Green synthesis of silver nanoparticles with different sizes and investigation of size-dependent antibacterial activity
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Neda Arghand,1 Somayeh Reiisi,2,*
1. sharekord university
2. Shahrekord University
- Introduction: Introduction & Aim: Nanotechnology is a modern research field about synthesis, modification, properties and usage of particles ranging from 1 to 100nm in size. Novel applications of nanoparticles and nanomaterials are developing rapidly in many areas, such as healthcare, cosmetics, biomedical, food, drug/gene delivery, environment, health, mechanics, optics, and chemical industries and etc. Currently, research regarding the interaction between nanoparticles and biomedicine is increasing, and as a result, a wide variety of inorganic nanoparticles are used for biological applications. Green synthesis of nanoparticles, as an emerging highlight of the intersection of nanotechnology and biotechnology, was attractive due to the growing need to develop environmentally benign technologies in material synthesis. The techniques for obtaining nanoparticles using naturally occurring reagents such as sugars, biodegradable polymers (chitosan, etc.), plant extracts, and microorganisms as reducing and capping agents could be considered attractive for nanotechnology. Eugenol, the main constituent of essential oils extracted from various plants, has been widely studied due to its medicinal properties, such as its antibacterial effect. Similarly, silver nanoparticles have been extensively investigated because of their antimicrobial properties alone or in combination with other compounds. In this study, different sizes of silver nanoparticles were synthesized with eugenol to compare the antibacterial effect of each nanoparticle.
- Methods: Methods: Ag nanoparticles (AgNPs) were synthesized with four different concentrations of eugenol. We prepare eugenol 10, 40, 70, 100μM eugenol in 2ml ethanol and also 20mM AgNO3 solution was prepared with 10ml distillated water. 2ml of AgNO3 solution was mixed with 46ml deionized water in each 4 dishes on the stirrer. Then we added 2ml of each concentration of eugenol to the solutions. By reaching the pH of the solution to 11, we saw the color of the solution change from colorless to blackish brown. Then we Placed the solution on the stirrer for one hour at room temperature (1000rpm). Thereafter, a blackish brown‐colored mixture was centrifuged for 20min (4000rpm) and the nanoparticles was used. Nanoparticles was assessed through dynamic light scattering and ultraviolet-visible spectroscopy. We use Escherichia coli to determine the MIC of each nanoparticle. For MIC test, different concentrations of nanoparticles (100, 150, 200, 300, 400, 500μg/μl) were prepared. Also, we prepared E. coli standard solution (include 1.5 × 108 bacteria). The MIC test was performed on 96-well plates. Three columns of plate were considered for Each nanoparticle. each concentration of nanoparticles was added in three well in each row with 20μl bacteria. Also, two rows were considered as positive control and negative control. Samples were incubated for 24 hours and then MIC was detected by bacterial turbidity in the wells.
- Results: Results: The UV-Vis results show peaks of all four samples were around 400 nm, which is a characteristic value for spherical silver nanoparticles, we have different absorbance for each nanoparticle, the nanoparticle made with eugenol 10μM have more absorbance than the other one. Also, the nanoparticle made with eugenol 10,40μM have darker than the other solutions. The DLS graphic of AgNPs showed different size of nanoparticle based on eugenol molarity. The largest nanoparticle was made with eugenol 10μM with a size of 512 nm and also the smallest synthesized nanoparticle was the nanoparticle made with eugenol 100μM with a size of 226nm. The size of nanoparticles made with eugenol 40, 70μM was 500 and 239, respectively. with an increasing concentration of eugenol, the size of the nanoparticles became smaller. The MIC of each sample was determined according to the degree of bacterial turbidity in each well compared to the negative control. MIC obtained from nanoparticles made with eugenol 10,40,70,100μM against E. coli was 100,150,400,400μM, respectively.
- Conclusion: Conclusion: Our results revealed an association between the eugenol concentration for Ag nanoparticles synthesized and nanoparticles size. The reverse association was seen in Ag nanoparticles size and antibacterial effect. These findings lead to the conclusion that aiming for the smallest possible nanoparticles might not be the best course of action, despite the general standpoint of the relevant literature.
- Keywords: Key words: nanoparticle size, silver nanoparticle, eugenol, antimicrobial effect
