Cryopreservation of Cells Encapsulated Within Nano-thin Polyelecrolyte Coatings

Cryopreservation is a method which enables to store the cells for a long time period and allows to obtain the appropriate amount of cells necessary for transplantation. Unfortunately, the cells isolated from organs like e.g. hepatocytes are susceptible to freezing damage. Encapsulation may be considered as a method allowing to protect cells during adverse freezing conditions. Aim: Assesement of the usability of nano-thin semipermeable membrane coating shell as protective element during cryopreservation of the cells. Materials and Methods: Liver cells, isolated from living donors (according to Bioethical Community protocol) or hepatoma cell line HepG2 were encapsulated within nano-thin poly-L-lysine/polyethylenoimine with incorporated fullerene (PLL/PEI+f) membrane or within standard alginate microcapsules. As a control group the cells were encapsulated The mitochondrial activity of cells was analyzed after 4 months cryopreservation using 5-diphenyltertrazolium bromide tetrazolium (MTT) test. The viability of cells was assessed utilizing flow cytometry during 8-day culture after thawing. Results: The cells protected during cryopreservation by nanomembranes or microcapsules were after thawing in better condition than nonencapsulated cells. The mitochondrial activity expressed as absorbance was comparable in both types of encapsulation within nano-thin membranes or microcapsules in MTT test. The percentage share of viable cells in all tested groups was meanly 90%. Conclusions: Applied nanocoating did not delimit the viability of cryopreserved cells as compared to microencapsulation. The cryopreservation within nano-thin semipermeable membranes seems to be promising way to protect cells during long term storage in liquid nitrogen when minimizing the encapsulated transplant volume is necessary.