Adsorption of antibody protein onto plasma-polymerized film characterized by atomic force microscopy and quartz crystal microbalance

Adsorption of antibody protein (anti-human IgG) onto plasma-polymerized thin films (PPF) with nanoscale thickness was characterized by atomic force microscopy (AFM) and quartz crystal microbalance (QCM). The PPF surface is very flat (less than 1 nm roughness) and its properties (charge and wettability) can be easily changed while retaining the backbone structure. We focus on two types of surfaces: one is the pristine surface of hexamethyldisiloxane (HMDS) PPF (hydrophobic) and the other is an HMDS PPF surface with nitrogen-plasma treatment (hydrophilic and positive-charged surface). The AFM image showed that the antibody molecules were densely adsorbed onto both surfaces and individual antibody molecules could be observed. The QCM profiles show a corresponding tendency with the AFM images. These results indicate that the plasma polymerized film can be the suitable biointerface for the application of biosensor and bioassay.