Type of Document Master's Thesis Author Acharya, Tathagata Author's Email Address email@example.com URN etd-11072008-013716 Title Freezing Processes in Cell Suspensions Evaluated Using Cryomicroscopy Degree Master of Science in Mechanical Engineering (M.S.M.E.) Department Mechanical Engineering Advisory Committee
Advisor Name Title Devireddy, Ram Committee Chair Wong, Harris Committee Member Monroe, William Todd Committee Member Keywords
- intracellular ice formation
- water transport
Date of Defense 2008-10-14 Availability unrestricted AbstractThis thesis aims at evaluating the freezing response of three different cell types, Pacific Oyster embryos, Jurkats and Helas, using the technique of cryomicroscopy. The choice of cells was primarily based on supporting ongoing research work at the Bioengineering Laboratory, Department of Mechanical Engineering at Louisiana State University in Baton Rouge. On a secondary basis, the cells were chosen based on their contrasting nature. While Pacific Oyster being a favorite food in USA calls for successful techniques of cryopreservation of their embryos in order to keep up with the growing demand, Jurkat and HeLa are undesired malignant human cells that require successful cryosurgical techniques for their destruction.
The fourth chapter of the thesis addresses the freezing experiments performed on Oyster embryos at freezing rates of 5 deg C/min and 10 deg C/min. During these experiments, embryos were investigated for either dehydration (water transport) or intracellular ice formation (IIF). The next two chapters address the freezing experiments performed on Jurkat cells and HeLa cells respectively. Freezing rates ranging from 1 deg C/min to 50 deg C/min were used for these cells. Once dehydration was observed, the cells were examined for their volume shrinkage. A graph of temperature against normalized volume was plotted using the experimental results. The key cell level parameters were: Reference permeability of cell membrane to water (Lpg), apparent activation energy (ELp), inactive cell volume (Vb), and the ratio of surface area for water transport to the volume of intracellular water (SA/WV). The values of ‘Vb’ for the chosen cells were known from earlier literature. The experimental data was fit into the water transport equation, using a numerical model, in order to obtain the values of the unknown cell level parameters i.e. Lpg and ELp. Finally, Generic Optimal Cooling Rate Equation (GOCRE) was used to determine the optimal cooling rate for the chosen variety of cells. Hence, higher freezing rates were used on the cells, which were investigated for IIF. IIF observed using cryomicroscopy, through darkening probably supported the results for optimal freezing rates, obtained using the water transport experiments and subsequent numerical simulations.
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