Effect of cooling rate on the quality of biological samples during cryopreservation.

Cryopreservation, a fundamental technology in modern biomedicine, has driven substantial advancements across several pioneering fields, including cell therapy, reproductive medicine, and tissue engineering. In lowtemperature environments, the rate of biochemical reactions in biological samples is significantly reduced, thereby prolonging their storage longevity. However, the essence of cryopreservation extends beyond merely maintaining low temperatures; the cooling rate emerges as a pivotal parameter during the cooling process, from ambient to storage temperatures, significantly influencing both the survival rate and efficacy of preservation. Furthermore, distinct biological samples exhibit varying sensitivities to cooling rates, with both excessively rapid and excessively slow cooling potentially inducing irreversible damage. Consequently, a comprehensive investigation and determination of the optimal cooling rates for different biological samples is essential to enhance the outcomes of cryopreservation. This review thoroughly examines the mechanisms by which cooling rates affect various biological samples, compares preservation outcomes across different cooling conditions with existing literature, and consolidates the optimal cooling rates for these samples. Research indicates that the optimal cooling rate for cell-like samples is generally below 10 ◦C/min whereas tissue-like samples typically require a slower rate, usually maintained below 1 ◦C/min. This controlled cooling process can be precisely achieved using a controlled-rate cooling device. Furthermore, this manuscript provides a brief overview of controlled-rate cooling techniques and the principles of slow freezing, offering a theoretical foundation for optimizing cryopreservation protocols for biological samples