Antimicrobial and antifungal properties of NiCu-PANI/PVA quaternary nanocomposite synthesized by chemical oxidative polymerization of polyaniline.

Increasing antimicrobial resistance has led to use of novel technologies such as nanomaterials and nanocomposites that have shown effective antimicrobial and/or antifungal activities against several gram-positive and gram-negative bacteria. There have been limited studies on antimicrobial properties of the combined polymer nanocomposites with transitional bimetallic nanoparticles such as nickel (Ni) and copper (Cu). Thus, the main objective of this study was to synthesis, characterize and investigate the antibacterial and antifungal properties of NiCu-PANI/PVA nanocomposite. The nanocomposite films with different amount of Ni and Cu salts were synthesized by chemical oxidative polymerization of polyaniline using HCl as oxidant and PVA as a stabilizer. Optical, chemical composition, and morphological characteristics as well as thermal stability were evaluated using UV-Visible, FTIR, SEM-EDX, and TGA analyses. Antimicrobial properties were then determined using the disc diffusion assay against gram-negative bacteria (i.e., Escherichia coli ATCC 25922, Klebsiella pneumonia ATCC 700603, Proteus sp.,) and gram-positive bacteria (i.e., Staphylococcus aureus ATCC 2593). Fungal plant pathogens including Aspergillus niger and Fusarium oxysporum f. sp. pisi were also evaluated for determination of antifungal activity of NiCu-PANI/PVA films. Among the synthesized films, Ni65Cu35-PANI/PVA showed excellent antibacterial activity against all the bacteria strains examined in this study. The diameters of inhibition zones for Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 700603, Proteus sp., and Staphylococcus aureus ATCC 2593 were 23, 23, 17, and 18 mm, respectively indicating good antibacterial activities. Additionally, NiCu-PANI/PVA, particularly the films with higher Cu intake, showed better antifungal activity against Fusarium oxysporum f. sp. pisi. However, NiCu-PANI/PVA was ineffective against Aspergillus niger.

A global systematic review of the concentrations of Malathion in water matrices: Meta-analysis, and probabilistic risk assessment.

Pesticide applications and the proximity of land use to water matrices have resulted in discharges of pollutants including Malathion -one of the most widely used organophosphorus pesticides- to water resources such as marine, freshwater, and under groundwater. Exposure to malathion through consumption of contaminated water may cause deleterious health effects on consumers. Determining the amount of pesticides used on farms can play an important role in preventing potential toxicity and pollution of nearby aquatic ecosystems. Therefore, this systematic review and meta-analysis is focused on evaluating the concentrations of Malathion in water resources while considering probabilistic health risk assessment. The international databases of Scopus, Embase, and PubMed were investigated to evaluate the related articles from January 01, 1968 to March 25, 2021. Thirty-four articles containing 206 samples from 15 countries were included. A meta-analysis of carcinogenic and non-carcinogenic risk assessments for Malathion was also performed. To determine uncertainty intervals, a Monte-Carlo simulation was conducted. The results of the meta-analysis showed that the rankings of Malathion pollution (from the most to the least) were: drinking water > surface waters > groundwaters. Moreover, the results of the risk assessments confirm that there is no non-carcinogenic risk for any of the study areas. The carcinogenic risk assessment was within the limit for the countries under this study, except for Ethiopia that was slightly over the limit as well as Iran, and Mexico had high carcinogenic risk.

Biosynthesis, characterization, and evaluation of antibacterial and photocatalytic methylene blue dye degradation activities of silver nanoparticles from Streptomyces tuirus strain.

