scattering (DLS technique Results: The size range of particles was determined to be 16-50 nm for different generations. The rate of the release increased in pH=10 in all generations due to the increase in Naproxen solubility and the hydrolysis of the esteric bonds in the mentioned pH. The results showed that the amount of the trapped drug increased with the increase in the generation of the dendrimer and pH. Conclusion: Based on our findings, we suggest CPEGC triblock dendrimers possess great potential to be used as drug/gene delivery system.

  7. Evaluation of polyamidoamine dendrimers as potential carriers for quercetin, a versatile flavonoid.

    Science.gov (United States)

    Madaan, Kanika; Lather, Viney; Pandita, Deepti

    2016-01-01

    The aim of the present research work was to investigate the potential of polyamidoamine (PAMAM) dendrimers as oral drug delivery carriers for quercetin, a Biopharmaceutical Classification System (BCS) class II molecule. The aqueous solubility of quercetin was investigated in different generations of dendrimers, i.e. G0, G1, G2 and G3, with varying concentrations (0.1, 0.5, 1, 2 and 4 µM). Then, it was successfully incorporated in PAMAM dendrimers and they were characterized for incorporation efficacy, nature of nanoformulations, size, size distribution, surface morphology and stability. In vitro release characteristics of quercetin from all quercetin-PAMAM complexes were studied at 37 °C in phosphate buffer saline (PBS; pH 7.4). Furthermore, the efficacy of quercetin-loaded PAMAM dendrimer was assessed by pharmacodynamic experiment, namely, a carrageenan-induced paw edema model to evaluate the acute activity of this nanocarrier in response to inflammation. It was observed that both generation and the respective concentrations of PAMAM dendrimers showed potential positive effects on solubility enhancement of quercetin. All the quercetin-PAMAM complexes were found to be in nanometeric range (quercetin which was characterized by an initial faster release followed by sustained release phase and pharmacodynamic study provided the preliminary proof of concept about the potential of quercetin-PAMAM complexes. The study concludes that the dendrimer-based drug delivery system for quercetin has enormous potential to resolve the drug delivery issues associated with it.

  8. Precise localization of metal nanoparticles in dendrimer nanosnakes or inner periphery and consequences in catalysis

    Science.gov (United States)

    Liu, Xiang; Gregurec, Danijela; Irigoyen, Joseba; Martinez, Angel; Moya, Sergio; Ciganda, Roberto; Hermange, Philippe; Ruiz, Jaime; Astruc, Didier

    2016-01-01

    Understanding the relationship between the location of nanoparticles (NPs) in an organic matrix and their catalytic performances is essential for catalyst design. Here we show that catalytic activities of Au, Ag and CuNPs stabilized by dendrimers using coordination to intradendritic triazoles, galvanic replacement or stabilization outside dendrimers strongly depends on their location. AgNPs are found at the inner click dendrimer periphery, whereas CuNPs and AuNPs are encapsulated in click dendrimer nanosnakes. AuNPs and AgNPs formed by galvanic replacement are larger than precursors and only partly encapsulated. AuNPs are all the better 4-nitrophenol reduction catalysts as they are less sterically inhibited by the dendrimer interior, whereas on the contrary CuNPs are all the better alkyne azide cycloaddition catalysts as they are better protected from aerobic oxidation inside dendrimers. This work highlights the role of the location in macromolecules on the catalytic efficiency of metal nanoparticles and rationalizes optimization in catalyst engineering. PMID:27759006

  9. Dendrimer nanoscaffolds for potential theranostics of prostate cancer with a focus on radiochemistry.

    Science.gov (United States)

    Lo, Su-Tang; Kumar, Amit; Hsieh, Jer-Tsong; Sun, Xiankai

    2013-03-04

    Dendrimers are a class of structurally defined macromolecules featured with a central core, a low-density interior formed by repetitive branching units, and a high-density exterior terminated with surface functional groups. In contrast to their polymeric counterparts, dendrimers are nanosized and symmetrically shaped, which can be reproducibly synthesized on a large scale with monodispersity. These unique features have made dendrimers of increasing interest for drug delivery and other biomedical applications as nanoscaffold systems. Intended to address the potential use of dendrimers for the development of theranostic agents, which combines therapeutics and diagnostics in a single entity for personalized medicine, this review focuses on the reported methodologies of using dendrimer nanoscaffolds for targeted imaging and therapy of prostate cancer. Of particular interest, relevant chemistry strategies are discussed due to their important roles in the design and synthesis of diagnostic and therapeutic dendrimer-based nanoconjugates and potential theranostic agents, targeted or nontargeted. Given the developing status of nanoscaffolded theranostics, major challenges and potential hurdles are discussed along with the examples representing current advances.

  10. Cationic poly(amidoamine) dendrimers induced cyto-protective autophagy in hepatocellular carcinoma cells

    Science.gov (United States)

    Li, Yubin; Wang, Shaofei; Wang, Ziyu; Qian, Xiaolu; Fan, Jiajun; Zeng, Xian; Sun, Yun; Song, Ping; Feng, Meiqing; Ju, Dianwen

    2014-09-01

    Poly(amidoamine) (PAMAM) dendrimers are proposed as one of the most promising nanomaterials for biomedical applications because of their unique tree-like structure, monodispersity and tunable properties. In this study, we found that PAMAM dendrimers could induce the formation of autophagosomes and the conversion of microtubule-associated protein 1 light chain 3 (LC3) in hepatocellular carcinoma HepG2 cells, while the inhibition of the Akt/mTOR and activation of the Erk 1/2 signaling pathways were involved in autophagy-induced by PAMAM dendrimers. We also investigated the suppression of autophagy with the obviously enhanced cytotoxicity of PAMAM dendrimers. Moreover, the blockage of a reactive oxygen species (ROS) could enhance the growth inhibition and apoptosis of hepatocellular carcinoma cells, induced by PAMAM dendrimers through reducing autophagic effects. Taken together, these findings explored the role and mechanism of autophagy induced by PAMAM dendrimers in HepG2 cells, provided new insight into the effect of autophagy on drug delivery nanomaterials and tumor cells and contributed to the use of a drug delivery vehicle for hepatocellular carcinoma treatment.

  11. Interactions of PAMAM dendrimers with SDS at the solid-liquid interface.

    Science.gov (United States)

    Arteta, Marianna Yanez; Eltes, Felix; Campbell, Richard A; Nylander, Tommy

    2013-05-14

    This work addresses structural and nonequilibrium effects of the interactions between well-defined cationic poly(amidoamine) PAMAM dendrimers of generations 4 and 8 and the anionic surfactant sodium dodecyl sulfate (SDS) at the hydrophilic silica-water interface. Neutron reflectometry and quartz crystal microbalance with dissipation monitoring were used to reveal the adsorption from premixed dendrimer/surfactant solutions as well as sequential addition of the surfactant to preadsorbed layers of dendrimers. PAMAM dendrimers of both generations adsorb to hydrophilic silica as a compact monolayer, and the adsorption is irreversible upon rinsing with salt solution. SDS adsorbs on the dendrimer layer and at low bulk concentrations causes the expansion of the dendrimer layers on the surface. When the bulk concentration of SDS is increased, the surfactant layer consists of aggregates or bilayer-like structures. The adsorption of surfactant is reversible upon rinsing, but slight changes of the structure of the preadsorbed PAMAM monolayer were observed. The adsorption from premixed solutions close to charge neutrality results in thick multilayers, but the surface excess is lower when the bulk complexes have a net negative charge. A critical examination of the pathway of adsorption for the interactions of SDS with preadsorbed PAMAM monolayers and premixed PAMAM/SDS solutions with hydrophilic silica revealed that nonequilibrium effects are important only in the latter case, and the application of a thermodynamic model to such experimental data would be inappropriate.

  12. Monolayers of poly(amido amine) dendrimers on mica - In situ streaming potential measurements.

    Science.gov (United States)

    Michna, Aneta; Adamczyk, Zbigniew; Sofińska, Kamila; Matusik, Katarzyna

    2017-01-01

    The deposition of poly(amido amine) dendrimers on mica at various pHs was studied by the atomic force microscopy (AFM) and in situ streaming potential measurements. Bulk characteristics of dendrimers were acquired by using the dynamic light scattering (DLS) and the laser Doppler velocimetry (LDV). The hydrodynamic radius derived from DLS measurements was 5.2nm for the ionic strength of 10(-2)M and pH range 4-10. The electrophoretic mobility, the zeta potential and the number of electrokinetic charges per molecule were derived as a function of pH from the LDV measurements. It was revealed that the dendrimers are positively charged for pH up to 10. This promoted their deposition on negatively charged mica substrate whose kinetics was quantitatively evaluated by direct AFM imaging and streaming potential measurements interpreted in terms of the electrokinetic model. The desorption kinetics of dendrimers under flowing conditions from monolayers of various coverage was also studied. It was revealed that dendrimer deposition was partially reversible for pH above 5.8. The acid-base properties of the dendrimer monolayers deposited on mica were characterized.

  13. Template free synthesis of natural carbohydrates functionalised fluorescent silver nanoclusters.

    Science.gov (United States)

    Ebrahiminezhad, Alireza; Berenjian, Aydin; Ghasemi, Younes

    2016-06-01

    Template-assisted synthesis is one of the most recognised techniques for fabrication of silver nanoclusters (AgNCs). However, this process is time consuming, toxic and expensive. In this study, the authors report a completely novel approach for the green and facile synthesis of AgNCs using Matricaria chamomilla, without any additional template. Fluorescent and colloidally stable AgNCs with average particle size of 2.4 nm were successfully produced. They found that carbohydrates from Matricaria chamomilla act as an ideal template to generate fluorescent AgNCs. Moreover, oxygen-bearing functional groups were validated to be the active groups for anchoring and reducing of Ag(+) ions. The novel carbohydrate coating method makes the prepared nanoclusters completely hydrophilic and stable in aqueous matrices.

  14. The expanding universe of thiolated gold nanoclusters and beyond.

    Science.gov (United States)

    Jiang, De-en

    2013-08-21

    Thiolated gold nanoclusters form a universe of their own. Researchers in this field are constantly pushing the boundary of this universe by identifying new compositions and in a few "lucky" cases, solving their structures. Such solved structures, even if there are only few, provide important hints for predicting the many identified compositions that are yet to be crystallized or structure determined. Structure prediction is the most pressing issue for a computational chemist in this field. The success of the density functional theory method in gauging the energetic ordering of isomers for thiolated gold clusters has been truly remarkable, but to predict the most stable structure for a given composition remains a great challenge. In this feature article from a computational chemist's point of view, the author shows how one understands and predicts structures for thiolated gold nanoclusters based on his old and new results. To further entertain the reader, the author also offers several "imaginative" structures, claims, and challenges for this field.

  15. Shape and scale dependent diffusivity of colloidal nanoclusters and aggregates

    Science.gov (United States)

    Alcanzare, M. M. T.; Ollila, S. T. T.; Thakore, V.; Laganapan, A. M.; Videcoq, A.; Cerbelaud, M.; Ferrando, R.; Ala-Nissila, T.

    2016-07-01

    The diffusion of colloidal nanoparticles and nanomolecular aggregates, which plays an important role in various biophysical and physicochemical phenomena, is currently under intense study. Here, we examine the shape and size dependent diffusion of colloidal nano- particles, fused nanoclusters and nanoaggregates using a hybrid fluctuating lattice Boltzmann-Molecular Dynamics method. We use physically realistic parameters characteristic of an aqueous solution, with explicitly implemented microscopic no-slip and full-slip boundary conditions. Results from nanocolloids below 10 nm in radii demonstrate how the volume fraction of the hydrodynamic boundary layer influences diffusivities. Full-slip colloids are found to diffuse faster than no-slip particles. We also characterize the shape dependent anisotropy of the diffusion coefficients of nanoclusters through the Green-Kubo relation. Finally, we study the size dependence of the diffusion of nanoaggregates comprising N ≤ 108 monomers and demonstrate that the diffusion coefficient approaches the continuum scaling limit of N-1/3.

  16. Optical properties of Si nanoclusters with passivated surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, L.N. [Univ. of California, Davis, CA (United States). Dept. of Applied Science]|[Lawrence Livermore National Lab., CA (United States). Chemistry and Materials Science Dept.; Chase, L.L.; Balooch, M.; Siekhaus, W.J. [Lawrence Livermore National Lab., CA (United States). Chemistry and Material Science Dept.; Wooten, F. [Univ. of California, Davis, CA (United States). Dept. of Applied Science

    1996-12-31

    Si nanoclusters with average size of a few nanometers have been synthesized by thermal vaporization of Si in an Ar buffer gas, and passivated with oxygen or atomic hydrogen. High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) revealed that these nanoclusters were crystalline. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times form nanoseconds to microseconds depending on synthesis conditions. Absorption mainly in the Si cores was observed by photoluminescence excitation (PLE) spectroscopy. The visible components of PL spectra were noted to blue shift and broaden as the size of the Si nanocrystals (nc-Si) was reduced, and there were differences in PL spectra for hydrogen and oxygen passivated nc-Si. This data can be explained best by a model involving absorption between quantum confined states in the Si cores and emission by surface/interface states.

  17. Catalytically highly active top gold atom on palladium nanocluster.

    Science.gov (United States)

    Zhang, Haijun; Watanabe, Tatsuya; Okumura, Mitsutaka; Haruta, Masatake; Toshima, Naoki

    2011-10-23

    Catalysis using gold is emerging as an important field of research in connection with 'green' chemistry. Several hypotheses have been presented to explain the markedly high activities of Au catalysts. So far, the origin of the catalytic activities of supported Au catalysts can be assigned to the perimeter interfaces between Au nanoclusters and the support. However, the genesis of the catalytic activities of colloidal Au-based bimetallic nanoclusters is unclear. Moreover, it is still a challenge to synthesize Au-based colloidal catalysts with high activity. Here we now present the 'crown-jewel' concept (Supplementary Fig. S1) for preparation of catalytically highly Au-based colloidal catalysts. Au-Pd colloidal catalysts containing an abundance of top (vertex or corner) Au atoms were synthesized according to the strategy on a large scale. Our results indicate that the genesis of the high activity of the catalysts could be ascribed to the presence of negatively charged top Au atoms.

  18. Ultrasonic synthesis and spectral characterization of a new blue fluorescent dendrimer as highly selective chemosensor for Fe3+ cations

    Science.gov (United States)

    Staneva, Desislava; Bosch, Paula; Grabchev, Ivo

    2012-05-01

    A poly(propyleneamine) dendrimer, comprising four 4-(N,N-dimethylaminoethyloxy)-1,8-naphthalimide units in the dendrimer periphery has been synthesized for the first time. The new blue fluorescent dendrimer has been obtained by nucleophilic substitution of the nitro groups at C-4 position of 1,8-naphthalimide units by N,N-dimethylaminoethyloxy moiety under ultrasonic conditions. Its photophysical characteristics have been investigated in organic solvents of different polarity. The influence of different metal cations on the dendrimer fluorescence has been also investigated viewing its sensor potential.

  19. Principal physicochemical methods used to characterize dendrimer molecule complexes used as genetic therapy agents, nanovaccines or drug carriers.

    Science.gov (United States)

    Alberto, Rodríguez Fonseca Rolando; Joao, Rodrigues; de Los Angeles, Muñoz-Fernández María; Alberto, Martínez Muñoz; Jonathan, Fragoso Vázquez Manuel; José, Correa Basurto

    2017-02-20

    Nanomedicine is the application of nanotechnology to medicine. This field is related to the study of nanodevices and nanomaterials applied to various medical uses, such as in improving the pharmacological properties of different molecules. Dendrimers are synthetic nanoparticles whose physicochemical properties vary according to their chemical structure. These molecules have been extensively investigated as drug nanocarriers to improve drug solubility and as sustained-release systems. New therapies such as gene therapy and the development of nanovaccines can be improved by the use of dendrimers. The biophysical and physicochemical characterization of nucleic acid/peptide-dendrimer complexes is crucial to identify their functional properties prior to biological evaluation. In that sense, it is necessary to first identify whether the peptide-dendrimer or nucleic acid-dendrimer complexes can be formed and whether the complex can dissociate under the appropriate conditions at the target cells. In addition, biophysical and physicochemical characterization is required to determine how long the complexes remain stable, what proportion of peptide or nucleic acid is required to form the complex or saturate the dendrimer, and the size of the complex formed. In this review, we present the latest information on characterization systems for dendrimer-nucleic acid, dendrimer-peptide and dendrimer-drug complexes with several biotechnological and pharmacological applications.

  20. Optimal control of electromagnetic field using metallic nanoclusters

    Science.gov (United States)

    Grigorenko, Ilya; Haas, Stephan; Balatsky, Alexander; Levi, A. F. J.

    2008-04-01

    The dielectric properties of metallic nanoclusters in the presence of an applied electromagnetic field are investigated using the non-local linear response theory. In the quantum limit we find a nontrivial dependence of the induced field and charge distributions on the spatial separation between the clusters and on the frequency of the driving field. Using a genetic algorithm, these quantum functionalities are exploited to custom-design sub-wavelength lenses with a frequency-controlled switching capability.

  1. Mossbauer Characterization of Iron Oxide Nanoclusters Grown within Aluminosilicate Matrices

    Science.gov (United States)

    2003-01-01

    2Facultad de Ciencias Fisicas , Universidad Mayor de San Marcos, Lima, Peru. 3Centro Brasileiro de Pesquisas Fisicas , Rio de Janeiro, Brasil. ABSTRACT...nanoclusters. Zeolitic and sol-gel derived molecular sieves and a variety of cross-linked and block co-polymers have been used to this purpose [1-41. The...Brasileiro de Pesquisas Fisicas and the NSF: DMR 0074537 for support. Figures 1 and 2 ame reprinted with permission from reference [I]. Copyright 2001

  2. Preparation of nanocomposites containing nanoclusters of transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Milne, S.B.; Lukehart, C.M., Wittig, J.E. [Vanderbilt Univ., Nashville, TN (United States)] [and others

    1996-10-01

    New nanocomposites containing nanoclusters of transition metals have been prepared and characterized by TEM, XRD, and energy dispersive spectroscopy. Organometallic or other coordination compounds functionalized with trialkoxysilyl groups have been synthesized and covalently incorporated into silica xerogels using standard sol-gel techniques. Thermal oxidative treatment of these xerogels in air followed by reduction in hydrogen yielded the desired nanocomposite phases. Using these methods, Mo, Re, Fe, Ru, Os, Pd, Pt, Cu. and Ag nanocomposites have been prepared.

  3. DNase 1 Retains Endodeoxyribonuclease Activity Following Gold Nanocluster Synthesis

    Science.gov (United States)

    2014-07-04

    Gatan). Microscopy samples were prepared for analysis through the following steps: (i) bulk material was ground up using a mortar and pestle , (ii...employed as efficient and fast sensors to augment the current time-consuming DNA contamination analysis techniques. Noble metal nanoclusters (NCs...to metal nanoparticles (NPs), which do not exhibit fluorescence but show plasmonic transitions involving surface electrons. By definition , NCs are

  4. Theory of Nanocluster Size Distributions from Ion Beam Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-06-13

    Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.

  5. Live Cell Surface Labeling with Fluorescent Ag Nanocluster Conjugates†

    OpenAIRE

    Yu, Junhua; Choi, Sungmoon; Richards, Chris I.; Antoku, Yasuko; Dickson, Robert M

    2008-01-01

    DNA-encapsulated silver clusters are readily conjugated to proteins and serve as alternatives to organic dyes and semiconductor quantum dots. Stable and bright on the bulk and single molecule levels, Ag nanocluster fluorescence is readily observed when staining live cell surfaces. Being significantly brighter and more photostable than organics and much smaller than quantum dots with a single point of attachment, these nanomaterials offer promising new approaches for bulk and single molecule b...

  6. Hyperspherical and related views of the dynamics of nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Lombardi, A; Palazzetti, F; Grossi, G; Aquilanti, V [Dipartimento di Chimica, Universita di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy); Castro Palacio, J C [Departamento de FI sica, Universidad de Pinar del Rio, MartI 270, Esq. 27 de Noviembre, Pinar del Rio (Cuba); Rubayo Soneira, J [Departamento de Fisica General y Matema ticas, Instituto Superior de Ciencias y Tecnologia Nucleares, Quinta de los Molinos, Avenne Carlos III y Luaces, Plaza C. Habana (Cuba)], E-mail: abulafia@dyn.unipg.it

    2009-10-15

    In this paper, we give an account of recent progress in understanding properties of nanoaggregates, following their dynamical behavior by classical mechanics simulations and utilizing tools based on extensions of hyperspherical and related techniques, originally developed for the quantum mechanical treatment of few-body atomic and molecular systems. After an outline of the underlying theory, recent applications exemplifying statistical and thermodynamic aspects of nanoclusters are discussed.

  7. In-vitro Synthesis of Gold Nanoclusters in Neurons

    Science.gov (United States)

    2016-04-01

    Pradeep T. Protein-protected luminescent noble metal quantum clusters : an emerging trend in atomic cluster nanoscience. Nano Rev. 2012;3:14767−14783. 2...5 Approved for public release; distribution is unlimited. 1 1. Introduction Noble metal nanoclusters (NCs) composed of...toxic to the cells based on the results from the 100-mM solutions discussed previously. Potentially, other cell lines might yield brighter clusters

  8. Observation of Body-Centered Cubic Gold Nanocluster.

    Science.gov (United States)

    Liu, Chao; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Pang, Guangsheng; Rosi, Nathaniel L; Jin, Rongchao

    2015-08-17

    The structure of nanoparticles plays a critical role in dictating their material properties. Gold is well known to adopt face-centered cubic (fcc) structure. Herein we report the first observation of a body-centered cubic (bcc) gold nanocluster composed of 38 gold atoms protected by 20 adamantanethiolate ligands and two sulfido atoms ([Au38S2(SR)20], where R=C10H15) as revealed by single-crystal X-ray crystallography. This bcc structure is in striking contrast with the fcc structure of bulk gold and conventional Au nanoparticles, as well as the bi-icosahedral structure of [Au38(SCH2CH2Ph)24]. The bcc nanocluster has a distinct HOMO-LUMO gap of ca. 1.5 eV, much larger than the gap (0.9 eV) of the bi-icosahedral [Au38(SCH2CH2Ph)24]. The unique structure of the bcc gold nanocluster may be promising in catalytic applications.

  9. Ab Initio Calculations for the Surface Energy of Silver Nanoclusters

    Science.gov (United States)

    Medasani, Bharat; Vasiliev, Igor; Park, Young Ho

    2007-03-01

    We apply first principles computational methods to study the surface energy and the surface stress of silver nanoparticles. The structures, energies and lattice contractions of spherical Ag nanoclusters are calculated in the framework of density functional theory combined with the generalized gradient approximation. Our calculations predict the surface energies of Ag nanoclusters to be in the range of 1-2 J/m^2. These values are close to the bulk surface energy of silver, but are significantly lower than the recently reported value of 7.2 J/m^2 derived from the Kelvin equation for free Ag nanoparticles. From the lattice contraction and the nearest neighbor interatomic distance, we estimate the surface stress of the silver nanoclusters to be in the the range of 1-1.45 N/m. This result suggests that a liquid droplet model can be employed to evaluate the surface energy and the surface stress of Ag nanoparticles. K. K. Nanda et al., Phys. Rev. Lett. 91, 106102 (2003).

  10. Polyethyleneimine Capped Silver Nanoclusters as Efficient Antibacterial Agents.

    Science.gov (United States)

    Xu, Dong; Wang, Qingyun; Yang, Tao; Cao, Jianzhong; Lin, Qinlu; Yuan, Zhiqin; Li, Le

    2016-03-18

    Development of efficient antibacterial agents is critical for human health. In the present study, we investigated the antibacterial activity of polyethyleneimine (PEI)-capped silver nanoclusters (PEI-AgNCs), based on the fact that nanoclusters normally have higher surface-to-volume ratios than traditional nanomaterials and PEI itself has a strong antimicrobial capacity. We synthesized stable silver nanoclusters by altering PEI molecular weight from 0.6 kDa to 25 kDa and characterized them by UV-Vis absorption and fluorescence spectroscopy and high resolution transmission electron microscopy. The sizes of AgNCs were around 2 nm in diameter and were little influenced by the molecular weight of PEIs. The antibacterial abilities of the four PEI-AgNCs were explored on agar plate and in liquid systems. Our results revealed that the antibacterial activity of PEI-AgNCs is excellent and the reduction of PEI molecular weight could result in the increased antibacterial capacity of PEI-AgNCs. Such proposed new materials might be useful as efficient antibacterial agents in practical clinical applications.

  11. Magnetic endohedral transition-metal-doped semiconducting-nanoclusters.

    Science.gov (United States)

    Matxain, Jon M; Formoso, Elena; Mercero, Jose M; Piris, Mario; Lopez, Xabier; Ugalde, Jesus M

    2008-01-01

    Endohedral first-row transition-metal-doped TM@Zn(i)S(i) nanoclusters, in which TM stands for the first-row transition-metals from Sc to Zn, and i=12, 16, have been characterized. In these structures the dopant metals are trapped inside spheroidal hollow semiconducting nanoclusters. It is observed that some of the transition metals are trapped in the center of mass of the cluster, whereas others are found to be displaced from that center, leading to structures in which the transition metals display a complex dynamical behavior upon encapsulation. This fact was confirmed by quantum molecular dynamics calculations, which further confirmed the thermal stability of endohedral compounds. In the endohedrally-doped nanoclusters in which the transition-metal atom sits on the center of mass, the host hollow cluster structure remains undistorted after dopant encapsulation. Conversely, if the encapsulated transition-metal atom is displaced from the center of mass, the host hollow cluster structure suffers a very tiny distortion. Additionally, it is found that there is negligible charge transfer between the dopant transition-metal atom and its hollow cluster host and, after encapsulation, the spin densities remain localized on the transition-metal atom. This allows for the atomic-like behavior of the trapped transition-metal atom, which gives rise to their atomic-like magnetic properties. The encapsulation free energies are negative, suggesting that these compounds are thermodynamically stable.

  12. Synthesis of bimetallic gold-silver alloy nanoclusters by simple mortar grinding.

    Science.gov (United States)

    Murugadoss, Arumugam; Kai, Noriko; Sakurai, Hidehiro

    2012-02-21

    A macroscale quantity of bimetallic Au-Ag alloy nanoclusters was achieved through sequential reduction by simple mortar grinding. The chitosan biopolymer was used as both a stabilizing and reducing agent. These nanoclusters exhibit excellent catalytic activity toward the reduction of 4-nitrophenol.

  13. Organic Inorganic Hybrid Solar Cell Efficiency Improvement By Employing Au Nanocluster

    Science.gov (United States)

    2015-06-14

    Specialists Conference Conference Date: June 14, 2015 Organic - Inorganic Hybrid Solar Cell Efficiency Improvement by Employing Au Nanocluster Manisha...tunable conductivity, organic polymer, heterojunction, nanocluster I. INTRODUCTION Recently, organic / inorganic hybrid heterojunction solar cells have...conventional Si p−n junction. These heterojunction devices are intended to exploit the advantageous properties of both organic and inorganic materials

  14. Controlling embedment and surface chemistry of nanoclusters in metal-organic frameworks.

    Science.gov (United States)

    Coupry, D E; Butson, J; Petkov, P S; Saunders, M; O'Donnell, K; Kim, H; Buckley, C; Addicoat, M; Heine, T; Szilágyi, P Á

    2016-04-14

    A combined theoretical and experimental approach demonstrates that nanocluster embedment into the pores of metal-organic frameworks (MOF) may be influenced by the chemical functionalisation of the MOF. Furthermore, this results in the surface functionalisation of the embedded nanoclusters, highlighting the potential of MOF scaffolds for the design and synthesis of novel functional materials.

  15. Controlled doping by self-assembled dendrimer-like macromolecules.

    Science.gov (United States)

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-02-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 10(17) cm(-3). Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.

  16. Charge Transport in Dendrimer Melt using Multiscale Modeling Simulation

    CERN Document Server

    Bag, Saientan; Maiti, Prabal K

    2016-01-01

    In this paper we present a theoretical calculation of the charge carrier mobility in two different dendrimeric melt system (Dendritic phenyl azomethine with Triphenyl amine core and Dendritic Carbazole with Cyclic Phenylazomethine as core), which have recently been reported1 to increase the efficiency of Dye-Sensitized solar cells (DSSCs) by interface modification. Our mobility calculation, which is a combination of molecular dynamics simulation, first principles calculation and kinetic Monte Carlo simulation, leads to mobilities that are in quantitative agreement with available experimental data. We also show how the mobility depends on the dendrimer generation. Furthermore, we examine the variation of mobility with external electric field and external reorganization energy. Physical mechanisms behind observed electric field and generation dependencies of mobility are also explored.

  17. Dendrimer light-harvesting: intramolecular electrodynamics and mechanisms.

    Science.gov (United States)

    Andrews, David L; Bradshaw, David S; Jenkins, Robert D; Rodríguez, Justo

    2009-12-01

    In the development of highly efficient materials for harvesting solar energy, there is an increasing focus on purpose-built dendrimers and allied multi-chromophore systems. A proliferation of antenna chromophores is not the only factor determining the sought light-harvesting efficiency; the internal geometry and photophysics of these molecules are also crucially important. In particular, the mechanisms by means of which radiant energy is ultimately trapped depends on an intricate interplay of electronic, structural, energetic and symmetry properties. To better understand these processes a sound theoretical representation of the intramolecular electrodynamics is required. A suitable formalism, based on quantum electrodynamics, readily delivers physical insights into the necessary excitation channelling processes, and it affords a rigorous basis for modelling the intramolecular flow of energy.

  18. Controlled doping by self-assembled dendrimer-like macromolecules

    Science.gov (United States)

    Wu, Haigang; Guan, Bin; Sun, Yingri; Zhu, Yiping; Dan, Yaping

    2017-02-01

    Doping via self-assembled macromolecules might offer a solution for developing single atom electronics by precisely placing individual dopants at arbitrary location to meet the requirement for circuit design. Here we synthesize dendrimer-like polyglycerol macromolecules with each carrying one phosphorus atom in the core. The macromolecules are immobilized by the coupling reagent onto silicon surfaces that are pre-modified with a monolayer of undecylenic acid. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) are employed to characterize the synthesized macromolecules and the modified silicon surfaces, respectively. After rapid thermal annealing, the phosphorus atoms carried by the macromolecules diffuse into the silicon substrate, forming dopants at a concentration of 1017 cm‑3. Low-temperature Hall effect measurements reveal that the ionization process is rather complicated. Unlike the widely reported simple ionization of phosphorus dopants, nitrogen and carbon are also involved in the electronic activities in the monolayer doped silicon.

  19. Macromolecular and dendrimer-based magnetic resonance contrast agents

    Energy Technology Data Exchange (ETDEWEB)

    Bumb, Ambika; Brechbiel, Martin W. (Radiation Oncology Branch, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States)), e-mail: pchoyke@mail.nih.gov; Choyke, Peter (Molecular Imaging Program, National Cancer Inst., National Inst. of Health, Bethesda, MD (United States))

    2010-09-15

    Magnetic resonance imaging (MRI) is a powerful imaging modality that can provide an assessment of function or molecular expression in tandem with anatomic detail. Over the last 20-25 years, a number of gadolinium-based MR contrast agents have been developed to enhance signal by altering proton relaxation properties. This review explores a range of these agents from small molecule chelates, such as Gd-DTPA and Gd-DOTA, to macromolecular structures composed of albumin, polylysine, polysaccharides (dextran, inulin, starch), poly(ethylene glycol), copolymers of cystamine and cystine with GD-DTPA, and various dendritic structures based on polyamidoamine and polylysine (Gadomers). The synthesis, structure, biodistribution, and targeting of dendrimer-based MR contrast agents are also discussed

  20. Aqueous synthesis of ZnTe/dendrimer nanocomposites and their antimicrobial activity: implications in therapeutics

    Science.gov (United States)

    Ghosh, S.; Ghosh, D.; Bag, P. K.; Bhattacharya, S. C.; Saha, A.

