UV-assisted 3D bioprinting of nano-reinforced hybrid cardiac patch for myocardial tissue engineering

Biofabrication of cell supportive cardiac patches that can be directly implanted on myocardial infarct is a potential solution for myocardial infarction repair. Ideally, cardiac patches should be able to mimic myocardium extracellular matrix for rapid integration with the host tissue, raising the need to develop cardiac constructs with complex features. In particular, cardiac patches should be electrically conductive, mechanically robust and elastic, biologically active and pre-vascularized.. In this study, we aim to biofabricate a nano-reinforced hybrid cardiac patch laden with human coronary artery endothelial cells (HCAECs) with improved electrical, mechanical and biological behavior. A safe UV exposure time with insignificant effect on cell viability was identified for methacrylated collagen (MeCol) micropatterning. The effects of carboxyl functionalized carbon nanotubes (CNTs) on MeCol and alginate matrix morphology, mechanical properties, electrical behavior and cellular response were investigated at different CNT mass ratios. A UV-integrated 3D-bioprinting technique was implemented to create hybrid hydrogel constructs consisting of CNT-incorporated alginate framework and cell-laden MeCol. The compressive modulus, impedance and swelling degree of hybrid constructs were assessed over 20 days of incubation in culture medium at 37C for different CNT mass ratios. The HCAEC viability, proliferation and differentiation in the context of the bioprinted hybrid constructs were assessed over 10 days in-vitro. The functionalized CNTs provided a highly interconnected nano-fibrous meshwork that significantly improved viscoelastic behavior and electrical conductivity of photo-cross-linked MeCol. Alginate-coated CNTs provided a nano-filamentous network with fiber size of ~25 – 500 nm, improving not only electrical and mechanical properties but also HCAEC attachment and elongation compared to pristine alginate. The CNT-reinforced 3D-printed hybrid constructs presented significantly higher stiffness and electrical conductivity particularly in the physiologically relevant frequency range (~5 Hz). The CNT-reinforced hybrid implants maintained a significantly higher swelling degree over 20 days of culturing compared to CNT-free hybrid constructs. For a selected CNT mass ratio, HCAECs presented significant cellular proliferation, migration and differentiation (lumen-like formation) over ten days of incubation in-vitro. Findings from this study deliver essential steps toward developing conductive, robust, and potentially pre-vascularized hybrid cardiac patches.