Characterization of IgG Langmuir–Blodgett films immobilized on functionalized polymers

The bioactivity of anti-human IgG Langmuir–Blodgett (LB) films, the non-specific adsorption of protein and the topography of anti-IgG LB films have been studied for application in immunosensors. The antibody (AB) LB films were horizontally deposited on glass and functionalized polymers, such as carboxy-poly(vinyl chloride) (PVC-COOH), chloropropyl and aminopropyl sol–gel. The LB films were characterized by means of ellipsometry, atomic force microscopy (AFM) and bicinchoninic acid (BCA) protein test. The interpretation of ellipsometric data was performed using a one-layer model. Non-specifically adsorbed protein was desorbed by washing the IgG film in 0.5 M NaCl, 2 M NaCl and 1% N-cetyl-N,N,N-trimethylammoniumbromide detergent solution resulting in a 50% reduction of the film thickness. The mean thickness of an anti-IgG film on glass measured by ellipsometry, PVC-COOH and aminopropyl sol–gel was 9±2, 11±1 and 23±8 nm, respectively. According to the BCA test 6–8 μg antibody (AB) per slide was bound to the functionalized polymers, but only 3 μg AB per slide was adsorbed on glass. The average distance of anti-IgG granules as indicated by AFM measurements on PVC-COOH, chloropropyl and aminopropyl sol–gel was 42±20, 34±3 and 23±4 nm. The average distance of granular AB structures on glass, however, was 150±50 nm.