HUMAN SERUM-ALBUMIN ADSORPTION ON HYDROGEL CONTACT-LENSES IN-VITRO

Purpose. To improve the understanding of the formation of protein depo sits on hydrogel lenses. Methods. A study of protein adsorption on thr ee commercial hydrogel contact lenses of different materials, Etafilco n A (2-hydroxyethyl methacrylate [HEMA] polymer with sodium methacryla te and 2-ethyl-2-hydroxymethyl-1,3-propanediol trimethatrylate), tefil con (poly[HEMA] cross-linked and copolpmerized with ethylene glycol di methacrylate), and vifilcon A (metha crylic acid polymer with ethylene glycol dimethacrylate, HEMA and N-vinyl pyrrolidone) was undertaken b y using a single protein solution, human serum albumin (PISA), and a r adiolabel-tracer technique. Results. Static adsorption leading to mult ilayer adsorption was observed. Complete reversibility for adsorbed HS A on lenses did not exist. Some was tightly bound, whereas most was lo osely bound and could be removed easily by rinsing in phosphate-buffer ed saline. Irreversible adsorption of HSA on the lenses was found to b e time dependent and did not reach a maximum value even after 48 hours of adsorption. The amount of PISA adsorbed on the lenses-irreversibly as well as totally adsorbed protein-was in the order of vifilcon A >t efilcon >etafilcon A. Adsorption of HSA on the lenses increases with d ecreasing pH (range, 7.4 to 4) but always follows the above trend with respect to the different types of lenses. Conclusions. Irreversible b inding of HSA on lenses is governed by the kinetics of protein denatur ation. Electrostatic interactions may not play a major role in HSA ads orption on hydrogel lenses. Some other factors, such as hydrophobic de hydration, and special monomer units, such as N-vinyl pyrrolidone in t he lens materials, may favor adsorption of HSA.