Molecular interactions of biomolecules with surface-engineered interfaces using atomic force microscopy and surface plasmon resonance

We have used albumin-modified atomic force microscope (AFM) tips to probe i nteractions with a range of hydrophilic polymer brush surfaces and protein. Copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxi de) (PEO-PPO-PEO) (Pluronics) adsorbed onto polymer interfaces have been sh own in previous studies to modify adsorption properties of blood components [using surface plasmon resonance (SPR) and AFM]. Here we have employed pro tein-coated AFM probes to study a series of PEO PPO-PEO-coated interfaces p repared with a range of PEO and PPO molecular weights. Subsequent force-dis tance experiments have shown a good correlation between the forces of adhes ion of an albumin-functionalized AFM probe with the various PEO-PPO-PEO sur faces and the adsorption trends of albumin onto these polymeric surfaces ob served with SPR. The data suggest that the size of the hydrophobic PPO segm ent of the Pluronic is a major determinant of the polymer protein resistanc e properties. In addition, as the PEO layer density increased, a reduction of interaction force was measured because of the formation of a steric barr ier from the PEO polymer brush. Such studies suggest that AEM may be employ ed as a novel method to assess "biocompatibility" and to rapidly screen sur face-engineered surfaces with micrometer spatial resolution.