Dual-Target Additively Manufactured Electrochemical Sensor for the Multiplexed Detection of Protein A29 and DNA of Human Monkeypox Virus

Herein, we present the first 3D-printed electrochemical portable biodevice for the detection of monkeypox virus (MKPV). The electrochemical device consists of two biosensors: an immunosensor and a genosensor specifically designed for the detection of the protein A29 and a target DNA of MKPV, respectively. The electrodes were manufactured using lab-made ultraflexible conductive filaments composed of carbon black, recycled PLA from coffee pods, and castor oil as a plasticizer. The sensors created through 3D printing technology exhibited good reproducibility and repeatability of analytical responses. Furthermore, both the immunosensor and genosensor demonstrated excellent MKPV detection capabilities, with a linear range from 0.01 to 1.0 μmol L–1 for the antigen and 0.1 to 20.0 μmol L–1 for the DNA target. The biosensors achieved limits of detection of 2.7 and 29 nmol L–1 for the immunosensor and genosensor, respectively. Interference tests conducted with the biosensors demonstrated their selectivity for MKPV. Moreover, analyses of fortified human serum samples showed recoveries close to 100%, confirming the absence of significant matrix effects for MKPV analysis. Therefore, the 3D-printed multiplex device represents a viable and highly promising alternative for on-site, portable, and rapid point-of-care MKPV monitoring

Anodic stripping voltammetric determination of aurothiomalate in urine using a screen-printed carbon electrode

This work describes an electroanalytical method for determining gold(I) thiomalate, aurothiomalate, widely used for treatment of reumatoid arthiritis, using a screen-printed carbon electrode (SPCE). Aurothiomalate (AuTM) was determined indirectly at the same electrode by accumulating it first at -1.5 V vs. printed carbon. At this potential in the adsorbed state, the AuTM is reduced to Au(0), which is then oxidized at two steps at -0.22 V and +0.54 V on SPCE. Using optimized conditions of 60 s deposition time, -1.5 V (vs. printed carbon) accumulation potential, 100 mV s(-1) scan rate, linear calibration graphs can be obtained by monitoring the peak at +0.54 V for AuTM in HCl 0.1 mol L-1 from 1.43 x 10(-6) to 1.55 x 10(-4) mol L-1. A limit of detection obtained was 6.50 x 10(-7) mol L-1, and the relative standard deviation from five measurements of 3.0 x 10(-5) mol L-1 AuTM is 4.5%. The method was successfully applied for AuTM determination in human urine sample

Application of the Potentiometric Stripping Analysis with Constant Current for the Determination of Lithium Ions Using a Spinel-Type Manganese (IV) Oxide-Modified Carbon Paste Electrode

A potentiometric stripping method for the measurement of lithium ions at a carbon paste electrode modified with spinel-type manganese oxide is described. The procedure is based on the effective pre-concentration of lithium ions on an electrode surface containing spinel-type MnO(2), with the reduction of Mn(IV) to Mn(III), and the consequent intercalation (insertion) of the lithium ions into the spinel structure. The best current constant stripping analysis (CCSA) response was reached for an electrode composition of 25% (m/m) spinel-type MnO(2) in the paste, 0.1 mol L(-1) TRIS buffer solution at pH 8.0, an accumulation potential of 0.3 V vs. the saturated calomel reference electrode (SCE), a pre-concentration time of 90 s and the application of a small positive constant current (10 A) during the stripping step. The obtained limit of detection was 2.0 x 10(-7) mol L(-1), and the relative standard deviation from five measurements of 2.5 x 10(-6) mol L(-1) lithium ions was 3.8%.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Screen-Printed Carbon Electrode Modified with Poly-L-histidine Applied to Gold(III) Determination

