Biosensors for Antioxidant Evaluation in Biological Systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The prevention of oxidative reactions in a biological medium as well as the role of reactive oxygen species (ROS) in chronic degenerative diseases are questions that continue to be investigated. Electrochemical biosensors have shown attractive features to evaluate the oxidative stress condition at a level comparable to chromatographic and spectroscopic techniques. The biosensors developed so far are based on direct analysis of specific indicators such as biomarkers of oxidative stress on the monitoring of reactive oxygen species the free radicals in cells or tissues, aiming to obtain a correlation between the index obtained from these indicators with the oxidative stress levels in cells. In this review we will provide an overview of the development of electrochemical biosensors to evaluate the content of antioxidants and reactive oxygen species in physiological systems. Some discussion regarding the analysis of antioxidant capacity at the single cell level is also presented.162109120Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPEAL/PRONEXCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Electrochemical investigations of the reaction mechanism and kinetics between NADH and redox-active (NC)(2)C6H3-NHOH/(NC)(2)C6H3-NO from 4-nitrophthalonitrile-(NC)(2)C6H3-NO2-modified electrode

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)A simple and sensitive method for the electrocatalytic detection of NADH on a carbon paste electrode modified with a redox-active (NC)(2)C6H3-NO/(NC)(2)C6H3-NHOH (NOPH/NHOHPH) electrogenerated in situ from 4-nitrophthalonitrile (4-NPHN) is presented. The electrode modified with 4-NPHN showed an efficient electrocatalytic activity towards the oxidation of NADH with activation overpotential of 0.12 V vs. Ag/AgCl. The formation of all intermediate charge transfer complex is proposed for the charge transfer reaction between NADH and the 4-NPHN-resulting system. The second-order rate constant for electrocatalytic oxidation of NADH, kappa(obs), and the apparent Michaelis-Menten constant K-M, at pH 7.0 were evaluated with rotating disk electrode (RDE) experiments, giving 1.0 x 10(4) mol(-1) Ls(-1) and 2.7 x 10(-5) mol L-1, respectively. Employing the Koutecky-Levich approach indicated that the NADH oxidation reaction involves two electrons. The sensor provided a linear response range for NADH from 0.8 up to 8.5 mu mol L-1 with sensitivity, detection, quantification limits and time response of 0.50 mu A L mu mol(-1), 0.25 mu mol L-1, 0.82 mu mol L-1 and 0.1 s. respectively. The repeatability of the measurements with the same sensor and different sensors. evaluated in terms of relative standard deviation, were 4.1 and 5.0%, respectively, for n = 10. (C) 2008 Elsevier B.V. All rights reserved.243448454Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPEALConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)PADCTBNBRENORBIOGerman Academic Exchange Service (DAAD)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Poly-xanthurenic acid modified electrodes: An amperometric sensor for the simultaneous determination of ascorbic and uric acids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The poly-xanthurenic acid (poly-Xa)/multi-walled carbon nanotube (MWCNT)/glassy carbon modified electrode (poly-Xa/MWCNT/GCE) was successfully applied for the simultaneous determination of ascorbic (AA) and uric (UA) acids. Cyclic voltammetric results show that the modified electrode displays an excellent eletrocatalytic activity toward the oxidation of AA at a low potential (0.05 V versus Ag/AgCl) and anodic peak resolution (Delta E-pa), close to 300 mV versus Ag/AgCl, in solutions containing AA and UA. Values in the order of 10(6) L mol(-1) s(-1) were obtained for the kinetic constant k(cat) for the catalytic oxidation of AA, upon evaluation by cyclic voltammetry, chronoamperometry and RDE. Furthermore, the sensor provided limits of detection of 0.19 mu mol L-1 and 0.31 mu mol L-1 for AA and UA, respectively. The sensor was applied for the simultaneous determination of AA and UA in urine samples and the average recoveries for these samples were 99.9 (+/-2.5)% and 99.9 (+/-2.6)%, respectively. (C) 2012 Elsevier B.V. All rights reserved.168289296FAPEALFAPEAL/PRONEXCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROCAD/NFINCT-BionaliticaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

