Thermodynamic analysis of the solidification processes for cryopreservation of biological tissues.
Nucleation of a cooling liquid occurs when atomic aggregates reach critical size that assures decreasing free energy as the crystal grows. Thermodynamic analysis allows to understand the ways to control the process. Evaluation of crystallized fraction in a freezing process is described as an example of biomedical application. For that purpose, 4 cm3 samples with different mixtures of RPMI 1640 and DMSO cryopreservant, were frozen in a programmed cooling chamber at a cooling rate of 1 degrees C/min. The temperatures of the chamber and the probe were plotted against time. Characteristic curves with different crystallization zones were obtained. The area of that zone beyond the base line determines the Relative Crystallisation Index (RCI) of the solution. The results were compared with usual methods of the National Organs and Tissues Bank of Uruguay. With 10% DMSO and VALPA 799 Program, the BNOT has obtained good quality cryopreserved cardiac valves and elastic arteries.
Costa
Blas Melissari
BM
Laboratorio de Biomecánica, Instituto de Ensayo de Materiales, Facultad de Ingeniería de la Universidad de la República, Montevideo, Uruguay.
D015925:Cryopreservation; D003460:Crystallization; D006801:Humans; D015397:Program Evaluation; D013816:Thermodynamics; D014015:Tissue Banks