Recent years have witnessed significant advancements in the cryopreservation of various tissues and cells, yet several challenges persist. This review evaluates the current state of cryopreservation, focusing on contemporary methods, notable achievements, and ongoing difficulties. Techniques such as slow freezing and vitrification have enabled the successful preservation of diverse biological materials, including embryos and ovarian tissue, marking substantial progress in reproductive medicine and regenerative therapies. These achievements highlight improved post-thaw survival and functionality of cryopreserved samples. However, there are remaining challenges such as ice crystal formation, which can lead to cell damage, and the cryopreservation of larger, more complex tissues and organs. This review also explores the role of cryoprotectants and the importance of optimizing both cooling and warming rates to enhance preservation outcomes. Future research priorities include developing new cryoprotective agents, elucidating the mechanisms of cryoinjury, and refining protocols for preserving complex tissues and organs. This comprehensive overview underscores the transformative potential of cryopreservation in biomedicine, while emphasizing the necessity for ongoing innovation to address existing challenges.

Comparison of Probe Materials for Tissue Cryoablation: Operational Properties of Metal and Sapphire Cryoprobes

This work describes a sapphire cryo-applicator with the ability to sense tissue freezing depth during cryosurgery by illumination of tissue and analyzing diffuse optical signals in a steady-state regime. The applicator was manufactured by the crystal growth technique and has several spatially resolved internal channels for accommodating optical fibers. The method of reconstructing freezing depth proposed in this work requires one illumination and two detection channels. The analysis of the detected intensities yields the estimation of the time evolution of the effective attenuation coefficient, which is compared with the theoretically calculated values obtained for a number of combinations of tissue parameters. The experimental test of the proposed applicator and approach for freezing depth reconstruction was performed using gelatin-based tissue phantom and rat liver tissue in vivo. It revealed the ability to estimate depth up to 8 mm. The in vivo study confirmed the feasibility of the applicator to sense the freezing depth of living tissues despite the possible diversity of their optical parameters. The results justify the potential of the described design of a sapphire instrument for cryosurgery.

BACKGROUND: local cryotherapy (LC) is a promising method of treating various diseases, as a result of which the effects of anesthesia and reduction of inflammation are achieved. The main factor of efficiency from a physical point of view is the achievement of the target temperature on the surface of the impact area. At the same time, during the procedure, the surface temperature of the tissue should not fall below the minimum permissible the limit temperature for safety. AIMS: identification of the range of target and limit temperatures in terms of safety parameters based on the results of literature analysis, carrying out experiments with the use of ice bag for cooling the biotissue phantom, determining the most appropriate impact modes. MATERIALS AND METHODS: a series of experiments was carried out on the developed stand to compare the two modes of the contact method of LC, depending on the working substance used (sodium chloride solution, a mixture of ice and water). The comparison was carried out according to the following parameters: the time to reach the target temperature on the surface, the temperature at the depth of the model medium. The temperature was measured by resistance thermometers (Pt100). RESULTS: when cooled with a sodium chloride solution, the surface temperature of the model medium dropped to 10 C in 6 minutes of exposure, and after 17 minutes reached its minimum value of 6.2 C. In the case of using a mixture of water and ice, the minimum temperature of 12.5 C was reached in 58 minutes. The minimum temperature at a depth of 8 mm in both cases was approximately the same and was about 17 C. It was reached by 19 minutes with a solution of sodium chloride and for 58 minutes with a mixture of water and ice. CONCLUSIONS: as a result of the experiments carried out, the most suitable contact cooling mode with the use of ice bag was determined - a mode using sodium chloride as a working substance with an initial temperature of minus 18.4 C with a possible impact time from 6 to 19 minutes.