ADSORPTION OF SERUM ALPHA-1-MICROGLOBULIN ONTO BIOMATERIALS

The adsorption of alpha-1-microglobulin (alpha-1-m) from serum to the surface of polymers with different physicochemical properties was inve stigated. Enzyme-linked immunosorbent assay showed binding of this pro tein to the surface of polystyrene (PS), polyvinyl chloride (PVC) and a polyurethane, Chronoflex, after water washing, but only trace levels could be detected on two polymethacrylate derivatives, polymethyl met hacrylate and poly(2-hydroxyethyl methacrylate). alpha-1-m was selecti vely desorbed from the five materials by sequential washes of serum-co nditioned surfaces with isopropanol solutions at increasing concentrat ions. The presence of alpha-1-m in the washing supernatants was detect ed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS- PAGE). The relative binding strength of alpha-1-m to each surface was evaluated as the isopropanol (IsoPOH) concentration required to desorb the protein from that surface. Analysis of bound proteins by SDS-PAGE conclusively demonstrated the binding of a range of serum proteins, i ncluding alpha-1-m, to all polymer systems, but with varying binding s trengths. The majority of protein was removed by water washing for the polymethacrylate polymers, while varying concentrations of IsoPOH wer e required to desorb proteins from PS, PVC and Chronoflex. There was a correlation between the hydrophobic nature of the material, determine d by water contact angle measurements, and adsorption of alpha-1-m. Im munoblotting of isopropanol-eluted proteins by alpha-1-m antibodies sh owed the positive staining of a 29 kDa protein as well as selected ban ds within a molecular weight range of 40-200 kDa, suggesting the adsor ption of this protein as both free and complexed forms. The ability of alpha-1-m to adsorb on to material surfaces and to participate in eve nts relevant to the biocompatibility of a polymer, such as bacterial i nfection or inflammation control, suggests the need for further charac terization of the properties of this protein. (C) 1998 Chapman & Hall.