The Adsorption of Proteins on a Polydimethylsiloxane Elastomer (PEP) and Their Antigenic Behavior

One focus of our research during the last two decades has been the immunochemistry of solid-phase immunoassay (Butler, 1991a). Contemporary solid-phase immunoassay involves the interaction of bio-molecules with, on or near, the surface of synthetic polymers composed of polystyrene, polyvinyl, nylon, methylmethacrylate, nitrocellulose, PVDF and their numerous “functionalized” variants. The native form of these polymers is intrinsically hydrophobic and readily adsorbs proteins, viruses, many peptides and nucleic acids. The practical application of biomolecular adsorption to immunoassay dates to Catt and Tregear (1967) who pioneered passive immobilization of receptors2 as a mean of simplifying the separation of bound and free ligand; this application revolutionized immunoassay. However, modern users of the technology were slow to recognize that proteins adsorbed to hydrophobic polymers do not remain in a totally native configuration although this had been shown >30 years ago (Bull, 1956; Kochwa et al., 1967; Oreskes and Singer, 1961). More recently, we have shown that only circa 20% of polyclonal and >10% of monoclonal antibodies passively adsorbed to polystyrene, remain functional (Butler et al., 1993). The subject of adsorption-induced conformational change on polymer surfaces has been reviewed elsewhere (Butler, 1991b; 1992; Butler, 1995).