    2011-03-01

    The present strategy proposes a simple and single step aqueous route for synthesizing stable, fluorescent ZnTe/dendrimer nanocomposites with varying dendrimer terminal groups. In these hybrid materials, the fluorescence of the semiconductor combines with the biomimetic properties of the dendrimer making them suitable for various biomedical applications. The ZnTe nanocomposites thus obtained demonstrate bactericidal activity against enteropathogenic bacteria without having toxic effects on the human erythrocytes. The average size of the ZnTe nanoparticles within the dendrimer matrix was in the range of 2.9-6.0 nm, and they have a good degree of crystallinity with a hexagonal crystal phase. The antibacterial activities of the ZnTe/dendrimer nanocomposites (ZnTe DNCs) as well other semiconductor nanocomposites were evaluated against enteropathogenic bacteria including multi-drug resistant Vibrio cholerae serogroup O1 and enterotoxigenic Escherichia coli (ETEC). ZnTe DNCs had significant antibacterial activity against strains of V. cholerae and ETEC with minimum inhibitory concentrations ranging from 64 to 512 μg ml-1 and minimum bactericidal concentrations ranging from 128 to 1000 μg ml-1. Thus, the observed results suggest that these water-soluble active nanocomposites have potential for the treatment of enteric diseases like diarrhoea and cholera.The present strategy proposes a simple and single step aqueous route for synthesizing stable, fluorescent ZnTe/dendrimer nanocomposites with varying dendrimer terminal groups. In these hybrid materials, the fluorescence of the semiconductor combines with the biomimetic properties of the dendrimer making them suitable for various biomedical applications. The ZnTe nanocomposites thus obtained demonstrate bactericidal activity against enteropathogenic bacteria without having toxic effects on the human erythrocytes. The average size of the ZnTe nanoparticles within the dendrimer matrix was in the range of 2.9-6.0 nm, and they

  1. Use of carbosilane dendrimer to switch macrophage polarization for the acquisition of antitumor functions

    Science.gov (United States)

    Perisé-Barrios, Ana J.; Gómez, Rafael; Corbí, Angel L.; de La Mata, Javier; Domínguez-Soto, Angeles; Muñoz-Fernandez, María A.

    2015-02-01

    Tumor microenvironment favors the escape from immunosurveillance by promoting immunosuppression and blunting pro-inflammatory responses. Since most tumor-associated macrophages (TAM) exhibit an M2-like tumor cell growth promoting polarization, we have studied the role of 2G-03NN24 carbosilane dendrimer in M2 macrophage polarization to evaluate the potential application of dendrimers in tumor immunotherapy. We found that the 2G-03NN24 dendrimer decreases LPS-induced IL-10 production from in vitro generated monocyte-derived M2 macrophages, and also switches their gene expression profile towards the acquisition of M1 polarization markers (INHBA, SERPINE1, FLT1, EGLN3 and ALDH1A2) and the loss of M2 polarization-associated markers (EMR1, IGF1, FOLR2 and SLC40A1). Furthermore, 2G-03NN24 dendrimer decreases STAT3 activation. Our results indicate that the 2G-03NN24 dendrimer can be a useful tool for antitumor therapy by virtue of its potential ability to limit the M2-like polarization of TAM.Tumor microenvironment favors the escape from immunosurveillance by promoting immunosuppression and blunting pro-inflammatory responses. Since most tumor-associated macrophages (TAM) exhibit an M2-like tumor cell growth promoting polarization, we have studied the role of 2G-03NN24 carbosilane dendrimer in M2 macrophage polarization to evaluate the potential application of dendrimers in tumor immunotherapy. We found that the 2G-03NN24 dendrimer decreases LPS-induced IL-10 production from in vitro generated monocyte-derived M2 macrophages, and also switches their gene expression profile towards the acquisition of M1 polarization markers (INHBA, SERPINE1, FLT1, EGLN3 and ALDH1A2) and the loss of M2 polarization-associated markers (EMR1, IGF1, FOLR2 and SLC40A1). Furthermore, 2G-03NN24 dendrimer decreases STAT3 activation. Our results indicate that the 2G-03NN24 dendrimer can be a useful tool for antitumor therapy by virtue of its potential ability to limit the M2-like polarization of TAM

  2. Clustomesogens: Liquid Crystalline Hybrid Nanomaterials Containing Functional Metal Nanoclusters.

    Science.gov (United States)

    Molard, Yann

    2016-08-16

    Inorganic phosphorescent octahedral metal nanoclusters fill the gap between metal complexes and nanoparticles. They are finite groups of metal atoms linked by metal-metal bonds, with an exact composition and structure at the nanometer scale. As their phosphorescence internal quantum efficiency can approach 100%, they represent a very attractive class of molecular building blocks to design hybrid nanomaterials dedicated to light energy conversion, optoelectronic, display, lighting, or theragnostic applications. They are obtained as AnM6X(i)8X(a)6 ternary salt powders (A = alkali cation, M = Mo, Re, W, X(i): halogen inner ligand, X(a) = halogen apical ligand) by high temperature solid state synthesis (750-1200 °C). However, their ceramic-like behavior has largely restricted their use as functional components in the past. Since these last two decades, several groups, including ours, started to tackle the challenge of integrating them in easy-to-process materials. Within this context, we have extensively explored the nanocluster ternary salt specificities to develop a new class of self-organized hybrid organic-inorganic nanomaterials known as clustomesogens. These materials, combine the specific properties of nanoclusters (magnetic, electronic, luminescence) with the anisotropy-related properties of liquid crystals (LCs). This Account covers the research and development of clustomesogens starting from the design concepts and synthesis to their introduction in functional devices. We developed three strategies to build such hybrid super- or supramolecules. In the covalent approach, we capitalized on the apical ligand-metal bond iono-covalent character to graft tailor-made organic LC promoters on the {M6X(i)8}(n+) nanocluster cores. The supramolecular approach relies on the host-guest complexation of the ternary cluster salt alkali cations with functional crown ether macrocycles. We showed that the hybrid LC behavior depends on the macrocycles structural features

  3. Synthesis and Doping of Ligand-Protected Atomically-Precise Metal Nanoclusters

    KAUST Repository

    Aljuhani, Maha A.

    2016-05-01

    Rapidly expanding research in nanotechnology has led to exciting progress in a versatile array of applications from medical diagnostics to catalysis. This success resulted from the manipulation of the desired properties of nanomaterials by controlling their size, shape, and composition. Among the most thriving areas of research about nanoparticle is the synthesis and doping of the ligand-protected atomically-precise metal nanoclusters. In this thesis, we developed three different novel metal nanoclusters, such as doped Ag29 with five gold (Au) atoms leading to enhance its quantum yield with remarkable stability. We also developed half-doped (alloyed) cluster of Ni6 nanocluster with molybdenum (Mo). This enabled enhanced stability and better catalytic activity. The third metal nanocluster that we synthesized was Au28 nanocluster by using di-thiolate as the ligand stabilizer instead of mono-thiolate. The new metal clusters obtained have been characterized by spectroscopic, electrochemical and crystallographic methods.

  4. Quantum-sized gold nanoclusters: bridging the gap between organometallics and nanocrystals.

    Science.gov (United States)

    Jin, Rongchao; Zhu, Yan; Qian, Huifeng

    2011-06-06

    This Concept article provides an elementary discussion of a special class of large-sized gold compounds, so-called Au nanoclusters, which lies in between traditional organogold compounds (e.g., few-atom complexes, 2 nm). The discussion is focused on the relationship between them, including the evolution from the Au⋅⋅⋅Au aurophilic interaction in Au(I) complexes to the direct Au-Au bond in clusters, and the structural transformation from the fcc structure in nanocrystals to non-fcc structures in nanoclusters. Thiolate-protected Au(n)(SR)(m) nanoclusters are used as a paradigm system. Research on such nanoclusters has achieved considerable advances in recent years and is expected to flourish in the near future, which will bring about exciting progress in both fundamental scientific research and technological applications of nanoclusters of gold and other metals.

  5. One-step facile synthesis of Pd nanoclusters supported on carbon and their electrochemical property

    Directory of Open Access Journals (Sweden)

    Junjun Shi

    2014-12-01

    Full Text Available Well-crystallized Pd nanoclusters supported on Ketjen Black (KB were successfully fabricated when Pd wires were served as an electrode pair by a solution plasma technique at atmospheric pressure. The synthesis of Pd nanoclusters was almost simultaneous with their dispersion on KB. Pd nanoclusters with the average diameter of about 2 nm were equably distributed on KB, and showed good electrochemical property corresponding to their obvious characteristic peaks. Multi-scan cyclic voltammetry and chronoamperometry clarified that as-prepared Pd nanoclusters have better electrochemical stability in alkaline solution than that of in acidic solution. Thus as-obtained Pd nanoclusters would become a promising electrocatalyst for fuel cells or Li-air batteries.

  6. A PEM fuel cell based on electrocatalyst and membrane materials modified by PANAM dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Ledesma-Garcia, J.; Chapman, T.W.; Godinez, L.A. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Queretaro (Mexico)

    2008-10-15

    Due to its high energy conversion efficiency and low emission of pollutants, fuel-cell technology has been generally recognized as a key twenty-first century energy source. For polymer electrolyte membrane fuel cells (PEMFC), it has been found that platinum and its alloys exhibit the best electrocatalytic activity for oxygen reduction. The highest electrocatalytic activity of platinum and its alloys can be achieved when the particles are produced in the nanometer range. In this context, organic molecules have been adopted as templates to control the size of metal nanoparticles. Dendrimers, in particular, have shown promising properties for this application, and strategies that include direct adsorption, electrostatic attachment and covalent bonding have been developed for connecting metal-bearing dendrimers to conducting substrates. This paper reported on the preliminary results of a study that involved the construction and testing of a hydrogen-oxygen PEM fuel cell based on carbon-fiber-paper electrodes coated with hydroxyl-terminated dendrimers that encapsulated nanoparticles of platinum. This prototype cell also employed an ion exchange membrane comprising a cellulose acetate filter functionalized with proton-exchanging dendrimers. A proton-exchange membrane was prepared by binding duplex amine-carboxylate dendrimers to a cellulose-acetate support. With these dendrimer-based materials, a hydrogen-oxygen fuel cell was assembled and the performance compared with cells prepared with Nafion-based membranes. The voltage-current profiles and the power-density curves from the new cell provide encouragement to continue work with these dendrimer-modified materials. The paper discussed the experimental methods, with particular reference to materials; electrode preparation and characterization; proton-exchange membrane preparation; and PEM fuel-cell assembly and testing. It was concluded that the use of the dendritic macromolecules as supports for the nanoparticulate

  7. Modified PAMAM dendrimer with 4-carbomethoxypyrrolidone surface groups reveals negligible toxicity against three rodent cell-lines

    DEFF Research Database (Denmark)

    Janaszewska, Anna; Ciolkowski, Michal; Wróbel, Dominika;

    2013-01-01

    Modification of the surface groups of dendrimers is one of the methods to improve their biocompatibility. This article presents results of experiments related to the toxicity of a modified polyamidoamine (PAMAM) dendrimer of the fourth generation with 4-carbomethoxypyrrolidone surface groups (PAM...

  8. Electrochemistry of ferrocenyl dendrimer-beta-cyclodextrin assemblies at the interface of an aqueous solution and a molecular printboard

    NARCIS (Netherlands)

    Nijhuis, C.A.; Boukamp, Bernard A.; Ravoo, B.J.; Huskens, Jurriaan; Reinhoudt, David

    2007-01-01

    Water-soluble supramolecular assemblies of redox-active ferrocenyl-decorated (Fc) poly(propylene imine) (PPI) dendrimers and β-cyclodextrin (βCD) were adsorbed at self-assembled monolayers (SAMs) of βCD (“molecular printboards”). The dendrimers form a stable monolayer at the βCD SAM owing to

  9. Microphase separation of diblock copolymers consisting of polystyrene and acid-functionalized poly(propylene imine) dendrimers

    NARCIS (Netherlands)

    Román, C.; Fischer, H.R.; Meijer, E.W.

    1999-01-01

    Diblock copolymers consisting of polystyrene and acid-functionalized poly(propylene imine) dendrimers have been found to self-assemble spontaneously into regular microdomains. The hybride dendrimer-linear chain block copolymers yield highly asymmetric molecules which display an aggregation behavior

  10. Selective synthesis of Rh5 carbonyl clusters within a polyamine dendrimer for chemoselective reduction of nitro aromatics.

    Science.gov (United States)

    Maeno, Zen; Mitsudome, Takato; Mizugaki, Tomoo; Jitsukawa, Koichiro; Kaneda, Kiyotomi

    2014-06-21

    The selective synthesis of the [Rh5(CO)15](-) cluster within the PPI dendrimer was successfully demonstrated. The dendrimer-encapsulated [Rh5(CO)15](-) was resistant to decomposition under the catalytic reaction conditions and exhibited extremely high selectivity for the chemoselective reduction of nitro groups of various nitro aromatics with other reducible groups using CO/H2O as a reductant.

  11. Poly(dendrimers) with phosphorescent iridium(III) complex-based side chains prepared via ring-opening metathesis polymerization

    NARCIS (Netherlands)

    Lai, W.-Y.; Balfour, M.N.; Levell, J.W.; Bansal, A.K.; Burn, P.L.; Lo, S.-C.; Samuel, I.D.W.

    2012-01-01

    Phosphorescent poly(dendrimers) with a norbornene-derived backbone have been synthesized using ring-opening metathesis polymerization with the Grubbs III catalyst. The dendrimers are comprised of a heteroleptic iridium(III) complex core with two 2-phenylpyridyl ligands and a phenyltriazolyl ligand,

  12. Towards HIV detection: Novel Poly(propylene imine) Dendrimer-Streptavidin platform for electrochemical DNA and gp120 aptamer biosensors

    CSIR Research Space (South Africa)

    John, SV

    2014-07-01

    Full Text Available The detection of sequence – specific DNA and HIV glycoprotein 120 (gp120) based on novel generation 4 poly(propylene imine) dendrimer/streptavidin platform is reported. The platform was prepared by the electrodeposition of the dendrimer on a carbon...

  13. Zn (II and Cu (II Halide Complexes of Poly(propylene amine Dendrimer Analysed by Infrared and Raman Spectroscopies

    Directory of Open Access Journals (Sweden)

    Ivo Grabchev

    2013-01-01

    Full Text Available Two nondestructive and complementary spectral methods as infrared and Raman spectroscopies have been used for characterizations of poly(propylene amine dendrimers comprising 1,8-naphthalimide units in the dendrimer periphery and their metal complexes with Cu2+ at Zn2+ ions.

  14. Charge-dependent conformations and dynamics of pamam dendrimers revealed by neutron scattering and molecular dynamics

    Science.gov (United States)

    Wu, Bin

    Neutron scattering and fully atomistic molecular dynamics (MD) are employed to investigate the structural and dynamical properties of polyamidoamine (PAMAM) dendrimers with ethylenediamine (EDA) core under various charge conditions. Regarding to the conformational characteristics, we focus on scrutinizing density profile evolution of PAMAM dendrimers as the molecular charge of dendrimer increases from neutral state to highly charged condition. It should be noted that within the context of small angle neutron scattering (SANS), the dendrimers are composed of hydrocarbon component (dry part) and the penetrating water molecules. Though there have been SANS experiments that studied the charge-dependent structural change of PAMAM dendrimers, their results were limited to the collective behavior of the aforementioned two parts. This study is devoted to deepen the understanding towards the structural responsiveness of intra-molecular polymeric and hydration parts separately through advanced contrast variation SANS data analysis scheme available recently and unravel the governing principles through coupling with MD simulations. Two kinds of acids, namely hydrochloric and sulfuric acids, are utilized to tune the pH condition and hence the molecular charge. As far as the dynamical properties, we target at understanding the underlying mechanism that leads to segmental dynamic enhancement observed from quasielstic neutron scattering (QENS) experiment previously. PAMAM dendrimers have a wealth of potential applications, such as drug delivery agency, energy harvesting medium, and light emitting diodes. More importantly, it is regarded as an ideal system to test many theoretical predictions since dendrimers conjugate both colloid-like globular shape and polymer-like flexible chains. This Ph.D. research addresses two main challenges in studying PAMAM dendrimers. Even though neutron scattering is an ideal tool to study this PAMAM dendrimer solution due to its matching temporal and

  15. Redox-controlled interaction of biferrocenyl-terminated dendrimers with beta-cyclodextrin molecular printboards.

    Science.gov (United States)

    Nijhuis, Christian A; Dolatowska, Karolina A; Ravoo, Bart Jan; Huskens, Jurriaan; Reinhoudt, David N

    2007-01-01

    This paper describes the synthesis and electrochemistry of biferrocenyl-terminated dendrimers and their beta-cyclodextrin (beta-CD) inclusion complexes in aqueous solution and at surfaces. Three generations of poly(propylene imine) (PPI) dendrimers, decorated with 4, 8, and 16 biferrocenyl (BFc) units, respectively, were synthesized. A water-soluble BFc derivative forms stable inclusion complexes with beta-CD. The intrinsic binding constant is K(i)=2.5 x 10(4) M(-1). The BFc dendrimers were solubilized in water by complexation of the end groups with beta-CD, resulting in large water-soluble supramolecular assemblies. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) showed that all the end groups are complexed to beta-CD. Adsorption of the dendrimers at self-assembled monolayers (SAMs) of heptathioether-functionalized beta-CD on gold ("molecular printboards") resulted in stable monolayers of the dendrimers due to the formation of multivalent host-guest interactions between the BFc end groups of the dendrimers and the immobilized beta-CD molecules. The number of interacting end groups is 3, 4, and 4 for dendrimer generations 1, 2, and 3, respectively. The complexation of BFc to beta-CD is sensitive to the oxidation state of the BFc unit. Oxidation of neutral BFc-Fe(2) ((II,II)) to the cationic, mixed-valence biferrocenium BFc-Fe(2) ((II,III)+) resulted in dissociation of the host-guest complexes. Scan-rate-dependent CV and DPV analyses of the dendrimer-beta-CD assemblies immobilized at the beta-CD host surface and in solution revealed that the dendrimers are oxidized in three steps. First, the surface-beta-CD-bound BFc moieties are oxidized to the mixed-valence state, Fe(2) ((II,III)+), followed by the oxidation of the non-surface-interacting BFc groups to the Fe(2) ((II,III)+) state. The third step involves the oxidation of all the BFc moieties to the Fe(2) ((III,III)2+) state.

  16. A multiscale scheme for the simulation of conformational and solution properties of different dendrimer molecules.

    Science.gov (United States)

    Del Río Echenique, Gustavo; Rodríguez Schmidt, Ricardo; Freire, Juan J; Hernández Cifre, José G; García de la Torre, José

    2009-06-24

    We propose a multiscale protocol for the simulation of conformation and dynamics of dendrimer molecules in dilute solution. Conformational properties (radius of gyration, mass distribution, and scattering intensities) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) are predicted by means of a very simple coarse-grained bead-and-spring model, whose parameters are not adjusted against experimental properties, but rather they are obtained from previous, atomic-level simulations which are also quite simple, performed with small fragments and Langevin dynamics simulation. The scheme is described and applied systematically to four different dendrimer molecules with up to seven generations. The predictive capability of this scheme is tested by comparison with experimental data. It is found that the predicted geometric and hydrodynamic radii of the dendrimer molecules are in agreement (typical error is about 4%) with a large set experimental values of the four dendrimers with various numbers of generations. Agreement with some X-ray scattering experimental intensities also confirms the good prediction of the internal structure. This scheme is easily extendable to study more complex molecules (e.g., functionalized dendrimers) and to simulate internal dynamics.

  17. Biomimetics: From Bioinformatics to Rational Design of Dendrimers as Gene Carriers

    Science.gov (United States)

    Araya-Durán, Ingrid; Varas-Concha, Ignacio; Almonacid, Daniel Eduardo; González-Nilo, Fernando Danilo

    2015-01-01

    Biomimetics, or the use of principles of Nature for developing new materials, is a paradigm that could help Nanomedicine tremendously. One of the current challenges in Nanomedicine is the rational design of new efficient and safer gene carriers. Poly(amidoamine) (PAMAM) dendrimers are a well-known class of nanoparticles, extensively used as non-viral nucleic acid carriers, due to their positively charged end-groups. Yet, there are still several aspects that can be improved for their successful application in in vitro and in vivo systems, including their affinity for nucleic acids as well as lowering their cytotoxicity. In the search of new functional groups that could be used as new dendrimer-reactive groups, we followed a biomimetic approach to determine the amino acids with highest prevalence in protein-DNA interactions. Then we introduced them individually as terminal groups of dendrimers, generating a new class of nanoparticles. Molecular dynamics studies of two systems: PAMAM-Arg and PAMAM-Lys were also performed in order to describe the formation of complexes with DNA. Results confirmed that the introduction of amino acids as terminal groups in a dendrimer increases their affinity for DNA and the interactions in the complexes were characterized at atomic level. We end up by briefly discussing additional modifications that can be made to PAMAM dendrimers to turned them into promising new gene carriers. PMID:26382062

  18. In vivo toxicity evaluation of gold-dendrimer composite nanodevices with different surface charges.

    Science.gov (United States)

    Kasturirangan, Venugopalan; Nair, Bindu M; Kariapper, Muhammed T S; Lesniak, Wojciech G; Tan, Wei; Bizimungu, Remy; Kanter, Peter; Toth, Karoly; Buitrago, Sandra; Rustum, Youcef M; Hutson, Alan; Balogh, Lajos P; Khan, Mohamed K

    2013-06-01

    Composite nanodevices (CNDs) are multifunctional nanomaterials with potential uses in cancer imaging and therapy. Poly(amidoamine) dendrimer-based composite nanodevices are important members of this group and consist of an organic dendrimer component and an incorporated inorganic component, in this case, gold. This study addresses the short- (14 days) and long-term (78 days) in vivo toxicity of generation-5 (G5; 5 nm) PAMAM dendrimer-based gold-CNDs (Au-CNDs) with varying surface charges (positive, negative and neutral) in C57BL/6J male mice. Detailed toxicological analyses of (1) body weight changes, (2) serum chemistry and (3) histopathological examination of 22 organs showed no evidence of organ injury or organ function compromise. Zeta potential of Au-CNDs showed significant change from their parent dendrimers upon gold incorporation, making the normally lethal positive surface dendrimer biologically safe. Also homeostatic mechanisms in vivo may compensate/repair toxic effects, something not seen with in vitro assays.

  19. Biomimetics: From Bioinformatics to Rational Design of Dendrimers as Gene Carriers.

    Directory of Open Access Journals (Sweden)

    Valeria Márquez-Miranda

    Full Text Available Biomimetics, or the use of principles of Nature for developing new materials, is a paradigm that could help Nanomedicine tremendously. One of the current challenges in Nanomedicine is the rational design of new efficient and safer gene carriers. Poly(amidoamine (PAMAM dendrimers are a well-known class of nanoparticles, extensively used as non-viral nucleic acid carriers, due to their positively charged end-groups. Yet, there are still several aspects that can be improved for their successful application in in vitro and in vivo systems, including their affinity for nucleic acids as well as lowering their cytotoxicity. In the search of new functional groups that could be used as new dendrimer-reactive groups, we followed a biomimetic approach to determine the amino acids with highest prevalence in protein-DNA interactions. Then we introduced them individually as terminal groups of dendrimers, generating a new class of nanoparticles. Molecular dynamics studies of two systems: PAMAM-Arg and PAMAM-Lys were also performed in order to describe the formation of complexes with DNA. Results confirmed that the introduction of amino acids as terminal groups in a dendrimer increases their affinity for DNA and the interactions in the complexes were characterized at atomic level. We end up by briefly discussing additional modifications that can be made to PAMAM dendrimers to turned them into promising new gene carriers.

  20. Role of PAMAM-OH dendrimers against the fibrillation pathway of biomolecules.

    Science.gov (United States)

    Sekar, Gajalakshmi; Florance, Ida; Sivakumar, A; Mukherjee, Amitava; Chandrasekaran, Natarajan

    2016-12-01

    The binding behavior of nanoparticle with proteins determines its biocompatibility. This study reports the interaction of ten different biomolecules (proteins-BSA, HSA, haemoglobin, gamma globulin, transferrin and enzymes-hog and bacillus amylase, lysozyme from chicken and human and laccases from Tramates versicolor) with a surface group hydroxylated Poly AMido AMide dendrimer (PAMAM) of generation 5. The study has utilized various spectroscopic methods like UV-vis spectroscopy, Fluorescence emission, Synchronous, 3-D spectroscopy and Circular Dichroism to detect the binding induced structural changes in biomolecules that occur upon interaction with mounting concentration of the dendrimers. Aggregation of proteins results in the formation of amyloid fibrils causing several human diseases. In this study, fibrillar samples of all ten biomolecules formed in the absence and the presence of dendrimers were investigated with Congo Red absorbance and ThT Assay to detect fibril formation, Trp Emission and 3-D scan to evaluate the effect of fibrillation on aromatic environment of biomolecules, and CD spectroscopy to measure the conformational changes in a quantitative manner. These assays have generated useful information on the role of dendrimers in amyloid fibril formation of biomolecules. The outcomes of the study remain valuable in evaluating the biological safety of PAMAM-OH dendrimers for their biomedical application in vivo.

  1. Aggregation-controlled excimer emission from anthracene-containing polyamidoamine dendrimers.

    Science.gov (United States)

    Lekha, P K; Prasad, Edamana

    2010-03-22

    Lower generations of polyamidoamine (PAMAM) dendrimers were peripherally modified with anthracene moieties, and excimer emission from anthracene chromophores was investigated in an acetonitrile-water mixture at acidic and basic pH values. Results from fluorescence spectroscopic experiments suggest that 1) the propensity of anthracene-modified PAMAM dendrimers to aggregate in acetonitrile is substantial in the presence of 15-20 vol % of water, and 2) aggregate formation in anthracene-modified PAMAM dendrimers leads to unique morphologies in the ground state, where the anthracene units are pre-arranged to form stable excimers upon photoexcitation. Three types of anthracene excimers are generated in the system, with face-to-face, angular, and T-shaped geometry. The formation of different types of anthracene excimers was confirmed by steady-state and time-resolved fluorescence spectroscopic experiments. Experimental results further suggest that it is feasible to alter the type of excimer formed by anthracene units attached to the PAMAM dendrimers through altering the propensity for ground-state aggregation. Most excitingly, increased pi conjugation in the molecular framework of anthracene-substituted PAMAM dendrimers leads to intense and exclusive excimer emission from anthracene at room temperature.

  2. Experimental and theoretical investigations in stimuli responsive dendrimer-based assemblies

    Science.gov (United States)

    Molla, Mijanur Rahaman; Rangadurai, Poornima; Pavan, Giovanni M.; Thayumanavan, S.

    2015-02-01

    Stimuli-responsive macromolecular assemblies are of great interest in drug delivery applications, as it holds the promise to keep the drug molecules sequestered under one set of conditions and release them under another. The former set of conditions could represent circulation, while the latter could represent a disease location. Over the past two decades, sizeable contributions to this field have come from dendrimers, which along with their monodispersity, provide great scope for structural modifications at the molecular level. In this paper, we briefly discuss the various synthetic strategies that have been developed so far to obtain a range of functional dendrimers. We then discuss the design strategies utilized to introduce stimuli responsive elements within the dendritic architecture. The stimuli itself are broadly classified into two categories, viz. extrinsic and intrinsic. Extrinsic stimuli are externally induced such as temperature and light variations, while intrinsic stimuli involve physiological aberrations such as variations in pH, redox conditions, proteins and enzyme concentrations in pathological tissues. Furthermore, the unique support from molecular dynamics (MD) simulations has been highlighted. MD simulations have helped back many of the observations made from assembly formation properties to rationalized the mechanism of drug release and this has been illustrated with discussions on G4 PPI (Poly propylene imine) dendrimers and biaryl facially amphiphilic dendrimers. The synergy that exists between experimental and theoretical studies open new avenues for the use of dendrimers as versatile drug delivery systems.

  3. Modulation of biogenic amines content by poly(propylene imine) dendrimers in rats.

    Science.gov (United States)

    Ciepluch, Karol; Ziemba, Barbara; Janaszewska, Anna; Appelhans, Dietmar; Klajnert, Barbara; Bryszewska, Maria; Fogel, Wiesława Agnieszka

    2012-09-01

    Biogenic amines and polyamines participate in all vital organism functions, their levels being important function determinants. Studies were performed to check whether repeated administration of poly(propylene imine) (PPI) dendrimers, synthetic macromolecules with diaminobutane core, and peripheral primary amine groups, may influence the endogenous level of amines, as represented by the two of them: spermidine, a natural derivative of diaminobutane, and histamine. The experiment was carried out on Wistar rats. Fourth generation PPI dendrimer, as well as maltotriose-modified fourth generation PPI dendrimers with (a) cationic open sugar shell and (b) neutral dense sugar shell that possess a higher biocompatibility, was used. Applying the combination of column chromatography on Cellex P and spectrofluorimetric assays of o-phthaldialdehyde, the final amine condensation products were employed to analyze tissue spermidine and histamine outside the central nervous system. Furthermore, radioenzymatic assay was used to measure histamine levels in the brain. The obtained results indicate that in some tissues, the endogenous concentrations of histamine and spermidine may be affected by dendrimers depending on their dose and type of dendrimers.

  4. Facile and Efficient Synthesis of Carbosiloxane Dendrimers via Orthogonal Click Chemistry Between Thiol and Ene.

    Science.gov (United States)

    Zhang, Zhida; Feng, Shengyu; Zhang, Jie

    2016-02-01

    A combination of a thiol-Michael addition reaction and a free radical mediated thiol-ene reaction is employed as a facile and efficient approach to carbosiloxane dendrimer synthesis. For the first time, carbosiloxane dendrimers are constructed rapidly by an orthogonal click strategy without protection/deprotection procedures. The chemoselectivity of these two thiol-ene click reactions leads to a design of a new monomer containing both electron-deficient carbon-carbon double bonds and unconjugated carbon-carbon double bonds. Siloxane bonds are introduced as the linker between these two kinds of carbon-carbon double bonds. Starting from a bifunctional thiol core, the dendrimers are constructed by iterative thiol-ene click reactions under different but both mild reaction conditions. After simple purification steps the fifth dendrimer with 54 peripheral functional groups is obtained with an excellent overall yield in a single day. Furthermore, a strong blue glow is observed when the dendrimer is excited by a UV lamp.

  5. Intermolecular forces between low generation PAMAM dendrimer condensed DNA helices: role of cation architecture.

    Science.gov (United States)

    An, Min; Parkin, Sean R; DeRouchey, Jason E

    2014-01-28

    In recent years, dendriplexes, complexes of cationic dendrimers with DNA, have become attractive DNA delivery vehicles due to their well-defined chemistries. To better understand the nature of the forces condensing dendriplexes, we studied low generation poly(amidoamine) (PAMAM) dendrimer-DNA complexes and compared them to comparably charged linear arginine peptides. Using osmotic stress coupled with X-ray scattering, we have investigated the effect of molecular chain architecture on DNA-DNA intermolecular forces that determine the net attraction and equilibrium interhelical distance within these polycation condensed DNA arrays. In order to compact DNA, linear cations are believed to bind in DNA grooves and to interact with the phosphate backbone of apposing helices. We have previously shown a length dependent attraction resulting in higher packaging densities with increasing charge for linear cations. Hyperbranched polycations, such as polycationic dendrimers, presumably would not be able to bind to DNA and correlate their charges in the same manner as linear cations. We show that attractive and repulsive force amplitudes in PAMAM-DNA assemblies display significantly different trends than comparably charged linear arginines resulting in lower DNA packaging densities with increasing PAMAM generation. The salt and pH dependencies of packaging in PAMAM dendrimer-DNA and linear arginine-DNA complexes were also investigated. Significant differences in the force curve behaviour and salt and pH sensitivities suggest that different binding modes may be present in DNA condensed by dendrimers when compared to linear polycations.

