Cardiovascular diseases (CVD) are the leading global cause of mortality worldwide. Myocardial infarction (MI), a severe CVD, causes irreversible heart tissue damage and complications like arrhythmias and impaired circulation. Current therapies are inadequate, necessitating innovative regenerative approaches. Electroconductive hydrogels (ECHs), blending electrical properties with hydrogel networks, have shown promise in resynchronizing heart contractions post-MI, both in vitro and in vivo. The complex cardiac tissue microstructure requires scaffolds able to support cell alignment and maturation. Bioprinting, a cutting-edge technology, holds great potential for tissue regeneration, yet integration of electroconductive materials within bioinks remains limited despite expanding bioprinting solutions. The development of electrically conductive bioinks is pivotal for optimizing interactions with cardiac tissue, leveraging extrusion-based bioprinting to meet the heart electrical and mechanical requirements. In a recent study, new hydrogel formulations combining poly(ethylene glycol) diacrylate (PEGDA), gelatin, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), were developed demonstrating biomimetic mechanical properties and improved conductivity. In this work, these formulations were improved for 3D bioprinting of cardiac cells. Integrating Laponite, a nanosilicate thickening agent, into the PEGDA-gelatin/PEDOT:PSS hydrogels resulted in nanocomposite bioinks with increased viscosity, shear-thinning behavior and elastic recovery, crucial for extrusion-based bioprinting. 3D printing of different complex structures was tested, demonstrating high shape fidelity of printed constructs. Furthermore, the nanocomposite bioinks showed high in vitro stability in cell-culture media and improved electroconductive properties. Finally, 3D bioprinting tests showed high cell viability of both encapsulated human cardiac fibroblasts (HCFs) and H9C2 cardiomyocytes. In conclusion, the incorporation of Laponite into PEGDA-gelatin/PEDOT:PSS hydrogels yielded photo-curable nanocomposite bioinks with desirable properties for cardiac tissue 3D bioprinting. This study paves the way for further exploration and optimization of these bioinks in advancing the development of electroconductive photo-curable 3D cardiac tissue constructs.

This work was supported from European Research Council (ERC) under European Union's Horizon 2020 Research and Innovation Programme (GA: 772168).