Comparative Evaluation of Antibacterial Activity of Silver and Gold Nanoparticles Synthesized Using Some Medicinal Plants' Leaves Ethanolic Extract

Abstract

Nanotechnology is a rapidly emerging field with a wide range of biomedical science applications. Simultaneously, silver has been used as an antibacterial substance and disinfectant with few side effects. Antibacterial, antifungal, and antiviral activities are all present in silver nanoparticles.Antibiotic activity of gold nanoparticles (AuNPs) and ionic forms has been examined. Some organic Au (I & III) ion complexes have antimicrobial properties. AuNPs are antifungal, however the evidence for their antibacterial efficacy is mixed. In this study, the antibacterial activity of silver nitrate and gold chloride were examined either alone or in combination with plant ethanolic extract (Lawsonia inermis, Olea europaea) to produce LAgNPs, LAuNPs, OAgNPs, and OAuNPs. The effect was further tested against the antibacterial effect of two widely used antibiotis (ciprofloxacin "C", cephalexin "K"). The effect of a combination of the nanoparticle, ethanolic extract of either L. inermis or O. europaea, and one of the antibiotics) were examined against five of the gram negative microbial strains (Klebsiella pneumoniae, Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa and Citrobacter freundii). Silver nitrate showed a significant increase in the inhibition zone of Pseudomonas aeruginosa growth, while no effect against other bacteria. L. inermis extract only affect the growth of Klebsiella pneumonia and Escherichia coli, while LAgNPs inhibit the growth of Salmonella typhimuriumm, Escherichia coli and Pseudomonas aeruginosa significantly. The antibacterial effect of ciprofloxacin and cephalexin was enhanced when combined with LAgNPs apart from Citrobacter freundii, Klebsiella pneumonia and LAgNPs + K against Escherichia coli and LAgNPs + C against Salmonella typhimurium, while no changed was noticed against Citrobacter freundii with LAgNPs + C. for OAgNPs, no significant effect on the growth of Klebsiella pneumonia was noticed. When combined with ciprofloxacin, only Citrobacter freundii and Salmonella typhimurium showed an increase in the zone of inhibition compared to the antibiotic alone, while for cephalexin + OAgNPs, only Pseudomonas aeruginosa was affected than when using each of them independently. AuCl4 significantly inhibit the expression of Pseudomonas aeruginosa and Citrobacter freundii. Only affect
Klebsiella pneumonia and Escherichia coli. Combining the two together, LAuNPs significantly increase the zone of inhibition of only two of Bactria Pseudomonas aeruginosa and Escherichia coli. The bactericidal effect of Ciprofloxacin was enhanced when combined with LAuNPs only against Klebsiella pneumonia and Pseudomonas aeruginosa, while LAuNPs+ cephalexin inhibitory effect was only noticed against Pseudomonas aeruginosa. For O. europaea extract ethanolic extract, only Escherichia coli was affected, while both Escherichia coli and Pseudomonas aeruginosa zone of inhibition were increased when treated with OAuNPs. Using OAuNPs with Ciprofloxacin increased the growth inhibition for only Escherichia coli compared to the use of the antibiotic alone, While Pseudomonas aeruginosa and Salmonella typhimurium was the only type of bacteria affected using OAuNPs + cephalexin compared to the use of the antibiotic alone. To conclude, the synergistic effect of using the nanoparticles with the antibiotic was noticeable with only some of the bacterial types while there was no or only slight effect against other bacteria and the same applied on comparing the effect of the aqueous extract of the tested medicinal plants compared to the combination with silver nitrate or gold chloride nanoparticles.