Microencapsulation technology based on sodium alginate hydrogels can be used to optimize freezing and rewarming procedures and to reduce cryo-damage to cells and tissues. In this paper

the morphology of oocytes in different concentrations (0.5%

1%

1.5%

and 2%) of sodium alginate hydrogels was first observed to determine the safe concentration for their encapsulation. Secondly

the crystallization temperature and crystallization behavior of sodium alginate hydrogels with different concentrations (0.5%

1%

1.5%

2%) were systematically investigated using cryo-microscopy

and the morphology and crystallization of oocytes were compared when they were cooled down/retempered in the base solution

cryoprotectant solution. Finally

the freezing effect of sodium alginate antifreeze hydrogel encapsulated oocytes prepared by solvent replacement type and physical mixing type were compared. The results showed that oocytes maintained their overall morphology and volume better in sodium alginate gels at 0.5% and 1% concentrations. Furthermore

oocytes in both the 1% sodium alginate group and the cryoprotectant solution group of 12.5% DMSO + 12.5% EG + 0.5 M trehalose did not produce intracellular ice during the cooling process；Additionally

compared with the physical mixture

oocytes in the solvent replacement group of hydrogels did not produce intracellular ice during the cooling process

and the cells retained their normal morphology after rewarming.