Oxidized alginate-gelatin nanocomposite hydrogels incorporating MXene nanosheets for 3D bioprinting

Electrically conductive hydrogels (ECHs) and electrical stimulation effectively regulate osteoblast attachment, proliferation, and differentiation, thus triggering bone tissue regeneration. Here, an alginate dialdehyde-gelatin (ADA-GEL) based hydrogel is modified with an electrically conductive and osteogenic 2D nanomaterial, namely MXene, to produce degradable and 3D printable nanocomposite hydrogels exhibiting electrical conductivity. The effect of MXene filler content on resulting hydrogel characteristics such as morphology, mechanical and electrical properties, swelling and degradation behavior was investigated comprehensively. The results indicate tailorable properties depending on MXene concentration, thus opening a library of ADA-GEL-MXene nanocomposite hydrogels. Moreover, the suitability of ADA-GEL-MXene hydrogels for 3D printing of grid-like scaffolds of up to 10 layers was shown. Additional 3D bioprinting studies demonstrated the applicability of the nanocomposite hydrogels as bioinks for 3D bioprinting of MG-63 osteoblast-like cells. Although the electrical conductivity was increased at higher MXene concentrations, compromised cell behavior was observed. This points to the conclusion that the concentration of MXene nanosheets must be carefully chosen depending on the required properties. Taken together, the presented ADA-GEL-MXene composite hydrogels exhibit significant potential for 3D bioprinting in bone tissue engineering and could be employed for the electrical stimulation of bone cells in the future.