Ionic liquids as capping agents of silver nanoparticles. Part II: Antimicrobial and cytotoxic study

Ahmad Gholami,Abbas Abbaszadegan,Mahdi Sedigh Shams,Mohammadreza Nabavizadeh

doi:10.1515/gps-2021-0054

Ahmad Gholami, Abbas Abbaszadegan + Show 2 more

Open Access

https://doi.org/10.1515/gps-2021-0054

Copy DOI

Abstract

Abstract This study was performed to validate the previous antimicrobial and cytotoxic data on the influence of ionic liquids as coatings of silver nanoparticles (AgNPs). The antibacterial and cytotoxicity assessments were carried out against different microorganisms and a cancerous cell line. AgNPs with two different ionic-liquid coatings and hydrocarbon chains were synthesized and characterized. We tested the antibacterial activity of these NPs against Salmonella typhi, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Candida albicans in planktonic forms and against Enterococcus faecalis and Escherichia coli in biofilm forms. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay was employed for toxicity evaluation. The antimicrobial activity of NPs with 12 carbons was significantly higher than those with 18 carbons. Furthermore, NPs with 12 carbons were also effective against bacterial biofilms. All of the NPs tested had good cell viability at different antimicrobial concentrations. The length of the hydrocarbon chain is an essential factor in determining the antimicrobial activity of ionic-liquid-coated AgNPs. The variation in ionic-liquid coatings was not as effective as other influencing factors. Evaluation of AgNPs using other alkyl chain lengths to find the optimal size is recommended.

Highlights

Owing to the indiscriminate use of antibiotics and the related multiple antibiotic resistance of pathogenic microorganisms, the need to search for new strategies to restrain these pathogens is essential [1,2].Among different nanoparticles, silver nanoparticles (AgNPs) have shown antimicrobial features against a broad range of microorganisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi [3,4,5,6]
The coating of the AgNP surface with organic compounds such as Ionic liquids (ILs) can inhibit particle aggregation and, enhance the positive charges at the surface of NPs thereby causing changes in the zeta potential value, which is defined as the potential difference between the surface of a solid particle immersed in a conducting liquid and the bulk of the liquid [16]. Considering these hypotheses, we initially examined the effect of charges on the surface of the imidazolium (Im)-coated AgNPs on their level of antimicrobial activity against different microorganisms
The zeta potential distribution and the transmission electron microscopy (TEM) images of the synthesized NPs are illustrated in Figures 2 and 3

Summary

Introduction

Silver nanoparticles (AgNPs) have shown antimicrobial features against a broad range of microorganisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi [3,4,5,6]. It is shown that these agents demonstrate superior properties when particle sizes range between 5 and 50 nm [8]. The main proposed mechanisms of action for antimicrobial activity of AgNPs are the release of silver ions, generation of reactive oxygen, and damage to the cell membrane [9,10,11]. The positively charged NPs tend to attract negatively charged bacterial cell walls, causing them to accumulate inside the membrane, penetrate the cells, and eventually damage the bacterial cell walls [12,13]

Methods

Results

Conclusion