Mechanism of Antioxidant Activity of Selenium Nanoparticles Obtained by Green and Chemical Synthesis.

Background: Selenium nanoparticles (SeNPs) show high therapeutic potential. SeNPs obtained by green synthesis methods, using commonly available plants, are an attractive alternative to nanoparticles obtained by classical, chemical methods. The green synthesis process uses environmentally friendly reagents, which offer an eco-friendly advantage. Clarifying their mechanism of action is key to their safe use. Methods: The study used SeNPs obtained using extracts of sage, hops, blackberry, raspberry, and lemon balm, without the use of additional stabilizers, and nanoparticles chemically obtained with ascorbic acid and gallic acid, stabilized with polyvinyl alcohol. The study was carried out on a model strain of Escherichia coli. In the study, the activities of the key enzymes catalase (CAT), superoxide dismutase (SOD), and the response of bacterial cells to osmotic shock were determined. Results: One of the key mechanisms of action of SeNPs is related to the formation of ROS in bacterial cells. The SeNPs tested showed strong inhibition of CAT, an enzyme crucial for bacterial cells that is involved in the removal of hydrogen peroxide. The tested SeNPs also had an effect on reducing the activity of superoxide dismutase (SOD), which is also involved in the removal of reactive oxygen species from cells. Green SeNPs were also shown to be involved in the cellular response to osmotic shock, confirming their pleiotropic mechanism of action in bacterial cells. Conclusion: NPs synthesized via green methods exhibit antibacterial activity against E. coli. The green synthesis process employs environmentally friendly reagents, offering a pro-ecological advantage. Notably, these nanoparticles are strongly stabilized by the post-reaction mixture, eliminating the need for toxic stabilizers. Their antimicrobial mechanism involves ROS generation, catalase (CAT) inhibition, and reduced SOD activity, affecting ROS defense and by disrupting the cellular response to osmotic shock.