Ellipsometry and radio-labelling studies on the adsorption of human serum albumin (HSA) and anti-HSA to hydrophobic silicon

Ellipsometry and radio-labelling techniques were employed to study the deposition of human serum albumin (HSA) followed by excess of mono- or polyclonal anti-HSA to methylated silicon. Adsorbed HSA, and [HSA-monoclonal anti-HSA] layers were rapidly removed by 0.1-0.5% SDS, but [HSA-polyclonal anti-HSA] layers were not. The results suggest that antigens and polyclonal antibodies crosslink on surfaces, thereby stabilizing the protein films.

Upon five repetitive and alternating exposures to excess of HSA and polyclonal anti-HSA, it was observed that the ellipsometric thickness did not increase during HSA incubations but did so during the polyclonal antibody incubations. When [HSA-polyclonal anti-HSA] multilayers were exposed to 125I-HSA, a low increased deposition with time of 125I-HSA was observed. HSA was, however, not able to remove 125I-HSA from [125I-HSA-polyclonal anti-HSA] films. The protein deposition and binding characteristics are presently not well understood but may be explained by a low HSA deposition to surface-bound polyclonal antibodies, the multiplicity of antibody binding sites on each HSA molecule, and a partial disruption of the antigen-antibody complex structure upon incubation in excess of HSA.