Development and Application of a Highly Selective Biomimetic Sensor for Detection of Captopril, an Important Ally in Hypertension Control

A biomimetic sensor is proposed as a promising new analytical method for determination of captopril in different classes of samples. The sensor was prepared by modifying a carbon paste electrode with iron (II) phthalocyanine bis(pyridine) [FePe(dipy)] complex. Amperometric measurements in a batch analytical mode were first carried out in order to optimize the sensor response. An applied potential lower than 0.2 V vs Ag vertical bar AgCl in 0.1 mol L(-1) of TRIS buffer at pH 8.0 provided the best response, with a linear range of 2.5 x 10(-5) to 1.7 x 10(-4) mol L(-1). A detailed investigation of the selectivity of the sensor, employing seventeen other drugs, was also performed. Recovery studies were carried out using biological and environment samples in order to evaluate the sensor`s potential for use with these sample classes. Finally, the performance of the biomimetic sensor was optimized in a flow injection (FIA) system using a wall jet electrochemical cell. Under optimized flow conditions, a broad linear response range, from 5.0 x 10(-4) to 2.5 x 10(-2) mol L(-1), was obtained for captopril, with a sensitivity of 210 +/- 1 mu A L mol(-1).

Gestão à Vista: uma proposta de avaliação de impacto da política municipal de garantia de direitos infanto-juvenil. A relação de causa e efeito da prática da monitoria sobre o volume de doações ao fundo para a infância e adolescência - FIA

O presente projeto de dissertação apresenta uma metodologia para avaliar a relação de causa e efeito da forma de gestão adotada pelos Conselhos Municipais de Defesa dos Direitos da Criança e do Adolescente, em especial no que se refere à utilização de ferramentas de monitoria e avaliação para acompanhar os projetos executados, no aumento do orçamento público captado através de doações aos Fundos para a Infância e Adolescência – FIA. Este projeto busca identificar a existência de possíveis gargalos na gestão dos Conselhos, principalmente no que diz respeito aos processos de monitoria dos projetos desenvolvidos com recursos advindos de doações ao Fundo Municipal para a Infância e Adolescência como uma oportunidade de avançar no processo de melhoria da gestão pública, neste caso, de garantia de direitos infanto-juvenil. Para tanto, será necessário criar grupos de tratamento e controle considerando os Conselhos Municipais de Garantia de Direitos da Criança e do Adolescente que utilizam ferramentas de monitoria e avaliação daqueles que não adotam essa prática no seu cotidiano profissional. A identificação de tais Conselhos será feita a partir de três filtros correlacionados a saber, tamanho da população do município, índice de desenvolvimento humano municipal e cadastro em situação regular do Fundo Municipal para a Infância e a Adolescência. Não se trata de um trabalho que visa apontar erros na gestão dos Conselhos, ao contrário, uma proposta de mapeamento capaz de verificar fragilidades e propor uma linha de atuação alternativa - capaz de romper com práticas meramente paternalistas ou formalismos que produzam disfunções burocráticas - que gere transformação no espaço de atuação.

Immobilization of uricase in layer-by-layer films used in amperometric biosensors for uric acid

The layer-by-layer technique was exploited to immobilize the enzyme uricase onto indium tin oxide substrates coated with a layer of Prussian Blue. Uricase layers were alternated with either poly(ethylene imine) or poly(diallyidimethylammoniumchloride), and the resulting films were used as amperometric biosensors for uric acid. Biosensors with optimum perfomance had a limit of detection of 0.15 mu A mu mol 1(-1) cm(-2) with a linear response between 0.1 and 0.6 mu M of uric acid, which is sufficient for use in clinical tests. Bioactivity was preserved for weeks, and there was negligible influence from interferents, as detection was carried out at 0.0 V vs saturated calomel electrode.

An electrochemical sensor for (L)-dopa based on oxovanadium-salen thin film electrode applied flow injection system

An oxovanadium-salen complex (NAP-ethylene-bis(salicylidenciminato) oxovanadium) thin film deposited on a graphite-polyurethane electrode was investigated with regard to its potential use for detection of L-dopa in flow injection system. The oxovanadium(IV)/oxovanadium(V) redox couple of the modified electrode was found to mediate the L-dopa oxidation before its use in the FIA system. Experimental parameters, such as pH of the carrier solution, flow rate, sample volume injection and probable interferents were investigated. Under the optimized FIA conditions, the amperometric signal was linearly dependent on the L-dopa concentration over the range 1.0 x 10(-1) to 1.0 x 10(-4) mol L-1 (I-anodic, mu A) = 0.01 + 0.25 [L-dopa mu mol L-1]) with a detection limit (S/N = 3) of 8.0 x 10(-7) mol L-1 and a sampling frequency of 90 h(-1) was achieved. For a concentration of 1.0 x 10(-5) mol L-1 L-dopa, the R.S.D. of nine consecutive measurements was 3.7%. (c) 2006 Elsevier B.V. All rights reserved.

Development of an amperometric sensor for potassium ions

Hollandite-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. Sensor based on hollandite-type manganese oxide was investigated for amperometric detection of potassium. With an operating potential of +0.63 V versus SCE, potassium ions produce oxidation currents at the sensor, which can be exploited for quantitative determinations. The amperometric signals are linearly proportional to potassium ions concentration in the range 2.7 x 10(-4) to 9.1 x 10(-4) Mol l(-1) with a correlation coefficient of 0.9990. The construction and renewal are simple and inexpensive.