O presente trabalho reporta o desenvolvimento de um novo método voltamétrico para análise de íons ouro(III) usando eletrodo de carbono impresso modificado com poli-L-histidina. O procedimento é baseado no acúmulo do complexo [AuCl4]-, na superfície do eletrodo sob potencial de circuito aberto e tempo de acúmulo controlado. Parâmetros que influenciam na resposta, tais como: preparação do filme, pH, potencial de acúmulo e tempo de acúmulo, foram otimizados e curvas analíticas para os íons ouro foram construídas usando voltametria de varredura linear (LSV), pulso diferencial (DPV), e onda quadrada (SWV). Limites de detecção de 6,0 × 10-6 mol L-1, 1,7 × 10-6 mol L-1 e 4,0 × 10-6 mol L-1 foram obtidos para LSV, DPV e SWV, respectivamente. O método foi aplicado para a determinação de íons ouro em amostras de urina humana.A sensitive voltammetric method for trace measurements of gold(III) ions using a screen-printed carbon electrode modified with poly-L-histidine is described. The new procedure is based on the accumulation of the tetrachloroaurates complex at the electrode surface under an open circuit potential condition, followed by a cathodic stripping scan of potential. Parameters such as film preparation, pH, accumulation potential and deposition time have been optimized to obtain the best voltammetric response. Using optimal experimental conditions, analytical curves for gold ions were obtained using a linear sweep (LSV), differential pulse (DPV), and square wave voltammetry (SWV). Limits of detection of 6.0 x 10(-6) mol L(-1), 1.7 x 10(-6) mol L(-1) and 4.0 x 10(-6) mol L(-1) were estimated for the LSV, DPV and SWV, respectively. The method was successfully applied to the determination of gold ions in human urine samples.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

Voltammetric sensor for amoxicillin determination in human urine using polyglutamic acid/glutaraldehyde film

A voltammetric sensor for determination of amoxicillin (AMX) was developed based on a glutaraldehyde cross-linked polyglutamic acid modified glassy carbon electrode. The proposed method is based on pre-concentration of AMX by cathodic accumulation as its oxidative product before being determined indirectly at potential as low as +0.23 V by square wave voltammetry. Linear response range, sensitivity and limit of detection were 2.0-25.0, 1.06 and 0.9.2 mu mol L-1, respectively, for AMX in 0.1 mol L-1 acetate buffer pH 5.2, pre-accurnulation time of 60s and accumulation potential of +1.0V. It was demonstrated that the glassy carbon electrode modified with PGA/GLU could be used for AMX determination in human urine without any separation step. (C) 2008 Elsevier B.V. All rights reserved.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

Determination of isoniazid in human urine using screen-printed carbon electrode modified with poly-L-histidine

A sensitive voltammetric method for trace measurements of isoniazid (INZ) in synthetic human urine sample is described. The method is based on its electroreduction at -0.98 V vs. Ag/AgCl on screen-printed carbon electrode (SPCE) modified with poly-L-histidine (PH). A film of good adherence on SPCE and electrocatalytic properties was obtained coating the electrode by histidine monomer electropolymerization process (SPCE/EPH). The electrochemical behavior of the modified SPCE was investigated by cyclic, linear sweep (LSV), differential pulse (DPV). square-wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). Limits of detection of 5.0 x 10(-7) mol L(-1), 1.7 x 10(-7) mol L(-1) and 2.5 x 10(-7) mol L(-1) were estimated from LSV, DPV and SWV determinations, respectively. The method was successfully applied to the determination of INZ in human urine samples. (c) 2009 Elsevier B.V. All rights reserved.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

Platinum Nanoparticles Supported by Carbon Nanotubes: Improvement in electrochemical sensor performance for caffeine determination

Abstract Platinum nanoparticles supported by carbon nanotubes were obtained by a simple chemical route and used for preparation of electrochemical sensor towards caffeine determination. Carbon nanotubes were used before and after an acid treatment, yielding two different materials. Morphological and structural characterization of these materials showed platinum nanoparticles (size around 12 nm) distributed randomly along carbon nanotubes. Modified electrodes were directly prepared through a dispersion of these materials. Voltammetric studies in the presence of caffeine revealed an electrocatalytic effect of platinum oxides, electrochemically produced from the chemical oxidation of the platinum nanoparticles. This behavior was explored in the development a selective method for caffeine determination based on platinum oxide reduction at a lower potential value (+0.45 V vs. Ag/AgCl). Using the best set of experimental conditions, it was shown a linear relationship for the caffeine concentration ranging from 5.0 to 25 µmol L-1 with a sensitivity of 449 nA L µmol-1. Limits of detection and quantification of 0.54 and 1.80 µmol L-1 were calculated, respectively. Recovery values for real samples of caffeine pharmaceutical formulations between 98.6% and 101.0% (n = 3) were obtained using the proposed procedure. Statistical calculations showed good concordance (95% confidence level) between the added and recovery values

