Advances in Dielectrophoresis As a Biotechnology Tool

Dielectrophoresis (DEP) has been widely studied for its potential as a biomarker-free method of sorting cells based on their intrinsic dielectric properties. Under appropriate experimental conditions the DEP frequency spectrum typically exhibited by a viable mammalian cell in suspension is characterised by two frequencies, f_xo1 and f_xo2. At these two characteristic frequencies the effective conductance and capacitance values of the cell exactly match those of the fluid it has displaced, and are commonly known as the DEP cross-over frequencies. At low frequencies (< 10 kHz) viable cells typically exhibit negative DEP and move away from electrodes, with the transition to positive DEP occurring at f_xo1 - where the cells move towards high field regions at the electrodes. A transition back to negative DEP occurs at f_xo2 (~150 MHz). The dielectric properties of the cell membrane and cell interior can be evaluated from knowledge of the dielectric properties of the suspending fluid, and changes of the physico-chemical properties of the suspending fluid can be used to control the frequencies f_xo1 and f_xo2. 

Theoretical and experimental evaluations of f_xo1 have been extensive and exploited in practical applications of DEP [1-5]. The current status of this, both in research and commercial exploitation, will be reviewed in this presentation. The factors that control the high frequency DEP cross-over at f_xo2 are now under investigation. The status of the ‘exploration of this 2^nd frontier of DEP research’ will be described. 

1. Pethig, R. Review Article - Dielectrophoresis: Status of the theory, technology, and applications. Biomicrofluidics  4, 022811 (2010).

2. Pethig, R.; Menachery, A.; Pells, S.; de Sousa, P. Dielectrophoresis: A review of applications for stem cell research. J. Biomed. Biotechnol., e182581 (2010).

3. Gagnon, Z.R. Cellular dielectrophoresis: Applications to the characterization, manipulation, separation and patterning of cells. Electrophoresis 32: 2466-2487 (2011).

4. Pethig, R. Dielectrophoresis: An assessment of its potential to aid the research and practice of drug discovery and delivery. Adv. Drug Deliv. Rev. 65: 1589-1599 (2013).

5. Gascoyne, P.R.C. and Shim, S. Isolation of circulating tumor cells by dielectro-phoresis, Cancers 6: 545-579 (2014).