Injectable Functional Microspheres Capable of BMSC Recruitment and Osteogenic Induction for <i>In Situ</i> Bone Regeneration

Currently, bone defects remain a major challenge in clinical treatment. Recruiting target cells at the defect site and inducing them to differentiate into bone tissue are effective treatment methods. In previous studies, we used the CD271 antibody to construct bone marrow mesenchymal stem cell (BMSC) recruitment microspheres for the treatment of bone defects. However, the osteoconductivity of the microspheres themselves was poor, and the system lacked osteoinductivity, which affected the repair efficiency. In this study, we prepared submillimeter-sized porous chitosan (CS) microspheres through process optimization, and the BMSCs were able to directly adhere and proliferate on their surfaces. After the bioconjugation of the CD271 antibody, bone morphogenetic protein-2 (BMP-2) was further loaded onto the pore structure of microspheres to obtain the injectable microspheres with BMSC recruitment and osteogenic differentiation induction functions. Microspheres could efficiently recruit BMSCs through the combined action of the CD271 antibody and BMP-2 and further induce the recruited BMSCs, differentiating into osteoblasts through BMP-2, which ultimately exhibited promising bone regeneration ability in rats. We expect that the novel functional microspheres have great potential in biomedical applications for <i>in situ</i> treatment of bone defects.