Synthesis and 3D printing of conducting alginate–polypyrrole ionomers

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Hydrogels composed of calcium cross-linked alginate are under investigation as bioinks for tissue engineering scaffolds due to their variable viscoelasticity, biocompatibility, and erodibility. Here, pyrrole was oxidatively polymerized in the presence of sodium alginate solutions to form ionomeric composites of various compositions. The IR spectroscopy shows that mild base is required to prevent the oxidant from attacking the alginate during the polymerization reaction. The resulting composites were isolated as dried thin films or cross-linked hydrogels and aerogels. The products were characterized by elemental analysis to determine polypyrrole incorporation, electrical conductivity measurements, and by SEM to determine changes in morphology or large-scale phase separation. Polypyrrole incorporation of up to twice the alginate (monomer versus monomer) provided materials amenable to 3D extrusion printing. The PC12 neuronal cells adhered and proliferated on the composites, demonstrating their biocompatibility and potential for tissue engineering applications.