| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 99 === The goal of this thesis is to study how to extract the dielectric properties of cells from the measurements of the real part of the Clausis-Mossotti factor (CMF), the crossover frequency ( ) of dielectrophoresis, and the peak frequency ( ) of electrorotation. Both the theory and the calculation procedures are proposed and demonstrated using the experimental data in the literature, together with some additional CMF measurements in the present study, which includes the measurements of lung cancer cells CL1-0 and CL1-5, and the colorectal cancer cell Colo205.
In the present CMF measurement as well as those in the literature, CMF was measured for different applied electric frequencies (from 10 kHz to 40 MHz) and medium conductivity (from 0.01 – 1 S/m). The dielectric properties of cells can be extracted according to the definition of CMF together with a suitable cell model using the optimization method. The membrane capacitance (permittivity divided by the membrane thickness) differs slightly for various cells, and are found to be 4.97~5.92 for different frequencies for CL1-0, CL1-5 and Colo205. However, the membrane conductance (conductivity divided by membrane thickness) of CL1-5 (more invasive in comparing with CL1-0) is 921~997 , which is about twice greater than those of CL1-0 and Colo205 (561~603 ). The cytoplasm conductivity is 0.842~1.165 for these three cells. The cytoplasm relative permittivity is 72~101 for CL1-5, which is slightly less than 78~142 for CL1-0 and Colo205. The dispersion phenomenon, i.e., the variation of properties with applied electric frequency, is observed for both the cytoplasm conductivity and permittivity.
There exists theory and method for extracting the cell properties from the experimental data of and in the literature. However, it was also found that the membrane conductance extracted from is three times greater than that from when the medium conductivity is of order of 0.1 S/m. Through a theoretical scaling analysis, it was found in the present study that the discrepancy is due to the DC limit approximation employed in the previous theory. A modified theory was thus proposed and validated in the present thesis. With the modified theory, it was found that the membrane capacitance are 7.95, 7.27 and 5.24 , the membrane conductance are 662, 1245 and 512 , the cytoplasm conductivity are 0.935, 0.862 and 0.828 S/m, and the cytoplasm relative permittivity are 93, 114 and 153, respectively, for CL1-0, CL1-5 and Colo205. Note that the above values agree with those obtained using CMF data.
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