Sakshin Bunthawin, Raymond J. Ritchie, and Pikul Wanichapichart

pp. 585 - 597

Abstract

Dielectrophoresis of a unicellular green alga, Tetraselmis sp., in a travelling electric field was analyzed using an RC
(resistor-capacitor)-model, instead of the Laplace approach reported in our previous work. The model consists of resistorcapacitor pairs in series to represent the conductive and the capacitive properties of the shell and the inner part of the spheroid.
The model is mathematically simpler than the Laplace model and the RC approach is experimentally superior because only the
lower critical frequency [LCF] and cell translational speed are required to be measured experimentally. The effective complex
impedance of the spheroid was mathematically modeled to obtain the Clausius-Mossotti factor ([CMF]) as a function of cell
dielectric properties. Spectra of dielectrophoretic velocity and the lower critical frequency of the marine green alga, Tetraselmis
sp. were investigated to determine cell dielectric properties using a manual curve-fitting method. Effects of arsenic at different
concentrations on the cell were examined to verify the model. Arsenic severely decreases cytoplasmic conductance (σ_c
)
whereas it increases membrane conductance (σ_m
). Effects were easily observable even at the lowest concentration of arsenic
used experimentally (1 ppm). The method offers a practical means of manipulating small plant cells and for rapid screening
for effects on the dielectric properties of cells of various applied experimental treatments.