  6. Physicochemical and biological properties of self-assembled antisense/poly(amidoamine dendrimer nanoparticles: the effect of dendrimer generation and charge ratio

    Directory of Open Access Journals (Sweden)

    Alireza Nomani

    2010-05-01

    Full Text Available Alireza Nomani1,6, Ismaeil Haririan1,5, Ramin Rahimnia2,4, Shamileh Fouladdel2, Tarane Gazori1, Rassoul Dinarvand1, Yadollah Omidi3, Ebrahim Azizi2,41Department of Pharmaceutics, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran; 2Molecular Research Lab, Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran; 3Department of Pharmaceutics, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran; 4Department of Medical Biotechnology, School of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran, Iran; 5Biomaterials Research Center (BRC Tehran, Iran; 6Department of Pharmaceutics, Faculty of Pharmacy, Zanjan University of Medical Sciences, Zanjan, IranAbstract: To gain a deeper understanding of the physicochemical phenomenon of self-assembled nanoparticles of different generations and ratios of poly (amidoamine dendrimer (PAMAM dendrimer and a short-stranded DNA (antisense oligonucleotide, multiple methods were used to characterize these nanoparticles including photon correlation spectroscopy (PCS; zeta potential measurement; and atomic force microscopy (AFM. PCS and AFM results revealed that, in contrast to larger molecules of DNA, smaller molecules produce more heterodisperse and large nanoparticles when they are condensed with a cationic dendrimer. AFM images also showed that such nanoparticles were spherical. The stability of the antisense content of the nanoparticles was investigated over different charge ratios using polyacrylamide gel electrophoresis. It was clear from such analyses that much more than charge neutrality point was required to obtain stable nanoparticles. For cell uptake, self-assembled nanoparticles were prepared with PAMAM G5 and 5’-FITC labeled antisense and the uptake experiment was carried out in T47D cell culture. This investigation also shows that the cytotoxicity of the nanoparticles was

  7. Polymer stabilized Ni-Ag and Ni-Fe alloy nanoclusters: Structural and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kabir, L.; Mandal, A.R. [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India); Mandal, S.K., E-mail: sk_mandal@hotmail.co [Department of Physics, Visva-Bharati, Santiniketan-731 235 (India)

    2010-04-15

    We report here the structural and magnetic behaviors of nickel-silver (Ni-Ag) and nickel-iron (Ni-Fe) nanoclusters stabilized with polymer (polypyrrole). High resolution transmission electron microscopy (HRTEM) indicates Ni-Ag nanoclusters to stabilize in core-shell configuration while that of Ni-Fe nanoclusters in a mixed type of geometry. Structural characterizations by X-ray diffraction (XRD) reveal the possibility of alloying in such bimetallic nanoclusters to some extent even at temperatures much lower than that of bulk alloying. Electron paramagnetic resonance (EPR) spectra clearly reveal two different absorption behaviors: one is ascribed to non-isolated Ni{sup 2+} clusters surrounded by either silver or iron giving rise to a broad signal, other (very narrow signal) being due to the isolated superparamagnetic Ni{sup 2+} clusters or bimetallic alloy nanoclusters. Results obtained for Ni-Ag and Ni-Fe nanoclusters have been further compared with the behavior exhibited by pure Ni nanoclusters in polypyrrole host. Temperature dependent studies (at 300 and 77 K) of EPR parameters, e.g. linewidth, g-value, line shape and signal intensity indicating the significant influence of surrounding paramagnetic silver or ferromagnetic iron within polymer host on the EPR spectra have been presented.

  8. Importance of configurational contributions to the free energy of nanoclusters

    Directory of Open Access Journals (Sweden)

    M. Posselt

    2013-07-01

    Full Text Available An effective simulation method based on the Wang-Landau Monte Carlo algorithm is used in order to demonstrate the significance of the configurational contributions to the free energy of embedded nanoclusters. Starting from the most stable cluster configuration the simulation provides all geometrically different, but simply connected and sufficiently compact configurations of a nanocluster of a given size and the respective formation energies. The knowledge of these data allows the calculation of the free formation and free binding energy of the cluster at T ≠ 0. The method is applied to coherent Cu clusters in bcc-Fe. It is shown that even at moderate temperatures the configurational contributions to the free formation and binding energy must not be neglected. The dependence of the monomer free binding energy on clusters size is found to change significantly with increasing temperature which has a considerable effect on the pathway of cluster evolution. Therefore, present investigations provide an essential contribution to the improvement of the input parameters for object kinetic Monte Carlo simulations and rate theory used in multi-scale simulations of the nanostructure evolution. The calculation scheme developed in this work is rather general and applicable to many types of embedded nanoclusters. Compared to the method of overlapping distributions hitherto used in some cases to determine the configurational part of the free energy the new method has major advantages. Various tests are performed in order verify the presented approach and to compare with the results of the other calculation procedure. A roadmap is proposed to include the vibrational contributions to the free energy of the clusters within the framework of the method employed in this work.

  9. Organization of copper nanoclusters in Langmuir–Blodgett films

    Indian Academy of Sciences (India)

    G Hemakanthi; Aruna Dhathathreyan; T Ramasami

    2002-02-01

    Stable nanoclusters of Cu were synthesized using Langmuir–Blodgett films of octadecylsuccinic acid (ODSA) as template. The Langmuir–Blodgett films of ODSA formed from subphase containing copper ions were first subjected to sulphidation (S) using sodium sulphide and then hydrogenated (H) using hydrogen gas. Diffuse reflectance UV-visible spectroscopy (DIR-UV-vis), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) used to characterize these films indicated the formation of Cu(0) metallic clusters ranging in size from 3 ∼ 10 nm.

  10. Enantioselective silver nanoclusters: Preparation, characterization and photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farrag, Mostafa, E-mail: mostafafarrag@aun.edu.eg

    2016-09-01

    Herein, we report a new wet-synthesis method to separate some water-soluble chiral silver nanoclusters with high yield. The cluster material was obtained by the reduction of silver nitrate with NaBH{sub 4} in the presence of three ligands L-penicillamine (L-pen), D-penicillamine (D-pen) and racemic mixture of penicillamine (rac-pen), functioning as capping ligand. For characterizing all silver cluster samples, the particle size was assessed by transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) and their average chemical formula was determined from thermogravimetric analysis (TGA) and elemental analysis (EA). The particles sizes of all three clusters are 2.1 ± 0.2 nm. The optical properties of the samples were studied by four different methods: UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and circular dichroism (CD) spectroscopy. The spectra are dominated by the typical and intense plasmon peak at 486 nm accompanied by a small shoulder at 540 nm. Infrared spectroscopy was measured for the free ligand and protected silver nanoclusters, where the disappearance of the S-H vibrational band (2535–2570 cm{sup −1}) in the silver nanoclusters confirmed anchoring of ligand to the cluster surface through the sulfur atom. PL studies yielded the fluorescent properties of the samples. The main focus of this work, however, lies in the chirality of the particles. For all silver clusters CD spectra were recorded. While for clusters capped with one of the two enantiomers (D- or L-form) typical CD spectra were observed, no significant signals were detected for a racemic ligand mixture. Furthermore, silver clusters show quite large asymmetry factors (up to 3 × 10{sup −4}) in comparison to most other ligand protected clusters. These large factors and bands in the visible range of the spectrum suggest a strong chiral induction from the ligand to the metal core. Textural features of the

  11. Fabrication of metal nanoclusters on graphene grown on Ru(0001)

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hui; FU Qiang; CUI Yi; TAN DaLi; BAO XinHe

    2009-01-01

    Monolayer graphene was epitaxially grown on Ru(0001) through exposure of the Ru(0001) to ethylene at room temperature followed by annealing in ultrahigh vacuum at elevated temperatures. The resulting graphene structures were studied by scanning tunneling microscopy (STM), X-ray photoelectron spec-troscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). The graphene/Ru(0001) surface was used as a periodic template for growth of metal nanoclusters. Highly dispersed Pt clusters with well controlled size and spatial distribution were fabricated on the surface.

  12. Dynamic study on the transformation process of gold nanoclusters.

    Science.gov (United States)

    Ma, Xiaoqian; Wen, Xiaoming; Toh, Yon-Rui; Huang, Kuo-Yen; Tang, Jau; Yu, Pyng

    2014-11-01

    In this paper, the transformation process from Au8 to Au25 nanoclusters (NCs) is investigated with steady state fluorescence spectroscopy and time-resolved fluorescence spectroscopy at various reaction temperatures and solvent diffusivities. Results demonstrate that Au8 NCs, protected by bovine serum albumin, transform into Au25 NCs under controlled pH values through an endothermic reaction with the activation energy of 74 kJ mol(-1). Meanwhile, the characteristic s-shaped curves describing the formation of Au25 NCs suggest this process involves a diffusion controlled growth mechanism.

  13. Synthesis and characterization of human transferrin-stabilized gold nanoclusters

    Science.gov (United States)

    Le Guével, Xavier; Daum, Nicole; Schneider, Marc

    2011-07-01

    Human transferrin has been biolabelled with gold nanoclusters (Au NCs) using a simple, fast and non-toxic method. These nanocrystals (polyclonal antibody. Additionally, antibody-induced agglomeration demonstrates no alteration in the protein activity and the receptor target ability. MTT and Vialight® Plus tests show no cytotoxicity of these labelled proteins in cells (1 µg ml - 1-1 mg ml - 1). Cell line experiments (A549) indicate also an uptake of the iron loaded fluorescent proteins inside cells. These remarkable data highlight the potential of a new type of non-toxic fluorescent transferrin for imaging and targeting.

  14. Reversible modulation of gold nanoclusters photoluminescence based on electrochromic poly(methylene blue).

    Science.gov (United States)

    Zhang, Hui; Zhai, Yanling; Dong, Shaojun

    2014-11-01

    Reversible photoluminescence (PL) switches based on a complex of gold nanoclusters and electrochromic poly(methylene blue) (PMB) were realized. The gold nanoclusters PL of hybrid device can be modulated reversibly under electrochemical stimulation. Such an electrochromic device presents several advantages, such as large fluorescence contrast under reduction and oxidation potentials, good reversibility and excellent long-time stability. This simple protocol is anticipated to offer important hints for other nanoclusters and electrochromic materials in the field of photoelectric devices. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Protein mediated synthesis of fluorescent Au-nanoclusters for metal sensory coatings

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Manja; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biogeochemistry

    2017-06-01

    Fluorescent Au-nanocluster were successfully synthesized and used for the selective detection of Cu{sup 2} {sup +}. The synthesized Au-BSA-nanoclusters remain functional also after immobilization and show high thermal stability. Additionally, the transfer of the protein mediated Au-nanocluster synthesis route to S-layer proteins was achieved. (The presented work is part of the project BIONEWS dealing with long-term stable cells for the set-up and regeneration of sensor and actor materials for strategic relevant metals, in particular rare earth elements).

  16. Size-dependent mobility of gold nano-clusters during growth on chemically modified graphene

    Energy Technology Data Exchange (ETDEWEB)

    Bell, Gavin R., E-mail: gavin.bell@warwick.ac.uk; Dawson, Peter M.; Pandey, Priyanka A.; Wilson, Neil R. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Mulheran, Paul A. [Department of Chemical and Process Engineering, University of Strathclyde, James Weir Building, 75 Montrose St., Glasgow G1 1XJ (United Kingdom)

    2014-01-01

    Gold nano-clusters were grown on chemically modified graphene by direct sputter deposition. Transmission electron microscopy of the nano-clusters on these electron-transparent substrates reveals an unusual bimodal island size distribution (ISD). A kinetic Monte Carlo model of growth incorporating a size-dependent cluster mobility rule uniquely reproduces the bimodal ISD, providing strong evidence for the mobility of large clusters during surface growth. The cluster mobility exponent of −5/3 is consistent with cluster motion via one-dimensional diffusion of gold atoms around the edges of the nano-clusters.

  17. Size-dependent mobility of gold nano-clusters during growth on chemically modified graphene

    Directory of Open Access Journals (Sweden)

    Gavin R. Bell

    2014-01-01

    Full Text Available Gold nano-clusters were grown on chemically modified graphene by direct sputter deposition. Transmission electron microscopy of the nano-clusters on these electron-transparent substrates reveals an unusual bimodal island size distribution (ISD. A kinetic Monte Carlo model of growth incorporating a size-dependent cluster mobility rule uniquely reproduces the bimodal ISD, providing strong evidence for the mobility of large clusters during surface growth. The cluster mobility exponent of −5/3 is consistent with cluster motion via one-dimensional diffusion of gold atoms around the edges of the nano-clusters.

  18. Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application

    Science.gov (United States)

    Chen, Yongdong; Wang, Jin; Liu, Chao; Li, Zhimin; Li, Gao

    2016-05-01

    We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S(&z.dbd;O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent

  19. Characterization and evaluation of amphotericin B loaded MDP conjugated poly(propylene imine) dendrimers.

    Science.gov (United States)

    Jain, Keerti; Verma, Ashwni Kumar; Mishra, Prabhat Ranjan; Jain, Narendra Kumar

    2015-04-01

    This paper describes a novel strategy for targeted delivery of amphotericin B (AmB) to macrophages with muramyl dipeptide (MDP) conjugated multimeric poly(propyleneimine) (PPI) dendrimers. Synergistic antiparasitic activity due to immunostimulation by multimeric presentation of MDP on dendrimers was anticipated. MDP conjugated 5.0G PPI (MdPPI) dendrimers were synthesized and characterized. Therapeutic activity and toxicity of dendrimeric formulation of AmB (MdPPIA) were compared with marketed formulations of AmB. Highly significant (PMDP conjugated dendrimeric formulation of AmB as a promising immunostimulant targeted drug delivery system and a safer alternative to marketed formulations. From the clinical editor: Parasitic infections remain a significant issue in the clinical setting. The authors in this article studied the use of ligand anchored dendrimeric formulation of Amphotericin B to target infected macrophages and showed reduced toxicity, high anti-leishmanial activity. This may add another treatment option to available formulations in the future.

  20. The key role of the scaffold on the efficiency of dendrimer nanodrugs.

    Science.gov (United States)

    Caminade, Anne-Marie; Fruchon, Séverine; Turrin, Cédric-Olivier; Poupot, Mary; Ouali, Armelle; Maraval, Alexandrine; Garzoni, Matteo; Maly, Marek; Furer, Victor; Kovalenko, Valeri; Majoral, Jean-Pierre; Pavan, Giovanni M; Poupot, Rémy

    2015-07-14

    Dendrimers are well-defined macromolecules whose highly branched structure is reminiscent of many natural structures, such as trees, dendritic cells, neurons or the networks of kidneys and lungs. Nature has privileged such branched structures for increasing the efficiency of exchanges with the external medium; thus, the whole structure is of pivotal importance for these natural networks. On the contrary, it is generally believed that the properties of dendrimers are essentially related to their terminal groups, and that the internal structure plays the minor role of an 'innocent' scaffold. Here we show that such an assertion is misleading, using convergent information from biological data (human monocytes activation) and all-atom molecular dynamics simulations on seven families of dendrimers (13 compounds) that we have synthesized, possessing identical terminal groups, but different internal structures. This work demonstrates that the scaffold of nanodrugs strongly influences their properties, somewhat reminiscent of the backbone of proteins.

  1. Facile synthesis of polyester dendrimers from sequential click coupling of asymmetrical monomers.

    Science.gov (United States)

    Ma, Xinpeng; Tang, Jianbin; Shen, Youqing; Fan, Maohong; Tang, Huadong; Radosz, Maciej

    2009-10-21

    Polyester dendrimers are attractive for in vivo delivery of bioactive molecules due to their biodegradability, but their synthesis generally requires multistep reactions with intensive purifications. A highly efficient approach to the synthesis of dendrimers by simply "sticking" generation by generation together is achieved by combining kinetic or mechanistic chemoselectivity with click reactions between the monomers. In each generation, the targeted molecules are the major reaction product as detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The only separation needed is to remove the little unreacted monomer by simple precipitation or washing. This simple clicklike process without complicated purification is particularly suitable for the synthesis of custom-made polyester dendrimers.

  2. HER2 specific delivery of methotrexate by dendrimer conjugated anti-HER2 mAb

    Energy Technology Data Exchange (ETDEWEB)

    Shukla, Rameshwer; Thomas, Thommey P; Desai, Ankur M; Kotlyar, Alina; Park, Steve J; Baker, James R Jr [Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, 9220 MSRB III, Box 0648, Ann Arbor, MI 48109 (United States)], E-mail: rameshwe@umich.edu, E-mail: jbakerjr@med.umich.edu

    2008-07-23

    Herceptin, a humanized monoclonal antibody that binds to human growth factor receptor-2 (HER2), was covalently attached to a fifth-generation (G5) polyamidoamine dendrimer containing the cytotoxic drug methotrexate. The specific binding and internalization of this conjugate labeled with FITC was clearly demonstrated in cell lines overexpressing HER2 by flow cytometry as well as confocal microscopic analysis. In addition, binding and uptake of antibody conjugated dendrimers was completely blocked by excess non-conjugated herceptin. The dendrimer conjugate was also shown to inhibit the dihydrofolate reductase with similar activity to methotrexate. Co-localization experiments with lysotracker red indicate that antibody conjugate, although internalized efficiently into cells, has an unusually long residence time in the lysosome. Somewhat lower cytotoxicity of the conjugate in comparison to free methotrexate was attributed to the slow release of methotrexate from the conjugate and its long retention in the lysosomal pocket.

  3. Dendrimers and Dendrons as Versatile Building Blocks for the Fabrication of Functional Hydrogels

    Directory of Open Access Journals (Sweden)

    Sadik Kaga

    2016-04-01

    Full Text Available Hydrogels have emerged as a versatile class of polymeric materials with a wide range of applications in biomedical sciences. The judicious choice of hydrogel precursors allows one to introduce the necessary attributes to these materials that dictate their performance towards intended applications. Traditionally, hydrogels were fabricated using either polymerization of monomers or through crosslinking of polymers. In recent years, dendrimers and dendrons have been employed as well-defined building blocks in these materials. The multivalent and multifunctional nature of dendritic constructs offers advantages in either formulation or the physical and chemical properties of the obtained hydrogels. This review highlights various approaches utilized for the fabrication of hydrogels using well-defined dendrimers, dendrons and their polymeric conjugates. Examples from recent literature are chosen to illustrate the wide variety of hydrogels that have been designed using dendrimer- and dendron-based building blocks for applications, such as sensing, drug delivery and tissue engineering.

  4. Targeting of follicle stimulating hormone peptide-conjugated dendrimers to ovarian cancer cells

    Science.gov (United States)

    Modi, Dimple A.; Sunoqrot, Suhair; Bugno, Jason; Lantvit, Daniel D.; Hong, Seungpyo; Burdette, Joanna E.

    2014-02-01

    Ovarian cancer is the most lethal gynecological malignancy. Current treatment modalities include a combination of surgery and chemotherapy, which often lead to loss of fertility in premenopausal women and a myriad of systemic side effects. To address these issues, we have designed poly(amidoamine) (PAMAM) dendrimers to selectively target the follicle stimulating hormone receptor (FSHR), which is overexpressed by tumorigenic ovarian cancer cells but not by immature primordial follicles and other non-tumorigenic cells. Fluorescein-labeled generation 5 (G5) PAMAM dendrimers were conjugated with the binding peptide domain of FSH (FSH33) that has a high affinity to FSHR. The targeted dendrimers exhibited high receptor selectivity to FSHR-expressing OVCAR-3 cells, resulting in significant uptake and downregulation of an anti-apoptotic protein survivin, while showing minimal interactions with SKOV-3 cells that do not express FSHR. The selectivity of the FSH33-targeted dendrimers was further validated in 3D organ cultures of normal mouse ovaries. Immunostaining of the conjugates revealed their selective binding and uptake by ovarian surface epithelium (OSE) cells that express FSHR, while sparing the immature primordial follicles. In addition, an in vivo study monitoring tissue accumulation following a single intraperitoneal (i.p.) injection of the conjugates showed significantly higher accumulation of FSH33-targeted dendrimers in the ovary and oviduct compared to the non-targeted conjugates. These proof-of-concept findings highlight the potential of these FSH33-targeted dendrimers to serve as a delivery platform for anti-ovarian cancer drugs, while reducing their systemic side effects by preventing nonspecific uptake by the primordial follicles.Ovarian cancer is the most lethal gynecological malignancy. Current treatment modalities include a combination of surgery and chemotherapy, which often lead to loss of fertility in premenopausal women and a myriad of systemic side

  5. Fluorescent hydroxylamine derived from the fragmentation of PAMAM dendrimers for intracellular hypochlorite recognition.

    Science.gov (United States)

    Wu, Te-Haw; Liu, Ching-Ping; Chien, Chih-Te; Lin, Shu-Yi

    2013-08-26

    Herein, a promising sensing approach based on the structure fragmentation of poly(amidoamine) (PAMAM) dendrimers for the selective detection of intracellular hypochlorite (OCl(-)) is reported. PAMAM dendrimers were easily disrupted by a cascade of oxidations in the tertiary amines of the dendritic core to produce an unsaturated hydroxylamine with blue fluorescence. Specially, the novel fluorophore was only sensitive to OCl(-), one of reactive oxygen species (ROS), resulting in an irreversible fluorescence turn-off. The fluorescent hydroxylamine was selectively oxidised by OCl(-) to form a labile oxoammonium cation that underwent further degradation. Without using any troublesomely synthetic steps, the novel sensing platform based on the fragmentation of PAMAM dendrimers, can be applied to detect OCl(-) in macrophage cells. The results suggest that the sensing approach may be useful for the detection of intracellular OCl(-) with minimal interference from biological matrixes.

  6. Synthetic methodologies and spatial organization of metal chelate dendrimers and star and hyperbranched polymers.

    Science.gov (United States)

    Dzhardimalieva, Gulzhian I; Uflyand, Igor E

    2017-08-08

    The synthetic methodologies, physico-chemical peculiarities, properties, and structure of metal chelate dendrimers and star and hyperbranched polymers are considered. These compounds are subdivided into molecular, intracomplex, and macrocyclic types which in turn are classified depending on the nature of the donor atoms (N,N-, N,O-, N,S-, O,O-, O,S-, S,S-, P,P-chelates, etc.). Special attention is paid to the features of the preparation of metal chelate star polymers by "arm-first", "core-first" and click-to-chelate approaches. The main data on the synthesis, spatial structure and properties of the metal chelate hyperbranched polymers are summarized. The basic concepts and synthetic strategies leading to the different types of supramolecular metal chelate dendrimers are analyzed. The problems and future prospects of metal chelate dendrimers and star and hyperbranched polymers are outlined. The bibliography includes papers published after 2010.

  7. Dendrimers and Dendrons as Versatile Building Blocks for the Fabrication of Functional Hydrogels.

    Science.gov (United States)

    Kaga, Sadik; Arslan, Mehmet; Sanyal, Rana; Sanyal, Amitav

    2016-04-15

    Hydrogels have emerged as a versatile class of polymeric materials with a wide range of applications in biomedical sciences. The judicious choice of hydrogel precursors allows one to introduce the necessary attributes to these materials that dictate their performance towards intended applications. Traditionally, hydrogels were fabricated using either polymerization of monomers or through crosslinking of polymers. In recent years, dendrimers and dendrons have been employed as well-defined building blocks in these materials. The multivalent and multifunctional nature of dendritic constructs offers advantages in either formulation or the physical and chemical properties of the obtained hydrogels. This review highlights various approaches utilized for the fabrication of hydrogels using well-defined dendrimers, dendrons and their polymeric conjugates. Examples from recent literature are chosen to illustrate the wide variety of hydrogels that have been designed using dendrimer- and dendron-based building blocks for applications, such as sensing, drug delivery and tissue engineering.

  8. Thermal stability of second generation carbosilane dendrimers with peripheral ammonia groups

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, Maria-Cristina, E-mail: cpopescu@icmpp.ro [' Petru Poni' Institute of Macromolecular Chemistry of Romanian Academy (Romania); Gomez, Rafael; Mata, Fco Javier de la; Rasines, Beatriz [Campus Universitario, Universidad de Alcala, Dpto. de Quimica Inorganica (Spain); Simionescu, Bogdan C. [' Petru Poni' Institute of Macromolecular Chemistry of Romanian Academy (Romania)

    2013-10-15

    Thermal analysis has a wide range of applications in pharmaceutical industry, in designing new molecules, control of raw materials, stability, compatibility studies, and development of new formulations. This paper evaluates the thermodynamic properties of two second generation G2 carbosilane dendrimers with peripheral ammonia groups by differential scanning calorimetry and TG/FTIR coupled techniques. The physical transformations have been detected and their thermodynamic characteristics have been estimated and analyzed. Both dendrimers are stable up to 150 Degree-Sign C, have the Tg at 75 and 59 Degree-Sign C and melting temperatures at 113 and 128 Degree-Sign C, respectively. The decomposition process proved to be very complex and takes place in three steps in nitrogen atmosphere and four steps in air, for both types of dendrimers. IR spectroscopic analysis was used to observe the evolution of the gaseous products versus temperature.

  9. Visualizing the Needle in the Haystack: In Situ Hybridization With Fluorescent Dendrimers

    Directory of Open Access Journals (Sweden)

    Gerhart Jacquelyn

    2004-01-01

    Full Text Available In situ hybridization with 3DNA™ dendrimers is a novel tool for detecting low levels of mRNA in tissue sections and whole embryos. Fluorescently labeled dendrimers were used to identify cells that express mRNA for the skeletal muscle transcription factor MyoD in the early chick embryo. A small population of MyoD mRNA positive cells was found in the epiblast prior to the initiation of gastrulation, two days earlier than previously detected using enzymatic or radiolabeled probes for mRNA. When isolated from the epiblast and placed in culture, the MyoD mRNA positive cells were able to differentiate into skeletal muscle cells. These results demonstrate that DNA dendrimers are sensitive and precise tools for identifying low levels of mRNA in single cells and tissues.

  10. Synthesis of an amphiphilic dendrimer-like block copolymer and its application on drug delivery

    KAUST Repository

    Wang, Shuaipeng

    2014-10-27

    Dendrimer-like amphiphilic copolymer is a kind of three-dimensional spherical structure polymer. An amphiphilic dendrimer-like diblock copolymer, PEEGE-G2-b-PEO(OH)12, constituted of a hydrophobic poly(ethoxyethyl glycidol ether) inner core and a hydrophilic poly(ethylene oxide) outer layer, has been successfully synthesized by the living anionic ring-opening polymerization method. The intermediates and targeted products were characterized with 1H NMR spectroscopy and gel permeation chromatography. The application on drug delivery of dendrimer-like diblock copolymer PEEGE-G2-b-PEO(OH)12 using DOX as a model drug was also studied. The drug loading content and encapsulation efficiency were found at 13.07% and 45.75%, respectively. In vitro release experiment results indicated that the drug-loaded micelles exhibited a sustained release behavior under acidic media.

  11. Emerging concepts in dendrimer-based nanomedicine: from design principles to clinical applications.

    Science.gov (United States)

    Kannan, R M; Nance, E; Kannan, S; Tomalia, D A

    2014-12-01

    Dendrimers are discrete nanostructures/nanoparticles with 'onion skin-like' branched layers. Beginning with a core, these nanostructures grow in concentric layers to produce stepwise increases in size that are similar to the dimensions of many in vivo globular proteins. These branched tree-like concentric layers are referred to as 'generations'. The outer generation of each dendrimer presents a precise number of functional groups that may act as a monodispersed platform for engineering favourable nanoparticle-drug and nanoparticle-tissue interactions. These features have attracted significant attention in medicine as nanocarriers for traditional small drugs, proteins, DNA/RNA and in some instances as intrinsically active nanoscale drugs. Dendrimer-based drugs, as well as diagnostic and imaging agents, are emerging as promising candidates for many nanomedicine applications. First, we will provide a brief survey of recent nanomedicines that are either approved or in the clinical approval process. This will be followed by an introduction to a new 'nanoperiodic' concept which proposes nanoparticle structure control and the engineering of 'critical nanoscale design parameters' (CNDPs) as a strategy for optimizing pharmocokinetics, pharmocodynamics and site-specific targeting of disease. This paradigm has led to the emergence of CNDP-directed nanoperiodic property patterns relating nanoparticle behaviour to critical in vivo clinical translation issues such as cellular uptake, transport, elimination, biodistribution, accumulation and nanotoxicology. With a focus on dendrimers, these CNDP-directed nanoperiodic patterns are used as a strategy for designing and optimizing nanoparticles for a variety of drug delivery and imaging applications, including a recent dendrimer-based theranostic nanodevice for imaging and treating cancer. Several emerging preclinical dendrimer-based nanotherapy concepts related to inflammation, neuro-inflammatory disorders, oncology and infectious

  12. Cationic Polyamidoamine Dendrimers as Modulators of EGFR Signaling In Vitro and In Vivo.

    Science.gov (United States)

    Akhtar, Saghir; Al-Zaid, Bashayer; El-Hashim, Ahmed Z; Chandrasekhar, Bindu; Attur, Sreeja; Yousif, Mariam H M; Benter, Ibrahim F

    2015-01-01

    Cationic polyamidoamine (PAMAM) dendrimers are branch-like spherical polymers being investigated for a variety of applications in nanomedicine including nucleic acid drug delivery. Emerging evidence suggests they exhibit intrinsic biological and toxicological effects but little is known of their interactions with signal transduction pathways. We previously showed that the activated (fragmented) generation (G) 6 PAMAM dendrimer, Superfect (SF), stimulated epidermal growth factor receptor (EGFR) tyrosine kinase signaling-an important signaling cascade that regulates cell growth, survival and apoptosis- in cultured human embryonic kidney (HEK 293) cells. Here, we firstly studied the in vitro effects of Polyfect (PF), a non-activated (intact) G6 PAMAM dendrimer, on EGFR tyrosine kinase signaling via extracellular-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) in cultured HEK 293 cells and then compared the in vivo effects of a single administration (10mg/kg i.p) of PF or SF on EGFR signaling in the kidneys of normal and diabetic male Wistar rats. Polyfect exhibited a dose- and time-dependent inhibition of EGFR, ERK1/2 and p38 MAPK phosphorylation in HEK-293 cells similar to AG1478, a selective EGFR inhibitor. Administration of dendrimers to non-diabetic or diabetic animals for 24h showed that PF inhibited whereas SF stimulated EGFR phosphorylation in the kidneys of both sets of animals. PF-mediated inhibition of EGFR phosphorylation as well as SF or PF-mediated apoptosis in HEK 293 cells could be significantly reversed by co-treatment with antioxidants such as tempol implying that both these effects involved an oxidative stress-dependent mechanism. These results show for the first time that SF and PF PAMAM dendrimers can differentially modulate the important EGFR signal transduction pathway in vivo and may represent a novel class of EGFR modulators. These findings could have important clinical implications for the use of PAMAM dendrimers

  13. An Alternative Approach for Acetylation of Amine Terminated Polyamidoamine (PAMAM Dendrimer

    Directory of Open Access Journals (Sweden)

    Surya Prakash Gautam

    2015-09-01

    Full Text Available Aim: Polyamidoamine (PAMAM dendrimers inherent properties have made it the nanocarrier of choice in the current era of innovation. Dendrimer based products are growing and mushrooming like anything in the current time. Although it suffer from hemolytic toxicity which could be reduced by protecting free amino group. Methods: In the present work alternate acetylated method for PAMAM dendrimers was discussed. 1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Linker was used for acetylation. The acetylated conjugate was evaluated for color reaction, Ultraviolet-visible spectroscopy, Fourier Transform infrared spectroscopy, Differential scanning calorimetric, Nuclear magnetic resonance spectra studies. Results: The PAMAM dendrimers were synthesized using divergent approach and further acetylated. Change in λmax values from 282.0 to 282.5 nm was observed for acetylated dendrimers. Characteristic peak of N-H stretch of primary amine at 3284.16 cm-1 was disappeared due to conversion of primary amine to secondary amine. A new peak of -(CO-NH stretch was obtained at 1640.28 cm-1 (medium which shows attachment of acetic acid surface group. The changes in Endothermic peak from 120.56 to 110.40ºC were observed which shows the PAMAM dendrimers surface modifications The peak of -NH2 at 2.99 ppm was replaced by (-NHCOCH3 at 2.42 ppm further supports the proof of acetylation. Conclusions: The spectral data clearly revealed that this approach for acetylation gives considerable amount of acetylation in less time duration with elimination of organic solvent. This method could be employed for regular acetylation of amine terminated nanocarriers. EDC linker mediated capping of amine groups opened a new avenue for acetylation of amine terminated protein/peptides.

