Docent Dr. Jussi Toppari, Department of Physics / Nanoscience Center, Jyväskylä, Finland, University of Jyväskylä

Possible Conductivity of Self-assembled DNA Structures? 

The most crucial part in the realization of functional molecular scale devices is to find suitable building blocks or scaffolds for nanoscale patterning. For the moment, DNA has been proven to be a very flexible and promising molecule for this. In the respect of the long history and debate on the possibly conductivity of DNA, the electrical properties of DNA-structures themselves are also of a great interest. However, to be able to measure the electrical properties and to exploit the full potential of the bottom-up DNA-nanotechnology, one needs to position these constructs on the chip in a controllable way. We have demonstrated that dielectrophoresis (DEP) can be efficiently utilized to trap DNA molecules and self-assembled structures, such as DNA origami [1].

We have studied the conductance of individual origami structures and TX-tile assemblies by impedance spectroscopy (IS) as well as DC-current measurements, and found that the conductance is very low in dry conditions on a surface, but increases significantly in high humidity [2,3]. Data analysis also suggest that the water molecules play a big role in the conductance, which suggests that the new 3D DNA origami structures may have an improved conductance due to their compact inner structure that can hold more organized water molecules. In addition, the outer helices can keep the inner helices in a more ideal environment. To explore this, several different shapes of 3D DNA origami structures were trapped and studied [4]. The electrical measurements revealed the conductivity to be mostly negligible in dry as well as in humidity. Interestingly, however, the trapping process of a brick-like origami equipped with thiol-linkers induced an etched “nanocanyon” in the silicon dioxide substrate exactly at the location of the DEP trapped origami.

We have also utilized a DNA-structure consisting of TX-tiles as a scaffold for arranging a row of three gold nanoparticles. After trapping the structure between nanoelectrodes the particles act as metallic islands of a single electron transistor (SET). The electrical measurements revealed clear Coulomb Blockade even at room temperature on couple of samples.

1. P. W. K. Rothemund, Nature 440 (2006) 297-302.
2. V. Linko, S.-T. Paasonen, A. Kuzyk, P. Törmä, and J.J. Toppari, Small 5, 2382–2386 (2009).
3. V. Linko, J. Leppiniemi, S.-T. Paasonen, V.P. Hytönen, and J.J. Toppari,Nanotechnology 22, 275610(2011).
4. B. Shen, V. Linko, H. Dietz and J.J. Toppari, To appear in Electrophoresis (DOI: 10.1002/elps.201400323).

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