Surface modification of thin polyion complex film for surface plasmon resonance immunosensor

A surface plasmon resonance-based immunosensor was developed by modifying the surface of a thin polyion complex film consisting of poly-l-lysine and poly-styrenesulfonate. The suppression of non-specific protein adsorption was investigated by changing the blend ratio of the two polymers. The protein adsorption fell to less than 10% that of an unmodified surface when the poly-l-lysine to ratio was 4:6. The binding constant between immobilized B-type natriuretic peptide on the polyion complex film and its antibody was calculated to be 1.1 × 108 (M−1), which is a satisfactory level for immuno-affinity on a solid surface. We also obtained stable and reproducible responses without losing the affinity on the polyion complex film.