Microporosity engineered printable silk/graphene hydrogels and their cytocompatibility evaluations

In this work, regenerated silk fibroin (RSF)/reduced graphene oxide (rGO) hybrid ink system was fabricated in aqueous phase, extrusion printed and photocrosslinked to hydrogels with tunable physicochemical properties and cell-gel interactions. Aqueous isopropyl alcohol was used to disperse the rGO into RSF matrix, where the RSF molecules showed relatively increased radius of gyration with IPA resulting in increased pore size and water uptake capacity of the photocrosslinked hydrogels. Incorporation of IPA along with increase in rGO content systematically decreased the viscosity, contact angle and printing accuracy of RSF/rGO hybrid inks, where the ink with highest rGO content exhibited relatively loose network structure at printing shear rate. However, no secondary structural change and fibrillogenesis was observed under printing shear stress, making it a suitable system for bioprinting silk hydrogel scaffolds. In addition, increase in rGO content systematically increased the crosslink density, β-sheet content, and mechanical properties of RSF/rGO hybrid hydrogels, whereas decreased the micropore size and water uptake capacity. Moreover, with increase in rGO content, the hybrid and bioprinted hydrogels showed good biocompatibility with marginal difference in cell viability on hybrid and bioprinted gels. The developed hydrogel systems could be potentially applied for tissue engineering and other functional applications.