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
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.