  14. Mechanism of Cooperativity and Nonlinear Release Kinetics in Multivalent Dendrimer-Atropine Complexes.

    Science.gov (United States)

    Mukherjee, Jhindan; Wong, Pamela T; Tang, Shengzhuang; Gam, Kristina; Coulter, Alexa; Baker, James R; Choi, Seok Ki

    2015-12-01

    Despite extensive studies on drug delivery using multivalent complexation systems, the biophysical basis for release kinetics remains poorly defined. The present study addresses this aspect involved in the complexation of a fifth generation poly(amidoamine) (PAMAM) dendrimer with atropine, an essential antidote used for treating organophosphate poisoning. First, we designed (1)H NMR titration studies for determining the molecular basis of the drug complexation with a glutarate-modified anionic dendrimer. These provide evidence pointing to a combination of electrostatic and hydrophobic interactions as the driving forces for dendrimer complexation with the alkaloid drug molecule. Second, using LC-MS/MS spectrometry, we determined the dissociation constants (KD) at steady state and also measured the drug release kinetics of atropine complexes with four negatively charged dendrimer types. Each of these dendrimers has a high payload capacity for up to ∼ 100 atropine molecules. However, the affinity of the atropine to the carrier was highly dependent on the drug to dendrimer ratio. Thus, a complex made at a lower loading ratio (≤ 0.1) displayed greater atropine affinity (KD ≈ μM) than other complexes prepared at higher ratios (>10), which showed only mM affinity. This negative cooperative variation in affinity is tightly associated with the nonlinear release kinetics observed for each complex in which drug release occurs more slowly at the later time phase at a lower loading ratio. In summary, the present study provides novel insights on the cooperativity as the mechanistic basis for nonlinear release kinetics observed in multivalent carrier systems.

  15. Dendrimer-like hybrid particles with tunable hierarchical pores

    Science.gov (United States)

    Du, Xin; Li, Xiaoyu; Huang, Hongwei; He, Junhui; Zhang, Xueji

    2015-03-01

    Dendrimer-like silica particles with a center-radial dendritic framework and a synergistic hierarchical porosity have attracted much attention due to their unique open three-dimensional superstructures with high accessibility to the internal surface areas; however, the delicate regulation of the hierarchical porosity has been difficult to achieve up to now. Herein, a series of dendrimer-like amino-functionalized silica particles with tunable hierarchical pores (HPSNs-NH2) were successfully fabricated by carefully regulating and optimizing the various experimental parameters in the ethyl ether emulsion systems via a one-pot sol-gel reaction. Interestingly, the simple adjustment of the stirring rate or reaction temperature was found to be an easy and effective route to achieve the controllable regulation towards center-radial large pore sizes from ca. 37-267 (148 +/- 45) nm to ca. 8-119 (36 +/- 21) nm for HPSNs-NH2 with particle sizes of 300-700 nm and from ca. 9-157 (52 +/- 28) nm to ca. 8-105 (30 +/- 16) nm for HPSNs-NH2 with particle sizes of 100-320 nm. To the best of our knowledge, this is the first successful regulation towards center-radial large pore sizes in such large ranges. The formation of HPSNs-NH2 may be attributed to the complex cross-coupling of two processes: the dynamic diffusion of ethyl ether molecules and the self-assembly of partially hydrolyzed TEOS species and CTAB molecules at the dynamic ethyl ether-water interface of uniform small quasi-emulsion droplets. Thus, these results regarding the elaborate regulation of center-radial large pores and particle sizes not only help us better understand the complicated self-assembly at the dynamic oil-water interface, but also provide a unique and ideal platform as carriers or supports for adsorption, separation, catalysis, biomedicine, and sensor.Dendrimer-like silica particles with a center-radial dendritic framework and a synergistic hierarchical porosity have attracted much attention due to their

  16. Structure activity relationship of dendrimer microbicides with dual action antiviral activity.

    Directory of Open Access Journals (Sweden)

    David Tyssen

    Full Text Available BACKGROUND: Topical microbicides, used by women to prevent the transmission of HIV and other sexually transmitted infections are urgently required. Dendrimers are highly branched nanoparticles being developed as microbicides. However, the anti-HIV and HSV structure-activity relationship of dendrimers comprising benzyhydryl amide cores and lysine branches, and a comprehensive analysis of their broad-spectrum anti-HIV activity and mechanism of action have not been published. METHODS AND FINDINGS: Dendrimers with optimized activity against HIV-1 and HSV-2 were identified with respect to the number of lysine branches (generations and surface groups. Antiviral activity was determined in cell culture assays. Time-of-addition assays were performed to determine dendrimer mechanism of action. In vivo toxicity and HSV-2 inhibitory activity were evaluated in the mouse HSV-2 susceptibility model. Surface groups imparting the most potent inhibitory activity against HIV-1 and HSV-2 were naphthalene disulfonic acid (DNAA and 3,5-disulfobenzoic acid exhibiting the greatest anionic charge and hydrophobicity of the seven surface groups tested. Their anti-HIV-1 activity did not appreciably increase beyond a second-generation dendrimer while dendrimers larger than two generations were required for potent anti-HSV-2 activity. Second (SPL7115 and fourth generation (SPL7013 DNAA dendrimers demonstrated broad-spectrum anti-HIV activity. However, SPL7013 was more active against HSV and blocking HIV-1 envelope mediated cell-to-cell fusion. SPL7013 and SPL7115 inhibited viral entry with similar potency against CXCR4-(X4 and CCR5-using (R5 HIV-1 strains. SPL7013 was not toxic and provided at least 12 h protection against HSV-2 in the mouse vagina. CONCLUSIONS: Dendrimers can be engineered with optimized potency against HIV and HSV representing a unique platform for the controlled synthesis of chemically defined multivalent agents as viral entry inhibitors. SPL7013 is

  17. History, Classification, Molecular Structure and Properties of Dendrimers which are a New Concept in Textile

    Directory of Open Access Journals (Sweden)

    Osman NAMIRTI

    2011-02-01

    Full Text Available Over the last 20 years polymer chemistry has created a number of non-lineer structures and introduction of a large number of branches during the polymer synthesis leads to obtain molecules with many end groups. Two types of these polymers are regularly branched "dendrimers" and "hyperbranched polymers" where branching is formed randomly. In this article knowledge about history, classification, molecular structure and properties of dendrimers which have found various application areas also in textile due to their special structures is given.

  18. Fluorescence enhancement of DNA-silver nanoclusters from guanine proximity

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Hsin-chih [Los Alamos National Laboratory; Sharma, Jaswinder [Los Alamos National Laboratory; Yoo, Hyojong [Los Alamos National Laboratory; Martinez, Jennifer S [Los Alamos National Laboratory

    2010-01-01

    Oligonucleotide-templated, silver nanoclusters (DNA/Ag NCs) are a versatile set of fluorophores and have already been used for live cell imaging, detection of specific metal ions, and single-nucleotide variation identification. Compared to commonly used organic dyes, these fluorescent nanoclusters have much better photostability and are often a few times brighter. Owing to their small size, simple preparation, and biocompatibility (i.e. made of nontoxic metals), DNA/Ag NCs should find more applications in biological imaging and chemical detection in the years to come. While clearly promising as new fluorophores, DNA/Ag NCs possess a unique and poorly understood dynamic process not shared by organic dyes or photoluminescent nanocrystals - the conversion among different NC species due to silver oxidation/reduction or NC regrouping. While this environmental sensitivity can be viewed as a drawback, in the appropriate context, it can be used as a sensor or reporter. Often reversible, conversions among different NC species have been found to depend upon a number of factors, including time, temperature, oxygen and salt content. In this communication, we report significant fluorescence enhancement of DNA/Ag NCs via interactions with guanine-rich DNA sequences. Moreover, we demonstrated this property can be used for sensitive detection of specific target DNA from a human oncogene (i.e. Braf gene).

  19. PE-CVD fabrication of germanium nanoclusters for memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Duerkop, T. [Institut fuer Materialien und Bauelemente der Elektronik, Leibniz Universitaet Hannover, Appelstrasse 11a, 30167 Hannover (Germany)], E-mail: duerkop@mbe.uni-hannover.de; Bugiel, E. [Institut fuer Materialien und Bauelemente der Elektronik, Leibniz Universitaet Hannover, Appelstrasse 11a, 30167 Hannover (Germany); Costina, I. [IHP GmbH, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Ott, A.; Peibst, R.; Hofmann, K.R. [Institut fuer Materialien und Bauelemente der Elektronik, Leibniz Universitaet Hannover, Appelstrasse 11a, 30167 Hannover (Germany)

    2008-02-15

    We have investigated Ge nanoclusters (Ge-NC) embedded in silicon dioxide, whose fundamental properties promise improved characteristics in NC flash memory devices as compared to Si nanoclusters. We present a simple new method, based on plasma-enhanced CVD (PE-CVD) deposition of amorphous Ge (a-Ge) onto SiO{sub 2}, to create gate stacks with embedded Ge-NC at vertically well-controlled positions suitable for use in flash memory devices. This process minimizes the exposure of Ge to environmental influences by depositing a-Ge as well as a SiO{sub 2} cap layer in situ within the same deposition chamber. Subsequent high-temperature anneals compatible with the temperature budget of CMOS processing are used for the actual cluster formation. Variation of annealing temperature and duration of this step as well as the thickness of the initial Ge layer controls the average cluster radius and density, as determined by transmission electron microscopy (TEM). Measurements of electrical properties show the capability of samples with NC to store charge.

  20. Multivalency effects on Pseudomonas aeruginosa biofilm inhibition and dispersal by glycopeptide dendrimers targeting lectin LecA.

    Science.gov (United States)

    Bergmann, Myriam; Michaud, Gaëlle; Visini, Ricardo; Jin, Xian; Gillon, Emilie; Stocker, Achim; Imberty, Anne; Darbre, Tamis; Reymond, Jean-Louis

    2016-01-01

    The galactose specific lectin LecA partly mediates the formation of antibiotic resistant biofilms by Pseudomonas aeruginosa, an opportunistic pathogen causing lethal airways infections in immunocompromised and cystic fibrosis patients, suggesting that preventing LecA binding to natural saccharides might provide new opportunities for treatment. Here 8-fold (G3) and 16-fold (G4) galactosylated analogs of GalAG2, a tetravalent G2 glycopeptide dendrimer LecA ligand and P. aeruginosa biofilm inhibitor, were obtained by convergent chloroacetyl thioether (ClAc) ligation between 4-fold or 8-fold chloroacetylated dendrimer cores and digalactosylated dendritic arms. Hemagglutination inhibition, isothermal titration calorimetry and biofilm inhibition assays showed that G3 dendrimers bind LecA slightly better than their parent G2 dendrimers and induce complete biofilm inhibition and dispersal of P. aeruginosa biofilms, while G4 dendrimers show reduced binding and no biofilm inhibition. A binding model accounting for the observed saturation of glycopeptide dendrimer galactosyl groups and LecA binding sites is proposed based on the crystal structure of a G3 dendrimer LecA complex.

  1. X-ray computed tomography contrast agents prepared by seeded growth of gold nanoparticles in PEGylated dendrimer

    Science.gov (United States)

    Kojima, Chie; Umeda, Yasuhito; Ogawa, Mikako; Harada, Atsushi; Magata, Yasuhiro; Kono, Kenji

    2010-06-01

    Gold nanoparticles (Au NPs) are a potential x-ray computed tomography (CT) contrast agent. A biocompatible and bioinactive surface is necessary for application of gold nanoparticle to CT imaging. Polyethylene glycol (PEG)-attached dendrimers have been used as a drug carrier with long blood circulation. In this study, the Au NPs were grown in the PEGylated dendrimer to produce a CT contrast agent. The Au NPs were grown by adding gold ions and ascorbic acid at various equivalents to the Au NP-encapsulated dendrimer solution. Both size and surface plasmon absorption of the grown Au NPs increased with adding a large number of gold ions. The x-ray attenuation of the Au NPs also increased after the seeded growth. The Au NPs grown in the PEG-attached dendrimer at the maximum under our conditions exhibited a similar CT value to a commercial iodine agent, iopamidol, in vitro. The Au NP-loaded PEGylated dendrimer and iopamidol were injected into mice and CT images were obtained at different times. The Au NP-loaded PEGylated dendrimer achieved a blood pool imaging, which was greater than a commercial iodine agent. Even though iopamidol was excreted rapidly, the PEGylated dendrimer loading the grown Au NP was accumulated in the liver.

  2. Interaction of cationic carbosilane dendrimers and their complexes with siRNA with erythrocytes and red blood cell ghosts.

    Science.gov (United States)

    Wrobel, Dominika; Kolanowska, Katarzyna; Gajek, Arkadiusz; Gomez-Ramirez, Rafael; de la Mata, Javier; Pedziwiatr-Werbicka, Elżbieta; Klajnert, Barbara; Waczulikova, Iveta; Bryszewska, Maria

    2014-03-01

    We have investigated the interactions between cationic NN16 and BDBR0011 carbosilane dendrimers with red blood cells or their cell membranes. The carbosilane dendrimers used possess 16 cationic functional groups. Both the dendrimers are made of water-stable carbon-silicon bonds, but NN16 possesses some oxygen-silicon bonds that are unstable in water. The nucleic acid used in the experiments was targeted against GAG-1 gene from the human immunodeficiency virus, HIV-1. By binding to the outer leaflet of the membrane, carbosilane dendrimers decreased the fluidity of the hydrophilic part of the membrane but increased the fluidity of the hydrophobic interior. They induced hemolysis, but did not change the morphology of the cells. Increasing concentrations of dendrimers induced erythrocyte aggregation. Binding of short interfering ribonucleic acid (siRNA) to a dendrimer molecule decreased the availability of cationic groups and diminished their cytotoxicity. siRNA-dendrimer complexes changed neither the fluidity of biological membranes nor caused cell hemolysis. Addition of dendriplexes to red blood cell suspension induced echinocyte formation.

  3. Preparation and surface enhanced Raman scattering behavior of Ag-coated C{sub 60} nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Shi-Zhao; Yin, Die-er; Li, Xiangqing; Mu, Jin, E-mail: mujin@sit.edu.cn

    2013-12-01

    Ag-coated C{sub 60} nanoclusters were prepared and characterized with X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption isotherm measurement. The Ag-coated C{sub 60} nanoclusters were assembled on the glass substrate to form a thin film using the layer-by-layer technique. Meanwhile, the surface enhanced Raman scattering (SERS) of musk xylene adsorbed on the film of Ag-coated C{sub 60} nanoclusters was explored. The results indicated that the film of Ag-coated C{sub 60} nanoclusters was a unique SERS-active substrate with a detection limit of 10{sup −9} mol L{sup −1} for musk xylene. Furthermore, the surface enhanced mechanisms were discussed preliminarily.

  4. Melting Properties of Medium-Sized Silicon Nanoclusters: A Molecular Dynamics Study

    Science.gov (United States)

    Li, Haipeng; Xu, Runfeng; Bi, Zetong; Shen, Xiaopeng; Han, Kui

    2017-07-01

    The structures and melting properties of the medium-sized silicon nanoclusters have been comparatively studied using the molecular dynamics method. Structural and thermodynamic parameters are used to characterize the melting properties of the clusters. The size dependence of the melting temperature of silicon nanoclusters is determined using the computation results. Different from the homogeneous melting of bulk silicon, melting of silicon nanoparticles proceeds over a finite temperature range due to surface effects, which shows the heterogeneous melting of nanoclusters. We found that the melting starts at the cluster surface and progressively shifts into the core region. This study provides a fundamental perspective on the melting behaviors of semiconductor silicon nanoclusters at the atomistic level.

  5. Self-Assembled Superparamagnetic Iron Oxide Nanoclusters for Universal Cell Labeling and MRI

    Science.gov (United States)

    Chen, Shuzhen; Zhang, Jun; Jiang, Shengwei; Lin, Gan; Luo, Bing; Yao, Huan; Lin, Yuchun; He, Chengyong; Liu, Gang; Lin, Zhongning

    2016-05-01

    Superparamagnetic iron oxide (SPIO) nanoparticles have been widely used in a variety of biomedical applications, especially as contrast agents for magnetic resonance imaging (MRI) and cell labeling. In this study, SPIO nanoparticles were stabilized with amphiphilic low molecular weight polyethylenimine (PEI) in an aqueous phase to form monodispersed nanocomposites with a controlled clustering structure. The iron-based nanoclusters with a size of 115.3 ± 40.23 nm showed excellent performance on cellular uptake and cell labeling in different types of cells, moreover, which could be tracked by MRI with high sensitivity. The SPIO nanoclusters presented negligible cytotoxicity in various types of cells as detected using MTS, LDH, and flow cytometry assays. Significantly, we found that ferritin protein played an essential role in protecting stress from SPIO nanoclusters. Taken together, the self-assembly of SPIO nanoclusters with good magnetic properties provides a safe and efficient method for universal cell labeling with noninvasive MRI monitoring capability.

  6. The role of oxygen and water on molybdenum nanoclusters for electro catalytic ammonia production

    DEFF Research Database (Denmark)

    Howalt, Jakob Geelmuyden; Vegge, Tejs

    2014-01-01

    . In this study, we present theoretical investigations of the influence of oxygen adsorption and reduction on pure and nitrogen covered molybdenum nanocluster electro catalysts for electrochemical reduction of N2 to NH3 with the purpose of understanding oxygen and water poisoning of the catalyst. Density...... functional theory calculations are used in combination with the computational hydrogen electrode approach to calculate the free energy profile for electrochemical protonation of O and N2 species on cuboctahedral Mo13 nanoclusters. The calculations show that the molybdenum nanocluster will preferentially bind...... are -0.72 V or lower for all oxygen coverages studied, and it is thus possible to (re)activate (partially) oxidized nanoclusters for electrochemical ammonia production, e.g., using a dry proton conductor or an aqueous electrolyte. At lower oxygen coverages, nitrogen molecules can adsorb to the surface...

  7. Nanocluster metal films as thermoelectric material for radioisotope mini battery unit

    Science.gov (United States)

    Borisyuk, P. V.; Krasavin, A. V.; Tkalya, E. V.; Lebedinskii, Yu. Yu.; Vasiliev, O. S.; Yakovlev, V. P.; Kozlova, T. I.; Fetisov, V. V.

    2016-10-01

    The paper is devoted to studying the thermoelectric and structural properties of films based on metal nanoclusters (Au, Pd, Pt). The experimental results of the study of single nanoclusters' tunneling conductance obtained with scanning tunneling spectroscopy are presented. The obtained data allowed us to evaluate the thermoelectric power of thin film consisting of densely packed individual nanoclusters. It is shown that such thin films can operate as highly efficient thermoelectric materials. A scheme of miniature thermoelectric radioisotope power source based on the thorium-228 isotope is proposed. The efficiency of the radioisotope battery using thermoelectric converters based on nanocluster metal films is shown to reach values up to 1.3%. The estimated characteristics of the device are comparable with the parameters of up-to-date radioisotope batteries based on nickel-63.

  8. A colloidal assembly approach to synthesize magnetic porous composite nanoclusters for efficient protein adsorption

    Science.gov (United States)

    Yang, Qi; Lan, Fang; Yi, Qiangying; Wu, Yao; Gu, Zhongwei

    2015-10-01

    A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation.A combination strategy of the inverse emulsion crosslinking approach and the colloidal assembly technique is first proposed to synthesize Fe3O4/histidine composite nanoclusters as new-type magnetic porous nanomaterials. The nanoclusters possess uniform morphology, high magnetic content and excellent protein adsorption capacity, exhibiting their great potential for bio-separation. Electronic supplementary information (ESI) available: Experimental details. See DOI: 10.1039/c5nr05800g

  9. The Influence of Ultrasound on Formation of Self-organized Uniform Nanoclusters

    Directory of Open Access Journals (Sweden)

    R.M. Peleshchak

    2016-06-01

    Full Text Available The non-linear diffusion-deformation theory of self-organization of nanoclusters of dot defects in semiconductor exposed to ultrasound treatment that considers the interaction of defects among themselves and with atoms of a matrix via the elastic field created by dot defects and an acoustic wave is developed. Within this theory the influence of ultrasound on the conditions of formation of spherical nanoclusters and their radius is investigated. The nanocluster size depending on average concentration of defects and amplitude of an acoustic wave is determined. It is established that ultrasonic treatment of the semiconductor in the process of formation of an ensemble of nanoclusters leads to reduction of dispersion of their sizes.

  10. Automated electrodeposition of bimetallic noble-metal nanoclusters via redox-replacement reactions for electrocatalysis

    CSIR Research Space (South Africa)

    Mkwizu, TS

    2009-01-01

    Full Text Available Nanoclusters of bimetallic composition involving platinum with gold or ruthenium were sequentially deposited via redoxreplacement of electrodeposited sacrificial Cu adlayers for controlling the deposition of the noble metals. These steps were...

  11. Probing the Absorption and Emission Transition Dipole Moment of DNA Stabilized Silver Nanoclusters

    DEFF Research Database (Denmark)

    Hooley, Emma Nicole; Carro Temboury, Miguel R.; Vosch, Tom André Jos

    2017-01-01

    Using single molecule polarization measurements, we investigate the excitation and emission polarization characteristics of DNA stabilized silver nanoclusters (C24-AgNCs). Although small changes in the polarization generally accompany changes to the emission spectrum, the emission and excitation ...

  12. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    National Research Council Canada - National Science Library

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H A; Toivonen, Juha

    2016-01-01

    .... A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode...

  13. Developing a Millifluidic Platform for the Synthesis of Ultrasmall Nanoclusters: Ultrasmall Copper Nanoclusters as a Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Sanchita; Miller, Jeffrey T; Li, Yuehao; Nandakumar, Krishnaswamy; Kumar, Challa S.S.R.

    2012-02-02

    The future of lab-on-a-chip devices for the synthesis of nanomaterials hinges on the successful development of high-throughput methods with better control over their size. While significant effort in this direction mainly focuses on developing “difficult to fabricate” complex microfluidic reactors, scant attention has been paid to the “easy to fabricate” and simple millifluidic systems that could provide the required control as well as high throughput. By utilizing numerical simulation of fluids within the millifluidic space at different flow rates, the results presented here show velocity profiles and residence time distributions similar to the case of microfluidics. By significantly reducing the residence time and residence time distribution, a continuous flow synthesis of ultrasmall copper nanoclusters (UCNCs) with exceptional colloidal stability is achieved. In-situ synchrotron-radiation-based X-ray absorption spectroscopy (XAS) reveal that the as-prepared clusters are about 1 nm, which is further supported by transmission electron microscopy and UV–vis spectroscopy studies. The clusters reported here are the smallest ever produced using a lab-on-a-chip platform. When supported on silica, they are found to efficiently catalyze C–H oxidation reactions, hitherto unknown to be catalyzed by Cu. This work suggests that a millifluidic platform can be an inexpensive, versatile, easy-to-use, and powerful tool for nanoparticle synthesis in general, and more specifically for ultrasmall nanoclusters (UNCs).

  14. New dendrimers containing a single cobaltocenium unit covalently attached to the apical position of Newkome dendrons: electrochemistry and guest binding interactions with cucurbit[7]uril.

    Science.gov (United States)

    Sobransingh, David; Kaifer, Angel E

    2006-12-05

    Two new dendrimer series were prepared and characterized. These dendrimers contain a single bis(cyclopentadienyl)cobalt(III) (cobaltocenium, Cob+) unit covalently attached to the apical (focal) position of Newkome-type dendrons, ranging in size from first to third generation. The dendrimers in the first series (1ECob+-3ECob+) are hydrophobic and have 3, 9, and 27 tert-butyl esters on their peripheries, whereas the dendrimers in the second series (1Cob+-3Cob+) are hydrophilic with 3, 9, and 27 carboxylic acid groups on their surfaces, respectively. In voltammetric experiments, all dendrimers showed the expected one-electron reversible reduction of the cobaltocenium center, and the heterogeneous rate of electron transfer decreased with generation in both dendrimer series. The host-guest binding interactions between water-soluble dendrimers 1Cob+-3Cob+ and the cucurbit[7]uril (CB7) host were investigated using 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and electrochemical techniques. The association equilibrium constants (K) for all dendrimer guests were significantly lower than that measured for the inclusion complex between underivatized Cob+ and CB7 (K = 5.7 x 10(9) M(-1)). Nonetheless, among the three dendrimers surveyed, the second-generation dendrimer, 2Cob+, afforded optimum stabilization for the CB7 inclusion complex.

  15. Laser-assisted atom probe tomography investigation of magnetic FePt nanoclusters: First experiments

    Energy Technology Data Exchange (ETDEWEB)

    Folcke, E.; Larde, R. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Le Breton, J.M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Gruber, M.; Vurpillot, F. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Shield, J.E.; Rui, X. [Department of Mechanical and Materials Engineering, Nebraska Center for Materials and Nanoscience, University of Nebraska, N104 WSEC, Lincoln, NE 68588 (United States); Patterson, M.M. [Department of Physics, University of Wisconsin-Stout, Menomonie, WI 54751 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer FePt nanoclusters dispersed in a Cr matrix were studied by atom probe tomography. Black-Right-Pointing-Pointer Simulated experiments were conducted to study the artefacts of the analysis. Black-Right-Pointing-Pointer In FePt nanoclusters, Fe and Pt are present in equiatomic proportions. Black-Right-Pointing-Pointer FePt nanoclusters are homogeneous, no core-shell structure is observed. - Abstract: FePt nanoclusters dispersed in a Cr matrix have been investigated by laser-assisted atom probe tomography. The results were analysed according to simulated evaporation experiments. Three-dimensional (3D) reconstructions reveal the presence of nanoclusters roughly spherical in shape, with a size in good agreement with previous transmission electron microscopy observations. Some clusters appear to be broken up after the evaporation process due to the fact that the Cr matrix has a lower evaporation field than Fe and Pt. It is thus shown that the observed FePt nanoclusters are chemically homogeneous. They contain Fe and Pt in equiatomic proportions, with no core-shell structure observed.

  16. Enhancement of the Hydrogen Evolution Reaction from Ni-MoS2 Hybrid Nanoclusters

    Science.gov (United States)

    2016-01-01

    This report focuses on a novel strategy for the preparation of transition metal–MoS2 hybrid nanoclusters based on a one-step, dual-target magnetron sputtering, and gas condensation process demonstrated for Ni-MoS2. Aberration-corrected STEM images coupled with EDX analysis confirms the presence of Ni and MoS2 in the hybrid nanoclusters (average diameter = 5.0 nm, Mo:S ratio = 1:1.8 ± 0.1). The Ni-MoS2 nanoclusters display a 100 mV shift in the hydrogen evolution reaction (HER) onset potential and an almost 3-fold increase in exchange current density compared with the undoped MoS2 nanoclusters, the latter effect in agreement with reported DFT calculations. This activity is only reached after air exposure of the Ni-MoS2 hybrid nanoclusters, suggested by XPS measurements to originate from a Ni dopant atoms oxidation state conversion from metallic to 2+ characteristic of the NiO species active to the HER. Anodic stripping voltammetry (ASV) experiments on the Ni-MoS2 hybrid nanoclusters confirm the presence of Ni-doped edge sites and reveal distinctive electrochemical features associated with both doped Mo-edge and doped S-edge sites which correlate with both their thermodynamic stability and relative abundance.

  17. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

    Science.gov (United States)

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-02-10

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

  18. Ligand-exchange synthesis of selenophenolate-capped Au25 nanoclusters.

    Science.gov (United States)

    Meng, Xiangming; Xu, Qian; Wang, Shuxin; Zhu, Manzhou

    2012-07-21

    We report the synthesis and characterization of selenophenolate-capped 25-gold-atom nanoclusters via a ligand-exchange approach. In this method, phenylethanethiolate (PhCH(2)CH(2)S) capped Au(25) nanoclusters are utilized as the starting material, which is subject to ligand-exchange with selenophenol (PhSeH). The as-obtained cluster product is confirmed to be selenophenolate-protected Au(25) nanoclusters through characterization by electrospray ionization (ESI) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), thermogravimetric analysis (TGA), elemental analysis (EA), UV-Vis and (1)H/(13)C NMR spectroscopies. The ligand-exchange synthesis of [Au(25)(SePh)(18)](-)[(C(8)H(17))(4)N](+) nanoclusters demonstrates that the core size of gold nanoclusters is retained in the thiolate-to-selenolate exchange process and that the 18 surface thiolate ligands can be completely exchanged by selenophenolate, rather than giving rise to a mixed ligand shell on the cluster. The two types of Au(25)L(18) (L = thiolate or selenolate) nanoclusters also show some differences in stability and optical properties.

  19. Synthesis of selenolate-protected Au18(SeC6H5)14 nanoclusters.

    Science.gov (United States)

    Xu, Qian; Wang, Shuxin; Liu, Zhao; Xu, Guoyong; Meng, Xiangming; Zhu, Manzhou

    2013-02-07

    This work reports the first synthesis of selenophenolate-protected Au(18)(SePh)(14) nanoclusters. This cluster exhibits distinct differences from its thiolate analogue in terms of optical absorption properties. The Au(18)(SePh)(14) nanoclusters were obtained via a controlled reaction of Au(25)(SCH(2)CH(2)Ph)(18) with selenophenol. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) revealed the crude product to contain predominantly Au(18)(SePh)(14) nanoclusters, and side products include Au(15)(SePh)(13), Au(19)(SePh)(15) and Au(20)(SePh)(16). High-performance liquid chromatography (HPLC) was employed to isolate Au(18)(SePh)(14) nanoclusters. The results of thermogravimetric analysis (TGA), elemental analysis (EA), and (1)H/(13)C NMR spectroscopy confirmed the cluster composition. To the best of our knowledge, this is the first report of selenolate-protected Au(18) nanoclusters. Future theoretical and X-ray crystallographic work will reveal the geometric structure and the nature of selenolate-gold bonding in the nanocluster.

  20. Design of an ultrasmall Au nanocluster-CeO2 mesoporous nanocomposite catalyst for nitrobenzene reduction.

    Science.gov (United States)

    Chong, Hanbao; Li, Peng; Xiang, Ji; Fu, Fangyu; Zhang, Dandan; Ran, Xiaorong; Zhu, Manzhou

    2013-08-21

    In this work we are inspired to explore gold nanoclusters supported on mesoporous CeO2 nanospheres as nanocatalysts for the reduction of nitrobenzene. Ultrasmall Au nanoclusters (NCs) and mesoporous CeO2 nanospheres were readily synthesized and well characterized. Due to their ultrasmall size, the as-prepared Au clusters can be easily absorbed into the mesopores of the mesoporous CeO2 nanospheres. Owing to the unique mesoporous structure of the CeO2 support, Au nanoclusters in the Au@CeO2 may effectively prevent the aggregation which usually results in a rapid decay of the catalytic activity. It is notable that the ultrasmall gold nanoclusters possess uniform size distribution and good dispersibility on the mesoporous CeO2 supports. Compared to other catalyst systems with different oxide supports, the as-prepared Au nanocluster-CeO2 nanocomposite nanocatalysts showed efficient catalytic performance in transforming nitrobenzene into azoxybenzene. In addition, a plausible mechanism was deeply investigated to explain the transforming process. Au@CeO2 exhibited efficient catalytic activity for reduction of nitrobenzene. This strategy may be easily extended to fabricate many other heterogeneous catalysts including ultrasmall metal nanoclusters and mesoporous oxides.

