Conclusions
This prioritized screen identified a cryopreservation solution that maintains the integrity of large alginate capsules and yields high viabilities and potency. Importantly, this formulation is serum-free, non-toxic, and can support the development of clinically translatable encapsulated cell-based therapeutics.
Methods
We employed a two-tiered screen of an initial library of 32 different cryopreservation agent (CPA) formulations composed of different cell-permeable and impermeable agents. Formulations were assayed using dark field microscopy to evaluate alginate hydrogel matrix integrity, followed by cell viability analyses and measurements of functional secretion activity.
Results
The structural integrity of large > 1 mm alginate capsules were highly sensitive to freezing and thawing in media alone but could be recovered by a number of CPA formulations containing different cell-permeable and impermeable agents. Subsequent viability screens identified two top-performing CPA formulations that maximized capsule integrity and cell viability after storage at - 80 °C. The top formulation (10% Dimethyl sulfoxide (DMSO) and 0.3 M glucose) was demonstrated to preserve hydrogel integrity and retain cell viability beyond a critical USA FDA set 70% viability threshold while maintaining protein secretion and resultant cell potency. Conclusions: This prioritized screen identified a cryopreservation solution that maintains the integrity of large alginate capsules and yields high viabilities and potency. Importantly, this formulation is serum-free, non-toxic, and can support the development of clinically translatable encapsulated cell-based therapeutics.
Supplementary Information
The online version contains supplementary material available at 10.1007/s12195-022-00739-7.