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 μm) and pore (0–50 μm) 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 μm and pore size 50 μm 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.