Selective Label-Free Electrochemical Aptasensor Based on Carbon Nanotubes for Carbendazim Detection

One of the most widely used pesticides in Chile is carbendazim (CBZ), which in agriculture is used to protect crops from fungal diseases that commonly occur in rice, vegetable, and fruit crops. However, prolonged exposure to it, and its high persistence, can cause adverse health effects. Therefore, it is necessary to determine the presence of CBZ through rapid detection methods in food samples to prevent ingestion and exposure to this pesticide at risk concentrations. In this work, a label-free electrochemical aptasensor based on functionalized carbon nanotubes was prepared for CBZ detection. The carbodiimide reaction between the amino-terminated aptamer and the carboxylic groups of carbon nanotubes achieved the covalent immobilization of the aptamer. The immobilized aptamer changed its conformation when it detected CBZ and blocked access to the redox mediator on the electrode surface, resulting in a measurable decrease in the voltammetric response. Under the optimal conditions, the aptasensor featured a linear detection range between 1.0 and 50.0 nM, with a detection limit of 4.35 nM. Moreover, the aptasensor exhibited good selectivity for CBZ, among other pesticides, and good repeatability. For CBZ detection in tomatoes, the aptasensor accurately measured CBZ content in a sample prepared using the standard addition method. This work provides a simple, rapid, sensitive, and selective biosensor for CBZ detection and quantification in food samples

Selective Label-Free Electrochemical Aptasensor Based on Carbon Nanotubes for Carbendazim Detection

One of the most widely used pesticides in Chile is carbendazim (CBZ), which in agriculture is used to protect crops from fungal diseases that commonly occur in rice, vegetable, and fruit crops. However, prolonged exposure to it, and its high persistence, can cause adverse health effects. Therefore, it is necessary to determine the presence of CBZ through rapid detection methods in food samples to prevent ingestion and exposure to this pesticide at risk concentrations. In this work, a label-free electrochemical aptasensor based on functionalized carbon nanotubes was prepared for CBZ detection. The carbodiimide reaction between the amino-terminated aptamer and the carboxylic groups of carbon nanotubes achieved the covalent immobilization of the aptamer. The immobilized aptamer changed its conformation when it detected CBZ and blocked access to the redox mediator on the electrode surface, resulting in a measurable decrease in the voltammetric response. Under the optimal conditions, the aptasensor featured a linear detection range between 1.0 and 50.0 nM, with a detection limit of 4.35 nM. Moreover, the aptasensor exhibited good selectivity for CBZ, among other pesticides, and good repeatability. For CBZ detection in tomatoes, the aptasensor accurately measured CBZ content in a sample prepared using the standard addition method. This work provides a simple, rapid, sensitive, and selective biosensor for CBZ detection and quantification in food samples

Carbon-Based Electrochemical (Bio)sensors for the Detection of Carbendazim: A Review

Carbendazim, a fungicide widely used in agriculture, has been classified as a hazardous chemical by the World Health Organization due to its environmental persistence. It is prohibited in several countries; therefore, detecting it in food and environmental samples is highly necessary. A reliable, rapid, and low-cost method uses electrochemical sensors and biosensors, especially those modified with carbon-based materials with good analytical performance. In this review, we summarize the use of carbon-based electrochemical (bio)sensors for detecting carbendazim in environmental and food matrixes, with a particular interest in the role of carbon materials. Focus on publications between 2018 and 2023 that have been describing the use of carbon nanotubes, carbon nitride, graphene, and its derivatives, and carbon-based materials as modifiers, emphasizing the analytical performance obtained, such as linear range, detection limit, selectivity, and the matrix where the detection was applied

Electrochemical determination of food colorants in soft drinks using MWCNT-modified GCEs

© 2016 Elsevier B.V.Food colorants are chemicals added to foods and soft drinks during manufacturing or processing. However, some of these chemicals represent potential risks to human health, especially if they are consumed in excess. Here, we modified a glassy carbon electrode (GCE) with multi-walled carbon nanotubes (MWCNTs) using 1,3-dioxolane as a dispersant agent, resulting in a stable and reproducible electrochemical sensor. The resulting sensor was applied to study the food dyes tartrazine, sunset yellow and carmoisine, showing high sensitivity and reproducibility. The influences of the scan rate, pH, amount of MWCNTs and accumulation time were studied. Moreover, the developed method was successfully applied in the determination of colorants in commercial soft drinks and compared with a chromatographic method. The resulting concentrations were compared based on the maximum amount of soft drink that a child and an adult can consume before reaching the admissible daily intake (AD

