3D-printed vascularized biofunctional scaffold for bone regeneration

3D-printed biofunctional scaffolds have promising applications in bone tissue regeneration. However, the development of bioinks with rapid internal vascularization capabilities and relatively sustained osteoinductive bioactivity is the primary technical challenge. In this work, we added rat platelet-rich plasma (PRP) to a methacrylated gelatin (GelMA)/methacrylated alginate (AlgMA) system, which was further modified by a nanoclay, laponite (Lap). We found that Lap was effective in retarding the release of multiple growth factors from the PRP-GelMA/AlgMA (PRP-GA) hydrogel and sustained the release for up to 2 weeks. Our in vitro studies showed that the PRP-GA@Lap hydrogel significantly promoted the proliferation, migration, and osteogenic differentiation of rat bone marrow mesenchymal stem cells, accelerated the formation of endothelial cell vascular patterns, and promoted macrophage M2 polarization. Furthermore, we printed hydrogel bioink with polycaprolactone (PCL) layer-by-layer to form active bone repair scaffolds and implanted them in subcutaneous and femoral condyle defects in rats. In vivo experiments showed that the PRP-GA@Lap/PCL scaffolds significantly promoted vascular inward growth and enhanced bone regeneration at the defect site. This work suggests that PRP-based 3D-bioprinted vascularized scaffolds will have great potential for clinical translation in the treatment of bone defects.