Effects of nanoparticles on devitrification and recrystallization of aqueous glycerol and PEG-600 solutions

Nanoparticles in solution offer unique electrical,mechanical and thermal properties due to their physical presence and interaction with the state of dispersion.This work is aimed to study the effects of hydroxyapatite(HA)nanoparticles on the behavior of devitrification and recrystallization of glycerol(60%w/w)and PEG-600(50%w/w)solutions during warming.HA nanoparticles of different sizes(20,40,60 nm)and concentrations(0.1%,0.5%,w/w)were incorporated into solutions,and were studied by calorimetric analysis coupled with cryomicroscopy.The presence of HA nanoparticles has little effect on the devitrification end temperatures,but affects the devitrification onset temperatures of glycerol and PEG-600 solutions.The investigation with the cryomicroscope observed that the ice morphologies of glycerol and PEG-600 solutions are dendritic and spheric respectively.The ice fraction of glycerol solution containing 0.1%HA with the size of 60 nm decreased to 2/5 of that of the solution without nanoparticles at 45°C.The ice fractions of PEG-600 solutions increased significantly between 64°C and54°C,and the ice fraction of PEG-600 solution without nanoparticles increased by 92%within the temperature range.The findings have significant implications for biomaterial cryopreservation,cryosurgery,and food manufacturing.The complexity of ice crystal growth kinetics in nanoparticle-containing solutions awaits further study.

Optimization of cryopreservation of pathogenic microbial strains

The preservation of pathogenic microbial strains is of great significance for basic research in microbiology and utilization of microbial resources.Appropriate preservation methods can maintain high survival rate and genetic stability of pathogenic microbial strains for a long time.This study summarizes the current status of preservation of strains,discusses the limitations and damaging factors of cryopreservation and prospects for optimization,and explores the mechanism of cryopreservation of strains.Our main objective is to provide a reference for the long-term effective preservation of microbial resources and guarantee of national biosafety.

Effects of Hydroxyapatite Nanoparticles on Devitrification Crystallization in Cryoprotectant Solutions

To study the effects of Hydroxyapatite(HA) nanoparticles on devitrification in cryoprotectant solutions,the crystallization of glycerol(60%,w/w) and PEG-600(50%,w/w) solutions with HA nanoparticles of different sizes(20 nm、 40 nm、60 nm)and different concentrations(0.1%、 0.5%)during warming were investigated by using differential scanning calorimetry(DSC) combined with cryomicroscopy.Experimental results showed that the presence of nanoparticles does not change the glass transition temperatures and melting temperatures of quenched solutions,but affects the behavior of devitrification and recrystallization upon warming.The morphologies of glycerol and PEG-600 solutions are dendritic and spheric respectively,and the structures are not changed by adding nanoparticles.The ice fraction of glycerol solution containing 0.1%60nm HA nanoparticles diminished significantly when comparing to the control solution.The ice fractions of PEG-600 solutions increased dramatically between-64℃ and-54℃.The findings have significant implications for biomaterial cryopreservation.