ABSTRACT The aim of the study is to demonstrate that the biotinylated 19 base oligonucleotide probe of the gag gene H1Gag1584 can be used as a molecular recognition element for the detection of HIV-1 proviral DNA, in two electrochemical detection systems of free laber. Two free leber electrochemical detection systems were evaluated: an impedimetric DNA genosensor using a self-assembled biotin monolayer (SAM) and a voltammetric DNA genosensor by modifying a new epoxy graphite transducer with graphene oxide. The results obtained in this study showed that the biotinylated 19-base oligonucleotide probe of the gag gene H1Gag1584 can be used as a molecular recognition element for the detection of HIV-1 proviral DNA, in two electrochemical detection systems of free labels.

RESUMEN El objetivo del estudio es demostrar que la sonda de oligonucleótidos de 19 bases biotinilada del gen gag H1Gag1584 puede utilizarse como elemento de reconocimiento molecular para la detección de ADN provírico del VIH-1, en dos sistemas de detección electroquímica de etiqueta libre. Se evaluaron dos sistemas de leber libres: un genosensor de ADN impedimétrico que utiliza una monocapa de biotina autoensamblada (SAM) y un genosensor de ADN voltamétrico mediante la modificación de un nuevo transductor de grafito epoxi con óxido de grafeno. Los resultados obtenidos en este estudio mostraron que la sonda de oligonucleótido de 19 bases biotinilada del gen gag H1Gag1584 puede utilizarse como elemento de reconocimiento molecular para la detección de ADN provírico del VIH-1, en dos sistemas de detección electroquímica de marcadores libres.

The sol-gel technique has drawn considerable attention in the area of biomolecules immobilization by virtue of its intrinsic properties including chemical inertness, thermal stability, and good biocompatibility. The present work reports the development of a bio-sensing methodology which involves the immobilization of horseradish peroxidase enzyme (HRP) on pencil graphite electrode (PGE) using TiO2 sol-gel and its application for 5-aminosalicylic acid (5-ASA) determination in pharmaceutical formulations. TiO2 sol-gel film was deposited on the PGE surface by dip coating, and the HRP enzyme was immobilized on the film by adsorption and cross-linked binding using glutaraldehyde. The analytical performance of the methodology was investigated through amperometric measurements at -0.08 V in the presence of 5-ASA (electron mediator) and hydrogen peroxide (substrate). The biosensor was successfully applied for 5-ASA determination, where limits of detection and quantification of 3.3 and 10.0 µmol L -1, respectively, were obtained. The application of the methodology for 5-ASA determination in pharmaceutical formulations led to satisfactory recovery rates ranging from 80 to 98%. The biosensor developed in this work is simple, inexpensive and has the potential to be applied for the determination of other pharmaceutical compounds, which also act as electron mediators in the catalytic cycle of HRP.

Electrochemistry and Electroanalytical chemistry play an important role to face the challenges of the contemporary world. They have contributed to the advance of the scientific development of our country, helped to promote economic and social progress as well as cultural dissemination. These areas have greatly contributed to the knowledge about thermodynamics and kinetics of the electron transfer reactions, energy conversion, synthesis and modification of compounds, corrosion, and development of fast, sensitive, and selective analytical methods. This work presents an overview of the areas by analyzing the technical and scientific papers produced in Brazil on these subjects, and the analysis of the Brazilian scientific societies that were formed and consolidated, which have contributed to spread the scientific knowledge. The improvement of these areas can be attributed to the good quality of the human resources formed during long time as well as the growing of distribution of research groups in different regions of the country. The success/future of these areas are associated with good academic/scientific education, low cost of instrumentation, formation of networks of excellence between researchers, and large cooperation projects that improved with the sharing of ideas, technologies, infrastructure, and equipment. All of which has contributed to strengthening consolidated and emerging graduation programs.

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.

