Search

Herein, a simple and selective electrochemical method was developed for sulfadimethoxine detection based on the triggered cleavage activity of nuclease P1 by the formation of aptamer and sulfadimethoxine conjugate. After probe DNA was immobilized on gold electrode surface, aptamer DNA labeled with biotin at its 5′-terminal was then captured on electrode surface through the hybridization reaction between probe DNA and aptamer DNA. The formed double-stranded DNA (dsDNA) can block the digestion activity of Nuclease P1 towards the single-stranded probe DNA. Then, the anti -dsDNA antibody was further modified on electrode surface based on the specific interaction between dsDNA and antibody. Due to the electrostatic repulsion effect and steric-hindrance effect, a weak electrochemical signal was obtained at this electrode. However, in the presence of sulfadimethoxine, it can interact with aptamer DNA, and then the formation of dsDNA can be blocked. As a result, the probe DNA at its single-strand state can be digested by Nuclease P1, which leads to the failure of the immobilization of anti -dsDNA antibody. At this state, a strong electrochemical signal was obtained. Based on the change of the electrochemical signal, sulfadimethoxine can be detected with linear range of 0.1–500 nmol/L. The detection limit was 0.038 nmol/L. The developed method possesses high detection selectivity and sensitivity. The applicability of this method was also proved by detecting sulfadimethoxine in veterinary drug and milk with satisfactory results. Image 1 • Electrochemical method was developed for sulfadimethoxine detection. • Aptamer was employed to specific recognition of sulfadimethoxine. • Signal improvement can be achieved after the formation of aptamer-target conjugate. • Sulfadimethoxine in veterinary drug and milk was detected. [ABSTRACT FROM AUTHOR]

Abstract In this study, conducting polyaniline (PAni) and silicon dioxide (SiO 2) nanocomposites (NCs) were synthesized for chemical sensing applications by microwave assisted reaction technique. Facile synthesis and characterization of the PAni-SiO 2 nanocomposites were investigated in details and discussed in this report. For the potential application, 1,4-dioxane chemical sensor was fabricated with the PAni-SiO 2 nanocomposites deposited onto glassy carbon electrode (GCE). A very thin uniform film was deposited onto GCE with nanocomposite by using conducting 5% nafion binder at room conditions. To evaluate the sensor analytical performances, a calibration plot such as current versus concentration of 1,4-dioxane was drawn and calculated the analytical parameters from the slope of calibration curve. Results are found as sensitivity (0.5934 µAµmol-1 L−2 cm−2), detection limit (16.0 ± 0.8 pmol L−1), and quantification limit (LOQ; 53.3 ± 1.5 pmol L−1) in this observation. Considering the linear region in calibration plot, the linear dynamic range of 1,4-dioxane chemical sensor was found (0.12 nmol L−1 ∼ 1.2 mmol L−1). Besides this, the proposed 1,4-dioxane chemical sensor was exhibited good reproducibility, long-term stability, high accuracy in detecting of 1,4-dioxane in real environmental samples. This research is to develop of a selective and an efficient electrochemical sensor. It might be a simple and easy way by applying electrochemical method to ensure the safe and sustainable green environment. Graphical abstract fx1 Highlights • PAni-SiO 2 nanocomposites prepared by microwave method. • Highly sensitive 1,4-dioxane chemi-sensor by reliable electrochemical method. • Chemi-sensor exhibits the lower detection limit within short response time. • Practically analyzed the real environmental samples. • Effective chemi-sensor for health care and environmental fields. [ABSTRACT FROM AUTHOR]

Small molecules that may facilitate and stabilize the formation of G-quadruplexes can be used for cancer treatments, because the G-quadruplex structure can inhibit the activity of telomerase, an enzyme over-expressed in many cancer cells. Therefore, there is considerable interest in developing a simple and high-performance method for screening small molecules binding to G-quadruplex. Here, we have designed a simple electrochemical approach to screen such ligands based on the fact that the formation and stabilization of G-quadruplex by ligand may inhibit electron transfer of redox species to electrode surface. As a proof-of-concept study, two types of classical G-quadruplex ligands, TMPyP4 and BRACO-19, are studied in this work, which demonstrates that this method is fast and robust and it may be applied to screen G-quadruplex ligands for anticancer drugs testing and design in the future. [ABSTRACT FROM AUTHOR]

