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Miguel F. Refojo - One of the best experts on this subject based on the ideXlab platform.

  • Intravitreal silicone and fluorosilicone oils: pathologic findings in rabbit eyes.
    Acta Ophthalmologica, 2009
    Co-Authors: J. Carlos Pastor, María I. López, M.a. Saornil, Miguel F. Refojo
    Abstract:

    The effects of medical-grade intraocular silicone and commercial-grade fluorosilicone oils were studied in rabbit eyes. The experimental model consisted of lensectomized and vitrectomized eyes that did not undergo further treatment (Group 1), and three groups of lensectomized and vitrectomized eyes that were injected intravitreously 3 months earlier with medical-grade silicone oil of 1000 cs (Group 3), and 10 000 cs (Group 4). The silicone oil-injected eyes developed proliferative membranes. The fluorosilicone oil caused an intravitreous inflammatory reaction with vacuolated macrophages present around the oil that may have been due to the higher concentration of low-molecular-weight components found in the oil.

  • Histopathology of rabbit eyes with silicone-fluorosilicone copolymer oil as six months internal retinal tamponade
    Experimental Eye Research, 2005
    Co-Authors: Motoaki Doi, Miguel F. Refojo
    Abstract:

    Abstract Silicone-fluorosilicone copolymer oil has low viscosity (175–185 cSt) and is heavier than water (density, 1·16 g cm−3). Short term retinal tolerance (within 2 months) of the silicone-fluorosilicone copolymer oil has been reported to be the same as that of currently used intraocular silicone oil. Ocular response of the purified silicone-fluorosilicone copolymer oil were examined clinically and histopathologically from 2·5 months to 6 months after vitreous cavity injection in rabbit phakic eyes, and compared the oil tolerance with that of purified silicone oil (0·97 g cm−3, 5000 cSt). The effects in anterior chamber also were examined within 4 weeks of the silicone-fluorosilicone copolymer oil injection in different rabbits. Silicone-fluorosilicone copolymer oil recovered from the vitreous cavity at 6 months was analysed for cholesterol and retinol content by high performance liquid chromatography. Because of its low viscosity, silicone-fluorosilicone copolymer oil was easy to inject and remove from the vitreous cavity with a 20-G needle. After the vitreous injection, discrete droplet formation by the silicone-fluorosilicone copolymer oil occurred more easily than by silicone oil. Medullary ray detachment was seen in a silicone oil-, and some silicone-fluorosilicone copolymer oil-injected eyes at 4–6 months. Histopathologically, after 3–6 months disappearance of outer plexiform layer and disorganization of the photoreceptor layer of silicone oil-, and silicone-fluorosilicone copolymer oil-injected eyes were seen in the superior and the inferior retina, respectively. Migration of the photoreceptor cell nuclei to the photoreceptor layer was found in the inferior retina of silicone-fluorosilicone copolymer oil-injected eyes at 5–6 months. Small droplets ingested by mononuclear cells were found in the vitreous cavity or preretina at 4–6 months in silicone-fluorosilicone copolymer oil-injected eyes. After the anterior chamber injection, silicone-fluorosilicone copolymer oil induced endothelial cell damage in the area where the oil contacted continuously. Retinol and cholesterol were identified in silicone-fluorosilicone copolymer oil removed from the vitreous cavity. Silicone-fluorosilicone copolymer oil may be useful as an intraoperative device in retinal detachment surgery and as a short term (up to about 2 months) retinal tamponade but we do not recommend it for long term retinal tamponade.

  • Histopathologic retinal changes with intravitreous fluorosilicone oil in rabbit eyes.
    Retina-the Journal of Retinal and Vitreous Diseases, 2000
    Co-Authors: Motoaki Doi, Ma Ning, Hiroshige Ida, Yukitaka Uji, Miguel F. Refojo
    Abstract:

    BACKGROUND Fluorosilicone oil (FSiO, 1,000-10,000 centistokes), which has a higher density (1.29 g/cm3) than vitreous gel, is useful as an operative tool and a tamponade for the inferior retina during difficult retinal detachment surgery. The occurrence of histopathologic retinal changes after injection of FSiO into the vitreous cavity is controversial. METHODS Retinas obtained from 18 rabbits were evaluated histopathologically within 8 weeks of injection into the vitreous cavity of purified FSiO or balanced salt solution as control in phakic eyes. The histopathologic retinal changes caused by FSiO were compared with those of previously reported high-density hydrophobic vitreous substitutes, such as silicone-fluorosilicone copolymer oil (SiFO) and perfluorocarbon liquids. RESULTS By light and electron microscopy, all retinas injected with FSiO were the same as control retinas within 2 weeks of the injection, but the outer plexiform layer disappeared from the inferior retina 4 weeks after injection. The receptor cell nuclei migrated to the photoreceptor layer in the inferior retina 8 weeks after injection. However, no preretinal membrane, including foam cells, was found in any eye injected with FSiO. CONCLUSION FSiO may be useful as a temporary vitreous substitute in difficult inferior retinal detachments.

