ABSTRACT
Ultra-rapid cooling and rewarming rate is a critical technical approach to achieve ice-free cells during the freezing and melting process. A set of ultra-rapid solid surface freeze-thaw visualization system was developed based on a sapphire flim, and experiments on droplet freeze-thaw were carried out under different cryoprotectant components, volumes and laser energies. The results showed that the cooling rate of 1 μL mixed cryoprotectant [1.5 mol/L propylene glycol (PG) + 1.5 mol/L ethylene glycol (EG) + 0.5 mol/L trehalose (TRE)] could be 9.2×10 3 °C/min. The volume range of 1-8 μL droplets could be vitrified. After comparing the proportions of multiple cryoprotectants, the combination of equal proportion mixed permeability protectant and trehalose had the best vitrification freezing effect and more uniform crystallization characteristics. During the rewarming operation, the heating curve of glassy droplets containing gold nanoparticles was measured for the first time under the action of 400-1 200 W laser power, and the rewarming rate was up to the order of 10 6 °C/min. According to the droplet images of different power rewarming processes, the laser power range for ice-free rewarming with micron-level resolution was clarified to be 1 400-1 600 W. The work of this paper simultaneously realizes the ultra-high-speed temperature ramp-up, transient visual observation and temperature measurement of droplets, providing technical means for judging the ice free droplets during the freeze-thaw process. It is conducive to promoting the development of ultra-rapid freeze-thaw technology for biological cells and tissues.
Subject(s)
Freezing , Vitrification , Cryopreservation/methods , Trehalose , Gold , Rewarming , Metal Nanoparticles , Cryoprotective Agents , LasersABSTRACT
Objective To investigate the optimal cryopreservation liquid of the stable transfected cell line named hepatic carcino-ma HepG2 transfected by lentivirus .Methods Glycerol and DMSO as cryopreservation liguid ,The HepG2 transfected by lentivirus and HepG2 cells were both cryopreserved with four various proportion of cryopreservation liquid .After thawing ,the survival rate of the two cells were observed by inverted contrast microscope and the viability and proliferation were detected with MTT assay .Re-sults Using glycerol as cryoprotectant liquid ,the survival rate of the HepG2 cells transfected by lentivirus was obviously higher than other 3 groups when the proportion of the cryopreservation liquid(DMEM ∶FBS∶Glycerol)was 0∶9∶1(P=0 .001) ,where-as there was no significant difference among the groups of HepG2 cells with various proportion of cryopreservation liquid (P=0 .293) .Using DMSO as cryoprotectant liquid ,the survival rate of the cells transfected by lentivirus was 0% ,whereas the survival rate of the HepG2 cells was higher than 60% ,and there was no significant difference between groups of various proportion of cryo-preservation liquid(P=0 .487) .The MTT assay demonstrated that the higher the serum levels was ,the better proliferation capacity those cells had(P<0 .05) .Conclusion The optimal cryopreservation liquid for the hepatic carcinoma cell line HepG2 transfected by lentivirus is used glycerol as cryoprotectant solution ,and the proportion of cryopreservation solution was 90% FBS + 10%Glycerol .
ABSTRACT
Objective To explore the effects of cryopreservation on biological characteristics of cultured limbal stem cells.Design Experimental study.Participants Twenty New Zealand white rabbits.Methods Twenty New Zealand white rabbits(40 eyes) were preparated of peripheral cornea with 2 mm and 2 mm circular shallow conjunctival limbal graft.Rabbit limbal stem cells(Rb-LSCs) used for cell-suspention culture were isolated form New Zealand white rabbit limbal tissues.The limbal stem cells,having formated monolayer cultured limbal stem cells,were cryopreservated one month,then thawing.By immunofluorescence staining,flow cytometry,inverted microscope,MTT assay,we compared the subculture of limbal stem cells cryopreservation before and after the structure and properties.Main Outcome Measurements Limbal stem cell activity and biological characteristics.Results Compared with freshing cells,the cells after cryopreservation in morphology were poor adherence late,small nuclear cytoplasm ratio,irregular shape.Im munofluorescence staining to detect the low-temperature frozen cells ABCG2 monoclonal antibody 81.7% positive rate decreased to 46.9%,the difference was statistically significant(P