A very low potential electrochemical detection of L-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)A nanohybrid platform built with multi-walled carbon nanotubes and gold nanorods, prepared via a cationic surfactant-containing seed-mediated sequential growth process, in aqueous solution, on a glassy carbon substrate has been successfully developed to be used in the electrocatalytic oxidation of L-cysteine (Cys). The nanohybrid was characterized by transmission electron microscopy, Raman spectroscopy and electrochemical measurements. Cyclic voltammetry results had shown that the modified electrode allows the oxidation of Cys at a very low anodic potential (0.00 V vs. Ag/AgCl). The kinetic constant k(cat) for the catalytic oxidation of Cys was evaluated by chronoamperometry and provided a value of 5.6 x 10(4) L mol(-1) s(-1). The sensor presents a linear response range from 5.0 up to 200.0 mu mol L-1, detection limit of 8.25 nmol L-1 and a sensitivity of 120 nA L mu mol(-1). (C) 2013 Elsevier B.V. All rights reserved.50202209PRONEX/FAPEALCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROCAD/NFINCT-BionaliticaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Modified Carbon Paste Electrode for Kinetic Investigation and Simultaneous Determination of Ascorbic and Uric Acids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present work explores, for the first time, the electrocatalytic oxidation of ascorbic acid (AscH(2)) and its determination in the presence Of Uric acid (UA) on the in situ activated 4-nitrophthalonitrile modified carbon paste electrode. The kinetic constant kappa for the catalytic reaction for the electrocatalytic oxidation of ascorbic acid, evaluated by cyclic voltammetry, chronoamperometry and RDE voltammetry provided values around 10(6) L mol(-1) s(-1). The sensor provided a linear response range for AscH(2) and UA from 5.0 up to 120.0 mu mol L(-1) with detection limits of 1.6 mu mol L(-1) and 1.3 mu mol L(-1), respectively. The sensor was applied for the Simultaneous determination of AscH(2) and UA in urine samples and the average recoveries for these samples were 99.8 (+/- 3.1)% and 99.9 (+/- 2.1)%, respectively.212123112320INCT de BioanaliticaFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPEALCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PADCTPROCAD/NF. PRLPRBMGerman Academic Exchange Service (DAAD)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

An amperometric sensor based on hemin adsorbed on silica gel modified with titanium oxide for electrocatalytic reduction and quantification of artemisinin

The present work describes the development of an amperometric sensor based on hemin immobilized oil a titanium oxide modified silica toward detection of artemisinin (ARN) in neutral medium at art applied potential of -0.5 V vs. Ag/AgCl. The sensor presented its best performance in 0.1 mol L(-1) phosphate buffer Solution, at pH 7.0. After optimizing the operational conditions, the sensor provided a linear response range for ARN reduction from 50 nmol L(-1) to 1000 nmol L(-1) with a sensitivity, detection and quantification limits of 24.66 A L mol(-1), 15 nmol L(-1) and 52 nmol L(-1), respectively. The proposed sensor showed a stable response for at least 80 successive determinations. The repeatability of the measurements with the sensor and the preparation of a series of electrodes, evaluated in terms of relative standard deviation, were 4.1% and 5.0%, respectively, for n = 10. The developed sensor was applied for the determination of ARN in the crude extracts of A. vulgaris 1, and the average recovery for these samples is 101.4 (+/- 3.1)%. (C) 2008 Elsevier B.V. All rights reserved.77290991

Alternating Layers of Iron(III) Tetra(N-methyl-4-pyridyl)-porphyrin and Copper Tetrasulfonated Phthalocyanine for Amperometric Detection of 4-Nitrophenol in Nanomolar Levels

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present work describes the development of a highly sensitive amperometric sensor for 4-NP in nanomolar levels using a glassy carbon electrode modified with alternating layers of CuTSPc and FeT4MPyP. After optimizing the operational conditions, the sensor provided a linear response range for 4-NP from 5 up to 100 nmol L-1 with sensitivity, detection, and quantification limits of 14 nA L nmol(-1), 1.9 nmol L-1, and 5.4 nmol L-1, respectively. The proposed sensor showed a stable response for at least 200 successive determinations. This modified electrode can be used to the determination of 4-NP in water samples.202123332339Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPEALCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PADCTPRLWJRSFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq