Self-assembly of antibody fragments and polymers onto gold for immunosensing

Surface plasmon resonance, SPR has been used to compare the attachment of antibody F(ab)2 and Fab′-fragments of anti-human IgG onto gold. Antibody Fab′-fragments directly coupled onto gold give a three-fold response to human IgG (hIgG) to that of F(ab)2-fragments. The Fab′-fragment layer could be regenerated with a glycine-HCl solution. The F(ab)2-fragment layer, on the other hand, could not be regenerated. This indicates a difference in immobilisation of the fragments. The F(ab)2-fragments were adsorbed on the surface and thus randomly oriented. The much higher binding capacity and the ability to regenerate the Fab′-fragment layer indicates that the Fab′-fragments were site-directly immobilised on the gold surface. When antibody Fab′-fragments were allowed to interact with the surface and the remaining free space in between the antibodies were filled with the protein repellent polymer the NSB was considerably reduced.