Biocompatibility of implantable electrodes coated with PVA films in the brain of rats: a histological evaluation

The biocompatibility of silicone rubber (SR) based electrodes coating with poly (vinyl alcohol) (PVA) films after implanted in the brain of rats was investigated. Twenty-two Wistar rats were used and implanted with SR electrodes and PVA/PAA films coated electrodes in left and right cerebral cortex respectively. After 4 and 8 weeks, the expression of glial fibrillary acidic protein (GFAP, a specific marker of astrocytes) and cluster of differentiation 68 (CD68, a specific marker of macrophages) were evaluated by immunohistochemistry. After 8 weeks, GFAP and CD68 expressions around PVA electrodes were significantly lower than those around SR electrodes in every stratified area (0-50 mu m, 50-100 mu m, 100 mu m from further up to the electrode-tissue interface). The results show that PVA coating can reduce the expressions of GFAP and CD68, suggesting the PVA coating can improve the biocompatibility of the SR while it is implanted in brain.