Papers by ROSA AMALIA FIREMAN DUTRA
World Academy of Science, Engineering and Technology, International Journal of Bioengineering and Life Sciences, Dec 18, 2017
Current Topics in Electrochemistry, 2013
Revista de Ciências Farmacêuticas Básica e Aplicada, Sep 18, 2017
Introducao: A construcao de biossensores tem se tornado uma atividade ampla no ramo da ciencia vi... more Introducao: A construcao de biossensores tem se tornado uma atividade ampla no ramo da ciencia visando principalmente questoes de saude e de meio ambiente. O seu desenvolvimento em laboratorio tem sido trabalhado por varios grupos de pesquisa buscando dispositivos especificos, de baixo custo, facil manuseio e preparacao. Eletrodos modificados com polimeros estao sendo utilizados, pois melhoram a resposta analitica alem de auxiliarem na imobilizacao das biomoleculas. Objetivo: Objetivou-se a modificacao de eletrodos de grafite de lapiseira com material polimerico derivado do monomero acido 3-amino-4-hidroxibenzoico para possivel imobilizacao de moleculas de interesse biologico. Metodologia: O eletrodo foi eletro modificado por voltametria ciclica com material derivado do monomero acido 3-amino-4-hidroxibenzoico em meio de acido sulfurico. Utilizou-se eletrodos de grafite com grande area superficial visando extrair o material formado. Apos a modificacao foram lavados e colocados em um recipiente contendo acetonitrila. Os eletrodos foram levados a um aparelho de ultrassom por 2 horas para extracao do material. O material extraido foi seco por rotaevaporacao e deixado em dessecador a vacuo. As amostras secas foram enfim levadas a um espectrometro de infravermelho marca Bruker modelo vertex 70. Os dados foram gravados em transmitância na faixa de 400 a 4000 cm-1, resolucao de 4 cm-1, 64 varreduras. O espectro de infravermelho do material obtido por eletropolimerizacao foi entao comparado com o espectro do monomero. Resultados e discussao: No espectro do monomero foi observado os estiramentos de ligacoes dos tipos O-H de ligacoes de hidrogenio (fenol e acido carboxilico), C-H no anel aromatico, C=C de aromatico, N-H, O-H no plano (fenol), C-O (fenol), C=O do acido carboxilico, C-H fora do plano de aneis trissubstituidos nas posicoes 1,2,4. As bandas relacionadas ao grupo amino, como estiramento C-N, e N-H sao muito pequenas o que pode ser indicio que foram sobrepostas pelas contribuicoes da hidroxila e da carboxila ficando dificil a analise desse grupo isoladamente. Ja no espectro do material eletropolimerizado extraido pode-se observar a presenca das mesmas bandas de deformacao axial, alem disso pode ser visto o aparecimento de banda provavelmente relacionada ao estiramento simetrico C-O-C, o que garante que o grupo hidroxila nao mais exista na forma livre e sim como um eter aromatico. Infelizmente as bandas de C-N de aminas primarias, secundarias e terciarias absorvem na mesma regiao, o que torna dificil prever se o mecanismo de reacao ocorre pelo atomo de nitrogenio ou de oxigenio. Conclusao: Apesar da incerteza sobre a presenca e/ou modificacao dos grupos amino e hidroxila no processo de polimerizacao, a partir da analise dos espectros pode-se ter certeza da presenca do grupo carboxilico como desejado para futura interacao com as biomoleculas, via ligacao covalente.
Proceedings of the 2001 SBMO/IEEE MTT-S International Microwave and Optoelectronics Conference. (Cat. No.01TH8568)
... Eduardo Fontana, Rosa F. Dutra and Jos6 O thio Maciel Net0 ... This lower limit is usually hi... more ... Eduardo Fontana, Rosa F. Dutra and Jos6 O thio Maciel Net0 ... This lower limit is usually higher than that reached by conventional labeling methods, such as the enzyme linked imunosorbent assay (ELISA) and the radioimmunoassay (RIA). ...
Biomedical Diagnostic, Guidance, and Surgical-Assist Systems III, 2001
ABSTRACT The Surface Plasmon Resonance (SPR) technique is considered by many researchers as a ver... more ABSTRACT The Surface Plasmon Resonance (SPR) technique is considered by many researchers as a very attractive approach for immunosensor development. By proper chemical modification of the gold surface, this technique avoids the use of a tracer material, such as a radioisotope, fluorophore, or enzyme, to identify the specific analyte, thus allowing kinetic analysis of biointeracting systems. However, the technique has found limited applications for the direct assay of complex biological samples due to the variable degree of non-specific binding that may occur along with the primary antigen-antibody reaction. This work describes a possible approach for the development of a new class of SPR based assays where non-specific binding effects could be minimized. The principle relies on selective UV inactivation of a gold surface coated with either antibody or antigen molecules. It is shown that under proper conditions it is possible to synthesize a surface with a pre-defined 2D variation of immunoactivity. Following exposure to a positive sample, image contrast under SPR illumination of the immunoactivated surface would be indicative of a positive reaction. The degree of SPR image contrast can be quantified and is a measure of the analyte concentration in solution. The approach minimizes non-specific binding effects, and the principle can be extended for the development of immunoassays for large scale testing of complex biological samples.
