Metabolic viability of Escherichia coli trapped by dielectrophoresis in microfluidics

Abstract

The spatial and temporal control of biological species is essential in complex microfluidic biosystems. In addition, if the biological species is a cell, microfluidic handling must ensure that the cell's metabolic viability is maintained. The use of DEP for cell manipulation in microfluidics has many advantages because it is remote and fast, and the voltages required for cell trapping scale well with miniaturization. In this paper, the conditions for bacterial cell (Escherichia coli) trapping using a quadrupole electrode configuration in a PDMS microfluidic channel were developed both for stagnant and for in-flow fluidic situations. The effect of the electrical conductivity of the fluid, the applied electric field and frequency, and the fluid-flow velocity were studied. A dynamic exchange between captured and free-flowing cells during DEP trapping was demonstrated. The metabolic activity of trapped cells was confirmed by using E. coli cells genetically engineered to express green fluorescent protein under the control of an inducible promoter. Noninduced cells trapped by negative DEP and positive DEP were able to express green fluorescent protein minutes after the inducer was inserted in the microchannel system immediately after DEP trapping. Longer times of trapping prior to exposure to the inducer indicated first a degradation of the cell metabolic activity and finally cell death.

Alternating Current-Dielectrophoresis Collection and Chaining of Phytoplankton on Chip: Comparison of Individual Species and Artificial Communities

“…Previous studies showed that the electric field could induce damage to yeast cells or bacteria with a long time AC field application [28,41]. For example, the number of viable yeast cells was reduced by 56.8% to 89.7% with a DEP treatment longer than 4 h [28], and trapping of genetically-modified E. coli was only workable for an AC field application of less than 10 min [41]. These results demonstrate the importance of the careful selection of the AC field duration to avoid damage of cell membrane integrity.…”

Recent advances in dielectrophoresis‐based cell viability assessment

“…Since the first report of the microfabrication technique for DEP devices in 1988, the 1990s saw an explosion of implementing DEP experiments with metal microelectrodes. The microelectrodes commonly used are carbon and metals, such as gold , platinum , titanium or silicon , among which gold and platinum electrodes are ideal choices due to the stable electrochemical property.…”

Dielectrophoresis for Bioparticle Manipulation

“…In Donato S’s experiment, cells were trapped under the pDEP for a period of time. The result indicates that the cell metabolism is affected by the electric field after 10 min of exposure, while the cells no longer produce GFP after 15 min of exposure, and most of the cells died [127]. Therefore, for bioparticles, the exposure time in the electric field must be controlled.…”