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Y. Krishna, R. Williams, D. Kent, I. Grierson, C. Sheridan; Optimisation of Retinal Pigment Epithelial Cell (RPE) Growth on Expanded Polytetrafluoroethylene . Invest. Ophthalmol. Vis. Sci. 2006;47(13):895.
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AMD is the main cause of registered blindness in the Western World and despite recent advances, there is limited preventative or curative treatment. Transplantation of RPE under the macula represents a potential treatment. However, since delivery of isolated cells can cause serious complications, we investigated methods to establish an intact functioning RPE monolayer on an artificial substrate that could be implanted under the macula and substitute for damaged native Bruch’s membrane. Expanded polytetrafluoroethylene (ePTFE) is a fluoropolymer which is already used clinically in non–ophthalmic fields and fulfils many of the prerequisites as a transplanting device, however cells do not attach and spread on ePTFE. In this study we investigated the possibility of modifying the surface properties of ePTFE to promote the growth of healthy RPE monolayers.
ePTFE was cut into 3mm diameter discs and surface modified by ammonia gas plasma treatment using a half–wave helical resonator plasma system. Immediately following treatment the samples were placed in distilled water for 24 hours. Dynamic contact angles were measured using the Wilhelmy plate technique to determine the increase in wettability induced by the plasma treatment. Human ARPE–19 cells were seeded onto untreated and treated samples and incubated at 37oC with 5% CO2. At set time intervals samples were fixed and cell number, cellular morphology and monolayer formation and cytotoxicity were assessed by immunofluorescent staining and microscopy. Cell number, morphology and formation of cell–cell junctions on treated ePTFE surfaces were also investigated in the presence of differentiating agents.
Plasma treatment resulted in increased wettability with lower advancing and receding values. This significantly enhanced cell adhesion and growth, reaching confluence by Day 7, in comparison to untreated substrates (p<0.0028; Friedman Test). Immunofluorescence revealed well–defined actin staining, monolayer formation and high cell viability on treated surfaces. Furthermore, a higher cell packing density with homogeneous cell growth and evident tight junctional staining were observed on treated surfaces in the presence of differentiating agents. Conversely, only isolated cell clumps were found on the untreated ePTFE, at all time–points.
ePTFE can be surface modified to support an intact monolayer of healthy RPE cells.
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