The Thermodynamic Parameters Of Cryoprotective Agents With Nanoparticles Examined By DSC

Vitrification is presently one of the best method for long-term preservation of biomaterials as a series of injuries during freezing and warming are avoided. But it is a challenge to preserve relatively large and complicate tissues and organs by vitrification, as result of restriction of cooling rate and concentrations of cryoprotective agents (CPAs). Although many studies have been done to improve cooling rate by changing several thermal situation except the solution itself. There are few reports to study the heat and mass transfer property of CPAs to enhance the vitrification capability.Nanoparticles can improve the conductivity of fluid at room temperature. It is essential to analyse the thermal physical properties of Nano-CPAs which is a new type of heat transfer carriers by suspending nanoscaled metallicor nonmetallic particles in base CPAs. In this paper different scanning calorimeter (DSC) is used to study the supercooling, hydration, vitrification and specific heat of Nano-CPAs and analyse the effect of nanoparticles on critical cooling rate, as follows:1. Different sizes and concentrations of Nano-CPAs were prepared by using ultrasonic oscillation method and the stability and uniformity of suspensions were evaluated by using sedimentation observation, Zeta electric potential and spectrophotometer. The results show that the oscillation time is the main factor to influence stability of suspensions. When the power of ultrasound is400W and the oscillation time is2hours, the well-distributed and stable nano-fluid could be got to ensure that the agglomeration and sedimentation would not happen in48hours.2. The effects of nanoparticles on the nucleation temperatures, supercooling and hydration of Nano-CPAs of different mass concentrations (30%,40%,50%) with different amount of HA(Hydroxyapatite) nanoparticles are measured respectively. The results show that the nucleation temperature increased and the supercooling decreased. When the concentration of HA nanoparticles is0.3%, the increment of nucleation temperatures and supercooling decrements reach maximum values(-10℃). The supercoolings reduce with the increasing size of nanoparticles. The hydration could be improved by addition of nanoparticles. The crystallization enthalpies will decline with the increasing size of nanoparticles.3. The specific heat values of glycerol solutions with nanopartices decreased during glass transition process. For the50%glycerol solution, the specific heat values decreased with the increasing mass fractions and deceasing sizes (20nm-60nm) of HA naoparticles.4. The glass transition temperature and the devitrification temperature of different nano-CPAs were measured. The results show that the devitrification temperatures of CPAs could be increased significantly by nanoparticles. When the concentration of solutions is larger than50%, the glass transition temperatures increase slowly. The values of Tm-Tg reduce after adding nanoparticles, which shows that the stability of glass solutions during heating process is improved by nanoparticles. Based on the above results, the conclusion can be drawn that the critical cooling rate can be reduced by suspending nanoparticles into the CPAs.