Eletrodo de diamante foi usado para avaliar a interação dos nucleotídeos guanosina monofosfato (GMP) e adenosina monofosfato (AMP) com os pesticidas clorpirifós, metamidofós e monocrotofós. Observaram-se alterações nas correntes e potenciais de picos dos voltamogramas dos nucleotídeos na presença dos pesticidas dependendo da concentração de pesticida (de 5,0 × 10-7 a 5,0 × 10-5 mol L-1) e do tempo de interação (de 1 min a 4 h). Isto é provavelmente devido à ligação dos pesticidas às bases nitrogenadas presentes nos nucleotídeos, o que poderia levar a problemas na replicação do DNA e nas funções biológicas de nucleotídeos. Os pesticidas apresentaram maior interação com AMP que com GMP. Estudos sobre a interação de DNA 50 µg mL-1 com os pesticidas (de 30 min até 4 h, e de 1,0 × 10-6 a 6,0 × 10-5 mol L-1) não revelaram picos relativos à abertura da dupla hélice ou desenrolamento do DNA.

Diamond electrode was used to evaluate the interaction of the nucleotides guanosine monophosphate (GMP) and adenosine monophosphate (AMP) with the pesticides chlorpyrifos, methamidophos and monocrotophos. Changes were observed in the currents and peak potentials of the nucleotide voltammograms in the presence of the pesticides, with dependence on the pesticide concentration (from 5.0 × 10-7 to 5.0 × 10-5 mol L-1) and the interaction time (from 1 min to 4 h). This is probably due to binding of the pesticides to the nitrogenous bases present in the nucleotides, which could lead to problems in the DNA replication and biological functions of nucleotides. The pesticides showed stronger interaction with AMP than with GMP. Studies of the interaction of 50 µg mL-1 DNA with the pesticides (from 30 min to 4 h and from 1.0 × 10-6 to 6.0 × 10-5 mol L-1) did not reveal any peaks relating to double helix opening or DNA unwinding.

A espectrofotometria UV-Vis foi utilizada para medir a solubilidade do corante disperso red 1 (DR1) em soluções aquosas, com diferentes solventes e dispersantes. O corante foi quantificado em amostras de águas, e sua interação com o ds-DNA de timo de vitelo foi investigada. Os resultados mostraram que o dispersante comercial Fongranal® FB foi adequado para a preparação das soluções aquosas do DR1. Para a determinação de DR1 em água pura, o limite de detecção foi de 2,47 × 10-6 mol L-1, e o limite de quantificação, 8,22 × 10-6 mol L-1. Porcentagens de recuperação de 91,2 e 103% foram obtidas para as concentrações de DR1 em 3,00 × 10-6 e 40,0 × 10-6 mol L-1, respectivamente. As recuperações alcançadas de DR1 em água de torneira e de rio ficaram na faixa de 85,9-113%. A interação de DR1 com o DNA de timo de vitela foi acompanhada por efeitos de hipocromismo e hipercromismo, que foram relacionados à mudanças conformacionais e lesão na dupla hélice do DNA.

UV-Vis spectrophotometry was used to measure the solubility of disperse red 1 (DR1) dye in aqueous solutions, using different solvents and dispersants. The dye was quantified in water samples, and its interaction with calf thymus ds-DNA was investigated. The results showed that the commercial dispersant Fongranal® FB was suitable for the preparation of aqueous DR1 solutions. For the determination of DR1 in purified water, the limit of detection was 2.47 × 10-6 mol L-1, and the limit of quantification was 8.22 × 10-6 mol L-1. Percentage recoveries of 91.2 and 103% were obtained for DR1 concentrations of 3.00 × 10-6 and 40.0 × 10-6 mol L-1, respectively. The recoveries achieved for DR1 present in tap and river water were in the range 85.9-113%. The interaction of DR1 with calf thymus DNA was accompanied by hypochromic and hyperchromic effects, which were related to conformational changes and damage to the DNA double helix.

