Albumin-binding surfaces: synthesis and characterization

The nature of the proteinaceous film deposited on a biomaterial surface following implantation is a key determinant of the subsequent biological response. To achieve selectivity in the formation of this film, monoclonal antibodies have been coupled to a range of solid substrates using avidin-biotin technology. Antibody clones varied in their antigen-binding activity following insertion of biotin groups into lysine residues. Biotinylated antibodies coupled to solid substrates via an immobilized avidin bridge retained their biological activity. During immobilization of avidin a significant proportion of the protein molecules were passively adsorbed rather than covalently attached to the surface. This loosely bound material could be removed by stringent elution procedures which resulted in a surface density of 5.4 pmol avidin cm(-2). Although these conditions would be harsh enough to denature monoclonal antibodies, they did not destroy the biotin-binding activity of the residual surface-coupled avidin, enabling the subsequent immobilization of biotinylated antibodies. The two-step immobilization technique allowed the use of gentle protein modification procedures, reduced the risk of surface-induced denaturation and removed loosely bound material from the surface. The versatility of the technique encourages its application to a wide range of immobilization systems where retention of biological activity is a key requirement.