  • Histopathology of rabbit eyes with intravitreous silicone-fluorosilicone copolymer oil.
    Experimental Eye Research, 1994
    Co-Authors: Motoaki Doi, Miguel F. Refojo
    Abstract:

    Silicone-fluorosilicone copolymer oil is characterized by being heavier than water (density, 1.16 g cm-3) and low viscosity (175-185 centistokes) compared with currently used intraocular silicone oils (density, 0.97 g cm-3 and 1000-5000 centistokes). This oil is potentially useful as an operative tool and a tamponade on the inferior retina in complicated retinal detachment. We evaluate the ocular response clinically and histopathologically within 8 weeks in rabbit phakic eyes to the purified silicone-fluorosilicone copolymer oil after vitreous cavity injection, and compared the oil tolerance with purified silicone oil (0.97 g cm-3, 5000 centistokes) and perfluorotetradecahydrophenanthrene for ophthalmic use (Vitreon, 2.03 g cm-3, 8.03 centistokes) which are currently used as operative tools and as internal retinal tamponade agents in retinal detachment surgery. Because of their low viscosity, silicone-fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene were easier to inject into the eye than silicone oil. Silicone-fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene occupied the inferior portion in the eye, and silicone oil occupied the superior portion. Fewer discrete oil droplets and weaker vessel attenuation of medullary rays than in the perfluorotetradecahydrophenanthrene-injected eyes were seen in silicone-fluorosilicone-copolymer-oil-injected eyes. Histopathologically, all retinas injected with silicone-fluorosilicone copolymer oil were normal within 4 weeks. The silicone-fluorosilicone copolymer oil dispersion did not induce histopathological changes within 8 weeks. However, thinning or disappearance of the outer plexiform layer was seen in the inferior retina in some silicone-fluorosilicone-copolymer-oil-injected eyes at 6-8 weeks. A similar effect was found in the superior retina of a silicone-oil-injected eye at 8 weeks. More severe changes such as thinning or disappearance of the outerplexiform layer, thinning and disorganization of the photoreceptor layer, and migration of the receptor cell nuclei to the photoreceptor layer were found in the inferior retina of perfluorotetradecahydrophenanthrene-injected eyes after 2 weeks. Intraocular silicone-fluorosilicone copolymer oil tolerance until about 2 months post-injection is similar to silicone oil and better than perfluorotetradecahydrophenanthrene. Silicone-fluorosilicone copolymer oil may be useful intraoperatively and as a temporary vitreous substitute in cases of inferior retinal detachment.

Santanu Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.

  • The synergistic effect of fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend
    Journal of Polymer Research, 2020
    Co-Authors: Sipra Khanra, Debabrata Ganguly, Sanjoy Kumar Ghorai, Debottam Goswami, Santanu Chattopadhyay
    Abstract:

    Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.

Xiaoyan Yuan - One of the best experts on this subject based on the ideXlab platform.

  • Fluorosilicone multi-block copolymers tethering quaternary ammonium salt groups for antimicrobial purpose
    Applied Surface Science, 2015
    Co-Authors: Fang Zhou, Yunhui Zhao, Xiaoshuai Qin, Lixia Ren, Xiaoyan Yuan
    Abstract:

    Abstract Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition–fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N+ composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N+ content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.

  • Balance of polyacrylate-fluorosilicone block copolymers as icephobic coatings
    Chinese Journal of Polymer Science (English Edition), 2015
    Co-Authors: Kaiqiang Zhang, Jing zhe Cai, Yunhui Zhao, Hui Li, Xiaoyan Yuan
    Abstract:

    Polyacrylate-fluorosilicone block copolymers, namely, polyacrylate-b-polydimethylsiloxane and polyacrylate-b-polymethyltrifluoropropylsiloxane were synthesized for fabricating icephobic coatings. The surface morphology and chemical composition of the block copolymers were characterized by atomic force microscopy and X-ray photoelectron spectroscopy, suggesting that the fluorosilicone blocks aggregated on the top of the copolymer surfaces. Results of water contact angles and ice shear strength demonstrated a certain amount adding of methacryloisobutyl polyhedral oligomeric silsesquioxane could lead to the decrease of contact angle hysteresis and increase of surface roughness, consequently resulting in significant reduction of the ice adhesion strength. Therefore, the block copolymers with the combined advantages of silicone and fluoropolymers could be potentially applied as icephobic coatings.

Wang Jing-he - One of the best experts on this subject based on the ideXlab platform.

Sipra Khanra - One of the best experts on this subject based on the ideXlab platform.

  • The synergistic effect of fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend
    Journal of Polymer Research, 2020
    Co-Authors: Sipra Khanra, Debabrata Ganguly, Sanjoy Kumar Ghorai, Debottam Goswami, Santanu Chattopadhyay
    Abstract:

    Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.