Measurement of Water-Cryoprotectant Mutual Diffusivity in Micro-Scale Biological Tissues at Subzero Temperatures

Water-cryoprotectant mutual diffusivity (D¯) in biological tissues at subzero temperatures is of critical importance for optimizing tissue or organ cryopreservation procedures. Currently, there exist no attempts to measure D¯ at subzero temperatures. We pioneered a thermal analytic method to measure this mass transfer parameter in biological tissues at the level of micro-liters. Using differential scanning calorimetry, the values of D¯ in mouse ovaries (∼4–8μl) with ethylene glycol (EG) as cryoprotectant were measured at −20°C, −10°C, 0°C, 10°C and 20°C. The results show the Arrhenius law is strictly followed (R² = 0.99) over this temperature range with the activation energy as 3.78 kcal/mol. The value of D¯ with EG as the cryoprotectant at 20°C, 6.2×10⁻⁷cm²/s, agrees well with that previously measured using a magnetic resonance imaging method at the same temperature, 6.1×10⁻⁷cm²/s.