The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Ye Hong - One of the best experts on this subject based on the ideXlab platform.
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poly 1 vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes a rheological study
Polymer International, 1998Co-Authors: Traian V Chirila, Ye HongAbstract:In order to develop an artificial vitreous, a large series of hydrogels have been previously produced by polymerization of 1-vinyl-2-Pyrrolidinone, with or without crosslinking. Based on the assumption that a functional vitreous substitute should possess viscoelastic properties after its delivery, a number of selected gels were characterized rheologically by both oscillatory shear stress analysis and shear creep analysis, using a controlled stress rheometer in the cone/plate configuration. The experiments demonstrated a dramatic effect of injecting the gels through small-gauge needles, as many lost their viscoelasticity to become free-flowing fluids, probably because of the cleavage of chains and crosslinks. It was also found that the increase of comonomer content (2-hydroxyethyl methacrylate) and of crosslinking level generally had a strengthening effect. However, the effects of hydrophilic crosslinking agents (diallyl ether and divinyl glycol) were irregular. Eventually, only four hydrogels in this series showed viscoelastic characteristics after injection through a 30-gauge (0·13mm diameter) needle, maintaining behaviour typical of crosslinked networks and warranting further assessment as potential vitreous substitutes. © 1998 SCI.
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biodegradation in vitro and retention in the rabbit eye of crosslinked poly 1 vinyl 2 Pyrrolidinone hydrogel as a vitreous substitute
Journal of Biomedical Materials Research, 1998Co-Authors: Ye Hong, Traian V Chirila, S Vijayasekaran, Weiyong Shen, Paul D DaltonAbstract:To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-Pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14 C- labeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments. The polymer was synthesized by the free-radical copolymeriza- tion of 99% 1-vinyl-2-Pyrrolidinone with 1% 14 C-methyl methacrylate in the presence of ethylene glycol dimethacry- late (0.1%) as crosslinking agent. The in vitro protocol for assessing the biodegradation included the incubation of hy- drogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products. Within the maximum du- ration of experiments (4 weeks), none of the procedures in- dicated biodegradation of polymer. The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks. Residual radioactivity measurements of the vit- reous contents indicated that 50% of the polymer was re- moved by the end of this period. Histopathologic examina- tion revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue. A possible phago- cyte-mediated mechanism for the dissipation of hydrogel is discussed. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 650-659, 1998.
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effect of crosslinked poly 1 vinyl 2 Pyrrolidinone gels on cell growth in static cell cultures
Bio-medical Materials and Engineering, 1997Co-Authors: Ye Hong, Traian V Chirila, J H Fitton, B W Ziegelaar, Ian ConstableAbstract:: Poly(1-vinyl-2-Pyrrolidinone) (PVP) and copolymers of 1-vinyl-2-Pyrrolidinone are insoluble in water when crosslinked but they can absorb very large amounts of water to become syringe-injectable hydrogels. Such gels have been investigated recently as potential substitutes for the vitreous humour in the eye. In this study, during the cytotoxic evaluation by sulforhodamine B colorimetric assay of variously crosslinked PVP gels, it was found that many of them showed protective/growth promoting effects on 3T3 mouse fibroblasts in static cultures, a phenomenon encountered previously only with aqueous solutions of a limited number of natural or synthetic polymers. Particularly, the gels crosslinked with diethylene glycol dimethacrylate (DEGDMA) induced a significant enhancement of cell proliferation, especially in serum-free cultures. No correlation between this effect and the essential gel properties (chemical composition, viscoelasticity and equilibrium water content) could be established. The study demonstrated that crosslinked PVP hydrogels showed a serum-like growth promoting effect on an anchorage-dependent cell line, which may be due to physical protection, inability of the insoluble gels to penetrate cell membranes, and their ability to mimic the extracellular matrix.
