Light-based vat-polymerization of electroconductive gelatin methacryloyl composite hydrogels for soft tissue interfacing

Conductive hydrogels have emerged as promising materials for soft tissue interfacing by combining tissue-like mechanical compliance with electrical conductivity, thereby enabling improved electrical communication with electroactive biological tissues. This work presents an electroconductive composite hydrogel fabricated via light-based vat-polymerization by integrating a choline-based bio-ionic liquid (IL) with gelatin methacryloyl (GelMA). The resulting hydrogels demonstrate tunable conductivity, structural integrity, and high print fidelity when fabricated using digital light processing (DLP) light-based 3D printing. Electrical conductivity was optimized at 20% v/v IL concentration, with the hydrogels demonstrating stable performance for over 28 days. A food-grade photoabsorber was integrated into the formulation to improve DLP resolution and was effectively removed after printing process. The hydrogels supported the human mesenchymal stem cells' viability and proliferation, confirming their cytocompatibility. They also promoted enhanced maturation of primary neurons, demonstrating a supportive microenvironment for neural cells. In vivo implantation of indocyanine green-loaded hydrogels exhibited sustained stability and robust retention of signal over a period of 4 weeks, with histological analysis indicating seamless integration with surrounding tissues. Impedance spectroscopy at both gut and spinal cord interfaces illustrated that GelMA/IL composites achieved the lowest impedance across a range of frequencies, outperforming both GelMA-only and tissue-only conditions. Collectively, these findings position light-based vat-polymerized electroconductive composites as a promising platform for the development of anatomically conformal materials tailored for soft tissue interfacing.