Atomic force microscopy has been utilized to probe, at a molecular level, the interaction between purified pig gastric mucin (PGM) and a mucoadhesive cationic polymer, chitosan (sea cure 210+), with a low degree (approx. 11%) of acetylation. Images were produced detailing the structures of both PGM and chitosan in 0.1 M acetate buffer (pH 4.5), followed by the complex of the two structures in the same buffer. PGM in 0.1 M acetate buffer revealed long linear filamentous structures, consistent with earlier electron microscopy and scanning tunnelling micoscopy studies. The chitosan molecules also adopted a linear conformation in the same buffer, although with a smaller average length and diameter. They appeared to adopt a stiff-coil conformation consistent with earlier hydrodynamic measurements. The complexes formed after mixing PGM and chitosan together revealed large aggregates. In 0.1 M ionic strength buffer they were of the order of 0.7 microm in diameter, consistent with previous electron microscopy studies. The effect of ionic strength of the buffer on the structure of the complex was also studied and, together with molecular hydrodynamic data, demonstrates that the interaction is principally electrostatic in nature.

Surface enrichment phenomena are important in determining the surface organization of fabricated biomaterials and other polymeric materials. Enrichment can govern both the surface chemistry and morphology of such surfaces. Here, we present new information on the surface enrichment of components from a biodegradable polymer blend composed of poly(sebacic anhydride) (PSA) and poly(dl-lactic acid) (PLA). This information, derived by phase-detection imaging atomic force microscopy (AFM), defines both the surface chemistry and morphology. We demonstrate that phase-detection imaging can distinguish between microdomains of PSA and PLA in blends of these biodegradable polymers. Contrast between these two polymers is achieved even when the microdomains cannot be distinguished on surface topography images. The relationship between the force of tapping of the AFM probe on the polymer surface and the image contrast mechanism is investigated. In addition to detecting chemical and mechanical variations on polymer blend surfaces, phase-detection imaging can improve the resolution and contrast of images on single-component films. This is demonstrated by the identification of lamellae with widths of less than 5 nm within PSA spherulites.

Water insoluble Zn-insulin can be formulated as a stable, biologically active nanometer-sized peptide particle dispersion using wet media milling technology.

We have used albumin-modified atomic force microscope (AFM) tips to probe interactions with a range of hydrophilic polymer brush surfaces and protein. Copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) (Pluronics) adsorbed onto polymer interfaces have been shown in previous studies to modify adsorption properties of blood components [using surface plasmon resonance (SPR) and AFM]. Here we have employed protein-coated AFM probes to study a series of PEO-PPO-PEO-coated interfaces prepared with a range of PEO and PPO molecular weights. Subsequent force-distance experiments have shown a good correlation between the forces of adhesion of an albuminfunctionalized AFM probe with the various PEO-PPO-PEO surfaces and the adsorption trends of albumin onto these polymeric surfaces observed with SPR. The data suggest that the size of the hydrophobic PPO segment of the Pluronic is a major determinant of the polymer protein resistance properties. In addition, as the PEO layer density increased, a reduction of interaction force was measured because of the formation of a steric barrier from the PEO polymer brush. Such studies suggest that AFM may be employed as a novel method to assess "biocompatibility" and to rapidly screen surface-engineered surfaces with micrometer spatial resolution.

Atomic force microscopy has been utilized to probe, at a molecular level, the interaction between purified pig gastric mucin (PGM) and a mucoadhesive cationic polymer, chitosan (sea cure 210j), with a low degree (approx. 11 %) of acetylation. Images were produced detailing the structures of both PGM and chitosan in 0.1 M acetate buffer (pH 4.5), followed by the complex of the two structures in the same buffer. PGM in 0.1 M acetate buffer revealed long linear filamentous structures, consistent with earlier electron microscopy and scanning tunnelling micoscopy studies. The chitosan molecules also adopted a linear conformation in the same buffer, although with a smaller average