A simple architecture with self-assembled monolayers to build immunosensors for detecting the pancreatic cancer biomarker CA19-9

Accepted ManuscriptThe challenge of the early diagnosis of pancreatic cancer in routine clinical practice requires low-cost means of detection, and this may be achieved with immunosensors based on electrical or electrochemical principles. In this paper, we report a potentially low-cost immunosensor built with interdigitated gold electrodes coated with a self-assembled monolayer and a layer of anti-CA19-9 antibodies, which is capable of detecting the pancreatic cancer biomarker CA19-9 using electrical impedance spectroscopy. Due to specific, irreversible adsorption of CA19-9 onto its corresponding antibody, according to data from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), the immunosensor is highly sensitive and selective. It could detect CA19-9 in commercial samples with a limit of detection of 0.68 U mL−1, in addition to distinguishing between blood serum samples from patients with different concentrations of CA19-9. Furthermore, by treating the capacitance data with information visualization methods, we were able to verify the selectivity and robustness of the immunosensor with regard to false positives, as the samples containing higher CA19-9 concentrations, including those from tumor cells, could be distinguished from those with possible interferents.CAPES, FAPESP (Grant 2013/14262-7 and 2012/15543-7), CNPq (150985/2017-7), nBioNet network and Barretos Cancer Hospital for financial supportinfo:eu-repo/semantics/publishedVersio

Polypyrrole/phytase amperometric biosensors for the determination of phytic acid in standard solutions

Amperometric biosensors based on the physical immobilization of phytase (PhyA) into polypyrrole (PPy) films were prepared in aqueous medium. The PPy/PhyA films were characterized by cyclic voltammetry, and surface and structural characterization techniques, SEM and FTIR. Both voltammetric and amperometric transduction methods were used in order to detect phytic acid in acetate buffer at pH 5.5 at room temperature. The biosensors exhibited a detection limit of 0.15 mmol L-1 and a linear range of phytic acid content from 0.5 to 2.0 mmol L-1, which are adequate values for typical analyses of phytic acids in most seeds, grains, and vegetablesFAPESPCAPESCNP

Not available

Este trabalho descreve a síntese eletroquímica, a caracterização eletroquímica e estrutural e as propriedades ópticas dos filmes de poli(p−fenileno) (PPP), poli−3−metiltiofeno (P3MET), polipirrol (PPI) e dos derivados poli−p−fenileno−3−metiltiofeno (CP3MET) e poli−p−fenileno−pirrol (CPPI). Nossa motivação pode ser justificada pelo fato de o PPP e dos derivados serem polímeros conjugados eletroluminescentes na região do azul e importantes candidatos a serem empregados como camadas ativas em dispositivos emissores de luz (LEDs). Os filmes foram eletroquimicamente sintetizados sobre eletrodos de óxido de estanho dopado com flúor (FTO) em um meio não−aquoso de acetonitrila e perclorato de tetrabutilamônio. A resposta eletroquímica dos filmes de PPP, P3MET, PPI, CP3MET e CPPI foi investigada por voltametria cíclica em uma solução livre de monômeros, quando se verificou a formação de filmes eletroativos e estáveis eletroquimicamente. As propriedades ópticas dos filmes foram investigadas por espectroscopia de absorção in situ no UV−VIS, uma técnica amplamente usada para se estudar a estrutura eletrônica da maioria dos polímeros. Os espectros de UV−VIS dos filmes de PPP, P3MET, PPI, CP3MET e CPPI foram obtidos a diferentes potenciais, quando se verificou a ocorrência da transição π− π∗ dos filmes em seu estado neutro e a formação de estados polarônicos e bipolarônicos dos polímeros durante a sua oxidação. A caracterização estrutural dos filmes foi investigada por espectroscopia FT−Raman e FTIR, quando se verificou que o espectro dos filmes de CP3MET e CPPI, preparados por eletrooxidação de co−monômeros, apresentavam apenas as bandas características dos filmes dos homopolímeros, P3MET e PPIThis work describes the e1ectrochemical synthesis, structural and electrochemical characterization, and the optical properties of poly(p−phenylene) (PPP), poly(3−methylthiophene) (P3MET), polypyrrole (PPI) and their derivatives poly(p−phenylene−3−methylthiophene) (CP3MET) and poly(p−phenylene−pyrrole) (CPPI) films. Our motivation cab be justified by the fact that poly(p−phenylene) (PPP) and its derivatives are conjugated polymers that emit in the blue range of energy, and they appoint as potential candidates as active layers in displays (LEDs). The films were electrochemically synthesized on fluorine−tin−oxide glass (FTO) electrodes in a nonaqueous medium contend acetonitrile and TBAClO4. The electrochemical response of the PPP, P3MET, PPI, CP3MET and CPPI films were investigated by cyc1ic voltammetry in a monomer−free solution with the films showing a typical electroactive response. Their optical properties were investigated by in situ UV−VIS absorption spectroscopy, a technique widely used aiming at understanding the electronic structure of most polymers. The UV−VIS spectra of the PPP, P3MET, PPI, CP3MET and CPPI films were obtained at different p−doping states, i.e., at different applied potential allowing us to calculate the π− π∗ transition of the films at their neutral, and polaronic and bipolaronic states. The structural characterization of the films was investigated by FT−Raman and FTIR spectroscopy, where it was verified that the films prepared by the electrooxidation of co−monomers showed only the bands that were typical of those ones observed in the spectra of the homopolymers, P3MET and PPI