A detecção individual e em mistura equimolar dos nucleotídeos de DNA guanosina (GMP), adenosina (AMP), timidina (TMP) e citidina (CMP) 5'-monofosfato, utilizando a voltametria de onda quadrada, foi realizada sobre o eletrodo de diamante dopado com boro (DDB) prétratado catodicamente (Red-DDB) e anodicamente (Oxi-DDB). A oxidação dos nucleotídeos individuais de DNA foi mais sensível sobre o Oxi-DDB. Na detecção simultânea de nucleotídeos, as respostas de GMP, AMP, TMP e CMP foram muito adequadas sobre ambos os eletrodos tratados. Particularmente, picos mais sensíveis e mais separados para TMP e CMP sobre o Oxi-DDB e Red-DDB, respectivamente, foram observados após procedimento de deconvolução. A detecção dos nucleotídeos em soluções aquosas certamente contribuirá para avaliação genotóxica de substâncias e em reações de hibridização por meio da imobilização de ss ou ds-DNA sobre a superfície do DDB.

The individual detection and equimolar mixture of DNA nucleotides guanosine monophosphate (GMP), adenosine monophosphate (AMP), thymidine (TMP) and cytidine (CMP) 5'-monophosphate using square wave voltammetry was performed on boron doped diamond (BDD) electrodes cathodically (Red-DDB) and anodically (Oxi-DDB) pretreated. The oxidation of individual DNA nucleotides was more sensitive on Oxi-BDD electrode. In a simultaneous detection of nucleotides, the responses of GMP, AMP, TMP and CMP were very adequate on both treated electrodes. Particularly, more sensitive and separate peaks for TMP and CMP on Oxi-BDD and Red-BDD electrodes, respectively, were observed after deconvolution procedure. The detection of nucleotides in aqueous solutions will certainly contribute for genotoxic evaluation of substances and hybridization reactions by immobilizing ss or ds-DNA on BDD surface.

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.

A hidrólise de lactose de soro de leite, resultando em glicose e galactose, apresenta-se como uma alternativa para ampliar as possibilidades de uso comercial deste insumo. Para ser aplicado em escala industrial, o processo deve ser operado de modo contínuo. Reporta-se o estudo de um sistema objetivando hidrólise de lactose de soro de leite através de um reator com enzima imobilizada. b-Galactosidase de Aspergillus oryzae foi imobilizada em sílica, sendo avaliadas a estabilidade e atividade. Os melhores resultados de imobilização foram obtidos usando glutaraldeído como ativante do suporte e estabilizador da enzima. A proporção otimizada entre enzima e suporte foi 15-20 mg.g-1. Foram estudadas formas de tratamento do soro (microfiltração, tratamento térmico e ultrafiltração), objetivando eliminação de material suspenso, e avaliando os efeitos na operação de reator de leito fixo. A ultrafiltração foi o melhor tratamento, na busca de uma solução de substrato apropriada para o reator contínuo.

Hydrolysis of whey lactose to glucose and galactose by immobilized galactosidase comes as an alternative to enlarge the possibilities of commercial use of this feedstock. To be applied at industrial scale, the process should be performed continuously .This work aimed to study the hydrolysis of whey lactose by an immobilized enzyme reactor. b-Galactosidase from Aspergillus oryzae was immobilized on silica and activity and stability were evaluated. The best immobilization results were attained by using glutaraldehyde as support's activator and enzyme stabilizer. The optimized enzyme proportion for immobilization was 15-20 mg g-1 of support. Treatments of whey were performed (microfiltration, thermal treatment and ultrafiltration), seeking the elimination of sludge, and the effects on operating the fixed bed reactor were evaluated. Ultrafiltration was the best treatment towards a proper substrate solution for feeding the reactor.

Fast, selective, reproducible and reliable detections have been carried out by using enzymatic biosensors in several areas. The enzymatic biosensors based on the inhibition represent an important role in analytical chemistry. Enzymes like cholinesterases, peroxidases, tyrosinases, etc. have been immobilized on electrochemical and optical transducers and the enzymatic activity decreasing in the presence of the inhibitor is related with its concentrations. This article presents a review on the enzymes used on the construction of these sensors, emphasizing the respective applications.

