Biostability of electrically conductive polyester fabrics: an in vitro study.

The biostability of a series of polypyrrole (PPy)-coated polyester fabrics was investigated in an in vitro model. PPy-coated sample fabrics were incubated in saline at 37 degrees C for 1 and 2 weeks. After each period of incubation, the surface electrical resistivity of the sample fabrics was measured to monitor the changes caused by the incubation. Redoping was then performed by immersing the sample fabrics in a 1N HCl solution at room temperature for 30 min, which was followed by another measurement of the surface resistivity. The surface morphology of the sample fabrics was observed by scanning electron microscopy. The surface chemical composition of the fabrics and the oxidation of nitrogen in PPy were measured with X-ray photoelectron spectroscopy. The surface electrical resistivity of the PPy-coated fabrics was found to increase with the progress of incubation, which was mainly caused by dedoping and uptake of oxygen. This increase was nonlinear and accelerated with time. The surface resistivity of most of the samples was retained in the range of 10(3)-10(4) Omega/square after 1 week of incubation, which was considered suitable for short-term electrical stimulation applications. Physical deterioration represented by the cracking and delamination of the PPy coating was occasionally observed on the sample fabrics showing the most significant increase of resistivity. Further improvement of the stability of conductivity is highly desirable.