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poly i vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes histopathological evaluation in the animal eye
Journal of Biomaterials Science-polymer Edition, 1996Co-Authors: S Vijayasekaran, Ye Hong, Traian V Chirila, Ian Constable, Paul D Dalton, Sjakon G Tahija, Ian L McallisterAbstract:A homopolymer of 1-vinyl-2 Pyrrolidinone and its copolymer with 2-hydroxyethyl methacrylate, both cross-linked with divinyl glycol, were produced as possible substitutes for the vitreous body of the eye. The hydrated polymers behaved like viscoelastic gels, displaying excellent physical and optical properties. The sterile gels (0.7-1.5 ml) were injected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exception of transient opacities in the vitreous. After 4 weeks, the operated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature in all sections was the invasion of inflammatory cells. Vacuoles containing granular material, assumed to be polymer, were seen in the intercellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It ...
Traian V Chirila - One of the best experts on this subject based on the ideXlab platform.
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poly 1 vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes a rheological study
Polymer International, 1998Co-Authors: Traian V Chirila, Ye HongAbstract:In order to develop an artificial vitreous, a large series of hydrogels have been previously produced by polymerization of 1-vinyl-2-Pyrrolidinone, with or without crosslinking. Based on the assumption that a functional vitreous substitute should possess viscoelastic properties after its delivery, a number of selected gels were characterized rheologically by both oscillatory shear stress analysis and shear creep analysis, using a controlled stress rheometer in the cone/plate configuration. The experiments demonstrated a dramatic effect of injecting the gels through small-gauge needles, as many lost their viscoelasticity to become free-flowing fluids, probably because of the cleavage of chains and crosslinks. It was also found that the increase of comonomer content (2-hydroxyethyl methacrylate) and of crosslinking level generally had a strengthening effect. However, the effects of hydrophilic crosslinking agents (diallyl ether and divinyl glycol) were irregular. Eventually, only four hydrogels in this series showed viscoelastic characteristics after injection through a 30-gauge (0·13mm diameter) needle, maintaining behaviour typical of crosslinked networks and warranting further assessment as potential vitreous substitutes. © 1998 SCI.
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biodegradation in vitro and retention in the rabbit eye of crosslinked poly 1 vinyl 2 Pyrrolidinone hydrogel as a vitreous substitute
Journal of Biomedical Materials Research, 1998Co-Authors: Ye Hong, Traian V Chirila, S Vijayasekaran, Weiyong Shen, Paul D DaltonAbstract:To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-Pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14 C- labeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments. The polymer was synthesized by the free-radical copolymeriza- tion of 99% 1-vinyl-2-Pyrrolidinone with 1% 14 C-methyl methacrylate in the presence of ethylene glycol dimethacry- late (0.1%) as crosslinking agent. The in vitro protocol for assessing the biodegradation included the incubation of hy- drogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products. Within the maximum du- ration of experiments (4 weeks), none of the procedures in- dicated biodegradation of polymer. The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks. Residual radioactivity measurements of the vit- reous contents indicated that 50% of the polymer was re- moved by the end of this period. Histopathologic examina- tion revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue. A possible phago- cyte-mediated mechanism for the dissipation of hydrogel is discussed. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 650-659, 1998.
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effect of crosslinked poly 1 vinyl 2 Pyrrolidinone gels on cell growth in static cell cultures
Bio-medical Materials and Engineering, 1997Co-Authors: Ye Hong, Traian V Chirila, J H Fitton, B W Ziegelaar, Ian ConstableAbstract:: Poly(1-vinyl-2-Pyrrolidinone) (PVP) and copolymers of 1-vinyl-2-Pyrrolidinone are insoluble in water when crosslinked but they can absorb very large amounts of water to become syringe-injectable hydrogels. Such gels have been investigated recently as potential substitutes for the vitreous humour in the eye. In this study, during the cytotoxic evaluation by sulforhodamine B colorimetric assay of variously crosslinked PVP gels, it was found that many of them showed protective/growth promoting effects on 3T3 mouse fibroblasts in static cultures, a phenomenon encountered previously only with aqueous solutions of a limited number of natural or synthetic polymers. Particularly, the gels crosslinked with diethylene glycol dimethacrylate (DEGDMA) induced a significant enhancement of cell proliferation, especially in serum-free cultures. No correlation between this effect and the essential gel properties (chemical composition, viscoelasticity and equilibrium water content) could be established. The study demonstrated that crosslinked PVP hydrogels showed a serum-like growth promoting effect on an anchorage-dependent cell line, which may be due to physical protection, inability of the insoluble gels to penetrate cell membranes, and their ability to mimic the extracellular matrix.
