Glassy Carbon Electrode Modified with Silver Nanodendrites Implemented in Polylactide-Thiacalix[4]arene Copolymer for the Electrochemical Determination of Tryptophan

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Glassy carbon electrode (GCE) was modified by new polymeric materials obtained from oligolactides by cross-linking with tetracarboxylated thiacalix[4]arene in cone, partial cone and 1,3-alternate configurations and then silver was deposited by potential cycling in the pores of the polymer film. The modified electrode showed highly sensitive and selective signal toward tryptophan which was irreversibly oxidized on the coating due to Ag + assisted accumulation in the surface layer. The role of macrocycle configuration and conditions for Ag nanodendrites formation are described. Granulation of the polymer films caused by the macrocycles improves both the conditions for silver deposition and tryptophan determination. The electrochemical sensor developed makes it possible to determine from 0.1 to 100μM of tryptophan with the limit of detection down to 0.03μM. No interference with oxidation of other amino acids (phenylalanine, histidine, cysteine and tyrosine) was found. The electrochemical sensor developed was validated in the determination of tryptophan sedative medication "Formula of calmness" in the presence of vitamins B 5 and B 6

Organic Acid and DNA Sensing with Electrochemical Sensor Based on Carbon Black and Pillar[5]arene

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimElectrochemical sensor has been proposed on the base of glassy carbon electrode (GCE) modified with carbon black (CB) and pillar[5]arene (P[5]A). The characteristics of the peak currents were found to be sensitive to the incubation of the sensor in organic acid and DNA solution. The detection of n×(10−8–10−5) M of organic acid and down to (1–5)×10−18 g of DNA was attributed to the effect of the analytes on the aggregation and relative stability of oxidized and reduced forms of P[5]A. No signal interference with the alkali and alkali-earth metal ions was found. The electrochemical sensor was tested in the detection of specific DNA interactions, i.e. reactive oxygen species damage and intercalating pharmaceuticals detection

Electrochemical dna sensor based on poly(Azure a) obtained from the buffer saturated with chloroform

Electropolymerized redox polymers offer broad opportunities in detection of biospecific interactions of DNA. In this work, Azure A was electrochemically polymerized by multiple cycling of the potential in phosphate buffer saturated with chloroform and applied for discrimination of the DNA damage. The influence of organic solvent on electrochemical properties of the coating was quantified and conditions for implementation of DNA in the growing polymer film were assessed using cyclic voltammetry, quartz crystal microbalance, and electrochemical impedance spectros-copy. As shown, both chloroform and DNA affected the morphology of the polymer surface and electropolymerization efficiency. The electrochemical DNA sensor developed made it possible to distinguish native and thermally and chemically damaged DNA by changes in the charge transfer resistance and capacitance. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This research was funded by Russian Science Foundation, grant number 17‐73‐20024

Electrochemical Determination of Malathion on an Acetylcholinesterase-Modified Glassy Carbon Electrode

© 2017 Taylor & Francis. An acetylcholinesterase biosensor based on glassy carbon electrode modified with carbon black and pillar[5]arene was used for the determination of malathion after its preliminary oxidation. The contributions of enzyme immobilization and oxidation conditions to the improvement of analytical characteristics of the biosensor were considered and quantified. In optimal conditions, the acetylcholinesterase biosensor allows the determination of 40 pM of malathion with 10 min of incubation and 15 pM with 30 min of incubation. The sensitivity of immobilized enzyme was found to be higher than that the free enzyme due to sorbtional accumulation in the modifier layer. Incomplete oxidation of malathion decreased the sensitivity of the assay. The developed acetylcholinesterase biosensor was validated for the determination of malathion residues in grapes, wine, and peanuts. The recoveries calculated against a high-performance liquid chromatography assay were between 80 and 120% due to possible matrix effects and the simplified extraction protocols

Label-free electrochemical aptasensor for cytochrome c detection using pillar[5]arene bearing neutral red

© 2015 Elsevier B.V. All rights reserved. Novel electrochemical aptasensor toward cytochrome c (Cyt c) has been developed on the base of glassy carbon electrode (GCE) modified with electropolymerized neutral red (Poly-NR) and decacarboxylated pillar[5]arene (P[5]A-COOH) bearing terminal neutral red (NR) and aminated aptamer specific to Cyt c. Addition of Cyt c resulted in decrease of the cathodic peak current of NR on cyclic voltammogram due to suppression of the electron exchange between reduced and oxidized NR forms in the surface layer. The implementation of Cyt c in the surface layer was confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). Depending on the content of the surface layer and assembling protocol, the limits of detection (LODs) varied from 0.02 to 1.0 nM and linear range of concentrations was within three orders of magnitude. Interfering influence of some proteins and polyethylene glycol was characterized. The aptasensors developed can find application in detection of Cyt c as apoptosis agent in blood serum. This has been partially validated in model blood serum mimicking the ionic composition of the plasma

Impedimetric Detection of DNA Damage with the Sensor Based on Silver Nanoparticles and Neutral Red

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Novel electrochemical DNA-sensor based on glassy carbon electrode (GCE) modified with Ag nanoparticles, Neutral red covalently attached to its surface and native DNA adsorbed on modifier coating was developed for the estimation of DNA damage on example of model system based on Fenton reagent. As was shown, the oxidation process resulted in synchronous increase of electron transfer resistance and capacitance measured by electrochemical impedance spectroscopy (EIS). The contribution of each sensor component on the signal was specified and sensitivity estimated against similar surface coatings. The shift of EIS parameters was found to be higher than that of similar biosensors reported. The DNA sensor was tested on the estimation of antioxidant capacity of green tea infusions again the results of coulometric titration with electrogenerated bromine

