Printable Conductive Hydrogels for Electrochemical Biosensing and Soft Bioelectronic Interfaces.

The development of flexible, conductive biomaterials is key to advancing next-generation biosensors and wearable health monitoring systems. However, combining printability, mechanical tunability, biocompatibility, and electronic performance within a single hydrogel remains a significant challenge. Here, we present a facile method to fabricate biofunctional conducting poly(ethylene glycol)-poly(pyrrole) (PEG-PPy) hydrogels via 3D-printing. The soft and flexible PEG-PPy hydrogels feature tunable mechanical properties and can be easily loaded with bioreceptors, enabling integration into sensing platforms. The composite consists of a poly(ethylene glycol) diacrylate matrix and a conductive polypyrrole filler. By optimizing photopolymerization conditions, we enable extrusion printing of complex, multi-layered structures with excellent shape fidelity (printability ≈ 1). The resulting hydrogels exhibit tunable stiffness (15-120 kPa), high cytocompatibility (>90%), and robust mechanical integrity. Integration of the hydrogel as a gate electrode in an organic electrochemical transistor yielded transconductance values comparable to conventional Ag/AgCl gates, confirming its electrochemical performance. Furthermore, embedding glucose oxidase into the hydrogel enabled enzymatic glucose sensing over a physiologically relevant range (1-100 mm). This cost-effective, multifunctional, and versatile PEG-PPy hydrogel platform offers a scalable route toward soft, flexible, printable electronic interfaces.