In Situ Encapsulation of Postcryopreserved Cells Using Alginate Polymer and Zwitterionic Betaine.

Currently, the state-of-the-art cryoprotectants for cell cryopreservation have bottleneck problems (such as cytotoxicity), which place enormous logistical limitations to the development of regenerative medicine. In this work, a first alginate polymer-based approach for human chondrocyte cryopreservation is reported. Combined with zwitterionic betaine, a natural osmoprotectant to offer intracellular protection, this alginate polymer-based approach can achieve ∼90% cryopreservation efficiency. Because of the biocompatibility of alginate polymer and betaine, this approach can easily retrieve the post-thaw cells without traditional multistep cryoprotectant washing procedures, which is highly favorable to cell therapy. Meanwhile, because of the feasible and mild gelation process of alginate polymer, this approach can also directly encapsulate the post-thaw cells into hydrogels without cryoprotectant removal, which is highly useful to tissue engineering. Moreover, these hydrogels exhibit tunable mechanical properties and can form variable shapes and sizes of scaffolds to inject into the patient's defect sites. After encapsulating post-thaw cells, these hydrogels can maintain high cell viability (∼90%) and normal cellular functions for at least 14 days. This work provides a step-change in cryopreservation of cells to be directly used in cell-based applications and may realize promising cellular therapy products that can integrate preservation with clinical practice.