Dielectrophoretic Manipulation of DNA:  Separation and Polarizability

Abstract

Although separation of polymers based on the combination of dielectrophoretic trapping and electrophoretic forces was proposed 15 years ago, experimental proof has not yet been reported. Here, we address this problem for long DNA fragments in a simple and easy-to-fabricate microfluidic device, in which the DNA is manipulated by electrophoresis and by electrodeless dielectrophoresis. By slowly increasing the strength of the dielectrophoretic traps in the course of the separation experiments, we are able to perform efficient and fast DNA separation according to length for two different DNA conformations: linear DNA (lambda (48.5-kbp) and T2 (164-kbp) DNA) and supercoiled covalently closed circular plasmid DNA (7 and 14 kbp). The underlying migration mechanism-thermally induced escape processes out of the dielectrophoretic traps in the direction of the electrophoretic force-is sensitive to different DNA fragments because of length-dependent DNA polarizabilities. This is analyzed in a second series of experiments, where the migration mechanism is exploited for the quantitative measurement of the DNA polarizabilities. This new and simple technique allows for the systematic characterization of the polarizability not only for DNA but also for other biomolecules like proteins. Furthermore, our results have direct implications to future biotechnological applications such as gene therapy and DNA vaccination.

Size-dependent trajectories of DNA macromolecules due to insulative dielectrophoresis in submicrometer-deep fluidic channels

“…3͒, in agreement with the previously published insulative dielectrophoresis results. 5,6 Comparison between the simulation and experimental data in Fig. 5 shows that the simulation of = 200ϫ 10 −11 m kg s −7 A −3 matches the data sets with red markers, while the simulation of = 500ϫ 10 −11 m kg s −7 A −3 matches the data sets with green markers.…”

“…This scheme has been used on DNA sorting and manipulation, starting with the proposition made by Ajdari et al,4 then realized in the form of DNA trapping by Chou et al, 5 and eventually applied in DNA sorting by Regtmeier et al 6 However, this scheme relies on trapping ͑rather than directly sorting͒ the DNA molecules, and hence cannot be operated continuously and is prohibited from achieving higher throughput. 7 In this paper, we demonstrate for the first time that insulative dielectrophoresis could also be used to induce size-dependent trajectories of individual DNA molecules that are flowing continuously.…”

Simulation of electrophoretic stretching of DNA in a microcontraction using an obstacle array for conformational preconditioning

“…Most studies on the dielectrophoresis of DNA have used ac fields and created the necessary electric field gradients by placing the electrodes in close proximity to each other. There have been a few studies, however, that have considered electrodeless dielectrophoresis of DNA using microfabricated devices to shape the field lines, [50][51][52][53] and some work has even been performed on dc fields. 52,53 Chou et al 50 and Regtmeier et al 51 used arrays of obstacles to bend and concentrate the field lines between the obstacles, and using an ac field, they trapped DNA between the obstacles.…”

Tuning direct current streaming dielectrophoresis of proteins

“…15,19,20 Analytical applications of DNA DEP have been early proposed by Washizu et al 14 and recent studies revived this approach exploiting the length dependency of DNA DEP for separation. For example, a field flow fractionation device for DNA was recently demonstrated by Lao et al 21 Moreover, both the separation of linear DNA by size 22 and DNA topoisomers 23 were demonstrated in gel-free environment.…”