  1. Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

    Science.gov (United States)

    Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

    2017-01-01

    In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)-capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters. PMID:28208642

  2. Assessment of nanopolyamidoamine-G7 dendrimer antibacterial effect in aqueous solution

    Directory of Open Access Journals (Sweden)

    Mitra Gholami

    2016-06-01

    Conclusion: The NPAMAM-G7 dendrimer with end amine groups exhibited a positive impact on the removal of standard strains, gram-positive and gram-negative bacteria. Therefore, it is possible to use these nanodendrimers as antibacterial in the future.

  3. PAMAM dendrimer-coated iron oxide nanoparticles: synthesis and characterization of different generations

    Energy Technology Data Exchange (ETDEWEB)

    Khodadust, Rouhollah, E-mail: raoul.1357@gmail.com; Unsoy, Gozde [Middle East Technical University, Department of Biotechnology (Turkey); Yalc Latin-Small-Letter-Dotless-I n, Serap [Ahi Evran University, Department of Food Engineering (Turkey); Gunduz, Gungor [Middle East Technical University, Department of Chemical Engineering (Turkey); Gunduz, Ufuk, E-mail: ufukg@metu.edu.tr [Middle East Technical University, Department of Biotechnology (Turkey)

    2013-03-15

    This study focuses on the synthesis and characterization of different generations (G{sub 0}-G{sub 7}) of polyamidoamine (PAMAM) dendrimer-coated magnetic nanoparticles (DcMNPs). In this study, superparamagnetic iron oxide nanoparticles were synthesized by co-precipitation method. The synthesized nanoparticles were modified with aminopropyltrimethoxysilane for dendrimer coating. Aminosilane-modified MNPs were coated with PAMAM dendrimer. The characterization of synthesized nanoparticles was performed by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering, and vibrating sample magnetometry (VSM) analyses. TEM images demonstrated that the DcMNPs have monodisperse size distribution with an average particle diameter of 16 {+-} 5 nm. DcMNPs were found to be superparamagnetic through VSM analysis. The synthesis, aminosilane modification, and dendrimer coating of iron oxide nanoparticles were validated by FTIR and XPS analyses. Cellular internalization of nanoparticles was studied by inverted light scattering microscopy, and cytotoxicity was determined by XTT analysis. Results demonstrated that the synthesized DcMNPs, with their functional groups, symmetry perfection, size distribution, improved magnetic properties, and nontoxic characteristics could be suitable nanocarriers for targeted cancer therapy upon loading with various anticancer agents.

  4. A novel Ag+ cation sensor based on polyamidoamine dendrimer modified with 1,8-naphthalimide derivatives

    Science.gov (United States)

    Dodangeh, Mohammad; Gharanjig, Kamaladin; Arami, Mokhtar

    2016-02-01

    In this study, 4-amino-1,8-naphthalimide-conjugated polyamidoamine dendrimer was synthesized and characterized and its potentiality as a cation sensor was investigated. 4-Amino-1,8-naphthalic anhydride reacted with polyamidoamine dendrimer and the product was characterized using FTIR, 1H NMR, 13C NMR and melting point analysis method. The synthesized compound was applied to detect various cations in water media and N,N-dimethylformamide (DMF) via monitoring the quenching of the fluorescence intensity. Furthermore, various metal cations including Cu2 +, Ni2 +, Zn2 +, Pb2 +,Ca2 +, Ba2 +, Cd2 +, Hg2 +, Fe2 +, Fe3 + and Ag+ were tested. The complexes formed between the synthesized compound and metal cations in solution and their effects on Photoinduced Electron Transfer (PET) process were investigated regarding the potential application of the newly-synthesized dendrimer as a colorimetric and fluorescent sensor for such cations. The results clearly confirmed that the 1,8-naphthalimide groups surrounding the central dendrimer core showed strong green fluorescence emission at 553 nm. This effect considerably decreased with the introduction of all cations, except Ag+ where the fluorescence quenching effect was remarkable and more dominant. Therefore, it can be concluded that the synthesized dye has the potentiality of being a highly sensitive and selective fluorescence sensor for Ag+ cation.

  5. Electrochemical aptasensor of cellular prion protein based on modified polypyrrole with redox dendrimers.

    Science.gov (United States)

    Miodek, A; Castillo, G; Hianik, T; Korri-Youssoufi, H

    2014-06-15

    This work consists of the development of an electrochemical aptasensor based on polyprrole modified with redox dendrimers, able to detect human cellular prions PrP(C) with high sensitivity. The gold surface was modified by conductive polypyrrole film coupled to polyamidoamine dendrimers of fourth generation (PAMAM G4) and ferrocenyl group as redox marker. The aptamers were immobilized on the surface via biotin/streptavidin chemistry. Electrochemical signal was detected by ferrocenyl group incorporated between dendrimers and aptamers layers. We demonstrated that the interaction between aptamer and prion protein led to variation in electrochemical signal of the ferrocenyl group. The kinetics parameters (diffusion coefficient D and heterogeneous constant transfer ket) calculated from electrochemical signals demonstrate that the variation in redox signal results from the lower diffusion process of ions during redox reaction after prion interaction due to bulk effect of larger protein. The association of redox dendrimers with conducting polypyrrole leads to high sensitivity of PrP(C) determination with detection limit of 0.8 pM, which is three orders of magnitude lower, compared to flat ferrocene-functionalized polypyrrole. Detection of PrP(C) in spiked blood plasma has been achieved and demonstrated a recovery up to 90%. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Optimization and in vivo toxicity evaluation of G4.5 PAMAM dendrimer-risperidone complexes.

    Directory of Open Access Journals (Sweden)

    Maria Jimena Prieto

    Full Text Available Risperidone is an approved antipsychotic drug belonging to the chemical class of benzisoxazole. This drug has low solubility in aqueous medium and poor bioavailability due to extensive first-pass metabolism and high protein binding (>90%. Since new strategies to improve efficient treatments are needed, we studied the efficiency of anionic G4.5 PAMAM dendrimers as nanocarriers for this therapeutic drug. To this end, we explored dendrimer-risperidone complexation dependence on solvent concentration, pH and molar relationship. The best dendrimer-risperidone incorporation (46 risperidone molecules per dendrimer was achieved with a mixture of chloroform:methanol 50∶50 v/v solution pH 3. In addition, to explore the possible effects of this complex, in vivo studies were carried out in the zebrafish model. Changes in the development of dopaminergic neurons and motoneurons were studied using tyrosine hydroxylase and calretinin, respectively. Physiological changes were studied through histological sections stained with hematoxylin-eosin to observe possible morphological brain changes. The most significant changes were observed when larvae were treated with free risperidone, and no changes were observed when larvae were treated with the complex.

  7. Optimization and in vivo toxicity evaluation of G4.5 PAMAM dendrimer-risperidone complexes.

    Science.gov (United States)

    Prieto, Maria Jimena; del Rio Zabala, Nahuel Eduardo; Marotta, Cristian Hernán; Carreño Gutierrez, Hector; Arévalo Arévalo, Rosario; Chiaramoni, Nadia Silvia; del Valle Alonso, Silvia

    2014-01-01

    Risperidone is an approved antipsychotic drug belonging to the chemical class of benzisoxazole. This drug has low solubility in aqueous medium and poor bioavailability due to extensive first-pass metabolism and high protein binding (>90%). Since new strategies to improve efficient treatments are needed, we studied the efficiency of anionic G4.5 PAMAM dendrimers as nanocarriers for this therapeutic drug. To this end, we explored dendrimer-risperidone complexation dependence on solvent concentration, pH and molar relationship. The best dendrimer-risperidone incorporation (46 risperidone molecules per dendrimer) was achieved with a mixture of chloroform:methanol 50∶50 v/v solution pH 3. In addition, to explore the possible effects of this complex, in vivo studies were carried out in the zebrafish model. Changes in the development of dopaminergic neurons and motoneurons were studied using tyrosine hydroxylase and calretinin, respectively. Physiological changes were studied through histological sections stained with hematoxylin-eosin to observe possible morphological brain changes. The most significant changes were observed when larvae were treated with free risperidone, and no changes were observed when larvae were treated with the complex.

  8. Dendrimer-Linked Antifreeze Proteins Have Superior Activity and Thermal Recovery.

    Science.gov (United States)

    Stevens, Corey A; Drori, Ran; Zalis, Shiran; Braslavsky, Ido; Davies, Peter L

    2015-09-16

    By binding to ice, antifreeze proteins (AFPs) depress the freezing point of a solution and inhibit ice recrystallization if freezing does occur. Previous work showed that the activity of an AFP was incrementally increased by fusing it to another protein. Even larger increases in activity were achieved by doubling the number of ice-binding sites by dimerization. Here, we have combined the two strategies by linking multiple outward-facing AFPs to a dendrimer to significantly increase both the size of the molecule and the number of ice-binding sites. Using a heterobifunctional cross-linker, we attached between 6 and 11 type III AFPs to a second-generation polyamidoamine (G2-PAMAM) dendrimer with 16 reactive termini. This heterogeneous sample of dendrimer-linked type III constructs showed a greater than 4-fold increase in freezing point depression over that of monomeric type III AFP. This multimerized AFP was particularly effective at ice recrystallization inhibition activity, likely because it can simultaneously bind multiple ice surfaces. Additionally, attachment to the dendrimer has afforded the AFP superior recovery from heat denaturation. Linking AFPs together via polymers can generate novel reagents for controlling ice growth and recrystallization.

  9. Simulation of some dynamical aspects of the photophysics of dye molecules encapsulated in a dendrimer

    Energy Technology Data Exchange (ETDEWEB)

    Teobaldi, Gilberto [Dipartimento di Chimica ' G. Ciamician' , Universita di Bologna, Via F. Selmi 2, Bologna I-40126 (Italy); Zerbetto, Francesco [Dipartimento di Chimica ' G. Ciamician' , Universita di Bologna, Via F. Selmi 2, Bologna I-40126 (Italy)]. E-mail: francesco.zerbetto@unibo.it

    2005-03-15

    We use a combination of molecular dynamics and quantum chemical calculations to investigate the photophysics of Eosin Y encapsulated in a fourth generation of poly-propylene amine dendrimer functionalized in the periphery with dansyl units. Once in contact with the macromolecule, the guests display a double exponential decay of the excited states that is reproduced by the present model.

  10. Comparison of MRI properties between derivatized DTPA and DOTA gadolinium-dendrimer conjugates

    Science.gov (United States)

    Nwe, K.; Bernardo, M; Regino, C. A. S.; Williams, M; Brechbiel, M. W.

    2010-01-01

    In this report we directly compare the in vivo and in vitro MRI properties of gadolinium-dendrimer conjugates of derivatized acyclic diethylenetriamine-N,N’,N’,N’’, N’’-pentaacetic acid (1B4M-DTPA) and macrocyclic 1,4,7,10-tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid (C-DOTA). The metal-ligand chelates were pre-formed in alcohol prior to conjugation to the generation 4 PAMAM dendrimer (G4D), and the dendrimer-based agents were purified by Sephadex® G-25 column. The analysis and SE-HPLC data indicated chelate to dendrimer ratios of 30:1 and 28:1 respectively. Molar relaxivity measured at pH 7.4, 22°C, and 3T are comparable (29.5 vs. 26.9 mM−1s−1), and both conjugates are equally viable as MRI contrast agents based on the images obtained. The macrocyclic agent however exhibits a faster rate of clearance in vivo (t1/2 = 16 vs. 29 min.). Our conclusion is that the macrocyclic-based agent is the more suitable agent for in vivo use for these reasons combined with kinetic inertness associated with the Gd(III) DOTA complex stability properties. PMID:20663676

  11. The solution structure of stilbenoid dendrimers: a small-angle scattering study.

    Science.gov (United States)

    Rosenfeldt, Sabine; Karpuk, Elena; Lehmann, Matthias; Meier, Herbert; Lindner, Peter; Harnau, Ludger; Ballauff, Matthias

    2006-10-13

    The spatial structure of a stilbenoid dendrimer is investigated by small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) in dilute solution. All measurements are performed in toluene. The dendrimer consists of a stilbenoid scaffold with appended hexyloxy chains. SAXS is mainly sensitive to the dendrimer scaffold whereas SANS intensity, measured in fully deuterated toluene, derives from the solute molecules. The resulting SAXS and SANS intensities are analyzed by comparison with various models. It is found that the model of a circular disk gives the best description of the data. SAXS data demonstrate that the stilbenoid scaffold is flat as expected for benzene rings conjugated through vinylene units. Thus, it can be described by a circular disk with a radius of 1.6 nm and a thickness of 0.7 nm. SANS, on the other hand, shows that the hexyloxy chains are not confined in the plane defined by the core. This is derived from modeling the SANS data with a much thicker circular disk (radius: 2.4 nm, thickness: 1.8 nm). The structure factor S(q), describing the interaction of the dendrimers at higher concentrations, is modeled quantitatively with the "polymer reference interaction site model" (PRISM) integral equation formalism for hard plates such as particles. Here the structural data obtained from the analysis of the SANS data are used so that no new adjustable parameter is necessary for this description.

  12. Nanomechanical properties of hydroxyapatite (HAP) with DAB dendrimers (poly-propylene imine) coatings onto titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Charitidis, Costas A., E-mail: charitidis@chemeng.ntua.gr [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou, Zografou, 15780 Athens (Greece); Skarmoutsou, Amalia [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechniou, Zografou, 15780 Athens (Greece); Tsetsekou, Athena; Brasinika, Despina [School of Mining Engineering and Metallurgy, National Technical University of Athens, Iroon Polytechniou, Zografou, 15780 Athens (Greece); Tsiourvas, Dimitris [National Centre for Scientific Research “Demokritos”, Institute of Physical Chemistry, Agia Paraskevi, 15310 Athens (Greece)

    2013-04-20

    Highlights: ► The synthesis of hydroxyapatite (HAP) nanoparticles in the presence of a cationic fourth generation diaminobutane poly(propylene imine) dendrimer (DAB). ► The nanomechanical properties of different HAP-DAB coatings onto titanium surfaces. ► Wear resistance and adhesion properties of the synthesized coatings quantified by nanoindentation data analysis. -- Abstract: Coatings of hydroxyapatite (HAP) nanorods onto titanium surfaces were synthesized with the aim to improve coatings’ mechanical properties and adhesion to the substrate. The coatings are consisting of HAP nanorods synthesized in the presence of a cationic fourth generation diaminobutane poly(propylene imine) dendrimer (DAB) bearing 32 amine end groups employing varying calcium: dendrimer ratios and varying hydrothermal treatments. The quality, surface morphology and structure of the coatings were characterized with X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy dispersive microanalysis. Wear resistance and adhesion properties of the coatings onto titanium substrates were studied through nanoindentation analysis. The experimental conditions, namely the calcium: dendrimer molar ratio and the hydrothermal treatment temperature were carefully selected; thus, it was possible to produce coatings of high hardness and elastic modulus values (ranging between 1–4.5 GPa and 40–150 GPa, respectively) and/or high wear resistance and plastic deformation values.

  13. Click Co sandwich-terminated dendrimers as polyhydride reservoirs and micellar templates.

    Science.gov (United States)

    Rapakousiou, Amalia; Belin, Colette; Salmon, Lionel; Ruiz, Jaime; Astruc, Didier

    2017-06-06

    Neutral click metallodendrimers with [Co(I)(η(4)-cyclopentadiene)(η(5)-cyclopentadienyl)] termini are synthesized by reduction of dendrimers with 9, 27 or 81 cobalticenium termini and serve as polyhydride reservoirs and reductants; for instance, they reduce proton sources to H2 and Au(III) to micellized capsules of gold nanoparticles.

  14. A simple new competition assay for heparin binding in serum applied to multivalent PAMAM dendrimers.

    Science.gov (United States)

    Bromfield, Stephen M; Posocco, Paola; Fermeglia, Maurizio; Pricl, Sabrina; Rodríguez-López, Julián; Smith, David K

    2013-05-25

    We report a competition assay using our recently reported dye Mallard Blue, which allows us to identify synthetic heparin binders in competitive media, including human serum - using this we gain insight into the ability of PAMAM dendrimers to bind heparin, with the interesting result that low-generation G2-PAMAM is the preferred heparin binder.

  15. Preparation of metal-SAM-dendrimer-SAM-metal junctions by supramolecular metal transfer printing

    NARCIS (Netherlands)

    Nijhuis, Christian A.; ter Maat, Jurjen; Bisri, Satria Z.; Weusthof, Marcel H. H.; Salm, Cora; Schmitz, Jurriaan; Ravoo, Bart Jan; Huskensa, Jurriaan; Reinhoudt, David N.

    2008-01-01

    Metal-self-assembled monolayer (SAM)-dendrimer-SAM-metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple beta-cyclodextrin (beta CD) host-guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is fu

  16. Preparation of metal-SAM-dendrimer-SAM-metal junctions by supramolecular metal transfer printing

    NARCIS (Netherlands)

    Nijhuis, Christian A.; Maat, ter Jurjen; Bisri, Satria Z.; Weusthof, Marcel H.H.; Salm, Cora; Schmitz, Jurriaan; Ravoo, Bart Jan; Huskens, Jurriaan; Reinhoudt, David N.

    2008-01-01

    Metal-self-assembled monolayer (SAM)-dendrimer-SAM-metal junctions were prepared by a new type of metal transfer printing (mTP) that uses multiple ß-cyclodextrin (ßCD) host-guest interactions between a metal-coated stamp decorated with a monolayer of host molecules and a substrate which is functiona

  17. Effects of solute-solute interactions on protein stability studied using various counterions and dendrimers.

    Directory of Open Access Journals (Sweden)

    Curtiss P Schneider

    Full Text Available Much work has been performed on understanding the effects of additives on protein thermodynamics and degradation kinetics, in particular addressing the Hofmeister series and other broad empirical phenomena. Little attention, however, has been paid to the effect of additive-additive interactions on proteins. Our group and others have recently shown that such interactions can actually govern protein events, such as aggregation. Here we use dendrimers, which have the advantage that both size and surface chemical groups can be changed and therein studied independently. Dendrimers are a relatively new and broad class of materials which have been demonstrated useful in biological and therapeutic applications, such as drug delivery, perturbing amyloid formation, etc. Guanidinium modified dendrimers pose an interesting case given that guanidinium can form multiple attractive hydrogen bonds with either a protein surface or other components in solution, such as hydrogen bond accepting counterions. Here we present a study which shows that the behavior of such macromolecule species (modified PAMAM dendrimers is governed by intra-solvent interactions. Attractive guanidinium-anion interactions seem to cause clustering in solution, which inhibits cooperative binding to the protein surface but at the same time, significantly suppresses nonnative aggregation.

  18. Amine functionalization of cholecyst-derived extracellular matrix with generation 1 PAMAM dendrimer.

    LENUS (Irish Health Repository)

    Chan, Jeffrey C Y

    2008-02-01

    A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N\\'-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype.

  19. Multifunctional dendrimer/combretastatin A4 inclusion complexes enable in vitro targeted cancer therapy

    Directory of Open Access Journals (Sweden)

    Zhang M

    2011-10-01

    Full Text Available Mengen Zhang1,2, Rui Guo2, Yin Wang2, Xueyan Cao2, Mingwu Shen2, Xiangyang Shi1-31State Key Laboratory for Modification of Chemical Fibers and Polymer Materials; 2College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, People’s Republic of China; 3Centro de Química da Madeira, Universidade da Madeira, Campus da Penteada, Funchal, PortugalBackground: We report here a unique approach to using multifunctional dendrimer/combretastatin A4 (CA4 inclusion complexes for targeted cancer therapeutics.Methods: Amine-terminated generation 5 polyamidoamine dendrimers were first partially acetylated to neutralize a significant portion of the terminal amines, and then the remaining dendrimer terminal amines were sequentially modified with fluorescein isothiocyanate as an imaging agent and folic acid as a targeting ligand. The multifunctional dendrimers formed (G5.NHAc-FI-FA were utilized to encapsulate the anticancer drug, CA4, for targeted delivery into cancer cells overexpressing folic acid receptors.Results: The inclusion complexes of G5.NHAc-FI-FA/CA4 formed were stable and are able to significantly improve the water solubility of CA4 from 11.8 to 240 µg/mL. In vitro release studies showed that the multifunctional dendrimers complexed with CA4 could be released in a sustained manner. Both 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide colorimetric assay and morphological cell observation showed that the inhibitory effect of the G5.NHAc-FI-FA/CA4 complexes was similar to that of free CA4 at the same selected drug concentration. More importantly, the complexes were able to target selectively and display specific therapeutic efficacy to cancer cells overexpressing high-affinity folic acid receptors.Conclusion: Multifunctional dendrimers may serve as a valuable carrier to form stable inclusion complexes with various hydrophobic anticancer drugs with improved water solubility, for targeting chemotherapy to

  20. Nano polyamidoamine-G7 dendrimer synthesis and assessment the antibacterial effect in vitro

    Directory of Open Access Journals (Sweden)

    Mitra Gholami

    2016-04-01

    Full Text Available Background: Nano scale dendrimers are macromolecules synthetic which frequently used in medical and health field. Because traditional antibiotics inevitably induce bacterial resistance, which is responsible for many treatment failures, there is an urgent need to develop novel antibiotic drugs. This study was aimed to examine Synthesis and the antibacterial effect of NanoPolyamidoamine-G7 (NPAMAM-G7 dendrimer on Escherichia Coli, Proteus Mirabilis, Salmonella Typhi, Bacillus Subtilis and Staphylococcus Aureus. Methods: In this experimental study that has been conducted in June 2015 in the Laboratory of Microbiology, Iran University of Medical Science, NPAMAM-G7 dendrimers was synthesized by Tomalia’s divergent growth approach. The antibacterial effects of NPAMAM-G7 dendrimer were studied by disc diffusion and micro-dilution method. Minimum inhibitory concentration (MIC and minimum bactericidal concentration (MBC against gram-positive and gram-negative bacteria were determined according to Clinical and Laboratory Standards Institute (CLSI guideline. Standard discs were prepared using different concentrations of dendrimer on Mueller-Hinton agar plates. Results: Zone of inhibition in concentration 25 μg/ml of NPAMAM-G7 dendrimers for Escherichia Coli, Proteus Mirabilis, Salmonella Typhi, Bacillus Subtilis and Staphylococcus Aureus were 26, 38, 36, 22 and 25 mm, respectively. Regarding the zone of inhibition in gram negative bacteria with gram positive ones was P= 0.16 and was not significant difference. The MIC for Salmonella Typhi was 0.025, for Proteus Mirabilis, Bacillus Subtilis, Staphylococcus Aureus and Escherichia Coli was 0.25 μg/ml. The MBC for Salmonella Typhi was 25μg/ml, for Proteus Mirabilis and Bacillus Subtilis was 50 μg/ml and for Escherichia Coli and Staphylococcus Aureus was 100 μg/ml. The least of sensitivity against NPAMAM-G7 related to Escherichia Coli and Staphylococcus Aureus and the most of sensitivity related to

  1. Anionic linear-globular dendrimers: biocompatible hybrid materials with potential uses in nanomedicine.

    Science.gov (United States)

    Alavidjeh, Mohammad Shafiee; Haririan, Ismaeil; Khorramizadeh, Mohammad Reza; Ghane, Zohre Zarei; Ardestani, Mehdi Shafiee; Namazi, Hassan

    2010-04-01

    The use of dendrimers as nano-sized excipients/vectors in biological and pharmaceutical systems is dependent on the investigation of their toxicological profiles in biological media. In this study, a series of mechanistic in vitro structure-associated cell toxicity evaluations was performed on the two generations of an anionic linear-globular dendrimer G1 and G2 (where PEG is the core, and citric acid is the periphery) each of which has a different size, charge, and MW. In vitro cytotoxicity behavior of the dendrimers with the methods like crystal violet staining, methyl thiazolyl tetrazolium (MTT), and lactate dehydrogenase (LDH) assays was analyzed. The cell death mechanisms (apoptosis-necrosis) induced by the dendrimers were also evaluated in HT1080 cell line. The impact of the dendrimers on the release of the pro-inflammatory cytokines like TNF-alpha (tumor necrosis factor alpha) and IL1-beta (interleukin 1 beta) was assessed in THP-1 cell line. Hemolysis assay and coagulation studies such as PT (prothrombin time) and APTT (activated partial thromboplastin time) on human blood samples were conducted to examine the interactions of the dendrimers with such bio-environments. The results of cell cytotoxicity experiments and the amounts of IL1-beta and TNF-alpha secretions from THP-1 cell line were consistent with the hemoglobin release from the erythrocytes and the results gained from the coagulation studies. In fact, no significant harmful effect was observed for the dendrimers up to the concentration of 0.5 mg/ml. Both apoptosis and necrosis were ascribed to cell death. The G1 with more flexibility, less negative charge, and greater poly dispersity in size versus the G2 displayed more toxicity than the G2 at the concentration of 1 mg/ml and above in most of the experiments. As a whole, these results suggest a biocompatible range for these hybrid structures up to the concentration of 0.5 mg/ml. Therefore, the potentiality for these structures to be employed in the

  2. Oegylated and cross-linking carbazole dendrons and dendrimers: Synthesis, characterization, assembly and thin film fabrication

    Science.gov (United States)

    Felipe, Mary Jane Legaspi

    2011-12-01

    Dendrimers and dendrons (fractional dendrimers) are macromolecular structures that have well-defined molecular weights and precise number of functional groups. Tailoring these structures has provided designer molecules that can be used for various applications including drug delivery, sensors, and anti-biofouling surfaces. Overall, this dissertation provides novel protocols for the understanding of molecular design, synthesis, and structure-property relationship of OEGylated and conjugated carbazole dendrons and dendrimers. In this design, the use of oligo(ethylene glycol) (OEG) allows for the fabrication of biocompatible materials and imparts hydrophilicity on the structure while the carbazole functionality allows the cross-linking of these designer molecules. Such fine-tuning of macromolecular structures leading to the fabrication of anti-biofouling thin films, nanostructuring at the air-water interface, and assembly into supramolecular superstructures are considered in this dissertation. Chapter 2 details the synthesis, characterization, and electrochemical cross-linking of OEGylated linear dendrons and "Janus-type" dendrimers. Cross-linking the carbazole moieties enables the deposition of these films on Au, indium tin oxide-coated glass, and doped silicon through cyclic voltammetry and provides films with secondary level of organization imparted by the inter- and intra-molecular interaction among the carbazole units. Chapter 3 describes the fabrication of nonspecific protein adsorption resistant surfaces through electrochemical grafting of three different dendrons on SAM carbazole-coated gold substrates. The predictable shape of each dendron and the ability to cross-link the carbazole units have enabled parametrization of OEG conformation and density on these interfaces. Chapter 4 demonstrates the fundamental architectural requirements for obtaining stable films with OEGylated linear dendron molecules providing a new architectural design of nanostructuring

  3. Interaction of size-selected gold nanoclusters with dopamine

    Science.gov (United States)

    Montone, Georgia R.; Hermann, Eric; Kandalam, Anil K.

    2016-12-01

    We present density functional theory based results on the interaction of size-selected gold nanoclusters, Au10 and Au20, with dopamine molecule. The gold clusters interact strongly with the nitrogen site of dopamine, thereby forming stable gold-dopamine complexes. Our calculations further show that there is no site specificity on the planar Au10 cluster with all the edge gold atoms equally preferred. On the other hand, in the pyramidal Au20 cluster, the vertex metal atom is the most active site. As the size increased from Au10 to Au20, the interaction strength has shown a declining trend. The effect of aqueous environment on the interaction strengths were also studied by solvation model. It is found that the presence of solvent water stabilizes the interaction between the metal cluster and dopamine molecule, even though for Au10 cluster the energy ordering of the isomers changed from that of the gas-phase.

  4. Simultaneous expression and transportation of insulin by supramolecular polysaccharide nanocluster

    Science.gov (United States)

    Zhang, Yu-Hui; Zhang, Ying-Ming; Zhao, Qi-Hui; Liu, Yu

    2016-01-01

    Drug/gene transportation systems with stimuli-responsive release behaviors are becoming research hotspots in biochemical and biomedical fields. In this work, a glucose-responsive supramolecular nanocluster was successfully constructed by the intermolecular complexation of phenylboronic acid modified β-cyclodextrin with adamantane modified polyethylenimine, which could be used as a biocompatible carrier for insulin and pCMV3-C-GFPSpark-Ins DNA which could express insulin co-delivery. Benefiting from the response capability of phenylboronic acid moiety toward glucose, the encapsulated insulin could be specifically released and the corresponding targeted DNA could efficiently express insulin in HepG2 cell, accompanied by the high-level insulin release in vitro. Our results demonstrate that the simultaneous insulin drug delivery and insulin gene transfection in a controlled mode may have great potential in the clinical diabetes treatments. PMID:26948978

  5. Cytotoxicity of nucleus-targeting fluorescent gold nanoclusters

    Science.gov (United States)

    Zhao, Jing-Ya; Cui, Ran; Zhang, Zhi-Ling; Zhang, Mingxi; Xie, Zhi-Xiong; Pang, Dai-Wen

    2014-10-01

    Gold nanoclusters (AuNCs) with ultra small sizes and unique fluorescence properties have shown promising potential for imaging the nuclei of living cells. However, little is known regarding the potential cytotoxicity of AuNCs after they enter the cell nucleus. The aim of this study is to investigate whether and how nucleus-targeting AuNCs affect the normal functioning of cells. Highly stable, water-soluble and bright fluorescent Au25NCs (the core of each nanocluster is composed of 25 gold atoms) were synthesized. Specific targeting of Au25NCs to the cell nucleus was achieved by conjugating the TAT peptide to the Au25NCs. Cell viability, cell morphology, cell apoptosis/necrosis, reactive oxygen species (ROS) level and mitochondrial membrane potential examinations were performed on different cell lines exposed to the nucleus-targeting Au25NCs. We found that the nucleus-targeting Au25NCs caused cell apoptosis in a dose-dependent manner. A possible mechanism for the cytotoxicity of the nucleus-targeting Au25NCs was proposed as follows: the nucleus-targeting Au25NCs induce the production of ROS, resulting in the oxidative degradation of mitochondrial components, in turn leading to apoptosis via a mitochondrial damage pathway. This work facilitates a better understanding of the toxicity of AuNCs, especially nucleus-targeting AuNCs.Gold nanoclusters (AuNCs) with ultra small sizes and unique fluorescence properties have shown promising potential for imaging the nuclei of living cells. However, little is known regarding the potential cytotoxicity of AuNCs after they enter the cell nucleus. The aim of this study is to investigate whether and how nucleus-targeting AuNCs affect the normal functioning of cells. Highly stable, water-soluble and bright fluorescent Au25NCs (the core of each nanocluster is composed of 25 gold atoms) were synthesized. Specific targeting of Au25NCs to the cell nucleus was achieved by conjugating the TAT peptide to the Au25NCs. Cell viability, cell

  6. Thumb Imprint Based Detection of Hyperbilirubinemia Using Luminescent Gold Nanoclusters

    Science.gov (United States)

    Basu, Srestha; Sahoo, Amaresh Kumar; Paul, Anumita; Chattopadhyay, Arun

    2016-12-01

    Early and easy detection of diseases, using point-of-care and inexpensive devices, not only provides option for early treatment but also reduces the risk of propagation. Herein we report the fabrication of a robust film based luminescence indicator of bilirubin, which can indicate hyperbilirubinemia through the thumb imprint of the patient. The UV-light induced luminescence intensity of the film, made out of chitosan stabilised gold (Au) nanoclusters, which was effectively quenched in the presence of Cu2+ ions, recovered in the presence of bilirubin from skin or blood serum. Moreover, the sensitivity of detection of bilirubin was tuneable with the amount of Cu2+ added, thereby facilitating the detection of the desired concentration range of bilirubin.