BioMed Research International, 2014
A simple amino-functionalization method for carbon nanotubes and its application in an electroche... more A simple amino-functionalization method for carbon nanotubes and its application in an electrochemical immunosensor for detection of the human cardiac troponin T are described. Amino-functionalized carbon nanotubes allow oriented antibodies immobilization via their Fc regions, improving the performance of an immunosensor. Herein multiwalled carbon nanotubes were amino-functionalized by using the ethylenediamine reagent and assays were designed by fractional factorial study associated with Doehlert matrix. Structural modifications in the carbon nanotubes were confirmed by Fourier transform infrared spectroscopy. After amino-functionalization the carbon nanotubes were attached to screen-printed carbon electrode and a sandwich-type immunoassay was performed for measuring the cardiac troponin T. The electrochemical measurements were obtained through hydrogen peroxide reaction with peroxidase conjugated to the secondary antibody. Under optimal conditions, troponin T immunosensor was eval...
Talanta, 2011
A biomimetic sensor for the determination of dipyrone was prepared by modifying carbon paste with... more A biomimetic sensor for the determination of dipyrone was prepared by modifying carbon paste with cobalt phthalocyanine (CoPc), and used as an amperometric detector in a flow injection analysis (FIA) system. The results of cyclic voltammetry experiments suggested that CoPc behaved as a biomimetic catalyst in the electrocatalytic oxidation of dipyrone, which involved the transfer of one electron. The optimized FIA procedure employed a flow rate of 1.5 mL min −1 , a 75 L sample loop, a 0.1 mol L −1 phosphate buffer carrier solution at pH 7.0 and amperometric detection at a potential of 0.3 V vs. Ag/AgCl. Under these conditions, the proposed method showed a linear response for dipyrone concentrations in the range 5.0 × 10 −6-6.3 × 10 −3 mol L −1. Selectivity and interference studies were carried out in order to validate the system for use with pharmaceutical and environmental samples. In addition to being environmentally friendly, the proposed method is a sensitive and selective analytical tool for the determination of dipyrone.
Biotechnology Letters, 2000
A renewable immunosensor consisting of an `epoxygraphite' biocomposite containing silver and ... more A renewable immunosensor consisting of an `epoxygraphite' biocomposite containing silver and tetracyanoquinodimethane (TCNQ) is described. These compounds enhance conductivity allowing the use of a smaller potential (0.28 v) which, in turn, enhances selectivity. This sensor, which may be renewed by simple polishing of its surface, was employed to detect human IgG using peroxidase-coupled anti-human IgG.
Eclética Química, 2011
Um biossensor amperométrico foi desenvolvido para detecção de peróxido de hidrogênio em amostras ... more Um biossensor amperométrico foi desenvolvido para detecção de peróxido de hidrogênio em amostras de leite. O biossensor foi construído a partir da imobilização de enzima peroxidase sobre eletrodo impresso de carbono. Parâmetros de otimização visando um melhor desempenho do biossensor foram avaliados. O biossensor apresentou linearidade no intervalo de 5,0 a 40,0 µ mol L-1 de H2O2 em tampão fosfato. Em amostras de leite sem diluição, os limites de detecção e quantificação foram de 0,42 µmol L-1 e 1,39 µmol L-1, respectivamente. O biossensor mostrou-se uma alternativa sensível e de baixo custo na detecção de H2O2 em amostras adulteradas de leite.
Ciência e Agrotecnologia, 2011
A ricina é uma proteína bastante tóxica presente nas sementes de mamona que impossibilita o uso d... more A ricina é uma proteína bastante tóxica presente nas sementes de mamona que impossibilita o uso da torta de mamona "in natura", como ração. A torta de mamona destoxificada necessita ainda de métodos de análise que garantam a ausência de traços dessa proteína. Objetivou-se, neste trabalho, produzir e avaliar a sensibilidade e especificidade de anticorpos policlonais anti-ricina, para serem empregados como possíveis componentes de métodos sorológicos na detecção de ricina em torta de mamona destoxificada. Foram avaliadas três doses da proteína: 400, 180 e 100 µg cada uma dividida em duas aplicações em coelhos. A primeira dose foi injetada no animal no início do experimento e a segunda após 21 dias. O método de ELISA indicou que as duas doses menores (100 e 180 µg) induziram respostas imunológicas primária e secundária com produção de anticorpos específicos. Enquanto a dose maior (400 µg) de ricina apresentou uma resposta primária com elevação dos títulos de anticorpos, segui...