Abstract: We reported a rapid toxicity assay method using electrochemical biosensor for pesticides, Escherichia coli (E. coli) was taken as a model microorganism for test. In this method, we adopted ferricyanide instead of natural electron acceptor O2, and then microbial oxidation was substantially accelerated. Toxicity assays measured the effect of toxic materials on the metabolic activity of microorganisms. The current signal of ferrocyanide produced from the metabolism was proven to be directly related to the toxicity, which could be amplified by ultramicroelectrode array (UMEA). The ratio of the electrochemical signals, recorded in the presence and absence of toxin, provided an index of inhibition. Accordingly, a direct toxicity assessment (DTA) based on chronoamperometry was proposed to detect the effect of toxic chemicals on microorganisms. 3,5-Dichlorophenol (DCP) was taken as the reference toxicant, its IC50 was estimated to be 8.0mg/L. Three pesticides were examined using this method. IC50 values of 6.5mg/L for Ametryn, 22mg/L for Fenamiphos and 5.7mg/L for Endosulfan were determined and in line with EC50 values reported in the literature. Atomic force microscopy (AFM) was also used for morphology characterization of E. coli induced by three pesticides. These results confirmed the present electrochemical method used is reliable. In addition, the electrochemical method is a sensitive, rapid and inexpensive way for toxicity assays of pesticides. [Copyright &y& Elsevier]

Abstract: This work described the development and characterization of an electrochemical method using square wave voltammetry (SWV) combined with the use of modified magnetic nanoparticles (MNPs), which had shown a rapid and sensitive determination of ochratoxin A (OTA) in wine grapes (Cabernet Sauvignon, Malbec and Syrah) post-harvest tissues. The wine grapes were inoculated with Aspergillus ochraceus to obtain OTA in artificially infected samples. The OTA was directly determined using square-wave voltammetry. The current obtained is directly proportional to the concentration of OTA present in the samples. This method has been used for OTA determination in wine grapes and it was validated against a commercial ELISA test kit. The limits of detection calculated for electrochemical detection and the ELISA were 0.02 and 1.9μgkg−1, respectively and the coefficients of variation for accuracy and precision dates were below 5.5%. This method promises to be suitable for the detection and quantification of OTA in apparently healthy fruits post-harvest for assuring safety and quality of food as well as consumer''s health. [Copyright &y& Elsevier]

Infectious diseases are a potential risk for public health and the global economy. Fast and accurate detection of the pathogens that cause these infections is important to avoid the transmission of the diseases. Conventional methods for the detection of these microorganisms are time-consuming, costly, and not applicable for on-site monitoring. Biosensors can provide a fast, reliable, and point of care diagnostic. Nanomaterials, due to their outstanding electrical, chemical, and optical features, have become key players in the area of biosensors. This review will cover different nanomaterials that employed in electrochemical, optical, and instrumental biosensors for infectious disease diagnosis and how these contributed to enhancing the sensitivity and rapidity of the various sensing platforms. Examples of nanomaterial synthesis methods as well as a comprehensive description of their properties are explained. Moreover, when available, comparative data, in the presence and absence of the nanomaterials, have been reported to further highlight how the usage of nanomaterials enhances the performances of the sensor. [Display omitted] • Fast detection of infectious disease is crucial to avoid fast human to human transmission. • We provide a comprehensive overview of most applicable nanomaterials in biosensors. • The review covered electrochemical, colorimetric, fluorescence, SERS, and lateral flow biosensor used antibodies and aptamers. • We emphasis how the usage of nanomaterials can influences the performances of the immunosensors and aptasensors. [ABSTRACT FROM AUTHOR]