Phytase immobilization on modified electrodes for amperometric biosensing

Phytase (myo-inositol hexaphosphate phosphohydrolase) and phytic acid (myo-inositol hexaphosphate) play an important environmental role, in addition to being a health issue in food industry. Phytic acid is antinutritional due to its ability to chelate metal ions and may also react with proteins decreasing their bioavailability. In this work, we produced biosensors with phytase immobilized in Layer-by-Layer (LbL) films, which could detect phytic acid with a detection limit of 0.19 mmol L-1, which is sufficient to detect phytic acid in seeds of grains and vegetables. The biosensosrs consisted of LbL films containing up to eight bilayers of phytase alternated with poly(allylamine) hydrochloride (PAH) deposited onto an indium-tin oxide (ITO) substrate modified with Prussian Blue. Amperometric detection was conducted in an acetate buffer solution (at pH 5.5) at room temperature, with the biosensor response attributed to the formation of phosphate ions. In subsidiary experiments with the currents measured at 0.0 V (vs. SCE), we demonstrated the absence of effects from some interferents, pointing to a good selectivity of the biosensor. (c) 2007 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

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Investigation of the interaction between Tc85-11 protein and antibody anti-T cruzi by AFM and amperometric measurements

This present work reports on development of an amperometric immunosensor for the diagnosis of Chagas' disease using a specific glycoprotein of the trypomastigote surface, which belongs to the Tc85-11 protein family of Trypanosoma cruzi (T cruzi). An atomically flat gold surface on a silicon substrate and gold screen-printed electrodes were functionalized with cystatrine and later activated with glutaraldehyde (GA), which was used to form covalent bonds with the purified recombinant antigen (Tc85-11). The antigen reacts with the antibody from the serum, and the affinity reaction was monitored directly using atomic force microscopy or amperometry through a secondary antibody tagged to peroxidase (HRP). Surface imaging allowed to us to differentiate the modification steps and antigen-antibody interaction allowed to distinguish the affinity reactions. In the amperometric immunosensor, peroxidase catalyses the L-2 formation in the presence of hydrogen peroxide and potassium iodide, and the reduction current intensity was measured at a given potential with screen-printed electrodes. The immunosensor was applied to sera of chagasic patients and patients having different systemic diseases. (c) 2006 Elsevier Ltd. All rights reserved.

Amperometric Immunosensor for Chagas' Disease Using Gold CD-R Transducer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Studies of the Electrochemical Degradation of Acetaminophen Using a Real-Time Biomimetic Sensor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Application of Factorial Design Experiments to the Development of a Disposable Amperometric DNA Biosensor

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Direct Determination of Phosphite in Fertilizers by Amperometric Titration

Amperometric titration using two Pt microelectrodes for the determination of phosphite in fertilizers based on the oxidation of analyte by iodine is proposed. The influence of pH, buffer composition, temperature, and foreign species on the end point and titration time was investigated. For titrations carried out at 70 degrees C using the pH 6.8 phosphate buffer, samples containing ca. 0.4% (m/v) P(2)O(5) could be titrated with 0.050 mol L(-1) iodine titrant, and the end point determined by extrapolating the linear portions of the plot to their intersection coincided with the end point identified by spectrophotometry. Accuracy was checked for phosphite determination in five fertilizer samples. Results were in agreement at the 95% confidence level (paired t test) with spectrophotometry. Recoveries of phosphite added to fertilizer samples ranged from 97% to 102% regardless of the amount of spiking in several determinations. The relative standard deviation (n = 10) was 1.0% for a diluted sample containing 0.050 mol L(-1) Na(2)HPO(3).

Study of the electrochemical reduction of amoebicide Teclozan and its amperometric determination in pharmaceutical formulations

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Optimization of an amperometric biosensor for the detection of hepatitis C virus using fractional factorial designs

Fractional factorial design and factorial with center point design were applied to the development of an amperometric biosensor for the detection of the hepatitis C virus. Biomolecules were immobilized by adsorption on graphite electrodes modified with siloxane-poly(propyleneoxide) hybrid matrix prepared using the sol-gel method. Several parameters were optimized, such as the streptavidin concentration at 0.01 mg mL(-1) and 1.0% bovine serum albumin, the incubation time of the electrodes in the complementary DNA solution for 30 minutes and a 1: 1500 dilution of the avidin-peroxidase conjugate, among others. The application of chemometric studies has been efficient, since the best conditions have been established with a restricted number of experiments, indicating the influence of different factors on the system.

Amperometric biosensor for ascorbic acid

Desenvolveu-se um biossensor para ácido L-ascórbico empregando ascorbato oxidase. A enzima foi extraída do mesocarpo de pepino com solução tampão fosfato 0,05 mol L-1, pH 5,8 contendo NaCl 0,5 mol L-1. Após diálise versus solução tampão fosfato 0,05 mol L-1, pH 5,8 a enzima foi imobilizada em rede de nylon através de ligação covalente com glutaraldeído. A membrana foi acoplada em eletrodo de O2 e a reação monitorada pelo consumo de oxigênio a -600 mV em análise em fluxo (solução tampão fosfato 0,05 mol L-1, pH 5,8 como carregador e vazão 0,5 mL min-1). A curva analítica apresentou-se linear entre 1,2x10-4 a 1,0x10-3 mol L-1. O tempo de vida do biossensor foi de 500 análises. Amostras de medicamentos foram analisadas com a metodologia proposta e os resultados comparados com os obtidos com HPLC.