By comparing the cooling characteristics of four types of cryoprobes under different inlet pressures, the effects of the inlet pressure, J-T slot inner diameter, and backflow channel size on the cooling of cryoprobes are analyzed, and the size of ice hockey balls formed in gelatin are tested. The results show that the temperatures of 1.8-0.42 mm, 1.8-0.30 mm, 1.8-0.12 mm, and 1.1 mm cryoprobes are the fastest under the inlet pressure of 4.5 MPa, 4.0 MPa, 5.5 MPa, and 5.5 MPa, respectively. When the pressure is low, the cooling rate is positively correlated with the inlet pressure. When the inlet pressure is greater than the optimal pressure, the ice blockage increases with increasing pressure. Among the cryoprobes, a smaller inner diameter of the J-T slot improves the cooling rate of the cryoprobes and lowers the temperature of the tip, and a larger backflow channel can reduce ice blockage in the pipe and improve the cooling rate; 1.8-0.42, 1.8-0.30, 1.8-0.12 mm, and 1.1 mm cryoprobes have the largest ice hockey ball diameters under air supply pressures of 4.5, 4.5, 6.0, and 6.0 MPa, respectively. When the inner diameter of the J-T slot decreases, its optimal air supply pressure increases.

In recent years, hydrogels have exhibited considerable advantages in cell and organoids culture as well as cryopreservation, particularly in cell cryopreservation. In this study, the spray method was selected, and ferric iron and calcium were used as cross-linking agents. The hydrogels were prepared using a low-cost and readily available airbrush. Subsequently, calcium alginate and iron alginate hydrogels were prepared, and HEK293T cells and HepG2 cells were encapsulated using this method. The study also investigated the impact of cross-linking solutions on cell viability during encapsulation, revealing that longer crosslinking times led to greater cell damage. Additionally, it was observed that crosslinking with sodium alginate solution reduced cell damage in the crosslinking solution. Furthermore, hydrogels crosslinked with CaCl₂ (0.2 mol/L) using sodium alginate solution at various mass fraction (1%, 1.5%, and 3%) were prepared. HEK293T cells were encapsulated and cultured for 7 d under these conditions, and successful cell culture was observed across all concentrations. Finally, the viability of cell cryopreservation after encapsulation was examined. The results showed that the viability of HEK293T and HepG2 cells, under the precondition of using two different volume fraction of dimethyl sulfoxide as protective agents, was significantly higher than that of the unencapsulated group. Specifically, for HEK293T cells before encapsulation, cell viability was 33.16% ± 2.70% (10% DMSO) and 16.75% ± 2.3% (5% DMSO). After encapsulation, cell viability increased to 76.51% ± 5.32% (10% DMSO) and 60.86% ± 2.41% (5% DMSO). Similarly, for HepG2 cells, cell viability increased from 48.93% ± 3.06% (10% DMSO) and 36.22% ± 2.54% (5% DMSO) to 78.79% ± 4.43% (10% DMSO) and 64.64% ± 3.13% (5% DMSO) after encapsulation. Moreover, when using ethylene glycol (1 mol/L) + propylene glycol (1.5 mol/L) + trehalose (1 mol/L) as a protective agent, the viability of HEK293T cells after vitrification increased from 33.5% ± 0.8% to 79% ± 3.76% after encapsulation. These results strongly indicate that encapsulated cells exhibit significantly higher viability after cryopreservation compared to unencapsulated cells, emphasizing the protective capacity of ionic cross-linked alginate hydrogels during cryopreservation.

The aim of this study is to optimize the cryopreservation scheme for microcarrier hepatocyte complexes used in artificial liver support systems to improve cell survival and adhesion rates. The effects of cryoprotectant concentration, loading temperature, and method on cell viability were evaluated experimentally. It was found that cell toxicity and osmotic damage were reduced significantly, and higher cell survival and adhesion rates were maintained by using two-step loading of 5% volume fraction dimethyl sulfoxide (Me₂SO) at 4 ℃. In addition, we investigated the effects of intracellular ice formation and cooling rate on cell viability and attachment. By performing ice seeding at -6 ℃, the intracellular ice damage was effectively reduced, and the adhesion rate of cells after recovery was improved. The experimental results show that a 10% volume fraction of Me₂SO and a cooling rate of 1 ℃/min, despite having high toxicity and osmotic damage, have the best freezing effect due to the smallest difference in thermal expansion. This study provides important techniques for the cryopreservation of microcarrier hepatocyte complexes for artificial liver support systems.

