In vitro adsorption of tear proteins to hydroxyethyl methacrylate-based contact lens materials.

OBJECTIVES: Investigations of polymer interactions in single protein solutions is a necessary step in the elucidation of in vivo early binding events during protein deposition on hydroxyethyl methacrylate-based contact lens materials. Quantity and tenacity of binding of significant tear components to groups I and IV contact lenses was assessed. Competitive binding by these components was also examined. METHODS: Adsorption on FDA groups I and IV hydrogel lenses was monitored using I-labeled protein. Lenses were incubated in increasing concentrations of radiolabeled single species proteins in solution. For competition experiments, concentration of each radiolabeled protein was held constant and the adsorption/sorption challenged with increasing concentrations of nonlabeled proteins. Lenses were soaked in phosphate-buffered saline to determine desorption. RESULTS: Group IV lenses bound large amounts of lysozyme, whereas group I lenses bound highest amounts of albumin. Albumin binding to both lens types was relatively strong and could not be competed from binding by other proteins lysozyme, lactoferrin, and mucin. Mucin at high concentrations tended to positively cooperate with the binding of lactoferrin and albumin to all lenses. CONCLUSIONS: Binding of proteins to hydroxyethyl methacrylate-based hydrogel lens surfaces is affected by charge and polymer components, and perhaps manufacturing processes. Albumin binds strongly to lens surfaces, and this may play an adverse role during contact lens wear.

The adsorption of major tear film lipids in vitro to various silicone hydrogels over time.

PURPOSE: An in vitro study was conducted to measure the adsorption of major tear film lipids to soft contact lenses over time. METHODS: Commercial balafilcon A (PureVision; Bausch & Lomb, Rochester, NY), galyfilcon A (Acuvue Advance; Johnson & Johnson Vision Care), lotrafilcon A and B (Night & Day And O(2)Optix; CIBA Vision, Duluth, GA), senofilcon A (Acuvue Oasys; Johnson & Johnson Vision Care, Jacksonville, FL) and etafilcon A (Acuvue 2; Johnson & Johnson Vision Care) lenses were all soaked for 14 hours in the dark at 34.5 degrees C in either cholesterol (CH; nonpolar lipid) or phosphatidylethanolamine (PE; polar lipid), tagged with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) and N-fluorescein-5-thiocarbamoyl (FITC) labels, respectively. After rinsing, the lenses were measured for fluorescence and the corresponding lipid concentration was calculated from an appropriate standard curve. The lenses were then placed into a fresh 1-mL aliquot of the lipid being tested, and the procedure was repeated for 20 days. RESULTS: In vitro adsorption of CH was greater that that of PE for all lens types (P < 0.0001 at days 14 and 20). After 20 days of soaking in PE, the lotrafilcon polymers showed the lowest adsorption of all the silicone hydrogel lenses tested at 0.4 and 1.5 microg/lens, for lotrafilcon A (P < or = 0.0001) and lotrafilcon B, respectively (P < or = 0.0001). Galyfilcon A and senofilcon A showed significantly higher PE adsorption at 5.1 and 4.9 microg/lens, respectively, compared with all other silicone hydrogel lenses investigated (P < 0.03). Senofilcon A (P < 0.0001) and balafilcon A (P < 0.02) had the highest affinity for CH of all the lens types after 20 days, with adsorptions of 23.2 and 24.1 microg/lens, respectively. Lotrafilcon B (P < 0.0001) showed the lowest in vitro adsorption of CH of all the lens types, at 3 mug/lens. CONCLUSIONS: In vitro lipid adsorption varied greatly depending on the lens material for both polar and nonpolar lipids. Overall, there was less in vitro adsorption of lipid to the lotrafilcon A and B polymers than for any of the other silicone hydrogel polymers tested. The quantity of lipid adsorption by lotrafilcon polymers was similar to "conventional" hydrogel lenses.

Development of a new extended-wear contact lens model in the rat.

PURPOSE: To develop a rat model to experimentally monitor the potential inflammatory effects of soft contact lens (CL) usage on the cornea during extended wear (EW). METHODS: Lewis rats were fitted with EW lotrafilcon A (CIBA Vision, Duluth, GA) hydrogel lenses (Dk/t 175 barrers/cm) in the left eye, the right eye serving as a control. After 12 days (n = 5 rats) and 30 days (n = 8 rats) of continuous extended wear, corneas were removed and total RNA was extracted from both CL-wearing and non-lens-wearing eyes. Multiprobe ribonuclease protection assays (RPA) were used to detect and compare cytokine and chemokine gene expression in corneas from both groups. RESULTS: Cytokine-chemokine mRNA expression levels were similar for interleukin (IL)-1alpha, IL-1 receptor antagonist (RA), IL- 18, transforming growth factor (TGF)-beta1, TGF-beta2, TGF-beta3, and macrophage migration inhibitory factor (MIF) levels in CL-wearing and non-lens-wearing corneas after 12 or 30 days of EW. CONCLUSION: This in vivo rat model for extended contact lens wear allows analysis and comparison of mRNA levels of cytokines and chemokines in the cornea with and without EW soft CL use. Remarkably, after 12 or 30 days of continuous CL wear, there was no significant up-regulation in lens wearing corneas for any of the cytokines-chemokines tested.