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M. van Beek, H. Sheardown, L. Jones; The Effect of Wetting Agents on Competitive Protein Adsorption to HEMA and HEMA/MA/PVP Hydrogels . Invest. Ophthalmol. Vis. Sci. 2006;47(13):112.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously demonstrated that hyaluronic acid (HA) and PVP can be incorporated into contact lenses for release over a period consistent with daily wear. In the current work, we examined the effect of released wetting agents on the adsorption of tear proteins to hydrogels with similar compositions to lens materials to better understand the role of protein adsorption on lens comfort.
2–hydroxyethylmethacrylate(HEMA) and HEMA/methacrylic acid(MA)/ polyvinyl pyrrolidone(PVP) hydrogels were prepared by free radical polymerization. 0.25 inch diameter dried polymer disks were were soaked in 0.5 mg/mL ethanol/water solutions of HA (6.3 kDa, 50kDa, 169kDa and 900 kDa) for four days. Simulated tear solutions containing lysozyme (1.9 mg/ml), albumin (0.2 mg/ml), immunoglobulin G (1.7 mg/ml) and beta–lactoglobulin as a substitute for tear lipocalin (1.6 mg/ml) were prepared in phosphate buffered saline. For all adsorption studies one of the proteins was 125I labeled. The HA releasing disks were rinsed with phosphate–buffered saline (PBS) buffer and incubated with the simulated tear solution for two hours. This was followed by an extensive PBS rinse to remove any loosely bound protein. Amount of adsorbed protein was determined by gamma counting.
The protein adsorption trends for all surfaces generally showed higher lysozyme adsorption relative to the other proteins. Trends suggested that beta–lactoglobulin showed the next highest levels of adsorption followed by IgG with only small amounts of albumin being observed on both materials. There were differences in the levels of adsorbed protein on the HEMA versus the HEMA/MA/PVP materials, both in the protein adsorption trends and in the amounts of adsorbed protein. Surprisingly, while HA release for up to 15 hours was observed previously from similar materials, the incorporation of HA into the matrix and its subsequent release during the adsorption did not seem to affect protein interactions. There were no statistically significant differences between the controls and the surfaces which contained the wetting agents.
Protein adsorption trends demonstrated that lysozyme consistently adsorbs in significant quantities to hydrogel materials used in the manufacture of contact lenses, even in the presence of other tear proteins. There were other material specific differences with the other proteins examined. Surprisingly, the incorporation of wetting agents did not significantly affect protein adsorption. Work is continuing with commercial lenses.
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