Electrochemical behavior of pillar[5]arene on glassy carbon electrode and its interaction with Cu2+ and Ag+ ions

© 2014 Elsevier Ltd. All rights reserved. The electrochemical behavior of pillar[5]arene (P[5]A) and of its reaction products with Ag+ and Cu2+ ions has been investigated using cyclic voltammetry, optical methods and transmission electron microscopy (TEM). Stepwise oxidation of hydroquinone units of P[5]A molecule is guided by self-assembling and acid-base interactions. From one to three hydroquinone units per P[5]A molecule are oxidized depending on the measurement conditions. The deposition of P[5]A on glassy carbon electrode (GCE) partially blocks the electron transduction. Interfering influence of dissolved oxygen can be partially eliminated by the use of carbon black as immobilization matrix. The reaction of P[5]A with silver ions results in formation of most stable form with three benzoquinone and two hydroquinone units stabilized by quinhydrone-like structure. The Ag nanoparticles formed in the reaction retain electron transduction with the electrode due to involvement of shielding P[5]A molecules. Similar reaction with Cu2+ ions does not lead to stable products because of the formation of Cu2O particles detected by UV spectroscopy and TEM. Possible analytical applications of the materials obtained were proved by electrocatalytic reduction of hydrogen peroxide and mediated oxidation of thiocholine as model systems. In both cases, high sensitivity and wide range of the concentration determined were shown

Impedimetric determination of kanamycin in milk with aptasensor based on carbon black‐oligolactide composite

The determination of antibiotics in food is important due to their negative effect on human health related to antimicrobial resistance problem, renal toxicity, and allergic effects. We propose an impedimetric aptasensor for the determination of kanamycin A (KANA), which was assembled on the glassy carbon electrode by the deposition of carbon black in a chitosan matrix followed by carbodiimide binding of aminated aptamer mixed with oligolactide derivative of thiacalix[4]arene in a cone configuration. The assembling was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. In the presence of the KANA, the charge transfer resistance of the inner interface surprisingly decreased with the analyte concentration within 0.7 and 50 nM (limit of detection 0.3 nM). This was attributed to the partial shielding of the negative charge of the aptamer and of its support, a highly porous 3D structure of the surface layer caused by a macrocyclic core of the carrier. The use of electrostatic assembling in the presence of cationic polyelectrolyte decreased tenfold the detectable concentration of KANA. The aptasensor was successfully tested in the determination of KANA in spiked milk and yogurt with recoveries within 95% and 115%. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 16‐13‐000051/0419/20Funding: I.S. acknowledges financial support from the Russian Science Foundation (grant no. 16‐13‐00005) in the synthesis and application in the biosensor platform of the oligolactides bearing thiacalix[4]arene fragments. T.H. acknowledges funding from the European Union’s Horizon 2020 Research and Innovation Program underthe Marie Sklodowska‐Curie grant agreement no. 690898 and from the Science Grant Agency VEGA, project No.1/0419/20

Electrochemical Sensing of Idarubicin—DNA Interaction Using Electropolymerized Azure B and Methylene Blue Mediation

A highly sensitive electrochemical DNA sensor for detection of the chemotherapeutic drug idarubicin mediated by Methylene blue (MB) has been developed. DNA from fish sperm has been immobilized at the electropolymerized layers of Azure B. The incorporation of MB into the DNA layers substantially increased the sensor sensitivity. The concentration range for idarubicin determination by cyclic voltammetry was from 1 fM to 0.1 nM, with a limit of detection (LOD) of 0.3 fM. Electrochemical impedance spectroscopy (EIS) in the presence of a redox probe ([Fe(CN)6 ]3−/4− ) allowed for the widening of a linear range of idarubicin detection from 1 fM to 100 nM, retaining LOD 0.3 fM. The DNA sensor has been tested in various real and artificial biological fluids with good recovery ranging between 90–110%. The sensor has been successfully used for impedimetric idarubicin detection in medical preparation Zavedos® . The developed DNA biosensor could be useful for the control of the level of idarubicin during cancer therapy as well as for pharmacokinetics studies. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: A.P. announces the financial support of Russian Science Foundation (grant 17-73-20024). T.H. is grateful to Science Agency VEGA, project No. 1/0419/20, for financial support

Impedimetric aptasensor for ochratoxin a determination based on Au nanoparticles stabilized with hyper-branched polymer

An impedimetric aptasensor for ochratoxin A (OTA) detection has been developed on the base of a gold electrode covered with a new modifier consisting of electropolymerized Neutral Red and a mixture of Au nanoparticles suspended in the dendrimeric polymer Botlorn H30®. Thiolated aptamer specific to OTA was covalently attached to Au nanoparticles via Au-S bonding. The interaction of the aptamer with OTA induced the conformational switch of the aptamer from linear to guanine quadruplex form followed by consolidation of the surface layer and an increase of the charge transfer resistance. The aptasensor makes it possible to detect from 0.1 to 100 nM of OTA (limit of detection: 0.02 nM) in the presence of at least 50 fold excess of ochratoxin B. The applicability of the aptasensor for real sample assay was confirmed by testing spiked beer samples. The recovery of 2 nM OTA was found to be 70% for light beer and 78% for dark beer. © 2013 by the authors; licensee MDPI, Basel, Switzerland