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Lysozyme (Lys) commonly presents in wines and are known to cause toxicological impact on human health. The need of highly sensitive and reliable detection methods are evident in such matrix. In this work, we developed a competitive aptamer based assay for detection of Lys by employing carboxylated magnetic beads as a support to immobilize the target molecule Lys. The used aptamer sequence was biotinylated...
The present article describes a portable and low cost fluorescence set-up designed and characterized for in-situ screening of Ochratoxin A (OTA) in cocoa samples at field settings. The sensing module (the set up) consists of a LED with the wavelength of 370–380nm and a color complementary metal oxide semiconductor (CMOS) micro-camera inbuilt at upright position of a black box to obtain an image of...
The discovery of in-vitro systematic evolution of ligands by exponential enrichment (SELEX) process has considerably broaden the utility of aptamer as bio-recognition element, providing the high binding affinity and specificity against the target analytes. Recent research has focused on the development of structure switching signaling aptamer assay, transducing the aptamer- target recognition event...
This work demonstrates the development of a folding based electrochemical aptasensor using methylene blue (MB) tagged anti-Ochratoxin A (OTA) aptamers. Different aptamer coupling strategies were tested using Hexamethylenediamine, polyethylene glycol, simple adsorption and diazonium coupling mechanism. The best sensitivity was recorded by oxidation of amines using hexamethylenediamine (HDMA) on screen...
A sensitive and selective colorimetric method based on the incorporation of zinc oxide nanoparticles (ZnO NPs) on the surface of carbon nanotubes (CNTs) was shown to posses synergistic peroxidase like activity for the detection of cholesterol. The proposed nanocomposite catalyzed the oxidation of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) in the presence of hydrogen peroxide (H2O2...
We report a new label-free colorimetric aptasensor based on DNAzyme–aptamer conjugate for rapid and high-throughput detection of Ochratoxin A (OTA, a possible human carcinogen, group 2B) in wine. Two oligonucleotides were designed for this detection. One is N1 for biorecognition, which includes two adjacent sequences: the OTA-specific aptamer sequence and the horseradish peroxidase (HRP)-mimicking...
Diarrheic Shellfish Poisoning (DSP) is a gastrointestinal illness caused by consumption of shellfish contaminated with DSP toxins such as okadaic acid (OA) and dinophysistoxins (DTX). The occurrences of OA in bivalves induce not only public health problems but also economic damages to shellfish farming. Consequently, the development of fast, reliable and sensitive detection methods is an evident necessity...
The aptamer immbolization onto organized mixed layers of diazonium salts via click chemistry was explored. The immobilized aptamer was employed in the fabrication of a highly sensitive and reusable electrochemical impedimetric aptasensor for the detection of ochratoxin A (OTA). The screen-printed carbon electrodes (SPCEs) were first modified by electrografting of a protected 4-((trimethylsilyl)ethynyl)...
An electrochemical immunosensor for okadaic acid (OA) detection has been developed, and used in an indirect competitive immunoassay format under automated flow conditions. The biosensor was fabricated by injecting OA modified magnetic beads onto screen printed carbon electrode (SPCE) in the flow system. The OA present in the sample competed with the immobilized OA to bind with anti-okadaic acid monoclonal...
A colorimetric protein phosphatase (PP) inhibition test for the detection of microcystin-LR (MC-LR) has been developed. Three PP2As, one recombinant and two natural versions, as well as one PP1 produced by molecular engineering, were tested. First, assays were performed using the enzymes in solution to compare their sensitivity to MC-LR. The PP2A purchased from ZEU Immunotec and PP1 appeared more...
In this work, an electrochemical method based on the diazonium-coupling reaction mechanism for the immobilization of okadaic acid (OA) on screen printed carbon electrode was developed. At first, 4-carboxyphenyl film was grafted by electrochemical reduction of 4-carboxyphenyl diazonium salt, followed by terminal carboxylic group activation by N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyle)-N′-ethyle-carbodiimide...
This work describes the use of a PEDOT:PSS-based conductive polymer for designing AChE-based biosensors. The transducers were obtained directly by screen-printing a PEDOT:PSS suspension on the surface of thick film carbon electrodes. The obtained working electrodes showed a high conductivity when compared with electrodes modified with conventional mediators like cobalt phthalocyanine or tetracyanoquinodimethane...
An amperometric biosensor based on laccase, from Trametes versicolor (LTV), was developed and optimized for monitoring the phenolic compounds content in tea infusions. The fungal enzyme was immobilized by entrapment within polyvinyl alcohol photopolymer PVA-AWP (azide-unit pendant water-soluble photopolymer) onto disposable graphite screen-printed electrodes (SPE). Sensitivity optimization in terms...
The Sonogel electrode was immersed in hemin solution to obtain the hemin–Sonogel-modified electrode by cyclic voltammetry (CV). It was applied to detect superoxide radicals produced by xanthine oxidase catalyzed hypoxanthine oxidation. The characterization of hemin–Sonogel was modified by impedance and CV.
This paper describes the characterization of the gold-catalyzed deposition of silver on graphite screen-printed electrodes (SPEs) using electrochemical impedance spectroscopy (EIS) and the application of this approach to the development of impedimetric immunosensors. After applying −0.1V for 45s, the amount of electrodeposited silver quantitatively changes the magnitude of two elements of the electrical...
Amperometric acetylcholinesterase (AChE) biosensors have been developed to resolve mixtures of chlorpyrifos oxon (CPO) and chlorfenvinfos (CFV) pesticides. Three different biosensors were built using the wild type from electric eel (EE), the genetically modified Drosophila melanogaster AChE B394 and B394 co-immobilized with a phosphotriesterase (PTE). Artificial Neural Networks (ANNs) were used to...
This paper describes the characterization and optimization of an amperometric cytochrome c (cyt c)-based sensor for the determination of the antioxidant capacity of pure substances and natural samples. The cyt c and the xanthine oxidase (XOD) enzyme were co-immobilized on the electrode using the combination of several long-chain thiols. The self-assembled monolayer (SAM) was optimized in terms of...
This work shows the possibility of combining the high sensitivity of genetically-modified Drosophila melanogaster acetylcholinesterase (B394) with the ability of phosphotriesterase (PTE) to hydrolyse organophosphate compounds, in the aim of developing a biosensor selective to two insecticides of interest: chlorpyrifos and chlorfenvinfos. The studies clearly demonstrate that chlorfenvinfos is a substrate...
The determination of the optimum parameters for hydroxyl radicals (OH) formation by a TiO 2 solution has been investigated by measuring the emitted fluorescence after the reaction with terephthalic acid has occurred. After UV irradiation, the terephthalic acid was transformed into 2-hydroxyterephthalic acid whose fluorescence is directly proportional to the generated OH. Optimization of hydroxyl...
Two new amperometric biosensors based on immobilization of acetylcholinesterase on a sonogel-carbon electrode for detection of organophosphorous compounds are proposed. The electrodes were prepared applying high-energy ultrasounds directly to the precursors. The first biosensor was obtained by simple entrapping acetylcholinesterase in Al 2 O 3 sol–gel matrix on the sonogel-carbon....
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