Antibacterial activity, morphology, and physicochemical stability of biosynthesized silver nanoparticles using thyme (Thymus vulgaris) essential oil

Abstract

Considering the importance of biosynthesized silver nanoparticles (AgNPs) using plant phytochemicals, the aim of this work was to evaluate the effect of pH in the formulation of AgNPs, bioreduced with thyme essential oil. Biosynthesized AgNPs were prepared under different pH (7, 8, 9 and 10), and the physicochemical stability was evaluated during 90 days at 6°C and 25°C. Using GC/MS technique, 17 different compounds were observed in the thyme essential oil; however, borneol and αterpineol were the majoritarian compounds, probably responsible to the formation of AgNPs. UV-vis spectroscopy with absorbance between 415 and 440 nm and Transmission Electron Microscopy (TEM) confirmed the synthesis of nanoparticles, with diameters of 40 nm and spherical shapes to pH 7, 8 and 9. Through DLS approach, was observed that the average particle diameter was around 90 nm for all pH tested. AgNPs presented homogeneous size distribution, and zeta potential values very close to the theoretical stability range. Moreover, biosynthesized AgNPs presented high antibacterial activity against Escherichia coli and Staphylococcus aureus. Through x-ray Photoelectron Spectroscopic (XPS) analysis was possible confirm the presence of crystalline silver nanoparticles. Thus, silver nanoparticles eco-friendly prepared using thyme essential oil can be considered as an alternative way to produce this nanomaterial with great stability and high antibacterial activity.

Green Silver and Gold Nanoparticles: Biological Synthesis Approaches and Potentials for Biomedical Applications

“…Based on our results, we have recommended to obtain a circumspect selection of the green extracts used for the synthesis of nanoparticles, and suggested that a comprehensive screen of the products should be carried out prior to their applications to delineate their behavior in the presence of living systems. Based on today’s nanotechnology results, combining the available methods of biology, chemistry and material sciences, more complex investigations can be carried out [ 162 , 163 ]. Using such an approach, systematic examinations regarding AgNP aggregation behavior with simultaneous measurements of its effect on biological activity can be performed to offer new frontiers to preserve nanoparticle toxicity by enhancing colloidal stability [ 70 ].…”

Chitosan and silver nanoparticles are attractive auxin carriers: A comparative study on the adventitious rooting of microcuttings in apple rootstocks

“…The average zeta potential values were found to be ‐31.4 ± 1.04 mV and ‐30.3 ± 086. mV for nAg‐IAA and nAg‐IBA, respectively which show the stable colloidal structure of the nanoparticles (Figure 2B). [ 21,22 ]…”

A importância dos óleos essenciais na síntese verde de nanopartículas metálicas

“…Alguns grupos funcionais dos óleos podem interagir com diferentes íons, formando ligações que favorecem o processo de nucleação de NPs. MELO et al [30] explicaram o mecanismo de biossíntese de AgNPs com óleo essencial de tomilho (Thymus vulgaris). Segundo os autores, a reação de redução de Ag + em Ag 0 ocorreu pela doação de prótons H + do borneol (composto de maior concen-tração encontrado no óleo essencial), com a estabilização simultânea do borneol pelo sódio (Na + ) da solução percursora.…”

“…A ação redutora do óleo essencial de tomilho (Thymus vulgaris) foi aplicada na síntese de AgNPs, que foi avaliada por sua atividade antibacteriana contra Escherichia coli e Staphylococcus aureus [30]. As nanopartículas apresentaram formato esférico com tamanho médio de 90 nm, e pico de absorbância entre 415 e 440 nm.…”

“…A união de várias unidades de Ag 0 é que forma uma nanopartícula. As biomoléculas dos óleos essências além de participarem da bioredução do AgNO 3 , podem se organizar na superfície das NPs tornando-as mais estáveis [30].…”