The use of biosynthesized silver nanoparticles from Klebsiella pneumonia as antioxidants and anti-bacterial agents

Aims: This study was aimed at the biosynthesis of silver nanoparticles (AgNPs) from Klebsiella pneumonia and the evaluation of their anti-bacterial and antioxidant activities.Methodology and results: Silver nitrate was used for the biosynthesis of silver-nanoparticles, and UV-visible spectrophotometer, X-ray diffraction, scanning electron microscope and Fourier transforms infrared spectroscopy were used for the characterization of AgNPs. Results showed colour changes of bacterial supernatant from pale yellow to dark brown, indicating the biosynthesis of AgNPs. The biosynthesis of AgNPs was confirmed using UV-visible spectrophotometry, which shows a strong peak at 420 nm. Infrared spectroscopy was also used, which revealed that the carboxyl and phenolic groups were coated on the surface of AgNPs. The results of the electron microscope scanning showed that AgNPs are spherical and have a size range from 35-100 nm. On the other hand, the antioxidant activity of AgNPs was done in vitro by adding the nanoparticles to the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) solution. The absorbance was measured at 517 nm after 30 min in dark conditions. The results revealed a significant increase (P<0.05) in free radicals reduction at five concentrations of AgNPs (30, 60, 120, 240 and 480 mu g/mL). Finally, the antibacterial activity of AgNPs against Escherichia coli and Pseudomonas aeruginosa was studied. The results revealed a significant increase (P<0.05) in the diameter of the inhibition zone of bacterial growth at 200 mu g/mL AgNPs compared to the inhibition zone at 50 and 100 mu g/mL AgNPs. The minimum inhibitory concentration of AgNPs was determined. It was 30 mu g/mL of P. aeruginosa and 16 mu g/mL of E. coli.Conclusion, significance and impact of study: The preliminary study results suggest that AgNPs have anti-bacterial activity as well as the ability to inhibit free radicals, making them a potential antioxidant source. However, further research is required.