Silver nanoparticles (AgNPs) are a promising technology for the design of antimicrobial agents against drug-resistant pathogens. It could also be used for the photocatalytic degradation of dyes used in industries such as methylene blue (MB). In this study, 17 different actinomycetal strains isolated from hydrocarbon-contaminated soils collected from an oil distribution company in Algeria were evaluated for their ability to produce NPs. After a selection process, S16 was the main strain capable of synthesizing AgNPs extracellularly. The strain S16 was determined using molecular identification based on the sequencing of the 16S rDNA gene. Among various techniques used for the synthesis of AgNPS, a technique using a temperature of 30 °C, pH of 7, a metal salt concentration of 1 mM, and a period of 72 h in the dark were found to be more effective in the biosynthesis of the AgNPs. The biosynthesized AgNPs that were analyzed by UV-visible spectroscopy resulted in a specific peak at a wavelength of (λ = 400 nm). The DRX analyses showed characteristic peaks of the AgNPs at (1 1 1), (2 0 0), (2 2 2), and (3 1 1), which validated the presence and crystalline nature of the biosynthesized NPs. Zetasizer analysis showed an average size and zeta potential of 64 nm (-32.3 mV), while the SEM-EDS analysis confirmed the spherical shape of AgNPs and the presence of Ag atoms in the elemental composition. The biosynthesized AgNPs indicated adequate antibacterial activity against 5 out of the 6 strains tested in this study, using minimum inhibitory concentration (MIC) that ranged from 217.18 µg/mL to 1137.5 µg/mL. The AgNPs were combined with commercial antibiotics and the synergistic effect of the combination was also assessed against MRSA which resulted in increased antibacterial activity of AgNPs in the presence of the strain S16. Furthermore, the photocatalytic degradation of the methylene blue (MB) was evaluated under sunlight and UV irradiations using biosynthesized AgNPs. The AgNPs showed photocatalytic decolorization potential of 71.3% for MB dye (20 ppm) under sunlight irradiation within 6 h of incubation, while only 11.25% of the MB dye degraded using UV irradiation.

MXene-based electrochemical sensors for detection of environmental pollutants: A comprehensive review.

Since the discovery of MXenes at Drexel University in the United States in 2011, there has been extensive research regarding various applications of MXenes including environmental remediation. MXenes with a general formula of Mn+1XnTx are a class of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides with unique chemical and physical characteristics as nanomaterials. MXenes feature characteristics such as high conductivity, hydrophobicity, and large specific surface areas that are attracting attention from researchers in many fields including environmental water engineering such as desalination and wastewater treatment as well as designing and building efficient sensors to detect hazardous pollutants in water. In this study, we review recent developments in MXene-based nanocomposites for electrochemical (bio) sensing with a particular focus on the detection of hazardous pollutants, such as organic components, pesticides, nitrite, and heavy metals. Integration of these 2D materials in electrochemical enzyme-based and affinity-based biosensors for environmental pollutants is also discussed. In addition, a summary of the key challenges and future remarks are presented. Although this field is relatively new, future research on biosensors of MXene-based nanocomposites need to exploit the remarkable properties of these 2D materials.

Electrochemical sensor to detect terbutaline in biological samples by a green agent.

In this research, reduced graphene oxide (RGO) which is a form of graphene oxide (GO) was formed through a reduction process using a "green agent" called Ascorbic acid (AA). RGO was then modified on the surface of the glassy carbon electrode (GCE) to generate RGO/GCE (an advanced electrode). The RGO/GCE was then used to detect Terbutaline (TB) in urine samples of volunteer athletes (n = 5) using well-known spectrophotometric analyses including X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible Spectroscopy (UV-Vis), and Raman and electrochemical methods using voltammetric analyses such as differential pulse anodic stripping voltammetry (DP-ASV) and cyclic voltammetry (CV). Comparing various analysis methods using RGO/GCE to detect TB in human urine samples, voltammetric analysis specifically DP-ASV demonstrated higher sensitivity and selectivity in detecting TB than spectrophotometric analyses. Thus, in this study, several factors that would affect the voltammetric signals such as pH and interferents were evaluated and the electroactive surface area was also calculated. Our findings indicated that the RGO/GCE showed excellent repeatability, reproducibility, and long-term stability suggesting that TB could be detected more effectively using RGO/GCE than bare GCE. The detection limit of 0.0052 µM achieved in this study indicated that RGO/GCE can effectively detect TB in human urine while demonstrating reasonable selectivity and sensitivity.

