Electroconductive and highly biocompatible PEDOT- and polypyrrole-alginate–gelatin hydrogels with enhanced electrochemical performance for biointerfaces

, and current injection limits reaching 4 mA, comparable to platinum electrodes. Swelling studies indicated that PEDOT-modified hydrogels achieved 41-56% swelling after 24 hours. PPy-based hydrogels swelled to approximately 97% and hybrid systems showed behavior dependent on their composition. All conductive formulations demonstrated improved long-term stability compared to pristine Alg-GEL, which gradually lost mass over 28 days of incubation. In contrast, hydrogels containing PEDOT and PPy maintained nearly constant wet weight, consistent with the formation of interpenetrating networks that prevented polymer degradation and leaching. Biological evaluation with NIH3T3 fibroblasts showed that all hydrogels were cytocompatible. PPy-only and PPy-PEDOT hybrids supported higher metabolic activity and more attached and spread cells after 7 days compared to Alg-GEL, while PEDOT-only samples showed similar or slightly reduced cell activity. These results confirm excellent cytocompatibility and suggest that PPy-rich domains improve cell-material interactions. Overall, PEDOT- and PPy-modified Alg-GEL hydrogels offer high conductivity, softness, electrochemical stability, long-term durability, and biocompatibility, creating a versatile and adjustable platform for next-generation soft neural interfaces.