Cell-microsphere based living microhybrids for osteogenesis regulating to boosting biomineralization

Abstract Biomineralization-based cell-material living composites ex vivo showed great potential for living materials construction and cell regulation. However, cells in scaffolds with unconnected pores usually induce confined nutrient transfer and cell–cell communications, affecting the transformation of osteoblasts into osteocytes and the mineralization process. Herein, the osteoblast-materials living hybrids were constructed with porous PLLA microspheres using a rational design, in which cell-based living materials presented an improved osteoblast differentiation and mineralization model using rationally designed cell-microsphere composites. The results indicated that the microfluidic-based technique provided an efficient and highly controllable approach for producing on-demand PLLA microspheres with tiny pores (<5 μm), medium pores (5–15 μm) and large pores (>15 μm), as well as further drug delivery. Furthermore, the simvastatin (SIM)-loaded porous PLLA microsphere with ε-polylysine (ε-PL) modification was used for osteoblast (MC3T3-E1) implantation, achieving the cell-material living microhybrids, and the results demonstrated the ε-PL surface modification and SIM could improve osteoblast behavior regulation, including cell adhesion, proliferation, as well as the antibacterial effects. Both in vitro and in vivo results significantly demonstrated further cell proliferation, differentiation and cascade mineralization regulation. Then, the quantitative polymerase chain reaction or histological staining of typical markers, including collagen type I, alkaline phosphatase, runt-related transcription factor 2 and bone morphogenetic protein 2, as well as the calcium mineral deposition staining in situ, reconfirmed the transformation of osteoblasts into osteocytes. These achievements revealed a promising boost in osteogenesis toward mineralization at the microtissue level by cell-microsphere integration, suggesting an alternative strategy for materials-based ex vivo tissue construction and cell regulation, further demonstrating excellent application prospects in the field of biomineralization-based tissue regeneration.