Biomolecular Electronics Experiments Using Nanoscience and Biophysics from an Undergrad Perspective

The scanning tunneling microscope (STM) was the first artifact capable of non-destructively imaging matter with an atomic-scale resolution. Over 30 years ago, Gerd Binning and Heinrich Rohrer shared the Nobel Prize for Physics for inventing the first STM¹. Beyond topographic imaging, STM offers the possibility of spectroscopic measurements with high resolution (atomic in many cases). This opened the door to single-molecule electrical measurements².<br/>The scientific community was astounded when the electronic conductance of individual molecules bound between electrodes could be measured reliably³ using the scanning tunneling microscope break junction (STMBJ) method. The STMBJ method is a powerful technique for creating single-molecule junctions and studying charge transport in biomolecules. In this method, the current is measured while the STM tip is brought into contact with the sample and retracted from the substrate surface several times⁴. The current recorded <i>(l</i>) can be related to conductance (G) by G = I/V, with V being the voltage, and conductance histograms can be constructed by acquiring thousands of curves to determine an individual molecule's conductance⁵. On the other hand, the current-time method provides less yield and is used to study the spontaneous formation of molecular junctions⁴. STM has applications in a variety of other disciplines, including biophysics⁶ and biomedicine⁵. From the biophysics perspective, it can be used to detect biomolecular interactions electrically⁷. On the other side, from the biomedicine perspective, it could be used to detect detrimental diseases such as cancer and COVID and its variants⁵<br/>In this contribution/Herein, we show an overview of the STMBJ method applied to the study of biomaterials and individual biomolecules⁶ from an undergraduate perspective, in the context of the immersive scholars UML summer challenge. The results include high-resolution STM substrate imaging in air and buffered solution and preliminary trials on molecules and biomolecules. These results, potential problems, and alternative solutions open the doors to further develop STM, automatizing and miniaturizing it to make it a widespread user-friendly nanotechnology tool.<br/><br/>References<br/>1. Binning, Gerd, and Heinrich Rohrer, “Scanning tunneling microscopy.” Surface science 126.1-3. (1983): 236-244.<br/>2. Mzoughi T. Salem Press Encyclopedia of Science, 2022, 6p, 89317201. Scanning Tunneling Microscopy And Atomic Force Microscopy.<br/>3. Nichols RJ. STM studies of electron transfer through single molecules at electrode-electrolyte interfaces. Electrochimica Acta. 2021;387. doi:10.1016/j.electacta.2021.138497<br/>4. Lee W, Reddy P. Creation of stable molecular junctions with a custom-designed scanning tunneling microscope. Nanotechnology. 2011;22(48):485703. doi:10.1088/0957-4484/22/48/485703<br/><i>5. J. Mater. Chem. B</i>, 2021,9, 6994-7006. RNA Biomolecular Electronics: towards new tools for biophysics and biomedicine.<br/>6. Chandra, S., Arachchillage, K. G. G., Kliuchnikov, E., Maksudov, F., Ayoub, S., Barsegov, V., & Artes Vivancos, J. M. (2022). Single-Molecule conductance of double-stranded RNA oligonucleotides. Nanoscale, 14(7), 2572-2577.<br/>7. Chandra, S., Arachchillage, K. G. G., Kliuchnikov, E., Maksudov, F., Castillo, A., Barsegov, V., & Artes Vivancos, J. M. (2022). Base-mediated electrical conductance through individual single-stranded RNA molecules. In preparation.