Biocompatibility of polyaniline

Both the non-conducting polyaniline, emeraldine base, and its conducting form, polyaniline hydrochloride, were tested for their biocompatibility in terms of skin irritation, sensitization and cytotoxicity performed on human immortalized non-tumorigenic keratinocyte and human hepatocellular carcinoma cell lines. The testing was carried out on extracts of polyaniline powders in agreement with requirements of international standards applicable for testing of medical devices. The results can be hence generally employed in all types of materials and devices containing polyaniline in various concentrations. The study confirmed that polyaniline has not induced any sensitization and skin irritation either. In contrast, both polyaniline forms showed considerable cytotoxicity, which was higher for polyaniline hydrochloride compared to polyaniline base and was observed on both cell lines. Differences between cytotoxicity found on human immortalized non-tumorigenic keratinocyte cell line and human hepatocellular carcinoma cell line were attributed to variability in specific metabolic capabilities of the respective cell lines. Significant reduction of cytotoxicity was achieved through deprotonation and reprotonation procedure, used as an additional purification step after polymer synthesis. Accordingly, the cytotoxicity is thus caused rather by the reaction by-products and residues than by polyaniline itself.