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DNA Zippers Pave the Way Toward Self-Restoring Electronic Devices

DNA zipper configuration has enabled scientists to design novel single-molecule junctions with high conductance and self-restoring capability.

Nearly every cell in a multicellular organism possesses the full set of deoxyribonucleic acid (DNA), which forms the genetic code. However, modern-day technology has taken DNA one step beyond living matter. Scientists are now exploring the structural, physical, and chemical properties of DNA at the nanoscale for the prospect of using this double helix molecule as a building block in nanoscience and molecular electronics. They have since established that the intricate structures of DNA show potential for use in new-age electronic devices with junctions comprising just a single DNA molecule.

However, the strength of single-molecule conductance seemed to be inversely proportional to the length of the molecule. Only extremely short stretches of DNA can be used for electrical measurements. Now, in a breakthrough study by researchers from the Tokyo Institute of Technology, they have come up with a way around this problem and achieved high conductivity with a long DNA molecule-based junction in a “zipper” configuration that also shows a remarkable self-restoring ability under electrical failure.

“We investigated electron transport through the single-molecule junction of a ‘zipper’ DNA that is oriented perpendicular to the axis of a nanogap between two metals. This single-molecule junction differs from a conventional one not only in the DNA configuration but also in orientation relative to the nanogap axis,” explained Dr. Tomoaki Nishino from Tokyo Tech, Japan, who was part of the study.

By using a 10-mer and a 90-mer DNA strand, the team formed a zipper-like structure and attached them to either a gold surface or to the metal tip of a scanning tunnelling microscope, an instrument used to image surfaces at the atomic level. The space between the tip and the surface constituted the “nanogap” that was modified with the zipper DNA. The team then estimated the conductivity of the DNA junctions against a bare nanogap without DNA by measuring a quantity called “tunnelling current” across the nanogap.

To explain the underlying “unzipping” dynamics of the junctions, the scientists conducted molecular dynamics simulations. Their experiments revealed that the single-molecule junction with the long 90-mer DNA showed an unprecedented high conductance due to a system of delocalised pi electrons that could move around freely in the molecule. But more importantly, the simulations suggested that the single-molecule junction could restore itself – from an unzipped to a zipped state or vice versa – spontaneously after an electrical failure, thereby showing that the junction is both resilient and easily reproducible.

With these optimistic discoveries, the team is excited about possible future ramifications in the technology. They believe that further functionalisation could be possible by using a long DNA sequence as a scaffold to form conjugates with a wide range of functional biomolecules.

“The strategy presented in our study could provide a basis for innovations in nanoscale electronics with superior designs of single-molecule electronics that could likely revolutionise nanobiotechnology, medicine, and related fields,” speculated Dr. Nishino. [APBN]

Source: Harashima et al. (2021). Single-molecule junction spontaneously restored by DNA zipper. Nature Communications, 12, 5762.