Improving cryopreservations strategies and developing optimal formulations of cryoprotectants is a high priority for the cell therapy and medical fields. A recent study from the Royal Free Hospital in London, UK investigated the toxicity associated with the exposure of cord blood samples to DMSO. The authors carried out cell viability and in vitro functional assays in fresh and post-thaw cord blood samples, and determined that the optimal concentration of DMSO for cryopreserved cord blood is in the 7.5 – 10% range, while the maximum exposure time should be limited to <1 h prior to freezing and 30 min post-thaw.
Elsewhere, new strategies for cryopreservation have appeared. The lab of Francisco del Monte at the Materials Science Institute of Madrid described the development, in the journal ACS Applied Materials and Interfaces, of liquid marbles encapsulating fibroblasts that are used for cryopreserving the encapsulated cells. Liquid marbles are spherical constructs – they are typically described as droplets – made of polymeric materials surrounding an aqueous core. They have been used for many applications. In the paper, the authors encapsulated murine L929 fibroblasts inside liquid marbles made up of poly(tetrafluoroethylene) and found that the cells were well cryopreserved in such a construct adhesion, morphology, viability, proliferation, and cell cycle. More studies are needed to further understand and optimize the utility of such processes, but this is one of the earliest examples of such a system.
Encapsulation was also employed in a new study on cryopreservation by a Jose Luis Pedraz’ lab at the University of the Basque Country in Spain. The authors tested a number of cryoprotectant solutions combining DMSO, glycerol and trehalose on encapsulated mesenchymal stem cells genetically modified to secrete erythropoeitin. Cells were encapsulated in multi-cell particles and were cryopreserved either with DMSO, glycerol or trehalose alone or a combination of cryoprotectants. The authors found that DMSO at a concentration of 10% displayed the best viability and erythropoietin secretion profile compared to the other cryoprotectant solutions. This is not, however, meant to exclude other compositions as being suitable for further development and optimization, considering the nature of this study was limited.
Some of these studies highlight that encapsulation, but more generally, novel approaches for cryopreservation, may hold keys to new solutions for the protection of hard-to-preserve cells for clinical use.
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