Antioxidant and Antimicrobial Activity of Protein-AgNPs from the Stem of Nicotiana Tabacum

Background: Stems of Nicotiana tabacum have secondary metabolites with antimicrobial and antioxidant properties. The purpose of the present study was to investigate the therapeutic properties of synthesized silver nanoparticles (Protein-AgNPs) in an isolated protein mixture from stems. Methodology: A N. tabacum protein mixture was used for the formation of silver nanoparticles by the bioreduction method. Characterization of Protein – AgNPs was completed using UV-Vis spectroscopy, Dynamic Light Scattering (DLS), Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM). Therapeutic properties of Protein-AgNPs were evident with antimicrobial and antioxidant activities. The antimicrobial activity of Protein-AgNPs was determined by the agar well diffusion and broth diffusion methods. The mode of action of Protein-AgNPs was determined by the cellular membrane leakage assay. Antioxidant activities of Protein-AgNPs were quantified by Superoxide Dismutase activity (SOD), Catalase activity (Cat), Glutathione S Transferase activity (GST), Glutathione Content (GSH) and lipid peroxidation. Results: The synthesized Protein-AgNPs were less than 100nm as characterized by UV-Vis spectroscopy, DLS, AFM and SEM. Antimicrobial activity was observed against both Gram positive and Gram negative bacteria, revealing maximum antimicrobial activity against Staphylococcus aureus and Acinetobacter baumannii (p value ≤ 0.05) as determined by the agar well diffusion method and the broth dilution method. The mode of action is likely to be cellular membrane damage, because protein and nucleic acid leakage was significant in treated cells. The antioxidant activities of Protein-AgNPs were higher than purified proteins as determined by Superoxide Dismutase activity (SOD), Catalase activity (Cat), Glutathione Stransferase activity (GST), Glutathione content (GSH) and lipid peroxidation. Conclusion: Synthesized silver nanoparticles from a tobacco stem protein mixture can be utilized as a herbal remedy or as a nano-drug delivery system against diseases such microbial pathogens.