Generation of cell-laden GelMA microspheres using microfluidic chip and its cryopreservation method

Gelatin methacrylate (GelMA) hydrogels have been widely used in tissue engineering because of their excellent biological and physical properties. Here, we used a microfluidic flow-focusing chip based on polymethyl methacrylate to fabricate cell-laden GelMA hydrogel microspheres. Structures of the throat region and photo crosslinking region on the chip, flow rate ratio of GelMA and oil phase, and GelMA concentration were optimized to obtain the stable and suitable size of microspheres. Cell-laden GelMA microspheres can be cryopreserved by slow freezing and rapid freezing. The survival rate of encapsulated cells after rapid freezing was significantly higher than that of unencapsulated cells. There was no significant difference between the results of the rapid freezing of encapsulated cells with 5% DMSO and the traditional slow freezing of suspended cells with 10% DMSO. It demonstrates the possibility that GelMA hydrogel itself can replace some of the cryoprotective agents and has some protective effect on cells. Our study provides new ideas to optimize GelMA hydrogels for cell cryopreservation, facilitating the off-the-shelf availability of tissue-engineered constructs.