  7. Simultaneous expression and transportation of insulin by supramolecular polysaccharide nanocluster

    Science.gov (United States)

    Zhang, Yu-Hui; Zhang, Ying-Ming; Zhao, Qi-Hui; Liu, Yu

    2016-03-01

    Drug/gene transportation systems with stimuli-responsive release behaviors are becoming research hotspots in biochemical and biomedical fields. In this work, a glucose-responsive supramolecular nanocluster was successfully constructed by the intermolecular complexation of phenylboronic acid modified β-cyclodextrin with adamantane modified polyethylenimine, which could be used as a biocompatible carrier for insulin and pCMV3-C-GFPSpark-Ins DNA which could express insulin co-delivery. Benefiting from the response capability of phenylboronic acid moiety toward glucose, the encapsulated insulin could be specifically released and the corresponding targeted DNA could efficiently express insulin in HepG2 cell, accompanied by the high-level insulin release in vitro. Our results demonstrate that the simultaneous insulin drug delivery and insulin gene transfection in a controlled mode may have great potential in the clinical diabetes treatments.

  8. A comparison of interatomic potentials for modeling tungsten nanocluster structures

    Science.gov (United States)

    Hao, Jiannan; Shu, Xiaolin; Jin, Shuo; Zhang, Xuesong; Zhang, Ying; Lu, Guang-Hong

    2017-02-01

    Molecular dynamic simulation is utilized to study the nanocluster and the fuzz structure on the PFM surface of tungsten. The polyhedral and linear cluster structures based on the icosahedron, cuboctahedron and rhombic dodecahedron are built up. Three interatomic potentials are used in calculating the relationship between the cluster energy and the number of atoms. The results are compared with first-principles calculation to show each potential's best application scale. Furthermore, the transition between the icosahedral and the cuboctahedral clusters is observed in molecular dynamic simulation at different temperatures, which follows a critical curve for different numbers of atoms. The linear structures are proved to be stable at experimental temperatures by thermodynamics. The work presents a selection of interatomic potentials in simulating tungsten cluster systems and helps researchers understand the growth and evolution laws of clusters and the fuzz-like structure formation process in fusion devices.

  9. Efficient Radioisotope Energy Transfer by Gold Nanoclusters for Molecular Imaging.

    Science.gov (United States)

    Volotskova, Olga; Sun, Conroy; Stafford, Jason H; Koh, Ai Leen; Ma, Xiaowei; Cheng, Zhen; Cui, Bianxiao; Pratx, Guillem; Xing, Lei

    2015-08-26

    Beta-emitting isotopes Fluorine-18 and Yttrium-90 are tested for their potential to stimulate gold nanoclusters conjugated with blood serum proteins (AuNCs). AuNCs excited by either medical radioisotope are found to be highly effective ionizing radiation energy transfer mediators, suitable for in vivo optical imaging. AuNCs synthesized with protein templates convert beta-decaying radioisotope energy into tissue-penetrating optical signals between 620 and 800 nm. Optical signals are not detected from AuNCs incubated with Technetium-99m, a pure gamma emitter that is used as a control. Optical emission from AuNCs is not proportional to Cerenkov radiation, indicating that the energy transfer between the radionuclide and AuNC is only partially mediated by Cerenkov photons. A direct Coulombic interaction is proposed as a novel and significant mechanism of energy transfer between decaying radionuclides and AuNCs.

  10. Jump electroconductivity in the laser deposited nanoclustered structures

    Science.gov (United States)

    Antipov, A.; Shagurina, A.; Osipov, A.; Istratov, A.; Skryabin, I.; Arakelian, S.

    2017-01-01

    The quantum states verification in cluster semiconductor/metallic structures by jump/tunneling electroconductivity and possible mechanisms for their implementation are considered in experiment and theory. By our laser ablation technique we have nanostructurized the films for which the ability to control the change in their electrical properties does exist by variation of the topology for the system. The granular conductivity specificity has been under study. The current-voltage characteristics behavior has been measured for a nanocluster bimetallic film (Au+Ag), and the experiments for multilayer bimetal thin films of the different composition have been carried out. Two associated mechanisms for electroconductivity occur in the case, i.e. tunnel transition for electrons and electron activation in the frames of the shell model for a cluster system, in dependence on the nanostructure topology.

  11. Dendrimer-mediated synthesis of platinum nanoparticles: new insights from dialysis and atomic force microscopy measurements

    Science.gov (United States)

    Xie, Hong; Gu, Yunlong; Ploehn, Harry J.

    2005-07-01

    In this work, we use AFM measurements in conjunction with dialysis experiments to study the synthesis mechanism and physical state of dendrimer-stabilized platinum nanoparticles. For characterizing particle size distributions by high resolution transmission electron microscopy and AFM, sample preparation by drop evaporation presumably minimizes the risk of sample bias that might be found in spin coating or dip-and-rinse methods. However, residual synthesis by-products (mainly salts) must be removed from solutions of dendrimer-stabilized metal nanoparticles prior to AFM imaging. Purification by dialysis is effective for this purpose. We discovered, by UV-visible spectrophotometry and atomic absorption (AA) spectroscopy, that dialysis using 'regular' cellulose dialysis tubing (12 000 Da cut-off) used in all previous work leads to substantial losses of poly(amidoamine) (PAMAM) dendrimer (G4OH), PAMAM-Pt(+2) complex, and PAMAM-stabilized Pt nanoparticles. Use of benzoylated dialysis tubing (1200 Da cut-off) shows no losses of G4OH or G4OH-Pt mixtures. We use AFM to see whether selective filtration during dialysis introduces sampling bias in the measurement of particle size distributions. We compare results (UV-visible spectra, AA results, and AFM-based particle size distributions) for a sample of G4OH-Pt40 divided into two parts, one part dialysed with regular dialysis tubing and the other with benzoylated tubing. Exhaustive dialysis using benzoylated tubing may lead to the loss of colloidal Pt nanoparticles stabilized by adsorbed dendrimer, but not Pt nanoparticles encapsulated by the dendrimer. The comparisons also lead to new insights concerning the underlying synthesis mechanisms for PAMAM-stabilized Pt nanoparticles.

  12. Information processing schemes based on monolayer protected metallic nanoclusters.

    Science.gov (United States)

    Cervera, Javier; Mafé, Salvador

    2011-09-01

    Nanostructures are potentially useful as building blocks to complement future electronics because of their high versatility and packing densities. The fabrication and characterization of particular nanostructures and the use of new theoretical tools to describe their properties are receiving much attention. However, the integration of these individual systems into general schemes that could perform simple tasks is also necessary because modern electronics operation relies on the concerted action of many basic units. We review here new conceptual schemes that can allow information processing with ligand or monolayer protected metallic nanoclusters (MPCs) on the basis of the experimentally demonstrated and theoretically described electrical characteristics of these nanostructures. In particular, we make use of the tunnelling current through a metallic nanocluster attached to the electrodes by ligands. The nanostructure is described as a single electron transistor (SET) that can be gated by an external potential. This fact permits exploiting information processing schemes in approximately defined arrays of MPCs. These schemes include: (i) binary, multivalued, and reversible logic gates; (ii) an associative memory and a synchronization circuit; and (iii) two signal processing nanodevices based on parallel arrays of MPCs and nanoswitches. In each case, the practical operation of the nanodevice is based on the SET properties of MPCs reported experimentally. We examine also some of the practical problems that should be addressed in future experimental realizations: the stochastic nature of the electron tunnelling, the relatively low operation temperatures, and the limited reliability caused by the weak signals involved and the nanostructure variability. The perspectives to solve these problems are based on the potentially high degree of scalability of the nanostructures.

  13. Evaluation of Nanocarrier Targeted Drug Delivery of Capecitabine-PAMAM Dendrimer Complex in a Mice Colorectal Cancer Model

    Directory of Open Access Journals (Sweden)

    Fatemeh Nabavizadeh

    2016-09-01

    Full Text Available Capecitabine, an effective anticancer drug in colorectal cancer chemotherapy, may create adverse side effects on healthy tissues. In the present study, we first induced colon adenocarcinoma with azoxymethane, a carcinogen agent, and then investigated the potentiality of polyamidoamine (PAMAM dendrimer to improve capecitabine therapeutic index and decrease its adverse side effects on healthy tissues like liver and bone marrow. Other variables such as nanoparticle concentrations have also been investigated. Drug loading concentration (DLC and encapsulation efficiency (EE were calculated for capecitabine/dendrimer complex. Experimental results showed an increase in DLC percentage resulted from elevated capecitabine/dendrimer ratio. Capecitabine/dendrimer complex could reduce tumor size and adverse side effects in comparison with free capecitabine form.

  14. Small Angle Neutron Scattering Study on Structure of PAMAM Dendrimer Encapsulation With Small Molecules in Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Dendrimers have very unique structural and physicochemical properties and many potential important applications, such as drug delivery, and therefore have been attracting research interests. It is interesting and important to investigate the interaction of

  15. Development and validation of a reversed-phase high-performance liquid chromatographic method for quantification of peptide dendrimers in human skin permeation experiments.

    Science.gov (United States)

    Mutalik, S; Hewavitharana, A K; Shaw, P N; Anissimov, Y G; Roberts, M S; Parekh, H S

    2009-11-01

    The aim of the present work was to develop and validate a simple RP-HPLC method with UV detection to quantify peptide dendrimers in skin permeation experiments. Six dendrimers of varying positive charges (4(+), 8(+) and 16(+)) containing either histidine or arginine as terminal aminoacids were prepared by solid phase peptide synthesis. Mobile phase containing 0.02% (v/v) heptafluorobutyric acid in 90% acetonitrile-water was capable of separating all dendrimers from interfering peaks of receptor fluid. For the calibration of each dendrimer, a different dendrimer from the same class was selected as the internal standard. The results of preliminary human skin permeation studies showed that the developed analytical method can be successfully used for the quantification of cationic poly(aminoacid)-based dendrimers in skin permeation experiments.

  16. Nanocluster model of intermetallic compounds with giant unit cells: beta, beta'-Mg(2)Al(3) polymorphs.

    Science.gov (United States)

    Blatov, Vladislav A; Ilyushin, Gregory D; Proserpio, Davide M

    2010-02-15

    A novel method for the computational description of intermetallics as an assembly of nanoclusters was improved and applied to extremely complicated crystal structures of beta, beta'-Mg(2)Al(3) polymorphs. Using the TOPOS program package that implements the method, we separated two types of two-shell primary nanoclusters A, A1, A2, and B consisting of 57-63 atoms that completely compose the structures of the polymorphs. The nanocluster model interprets structural disordering in beta-Mg(2)Al(3): the disordered atoms form the inner shell of the nanocluster A, while the outer shells of all nanoclusters are preserved. The self-assembly of the beta, beta'-Mg(2)Al(3) crystal structures was considered within the hierarchical scheme: 0D primary polyhedral clusters (coordination polyhedra) --> 0D two-shell primary nanoclusters A, A1, A2, or B --> 0D supracluster-precursor AB(2) --> 1D primary chain --> 2D microlayer --> 3D microframework. The self-assembly scheme proves the similarity of beta, beta'-Mg(2)Al(3) to other extremely complicated Samson's phases, NaCd(2) and ZrZn(22); the spatial arrangement of the centers of nanoclusters in these structures as well as the topology of the corresponding network conform to the Laves phase MgCu(2). Using the TOPOS procedure of searching for finite fragments in infinite nets we found that nanocluster B is a typical fragment of intermetallic compounds: it exists in intermetallics belonging to 42 Pearson classes. The nanocluster A was found only in two Pearson classes: cF464 and hP238, while the nanoclusters A1 and A2 occur in beta'-Mg(2)Al(3) only. Thus, the nanoclusters A, A1, and A2 can be considered as "determinants" of the corresponding structures.

  17. Urea and thiourea modified polypropyleneimine dendrimers clear intracellular α-synuclein aggregates in a human cell line

    DEFF Research Database (Denmark)

    Laumann, Kristoffer; Boas, Ulrik; Larsen, Hjalte Martin;

    2015-01-01

    Synucleinopathies are neurodegenerative pathologies in which disease progression is closely correlated to brain accumulation of insoluble α-synuclein, a small protein abundantly expressed in neural tissue. Here, two types of modified polypropyleneimine (PPI) dendrimers having either urea or methy......Synucleinopathies are neurodegenerative pathologies in which disease progression is closely correlated to brain accumulation of insoluble α-synuclein, a small protein abundantly expressed in neural tissue. Here, two types of modified polypropyleneimine (PPI) dendrimers having either urea...

  18. A scalable synthesis of highly stable and water dispersible Ag 44(SR)30 nanoclusters

    KAUST Repository

    AbdulHalim, Lina G.

    2013-01-01

    We report the synthesis of atomically monodisperse thiol-protected silver nanoclusters [Ag44(SR)30] m, (SR = 5-mercapto-2-nitrobenzoic acid) in which the product nanocluster is highly stable in contrast to previous preparation methods. The method is one-pot, scalable, and produces nanoclusters that are stable in aqueous solution for at least 9 months at room temperature under ambient conditions, with very little degradation to their unique UV-Vis optical absorption spectrum. The composition, size, and monodispersity were determined by electrospray ionization mass spectrometry and analytical ultracentrifugation. The produced nanoclusters are likely to be in a superatom charge-state of m = 4-, due to the fact that their optical absorption spectrum shares most of the unique features of the intense and broadly absorbing nanoparticles identified as [Ag44(SR) 30]4- by Harkness et al. (Nanoscale, 2012, 4, 4269). A protocol to transfer the nanoclusters to organic solvents is also described. Using the disperse nanoclusters in organic media, we fabricated solid-state films of [Ag44(SR)30]m that retained all the distinct features of the optical absorption spectrum of the nanoclusters in solution. The films were studied by X-ray diffraction and photoelectron spectroscopy in order to investigate their crystallinity, atomic composition and valence band structure. The stability, scalability, and the film fabrication method demonstrated in this work pave the way towards the crystallization of [Ag44(SR)30]m and its full structural determination by single crystal X-ray diffraction. Moreover, due to their unique and attractive optical properties with multiple optical transitions, we anticipate these clusters to find practical applications in light-harvesting, such as photovoltaics and photocatalysis, which have been hindered so far by the instability of previous generations of the cluster. © 2013 The Royal Society of Chemistry.

  19. Electrical transport properties in Fe-Cr nanocluster-assembled granular films

    Science.gov (United States)

    Wang, Xiong-Zhi; Wang, Lai-Sen; Zhang, Qin-Fu; Liu, Xiang; Xie, Jia; Su, A.-Mei; Zheng, Hong-Fei; Peng, Dong-Liang

    2017-09-01

    The Fe100-xCrx nanocluster-assembled granular films with Cr atomic fraction (x) ranging from 0 to 100 were fabricated by using a plasma-gas-condensation cluster deposition system. The TEM characterization revealed that the uniform Fe clusters were coated with a Cr layer to form a Fe-Cr core-shell structure. Then, the as-prepared Fe100-xCrx nanoclusters were randomly assembled into a granular film in vacuum environments with increasing the deposition time. Because of the competition between interfacial resistance and shunting effect of Cr layer, the room temperature resistivity of the Fe100-xCrx nanocluster-assembled granular films first increased and then decreased with increasing the Cr atomic fraction (x), and revealed a maximum of 2 × 104 μΩ cm at x = 26 at.%. The temperature-dependent longitudinal resistivity (ρxx), magnetoresistance (MR) effect and anomalous Hall effect (AHE) of these Fe100-xCrx nanocluster-assembled granular films were also studied systematically. As the x increased from 0 to 100, the ρxx of all samples firstly decreased and then increased with increasing the measuring temperature. The dependence of ρxx on temperature could be well addressed by a mechanism incorporated for the fluctuation-induced-tunneling (FIT) conduction process and temperature-dependent scattering effect. It was found that the anomalous Hall effect (AHE) had no legible scaling relation in Fe100-xCrx nanocluster-assembled granular films. However, after deducting the contribution of tunneling effect, the scaling relation was unambiguous. Additionally, the Fe100-xCrx nanocluster-assembled granular films revealed a small negative magnetoresistance (MR), which decreased with the increase of x. The detailed physical mechanism of the electrical transport properties in these Fe100-xCrx nanocluster-assembled granular films was also studied.

  20. Poly(amidoamine) dendrimers show carbonic anhydrase inhibitory activity against α-, β-, γ- and η-class enzymes.

    Science.gov (United States)

    Carta, Fabrizio; Osman, Sameh M; Vullo, Daniela; AlOthman, Zeid; Del Prete, Sonia; Capasso, Clemente; Supuran, Claudiu T

    2015-11-01

    Four generations of poly(amidoamine) (PAMAM) dendrimers incorporating benzenesulfonamide moieties were investigated as inhibitors of carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α-, β-, γ- and η-classes which are present in pathogenic bacteria, fungi or protozoa. The following bacterial, fungal and protozoan organisms were included in the study: Vibrio cholerae, Trypanosoma cruzi, Leishmania donovani chagasi, Porphyromonas gingivalis, Cryptococcus neoformans, Candida glabrata, and Plasmodium falciparum. The eight pathozymes present in these organisms were efficiently inhibited by the four generations PAMAM-sulfonamide dendrimers, but multivalency effects were highly variable among the different enzyme classes. The Vibrio enzyme VchCA was best inhibited by the G3 dendrimer incorporating 32 sulfamoyl moieties. The Trypanosoma enzyme TcCA on the other hand was best inhibited by the first generation dendrimer G0 (with 4 sulfamoyl groups), whereas for other enzymes the optimal inhibitory power was observed for the G1 or G2 dendrimers, with 8 and 16 sulfonamide functionalities. This study thus proves that the multivalency may be highly relevant for enzyme inhibition for some but not all CAs from pathogenic organisms. On the other hand, some dendrimers investigated here showed a better inhibitory power compared to acetazolamide for enzymes from widespread pathogens, such as the η-CA from Plasmodium falciparum. Overall, the main conclusion is that this class of molecules may lead to important developments in the field of anti-infective CA inhibitors.

  1. Atomic force microscopy probing of receptor-nanoparticle interactions for riboflavin receptor targeted gold-dendrimer nanocomposites.

    Science.gov (United States)

    Witte, Amanda B; Leistra, Abigail N; Wong, Pamela T; Bharathi, Sophia; Refior, Kevin; Smith, Phillip; Kaso, Ola; Sinniah, Kumar; Choi, Seok Ki

    2014-03-20

    Riboflavin receptors are overexpressed in malignant cells from certain human breast and prostate cancers, and they constitute a group of potential surface markers important for cancer targeted delivery of therapeutic agents and imaging molecules. Here we report on the fabrication and atomic force microscopy (AFM) characterization of a core-shell nanocomposite consisting of a gold nanoparticle (AuNP) coated with riboflavin receptor-targeting poly(amido amine) dendrimer. We designed this nanocomposite for potential applications such as a cancer targeted imaging material based on its surface plasmon resonance properties conferred by AuNP. We employed AFM as a technique for probing the binding interaction between the nanocomposite and riboflavin binding protein (RfBP) in solution. AFM enabled precise measurement of the AuNP height distribution before (13.5 nm) and after chemisorption of riboflavin-conjugated dendrimer (AuNP-dendrimer; 20.5 nm). Binding of RfBP to the AuNP-dendrimer caused a height increase to 26.7 nm, which decreased to 22.8 nm when coincubated with riboflavin as a competitive ligand, supporting interaction of AuNP-dendrimer and its target protein. In summary, physical determination of size distribution by AFM imaging can serve as a quantitative approach to monitor and characterize the nanoscale interaction between a dendrimer-covered AuNP and target protein molecules in vitro.

  2. Molecular dynamics simulation of spin-lattice NMR relaxation in poly-L-lysine dendrimers: manifestation of the semiflexibility effect.

    Science.gov (United States)

    Markelov, Denis A; Falkovich, Stanislav G; Neelov, Igor M; Ilyash, Maxim Yu; Matveev, Vladimir V; Lähderanta, Erkki; Ingman, Petri; Darinskii, Anatolii A

    2015-02-07

    NMR relaxation experiments are widely used to investigate the local orientation mobility in dendrimers. In particular, the NMR method allows one to measure the spin-lattice relaxation rate, 1/T1, which is connected with the orientational autocorrelation function (ACF) of NMR active groups. We calculate the temperature (Θ) and frequency (ω) dependences of the spin-lattice NMR relaxation rates for segments and NMR active CH2 groups in poly-L-lysine (PLL) dendrimers in water, on the basis of full-atomic molecular dynamics simulations. It is shown that the position of the maximum of 1/T1(ω) depends on the location of the segments inside the dendrimer. This dependence of the maximum is explained by the restricted flexibility of the dendrimer. Such behavior has been predicted recently by the analytical theory based on the semiflexible viscoelastic model. The simulated temperature dependences of 1/T1 for terminal and inner groups in PLL dendrimers of n = 2 and n = 4 generations dissolved in water are in good agreement with the NMR experimental data, which have been obtained for these systems previously by us. It is shown that in the case of PLL dendrimers, the traditional procedure of the interpretation of NMR experimental data - when smaller values of 1/T1 correspond to higher orientation mobility - is applicable to the whole accessible frequency interval only for the terminal groups. For the inner groups, this procedure is valid only at low frequencies.

  3. Synthesis of Novel Amphiphilic Poly (ester-amine) Dendrimers and Their Recognition of Hg2+ at the Air/Water Interface

    Institute of Scientific and Technical Information of China (English)

    申亮; 李富友; 沙耀武; 潘峥峥; 洪啸吟; 黄春辉

    2003-01-01

    Two novel amphiphilic poly(ester-amine)dendrimers were synthesized and characterized by 1H NMR,13C NMR and IR spectra.Their properties of Langmuir film were investigated at the air/water interface.The relationship between the surface pressure and area isotherms of the dendrimers was found to be dependent on the nature of subphases,Interaction between HgCl2 and the dendrimers was observed,indicating that the amphiphilic dendrimers could act as a sensor for Hg2+.

  4. Surface Hydrophobic Modification of Fifth-Generation Hydroxyl-Terminated Poly(amidoamine Dendrimers and Its Effect on Biocompatibility and Rheology

    Directory of Open Access Journals (Sweden)

    Paul D. Hamilton

    2009-08-01

    Full Text Available Water-soluble, commercially-available poly(amidoamine (PAMAM dendrimers are highly-branched, well-defined, monodisperse macromolecules having an ethylenediamine core and varying surface functional groups. Dendrimers are being employed in an increasing number of biomedical applications. In this study, commercially obtained generation 5 hydroxyl-terminated (G5OH PAMAM dendrimers were studied as potential proteomimetics for ophthalmic uses. To this end, the surface of G5OH PAMAM dendrimers were hydrophobically modified with varying amounts of dodecyl moieties, (flexible long aliphatic chains, or cholesteryl moieties (rigid lipid found in abundance in biological systems. Dendrimers were characterized by 1H-NMR, DLS, DSC and HPLC. The hydrophobic modification caused aggregation and molecular interactions between dendrimers that is absent in unmodified dendrimers. In vitro tissue culture showed that increasing the amount of dodecyl modification gave a proportional increase in toxicity of the dendrimers, while with increasing cholesteryl modification there was no corresponding increase in toxicity. Storage and loss modulus were measured for selected formulations. The hydrophobic modification caused an increase in loss modulus, while the effect on storage modulus was more complex. Rheological properties of the dendrimer solutions were comparable to those of porcine lens crystallins.

  5. Green synthesis of peptide-templated gold nanoclusters as novel fluorescence probes for detecting protein kinase activity.

    Science.gov (United States)

    Song, Wei; Liang, Ru-Ping; Wang, Ying; Zhang, Li; Qiu, Jian-Ding

    2015-06-21

    A green method was employed for synthesizing peptide-templated nanoclusters without requiring strong reducing agents. Using synthetic peptide-gold nanoclusters as fluorescence probes, a novel assay for detecting protein kinase is developed based on phosphorylation against carboxypeptidase Y digestion.

  6. Synthesis of biocompatible AuAgS/Ag{sub 2}S nanoclusters and their applications in photocatalysis and mercury detection

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Qian; Chen, Shenna; Zhang, Lingyang; Huang, Haowen, E-mail: hhwn09@163.com; Liu, Fengping [Hunan University of Science and Technology, Key Laboratory of Theoretical Organic Chemistry and Function Molecule, Ministry of Education, Hunan Provincial University Key Laboratory of QSAR/QSPR, School of Chemistry and Chemical Engineering (China); Liu, Xuanyong, E-mail: xyliu@mail.sic.ac.cn [Chinese Academy of Sciences, State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics (China)

    2014-12-15

    In this paper, a facile approach for preparation of AuAgS/Ag{sub 2}S nanoclusters was developed. The unique AuAgS/Ag{sub 2}S nanoclusters capped with biomolecules exhibit interesting excellent optical and catalytic properties. The fluorescent AuAgS/Ag{sub 2}S nanoclusters show tunable luminescence depending on the nanocluster size. The apoptosis assay demonstrated that the AuAgS/Ag{sub 2}S nanoclusters showed low cytotoxicity and good biocompatibility. Therefore, the nanoclusters can be used not only as a probe for labeling cells but also for their photocatalytic activity for photodegradation of organic dye. Moreover, a highly selective and sensitive assay for detection of mercury including Hg{sup 2+} and undissociated mercury complexes was developed based on the quenching fluorescent AuAgS/Ag{sub 2}S nanoclusters, which provides a promising approach for determining various forms of Hg in the mercury-based compounds in environment. These unique nanoclusters may have potential applications in biological labeling, sensing mercury, and photodegradation of various organic pollutants in waste water.Graphical Abstract.

  7. Synthesis of biocompatible AuAgS/Ag2S nanoclusters and their applications in photocatalysis and mercury detection

    Science.gov (United States)

    Zhao, Qian; Chen, Shenna; Zhang, Lingyang; Huang, Haowen; Liu, Fengping; Liu, Xuanyong

    2014-12-01

    In this paper, a facile approach for preparation of AuAgS/Ag2S nanoclusters was developed. The unique AuAgS/Ag2S nanoclusters capped with biomolecules exhibit interesting excellent optical and catalytic properties. The fluorescent AuAgS/Ag2S nanoclusters show tunable luminescence depending on the nanocluster size. The apoptosis assay demonstrated that the AuAgS/Ag2S nanoclusters showed low cytotoxicity and good biocompatibility. Therefore, the nanoclusters can be used not only as a probe for labeling cells but also for their photocatalytic activity for photodegradation of organic dye. Moreover, a highly selective and sensitive assay for detection of mercury including Hg2+ and undissociated mercury complexes was developed based on the quenching fluorescent AuAgS/Ag2S nanoclusters, which provides a promising approach for determining various forms of Hg in the mercury-based compounds in environment. These unique nanoclusters may have potential applications in biological labeling, sensing mercury, and photodegradation of various organic pollutants in waste water.

  8. Three-dimensional macroporous carbon/hierarchical Co3O4 nanoclusters for nonenzymatic electrochemical glucose sensor

    Science.gov (United States)

    Wang, Li; Zhang, Yayun; Xie, Yingzhen; Yu, Jie; Yang, Han; Miao, Longfei; Song, Yonghai

    2017-04-01

    A novel supporting material named as three-dimensional kenaf stem-derived carbon (3D-KSCs) was used to load hierarchical Co3O4 nanoclusters for electrochemical sensing glucose. The 3D-KSCs/hierarchical Co3O4 nanoclusters were constructed by two steps. Los of acicular precursor nanoclusters firstly grew on the channels of 3D-KSCs densely by hydrothermal method and then the as-prepared 3D-KSCs/hierarchical Co3O4 nanoclusters was obtained by thermal pyrolysis of the 3D-KSCs/precursors nanocomposites at 400 °C. The 3D macroporous configuration of 3D-KSCs resulted in lots of hierarchical Co3O4 nanoclusters arrayed on the surface of 3D-KSCs owing to its large enough specific surface area, which effectively avoided their aggregations and improved the stability of nanocomposites. The obtained 3D-KSCs/hierarchical Co3O4 nanoclusters showed a large number of needle-shaped and layered Co3O4 nanoclusters uniformly grew on the macropore's walls of 3D-KSC. Due to its unique nanostructures, the 3D-KSCs/hierarchical Co3O4 nanoclusters integrated electrode showed superior performance for nonenzymatic electrochemical glucose sensing, showing wide linear range (0.088-7.0 mM) and low detection limit of 26 μM. It might be a new strategy to prepare nanostructures on 3D-KSC for future applications.

  9. Controlled delivery of Gemcitabine Hydrochloride using mannosylated poly(propyleneimine) dendrimers

    Energy Technology Data Exchange (ETDEWEB)

    Soni, Namrata; Jain, Keerti, E-mail: keertijain02@gmail.com; Gupta, Umesh, E-mail: umeshgupta175@gmail.com; Jain, N. K., E-mail: jnarendr@yahoo.co.in [Dr. H. S. Gour Central University, Pharmaceutics Research Laboratory, Department of Pharmaceutical Sciences (India)

    2015-11-15

    The aim of the present investigation was to deliver Gemcitabine Hydrochloride (GmcH), an anticancer bioactive, specifically to lung tumor cells using mannosylated 4.0G poly(propyleneimine) dendrimers (M-PPI). 4.0G poly(propyleneimine) (PPI) dendrimers was synthesized using ethylenediamine as core and conjugated with mannose by ring opening reactions, followed by Schiff’s reaction in the presence of sodium acetate buffer (pH 4.0). Synthesized PPI dendrimers and mannose-conjugated dendrimers were characterized using IR, NMR spectroscopy, and scanning electron microscopy. GmcH was loaded into PPI and M-PPI dendrimers using equilibrium dialysis method to develop the formulations, GmcH-PPI and GmcH-M-PPI, respectively. The developed formulations were evaluated for drug loading, in vitro release kinetics, in vitro stability, hemolytic toxicity, cytotoxicity, pharmacokinetic, and biodistribution studies. The dendrimeric formulation of GmcH showed pH-sensitive release with faster release at acidic pH, i.e., pH 4.0 in comparison with physiological pH 7.4. M-PPI conjugate showed significant reduction in hemolytic toxicity as compared to plain 4.0G PPI dendrimers towards human erythrocytes. In the cytotoxicity studies with A-549 lung adenocarcinoma cell line, the GmcH-M-PPI formulation showed the lowest IC{sub 50} value. Further, the pharmacokinetic and tissue distribution studies of free drug GmcH, GmcH-PPI, and GmcH-M-PPI in albino rats of Sprague–Dawley strain suggested the mean residence time of GmcH-M-PPI conjugate to be significantly higher (24.85 h) than free GmcH and GmcH-PPI. Deposition of drug (396.1 ± 4.7 after 2 h) in lung was found to be significantly higher with GmcH-M-PPI formulation in comparison with Gmch and GmcH-PPI.

  10. Au Nanocluster assisted PCE improvement in PEDOT: PSS - Si Hybrid Devices

    Science.gov (United States)

    Sharma, Manisha; Pudasaini, Pushpa Raj; Ayon, Arturo A.

    2015-03-01

    Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), a P-type organic polymer is frequently employed in the fabrication of heterojunction p-n solar cell devices due to its proper HOMO-LUMO band gap as well as its tunable conductivity. In this report we describe the incorporation of gold (Au) nanoclusters in the PEDOT:PSS blend and its influence on the power-conversion-efficiency (PCE) on planar silicon (Si) hybrid heterojunction solar cell devices. Specifically, the reference samples without the aforementioned nanoclusters, were measured to exhibit a 6.10% PCE, value that increased to 7.55% upon the addition of the Au nanoclusters. The observed increase in the PCE is attributed to the enhanced electrical conductivity of the PEDOT:PSS films due to the incorporation of the nanoclusters, which is directly reflected in their improved fill factor. It is further theorized that the presence of Au nanoclusters in the insulating PSS layer in the PEDOT:PSS blend have a positive influence in the charge collection effectiveness of the devices produced. Considering that the Au nanoparticles involved in this research exercise had an average size of only 4 nm, it is considered that plasmonic effects did not play a relevant role in the observed PCE improvement.

