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2 Pyrrolidinone

The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

Ye Hong – 1st expert on this subject based on the ideXlab platform

  • poly 1 vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes a rheological study
    Polymer International, 1998
    Co-Authors: Traian V Chirila, Ye Hong

    Abstract:

    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.

  • 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, 1998
    Co-Authors: Ye Hong, Traian V Chirila, S Vijayasekaran, Weiyong Shen, Paul D Dalton

    Abstract:

    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.

  • effect of crosslinked poly 1 vinyl 2 Pyrrolidinone gels on cell growth in static cell cultures
    Bio-medical Materials and Engineering, 1997
    Co-Authors: Ye Hong, Traian V Chirila, J H Fitton, B W Ziegelaar, Ian Constable

    Abstract:

    : 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.

Traian V Chirila – 2nd expert on this subject based on the ideXlab platform

  • poly 1 vinyl 2 Pyrrolidinone hydrogels as vitreous substitutes a rheological study
    Polymer International, 1998
    Co-Authors: Traian V Chirila, Ye Hong

    Abstract:

    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.

  • 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, 1998
    Co-Authors: Ye Hong, Traian V Chirila, S Vijayasekaran, Weiyong Shen, Paul D Dalton

    Abstract:

    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.

  • effect of crosslinked poly 1 vinyl 2 Pyrrolidinone gels on cell growth in static cell cultures
    Bio-medical Materials and Engineering, 1997
    Co-Authors: Ye Hong, Traian V Chirila, J H Fitton, B W Ziegelaar, Ian Constable

    Abstract:

    : 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.

Yingjun Zhang – 3rd expert on this subject based on the ideXlab platform

  • c 8 n ethyl 2 Pyrrolidinone substituted flavan 3 ols from the leaves of camellia sinensis var pubilimba
    Journal of Agricultural and Food Chemistry, 2018
    Co-Authors: Xiuhua Meng, Dong Wang, Chongren Yang, Yingjun Zhang

    Abstract:

    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 …