Authors: S. Bunthawin, P. Wanichapichart, A. Tuantranont
Affilation: Membrane Science and Technology Research Center, Thailand
Pages: 485 - 488
Keywords: cell dielectric property, traveling wave dielectrophoresis, velocity, critical frequency, arsenic
This study determined changes in cell dielectric properties due to variation of arsenic concentration of the cell suspending medium, from 1 to 150 ppm. An octa-pairs interdigitated electrode was used to induce dielectrophoresis, and the field strength was calculated using Quick FieldTM program version 5.5. With this technique, essential data needed for cell dielectric estimations were either the cell velocity towards electrode direction or two critical frequencies; the lower and the upper boundary values of which cells were repelled from the electrode after being attracted. Theories used to explain the former was derived from Laplace model and the latter was from RC-model - after having corrected an assumption used in our previous reported (IEEE-NEMS 2007, p. 472-477). The cell movement was recorded through a CCD camera and the velocity was measured using a computer program Winfast PVRTM. Marine phytoplankton, Tetraselmic sp., was used as a test model. This study found that the cell velocity was increased with field strength, while the two frequencies were not affected. By curve fittings to both the velocity and frequency data, the results implied that cells reduced in its cytoplasmic conductivity greatly after arsenic absorption, and the reverse was true for the cell membrane. This result coincided with our previous report using cell electro-rotation technique (IEEE-NEMS 2007, p. 1115-1120). When arsenic content in the pretreated solution was as great as 100 ppm, the cell ceased to proliferate. Interestingly, cells exhibited a non homogeneous velocity curve in all cases, suggesting that the electric field under frequencies between 10 kHz and 100 MHz can “see” the two compartments of plant cells.