Under buffer SFM observation of immunospecies adsorbed on a cyano grafted silicon substrate

Scanning force microscopy (SFM) in contact mode and in liquid medium has been employed to study immunospecies layers adsorbed on a silicon wafer. The silicon wafer has been grafted with a cyanosilane monolayer in order to create a surface with strong adhesive properties which prevent proteins being swept by the scan of the SFM tip. The force curves reveal that the adhesive force has been increased by a factor six without roughness modification (< 1 nm). After the incubation of the surface in a monoclonal antibody (mouse anti-human alpha-fetoprotein IgG) solution, SFM surface images suggest an homogeneous layer composed by ellipsoidal objects (40-60 nm in diameter, 6-13 nm in height). The substrate was moreover incubated in an antigenic solution (human alpha-fetoprotein): SFM images reveal that proteins have been added onto the antibody layer.