Sol–gel-based silver nanoparticles-doped silica – Polydiphenylamine nanocomposite for micro-solid-phase extraction

Thin-film solid-phase microextraction of pesticides from cereal samples using electrospun polyvinyl alcohol/modified chitosan/porous organic framework nanofibers

In this study, a coating of electrospun polyvinyl alcohol/modified chitosan/hydroxy-containing porous organic framework (PVA/MCS/HC-POF) was fabricated and applied as a novel sorbent for thin-film solid-phase microextraction of pesticides from cereal samples, followed by HPLC-UV. The successful fabrication of PVA/MCS/HC-POF was confirmed through characterization tests. The functional group of MCS and a large number of hydroxyl groups on the HC-POF structure contributed to the co-extraction of pesticides. Under the optimum conditions, the calibration plots were linear within the range of 5.0-800 ng mL-1 (r2 ≥ 0.978), and the limits of detection were obtained below 4.0 ng mL-1. The method's precision was investigated through intra-day, inter-day, and film-to-film RSD (%) measurements, all of which were less than 6.5 %, 8.2 %, and 10.0 %, respectively. Furthermore, satisfactory recoveries ranging from 63.3 % to 79.0 % were obtained. Accordingly, the proposed method can be considered a suitable alternative for measuring trace amounts of pesticides in cereal samples.

Biosynthesized Silver Nanoparticles from Eruca sativa Miller Leaf Extract Exhibits Antibacterial, Antioxidant, Anti-Quorum-Sensing, Antibiofilm, and Anti-Metastatic Activities

Worldwide, the primary problem today is the proliferation of cancer and secondary bacterial infections caused by biofilms, as they are the principal causes of death due to the lack of effective drugs. A great deal of biological activities of silver nanoparticles (AgNPs) have made them a brilliant choice for the development of new drugs in recent years. The present study was conducted to evaluate the anticancer, antibacterial, anti-QS, and antibiofilm effects of AgNPs synthesized from Eruca sativa (E. sativa) leaf extract. The ultraviolet–visible (UV–Vis) spectra showed a peak of surface plasmon resonance at 424 nm λmax, which corresponded to AgNP formation. The Fourier transform infrared spectroscopy (FT-IR) confirmed that biological moieties are involved for the development of AgNPs. Moreover, transmission electron microscopy (TEM) analyses confirmed the spherical shape and uniform size (8.11 to 15 nm) of the AgNPs. In human lung cancer cells (A549), the anticancer potential of AgNPs was examined by the MTT [3-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, scratch assay, and invasion assay. The results indicated that AgNPs inhibit the migration of A549 cells. The synthesized AgNPs showed MIC values of 12.5 µg/mL against Chromobacterium violaceum (C. violaceum) and 25 µg/mL against Pseudomonas aeruginosa (P. aeruginosa), which demonstrated their antibacterial abilities. Biological compounds that disable the QS system are being investigated as potential strategies for preventing bacterial infections. Thus, we analyzed the potential effectiveness of synthesized AgNPs in inhibiting QS-regulated virulence factors and biofilm formation in both strains of bacteria. In C. violaceum, the synthesized AgNPs significantly inhibited both violacein (85.18% at 1/2 × MIC) and acyl homoserine lactone (78.76% at 1/2 × MIC). QS inhibitory activity was also demonstrated in P. aeruginosa at a sub-MIC concentration (1/2 × MIC) by a reduction in pyocyanin activity (68.83%), total protease (68.50%), LasA activity (63.91%), and LasB activity (56.40%). Additionally, the exopolysaccharide production was significantly reduced in both C. violaceum (65.79% at 1/2 × MIC) and P. aeruginosa (57.65% at 1/2 × MIC). The formation of biofilm was also significantly inhibited at 1/2 × MIC in C. violaceum (76.49%) and in P. aeruginosa (65.31%). Moreover, a GC–MS analysis confirmed the presence of different classes of bioactive phytochemical constituents present in the leaf extract of E. sativa. On the basis of our results, we conclude that biologically synthesized AgNPs showed numerous multifunctional properties and have the potential to be used against human cancer and bacterial biofilm-related infections.