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poly i vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes histopathological evaluation in the animal eye
Journal of Biomaterials Science-polymer Edition, 1996Co-Authors: S Vijayasekaran, Ye Hong, Traian V Chirila, Ian Constable, Paul D Dalton, Sjakon G Tahija, Ian L McallisterAbstract:A homopolymer of 1-vinyl-2 Pyrrolidinone and its copolymer with 2-hydroxyethyl methacrylate, both cross-linked with divinyl glycol, were produced as possible substitutes for the vitreous body of the eye. The hydrated polymers behaved like viscoelastic gels, displaying excellent physical and optical properties. The sterile gels (0.7-1.5 ml) were injected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exception of transient opacities in the vitreous. After 4 weeks, the operated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature in all sections was the invasion of inflammatory cells. Vacuoles containing granular material, assumed to be polymer, were seen in the intercellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It ...
Yingjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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c 8 n ethyl 2 Pyrrolidinone substituted flavan 3 ols from the leaves of camellia sinensis var pubilimba
Journal of Agricultural and Food Chemistry, 2018Co-Authors: Xiuhua Meng, Dong Wang, Chongren Yang, Yingjun ZhangAbstract:Camellia sinensis var. pubilimba, one variety of the genus Camellia sect. Thea (Theaceae), has been used for producing green tea mainly by the local people of its growing areas of Guangxi province, China. Forty compounds, including eight C-8 N-ethyl-2-Pyrrolidinone-substituted flavan-3-ols (1–8) and their substituted unit N-ethyl-5-hydroxy-2-Pyrrolidinone (9), four flavan-3-ol monomers (10–13) and one dimer (14), nine flavonoids (15–23), three hydrolyzable tannins (24–26), two lignans (27–28), 11 simple phenolics (29–39), and caffeine (40), were first isolated and identified from the leaves. Their structures were determined by detailed spectroscopic analysis and comparison with the literature data and authentic samples. Both 1 and 4 were obtained as a mixture of the N-ethyl-2-Pyrrolidinone C-5 enantiomers (1a and 1b and 4a and 4b), respectively, while the resolution of another three pairs of enantiomers (2 and 3, 5 and 6, and 7 and 8) was achieved. Among them, 1b is a new compound whose NMR data together ...
Paul D Dalton - One of the best experts on this subject based on the ideXlab platform.
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biodegradation in vitro and retention in the rabbit eye of crosslinked poly 1 vinyl 2 Pyrrolidinone hydrogel as a vitreous substitute
Journal of Biomedical Materials Research, 1998Co-Authors: Ye Hong, Traian V Chirila, S Vijayasekaran, Weiyong Shen, Paul D DaltonAbstract:To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-Pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14 C- labeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments. The polymer was synthesized by the free-radical copolymeriza- tion of 99% 1-vinyl-2-Pyrrolidinone with 1% 14 C-methyl methacrylate in the presence of ethylene glycol dimethacry- late (0.1%) as crosslinking agent. The in vitro protocol for assessing the biodegradation included the incubation of hy- drogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products. Within the maximum du- ration of experiments (4 weeks), none of the procedures in- dicated biodegradation of polymer. The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks. Residual radioactivity measurements of the vit- reous contents indicated that 50% of the polymer was re- moved by the end of this period. Histopathologic examina- tion revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue. A possible phago- cyte-mediated mechanism for the dissipation of hydrogel is discussed. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 39, 650-659, 1998.
