LS-6-P-5972 Dielectrophoresis for single-virus force spectroscopy

It is possible to use the atomic force spectroscopy technique for manipulation of single virus particles [1]. To do this a virus particle needs to be attached to the tip of atomic force microscope’s probe. A dielectrophoresis (DEP) is a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field [3]. The direction and magnitude of DEP force are the functions of frequency of the electric field. These functions are defined by electrical properties of the particle. It is possible to use positive DEP (a movement of particles to electrodes) for attaching a single virus particle to the conductive AFM probe’s tip for the force spectroscopy measurements.

A curvature radius of conventional gold-coated AFM probe’s tip is not more than 35 nm (Fig. 1). During the experiments the small (60 nm) virus-like particles and virions with size from 100 nm (influenza virus) to 350 nm (vaccinia virus) were used. The AFM tips (CSG01/Au, NT-MDT, Russia) were flattened by the scanning of silicon or sapphire surfaces in contact mode with high load, high scan speed, and a large scanning area. This procedure creates a flat area at the tip [2]. The AFM probe’s tips were examined by transmission electron microscopy (JEM 1400, Jeol, Japan) with custom-made TEM holder.

It has been proved that this method is useful for attaching the virus particles (influenza, vaccinia, etc.) to the tip of AFM probe. The results were verified by a TEM examination of the AFM tips.

REFERENCES

1. D. Alsteens, E. Pesavento, G. Cheuvart, V. Dupres, H. Trabelsi, P. Soumillion, Y.F. Dufrene, Controlled manipulation of bacteriophages using single-virus force spectroscopy, ACS Nano, 2009, 3(10), pp. 3063-3068.
2. C.L. Cheung, J.H. Hafner, C.M. Lieber, Carbon nanotube atomic force microscopy tips: Direct growth by chemical vapor deposition and application to high-resolution imaging, PNAS, 2000, 97(8), pp. 3809–3813.
3. H.A. Pohl, Dielectrophoresis, Cambridge University Press, Cambridge, 1978.