Nanomaterial-modified bioinks for DLP-based bioprinting of bone constructs: Impact on mechanical properties and mesenchymal stem cell function

3D printing technologies offer tremendous potential to produce patient-specific implants and treat critical-sized bone defects, which vary in size, shape, and clinical requirements. Despite advancements in 3D printing of biomaterial-based bone constructs, they often lack biologically active material. For larger-sized bone implants, early biologization and vascularization are essential. In this context, bioprinting technologies enable the integration of vital cells or active growth factors into 3D-printed constructs, while the integration of nanomaterials enables material-mediated functionalization of the bioink. To date, such bioink modifications with nanomaterials have rarely been reported for digital light processing (DLP) bioprinting technology. Furthermore, there is a notable lack of direct comparative studies on the impact of nanomaterials on cellular processes. In this study, we assessed and compared graphene oxide (GO)- and calcium phosphate (CaP)-modified bioinks for DLP bioprinting of methacrylated gelatin (GelMa)-based bone constructs. After printing, the impact of bioinks on cell distribution, viability, cell proliferation, and differentiation, as well as the mechanical and structural properties of constructs, was evaluated. In comparison to commercial bioinks, cell viability was higher in the established GelMa bioinks. Morphological data and DNA quantification indicate the highest cell vitality and proliferation over time in basic GelMa bioink. CaP-modified GelMa bioink displayed the highest differentiation of human mesenchymal stem cells (hMSCs), in terms of osteogenic gene expression and calcium deposition. Conversely, GO increased the Young’s modulus of the material, affecting cell morphology. Overall, the direct comparison of nanomaterials suggests diverse effects in functionalizing DLP-printed bone constructs containing living osteogenic cells.