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poly i vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes histopathological evaluation in the animal eye
Journal of Biomaterials Science-polymer Edition, 1996Co-Authors: S Vijayasekaran, Ye Hong, Traian V Chirila, Ian Constable, Paul D Dalton, Sjakon G Tahija, Ian L McallisterAbstract:A homopolymer of 1-vinyl-2 Pyrrolidinone and its copolymer with 2-hydroxyethyl methacrylate, both cross-linked with divinyl glycol, were produced as possible substitutes for the vitreous body of the eye. The hydrated polymers behaved like viscoelastic gels, displaying excellent physical and optical properties. The sterile gels (0.7-1.5 ml) were injected into the vitreous cavity of rabbits, which previously underwent gas-mediated vitrectomy. Clinically, the eyes were quiet, with the exception of transient opacities in the vitreous. After 4 weeks, the operated eyes were enucleated and subjected to histopathological analysis using light and transmission electron microscopy. The common feature in all sections was the invasion of inflammatory cells. Vacuoles containing granular material, assumed to be polymer, were seen in the intercellular spaces of the neural retina, in the retinal pigment epithelium cells, and in macrophages. These findings indicated the fragmentation and phagocytosis of synthetic gels. It ...
N V Sastry - One of the best experts on this subject based on the ideXlab platform.
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densities viscosities speeds of sound and relative permittivities for water cyclic amides 2 Pyrrolidinone 1 methyl 2 Pyrrolidinone and 1 vinyl 2 Pyrrolidinone at different temperatures
Journal of Chemical & Engineering Data, 2004Co-Authors: N V SastryAbstract:Experimental densities, ρ, viscosities, η, speeds of sound, υ, and relative permittivities, er, for three binary mixtures of water + 2-Pyrrolidinone, + 1-methyl-2-Pyrrolidinone, and + 1-vinyl-2-Pyrrolidinone were measured over the entire composition range and at different temperatures. The variations of ρ, η, and υ with water mole fractions were typical of systems which show large nonidealities. The excess molar volumes, , excess isentropic compressibilities, , and deviations in dynamic viscosities, δη, and relative permittivities, δer, were calculated, and their compositional variation was mathematically represented by a Redlich−Kister type equation. The partial molar volumes of water at infinite dilution, , were calculated from the smoothed values of three binary mixtures at different temperatures. The variation of the Kirkwood correlation factor, gK, was examined across the entire composition range. The analysis of these functions revealed that both hydrophobic and hydrophilic hydrations are responsibl...
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Densities, Viscosities, Speeds of Sound, and Relative Permittivities for Water + Cyclic Amides (2-Pyrrolidinone, 1-Methyl-2-Pyrrolidinone, and 1-Vinyl-2-Pyrrolidinone) at Different Temperatures
Journal of Chemical & Engineering Data, 2004Co-Authors: John George And, N V SastryAbstract:Experimental densities, ρ, viscosities, η, speeds of sound, υ, and relative permittivities, er, for three binary mixtures of water + 2-Pyrrolidinone, + 1-methyl-2-Pyrrolidinone, and + 1-vinyl-2-Pyrrolidinone were measured over the entire composition range and at different temperatures. The variations of ρ, η, and υ with water mole fractions were typical of systems which show large nonidealities. The excess molar volumes, , excess isentropic compressibilities, , and deviations in dynamic viscosities, δη, and relative permittivities, δer, were calculated, and their compositional variation was mathematically represented by a Redlich−Kister type equation. The partial molar volumes of water at infinite dilution, , were calculated from the smoothed values of three binary mixtures at different temperatures. The variation of the Kirkwood correlation factor, gK, was examined across the entire composition range. The analysis of these functions revealed that both hydrophobic and hydrophilic hydrations are responsibl...