Green and Facile Synthesis of Pullulan-Stabilized Silver and Gold Nanoparticles for the Inhibition of Quorum Sensing

Pullulan (Pull) decorated with monodisperse Ag and Au nanoparticles (NPs) was synthesized by a simple and green method. Samples were characterized by FTIR, UV–vis, NMR, XRD, TGA, SEM, XPS, DLS, and TEM. SEM images showed highly oriented microforms reported for the first time for Pull, because of the supramolecular self-assembling behavior of Pull chains. Antimicrobial and quorum sensing (QS) inhibition activities were tested against six pathogen bacteria and reporter and biomonitor strain. Pull decorated with NPs, in particular, Ag-modified ones, outperformed pristine Pull. The cell proliferation was tested with an MTT assay. NPs-decorated Pull was studied for the first time as an inhibitory agent against bacterial signal molecules and found to be a good candidate. The promising performance of AgNPs@Pull compared to the commercial antibiotic gentamicin showed that it has great potential as a therapeutic approach to overcome the bacterial resistance that has developed against conventional antibiotics.

Green synthesis of silver nanoparticles using terrestrial fern (Gleichenia Pectinata (Willd.) C. Presl.): characterization and antimicrobial studies

Novel silver nanoparticles from Gleichenia Pectinata (Willd.) C. Presl. was synthesized. A combination of spectroscopic and microscopic techniques were utilized to characterize the newly synthesized Gleichenia Pectinata Silver Nanoparticles (GPAgNPs) vis-à-vis UV-Vis Spectroscopy, Fourier Transform Infra-Red (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX) and X-Ray Diffraction (XRD) Analyses. Significant absorption was observed at 460 nm resulting from the surface Plasmon resonance (SPR). A rapid rate of synthesis was observed and the best surface plasmon resonance was obtained at 105 minutes contact time. SEM and TEM showed an spherical shape of GPAgNPs with an average size of 7.51 nm. The XRD result revealed a crystalline and polydispersed GPAgNPs. GPAgNPs were effective against four antibiotic resistant pathogens and they exhibited excellent antimicrobial activity against Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and Candida albicans. GPAgNPs favorably competed with standard antibiotics. This therefore enlisted GPAgNPs as potential antimicrobial and therapeutic agents against multidrug resistant micro-organisms (MDRM).

Ag-Based nanocomposites: synthesis and applications in catalysis

Ag-Based nanocomposites, including supported Ag nanocomposites and bimetallic Ag nanocomposites, have been intensively investigated as highly efficient catalysts because of their high activity and stability, easy preparation, low cost, and low toxicity. Herein, we systematically summarize and comprehensively evaluate versatile synthetic strategies for the preparation of Ag-based nanocomposites, and outline their recent advances in catalytic oxidation, catalytic reduction, photocatalysis and electrocatalysis. In addition, the challenges and prospects related to Ag-based nanocomposites for various catalytic applications are also discussed. In light of the most recent advances in Ag-based nanocomposites for catalysis applications, this review provides a comprehensive assessment on the material selection, synthesis and catalytic characteristics of these catalysts, which offers a strategic guide to build a close connection between Ag nanocomposites and catalysis applications.

Antimicrobial and anticancer activities of silver nanoparticles synthesized from the root hair extract of Phoenix dactylifera

