Eco-friendly synthesis, characterization and biological evaluation of silver nanoparticles using Ylang-Ylang oil and Tea-tree oil

Abstract Application of silver nanoparticles (AgNPs) in healthcare products to prevent/treat bacterial infections has gained popularity in the recent past. Nevertheless, the full utilization of chemically-synthesized AgNPs in biomedical field was constrained by the utilization of chemical reagents, which contaminates the environment and threatens human health. Herein, two herbal oils, i.e., Ylang-Ylang Oil (YO) and Tea Tree Oil (TO) were adopted to synthesize green-bioactive AgNPs. Besides promoting the synthesis of eco-friendly nanoparticles, the phytochemicals present in herbal oils can enhance the antibacterial properties, leading to improved efficacy of AgNPs against a broader range of pathogens. The biosynthesized YO-AgNPs and TO-AgNPs were characterized using SPR, FTIR, zeta size, zeta potential and SEM, and evaluated for their DPPH radical scavenging and antibacterial potentials. Characteristic SPR peaks for YO-AgNPs and TO-AgNPs were observed at 470 nm and 430 nm, respectively. FTIR spectra of the biosynthesized AgNPs suggested the capping of AgNPs by biomolecules present in YO and TO. The average size for YO-AgNPs was 163.1 ± 9.8 nm with zeta potential of −21.1 ± 2.8 mV, whereas the average size for TO-AgNPs was estimated as 92.4 ± 7.2 nm with zeta potential of −22.5 ± 3.6 mV. The SEM images showed polygonal YO-AgNPs, and cauliflower aggregates of spherical TO-AgNPs. Moreover, DPPH assay estimated IC 50 of 47.2 μg ml −1 for YO-AgNPs, and 22.6 μg ml −1 for TO-AgNPs. The MIC 50 analysis showed that both biosynthesized AgNPs were more active against gram-negative ( E. coli ) than gram-positive ( S. aureus ) strains. Most importantly, TO-AgNPs was comparatively more potent than YO-AgNPs as well as positive control (streptomycin), with an MIC 50 value of 20.5 μg ml −1 and 25.9 μg ml −1 against E. coli and S. aureus , respectively. To sum up, TO-AgNPs displayed the potential to be developed into a broad-spectrum antibacterial agent, alleviating the toxicity issues associated with the use of AgNPs in healthcare products.