Neil P. Desai

Solution technique to incorporate polyethylene oxide and other water-soluble polymers into surfaces of polymeric biomaterials

A simple solution technique was used to incorporate polyethylene oxide (PEO, of 5000, 10,000, 18,500, and 100,000 g/mol) and other water-soluble polymers such as polyvinylpyrrolidone and polyethyl oxazoline into the surfaces of commonly used biomedical polymers such as polyethylene terephthalate, a polyurethane (Pellethane 2363-80AE), and polymethylmethacrylate. The presence of the water-soluble polymers on these surfaces was verified by using contact angle analysis and ESCA. Protein adsorption studies, fibroblast adhesion assays, and whole blood perfusions over these polymers showed that the surface modified with PEO 18,500 was the most effective in reducing all the tested biological interactions. It was concluded that PEO 18,500 had a chain length that was optimal, using this technique for surface incorporation, to reduce protein adsorption and hence prevent protein-mediated biological interactions.

Surface-immobilized polyethylene oxide for bacterial repellence

Polyethylene terephthalate films were surface-modified with polyethylene oxide (18,500 g/mol) using a solution technique described previously. These films were investigated for their resistance to bacterial adhesion. Three bacterial strains most commonly associated with implant infections, Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa, were cultured in tryptic soya broth, human plasma and human serum on the polymeric substrates. Significant reductions (between 70 and 95%) in adherent bacteria were observed on the polyethylene oxide-modified substrates compared to the untreated control polyethylene terephthalate. Surface modification with polyethylene oxide may reduce the risk of implant-associated infections. Plasma fibrinogen was observed to play an important role in the adhesion of all three of these species on both the polyethylene oxide-modified and control polyethylene terephthalate materials.

Tissue response to intraperitoneal implants of polyethylene oxide-modified polyethylene terephthalate

Polyethylene terephthalate films surface modified with polyethylene oxide of mol wt 18,500 g/mol (18.5 k) by a previously described technique, were implanted in the peritoneal cavity of mice, along with their respective untreated controls, for periods of 1-28 d. The implants were retrieved and examined for tissue reactivity and cellular adherence. The control polyethylene terephthalate surfaces showed an initial inflammatory reaction followed by an extensive fibrotic response with a mean thickness of 60 microns at 28 d. By contrast, polyethylene oxide-modified polyethylene terephthalate showed only a mild inflammatory response and no fibrotic encapsulation throughout the implantation period: at 28 d a cellular monolayer was observed. Apparently either the polyethylene oxide-modified surface was stimulating less inflammation, which was in turn stimulating less fibroblastic overgrowth, or the cellular adhesion to the polyethylene oxide-modified surface was too weak to support cellular multilayers.