Sunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity

Abstract

BackgroundNanotechnology is now regarded as a distinct field of research in modern science and technology with multifaceted areas including biomedical applications. Among the various approaches currently available for the generation of metallic nanoparticles, biogenic synthesis is of increasing demand for the purpose of green nanotechnology. Among various natural sources, plant materials are the most readily available template-directing matrix offering cost-effectiveness, eco-friendliness, and easy handling. Moreover, the inherent pharmacological potentials of these medicinal plant extracts offer added biomedical implementations of the synthesized metal nanoparticles.ResultsA robust practical method for eco-friendly synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum (Tulsi) as both reducing and capping agent, under the influence of direct sunlight has been developed without applying any other chemical additives. The nanoparticles were characterized with the help of UV-visible spectrophotometer and transmission electron microscopy (TEM). The prepared silver nanoparticles exhibited considerable antibacterial activity. The effects were more pronounced on non-endospore-forming Gram-positive bacteria viz., Staphylococcus aureus, Staphylococcus epidermidis, and Listeria monocytogenes than endospore-forming species Bacillus subtilis. The nanoparticles also showed prominent activity on Gram-negative human pathogenic Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and plant pathogenic Pantoea ananatis. A bactericidal mode of action was observed for both Gram-positive and Gram-negative bacteria by the nanoparticles.ConclusionsWe have developed a very simple, efficient, and practical method for the synthesis of silver nanoparticles using aqueous leaf extract of O. sanctum under the influence of direct sunlight. The biosynthesis of silver nanoparticles making use of such a traditionally important medicinal plant without applying any other chemical additives, thus offers a cost-effective and environmentally benign route for their large-scale commercial production. The nanoparticles dispersed in the mother solution showed promising antibacterial efficacy.Graphical AbstractSunlight-induced rapid and efficient biogenic synthesis of silver nanoparticles using aqueous leaf extract of Ocimum sanctum Linn. with enhanced antibacterial activity.Electronic supplementary materialThe online version of this article (doi:10.1186/s13588-014-0018-6) contains supplementary material, which is available to authorized users.

Sunlight Induced Mediated Silver Nanoparticles from Seeds of Thevetia peruviana L., Characterization and their Antifungal Efficacy against Curvularia lunata (Wakker) Boedijn

“…3). Similar result was observed by Brahmachari et al, 2014) when AgNPs were synthesized from Ocimum sanctum leaves extract but absorption maxima differed from Rupiasih et al, 2013) who used T. peruviana latex extract for the synthesis of AgNPs, where absorption maxima was 570 nm. The AFM image analysis revealed the topography, size of AgNPs.…”

Antimicrobial Effect of Silver Nanoparticles Synthesised with Ocimum Sanctum Leaf Extract on Periodontal Pathogens

“…AgNPs formed due to sunlight induction produced best results at 7% concentration against all test bacteria [35]. In our study, bactericidal activity of silver nanoparticles exhibited only against Aa even at a concentration of 3.125 µg/ml.…”

“…Contrary to this finding, silver nano particle synthesized with Ocimum sanctum by sunlight induction revealed more pronounced activity on gram positive Staphylococcus aureus, Staphylococcus epidermidis and Listeria monocytogenesis than on gram negative bacteria like Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa and Pantoea ananatis [35]. The green synthesis of silver nanoparticle using Ocimum with methanol solvent gave high & similar antibacterial activity against both gram positive & gram negative bacteria [41].…”

“…Though the leaf extract of Ocimum sanctum also could kill the bacteria but with lesser efficiency than the 10 -3 M silver nitrate solution [35].…”

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“…The silver nanoparticles synthesized from the aqueous leaf extract of Ocimum sanctum Linn also showed prominent activity on Gram negative human pathogenic Salmonella typhimurium, Escherichia coli and Pseudomonas aeruginosa 34 . The antibacterial activity of the silver nanoparticles synthesized from rhizome extract of Alpinia galangaby by microwave irradiation was investigated against the Gram positive bacteria Staphylococcus aureus and Bacillus subtilis and against the Gram negative bacteria Vibrio cholerae and Salmonella paratyphi, which showed higher antibacterial activity in both Gram positive and Gram negative organisms 35 .…”