INTERFACIAL BIONANOSCIENCE AT TBILISI STATE UNIVERSITY: ACHIEVEMENTS AND PERSPECTIVES FOR GEORGIA
Nanoscience and its component, bionanoscience, are modern interdisciplinary research “super-domains”, compulsory conceptual platforms for the development of the related domains of nanotechnology and bionanotechnology. These fields began to emerge in the 1960s, however they developed as essential constituents of well-funded strategic policies only at the beginning of the 21st c, and especially in highly developed and/or rapidly developing countries such as the USA, EU, Japan, Israel, China and India. The prefix “nano” and the abbreviation “nm” are the shortened variants of the term “nanometer”, indicating one-billionth part of a meter (10–9m). At the beginning of the development of these disciplines the terms “nanoscopic matter” or “mesoscopic matter” were used for categories of matter with dimensions of 100 nm or less. Subsequently, however, it was discovered that the borderline between “nano” and “normal” matter could be calculated much lower at around 10, or even 1 nm!
The outstanding and innovative specificity of nano-dimensional research „super-domains“ resides in the range of physical and/or chemical characteristics that may differ significantly on both sides of a “nanoscopic” borderline, even in the case of a homogeneous substance (such as a metallic piece). It should be emphasized that the dimensions of biologically active macromolecules such as DNA, proteins, lipids as well as their constituent, activity-decisive components fall within the nanoscopic dimensional range. Consequently, in some sense biomolecules can be considered as nanoparticles or assemblies of nanoparticles. Even so, today the main objects of contemporary bionanoscience and bionanotechnology are hybrid “supramolecular” assemblies which, along with essential biomolecules or their fragments/components, also include synthetic chemical molecules (commonly, polymers) and possibly nanometer-size conductive (metallic) and/or semi-conductive particles. The virtually unlimited capability of creation of these multifunctional super-assemblies provide a solid basis for their current and future bionanotechnological applications.
Pic. The figure represents a hybrid nanoscale system that has been thoroughly studied very recently with the active involvement of the TSU scientific team. It includes the well-known protein myoglobin as an active component (the upper part), self-assembled organic film (the middle part), and the bearing platform that is a golden electrode (the lower part). The so-called heme group (in yellow) with the iron ion in the center (dark violet) is clearly visible, as are several transient positions and the proposed trajectory for a removable water molecule (red balls and pink broken arrow, respectively). The two-sided vertical solid red arrow depicts the shortest pathway for electron self-exchange.
Source: D.E. Khoshtariya, et al. J. Phys. Chem. B., 2014, v.118, 692-706.
The diversity of all the realizable studies within the research fields of bionanoscience and bionanotechnology is immeasurable. We focus here only on international research involving the Institute for Biophysics and Bionanosciences at the Faculty of Exact and Natural Sciences at I. Javakhishvili Tbilisi State University (TSU). These research efforts within the interdisciplinary subfield of Interfacial Bionanoscience were initiated between 2000-2003 by Professor Dimitri Khoshtariya with colleagues from the Universities of Erlangen (Germany) and Pittsburgh (USA). These joint research projects were supported and funded by the Alexander von Humboldt and Volkswagen Foundations (Germany), the National Research Council (NRC) and the Fulbright Foundation (USA). Since 2009, the year that at TSU the faculty Institute for Biophysics and Bionanosciences was founded, projects implemented by this group in collaboration with the Department of Biophysics, the I. Beritashvili Center of Experimental Biomedicine, have also been regularly supported by the Shota Rustaveli National Research Foundation of Georgia.
Interfacial bionanosystems are biologically active hybrid nanometer-sized devices. They have redox-active biomolecules that are typically incorporated at the perfectly tunable border of ordered (solid metallic platform coated by self-organized organic film) and disordered (liquid or semi-liquid) phases. To some extent, these devices mimic the native assemblies working inside the living cells. They have an advantage against their mono-phase (homogeneous liquid-phase) analogs since they can permit electron exchange between the biological object (active center) under study and the metallic carrying platform (the modified electrode). This implies that the biological function of the biomolecule under study is either an outer-sphere transfer of the “free” electron, or that the electron transfer is involved in a more complex process, for example in the well-known enzymatic process of chemical transformation of glucose. The electron exchange (transfer) process with the electrode gives rise to a well-pronounced voltammetric (Faradaic) signal. An adequate analysis of this signal is then provided within the framework of a fast-scan methodology for cyclic voltammetry of up to 1000 volts per second. What is most important for this kind of device is the application of insulating organic films as spacers of changeable thicknesses, placed between the redox protein and metallic electrode, allowing for a smooth variation of the charge (electron) transfer distance with the extremely high accuracy of one Angstrom (i.e., the steps of 0.1 nm: nearly of the carbon atom diameter).