revista da universidade vale do rio verde, 2014
Staphylococcal enterotoxin is one of the more aggressive enterotoxins produced by Staphylococcus ... more Staphylococcal enterotoxin is one of the more aggressive enterotoxins produced by Staphylococcus aureus strains and it is a common cause of food poisoning. Analytical methods that are sensitive, low cost and easy to use are needed to evaluate the food quality. This work describes the development of a label free immunosensor based on screen-printed AuNPs/carbon and the characterization of its analytical response for staphylococcal enterotoxin B (SEB) detection. The biosensor was constructed from self-assembled monolayer of thiols and protein A for the oriented immobilization of the polyclonal antibodies against SEB. As electrons mediator, potassium ferrocyanide was used. The electrochemical detection was direct with the parameters following:-0.2 to 0.6 V with the pulse amplitude of 0.075 V and the pulse width of 75 ms. The immunosensor showed detection and quantification limits of 0.4 µg mL-1 and 1.6 µg mL-1 , respectively. The immunosensor showed quite satisfactory performance in contaminated and non-contaminated cheese samples.
Workshop on Specialty Optical Fibers and their Applications, 2013
We present a new dengue diagnose method with an all-optical fiber sensor based on LSPR from Au na... more We present a new dengue diagnose method with an all-optical fiber sensor based on LSPR from Au nanoparticles.
Latin America Optics and Photonics Conference, 2012
An all-optical fiber sensor based on Localized Surface Plasmon Resonance (LSPR) and specular refl... more An all-optical fiber sensor based on Localized Surface Plasmon Resonance (LSPR) and specular reflection from gold nanoparticles (NPs) has been functionalized detecting NS1 protein of dengue virus.
Talanta, 2013
Label-free immunosensor based on amine-functionalized carbon nanotubes screen-printed electrode i... more Label-free immunosensor based on amine-functionalized carbon nanotubes screen-printed electrode is described for detection of the cardiac troponin T, an important marker of acute myocardial infarction. The disposable sensor was fabricated by tightly squeezing an adhesive carbon ink containing carbon nanotubes onto a polyethylene terephthalate substrate forming a thin film. The use of carbon nanotubes increased the reproducibility and stability of the sensor, and the amine groups permitted nonrandom immobilization of antibodies against cardiac troponin T. Amperometric responses were obtained by differential pulse voltammetry in presence of a ferrocyanide/ferricyanide redox probe after troponin T incubation. The calibration curve indicated a linear response of troponin T between 0.0025 ng mL(-1) and 0.5 ng mL(-1), with a good correlation coefficient (r=0.995; p<0.0001, n=7). The limit of detection (0.0035 ng mL(-1) cardiac troponin T) was lower than any previously described by immunosensors and was comparable with conventional analytical methods. The high reproducibility and clinical range obtained using this immunosensor support its utility as a potential tool for point-of-care acute myocardial infarction diagnostic testing.
Sensors and Actuators B: Chemical, 2012
An immunosensor based on dual quartz crystal microbalance (Dual-QCM) for human cardiac troponin T... more An immunosensor based on dual quartz crystal microbalance (Dual-QCM) for human cardiac troponin T (cTnT) was developed. The self-assembled monolayer by cysteamine was used to immobilize the monoclonal antibody against cTnT (mAb-cTnT). The mAb-cTnT was immobilized on the amine-coated surface via glutaraldehyde. The effect of the cysteamine concentrations on the SAM coated gold sensor was studied as a function of
Process Biochemistry, 2007
Porous silicon layers fabricated by the reaction-induced vapor phase stain etch method were coate... more Porous silicon layers fabricated by the reaction-induced vapor phase stain etch method were coated with 5% polyethylenimine. Urease from Canavalia brasiliensis beans was immobilized on this support through covalent linking with 2.5% glutaraldehyde. The pH and temperature profile of the immobilized and free urease exhibited higher activity at pH 6.5 and 37 8C. After being stored for 30 days at 4 8C, the immobilized enzyme had 75% of the initial activity. The maximum apparent Michaelis constant for free urease (K m) was 94.33 mM whereas for immobilized urease was 53.04 mM. The maximum reaction velocity (V max) for free urease was 3.51 mmol/min and for immobilized urease was 1.57 mmol/min.
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Papers by ROSA AMALIA FIREMAN DUTRA