O planejamento fatorial fracionário e com ponto central foram aplicados no desenvolvimento de um biossensor amperométrico para determinação do vírus da hepatite C. As biomoléculas foram imobilizadas por adsorção em eletrodos de grafite modificados com filme sol-gel preparado com matriz híbrida siloxano-poli(propileno-óxido). Diversos parâmetros foram otimizados, tais como a concentração da estreptavidina em 0,01mg mL-1 e albumina de soro bovino em 1,0%, o tempo de incubação dos eletrodos de 30 minutos na solução do DNA complementar e a diluição do conjugado avidina-peroxidase em 1:1500, entre outros. A aplicação de estudos quimiométricos mostrou-se eficiente, pois as melhores condições foram estabelecidas com um menor número de experimentos, além de apontar quais os fatores exercem maiores influências sobre o sistema.

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.

Foi realizado um estudo comparativo entre duas metodologias de imobilização do Azul de Meldola (MB), utilizado para diminuir o potencial de oxidação do NADH. O estudo foi realizado no eletrodo de carbono vítreo através da eletropolimerização do pirrol e MB, empregando a técnica de voltametria cíclica e avaliando-se o efeito do número de ciclos para definir a espessura e a estabilidade do filme. Com 25 ciclos foi obtido o melhor resultado. Foi também investigada a modificação do eletrodo de grafite com filme formado pelo sistema sol-gel PPO 300 ou PPO 4000 pelo método de recobrimento por mergulho, através de dois métodos: oclusão e adsorção. O melhor método foi o de adsorção da MB durante 10 min, seguida de depósito do filme PPO 300, favorecido pelo tempo de secagem (24 horas). A adsorção da MB seguido do depósito do PPO 300 apresentou maior intervalo linear do que a metodologia do PPY.

A comparative study was accomplished between two immobilization methodologies for the meldola's blue (MB), used to decrease the oxidation potential of NADH. The study was performed with glassy carbon electrode by electropolymerization of pyrrole and MB through the technique of cyclic voltammetry being evaluated the effect of the number of cycles to define the thickness and the stability of the film. With 25 cycles it was obtained the best result. They were also investigated the modification of the graphite electrode with film formed by the system sol-gel PPO 300 or PPO 4000 for the dip-coating, through two methods: occlusion and adsorption. The best method was it of adsorption of MB during 10 min, following by deposit of the film PPO 300, favored for the time of drying (24 hours). The adsorption of MB followed by PPO 300 deposition presented broader linear range than PPy methodology.

Affinity reactions have been used for specific detection of their complementary partners and an enormous variety of enzyme-linked immunosorbent assay (ELISA) formats are used in research and in routine serological tests. With the advent of the atomic force microscopy (AFM) technique, the immune reactions have been monitored by these devices. In the present article we focus on applications of AFM to immunoassays. After introducing the basic concepts of AFM, a brief discussion on the monitoring of the interactions between antigens and antibodies through both topographic image and biosensor systems is presented.

Sensores potenciométricos, amperométricos e condutométricos são sensores eletroquímicos com imensa aplicação nas áreas de meio ambiente, indústria e análises clínicas. O presente trabalho apresenta uma revisão generalizada dos aspectos fundamentais, os desenvolvimento e a contribuição destes sensores na área de química analítica, e reporta alguns aspectos relevantes dos avanços na área de sensores eletroquímicos no Brasil.

Potentiometric, amperometric and conductometric electrochemical sensors have found a number of interesting applications in the areas of environmental, industrial, and clinical analyses. This review presents a general overview of the three main types of electrochemical sensors, describing fundamental aspects, developments and their contribution to the area of analytical chemistry, relating relevant aspects of the development of electrochemical sensors in Brazil.

The reaction between antigen and antibody has been widely used in many strategies for the development of analytical methodology, due to its high specificity. The immuno-reaction has been successfully employed for the biosensor development. A focus on biosensor based on immunoassay coupled to amperometric transducer is presented.