Adsorption of serum albumin to thin films of poly(lactide-co-glycolide)

Protein adsorption has been implicated in the variability of drug release f rom biodegradable microspheres. We used optical reflectometry to measure th e extent and kinetics of bovine serum albumin (BSA) adsorption to smooth sp in-cast films prepared from two poly(lactide-co-glycolide) (PLG) samples th at have different end-groups, one being a hydrophilic carboxylic end group and the other a hydrophobic ester end group. One of us has previously shown that these end-groups influence microsphere degradation (Tracy et al., 199 8, Factors affecting the degradation rate of poly(lactide-co-glycolide) mic rospheres in vivo and in vitro. Biomaterials: submitted for publication.). Both films were moderately hydrophobic, and their wettability was independe nt of the type of end-group. BSA adsorbed readily to both native PLG films, attaining as much as 50% surface coverage by area and was insensitive to t he type of end-group. Aging the films in water for 24 h prior to BSA exposu re decreased the hydrophobicity of the films and this in turn correlated wi th a significant decrease in the initial BSA adsorption rate. This was cons istent with the often-observed trend that surface hydrophobicity favors pro tein adsorption. In spite of the lower adsorption affinity revealed by this decreased initial adsorption rate, the final adsorbed amounts on the aged films exceeded those attained on native films, presumably due to the increa se in total surface area produced by partial PLG erosion. (C)1999 Elsevier Science BN. All rights reserved.