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Li W.,University of Shanghai for Science and Technology | Zhou X.,University of Shanghai for Science and Technology | Wang H.,University of Shanghai for Science and Technology | Liu B.,University of Shanghai for Science and Technology | Dai J.,Animal and Veterinary Research Institute
Cryo-Letters | Year: 2013

Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40% ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is about 9000 W/(m 2·K) Source


Li W.-J.,University of Shanghai for Science and Technology | Zhou X.-L.,University of Shanghai for Science and Technology | Liu B.-L.,University of Shanghai for Science and Technology | Dai J.-J.,Animal and Veterinary Research Institute | And 3 more authors.
Chinese Journal of Biomedical Engineering | Year: 2013

Nano-cryopreservation is a promising new way in the next generation of cryopreservation technology; however, using nanoparticles in oocytes vitrification has been rarely reported. This paper investigated the effect of hydroxy apatite (HA), silica, aluminum oxide, and titanium dioxide nanoparticles in the cryoprotectant on the survival rate and developmental rate of porcine GV- stage oocytes. The cells were cryopreserved in Cryotop and observed using fluorescence staining methods. Results showed that HA nanoparticles have the lowest cytotoxicity among the other nanoparticles, the developmental rate of GV-stage porcine oocytes was 100% when concentrate of HA was lower than 0.5%. When the concentration of HA was 0.1% in the cryoprotectant, the developmental rate of GV-stage porcine oocytes was 22% in Cryotop, which was significantly higher than that in the other groups. The size of nanoparticles exerted little influence. When 0.05% HA nanoparticles (60 nm in diameter) were added, the developmental rate increased dramatically from 14.7% in control group to 30.4%. In conclusion, adding appropriate concentration of HA nanoparticles to cryoprotectant can reduce recrystallization during rewarming and promote survival rate and developmental rate of oocytes after freezing and rewarming. The effect of HA nanoparticles is concentration dependent, while independent to diameters of the nanoparticles. Source

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