C-13: Application of hydrogel in cryopreservation as a novel cryoprotectant, encapsulation and single-cell-based functional sensing material

Abstract

Some challenges still remain in cryopreservation and cytotherapy, including (1) cryoinjury due to intracellular ice formation may cause cell loss during cryopreservation. Non-freezing preservation may be achieved by vitrification with ultra-high cooling rate or cryoprotectant concentration; however, this is unfeasible or cytotoxic. (2) Immune rejection response may happen to the transplanted cell products. Microencapsulation of the transplanted cells has been used to immobilize xenograft cells in the last few decades. However, the progress in this field has not met expectations yet. The major problems include biocompatibility, possible function loss during encapsulation, mechanical and chemical stability of the encapsulation membranes, generation reproducibility of the uniform capsules, suitable membrane permeability that protects the implants from immune response of the host and simultaneously permits passage of nutrients and secretions. (3) A fast, simple and reliable quality control assay for the cells along the whole process is desirable. Especially, single-cell-based quality assessment has many advantages. In this work, application of hydrogel (application for rat islet as the example) was studied to address the three challenges listed above. A microfluidic device was applied to generate individual-cell based microencapsulation with uniformity and reproducibility. Meanwhile, biosensing agent was embedded in the hydrogel layer for single-cell-based biosensing, which can act as a simple quality control assay in cryopreservation and cytotherapy. It was found that glass transition of hydrogel may be achieved by tuning the crosslinking network density and water content. This implies that hydrogel can be potentially a novel cryoprotectant for non-freezing preservation purposes. In conclusion, hydrogel can serve as a cryoprotectant, immune barrier, and biosensing agent carrier. Further investigations are needed, especially the properties of hydrogel as cryoprotectant, which may lead to many striking and interesting applications in cryobiology.