Localization of lysozyme sorption to conventional and silicone hydrogel contact lenses using confocal microscopy

Abstract

Purpose: To investigate the distribution profile of hen egg lysozyme (HEL) through poly-2-hydroxyethyl methacrylate (pHEMA)-based lens materials and silicone hydrogel (SH) lens materials using confocal laser scanning microscopy (CLSM).

Methods: Five silicone SH materials (balafilcon A, lotrafilcon A, lotrafilcon B, galyfilcon A, senofilcon A) and four pHEMA-based materials (alphafilcon A, etafilcon A, omafilcon A, vifilcon A) were incubated in 1.9 mg/ml protein solution for 24 hours. The protein solution consisted of HEL, which was conjugated with either fluorescein isothiocyanate (FITC) or lucifer yellow VS dilithium salt (LY). CLSM (Zeiss LSM 510 META) identified the location of the fluorescently labeled protein by using 1 micro m depth scans through the lens. In a second experiment, lenses were incubated with 2% (125) I labeled HEL to determine the amount of deposited protein on each lens. Both techniques were combined to describe the individual HEL profiles.

Results: After the incubation in fluorescently labeled HEL, all pHEMA-based materials and the SH material balafilcon A accumulated protein throughout the entire lens material, while, for the SH lenses lotrafilcon A and lotrafilcon B, HEL was primarily detected on the lens surface alone. Differences in protein uptake pattern due solely to the two conjugated dyes were most apparent for the SH materials galyfilcon A and senofilcon A; HEL was detected throughout these lenses when conjugated with LY but accumulated primarily on the surface when conjugated with FITC.

Conclusion: CLSM in combination with a radiolabel technique can describe both the location and degree of protein deposition on different contact lens materials.