The Effects of Different Ionic Liquid Coatings and the Length of Alkyl Chain on Antimicrobial and Cytotoxic Properties of Silver Nanoparticles

Introduction: The antibacterial efficacy and toxicity of silver nanoparticles (AgNPs) depends on their physicochemical properties including size, shape, surface charge and surface coatings. The Objectives of this study were: i) To synthesize and characterize positively charged AgNPs coated by different ionic-liquids with different alkyl chain lengths, ii) To evaluate the antimicrobial activity of these nanoparticles against Enterococcus faecalis compared to sodium hypochlorite (NaOCl) and chlorhexidine (CHX), iii) To compare the cytocompatibility of these solutions against L929 mouse fibroblasts. Methods and Materials: AgNPs with positive surface charges capped by two different ionic liquids [imidazolium (Im) and pyridinium (Py)] with two alkyl chain lengths (C12 and C18) were synthesized. Im and Py were also tested as control groups. The characterization revealed synthesis of spherical NPs in the size range of 6.7-18.5 nm with a surface charge ranging from +25 to +58 mV. To standardize the comparisons, the surface charge to radius ratio of each nanoparticle was calculated. The minimum inhibitory concentrations (MIC) of the AgNP solutions, NaOCl and CHX were determined against E. faecalis by a microdilution test. An MTT-based cytotoxicity assay evaluated the cytotoxicity of the solutions in different concentrations on L929 fibroblasts. One-way and two-way ANOVA were used for statistical analysis. Results: All tested AgNPs reached MIC90 in significantly lower concentrations compared to CHX and NaOCl. C12 Py-coated AgNPs had the lowest MIC90 value. CHX and NaOCl were more toxic on fibroblasts than all tested AgNPs. Im-coated AgNPs had better compatibility with fibroblasts than Py-coated particles; and C12 Im AgNPs had the best biocompatibility. Variations in alkyl chain length had no effects on the biocompatibility of AgNPs. Conclusion: Py improved the antibacterial efficacy of AgNPs compared to Im; however, it had a negative effect on cytocompatibility. Alkyl chain length had no effects on AgNPs’ bioactivity.Keywords: Antibacterial Agents; Chlorhexidine; Cytotoxicity; Metal Nanoparticles; Sodium Hypochlorit

The Effect of Charge at the Surface of Silver Nanoparticles on Antimicrobial Activity against Gram-Positive and Gram-Negative Bacteria: A Preliminary Study

The bactericidal efficiency of various positively and negatively charged silver nanoparticles has been extensively evaluated in literature, but there is no report on efficacy of neutrally charged silver nanoparticles. The goal of this study is to evaluate the role of electrical charge at the surface of silver nanoparticles on antibacterial activity against a panel of microorganisms. Three different silver nanoparticles were synthesized by different methods, providing three different electrical surface charges (positive, neutral, and negative). The antibacterial activity of these nanoparticles was tested against gram-positive (i.e., Staphylococcus aureus, Streptococcus mutans, and Streptococcus pyogenes) and gram-negative (i.e., Escherichia coli and Proteus vulgaris) bacteria. Well diffusion and micro-dilution tests were used to evaluate the bactericidal activity of the nanoparticles. According to the obtained results, the positively-charged silver nanoparticles showed the highest bactericidal activity against all microorganisms tested. The negatively charged silver nanoparticles had the least and the neutral nanoparticles had intermediate antibacterial activity. The most resistant bacteria were Proteus vulgaris. We found that the surface charge of the silver nanoparticles was a significant factor affecting bactericidal activity on these surfaces. Although the positively charged nanoparticles showed the highest level of effectiveness against the organisms tested, the neutrally charged particles were also potent against most bacterial species

Identification of the Source of Geographical Origin of Iranian Crude Oil by Chemometrics Analysis of Fourier Transform Infrared Spectra

In this paper, we analyzed the crude oils of five different regions of Iran to identify their sources of geographical origin. The Fourier transform infrared (FTIR) spectra of samples were analyzed by chemometrics methods to make discrimination between the different crude oil sources. Infrared (IR) spectroscopy in conjunction with chemometrics techniques allows for online monitoring in real time, which can be of considerable use in the petroleum industry. Principal component analysis (PCA) and extended canonical variates analysis (ECVA), as unsupervised and supervised classification methods, respectively, were employed. The PCA scores made a relative discrimination between the different crude oil sources; however, the degree of classification was not satisfactory. Instead, more accurate classification results were achieved by ECVA. The results show that the spectral region 1350–1490 cm^–1 possessed much better performances for classification by ECVA. This spectral region, which is attributed to the SO, aromatic CC, and methylene C–C vibrations, suggests that the difference between crude oils of these geographical origins is primarily attributed to the difference in sulfoxide and aromatic compounds. The ECVA technique was found as a promising classification model and has shown good classification power for crude oil sources