In vitro Antimicrobial Activity of Biogenically Synthesized Nickel and Zinc Nanoparticles against Selected Pathogenic Bacterial Strains.

Bacterial resistance to already present antibiotics demands for new approaches in field of medicine. Scientists prefer nanoparticles (NPs) due to their promising potential in many applications. Two bacterial strains, Escherichia coli and Bacillus subtilis were used for biogenic synthesis of NPs. Characterization of prepared NPs was accomplished using UV-vis spectroscopy and fourier transform infrared spectroscopy (FTIR). The prepared NPs were confirmed by the color change from pale yellow to having white deposition for Zn NPs while from dark green to light green for Ni NPs. UV-vis spectroscopy of E. coli and B. subtilis based ZnNPs showed highest peak at 354nm and 362nm, respectively. Likewise, E. coli and B. subtilis NiNPs showed peaks at 246 nm and 238 nm, respectively. Antibacterial activity of B. subtilis based ZnNPs showed significant (p ≤ 0.05) zone of inhibition (ZOI; 27.3±0.6) against B. subtilis and 26.66±0.67 against E. coli at 100 mg/mL. Antibacterial activity of E. coli based ZnNPs showed 8.3±0.3 ZOI against B. subtilis and 6.6±0.3 ZOI against E. coli while NiNPs showed (25.0±0.0 mm) (ZOI) against B. subtilis and (25.0 ± 0.3 mm) against E. coli. Minimum inhibitory concentration (MIC) of E. coli ZnNPs showed values of 6.7±0.3 μg/mL for E. coli and 4.7±0.3 μg/mL for B. subtilis. MIC of B. subtilis ZnNPs showed 5.3±0.3 μg/mL for E. coli and 6.6±0.3 μg/mL for B. subtilis while NiNPs showed 33.0±1.0 μg/mL against E. coli and 24.0±1.0 μg/mL against B. subtilis as effective inhibitory concentrations. Minimum bactericidal concentration (MBC) of E. coli ZnNPs showed 7.3±0.3 μg/mL for E. coli and 8.3±0.3 μg/mL for B. subtilis. MBC of B. subtilis ZnNPs showed 7.6±0.3 μg/mL for E. coli and 8.6±0.3 μg/mL for B. subtilis while NiNPs showed 45.7±1.3 μg/mL against E. coli and 33.0±1.0 μg/mL against B. subtilis as effective inhibitory concentrations. It was concluded from the current study that biogenically synthesized ZnNPs and NiNPs are effective as promising antibacterial agents and have potential applications in biomedical fields.