3D Printing of Conducting Polymer Hydrogels for Electrostimulation-Assisted Tissue Engineering.

Electrostimulation (ES) is at the cutting edge of contemporary medicine, effectively promoting tissue regeneration and wound healing by applying small electrical cues to stimulate specific cellular responses. The 3D printing of electronically conducting hydrogels (CHs) offers a transformative strategy for developing ES platforms. These hydrogels integrate conformal, customizable geometries, mechanical compliance, adequate electrical conductivity, and biocompatibility, enabling seamless interaction with native tissues. Nanosized inherently conducting polymers (ICPs) are promising conductive ink constituents for 3D printing, owing to their straightforward preparation, electrical conductivity, and printability. However, 3D printing of ICP-based CHs faces several challenges. Controlling the tendency of ICPs to aggregate and achieving the rheological properties required by specific 3D printing modalities are vital for achieving uniform and precise printed structures. Furthermore, post-printing solidification of ICPs often uses harsh curing conditions, e.g., high temperatures or toxic solvents, rendering encapsulation of biological components and cells infeasible. This review critically assesses strategies for synthesizing ICP nanostructures, preparing ICP-based CHs, and applicable 3D printing techniques. Progress in tissue regeneration utilizing 3D-printed ICP-based CHs as ES devices is highlighted, along with future perspectives regarding the development of bio-functional ICPs and integrated powering mechanisms for closed-loop ES systems.