Selective dielectrophoretic manipulation of surface-immobilized DNA molecules

Abstract

The fabrication of nanoscale molecular devices is becoming increasingly important and research into their fabrication has intensified over the last few years. In particular, the attachment of molecular objects onto various surfaces has attracted considerable attention. Here, we report a multistep surface immobilization procedure, which allows the specific and controlled attachment of very long DNA molecules onto gold electrodes. Further, we report the effect of dielectrophoresis on these surface-bound DNA molecules with respect to amplitude and frequency, and we show that selected surface-immobilized DNA molecules can be manipulated by dielectrophoresis. Finally, we investigated the use of dielectrophoresis in conjunction with the multistep surface immobilization of fluorescently labelled, surface-bound λ-DNA in a basic data-storage device.

Influence of alternating current electrokinetic forces and torque on the elongation of immobilized DNA

“…Before immobilization of the DNA fragments onto the gold electrodes as described in detail in Ref. 24, each solution was diluted to 50 ng/ l DNA in TE (10 mM tris-HCl, 1 mM EDTA, pH 8) 1 M NaCl solution, and the YOYO-1 fluorescent intercalator (Molecular Probes, Eugene, OR, USA) was added at an intercalator to basepair ratio of 1:8. Control experiments to confirm that the DNA is tethered to the electrodes via one end only have been carried out.…”

“…The detection method used to confirm the presence of the DNA targets the biotin attached to the free end. 25 All of the control experiments, either using no oligonucleotides at all, complementary but nonthiolated, or noncomplementary oligonucleotides in the multistep procedure, 24 demonstrated that no -DNA was bound to the surface in the absence of suitable anchor molecules confirming that the DNA is tethered only via one end. Further, tethered -DNA was digested with BglII which cleaves the DNA close to the biotinylated end.…”

“…The reorientation of the charges along the backbone of the DNA starts lagging behind the switch in the polarity of the electrodes in the ac field with increasing frequencies, leading to a decrease of the effective dipole moment and thus torque. 3,24 Figure 5(a) shows the normalized length L n = L / L 0 , where L is the measured length and L 0 the contour length, of the four elongated DNA fragments as a function of frequency at an electric field of 0.5 MV/ m across a 40 m gap. As also shown before, all the different fragments were fully elongated at frequencies of 200-300 kHz.…”

“…Direct immobilization of DNA onto the electrodes prior to electric field application removes this artifact and provides a direct means of studying the effects of the electric field on the molecule. 24 In this article we present a detailed study of the effect of ac electric fields on the elongation and orientation of surfacetethered DNA molecules. We have immobilized four different-sized fragments of -DNA [15,25,35, and 48 kilobases (kb)] onto gold microelectrodes via a terminal thiol group, and measured the length of the elongated DNA as a function of electric field magnitude and frequency.…”

Dielectrophoretic capture of low abundance cell population using thick electrodes

“…In the channel, the dielectrophoretic force is mainly in competition with the drag force, F drag , and thus, dielectrophoretic trapping is generally performed at low flow rate. 7 Most of the devices dedicated to DEP trapping are realized by integrating coplanar microfabricated electrodes, with geometries consisting generally of interdigitated 8 or castellated 9 electrode arrays. However, F DEP decreases quickly as the distance from the electrode surface increases.…”