Dual Suppression Effect of Magnetic Induction Heating and Microencapsulation on Ice Crystallization Enables Low-Cryoprotectant Vitrification of Stem Cell–Alginate Hydrogel Constructs

Abstract

Stem cells microencapsulated in hydrogel as stem cell-hydrogel constructs have wide applications in the burgeoning cell-based medicine. Due to their short shelf life at ambient temperature, long-term storage or banking of the constructs is essential to the "off-the-shelf" ready availability needed for their widespread applications. As a high-efficiency, easy-to-operate, low-toxicity, and low-cost method for long-term storage of the constructs, low-cryoprotectant (CPA) vitrification has attracted tremendous attention recently. However, we found many cells in the stem cell-alginate constructs (∼500 μm in diameter) could not attach to the substrate post low-CPA vitrification with ∼2 M penetrating CPAs. To address this problem, we introduced nanowarming via magnetic induction heating (MIH) of FeO nanoparticles to minimize recrystallization and devitrification during the warming step of the low-CPA vitrification procedure. Our results indicate that high-quality stem cell-alginate hydrogel constructs with an intact microstructure, high immediate cell survival (>80%), and greatly improved attachment efficiency (by nearly three times, 68% versus 24%) of the encapsulated cells could be obtained post-cryopreservation with nanowarming. Moreover, the cells encapsulated in the cell-hydrogel constructs post-cryopreservation maintained normal proliferation under 3D culture and retained intact biological function of multilineage differentiation. This novel low-CPA vitrification approach for cell cryopreservation enabled by the combined use of alginate hydrogel microencapsulation and FeO nanoparticles-mediated nanowarming may be valuable in facilitating the widespread application of stem cells in the clinic.

Cold‐Responsive Nanocapsules Enable the Sole‐Cryoprotectant‐Trehalose Cryopreservation of β Cell–Laden Hydrogels for Diabetes Treatment

“…Since β cells are easier available and capable of secreting insulin, their encapsulation in hydrogel could thus mimic real islet to regulate blood glucose. Different from the traditional islet cryopreservation methods including a high concentration of permeable cryoprotectants (pCPAs, like dimethyl sulfoxide, glycerol, ethylene glycol and propylene glycol) to prevent ice crystal damages, recent preservation methods enable efficient storage of various cells with hydrogel encapsulation, electromagnetic fields, nanoparticles, etc . Researches have been carried out and showed that by using droplet microfluidics numerous functional materials based on hydrogels could be fabricated .…”

Effects of Frozen Stromal Vascular Fraction on the Survival of Cryopreserved Fat Tissue

“…This finding may be attributed to the following: First, cryopreserved fat tissue is not only a dead filler. Some stem cells and capillary cells surrounding this tissue may have survived or become dormant temporarily, which is similar to the encapsulation and preservation of hydrogels made by Zhao [ 19 , 20 ]. With controlled cooling, stem cells and endothelial cells can be protected and retain their activity.…”

Advanced Biotechnology for Cell Cryopreservation

“…Mechanically, in addition to the cryopreservation provided by cryo-solution and alginate hydrogel, Fe 3 O 4 NPs uniformly present outside of hydrogel further suppressed devitrification and recrystallization during nanowarming process. Nanowarming was the primary reason for promoted attachment of thawed pADSCs [97]. This technology was also found to be efficient in human UC-MSCs and resulted in an improved vitrification outcome [98] (Fig.…”

“…Liu et al [97] successfully achieved low-CPA vitrification of stem cell-alginate hydrogel constructs by combining nanowarming and micro-encapsulation technology (Fig. 5a).…”