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 prevascularized. In this study, we aim to biofabricate a nanoreinforced hybrid cardiac patch laden with human coronary artery endothelial cells (HCAECs) with improved electrical, mechanical, and biological behavior. A safe ultraviolet (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 nanofibrous meshwork that significantly improved viscoelastic behavior and electrical conductivity of photo-cross-linked MeCol. Alginate-coated CNTs provided a nanofilamentous 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 10 days of incubation in vitro. Findings from this study deliver essential steps toward developing conductive, robust, and potentially prevascularized hybrid cardiac patches.
Keywords: 3D-printing; bioprinting; cardiac patch; cardiac tissue engineering; hybrid scaffold; hydrogel; nanotubes; photo-cross-linking.