Manipulation and trapping of sub-micron bioparticles using dielectrophoresis

Abstract

A non-uniform alternating electric field induces motion in polarisable particles called dielectrophoresis. The effect is governed by the relative magnitudes of the dielectric properties of the medium and the particles. The technology has been used to manipulate particles for biotechnological applications, including purification, fractionation and concentration of cells and microorganisms. However, the lower size limit for the dielectrophoretic manipulation of particles was believed to be about 1 m, but recent work has proved otherwise. The dielectrophoretic movement and properties of latex beads and a simple rod-shaped virus, tobacco mosaic virus (TMV), have been measured using microfabricated electrode structures. Measurements have been made over a range of suspending medium conductivities, applied frequencies and electric field strengths. It is shown that under appropriate conditions both latex beads and tobacco mosaic virus particles can be selectively attracted to regions of high electric field strength located at the tips of microfabricated electrode structures. The ability to selectively trap and separate bio-particles has many potential applications in the area of biotechnology. © 1997 Elsevier Science B. V.

Dielectric spectroscopy of Tobacco Mosaic Virus

“…Solutions of TMV were prepared in KCl and in HEPES buffer, pH 7.0, at a range of conductivities or molarities. Virus concentration was estimated spectrophotometrically using the published extinction coefficient for a 1 mg ml À 1 solution of E 280 = 3.0 [23]. Volume fractions of the different concentrations of TMV solutions were estimated using the density quoted above.…”

“…Dielectrophoresis is the movement of a polarisable particle in a nonuniform alternating electric field [23,26]. In order to observe the dielectrophoretic behaviour of the particle, the virus was fluorescently labelled.…”

Dielectrophoretic manipulation of rod-shaped viral particles

“…The preparation and fluorescent labelling of the virus has been described in detail elsewhere [23]. Labelled virus was concentrated by ultracentrifugation for 1 h at 2000009 and re-suspended in potassium phosphate buffer, pH 7.2.…”

Determination of pathogenic bacteria by CZE with surface‐modified capillaries

“…Unfortunately, the same situation in medical diagnosis of pathogenic bacteria is observed because traditional colony counts methods are always slow (up to 72 h). Obviously, there are some new technologies such as: PCR detection [2], flow cytometry [3,4], differential staining [5], serological methods and recently dielectrophoresis [6][7][8][9][10][11][12][13][14][15][16][17], or microchipbased technology [18]. For instance, PCR method is extremely sensitive, however requires pure samples and hours of analysis and expertise in molecular biology.…”