PEDOT:PSS Microparticles for Extrudable and Bioencapsulating Conducting Granular Hydrogel Bioelectronics

Conducting hydrogels are promising materials for forming biomimetic bioelectronic interfaces to monitor and stimulate biological activity. However, most developed materials possess fixed shapes, which limit their application to specific types of device interfaces. In non-conducting biomaterials, granular hydrogels have enabled encapsulating, conformal, and injectable biointerfaces due to unique possession of both microporosity and dynamic mechanical properties. Bringing this adaptability to conducting hydrogels would be promising for enhancing bioelectronic interfaces. However, granular hydrogels remain largely unexplored as conducting biomaterials. Methods for fabricating spherical hydrogel microparticles from the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) are presented. When densely packed, these microparticles form a conducting granular hydrogel with microporosity as well as shear-thinning and self-healing dynamic mechanical properties. The PEDOT:PSS granular hydrogel can be extruded and maintain structure post-3D printing. Modulating microparticle PSS content achieves high granular hydrogel conductivity (137 S m^-1), and microparticles exhibit excellent cytocompatibility (>98% viability). Finally, utility is demonstrated as bioencapsulating electrodes for electrophysiological monitoring. These results highlight the functionality of the PEDOT:PSS conducting granular hydrogel, which in the future may be realized as 3D printed bioencapsulating electrodes, 3D tissue engineering scaffolds for monitoring encapsulated cells, and injectable therapies for enhanced cell recruitment and tissue regeneration combined with electronic stimulation.