Inhibition of Staphylococcus Bacteria by Ag Nanoparticles Under Plasmon Resonance

The antimicrobial activity of colloids of Ag nanoparticles (NPs) with a diameter of 90 and 7 nm in a quercetin shell, obtained by thermal reduction and chemical reduction of NaBH4, was studied. Colloids exhibited antimicrobial activity against a test culture of S. aureus. At the same time, NPs of smaller sizes showed antimicrobial activity more effectively (at lower concentrations of the solution). The additional irradiation of the colloid solutions covered by quercetin Ag NPs with a diameter of 7 nm on the S. aureus test culture was also studied. The SF26 spectrophotometer was used as a radiation source to determine the effect on S. Aureus under LSPR conditions of NPs. The SF26 spectrophotometer can manually select the wavelength and radiation intensity. It allows us to irradiate the maximum volume of solutions. The sample was irradiated with light with a wavelength of 380 nm, corresponding to the resonance frequency of NPs in the solution. The transmission band was 15 nm. The control sample was stored in the absence of external irradiation (in the dark) and under the same conditions as the irradiated one. The samples were irradiated for 110 minutes. Then, the irradiated and control samples were sown on Petri dishes with a solid nutrient medium and incubated in a thermostat at 37 °C for 24 hours. After that, we compared the seeds of irradiated and control samples. A relative decrease in the growth of the population of S. aureus bacteria in the culture of irradiated samples was found. The enhancing effect of additional external irradiation under the conditions of surface plasmon resonance of NPs was determined (by 33 percent). The authors associate this effect of irradiation with the physical (field) interactions of NPs and bacteria.