In situ Electroreduction of Graphene Oxide: Increased Sensitivity for the Determination of NADH

A novel and useful method to catalyze the electro-oxidation of nicotinamide adenine dinucleotide (NADH) over a glassy carbon electrode (GCE) modified with graphene oxide (GO) is presented. Based on the presence of oxygen moieties in GO, which can be easily reduced, an in situ electrochemical generation of reduced graphene oxide (denoted as erGO) applying a sufficient negative potential. A potential of −1.000 V was selected to generate the erGO/GCE as a pretreatment potential before the detection of NADH. The in situ generated erGO/GCE system produces a decrease in the overpotential of NADH oxidation from +0.720 V to +0.230 V compared with GCE. The process also produced an important increase in current signals. The modified electrode was characterized by scanning electron (SEM) and electrochemical microscopies (SECM), cyclic voltammetry and by Raman spectroscopy. Amperometric detection of NADH via this straightforward electrocatalytic method provides a wide linear range between 10 and 100 μM, a lower detection limit of 0.36 μM and an excellent sensitivity of (1.47±0.09) μA mM −1

MWCNT-modified Electrode for Voltammetric Determination of Allura Red and Brilliant Blue FCF in Isotonic Sport Drinks

A fast and simple electrochemical sensor is presented for the determination of allura red and brilliant blue in isotonic sport drinks, using a glassy carbon electrode modified with multi-walled carbon nanotubes. The electrochemical behavior of the colorants was studied by cyclic and differential pulse voltammetry in 0.1 M PBS, pH 7.0. The solution pH, the amount of nanomaterial on the surface of the electrode and the accumulation time of each colorant were optimized. Under the optimal conditions, the sensor exhibited a linear response to allura red and brilliant blue with detection limits of 7 μg L −1 and 52 μg L −1 , respectively. The sensor was applied to the analysis of commercial isotonic sports drinks that contain individual or mixed colorants, showing good sensitivity and reproducibility. The results were compared with a chromatographic method showing that the levels of colorants are low and did not show a risk for a consumer's h

Electrochemical characterization and electrocatalytic application of gold nanoparticles synthesized with different stabilizing agents

Gold nanoparticles (AuNPs) have unique properties, making them attractive for electronic and energy-conversion devices and as (electro)catalysts for electrochemical sensors. In addition to the size and shape of AuNPs, the electrocatalytic properties of AuNP-sensors are also determined by the stabilizing agent used in their synthesis. Here, AuNPs were synthesized with citrate, alginate and quercetin, obtaining spherical and negatively charged nanoparticles. The AuNPs were used to modify glassy carbon electrodes (AuNPs/GCE), which were characterized by scanning electron microscopy and electrochemical techniques. The AuNPs/GCE showed aggregates of different sizes and degrees of dispersion on the electrode surface depending on the stabilizing agent. The AuNP's aggregates affect the homogeneity of the film, the reproducibility of the electrodes and their response in buffer solution. Finally, to evaluate the electrocatalytic ability of the AuNPs/GCE, we studied the oxidation of two analytes with opposite charges: (1) sunset yellow (negative) and (2) hydrazine (positive). Compared with GCE, the AuNPs/GCE showed good electrocatalytic properties for hydrazine, increasing the current up to 50% and shifting the potential by almost 400mV, depending on the AuNP used. For the negatively charged analyte, the current decreased up to 50% and no shift in potential was observed. Thus, the electrocatalytic properties of the AuNPs showed to be highly dependent on the nature of the analyte.FONDECYT 3140533 3150515 FONDAP 1513001

Catalytic aspects of metallophthalocyanines adsorbed on gold-electrode. Theoretical exploration of the binding nature role

