Stem cell-laden injectable hydrogel microspheres for cancellous bone regeneration

Injection of cell-laden hydrogel microspheres is a minimally invasive method for tissue regeneration. However, microspheres are usually limited by structural heterogeneity, uneven size, low cell loading capacity, and poor cell survival rate. We devised a microfluidics synchronous cross-linked technology to obtain injectable homogenous porous microspheres of desired particle (50-400 mu m) and pore (0-50 mu m) size by adjusting the flow rate and concentration of gelatin methacrylamide (GelMA). The synchronous cross-linking controlled the strength of cross-linking and prevented fusion and uneven cross-linking. The freeze-dried microspheres of particle size 300 mu m and pore size 50 mu m rapidly adsorbed murine bone marrow-derived stem cells (BMSCs) and maintained their viability and osteogenic potential in vitro. In addition, the cell-loaded porous microspheres promoted tissue regeneration when injected locally into a murine bone defect model. Our results show that hydrogel microspheres generated by the microfluidics synchronous cross-linked technology are stable and biocompatible, and have strong regenerative potential when loaded with stem cells.