No abstract

Silver nanoparticles (AgNPs) are popular consumer product additives due to their well-known antimicrobial properties. Nowadays, their usage has increased after the emergence of green synthesis method with less toxicity than conventional methods. In this study, we aimed to reveal the antimicrobial potential of phytosynthesized AgNP by Laurus nobilis L. extracts against different Gram-positive, Gram-negative bacteria as well as Candida albicans ATCC 10231. Phyto-synthesized AgNPs were characterized by scanning electron microscopy, zeta size-potential analysis, UV-Visible spectroscopy and FT-IR analysis. The results showed that the size of AgNP was 50 nm and coated by phyto-constituents such as phenolic compounds according to FT-IR results. The antimicrobial activity of AgNP was determined by MIC and MBC tests. The results pointed that green synthesized AgNPs are effective against various microorganisms.

Silver nanoparticles (AgNPs) are made up about 55% of all nanomaterials produced and are widely used in consumer products. Its is inevitable that these particles are released to the aquatic environment during production, use and disposal. In this study, subacute toxicity of AgNPs obtained by phyto-synthesis was investigated on Lemna minor L. (duckweed) plants. The formation of AgNPs obtained from laurel (Laurus nobilis L.) extract was determined by UV-VIS spectrophotometric measurements. The AgNPs synthesized by the phytosynthesis method were characterized by Fourier transform infrared spectroscopy (FT-IR), Zeta size and potential, Inductively Coupled Plasma Mass Spectrometry and Scanning electron microscopy (SEM-EDS) analysis. The analysis results show that AgNPs are homogeneously distributed, spherical in shape with an average size of 34 nm and coated with phyto-content. For toxicity tests, plant stock cultures were grown in the climate room according to OECD 221 guidelines. After 8 weeks of acclimation, the plants were treated with AgNP concentrations ranging from 0.005 to 50 mg L −1 for 7-and 14-days. The increase in AgNP concentration caused a decrease in frond numbers. Growth inhibition data showed that the EC50 value of phyto-synthesized AgNP was 4.78 mg L -1 and the lowest observed effect concentration (LOEC) was 0.5 mg L -1 for 7-days. AgNP concentrations below LOEC level (0.05, to 0.5 mg L -1 ) caused a significant decrease in growth rate by 20.07% after 7 days of exposure while it was found 4.03% for 14-days treatment at the highest AgNP concentration (0.5 mg L -1 ). Similar trend was observed in fresh-and dry weight of plants indicating prolonged exposure time triggering tolerance mechanism which was corroborated by chlorophyll a/b and carotenoids content results. Based on higher NOEC, LOEC and EC50 values, phyto-synthesized AgNP usage may lead less environmental toxicity.

Magnetite nanoparticles (MNPs) are widely used in medicine, environmental technologies and biotechnology and green synthesis of MNPs could be an option to minimize potential environmental pollution by their usage. In this study, subacute toxicity of green synthesized magnetite (Fe3O4) nanoparticle was evaluated on Lemna minor, a main autotroph in lakes. Laurel (Laurus nobilis) leaf extract was used to synthesize the magnetite nanoparticles. Characterization of the nanoparticles were performed by UV/Vis spectrophotometer, Fourier transform infrared spectroscopy (FT-IR), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Zeta size and potential and Scanning electron microscopy (SEM-EDS) analysis. Nanoparticles were around 108.5 nm, spherical in shape and capped with phyto-content. Subacute toxicity of magnetite nanoparticle was tested according to modified OECD 221 protocol, by treating L. minor plants with different MNPs concentrations (0.1, 1, 10, 100, 1000, 2000 mg L− 1) in petri dishes containing Steinberg medium for 15 days. The MNPs up to 1000 mg L− 1 did not cause any toxic effect on Lemna minor even it promoted growth and development of the plant in the concentrations less than 100 mg L− 1. The number of fronds, colonies and photosynthetic pigment contents significantly decreased by magnetite nanoparticle application of 1000 and 2000 mg L− 1 concentrations. Moreover, in these concentrations the nanoparticle caused oxidative stress indicated by the increased hydrogen peroxide and superoxide anion content and lipid peroxidation level. As a conclusion, this study showed that 1000 mg L− 1 green synthesized MNPs concentration is the starting point of subacute toxicity for L. minor.