Review—Where Is Dielectrophoresis (DEP) Going?

Abstract

A guide is offered to new researchers (and their supervisors) of the most promising topics to explore in market-driven or curiositydriven dielectrophoresis (DEP) research. Based on an analysis of publications since 2000, contributions from electronic engineers and materials scientists are likely to be maintained, with increasing emphasis on the development of DEP-based protocols for chemical and biochemical analyses that involve nanoparticles. Two modes of DEP are likely to dominate, namely metal-electrode based (eDEP) and insulator-based (iDEP). Where high values of the electric field and its gradient are required, such as the spatial manipulation of nanoparticles (e.g., exosomes, proteins, viruses, carbon-nanotubes), eDEP would in many cases be the preferred choice. This would also be the case for the selective isolation of biological cells; the development of cell-based drug discovery protocols; electronic sensors and the assembly of nanoparticles (e.g., carbon nanotubes). Applications of iDEP would be particularly suited for the separation or detection of bioparticles such as DNA, RNA, proteins or bacteria, where manipulation selectivity is based on differences in surface charge. Hot topics include the development of dynamic patterning of bioparticles using photoconductive electrodes, and the genome-wide mapping between genotype and DEP phenotype of cells. The motivation for conducting this analysis came from email exchanges with postgraduates commencing projects involving the electrokinetic manipulation of particles, as well as from discussions with business people and venture capitalists. Apart from seeking advice on specific technical issues, opinions were sought by postgrads regarding the "hottest' topics for investigation and the potential for long-term careers in the subject. For the more commercially minded with inbuilt risk aversion, it was appropriate to explain that dielectrophoresis (DEP) was the term coined by Herbert Pohl as far back as 1951 to describe the translational motion of an electrically polarized particle in a non-uniform electric field.1 Such interested parties also required assurances that the maturity of the technology presents low risk of failure to meet technical objectives. This can be approached by explaining that the phenomenon has been exploited since 1924 (for the separation of minerals 2 ), with a theoretical basis to be found in early 19th century text books. 3 Furthermore, various aspects of the subject are treated in text books 4-9 and review articles 10-17 that take us to the present status of DEP technology. Responses to these intended reassurances are invariably of the form: "If DEP has been around for so long and is considered such an innovative technology, why hasn't it received significant commercial exploitation?" Although this assessment may be uncomfortable to receive, the so-called Golden Rule (i.e., he who has the gold, rules) should be acknowledged.At least six commercial products incorporating DEP can be cited. For example, the Panasonic bacteria counter dete...

Dielectrophoretic deformation of breast cancer cells for lab on a chip applications

“…1, where the highest electric field region is located at the tips of the curved microelectrodes. Pearl-chaining is also described as mutual DEP [28] and occurs when the electrostatic interactions between polarized cells rebalance their electrical potential energies [29]. MDA-MB-231 cells in 1% DMEM solution experience positive DEP which is confirmed by the responses of Cell A and B in Figs.…”

“…3, cell C is already in contact with cell D and rotates towards cell E to form a chain-like formation which is known as pearl chaining [27]. Pearl-chaining is also described as mutual DEP [28] and occurs when the electrostatic interactions between polarized cells rebalance their electrical potential energies [29]. Cells naturally have repulsive forces between opposing membrane surfaces which are known as electrostatic repulsion and hydration repulsive forces [30].…”

Dielectrophoretic analysis of treated cancer cells for rapid assessment of treatment efficacy

“…DEP spectra were obtained from each experiment, and were then modelled to extract the dielectric properties. The modelling was performed by varying parameters to find the best fit (highest Pearson correlation coefficient) between the data points and a model of the composite dielectric properties of a shelled particle , as related through a mathematical operation called the Clausius‐Mossotti factor . This is frequency dependent, such that measuring the DEP behaviour at different frequencies and fitting a model to these points allows the estimation of the electrical properties of the cells.…”

Technological developments in dielectrophoresis and its path to commercialization

“…In the following years, many variants of this separation technology were published, presenting multiple separation outputs [22], vertical electrodes [23] and more, and several cell types used; several excellent review can be found describing both technology and applications elsewhere (e.g., [24]). However, this period did not see the advancement of DEP separation outside of engineering departments; it could be argued that there was a disconnection between the technology providers and the ultimate end users.…”