There is a continuous rise in the rate of medicine consumption because of the development of drug resistance by microbial pathogens. In the last one decade, silver nanoparticles (AgNPs) have become a remarkable choice for the development of new drugs due to their excellent broad-spectrum antimicrobial activity. In the current piece of work, we have synthesized AgNPs from the root extract of Phoenix dactylifera to test their antimicrobial and anti-cancer potential. UV-visible spectra showed the surface plasmon resonance peak at 420 nm λ_max corresponding to the formation of silver nanoparticles, FTIR spectra further confirmed the involvement of biological moieties in AgNPs synthesis. Moreover, XRD analysis showed the crystalline nature of AgNPs and predicted the crystallite size of 15 to 40 nm. Electron microscopy analyses confirmed their spherical shape. In addition, synthesized AgNPs was also found to control the growth of C. albicans and E. coli on solid nutrient medium with 20 and 22 mm zone of inhibition, respectively. The 100% potency at 40 μg/ml AgNPs concentration was observed against E. coli and C. albicans after 4 h and 48 h incubation respectively. Importantly, AgNPs were also found to decrease the cell viability of MCF7 cell lines in vitro with IC₅₀ values of 29.6 μg/ml and could act as a controlling agent of human breast cancer. Based on our results, we conclude that biologically synthesized AgNPs exhibited multifunctional properties and could be used against human cancer and other infectious diseases.

Advances in organic-inorganic hybrid sorbents for the extraction of organic and inorganic pollutants in different types of food and environmental samples

The efficiency of the extraction and removal of pollutants from food and the environment has been an important issue in analytical science. By incorporating inorganic species into an organic matrix, a new material known as an organic-inorganic hybrid material is formed. As it possesses high selectivity, permeability, and mechanical and chemical stabilities, organic-inorganic hybrid materials constitute an emerging research field and have become popular to serve as sorbents in various separaton science methods. Here, we review recent significant advances in analytical solid-phase extraction employing organic-inorganic composite/nanocomposite sorbents for the extraction of organic and inorganic pollutants from various types of food and environmental matrices. The physicochemical characteristics, extraction properties, and analytical performances of sorbents are discussed; including morphology and surface characteristics, types of functional groups, interaction mechanism, selectivity and sensitivity, accuracy, and regeneration abilities. Organic-inorganic hybrid sorbents combined with extraction techniques are highly promising for sample preparation of various food and environmental matrixes with analytes at trace levels.

Silica nanoparticle based techniques for extraction, detection, and degradation of pesticides

Silica nanoparticles (SiNPs) find applications in the fields of drug delivery, catalysis, immobilization and sensing. Their synthesis can be mediated in a facile manner and they display broad range compatibility and stability. Their existence in the form of spheres, wires and sheets renders them suitable for varied purposes. This review summarizes the use of silica nanostructures in developing techniques for extraction, detection and degradation of pesticides. Silica nanostructures on account of their sorbent properties, porous nature and increased surface area allow effective extraction of pesticides. They can be modified (with ionic liquids, silanes or amines), coated with molecularly imprinted polymers or magnetized to improve the extraction of pesticides. Moreover, they can be altered to increase their sensitivity and stability. In addition to the analysis of pesticides by sophisticated techniques such as High Performance Liquid Chromatography or Gas chromatography, silica nanoparticles related simple detection methods are also proving to be effective. Electrochemical and optical detection based on enzymes (acetylcholinesterase and organophosphate hydrolase) or antibodies have been developed. Pesticide sensors dependent on fluorescence, chemiluminescence or Surface Enhanced Raman Spectroscopic responses are also SiNP based. Moreover, degradative enzymes (organophosphate hydrolases, carboxyesterases and laccases) and bacterial cells that produce recombinant enzymes have been immobilized on SiNPs for mediating pesticide degradation. After immobilization, these systems show increased stability and improved degradation. SiNP are significant in developing systems for effective extraction, detection and degradation of pesticides. SiNPs on account of their chemically inert nature and amenability to surface modifications makes them popular tools for fabricating devices for 'on-site' applications.

Magnetic graphene-based cyanopropyltriethoxysilane as an adsorbent for simultaneous determination of polar and non-polar organophosphorus pesticides in cow’s milk

A new adsorbent based on magnetic nanoparticles (Fe₃O₄), graphene and cyanopropyltriethoxysilane was fabricated and applied to the magnetic solid phase extraction of organophosphorus pesticides.