In tumor cryoablation therapy, the effective improvement of the cooling rate of the freezing process is a research hotspot. In this study, a novel cryoablation needle with an adjustable throttle nozzle was designed. The external surface temperature of the needle could be reduced to -80 ℃ within just 4 s, while the traditional cryoablation needle with a fixed throttling nozzle requires 73 s. The three-dimensional heat transfer model simulation results show that the temperature around the cryoablation needle drops sharply to -150 ℃ within 120 s, and the fastest instantaneous cooling rate is 1500-1575 ℃/min, which achieves the purpose of rapid cooling. In addition, the -20 ℃ isotherm has a small variation range from 60 s to 120 s (increasing from 5 mm to 6.5 mm), and the temperature changes tend to be gentle after 120 s, and the tissue damage range increases to 9 mm, indicating that the tissue damage range increases significantly. Comprehensive studies have shown that the adjustable throttling nozzle cryoablation needle has a higher cooling rate and larger effective ablation range, which is of great significance for clinical cryoablation treatment.

Dimethyl sulfoxide (Me₂SO) in cell banking exhibits significant side effects on both the cells and the human body. Therefore, an approach that mitigates the side effects of Me₂SO with comparable efficacy is urgently needed. The human umbilical cord mesenchymal was used as the research material. First, the thermal physical properties of trehalose, glucose, and L-proline and their regulation of ice crystal growth were measured using a differential scanning calorimeter and a cryomicroscope. Cryopreservation experiments were performed to determine the optimal concentration of each component in the cryopreservation solution, and the viability and functionality of the cells after cryopreservation were validated. The results show that there is no significant difference in cell viability (92.42%±0.28%) and recovery rate (87.80%±4.22%) between the use of the novel stem cell cryopreservation solution (1.25 mol/L ethylene glycol + 10 g/L whey protein + 0.1 mol/L trehalose + Normosol-R) and the conventional cryopreservation solution (a volume fraction of 10% Me₂SO). Moreover, after 3 days of culture, the cell number was (12.42±0.60) × 10⁶ (proliferation fold of 4.97), and the cell phenotype was not significantly different from that of fresh cells. The proposed novel solution for stem cell cryopreservation solves the problem of "Me₂SO-free" cryopreservation of cells and offers promising potential for clinical applications.

To investigate the low-temperature tolerance of Phoenix canariensis seeds and isolated seed embryos, along with the physiological changes that occur during cryopreservation, fresh seeds were dried to 25%, 20%, and 15% moisture content and then cryopreserved at -20 ℃ and -196 ℃ (LN₂). The results showed that the survival rate of intact seeds gradually increased with decreasing water content. The survival rate of isolated seed embryo cultures increased with decreasing water content, and the growth rates of seeds and seed embryos dried to 11.6% moisture content were not significantly different from those of the unfrozen groups. The viability of LN₂-preserved intact seeds and isolated seed embryos was higher than that of the -20 ℃ preservation group. After cryopreservation, the sucker part of the seed embryos was damaged more severely than the cotyledon after low-temperature preservation; however, this damage did not affect the subsequent growth of the seed embryos. After drying to an 8% moisture content, the superoxide dismutase (SOD) activity of the seeds was lower than that of fresh seeds, and the CAT activity and MDA content increased. After cryopreservation, the SOD activity and CAT activity of the seeds increased, and the MDA content decreased, whereas the MDA content of the seeds increased significantly after drying, indicating that excessive dehydration was not conducive to seed cryopreservation. Phoeni canariensis seeds are highly resistant to low temperatures and can be preserved in liquid nitrogen for long periods.

Today, energy is essential for every aspect of human life, including clothing, food, housing and transportation. However, traditional energy resources are insufficient to meet our modern needs. Self-powered sensing devices emerge as promising alternatives, offering sustained operation without relying on external power sources. Leveraging advancements in materials and manufacturing research, these devices can autonomously harvest energy from various sources. In this review, we focus on the current landscape of self-powered wearable sensors, providing a concise overview of energy harvesting technologies, conversion mechanisms, structural or material innovations, and energy storage platforms. Then, we present experimental advances in different energy sources, showing their underlying mechanisms, and the potential for energy acquisition. Furthermore, we discuss the applications of self-powered flexible sensors in diverse fields such as medicine, sports, and food. Despite significant progress in this field, widespread commercialization will necessitate enhanced sensor detection abilities, improved design factors for adaptable devices, and a balance between sensitivity and standardization.