(65g) Dielectrophoresis for Characterizing Electrical Properties of Mouse Ovarian Surface Epithelial (MOSE) Cells

Lab-on-a-Chip (LOC) devices have commonly been used to isolate and uncover the intrinsic properties of rare cells. Reactions in LOC devices occur quickly and require smaller quantities of samples and reagents compared to their macroscale counterparts. Recently, a number of technologies have been developed which are capable of isolating cells based in their intrinsic properties. These techniques hold great potential as a means of early cancer detection. In this study we used contactless dielectrophoresis devices to study the electrical properties of ovarian cancer cells.

Ovarian cancer is the fourth leading cause of death in women in the United States among all cancers. The main reason for this high rate of mortality is the inability to properly detect these carcinomas early. The lack of adequate cell models to study different cancer stages and the lack of a reliable technique to isolate these cancer cells from peritoneal fluid have hindered the investigation of ovarian cancer.

Dielectrophoresis (DEP) is a commonly employed technique for cell manipulation, isolation, enrichment, and mixing in microdevices. Cell membrane morphology, membrane surface permeability, cytoplasm conductivity, radius, and surface proteins influence the DEP response of cells. Due to this, different cell types exposed to the same electric field exhibit unique DEP responses suggesting that cells can be selectively manipulated using DEP. Additionally, the influential nature of the cell membrane on DEP response provides a mechanism to calculate its electrical properties based on DEP response observations. In this work, we investigate the changes in electrical properties of mouse ovarian epithelial (MOSE) cells as the cells progress from relatively benign to aggressive stages.

A continuous sorting low frequency cDEP device was fabricated in PDMS. A silicon master stamp was first fabricated using typical photolithography techniques and deep reactive ion etching. The device was then cast in PDMS using a 10:1 ratio of monomers to curing agent. The polymer replicates were bonded to glass slides using air plasma after access holes were punched. Four different stages of MOSE cells were independently driven through the device using a syringe pump at a flow rate of 0.005 mL/hour. A 200 V_RMS signal was then applied across the device for frequencies between 5 and 100 kHz. The distribution of cells within the device was recorded and processed to determine the first crossover frequency. Measurements of the cell radius were then used to calculate the area specific membrane capacitance for each cell line.

We found that cell membrane capacitance increases as the cells progress into more malignant states. This is consistent with previous studies which show changes in the cells mechanical properties and membrane morphology. We hypothesize that the differences in membrane capacitance were due to morphological differences and changes in the cytoskeleton among stages of these transformed MOSE cells. This work is the first step to understanding the difference in electrical properties of cell associated with ovarian cancer and future work will focus on isolating these cells from the native cells found in peritoneal fluid.