To illustrate, the enclosed figure represents a hybrid nanoscale system that has been thoroughly studied very recently with an active involvement of the TSU scientific team.1 It includes the well-known protein myoglobin as an active component (the upper part), self-assembled organic film (the middle part), and the bearing platform that is a golden electrode (the lower part). The so-called heme group (in yellow) with the iron ion in the center (dark violet) is clearly visible, as are several transient positions and the proposed trajectory for a removable water molecule (red balls and pink broken arrow, respectively). The two-sided vertical solid red arrow depicts the shortest pathway for electron self-exchange.
In the framework of several international joint research projects, extensively applying the mentioned experimental methodology called “Protein Film Voltammetry”, Professor Khostariya’s group investigated the intrinsic “elementary” mechanisms of electron exchange with organic film-modified gold electrodes for a number of redox-active proteins. These included cytochrome c (Cyt-c), azurin (Az) and myoglobin (Mb). The thickness of insulating organic films created through the self-assembling routine protocol varied at an accuracy of 0.1 nm. The results of systematic investigations with the combined application of a series of physico-chemical approaches including variations of temperature, pressure and viscosity (latter through the changable composition of the solution) convincingly indicated for the first time that the physical nature of biomolecular electron transfer has to be transformed between two limiting regimes through the artificially tunable change of the charge transfer distance over the range of 1-2 Angstroms. This conclusion is having a tremendous impact on the further development of some key fundamental subfields of bionanoscience and its bionanotechnological applications.
This research illustrates h ow TSU’s scientific team, together with its partners, is carrying out leading edge investigations within the modern interdisciplinary research field of interfacial bionanoscience. These investigations are a reasonable prerequisite for the initiation and extensive development of the accompanying domain of interfacial bionanotechnology in Georgia. For this to happen, however, official recognition of these innovative developments as a national priority and systematic implementation of respective governmental policy must take place. This has been the case in other technologically developed and steadily developing countries. Why are these developments for Georgia and the whole world so critical? The author’s answer rests on the following theses:
(a) According to projections by world-renowned scientists, it has become increasingly obvious that future nanotechnologies, including pollution-free utilization of solar energy and the earth’s biofuels, the fabrication of bio-sensors and immuno-sensors etc. will rest on interfacially-inspired bionanoscience, which in turn is based on the profound understanding of quantum-mechanical phenomena of charge (electron and/or proton) translocations.
(b) Trial investigations within the fields of interfacial bionanoscience and bionanotechnology are basically inexpensive and rest mainly on the world’s and country’s intellectual potential, not their industrial ability; hence with a reasonably minimal support they can be developed steadily with potentially revolutionary results.
(c) Therefore, developments within the fundamental and applied fields and specifically of interfacial bionanoscience and bionanotecnology are probably the best and perhaps the only serious prerequisites for the enhanced economic development of Georgia and for its rapid integration into the EU community.
Materials on research conducted by Dimitri Khoshtariya and his coworkers have been published in well-known scientific journals and as the book chapters, among which should be mentioned the following:
D.E. Khoshtariya, T.D. Dolidze, M. Shushanyan, & R. van Eldik, Long-range electron transfer with myoglobin immobilized at Au/mixed-SAM junctions: Mechanistic impact of the strong protein confinement. J. Phys. Chem. B. (ACS), 2014, v.118, 692-706.
D.H. Waldeck & D.E. Khoshtariya, Fundamental studies of long- and short-range electron exchange mechanisms between electrodes and protein In: Modern aspects of Electrochemistry. Applications of Electrochemistry and Nanotechnology in Biology and Medicine V.52, (N. Elias, Ed.) Springer Publishers, 2011, Chapter 2, p.105-238.
D.E. Khoshtariya, T.D. Dolidze, M. Shushanyan, K.L. Davis, D.H. Waldeck & R. van Eldik, Fundamental signatures of short- and long-range electron transfer for azurin functionalized at Au/alkanethiol SAM junctions, Proc. Natl. Acad. Sci. USA, 2010, v.107, p.2757-2762.
D.E. Khoshtariya, J. Wei, H. Liu, H. Yue, & D. H. Waldeck, The charge-transfer mechanism for cytochrome c adsorbed on nanometer thick films. Distinguishing frictional control from conformational gating. J. Am. Chem. Soc., 2003, v.125, p.7704-7714.