  11. Highly fluorescent gold nanoclusters based sensor for the detection of quercetin

    Energy Technology Data Exchange (ETDEWEB)

    Chen Zhanguang, E-mail: kqlu@stu.edu.cn; Qian Sihua [Shantou University, Department of Chemistry (China); Chen Junhui, E-mail: chenjupush@126.com [Peking University Shenzhen Hospital, Interventional Oncology and Minimally Invasive Therapies Department (China); Chen Xi [Guangdong Pharmaceutical University (China)

    2012-12-15

    In this contribution, novel luminescent gold nanoclusters were synthesized by utilizing bovine serum albumin as templates with a simple, rapid, and one-pot procedure. The as-prepared gold nanoclusters were highly dispersed in aqueous solution and emitted an intense red fluorescence under UV light (365 nm). They exhibited strong fluorescence and the maximum excitation and emission wavelengths were 480 and 613.5 nm. In addition, the bovine serum albumin-stabilized gold nanoclusters were successfully utilized as novel fluorescent probes for the detection of quercetin for the first time. It was found that the addition of quercetin induced the strong fluorescence intensity of the gold nanoclusters to decrease. The decrease in fluorescence intensity of the gold nanoclusters caused by quercetin allowed the sensitive detection of quercetin in the range of 8.9 Multiplication-Sign 10{sup -8}-1.8 Multiplication-Sign 10{sup -4} mol L{sup -1}. The detection limit for quercetin is 1.8 Multiplication-Sign 10{sup -8} mol L{sup -1} at a signal-to-noise ratio of 3. The present sensor for quercetin detection possessed a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.

  12. Highly fluorescent gold nanoclusters based sensor for the detection of quercetin

    Science.gov (United States)

    Chen, Zhanguang; Qian, Sihua; Chen, Junhui; Chen, Xi

    2012-12-01

    In this contribution, novel luminescent gold nanoclusters were synthesized by utilizing bovine serum albumin as templates with a simple, rapid, and one-pot procedure. The as-prepared gold nanoclusters were highly dispersed in aqueous solution and emitted an intense red fluorescence under UV light (365 nm). They exhibited strong fluorescence and the maximum excitation and emission wavelengths were 480 and 613.5 nm. In addition, the bovine serum albumin-stabilized gold nanoclusters were successfully utilized as novel fluorescent probes for the detection of quercetin for the first time. It was found that the addition of quercetin induced the strong fluorescence intensity of the gold nanoclusters to decrease. The decrease in fluorescence intensity of the gold nanoclusters caused by quercetin allowed the sensitive detection of quercetin in the range of 8.9 × 10-8-1.8 × 10-4 mol L-1. The detection limit for quercetin is 1.8 × 10-8 mol L-1 at a signal-to-noise ratio of 3. The present sensor for quercetin detection possessed a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.

  13. Synthesis and Optical Properties of Au-Ag Alloy Nanoclusters with Controlled Composition

    Directory of Open Access Journals (Sweden)

    J. F. Sánchez-Ramírez

    2008-01-01

    Full Text Available Colloidal solid-solution-like Au-Ag alloy nanoclusters of different compositions were synthesized through citrate reduction of mixed metal ions of low concentrations, without using any other protective or capping agents. Optical absorption of the alloy nanoclusters was studied both theoretically and experimentally. The position of the surface plasmon resonance (SPR absorption band of the nanoclusters could be tuned from 419 nm to 521 nm through the variation of their composition. Considering effective dielectric constant of the alloy, optical absorption spectra for the nanoclusters were calculated using Mie theory, and compared with the experimentally obtained spectra. Theoretically obtained optical spectra well resembled the experimental spectra when the true size distribution of the nanoparticles was considered. High-resolution transmission electron microscopy (HREM, high-angle annular dark field (HAADF imaging, and energy dispersive spectroscopy (EDS revealed the true alloy nature of the nanoparticles with nominal composition being preserved. The synthesis technique can be extended to other bimetallic alloy nanoclusters containing Ag.

  14. Nanocrystals and Nanoclusters as Cocatalysts for Photocatalytic Water Splitting

    KAUST Repository

    Sinatra, Lutfan

    2016-12-04

    studied for the photocatalytic H2 production in order to explore the synergistic effect of the plasmonic resonance from the Au nanoparticles and pn-junction between Cu2O and TiO2. Additionally, the plasmonic effect of the Au films was also studied and utilized in order to improve the PWS. Secondly, the nanoscaling of cocatalysts was studied in order to improve the efficiency thereof and to reduce the cost of the cocatalyst materials. Moreover, it is sought to explore the quantum size effect on the properties of the cocatalyst and their effect on the photocatalytic reaction. Atomically precise Au and Ni nanoclusters were employed in these studies. Au nanoclusters were studied in relation to the cocatalysts in the photocatalytic water splitting, and Ni nanoclusters were studied in relation to the cocatalysts in the electrocatalytic water oxidation. The results of these studies will provide new insights in relation to the strategy used in order to develop efficient cocatalysts for the purpose of photocatalytic water splitting.

  15. Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins.

    Science.gov (United States)

    Rodríguez, Henry A; Giraldo, Luis F; Casanova, Herley

    2015-07-01

    The aim of this work was to study the effect of silica nanoclusters (SiNC), obtained by a solvent evaporation method and functionalized by 3-methacryloxypropyltrimethoxysilane (MPS) and MPS+octyltrimethoxysilane (OTMS) (50/50wt/wt), on the rheological, mechanical and sorption properties of urethane dimethylacrylate (UDMA)/triethylenglycol dimethacrylate (TEGDMA) (80/20wt/wt) resins blend. Silica nanoparticles (SiNP) were silanized with MPS or MPS+OTMS (50/50wt/wt) and incorporated in an UDMA-isopropanol mix to produce functionalized silica nanoclusters after evaporating the isopropanol. The effect of functionalized SiNC on resins rheological properties was determined by large and small deformation tests. Mechanical, thermal, sorption and solubility properties were evaluated for composite materials. The UDMA/TEGDMA (80/20wt/wt) resins blend with added SiNC (ca. 350nm) and functionalized with MPS showed a Newtonian flow behavior associated to their spheroidal shape, whereas the resins blend with nanoclusters silanized with MPS+OTMS (50/50wt/wt) (ca. 400nm) showed a shear-thinning behavior due to nanoclusters irregular shape. Composite materials prepared with bare silica nanoclusters showed lower compressive strength than functionalized silica nanoclusters. MPS functionalized nanoclusters showed better mechanical properties but higher water sorption than functionalized nanoclusters with both silane coupling agents, MPS and OTMS. The solvent evaporation method applied to functionalized nanoparticles showed to be an alternative way to the sinterization method for producing nanoclusters, which improved some dental composite mechanical properties and reduced water sorption. The shape of functionalized silica nanoclusters showed to have influence on the rheological properties of SiNC resin suspensions and the mechanical and sorption properties of light cured composites. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  16. Charge Carrier Dynamics at Silver Nanocluster-Molecular Acceptor Interfaces

    KAUST Repository

    Almansaf, Abdulkhaleq

    2017-07-01

    A fundamental understanding of interfacial charge transfer at donor-acceptor interfaces is very crucial as it is considered among the most important dynamical processes for optimizing performance in many light harvesting systems, including photovoltaics and photo-catalysis. In general, the photo-generated singlet excitons in photoactive materials exhibit very short lifetimes because of their dipole-allowed spin radiative decay and short diffusion lengths. In contrast, the radiative decay of triplet excitons is dipole forbidden; therefore, their lifetimes are considerably longer. The discussion in this thesis primarily focuses on the relevant parameters that are involved in charge separation (CS), charge transfer (CT), intersystem crossing (ISC) rate, triplet state lifetime, and carrier recombination (CR) at silver nanocluster (NCs) molecular-acceptors interfaces. A combination of steady-state and femto- and nanosecond broadband transient absorption spectroscopies were used to investigate the charge carrier dynamics in various donor-acceptor systems. Additionally, this thesis was prolonged to investigate some important factors that influence the charge carrier dynamics in Ag29 silver NCs donor-acceptor systems, such as the metal doping and chemical structure of the nanocluster and molecular acceptors. Interestingly, clear correlations between the steady-state measurements and timeresolved spectroscopy results are found. In the first study, we have investigated the interfacial charge transfer dynamics in positively charged meso units of 5, 10, 15, 20-tetra (1- methyl-4-pyridino)-porphyrin tetra (p-toluene sulfonate) (TMPyP) and neutral charged 5, 10, 15, 20-tetra (4-pyridyl)-porphyrin (TPyP), with negatively charged undoped and gold (Au)- doped silver Ag29 NCs. Moreover, this study showed the impact of Au doping on the charge carrier dynamics of the system. In the second study, we have investigated the interfacial charge transfer dynamics in [Pt2 Ag23 Cl7 (PPh3

  17. Is the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers sensitive to excluded volume interactions?

    Science.gov (United States)

    Shavykin, Oleg V; Neelov, Igor M; Darinskii, Anatolii A

    2016-09-21

    The effect of excluded volume (EV) interactions on the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers has been studied by using Brownian dynamics simulations. The study was motivated by the theory developed by Markelov et al., [J. Chem. Phys., 2014, 140, 244904] for a Gaussian dendrimer model without EV interactions. The theory connects the experimentally observed dependence of the spin-lattice relaxation rate 1/T(1)H on the location of NMR active groups with the restricted flexibility (semiflexibility) of dendrimers. Semiflexibility was introduced through the correlations between the orientations of different segments. However, these correlations exist even in flexible dendrimer models with EV interactions. We have simulated coarse-grained flexible and semiflexible dendrimer models with and without EV interactions. Every dendrimer segment consisted of two rigid bonds. Semiflexibility was introduced through a potential which restricts the fluctuations of angles between neighboring bonds but does not change orientational correlations in the EV model as compared to the flexible case. The frequency dependence of the reduced 1/T(1)H(ωH) for segments and bonds belonging to different dendrimer shells was calculated. It was shown that the main effect of EV interactions consists of a much stronger contribution of the overall dendrimer rotation to the dynamics of dendrimer segments as compared to phantom models. After the exclusion of this contribution the manifestation of internal dynamics in spin-lattice NMR relaxation appears to be practically insensitive to EV interactions. For the flexible models, the position ωmax of the peak of the modified 1/T(1)H(ωH) does not depend on the shell number. For semiflexible models, the maximum of 1/T(1)H(ωH) for internal segments or bonds shifts to lower frequencies as compared to outer ones. The dependence of ωmax on the number of dendrimer shells appears to be universal for segments and

  18. Direct TLC/MALDI-MS coupling for modified polyamidoamine dendrimers analyses.

    Science.gov (United States)

    Leriche, Emma-Dune; Hubert-Roux, Marie; Grossel, Martin C; Lange, Catherine M; Afonso, Carlos; Loutelier-Bourhis, Corinne

    2014-01-15

    Polyamidoamine (PAMAM) are synthetic dendrimers which present attractive properties for the biological and biomedical fields, as they proved to be efficient drug and gene carriers. In order to increase their transfection efficiency, chemical modifications of the amino end-groups had been reported. In this work, the synthesis of the ammonia-cored G1(N) PAMAM and the consecutive chemical modification with glycine or phenylalanine amino-acids were monitored using the coupling of thin layer chromatography (TLC) with matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS). Thus, the monitoring of the PAMAM synthesis included the identification of the by-products such as defective structures of PAMAM dendrimers as well as the study of phenylalanine-grafted PAMAM oligomer distribution. Copyright © 2013 Elsevier B.V. All rights reserved.

  19. Low cytotoxicity fluorescent PAMAM dendrimer as gene carriers for monitoring the delivery of siRNA

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Lingmei [Sichuan University, State Key Laboratory of Bio-resources and Eco-environment, The Ministry of Education, College of Life Sciences (China); Huang, Saipeng [Chinese Academy of Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center for Molecular Sciences, Institute of Chemistry (China); Chen, Zhao [Xi’an Jiaotong University, School of Science (China); Li, Yanchao [Chinese Academy of Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center for Molecular Sciences, Institute of Chemistry (China); Liu, Ke [Sichuan University, State Key Laboratory of Bio-resources and Eco-environment, The Ministry of Education, College of Life Sciences (China); Liu, Yang, E-mail: yliu@iccas.ac.cn; Du, Libo, E-mail: dulibo@iccas.ac.cn [Chinese Academy of Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Center for Molecular Sciences, Institute of Chemistry (China)

    2015-09-15

    Visual detection of gene vectors has attracted a great deal of attention due to the application of these vectors in monitoring and evaluating the effect of gene carriers in living cells. A non-viral vector, the fluorescent PAMAM dendrimer (F-PAMAM), was synthesized through conjugation of PAMAM dendrimers and fluorescein. In vitro and ex vivo experiments show that F-PAMAM exhibits superphotostability, low cytotoxicity and facilitates endocytosis by A549 cells. The vector has a high siRNA binding affinity and it increases the efficiency of cy5-siRNA delivery in A549 cells, in comparison with a cy5-siRNA monomer. Our results provide a new method for simultaneously monitoring the delivery of siRNA and its non-viral carriers in living cells.

  20. Triclosan-loaded poly(amido amine) dendrimer for simultaneous treatment and remineralization of human dentine.

    Science.gov (United States)

    Zhou, Yan; Yang, Jiaojiao; Lin, Zaifu; Li, Jiyao; Liang, Kunneng; Yuan, He; Li, Sheyu; Li, Jianshu

    2014-03-01

    In order to treat dental caries of damaged dentine, triclosan-loaded carboxyl-terminated poly(amido amine) dendrimer (PAMAM-COOH) is prepared and characterized. While being incubated in artificial saliva, triclosan-loaded PAMAM-COOH formulation can induce in situ remineralization of hydroxyapatite (HA) on etched dentine, and the regenerated HA has a similar crystal structure with natural dentine. It can also release the encapsulated triclosan for a long period. The interesting drug release profiles are controlled by both dendrimer encapsulation capability and the mineralization degree, which are ideal to obtain multifunctional properties of long-term release of anti-bacterial drug for local treatment during the remineralization process. The triclosan-loaded G4-COOH provides a general strategy to cure dental caries and repair damaged dentine at the same time, which forms a potential restorative material for dental repair.

  1. Vesicles from Amphiphilic Dumbbells and Janus Dendrimers: Bioinspired Self-Assembled Structures for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Soraya Taabache

    2017-07-01

    Full Text Available The current review focuses on vesicles obtained from the self-assembly of two types of dendritic macromolecules, namely amphiphilic Janus dendrimers (forming dendrimersomes and amphiphilic dumbbells. In the first part, we will present some synthetic strategies and the various building blocks that can be used to obtain dendritic-based macromolecules, thereby showing their structural versatility. We put our focus on amphiphilic Janus dendrimers and amphiphilic dumbbells that form vesicles in water but we also encompass vesicles formed thereof in organic solvents. The second part of this review deals with the production methods of these vesicles at the nanoscale but also at the microscale. Furthermore, the influence of various parameters (intrinsic to the amphiphilic JD and extrinsic—from the environment on the type of vesicle formed will be discussed. In the third part, we will review the numerous biomedical applications of these vesicles of nano- or micron-size.

  2. Divergent dendrimer synthesis via the Passerini three-component reaction and olefin cross-metathesis.

    Science.gov (United States)

    Kreye, Oliver; Kugele, Dennis; Faust, Lorenz; Meier, Michael A R

    2014-02-01

    The combination of the Passerini reaction and olefin cross-metathesis is shown to be a very useful approach for the divergent synthesis of dendrimers. Castor oil-derived platform chemicals, such as 10-undecenoic acid and 10-undecenal, are reacted in a Passerini reaction with an unsaturated isocyanide to obtain a core unit having three terminal double bonds. Subsequent olefin cross-metathesis with tert-butyl acrylate, followed by hydrogenation of the double bonds and hydrolysis of the tert-butyl ester, leads to an active core unit bearing three carboxylic acid groups as reactive sites. Iterative steps of the Passerini reaction with 10-undecenal and 10-isocyanodec-1-ene for branching, and olefin cross-metathesis with tert-butyl acrylate, followed by hydrogenation and hydrolysis allow the synthesis of a third-generation dendrimer. All steps of the synthesis are carefully characterized by NMR, GPC, MS, and IR.

  3. Palladium(0 Deposited on PAMAM Dendrimers as a Catalyst for C–C Cross Coupling Reactions

    Directory of Open Access Journals (Sweden)

    Tomasz Borkowski

    2011-01-01

    Full Text Available PAMAM dendrimers of generations G2–G3 as well as a partially substituted derivative of generation G4 and a low-molecular-weight tricyclic ligand 4 were used to bind Pd(0 nanoparticles. The obtained adducts were tested as catalysts for C–C cross-coupling reactions, such as the Suzuki-Miyaura, Hiyama, Heck and Sonogashira reaction. The highest yields of the coupling product, diphenylacetylene, were obtained with all the catalysts studied in the Sonogashira coupling performed in ethanol with K2CO3 as base. Very good results, 85–100%, were also found in the Suzuki-Miyaura cross-coupling, while the efficiency of the Hiyama coupling appeared lower, with 38–52% of 2-Methylbiphenyl formed. In all reactions, the G2–Pd(0 catalyst, containing an unmodified dendrimer, afforded the highest yields of the cross-coupling products.

  4. Dendrimer-Templated Ultrasmall and Multifunctional Photothermal Agents for Efficient Tumor Ablation.

    Science.gov (United States)

    Zhou, Zhengjie; Wang, Yitong; Yan, Yang; Zhang, Qiang; Cheng, Yiyun

    2016-04-26

    Ultrasmall and multifunctional nanoparticles are highly desirable for photothermal cancer therapy, but the synthesis of these nanoparticles remains a huge challenge. Here, we used a dendrimer as a template to synthesize ultrasmall photothermal agents and further modified them with multifunctional groups. Dendrimer-encapsulated nanoparticles (DENPs) including copper sulfide, platinum, and palladium nanoparticles possessed a sub-5 nm size and exhibited an excellent photothermal effect. DENPs were further modified with TAT or RGD peptides to facilitate their cellular uptake and targeting delivery to tumors. They were also decorated with fluorescent probes for real-time imaging and tracking of the particles' distribution. The in vivo study revealed RGD-modified DENPs efficiently reduced the tumor growth upon near-infrared irradiation. In all, our study provides a facile and flexible scaffold to prepare ultrasmall and multifunctional photothermal agents.

  5. High-Resolution Imaging of Dendrimers Used in Drug Delivery via Scanning Probe Microscopy

    Directory of Open Access Journals (Sweden)

    Lifang Shi

    2011-01-01

    Full Text Available Dendrimers and telodendrimer micelles represent two new classes of vehicles for drug delivery that have attracted much attention recently. Their structural characterization at the molecular and submolecular level remains a challenge due to the difficulties in reaching high resolution when imaging small particles in their native media. This investigation offers a new approach towards this challenge, using scanning tunneling microscopy (STM and atomic force microscopy (AFM. By using new sample preparation protocols, this work demonstrates that (a intramolecular features such as drug molecules and dendrimer termini can be resolved; and (b telodendrimer micelles can be immobilized on the surface without compromising structural integrity, and as such, high resolution AFM imaging may be performed to attain 3D information. This high-resolution structural information should enhance our knowledge of the nanocarrier structure and nanocarrier-drug interaction and, therefore, facilitate design and optimization of the efficiency in drug delivery.

  6. Metal dendrimers: synthesis of hierarchically stellated nanocrystals by sequential seed-directed overgrowth.

    Science.gov (United States)

    Weiner, Rebecca G; Skrabalak, Sara E

    2015-01-19

    Hierarchically organized structures are prevalent in nature, where such features account for the adhesion properties of gecko feet and the brilliant color variation of butterfly wings. Achieving artificial structures with multiscale features is of interest for metamaterials and biomimetic applications. However, the fabrication of such structures relies heavily on lithographic approaches, although self-assembly routes to superstructures are promising. Sequential seed-directed overgrowth is now demonstrated as a route to metal dendrimers, which are hierarchically branched nanocrystals (NCs) with a three-dimensional order analogous to that of molecular dendrimers. This method was applied to a model Au/Pd NC system; in general, the principle of sequential seed-directed overgrowth should enable the synthesis of new hierarchical inorganic structures with high symmetry.

  7. Layered Double Hydroxide Nanoclusters: Aqueous, Concentrated, Stable, and Catalytically Active Colloids toward Green Chemistry.

    Science.gov (United States)

    Tokudome, Yasuaki; Morimoto, Tsuyoshi; Tarutani, Naoki; Vaz, Pedro D; Nunes, Carla D; Prevot, Vanessa; Stenning, Gavin B G; Takahashi, Masahide

    2016-05-24

    Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems.

  8. XAFS studies of monodisperse Au nanoclusters formation in the etching process

    Science.gov (United States)

    Yang, Lina; Huang, Ting; Liu, Wei; Bao, Jie; Huang, Yuanyuan; Cao, Yuanjie; Yao, Tao; Sun, Zhihu; Wei, Shiqiang

    2016-05-01

    Understanding the formation mechanism of gold nanoclusters is essential to the development of their synthetic chemistry. Here, by using x-ray absorption fine-structure (XAFS) spectroscopy, UV-Vis and MS spectra, the formation process of monodisperse Au13 nanoclusters is investigated. We find that a critical step involving the formation of smaller Au8-Au11 metastable intermediate clusters induced by the HCl + HSR etching of the polydisperse Aun precursor clusters occurs firstly. Then these intermediate species undergo a size-growth to Au13 cores, followed by a slow structure rearrangement to reach the final stable structure. This work enriches the understanding of cluster formation chemistry and may guide the way towards the design and the controllable synthesis of nanoclusters.

  9. Crystal structure of selenolate-protected Au24(SeR)20 nanocluster.

    Science.gov (United States)

    Song, Yongbo; Wang, Shuxin; Zhang, Jun; Kang, Xi; Chen, Shuang; Li, Peng; Sheng, Hongting; Zhu, Manzhou

    2014-02-26

    We report the X-ray structure of a selenolate-capped Au24(SeR)20 nanocluster (R = C6H5). It exhibits a prolate Au8 kernel, which can be viewed as two tetrahedral Au4 units cross-joined together without sharing any Au atoms. The kernel is protected by two trimeric Au3(SeR)4 staple-like motifs as well as two pentameric Au5(SeR)6 staple motifs. Compared to the reported gold-thiolate nanocluster structures, the features of the Au8 kernel and pentameric Au5(SeR)6 staple motif are unprecedented and provide a structural basis for understanding the gold-selenolate nanoclusters.

  10. Coherent Fano resonances in a plasmonic nanocluster enhance optical four-wave mixing

    Science.gov (United States)

    Zhang, Yu; Wen, Fangfang; Zhen, Yu-Rong; Nordlander, Peter; Halas, Naomi J.

    2013-01-01

    Plasmonic nanoclusters, an ordered assembly of coupled metallic nanoparticles, support unique spectral features known as Fano resonances due to the coupling between their subradiant and superradiant plasmon modes. Within the Fano resonance, absorption is significantly enhanced, giving rise to highly localized, intense near fields with the potential to enhance nonlinear optical processes. Here, we report a structure supporting the coherent oscillation of two distinct Fano resonances within an individual plasmonic nanocluster. We show how this coherence enhances the optical four-wave mixing process in comparison with other double-resonant plasmonic clusters that lack this property. A model that explains the observed four-wave mixing features is proposed, which is generally applicable to any third-order process in plasmonic nanostructures. With a larger effective susceptibility χ(3) relative to existing nonlinear optical materials, this coherent double-resonant nanocluster offers a strategy for designing high-performance third-order nonlinear optical media. PMID:23690571

  11. Analysis of the applicability of Ni, Cu, Au, Pt, and Pd nanoclusters for data recording

    Science.gov (United States)

    Redel', L. V.; Gafner, S. L.; Gafner, Yu. Ya.; Zamulin, I. S.; Goloven'ko, Zh. V.

    2017-02-01

    The applicability of individual Ni, Cu, Au, Pt, and Pd nanoclusters as data bits in next generation memory devices constructed on the phase-change carrier principle is studied. To this end, based on the modified tight-binding potential (TB-SMA), structure formation from the melt of nanoparticles of these metals to 10 nm in diameter was simulated by the molecular dynamics method. The effect of various crystallization conditions on the formation of the internal structures of Ni, Cu, Au, Pt, and Pd nanoclusters is studied. The stability boundaries of various crystalline isomers are analyzed. The obtained systematic features are compared for nanoparticles of copper, nickel, gold, platinum, and palladium of identical sizes. It is concluded that platinum nanoclusters of diameter D > 8 nm are the best materials among studied metals for producing memory elements based on phase transitions.

  12. XAFS study on thiol etching of diphosphine-stabilized gold nanoclusters

    Science.gov (United States)

    Bao, Jie; Yang, Lina; Huang, Ting; Sun, Zhihu; Yao, Tao; Jiang, Yong; Wei, Shiqiang

    2017-08-01

    Thiol-etching triphenylphosphine (PPh3)-protected Au nanoclusters has been widely used to synthesize thiolated Au nanoclusters, while few studies have been reported on the thiol-etching reaction starting from diphosphine-protected Au clusters. Here the thiol-etching reaction in chloroform (CHCl3) for 1,5-Bis(diphenylphosphino) pentane (L5) protected Au11 nanoclusters is presented, and synchrotron radiation X-ray absorption fine structure, UV-vis absorption and mass spectra are combined to identify the reaction products. It is revealed that a gold(I)-thiolate complex Au2L5(RS) is produced, contrary to the case of thiol-etching PPh3-protected Au clusters where formation of thermodynamically stable Au25 or Au11 clusters is achieved.

  13. A novel dendrimer based on poly (L-glutamic acid) derivatives as an efficient and biocompatible gene delivery vector

    Science.gov (United States)

    Zeng, Xin; Pan, Shirong; Li, Jie; Wang, Chi; Wen, Yuting; Wu, Hongmei; Wang, Cuifeng; Wu, Chuanbin; Feng, Min

    2011-09-01

    Non-viral gene delivery systems based on cationic polymers have faced limitations related to their relative low gene transfer efficiency, cytotoxicity and system instability in vivo. In this paper, a flexible and pompon-like dendrimer composed of poly (amidoamine) (PAMAM) G4.0 as the inner core and poly (L-glutamic acid) grafted low-molecular-weight polyethylenimine (PLGE) as the surrounding multiple arms was synthesized (MGI dendrimer). The novel MGI dendrimer was designed to combine the merits of size-controlled PAMAM G4.0 and the low toxicity and flexible chains of PLGE. In phosphate-buffered saline dispersions the well-defined DNA/MGI complex above a N/P ratio of 30 showed good stability with particle sizes of approximately 200 nm and a comparatively low polydispersity index. However, the particle size of the DNA/25 kDa polyethylenimine (DNA/PEI 25K) complex was larger than 700 nm under the same salt conditions. The shielding of the compact amino groups at the periphery of flexible PAMAM and biocompatible PLGE chains in MGI resulted in a dramatic decrease of the cytotoxicity compared to native PAMAM G4.0 dendrimer. The in vitro transfection efficiency of DNA/MGI dendrimer complex was higher than that of PAMAM G4.0 dendrimer. Importantly, in serum-containing medium, DNA/MGI complexes at their optimal N/P ratio maintained the same high levels of transfection efficiency as in serum-free medium, while the transfection efficiency of native PAMAM G4.0, PEI 25K and Lipofectamine 2000 were sharply decreased. In vivo gene delivery of pVEGF165/MGI complex into balloon-injured rabbit carotid arteries resulted in significant inhibition of restenosis by increasing VEGF165 expression in local vessels. Therefore, the pompon-like MGI dendrimer may be a promising vector candidate for efficient gene delivery in vivo.

  14. Dendrimers and Polyamino-Phenolic Ligands: Activity of New Molecules Against Legionella pneumophila Biofilms

    Science.gov (United States)

    Andreozzi, Elisa; Barbieri, Federica; Ottaviani, Maria F.; Giorgi, Luca; Bruscolini, Francesca; Manti, Anita; Battistelli, Michela; Sabatini, Luigia; Pianetti, Anna

    2016-01-01

    Legionnaires’ disease is a potentially fatal pneumonia caused by Legionella pneumophila, an aquatic bacterium often found within the biofilm niche. In man-made water systems microbial biofilms increase the resistance of legionella to disinfection, posing a significant threat to public health. Disinfection methods currently used in water systems have been shown to be ineffective against legionella over the long-term, allowing recolonization by the biofilm-protected microorganisms. In this study, the anti-biofilm activity of previously fabricated polyamino-phenolic ligands and polyamidoamine dendrimers was investigated against legionella mono-species and multi-species biofilms formed by L. pneumophila in association with other bacteria that can be found in tap water (Aeromonas hydrophila, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae). Bacterial ability to form biofilms was verified using a crystal violet colorimetric assay and testing cell viability by real-time quantitative PCR and Plate Count assay. The concentration of the chemicals tested as anti-biofilm agents was chosen based on cytotoxicity assays: the highest non-cytotoxic chemical concentration was used for biofilm inhibition assays, with dendrimer concentration 10-fold higher than polyamino-phenolic ligands. While Macrophen and Double Macrophen were the most active substances among polyamino-phenolic ligands, dendrimers were overall twofold more effective than all other compounds with a reduction up to 85 and 73% of legionella and multi-species biofilms, respectively. Chemical interaction with matrix molecules is hypothesized, based on SEM images and considering the low or absent anti-microbial activity on planktonic bacteria showed by flow cytometry. These data suggest that the studied compounds, especially dendrimers, could be considered as novel molecules in the design of research projects aimed at the development of efficacious anti-biofilm disinfection treatments of water systems

  15. Dendrimers and polyamino-phenolic ligands: activity of new molecules against Legionella pneumophila biofilms.

    Directory of Open Access Journals (Sweden)

    Elisa eAndreozzi

    2016-03-01

    Full Text Available Legionnaires’ disease is a potentially fatal pneumonia caused by Legionella pneumophila, an aquatic bacterium often found within the biofilm niche. In man-made water systems microbial biofilms increase the resistance of legionella to disinfection, posing a significant threat to public health. Disinfection methods currently used in water systems have been shown to be ineffective against legionella over the long-term, allowing recolonization by the biofilm-protected microorganisms. In this study, the anti-biofilm activity of previously fabricated polyamino-phenolic ligands and polyamidoamine dendrimers was investigated against legionella mono-species and multi-species biofilms formed by L. pneumophila in association with other bacteria that can be found in tap water (Aeromonas hydrophila, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae. Bacterial ability to form biofilms was verified using a crystal violet colorimetric assay and testing cell viability by real-time quantitative PCR and Plate Count assay. The concentration of the chemicals tested as anti-biofilm agents was chosen based on cytotoxicity assays: the highest non-cytotoxic chemical concentration was used for biofilm inhibition assays, with dendrimer concentration ten-fold higher than polyamino-phenolic ligands. While Macrophen and Double Macrophen were the most active substances among polyamino-phenolic ligands, dendrimers were overall two-fold more effective than all other compounds with a reduction up to 85% and 73% of legionella and multi-species biofilms, respectively. Chemical interaction with matrix molecules is hypothesized, based on SEM images and considering the low or absent anti-microbial activity on planktonic bacteria showed by flow cytometry. These data suggest that the studied compounds, especially dendrimers, could be considered as novel molecules in the design of research projects aimed at the development of efficacious anti-biofilm disinfection

  16. Vortex-Induced Alignment of a Water Soluble Supramolecular Nanofiber Composed of an Amphiphilic Dendrimer

    Directory of Open Access Journals (Sweden)

    Akihiko Tsuda

    2013-06-01

    Full Text Available We have synthesized a novel amphiphilic naphthalene imide bearing a cationic dendrimer wedge (NID. NID molecules in water self-assemble to form a two-dimensional ribbon, which further coils to give a linear supramolecular nanofiber. The sample solution showed linear dichroism (LD upon stirring of the solution, where NID nanofibers dominantly align at the center of vortex by hydrodynamic interaction with the downward torsional flows.

