Biomineral/VEGF-functionalized fiber - enhanced 3D printed GelMA hydrogel to facilitate bone regeneration through osteogenesis and angiogenesis modulation

Three-dimensionally (3D) printed hydrogels face significant challenges in promoting osteogenesis and angiogenesis for bone tissue engineering. In this study, we designed a bioactive 3D-printed hydrogel to enhance bone regeneration through osteogenesis and angiogenesis modulation. An enzymatic mineralization strategy was proposed to develop biomineral/vascular endothelial growth factor (VEGF)-functionalized poly (L-lactic acid) (PLLA) micro-nanofibers (m-PLLA@VEGF). These micro-nanofibers were incorporated into gelatin methacryloyl (GelMA) bioink to develop GelMA/m-PLLA@VEGF hydrogel scaffold. The m-PLLA@VEGF micro-nanofibers provided multiple benefits. Specifically, they improved the rheological properties of the GelMA bioink and mechanical properties of the hydrogel, and promoted osteogenesis and angiogenesis of the hydrogel scaffold. The resulting GelMA/m-PLLA@VEGF hydrogel scaffold effectively promoted osteogenesis by enhancing osteoblastrelated expression and mineralized matrix deposition, aided by the sustained release of biominerals (Ca and P ions). It also significantly enhanced endothelial cell proliferation, scratch wound healing, and the expression of angiogenesis-related genes. When implanted in a critical-sized rat calvarial bone defect model, the composite hydrogel scaffold facilitated bone regeneration through the synergistic modulation of angiogenesis and osteogenesis. Overall, this work presented an innovative approach for developing functionalized micro-nanofibers, with the enhanced bioactive hydrogel showing significant potential for bone regeneration.