Anodic Stripping Voltammetric Determination of Lead (II) and Cadmium (II) by Using a Carbon Nanotubes Paste Electrode Modified with Ion Exchange Synthetic Resin

This work describes an electroanalytical method for simultaneous determination of cadmium (II) and lead (II) ions using a carbon paste modified with carbon nanotubes and an ion exchange synthetic resin (Amberlite IR120) electrode under Differential Pulse Anodic stripping voltammetric (DPASV) conditions. The procedure is based on the effective preconcentration of metal ions on the electrode surface containing ion exchange resin under open circuit condition. Using optimized conditions of 600 s preconcentration time for an electrode composition of 5% w/w Amberlite IR 120 and 30 % w/w carbon nanotubes in the paste, a scan rate of 10 mVs(-1), and a potential pulse amplitude of 75 mV, linear calibration graphs can be obtained by were monitoring the peaks at -0.75 V for cadmium (II) and -0.58 V for lead (II) from 0.07 - 2.50 mu mol L-1 and 0.01 - 5.80 mu mol L-1, respectively. The proposed method was applied for the determination of lead (II) and cadmium (II) in ethanol fuel, gasoline for aviation, and spiked water. For all samples analyzed, recoveries ranged from 95.8 to 106.3%. Interferences were also evaluated.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Flow injection amperometric determination of procaine in pharmaceutical formulation using a screen-printed carbon electrode

A rapid and simple method for procaine determination was developed by flow injection analysis (FIA) using a screen-printed carbon electrode (SPCE) as amperometric detector. The present method is based on the amine/hydroxylamine oxidation from procaine monitored at 0.80 V on SPCE in sodium acetate solution pH 6.0. Using the best experimental conditions assigned as: pH 6.0, flow rate of 3.8 mL min(-1), sample volume of 100 mu L and analytical path of 30 cm it is possible to construct a linear calibration curve from 9.0 x 10(-6) to 1.0 x 10(-4) mol L-1. The relative standard deviation for 5.0 x 10(-5) mol L-1 procaine (15 repetitions using the same electrode) is 3.2% and detection limit calculated is 6.0 x 10(-6) mol L-1. Recoveries obtained for procaine gave a mean values from 94.8 to 102.3% and an analytical frequency of 36 injections per hour was achieved. The method was successfully applied for the determination of procaine in pharmaceutical formulation without any pre-treatment, which are in good accordance with the declared values of manufacturer and an official method based on spectrophotometric analysis. (c) 2006 Elsevier B.V. All rights reserved

Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. This paper describes the amperometric determination of lithium ions using carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions. Systematic investigations were made to optimize the experimental parameters for lithium sensor by flow injection analysis. The detection was based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and consequently the lithium ions extraction into the spinel structure. An operating potential of 0.50 V (vs. Ag/AgCl/3 KCl mol/L) was exploited for amperometric monitoring. The amperometric signal was linearly dependent on the lithium ions concentration over the range 4.0 x 10(-5) to 1.0 x 10(-3) mol L-1. The equilibrium constant of insertion/extraction of the lithium ion in the spine! structure, apparent Gibbs energy of insertion, and surface coverage of the electrode with manganese oxide, were calculated by peak charge (Q) in different concentration under flow conditions. Considering selectivity, the peak charge of the sensor was found to be linearly dependent on the ionic radius of the alkaline and earth-alkaline cations. (C) 2010 Elsevier Ltd. All rights reserved