Library Subscription: Guest

ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Cryogenic heat and mass transfer in biomedical applications

Get access (open in a dialog) DOI: 10.1615/IHTC12.3210
16 pages

Abstract

Two important biomedical applications of cryobiology are cryopreservation and cryosurgery. In cryopreservation freezing is used to achieve indefinite banking of cells and native or artificial tissues in the frozen state prior to thawing and use. On the other hand, cryosurgery uses low temperatures to destroy diseased or unwanted tissues such as tumors in situ. Chemicals called cryoprotective agents (CPAs) are loaded into cells and tissues before cryopreservation to improve their viability during and after freeze/thaw. While the characteristic biophysics of single cell CPA loading has been understood for some time using irreversible thermodynamics of coupled flows (water and CPA), significant challenges in both measurement and prediction of cellular biophysics and mass transport exist for this problem within more complicated tissue systems. During freezing and thawing important challenges for both applications are associated with the control of injury most notably due to two biophysical events which are oppositely dependent on cooling rate: either excessive cellular dehydration or intracellular ice formation (IIF). While experimental techniques and models exists for spherical cells there remain challenges in the measurement and modeling of cellular level biophysics for non-spherical cells and tissue systems during freezing. To study challenges associated with CPA loading and freezing of biomaterials, experimental techniques based on differential scanning calorimetry (DSC), cryo or low temperature microscopy, and nuclear magnetic resonance (NMR) imaging have recently been developed. These techniques have provided useful data to generate new and/or modified models of the phenomenon and to define biophysical parameters which govern the processes. Finally, to predict the thermal history during freezing, which is linked to biophysical response and therefore injury, a precise understanding of the thermal response is needed. Here a lack of information on the temperature dependence of thermal properties (thermal conductivity, specific heat and latent heat) for biological materials at low subzero temperatures is a continuing challenge. Progress in the application of cryogenics in medicine requires continued work in defining both biophysical and thermal behavior (i.e. properties and response) of biological systems at low temperatures.