Antibacterial Effect of Nanostructured Gold Surface under Surface Plasmon Resonance Conditions

Neutralizing bacteria and viruses has been a critically important problem for the last decades. At the same time, today, the main means and methods for neutralization are the use of chemicals and heat treatment. One of the disadvantages of chemical drugs is the ability of viruses and microbes to adapt to the mechanism of action of chemicals through mutagenesis [1]. The phenomenon of acquired resistance to various drugs due to mutations in genes is common to various viruses and bacteria [2,3]. Therefore, the search for drugs that use other non-chemical effects and mechanisms to neutralize the infectious activity of pathogens is relevant. 

It is well known that different types of nanoparticles occupy an important place in nanomedicine. A striking feature of the antiviral and antimicrobial action of nanoparticles is their universality - small nanoparticles fabricated from different materials demonstrate antiviral/antimicrobial activities. The main idea of the study is the assumption that the effect of nanoparticles on viruses and microbes is of a field nature, and due to the effect of local field enhancement, a region of a strongly inhomogeneous local field is formed on the surface of viruses/microbes, which leads to the formation of ponderomotive forces that, acting on the envelope of the virus/microbe, greatly reduce their infectious activity, up to the destruction of the envelope. The surface of a real solid is not perfectly flat. It is more correct to consider the surface as a plane covered with nanoscale protrusions. Therefore, the surface of a solid is nanostructured. Under the action of surface plasmon, the adsorption potential of viruses/microbes onto the surface is significantly enhanced [4], and thus the action of nanoparticles and nanostructured surfaces under plasmon resonance conditions can be controlled to be enhanced. The study of the physical interaction of viruses and microbes with nanostructured surfaces under plasmon resonance conditions aims to clarify the features of such interaction for further application in the development of technology for neutralizing bacteria and viruses.

The work is devoted to the search for the enhancement of the antimicrobial action of the nanostructured gold surface under plasmon resonance conditions. The Plasmon-6 plasmon resonance spectrometer was used for the experiments. The surface plasmon was excited by light with a wavelength of 625 nm in the Kretschmann mode. The best effect of the antibacterial action was achieved when the prism is in the position at the angle of plasmon resonance. The reference strain of the conditionally pathogenic gram-positive Staphylococcus aureus ATCC 6538 was used as a test culture. Suspensions of bacteria in physiological solutions were used for the study. It was achieved that up to 80% of the bacteria were neutralized in the suspension under conditions for excitation of surface plasmons on the gold surface.