Recognition of protein adsorption onto polymer surfaces by scanning force microscopy and probe-surface adhesion measurements with protein-coated probes

In this paper, we demonstrate in situ recognition of protein adsorption onto a polymer surface with scanning force microscopy by probe-surface adhesion measurements and topography imaging with protein-coated probes. Albumin-coated probes have been employed in studies of albumin and fibrinogen adsorption to hydrophobic polystyrene surfaces. The adhesion between force microscope probes and sample surfaces were determined using profiles of retract force-distance curves. A large adhesion force profile resulted when the force-distance curves were measured on protein-free polystyrene surfaces. When the measurements were conducted on protein-exposed polystyrene surfaces, the force-distance curves showed negligible adhesion. The same coated probes were also used for in situ topographic imaging. Applications of this novel approach are described: first, the location of boundaries of preadsorbed protein films and, second, the dynamic detection of protein adsorption onto polystyrene surfaces. Two-dimensional adhesion energy maps were obtained by employing "layered imaging". We also note that an increase in pressure exerted by the force microscope probe results in penetration of a protein film and contact of the probe with the underlying polystyrene.