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 α-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 α-fetoprotein): SFM images reveal that proteins have been added onto the antibody layer.