Microfluidics-Generated Cryo-Fracture Resistant CNCs-Reinforced Composite Microcapsules for Enhanced Cryopreservation of Encapsulated Cells

Immunoisolated cells hold great promise for advancing cell therapeutics; however, their long-term storage remains a critical challenge due to ice formation and mechanical damage to both cells and the encapsulating matrix during cryopreservation. In this study, a cryo-fracture-resistant composite microcapsule has been developed using microfluidic technology, where sodium alginate was reinforced with cellulose nanocrystals (CNCs). The composite microcapsules were assessed for their ability to provide structural, mechanical, morphological, chemical, and thermal stability during cryopreservation. Additionally, red blood cells (RBCs) were used as a model to evaluate the ability of the optimized microcapsules to improve cell viability post-thaw. Results revealed that the microfluidic system allowed for precise control over microcapsule size and uniformity, which is crucial for even freezing and thawing. CNCs reinforced microcapsules exhibited delayed ice formation, improved ice recrystallization inhibition, and superior protection against freeze-induced deformations. Furthermore, the composite microcapsules enhanced post-thaw recovery of encapsulated RBCs and enabled the incorporation of a biocompatible cryoprotectant (trehalose). This study demonstrates a novel approach to optimizing cryopreservation techniques by leveraging the enhanced properties of composite microcapsules to mitigate cryo-injury and improve the functional recovery of encapsulated cells. These findings present a promising strategy for advancing microencapsulation-based cell therapies and broader biomedical applications.