The need of deeper insights regarding the inner working of catalysts represents a current challenge in the search of new ways to tune their activities towards new chemical transformations. Within this field, metallophthalocyanines-based (MPc) electrocatalysis has gained tremendous attention due to their versatility, low cost, great stability and excellent turn-over properties. In this concern, here we present a quantum chemical study of the formation of supramolecular complexes based on the adsorption of MPcs on gold substrates, and the effect of the substrate on their electrocatalytic properties. For this purpose, we used iron-(FePc), cobalt( CoPc) and copper-phthalocyanines (CuPc). To model the gold surface we used two gold clusters of different sizes, given by Au-26 and Au-58 accounting for gold electrode Au(111) surface. Thus, both electronic and binding strength features of the adsorption process between the complexes were analyzed in detail in order to gain a deeper description of the nature of the MPc-Au(111) formation, by using Density Functional Theory (DFT) calculations, at the PBE and TPSS levels including the dispersive contribution according to the Grimme approach (D3). Our results show that dispersion forces rule the MPc-gold interaction, with binding strengths ranging between 61 and 153 kcal mol(-1), in agreement to the reported experimental data. To provide a detailed picture of our findings we used the non-covalent interactions index (NCIs) analysis, which offers additional chemical insights regarding the forces that control their interaction strength. Finally, our calculations revealed that among the three MPcs, CuPc required less energy for its oxidation. However, the removal of the electron involves a tremendous decrease of the MPc-gold surface interaction strength thus suggesting its desorption, which would prevent the required reversibility of the redox reaction, explaining its low performance observed experimentally.Fondecyt 1140503 1150629 110758 1150327 3130383 3140533 Universidad Andres Bello project DI-1323-16/R RC120001 NC12008

Electrochemical method to study the environmental behavior of Glyphosate on volcanic soils: Proposal of adsorption-desorption and transport mechanisms

Glyphosate is used extensively worldwide, but current evidence suggests detrimental effects on the environment, pollinators, and human health. Glyphosate adsorption kinetics and adsorption/desorption were studied through batch sorption experiments in ten typical volcanic ash-derived soils from Andisol and Ultisol orders. Two kinetic models were used to fit the experimental data: i. Models that allowed establishment of principally kinetic parameters and modeling of the adsorption process, and ii. Models described solute transport mechanisms commonly used for remediation purposes. Adsorption kinetic data were best fitted by the pseudo-second-order kinetic model and Two-Site Nonequilibrium model. These models suggest that mechanisms are complex due to rapid surface adsorption in ultisols with mass transfer controlling adsorption kinetics across the boundary layer, as indicated by the high h and low t1/2 values. High intraparticle diffusion into macropores and micropores was observed for Andisols. The Freundlich model accurately represented adsorption equilibrium data in all cases (R2 > 0.9580) with comparatively higher adsorption capacity on Andisols. Kf values (2.50–52.28 μg1−1/n mL1/n g-1) and hysteresis were significant in all studied soils. Taken together, these data suggest that Glyphosate may be adsorbed more on Andisol soils in comparison to Ultisols

Electrochemical and associated techniques for the study of the inclusion complexes of thymol and β-cyclodextrin and its interaction with DNA

Thymol, a potent agent for microbial, fungal, and bacterial disease, has low aqueous solubility and it is genotoxic, i.e., is capable of damaging deoxyribonucleic acid (DNA). This possible problem of DNA toxicity needs to be solved to allow the use of different doses of thymol. This study characterized the inclusion compound containing thymol and beta-cyclodextrin (beta-CD) by measuring the interaction between these two components and the ability of thymol to bind DNA in its free and beta-CD complexed form. The encapsulation approach using beta-CD is particularly useful when controlled target release is desired, and a compound is insoluble, unstable, or genotoxic. The interaction between thymol and DNA has been studied using electrochemical quartz crystal microbalance (EQCM), atomic force microscopy (AFM), and differential pulse voltammetry (DPV). The characterization of the inclusion complex of thymol and beta-CD was analyzed by UV-vis spectrophotometry, cyclic voltammetry, and scanning electrochemical microscopy (SECM). Based on the free beta-CD by spectrophotometry method, the association constant of thymol with the beta-CD was estimated to be 2.8 x 10(4) L mol(-1). The AFM images revealed that in the presence of small concentrations of thymol, the dsDNA molecules appeared less knotted and bent on the mica surface, showing significant damage to DNA. The SECM and voltammetry results both demonstrated that the interaction of thymol-beta-CD complex was smaller than the free compound showing that the encapsulation process may be an advantage leading to a reduction of toxic effects and increase of the bioavailability of the drug.Brazilian agency CNPq Brazilian agency CAPES Brazilian agency FAPEAL Brazilian agency Organization of American States (OAS