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 adsorptio n onto a polymer surface with scanning force microscopy by probe-surfa ce adhesion measurements and topography imaging with protein-coated pr obes. Albumin-coated probes have been employed in studies of albumin a nd fibrinogen adsorption to hydrophobic polystyrene surfaces. The adhe sion between force microscope probes and sample surfaces were determin ed using profiles of retract force-distance curves. A large adhesion f orce profile resulted when the force-distance curves were measured on protein-free polystyrene surfaces. When the measurements were conducte d on protein-exposed polystyrene surfaces, the force-distance curves s howed negligible adhesion. The same coated probes were also used for i n situ topographic imaging. Applications of this novel approach are de scribed: first, the location of boundaries of preadsorbed protein film s and, second, the dynamic detection of protein adsorption onto polyst yrene surfaces. Two-dimensional adhesion energy maps were obtained by employing ''layered imaging''. We also note that an increase in pressu re exerted by the force microscope probe results in penetration of a p rotein film and contact of the probe with the underlying polystyrene.