A simple and effective treatment can make plastics more biocompatible by altering their surface properties.

Jeffrey Schwartz and his group at Princeton University, US, work in the area of interfacial chemistry and noticed a persistent problem with polymers used in biomedical devices. When implanted in the body, the polymer comes in contact with bodily fluids and can be rejected as certain proteins and cells stick to its surface. 'The polymers' mechanical properties are great but surface issues are a stumbling block,' said Schwartz.

Schwartz and his colleague Joseph Dennes set about altering the surface of polyurethanes, a hugely versatile group of polymers used in applications as diverse as stretchy clothing to roller blade wheels. Polyurethanes are also used in medical devices such as artificial organs and synthetic vascular grafts.

The researchers reacted a polyurethane surface with zirconium tetra(tert-butoxide); the activated surface could then be used to attach various organic groups to the polymer, introducing properties for better biocompatibility. By attaching a cell-adhesive peptide to the zirconia group the scientists succeeded in encouraging fibroblast cells to grow on the polymer in vitro. Fibroblasts are known to help integrate such materials into the body. In a separate experiment, the researchers could also discourage unwanted cell growth by attaching a non-cell-adhesive group.

Kim Midwood, an expert on cell adhesion, at Imperial College London, UK, described the work as elegant, and suggested that 'given the widespread use of polyurethane polymers in medical devices, the approach could have a significant impact on the way biomaterials are designed for medical use.'

The Schwartz group is now continuing its work in this field to control exactly where the cells adhere on the polymer surface. 

Gavin Armstrong