The Influence of a Peroxide-Based Versus a Polyhexanide-Based MPS in Controlling Both the Quantity and Conformation of Desposited Lysozyme on Silicone-Hydrogel Contact Lenses

Abstract

Abstract: : Purpose: To quantify both the amount and percentage of denatured lysozyme that is deposited on silicone-hydrogel contact lens materials [balafilcon (PureVision {PV}; B&L) and lotrafilcon (Focus Night&Day {FND}; CIBA]) when cared for by a peroxide-based multipurpose system (AOSept Plus; CIBA) and a polyhexanide-based system (ReNu MultiPlus; B&L). Methods: A prospective, double-blind, randomized, cross-over, daily wear clinical trial was conducted with 20 participants. Each subject wore a FND lens in one eye and a PV lens in the contralateral eye, while using either CIBA AOSept Plus or B&L ReNu MultiPlus), for a period of 4-weeks. After each system had been used for 4-weeks the lenses were collected and replaced with a second pair, which were used with the second care regimen. All lenses were aseptically collected and immediately placed in 1.5 mL of extraction buffer, comprised of 50:50 acetonitrile:0.2% trifluoroacetic acid. Total lysozyme was quantified via Western blotting and the percentage of denatured lysozyme was assessed using a modified Micrococcus lysodekticus assay. A two-way repeated measures analysis of variance was performed on all data to assess differences between lens materials and care regimens. Results: PV lenses deposited 14±8 or 19±9 µg of lysozyme / lens and FND lenses deposited 0.5±0.3 or 0.7±0.4 µ g / lens when cared for with AOSept Plus or ReNu MultiPlus, respectively. The amount of lysozyme deposited on PV lenses was significantly greater than that deposited on FND lenses (p< 0.001) and the care regimen did not influence the amount of lysozyme deposited (p=NS). The percentage of denatured lysozyme found on PV lenses was 87±9 or 89±8% and 57±16 or 51±23% for FND lenses, when cared for with AOSept Plus or ReNu MultiPlus respectively. The percentage of denatured lysozyme found on FND lenses was significantly greater than that found on PV lenses (p< 0.001) and these results were not affected by the care regimen (p=NS). Conclusions: The results demonstrate that significant differences exists between PV and FND lenses with respect to both the amount of deposited lysozyme and the degree to which the lysozyme is denatured. Neither amount nor conformation of deposited lysozyme on silicone-hydrogel materials appears to be influenced by the care regimen.

Keywords: contact lens • protein structure/function • protein purification and characterization