Effects of freezing rates and dimethyl sulfoxide concentrations on thermal expansion of rabbit aorta during freezing phase change as measured by thermo mechanical analysis.

Thermal expansion data are essential for thermal stress analysis in order to predict the likelihood of fracture formation in tissues during cryopreservation as well as cryosurgery. The current study focuses on examining the thermal expansion behavior of rabbit aorta during freezing, especially phase change processes. Thermo mechanical analysis (TMA) was used to investigate the effects of different concentrations of dimethyl sulfoxide (DMSO) cryoprotective agent (CPA) (0%, 5%, 10%, and 15% (v/v) DMSO) and different freezing rates (3, 5 and 10 degrees C/min). The results showed that (1) the maximum of thermal strain for 10 degrees C/min was approximately four times greater than that for 3 degrees C/min, and 1.4 times greater than that for 5 degrees C/min, and the higher the freezing rate, the larger the corresponding thermal expansion coefficient; (2) the maximum thermal strain of sample permeated by 5% DMSO approached that of 0% DMSO (i.e., no DMSO was added); however, it showed very significant difference from that of 15% DMSO (only half of that with 5% DMSO), and the thermal expansion coefficient decreased when the concentration of DMSO solution increased; (3) comparison with data available from the literature and with theoretically calculated values illustrated that the thermal expansion change was not equal to the volume change from free water to ice during freezing, but was related to the freezing rate of samples and the DMSO concentration.