Alkylated polycyclic aromatic hydrocarbons are the largest contributor to polycyclic aromatic compound concentrations in traditional foods of the Bigstone Cree Nation in Alberta, Canada.

Rising global demand for energy promotes extensive mining of natural resources, such as oil sands extractions in Alberta, Canada. These extractive activities release hazardous chemicals into the environment, such as polycyclic aromatic compounds (PACs), which include the parent polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs, and sulfur-containing heterocyclic dibenzothiophenes (DBTs). In areas adjacent to industrial installations, Indigenous communities may be exposed to these PACs through the consumption of traditional foods. Our objective was to evaluate and compare the concentrations of total PACs (∑PAC), expressed as the sum of the 16 U.S. EPA priority PAHs (∑PAH), 49 alkylated PAHs (∑alkyl-PAH), and 7 DBTs (∑DBT) in plant and animal foods collected in 2015 by the Bigstone Cree Nation in Alberta, Canada. We analyzed 42 plant tissues, 40 animal muscles, 5 ribs, and 4 pooled liver samples. Concentrations of ∑PAC were higher in the lichen, old man's beard (Usnea spp.) (808 ± 116 ng g-1 w.w.), than in vascular plants, and were also higher in smoked moose (Alces alces) rib (461 ± 120 ng g-1 w.w.) than in all other non-smoked animal samples. Alkylated-PAHs accounted for between 63% and 95% of ∑PAC, while the concentrations of ∑PAH represented 4%-36% of ∑PAC. Contributions of ∑DBT to ∑PAC were generally lowest, ranging from <1% to 14%. While the concentrations of benzo(a)pyrene (B[a]P) and ∑PAH4 (∑benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and B[a]P) in all samples were below guideline levels for human consumption as determined by the European Commission, guideline levels for the more prevalent alkylated PAHs are not available. Given the predominance of alkylated PAHs in all food samples and the potentially elevated toxicity relative to parent PAHs of this class of PACs, it is critical to consider a broader range of PACs other than just parent PAHs in research conducted close to oil sands mining activities.

Evaluating the concentrations of total mercury, methylmercury, selenium, and selenium:mercury molar ratios in traditional foods of the Bigstone Cree in Alberta, Canada.

Traditional foods provide nutritional, social, and economic benefits for Indigenous communities; however, anthropogenic activities have raised concerns about mercury (Hg), especially methylmercury (MeHg), in these foods. This issue may be of particular concern for communities near large industrial activities, including the Bigstone Cree Nation adjacent to the Athabasca oil sands region, Canada. This community-led study sought to assess variation in THg and MeHg concentrations among traditional food types (plants or animals), species, and tissues (muscles, organs), and variation in concentrations of the micronutrient selenium (Se)- thought to protect against Hg toxicity-and Se:THg ratios. Thirteen plant and animal species were collected in 2015 by Bigstone Cree community members. We quantified THg, Se, and Se:THg ratios in 65 plant and 111 animal samples and MeHg in 106 animal samples. For plants, the lichen, old man's beard (Usnea spp.), showed the highest concentrations of THg and Se (0.11 ± 0.02 and 0.08 ± 0.01 µg g-1 w. w., respectively) and also had a low Se:THg molar ratio. Concentrations of THg, MeHg, and Se differed among animal samples (P < 0.010), showing variation among species and among tissues/organs. Generally, concentrations of THg and MeHg were highest in aquatic animals, which also had relatively low Se:THg molar ratios. Overall results revealed substantial variation in the patterns of THg, MeHg, Se and Se:THg ratios across this comprehensive basket of traditional foods. Thus, measuring concentrations of THg alone, without considering MeHg and potential associations with Se, may not adequately convey the exposure to Hg in traditional foods.