Direct current electrical characterization of ds-DNA in nanogap junctions

Abstract

Measurements of DNA conductivity, hybridization, and melting using electronic means can have wide applications in molecular electronics and biological sensors. We have fabricated nanogap break-junctions by electromigration through thin gold-on-titanium films. 18-mer thiolated ds-DNA molecules were covalently attached between the electrodes and dc electrical measurements were done. The conductance was measured through the molecule before and after a temperature ramp from 300 to 400 K. A dramatic decrease in conductance was observed, analogous to an electrical fuse, possibly attributed to complete or partial denaturing of the ds-DNA molecules bridging the nanogaps. We also show evidence that the dc resistance of dry DNA strands of the same length decreases with increasing guanine-cytosine content in the sequence with values ranging from 10 M Ω to 2 G Ω. These findings can have important consequences in DNA-based molecular electronics and direct label-free detection of DNA hybridization.

In Situ Electrochemical Distance Tunneling Spectroscopy of ds-DNA Molecules

“…5 Recent studies by Tao et al 6,7 , Xu et al 8 , Bashir et al 9 , and Porath et al 10 involving single DNA molecules in two-terminal nano-gaps in the presence and absence of water further indicate that the experimental conditions strongly influence the electrical properties of DNA. Moreover, several reports indicate that the solvent and ions play a critical role in electron transport along a variety of molecules.…”

“…Thus, we can investigate the influence of the orientation of DNA within the gap on the electrical properties of the system. Unlike in two-terminal approach used previously to measure conductivity of DNA [6][7][8][9] , the electrochemically controlled STM allows for the electrochemical potentials to be applied independently and simultaneously to both the STM tip (E TIP ) and the Au (111) substrate (E Au ). 14 Figure 3 shows the distribution of current plateaus obtained from the currentdistance curves for the self-complementary ds-DNA duplex of the 5′-(GC) 7 -3′-(CH 2 ) 6 -SH sequence under the same bias voltage, ΔE=0.4 V, but using different combinations of electrochemical potentials applied to the STM tip and the Au(111) substrate.…”

Theory, fabrication and applications of microfluidic and nanofluidic biosensors

“…Electrochemical impedance spectroscopy or EIS [17][18][19] detects changes in surface or nanostructure impedance owing to surface reactions or transport. In other electrically based techniques, a surface-based reaction corresponds to a change in a measured electrical signal such as current [20][21][22][23], resistance [24][25][26], capacitance [27] or conductance [28][29][30][31][32][33][34] of the test sample. In addition, detection methods could also rely on mechanical changes induced owing to adsorption of target molecules or analytes to cantilevers [35][36][37] or nanowires [33], changes to inherent biomolecular charge in the case of field-effect transistors, sometimes also classified as microarray-type biosensors [38][39][40][41][42][43], or electrochemical changes such as those arising from redox reactions inducing variations in current flow [44,45].…”

“…The solvents are usually aqueous solutions to preserve the natural state, or after processing may be organic materials. The sensor should be able to perform the [35][36][37] nanowires change in surface charge through protonation/deprotonation [33] electrical field-effect transistors changes in inherent biomolecular charge [38,[41][42][43]51] nanowires changes in electrical signal such as current, resistance, capacitance or conductance [24][25][26][27][28][29][30][31][32][33][34] optical fluorescence intensity of fluorescent signal [3][4][5] optical cavity resonator shift in resonance wavelength proportional to change in mass [7,9] surface-plasmon resonance shift in refractive index [10,11,[13][14][15][16]52] (b) sample manipulation method underlying principle involved references pumps electrokinetic pumping (including electro-osmosis) valves surface modification [53] droplets transfer electrically controlled surface tension drives liquid droplets [54,55] arrays/mixing of fluids use of heterogeneous surfaces (e.g. use of nanoholes or modified surfaces) [56,57] a As discussed in the text, many of the mechanisms can be combined with sample manipulation techniques in table 1b in microfluidic or nanofluidic platforms or can be used as stand-alone methods.…”

Label-free direct electronic detection of biomolecules with amorphous silicon nanostructures

“…These biochips have already improved the speed and sensitivity of bioanalysis in the micron-scale in detection of DNA (6)(7)(8)(9) and proteins (10). The detection of DNA is of importance because of applications in drug development, in identification of pathogens, and in genetic screening.…”