Porcine heart valve, aorta and trachea cryopreservation and thawing using polydimethylsiloxane

The most common cryopreservation protocols of biological tissues suitable for their further implantation has some disadvantages and limited to one sample per procedure with no possible repeated freezing in case of clinical needs. This study is aimed to improve a biological tissues cryopreservation by adding a new heat transfer fluid - polydimethylsiloxane (PDMS). To evaluate its efficiency the porcine biological tissues (heart valves, aortic and trachea fragments) were cryopreserved and thawed in low-viscous PDMS. According to the computer simulation, the midsection cooling rate was up to 490 °C/min and the midsection thawing rate was up to 1140 °C/min with admissible temperature uniformity. Cryoprotectants and liquid nitrogen were not used. The quality of tissue cryopreservation was evaluated using a number of histological and immunohistochemical methods (Orcein, H&E, Anti-CD34, Anti-Vimentin, Anti-Actin staining). Cryopreserved tissues showed no significant morphological difference in comparison with control group both in case of immediate thawing, and after 2 months of low temperature storage. Computer simulation of heat transfer showed the thermal limitations of used approach for larger specimens. The use of PDMS is proposed for preservation of vascular tissue in order to implant it in the form of homotransplants or biobanking with the possible additional use of an internal hydrophilic coating to prevent hydrophobization.