  17. Vortex-induced alignment of a water soluble supramolecular nanofiber composed of an amphiphilic dendrimer.

    Science.gov (United States)

    Yamamoto, Taiki; Tsuda, Akihiko

    2013-06-17

    We have synthesized a novel amphiphilic naphthalene imide bearing a cationic dendrimer wedge (NID). NID molecules in water self-assemble to form a two-dimensional ribbon, which further coils to give a linear supramolecular nanofiber. The sample solution showed linear dichroism (LD) upon stirring of the solution, where NID nanofibers dominantly align at the center of vortex by hydrodynamic interaction with the downward torsional flows.

  18. Deposition of Silver Nanoparticles on Dendrimer Functionalized Multiwalled Carbon Nanotubes: Synthesis, Characterization and Antimicrobial Activity

    OpenAIRE

    2011-01-01

    The nanohybrids composed of silver nanoparticles and aromatic polyamide functionalized multiwalled carbon nanotubes (MWCNTs) is successfully synthesized and tested for their antibacterial activity against different pathogens. Prior to deposition of silver nanoparticles, acid treated MWCNTs (MWCNTs-COOH) were successively reacted with p-phenylenediamine and methylmethacrylate to form series of NH2-terminated aromatic polyamide dendrimers on the surface of MWCNTs through Michael addition and am...

  19. Design of dendrimer-based drug delivery nanodevices with enhanced therapeutic efficacies

    Science.gov (United States)

    Kannan, Rangaramanujam

    2007-03-01

    Dendrimers and hyperbranched polymers possess highly branched architectures, with a large number of controllable, tailorable, `peripheral' functionalities. Since the surface chemistry of these materials can be modified with relative ease, these materials have tremendous potential in targeted drug delivery. They have significant potential compared to liposomes and nanoparticles, because of the reduced macrophage update, increased cellular transport, and the ability to modulate the local environment through functional groups. We are developing nanodevices based on dendritic systems for drug delivery, that contain a high drug payload, ligands, and imaging agents, resulting in `smart' drug delivery devices that can target, deliver, and signal. In collaboration with the Children's Hospital of Michigan, Karmanos Cancer Institute, and College of Pharmacy, we are testing the in vitro and in vivo response of these nanodevices, by adapting the chemistry for specific clinical applications such as asthma and cancer. These materials are characterized by UV/Vis spectroscopy, flow cytometry, fluorescence/confocal microscopy, and appropriate animal models. Our results suggest that: (1) We can prepare drug-dendrimer conjugates with drug payloads of greater than 50%, for a variety of drugs; (2) The dendritic polymers are capable of transporting and delivering drugs into cells faster than free drugs, with superior therapeutic efficiency. This can be modulated by the surface functionality of the dendrimer; (3) For chemotherapy drugs, the conjugates are a factor of 6-20 times more effective even in drug-resistant cell lines; (4) For corticosteroidal drugs, the dendritic polymers provide higher drug residence times in the lung, allowing for passive targeting. The ability of the drug-dendrimer-ligand conjugates to target specific asthma and cancer cells is currently being explored using in vitro and in vivo animal models.

  20. UV-Photodimerization in Uracil-substituted dendrimers for high density data storage

    DEFF Research Database (Denmark)

    Lohse, Brian; Vestberg, Robert; Ivanov, Mario Tonev

    2007-01-01

    Two series of uracil-functionalized dendritic macromolecules based on poly (amidoamine) PAMAM and 2,2-bis(hydroxymethylpropionic acid) bis-MPA backbones were prepared and their photoinduced (2 pi+2 pi) cycloaddition reactions upon exposure to UV light at 257 nm examined. Dendrimers up to 4th...... nm with an intensity of 70 mW/cm(2) could be obtained suggesting future use as recording media for optical data storage. (c) 2007 Wiley Periodicals, Inc....

  1. Cell uptake mechanisms of PAMAM G4-FITC dendrimer in human myometrial cells

    Energy Technology Data Exchange (ETDEWEB)

    Oddone, Natalia; Zambrana, Ana I.; Tassano, Marcos [Instituto de Investigaciones Biologicas Clemente Estable, Laboratorio de Senalizacion Celular y Nanobiologia (Uruguay); Porcal, Williams [Universidad de la Republica, Grupo de Quimica Medicinal, Instituto de Quimica Biologica, Facultad de Ciencias-Facultad de Quimica (Uruguay); Cabral, Pablo [Universidad de la Republica, Laboratorio de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias (Uruguay); Benech, Juan C., E-mail: benech@iibce.edu.uy [Instituto de Investigaciones Biologicas Clemente Estable, Laboratorio de Senalizacion Celular y Nanobiologia (Uruguay)

    2013-07-15

    The high incidence and severity of diseases which involve smooth muscle dysfunction dictates the need of continued search for novel therapeutic strategies to treat these conditions. Dendrimers are branched macromolecules with multiple end-groups that can be functionalized for applications which include drug delivery. There is no data regarding the cellular uptake mechanisms used by dendrimers in smooth muscle human myometrial cells (HMC). Polyamidoamine G4 dendrimers were conjugated with fluorescein isothiocyanate (FITC) and the resulting conjugate (G4-FITC) was characterized using high-performance liquid chromatography, nuclear magnetic resonance, and atomic force microscopy. G4-FITC showed to have no significant effect on the primary culture HMC viability up to 48 h. HMC incubated with G4-FITC were analyzed by laser confocal microscopy. Peri-nuclear fluorescence distribution was observed at 5 h of incubation or more (24, 36, and 48 h). At 24 h, G4-FITC partially co-localized with lysotracker. Uptake of G4-FITC by HMC was slightly inhibited by filipin (8.0 {+-} 3.9 %) and significantly inhibited by chlorpromazine (63.5 {+-} 3.7 %). In non-electroporated HMC, G4-FITC was never observed inside the cell nucleus. Interestingly, we detected G4-FITC inside the nuclear domain of some electroporated cells. Thus, electroporation changed intracellular G4-FITC localization. Isolated nuclei of HMC incubated with G4-FITC showed fluorescence signal inside the nuclear domain. The results suggest that in HMC, G4-FITC is taken up by clathrin-mediated endocytosis with endosomal and lysosomal localization at 24 h. The combination of electroporation and dendrimers could be an interesting technology to electrotransfer drugs into smooth muscle cells cytosol and nuclei.

  2. Recent Findings Concerning PAMAM Dendrimer Conjugates with Cyclodextrins as Carriers of DNA and RNA

    Directory of Open Access Journals (Sweden)

    Keiichi Motoyama

    2009-08-01

    Full Text Available We have evaluated the potential use of various polyamidoamine (PAMAM dendrimer [dendrimer, generation (G 2-4] conjugates with cyclodextrins (CyDs as novel DNA and RNA carriers. Among the various dendrimer conjugates with CyDs, the dendrimer (G3 conjugate with α-CyD having an average degree of substitution (DS of 2.4 [α-CDE (G3, DS2] displayed remarkable properties as DNA, shRNA and siRNA delivery carriers through the sensor function of α-CDEs toward nucleic acid drugs, cell surface and endosomal membranes. In an attempt to develop cell-specific gene transfer carriers, we prepared sugar-appended α-CDEs. Of the various sugar-appended α-CDEs prepared, galactose- or mannose-appended α-CDEs provided superior gene transfer activity to α-CDE in various cells, but not cell-specific gene delivery ability. However, lactose-appended α-CDE [Lac-α-CDE (G2] was found to possess asialoglycoprotein receptor (AgpR-mediated hepatocyte-selective gene transfer activity, both in vitro and in vivo. Most recently, we prepared folate-poly(ethylene glycol-appended α-CDE [Fol-PαC (G3] and revealed that Fol-PαC (G3 imparted folate receptor (FR-mediated cancer cell-selective gene transfer activity. Consequently, α-CDEs bearing integrated, multifunctional molecules may possess the potential to be novel carriers for DNA, shRNA and siRNA.

  3. Efficient electrocatalytic oxidation of formic acid using Au@Pt dendrimer-encapsulated nanoparticles.

    Science.gov (United States)

    Iyyamperumal, Ravikumar; Zhang, Liang; Henkelman, Graeme; Crooks, Richard M

    2013-04-17

    We report electrocatalytic oxidation of formic acid using monometallic and bimetallic dendrimer-encapsulated nanoparticles (DENs). The results indicate that the Au147@Pt DENs exhibit better electrocatalytic activity and low CO formation. Theoretical calculations attribute the observed activity to the deformation of nanoparticle structure, slow dehydration of formic acid, and weak binding of CO on Au147@Pt surface. Subsequent experiments confirmed the theoretical predictions.

  4. Cell uptake mechanisms of PAMAM G4-FITC dendrimer in human myometrial cells

    Science.gov (United States)

    Oddone, Natalia; Zambrana, Ana I.; Tassano, Marcos; Porcal, Williams; Cabral, Pablo; Benech, Juan C.

    2013-07-01

    The high incidence and severity of diseases which involve smooth muscle dysfunction dictates the need of continued search for novel therapeutic strategies to treat these conditions. Dendrimers are branched macromolecules with multiple end-groups that can be functionalized for applications which include drug delivery. There is no data regarding the cellular uptake mechanisms used by dendrimers in smooth muscle human myometrial cells (HMC). Polyamidoamine G4 dendrimers were conjugated with fluorescein isothiocyanate (FITC) and the resulting conjugate (G4-FITC) was characterized using high-performance liquid chromatography, nuclear magnetic resonance, and atomic force microscopy. G4-FITC showed to have no significant effect on the primary culture HMC viability up to 48 h. HMC incubated with G4-FITC were analyzed by laser confocal microscopy. Peri-nuclear fluorescence distribution was observed at 5 h of incubation or more (24, 36, and 48 h). At 24 h, G4-FITC partially co-localized with lysotracker. Uptake of G4-FITC by HMC was slightly inhibited by filipin (8.0 ± 3.9 %) and significantly inhibited by chlorpromazine (63.5 ± 3.7 %). In non-electroporated HMC, G4-FITC was never observed inside the cell nucleus. Interestingly, we detected G4-FITC inside the nuclear domain of some electroporated cells. Thus, electroporation changed intracellular G4-FITC localization. Isolated nuclei of HMC incubated with G4-FITC showed fluorescence signal inside the nuclear domain. The results suggest that in HMC, G4-FITC is taken up by clathrin-mediated endocytosis with endosomal and lysosomal localization at 24 h. The combination of electroporation and dendrimers could be an interesting technology to electrotransfer drugs into smooth muscle cells cytosol and nuclei.

  5. Bimetallic dendrimer-encapsulated nanoparticles as catalysts: a review of the research advances

    OpenAIRE

    Peng, Xiaohong; Pan, Qinmin; Rempel, Garry L.

    2008-01-01

    Bimetallic dendrimer-encapsulated nanoparticles (DENs) are important materials, because they have demonstrated improvement in performance compared to the monometallic DENs in many systems when they are used as catalysts. This tutorial review focuses on the recent research advances in bimetallic DENs with respect to their synthesis, characterization, and applications as catalysts. Bimetallic DENs can be made mainly via three routes: co-complexation, sequential loading, and partial displacement...

  6. Vibrational spectra study of phosphorus dendrimer containing azobenzene, ammonium and carbamate groups

    Science.gov (United States)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2013-06-01

    The FTIR and FT Raman spectra of the first generation dendrimers, possessing carbamate (G1) or ammonium (G2) terminal groups were studied. The structural optimization and normal mode analysis were performed for dendrimers on the basis of the density functional theory (DFT). These calculations of G2 gave the frequencies of vibrations, infrared intensities and Raman scattering activities for the E- and Z-forms of azobenzene unit. The energy difference between the E- and Z-forms of G2 is 27.36 kcal/mol. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendrimers molecules have a concave lens structure with planar -O-C6H4-CHdbnd N-N(CH3)Pdbnd S, and -O-C6H4-Ndbnd N-C6H4-CHdbnd N-NH-Cdbnd O-CH2-N fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendrimers G1 and G2 were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1605 cm-1 in the IR spectra show marked changes of the optical density in dependence of substituents in the aromatic ring. The differences in the IR and Raman spectra of G2 for the E- and Z-forms of azobenzene units were cleared up. During structural isomerization of azobenzene units, redistribution of band intensities appears to a much higher extent than frequency shifts.

  7. Vibrational spectra study of phosphorus dendrimer containing azobenzene units on the surface

    Science.gov (United States)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2013-08-01

    The FTIR and FT Raman spectra of the first generation dendrimers, possessing oxybenzaldehyde (G1) or oxyphenylazobenzaldehyde (G2) terminal groups and sodium 4-[4-oxyphenyl)azo]-benzaldehyde (SOAB) were studied. The structural optimization and normal mode analysis were performed for dendrimer G2 on the basis of the density functional theory (DFT). These calculations gave the frequencies of vibrations, infrared intensities and Raman scattering activities for the E- and Z-forms of azobenzene unit. The energy differences between the E- and Z-forms are 12.62 and 25.16 kcal/mol for SOAB and G2. The calculated in gas phase dipole moments for the E- and Z-forms are equal to 20.86, 18.28 D (SOAB) and 7.56, 8.88 D (G2). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendrimer G2 molecule has a concave lens structure with planar sbnd Osbnd C6H4sbnd CHdbnd Nsbnd N(CH3)Pdbnd S and sbnd Osbnd C6H4sbnd Ndbnd Nsbnd C6H4sbnd CHdbnd O fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendrimer G2 were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1598 cm-1 in the IR spectra show marked changes of the optical density in dependence of substituents in the aromatic ring. The differences in the IR and Raman spectra of SOAB and G2 for the E- and Z-forms of azobenzene units were cleared up. During structural isomerization of azobenzene units, redistribution of band intensities appears to a much higher extent than frequency shifts.

  8. Crystal structure and electronic properties of a thiolate-protected Au24 nanocluster

    Science.gov (United States)

    Das, Anindita; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Rosi, Nathaniel L.; Jin, Rongchao

    2014-05-01

    Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''.Solving the total structures of gold nanoclusters is of critical importance for understanding their electronic, optical and catalytic properties. Herein, we report the X-ray structure of a charge-neutral Au24(SCH2Ph-tBu)20 nanocluster. This structure features a bi-tetrahedral Au8 kernel protected by four tetrameric staple-like motifs. Electronic structure analysis is further carried out and the optical absorption spectrum is interpreted. The Au24(SCH2Ph-tBu)20, Au23(S-c-C6H11)16 and Au25(SCH2CH2Ph)18 nanoclusters constitute the first crystallographically characterized ``trio''. Electronic supplementary information (ESI) available: Experimental and supporting Fig. S1-S3. CCDC NUMBER(1000102). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c4nr01350f

  9. Phenotypic Screening Identifies Protein Synthesis Inhibitors as H-Ras-Nanocluster-Increasing Tumor Growth Inducers.

    Science.gov (United States)

    Najumudeen, Arafath K; Posada, Itziar M D; Lectez, Benoit; Zhou, Yong; Landor, Sebastian K-J; Fallarero, Adyary; Vuorela, Pia; Hancock, John; Abankwa, Daniel

    2015-12-15

    Ras isoforms H-, N-, and K-ras are each mutated in specific cancer types at varying frequencies and have different activities in cell fate control. On the plasma membrane, Ras proteins are laterally segregated into isoform-specific nanoscale signaling hubs, termed nanoclusters. As Ras nanoclusters are required for Ras signaling, chemical modulators of nanoclusters represent ideal candidates for the specific modulation of Ras activity in cancer drug development. We therefore conducted a chemical screen with commercial and in-house natural product libraries using a cell-based H-ras-nanoclustering FRET assay. Next to established Ras inhibitors, such as a statin and farnesyl-transferase inhibitor, we surprisingly identified five protein synthesis inhibitors as positive regulators. Using commonly employed cycloheximide as a representative compound, we show that protein synthesis inhibition increased nanoclustering and effector recruitment specifically of active H-ras but not of K-ras. Consistent with these data, cycloheximide treatment activated both Erk and Akt kinases and specifically promoted H-rasG12V-induced, but not K-rasG12V-induced, PC12 cell differentiation. Intriguingly, cycloheximide increased the number of mammospheres, which are enriched for cancer stem cells. Depletion of H-ras in combination with cycloheximide significantly reduced mammosphere formation, suggesting an exquisite synthetic lethality. The potential of cycloheximide to promote tumor cell growth was also reflected in its ability to increase breast cancer cell tumors grown in ovo. These results illustrate the possibility of identifying Ras-isoform-specific modulators using nanocluster-directed screening. They also suggest an unexpected feedback from protein synthesis inhibition to Ras signaling, which might present a vulnerability in certain tumor cell types.

  10. An amperometric chloramphenicol immunosensor based on cadmium sulfide nanoparticles modified-dendrimer bonded conducting polymer.

    Science.gov (United States)

    Kim, Dong-Min; Rahman, Md Aminur; Do, Minh Hien; Ban, Changill; Shim, Yoon-Bo

    2010-03-15

    An amperometric chloramphenicol (CAP) immunosensor was fabricated by covalently immobilizing anti-chloramphenicol acetyl transferase (anti-CAT) antibody on cadmium sulfide nanoparticles (CdS) modified-dendrimer that was bonded to the conducting polymer (poly 5, 2': 5', 2''-terthiophene-3'-carboxyl acid (poly-TTCA)) layer. The AuNPs, dendrimers, and CdS nanoparticles were deposited onto the polymer layer in order to enhance the sensitivity of the sensor probes. The particle sizes were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The immobilization of dendrimers, CdS, and anti-CAT were confirmed using energy disruptive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance (QCM) techniques. The detection of CAP was based on the competitive immuno-interaction between the free- and labeled-CAP for active sites of the anti-CAT. Hydrazine was used as the label for CAP, and it electrochemically catalyzed the reduction of H(2)O(2) at -0.35 V vs. Ag/AgCl. Under optimized conditions, the proposed immunosensor exhibited a linear range of CAP detection between 50 pg/mL and 950 pg/mL, and the detection limit was 45 pg/mL. The immunosensor was examined in real meat samples for the analysis of CAP.

  11. Dendrimer-magnetic nanoparticles as multiple stimuli responsive and enzymatic drug delivery vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Chandra, Sudeshna; Noronha, Glen [Metallurgical and Materials Science Department, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India); Dietrich, Sascha; Lang, Heinrich [Technische Universität Chemnitz, Institute of Chemistry, Straße der Nationen 62, d-09111 Chemnitz (Germany); Bahadur, Dhirendra, E-mail: dhirenb@iitb.ac.in [Metallurgical and Materials Science Department, Indian Institute of Technology Bombay, Powai, Mumbai, 400076 (India)

    2015-04-15

    Two different chain lengths of (poly)ethylene glycol-PAMAM dendrimers namely, L6-PEG-PAMAM and S6-PEG-PAMAM with six end-grafted ethylene glycol ether-tentacles of type CH{sub 2}CH{sub 2}C(O)O(CH{sub 2}CH{sub 2}O){sub 9}CH{sub 3} and CH{sub 2}CH{sub 2}C(O)O(CH{sub 2}CH{sub 2}O){sub 2}C{sub 2}H{sub 5}, respectively, were synthesized. These dendrimers have multiple σ-donor capabilities and therefore, were used for stabilizing the magnetite (Fe{sub 3}O{sub 4}) nanoparticles. Both the dendrimer-magnetic nanoparticles (L6-PEG-PAMAM-MNPs and S6-PEG-PAMAM-MNPs) were characterized by different spectroscopic and microstructural techniques. The nanoparticles were mesoporous and superparamagnetic and therefore, explored for their possible use in delivery of cancer drug, doxorubicin (DOX). In the developed drug delivery system, achieving high drug-loading efficiency with controllable release were the main challenges. The change in zeta potential and quenching of fluorescence intensity suggests chemical interaction between DOX and the nanoparticles. The loading efficiency was calculated to be over 95% with a sustained pH and temperature sensitive release. Further, enzyme cathepsin B has also been used to degrade the dendritic shell to trigger sustained drug release in the vicinity of tumor cells.

  12. Dendrimer-Functionalized Laponite Nanodisks as a Platform for Anticancer Drug Delivery

    Directory of Open Access Journals (Sweden)

    Rania Mustafa

    2015-10-01

    Full Text Available In this study, we synthesized dendrimer-functionalized laponite (LAP nanodisks for loading and delivery of anticancer drug doxorubicin (DOX. Firstly, LAP was modified with silane coupling agents and succinic anhydride to render abundant carboxyl groups on the surface of LAP. Then, poly(amidoamine (PAMAM dendrimer of generation 2 (G2 were conjugated to form LM-G2 nanodisks. Anticancer drug DOX was then loaded on the LM-G2 with an impressively high drug loading efficiency of 98.4% and could be released in a pH-sensitive and sustained manner. Moreover, cell viability assay results indicate that LM-G2/DOX complexes could more effectively inhibit the proliferation of KB cells (a human epithelial carcinoma cell line than free DOX at the same drug concentration. Flow cytometry analysis and confocal laser scanning microscope demonstrated that LM-G2/DOX could be uptaken by KB cells more effectively than free DOX. Considering the exceptional high drug loading efficiency and the abundant dendrimer amine groups on the surface that can be further modified, the developed LM-G2 nanodisks may hold a great promise to be used as a novel platform for anticancer drug delivery.

  13. Low temperature synthesis of ordered mesoporous stable anatase nanocrystals: the phosphorus dendrimer approach.

    Science.gov (United States)

    Brahmi, Younes; Katir, Nadia; Ianchuk, Mykhailo; Collière, Vincent; Essassi, El Mokhtar; Ouali, Armelle; Caminade, Anne-Marie; Bousmina, Mosto; Majoral, Jean Pierre; El Kadib, Abdelkrim

    2013-04-07

    The scarcity of low temperature syntheses of anatase nanocrystals prompted us to explore the use of surface-reactive fourth generation phosphorus-dendrimers as molds to control the nucleation and growth of titanium-oxo-species during the sol-gel mineralization process. Unexpectedly, the dendritic medium provides at low temperature, discrete anatase nanocrystals (4.8 to 5.2 nm in size), in marked contrast to the routinely obtained amorphous titanium dioxide phase under standard conditions. Upon thermal treatment, heteroatom migration from the branches to the nanoparticle surface and the ring opening polymerization of the cyclophosphazene core provide stable, interpenetrating mesoporous polyphosphazene-anatase hybrid materials (-P[double bond, length as m-dash]N-)n-TiO2. The steric hindrance of the dendritic skeleton, the passivation of the anatase surface by heteroatoms and the ring opening of the core limit the crystal growth of anatase to 7.4 nm and prevent, up to 800 °C, the commonly observed anatase-to-rutile phase transformation. Performing this mineralization in the presence of similar surface-reactive but non-dendritic skeletons (referred to as branch-mimicking dendrimers) failed to generate crystalline anatase and to efficiently limit the crystal growth, bringing thus clear evidence of the virtues of phosphorus dendrimers in the design of novel nanostructured materials.

  14. Polymer nanoparticles with dendrimer-Ag shell and its application in catalysis

    Institute of Scientific and Technical Information of China (English)

    Gaofei Dang; Yan Shi; Zhifeng Fu; Wantai Yang

    2013-01-01

    Polymer nanoparticles with dendrimer-Ag shell were prepared and their application in catalytic reduction of 4-nitrophenol (4-NP) was investigated.Cross-linked polystyrene (PS) microspheres were prepared through dispersion copolymerization of styrene,acrylic acid and crosslinking monomer 1,2-divinylbenzene.PS microspheres with average size of 450 nm and narrow size distribution were used as support for the immobilization of dendrimer-Ag shell.The polyamidoamine (PAMAM) dendrimer shell was successively grafted onto the surface of PS microspheres through repetitive Michael addition reaction of methyl acrylate (MA) and amidation of the obtained esters with large excess of ethylenediamine (EDA).Silver nanoparticles were formed directly inside the PAMAM shell through reduction with NaBH4.The resulting PS@PAMAM-Ag nanoparticles were packed in a stainless steel column and used successfully for catalytic reduction of 4-NP.This technique for packing catalytic polymer particles in a column could improve the efficiency of using the metal catalyst and the tedious separation in catalytic reaction.

  15. RNA-Based TWIST1 Inhibition via Dendrimer Complex to Reduce Breast Cancer Cell Metastasis

    Directory of Open Access Journals (Sweden)

    James Finlay

    2015-01-01

    Full Text Available Breast cancer is the leading cause of cancer-related deaths among women in the United States, and survival rates are lower for patients with metastases and/or triple-negative breast cancer (TNBC; ER, PR, and Her2 negative. Understanding the mechanisms of cancer metastasis is therefore crucial to identify new therapeutic targets and develop novel treatments to improve patient outcomes. A potential target is the TWIST1 transcription factor, which is often overexpressed in aggressive breast cancers and is a master regulator of cellular migration through epithelial-mesenchymal transition (EMT. Here, we demonstrate an siRNA-based TWIST1 silencing approach with delivery using a modified poly(amidoamine (PAMAM dendrimer. Our results demonstrate that SUM1315 TNBC cells efficiently take up PAMAM-siRNA complexes, leading to significant knockdown of TWIST1 and EMT-related target genes. Knockdown lasts up to one week after transfection and leads to a reduction in migration and invasion, as determined by wound healing and transwell assays. Furthermore, we demonstrate that PAMAM dendrimers can deliver siRNA to xenograft orthotopic tumors and siRNA remains in the tumor for at least four hours after treatment. These results suggest that further development of dendrimer-based delivery of siRNA for TWIST1 silencing may lead to a valuable adjunctive therapy for patients with TNBC.

  16. Novel Dendrimer-Like Star Copolymer Architectures Investigated with Scattering Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pople, John A

    2001-10-17

    Hyperbranched dendrimer molecules emanating from a central core were successfully synthesized just over a decade ago and have been gaining the interest of polymer scientists due to their unique properties and promising applications. Several groups have sought structural and dynamic information on dendrimeric molecules with some degree of success. Most of the studies thus far have focused on dendrimeric structures having relatively short links between branching points and having a uniform distribution of branches throughout the molecule. We are interested in dendrimer-star molecules where polymer chains connect the branch points and the length and placement of these chains can be varied systematically. We have taken one approach to such systems by investigating a series of constitutional isomers having the same molecular weight and number of branch points and surface functionalities, but varied branch placement to alter the architecture. In this way, we can study the influence of the architecture on the structure, interactions, and dynamics of these molecules. to provide neutron scattering contrast. The PCL dendrimer-like stars then comprise the cores of the molecules while the PMMA chains emanate from the periphery. The samples used in the scattering experiments were prepared in either THF or toluene, which are both good solvents for PCL and PMMA, to mass fractions of 0.2 wt% to 30 wt%.

  17. Magnetism of FePt Nanoclusters in Polyimide

    Directory of Open Access Journals (Sweden)

    Mircea Chipara

    2015-01-01

    Full Text Available FePt nanoclusters have been implanted onto polyimide films and subjected to thermal annealing in order to obtain a special magnetic phase (L10 dispersed within the polymer. SQUID measurements quantified the magnetic features of the as-prepared and annealed hybrid films. As-implanted FePt nanoparticles in polyimide films exhibited a blocking temperature of 70 ± 5 K. Thermal annealing in zero and 10 kOe applied magnetic field increased the magnetic anisotropy and coercivity of the samples. Wide Angle X-Ray Scattering confirmed the presence of FePt and L10 phase. All samples (as deposited and annealed exhibited electron spin resonance spectra consisting of two overlapping lines. The broad line was a ferromagnetic resonance originating from FePt nanoparticles. Its angular dependence indicated the magnetic anisotropy of FePt nanoparticles. SEM micrographs suggest a negligible coalescence of FePt nanoparticles, supporting that the enhancement of the magnetic properties is a consequence of the improvement of the L10 structure. The narrow ESR line was assigned to nonmagnetic (paramagnetic impurities within the samples consistent with graphite-like structures generated by the local degradation of the polymer during implantation and annealing. Raman spectroscopy confirmed the formation of graphitic structures in annealed KHN and in KHN-FePt.

  18. Photoluminescent gold nanoclusters as sensing probes for uropathogenic Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Po-Han Chan

    Full Text Available Glycan-bound nanoprobes have been demonstrated as suitable sensing probes for bacteria containing glycan binding sites. In this study, we demonstrated a facile approach for generating glycan-bound gold nanoclusters (AuNCs. The generated AuNCs were used as sensing probes for corresponding target bacteria. Mannose-capped AuNCs (AuNCs@Mann were generated and used as the model sensors for target bacteria. A one-step synthesis approach was employed to generate AuNCs@Mann. In this approach, an aqueous solution of tetrachloroauric acid and mannoside that functionized with a thiol group (Mann-SH was stirred at room temperature for 48 h. The mannoside functions as reducing and capping agent. The size of the generated AuNCs@Mann is 1.95±0.27 nm, whereas the AuNCs with red photoluminescence have a maximum emission wavelength of ~630 nm (λexcitation = 375 nm. The synthesis of the AuNCs@Mann was accelerated by microwave heating, which enabled the synthesis of the AuNCs@Mann to complete within 1 h. The generated AuNCs@Mann are capable of selectively binding to the urinary tract infection isolate Escherichia coli J96 containing the mannose binding protein FimH expressed on the type 1 pili. On the basis of the naked eye observation, the limit of detection of the sensing approach is as low as ~2×10(6 cells/mL.

  19. Photoluminescent gold nanoclusters as sensing probes for uropathogenic Escherichia coli.

    Science.gov (United States)

    Chan, Po-Han; Ghosh, Bhaswati; Lai, Hong-Zheng; Peng, Hwei-Ling; Mong, Kwok Kong Tony; Chen, Yu-Chie

    2013-01-01

    Glycan-bound nanoprobes have been demonstrated as suitable sensing probes for bacteria containing glycan binding sites. In this study, we demonstrated a facile approach for generating glycan-bound gold nanoclusters (AuNCs). The generated AuNCs were used as sensing probes for corresponding target bacteria. Mannose-capped AuNCs (AuNCs@Mann) were generated and used as the model sensors for target bacteria. A one-step synthesis approach was employed to generate AuNCs@Mann. In this approach, an aqueous solution of tetrachloroauric acid and mannoside that functionized with a thiol group (Mann-SH) was stirred at room temperature for 48 h. The mannoside functions as reducing and capping agent. The size of the generated AuNCs@Mann is 1.95±0.27 nm, whereas the AuNCs with red photoluminescence have a maximum emission wavelength of ~630 nm (λexcitation = 375 nm). The synthesis of the AuNCs@Mann was accelerated by microwave heating, which enabled the synthesis of the AuNCs@Mann to complete within 1 h. The generated AuNCs@Mann are capable of selectively binding to the urinary tract infection isolate Escherichia coli J96 containing the mannose binding protein FimH expressed on the type 1 pili. On the basis of the naked eye observation, the limit of detection of the sensing approach is as low as ~2×10(6) cells/mL.

  20. Silver Nanoclusters: From Design Principles to Practical Applications

    KAUST Repository

    Abdulhalim, Lina G.

    2015-12-08

    A strategy based on reticulating metal ions and organic ligands into atomically precise gold and silver nanoclusters (NCs) with high monodispersity has been advanced to a point that allows the design of NCs with strict stoichiometries, functionalities and valence. Of the Ag NCs discovered, Ag44 is the most studied, not only due to its high absorption that transcends the visible spectrum suitable for photovoltaics but also because of its long excited state lifetime, as revealed by nanosecond transient absorption spectroscopy. A major principle discovered in this dissertation is the ability to produce Ag44 in scalable amounts and with high stability in addition to modulation of the functional groups of the organic ligands via a fast and complete ligand exchange process. This new discovery has led to the development of synthetic designs in which new sizes were obtained by varying the reaction parameters (e.g., ligands functionality, reaction temperature and time), namely, Ag29 using dithiols and phosphines. The synthesized NCs possess tetravalent functionalities that facilitate their crystallization and characterization. Furthermore, Ag29 glows red and is therefore a possible candidate for sensing and imaging applications.