Electrochemical biosensors fabricated by the immobilization of urease in polypyrrole films

A urease (Canavalia ensiformis DC.) foi fisicamente imobilizada em matrizes de polipirrol (PPI) com o objetivo de se detectar uréia em amostras padrão. A eletropolimerização do pirrol foi realizada por voltametria cíclica em uma faixa de potencial de -1,0 a 1,0 V vs. ECS em um meio aquoso contendo 0,2 mol/L de \'LI\'CL\'O IND.4\' e 0,1 mol/L de pirrol. Este procedimento permitiu também a imobilização da enzima na matriz polimérica em suas formas, urease purificada (comercial) e como extrato bruto obtido a partir do feijão de porco (Jack Bean), após a adição de 300 \'mü\'g/mL de urease purificada ou 100 \'mü\'L de extrato bruto de feijão de porco. A urease purificada possui 34.375 U/g de sólido e o extrato bruto, 13.000 UA/mL, valores obtidos por titrimetria. A presença da enzima imobilizada nos filmes de PPI foi verificada por voltametria cíclica, FTIR, microscopia eletrônica de varredura (MEV), microscopia de força atômica (AFM) e por uma microbalança de cristal de quartzo (MCQE). A atividade da enzima após a imobilização nos filmes de PPI foi confirmada pela presença de íons amônio em solução, que são formados como produtos da reação de hidrólise da uréia catalisada pela enzima. Como o transdutor influencia a eficiência e a sensibilidade do biossensor, dois métodos de transdução foram estudados: cronoamperometria, aplicando-se um potencial de -0,28 V durante 120 s em tampão fosfato pH 7,0 e a cronopotenciometria, aplicando-se uma corrente de 1,0 mA durante 120 s em tampão fosfato pH 7,0 variando-se a concentração de uréia. O principal objetivo deste trabalho foi avaliar a eficiência do biossensores para a detecção de uréia por meio de transdutores potenciométricos e amperométricos e depois comparar as eficiências dos filmes de PPI/urease purificada e PPI/extrato bruto como biosensores.Urease (Canavalia ensiformis DC.) was physically immobilized on polypyrrole (PPy) films aiming at detecting urea in standard samples. The electropolymerization of pyrrole was performed by cyclic voltammetry at a potential range from -1.0 to 1.0 V vs SCE in an aqueous medium containing \'LI\'CL\'O IND.4\' 0.2 mol/L and 0.1 mol/L pyrrole. This procedure also allowed us to immobilize the enzyme into the PPy matrix in forms, commercially purified and crude extract of urease obtained from Jack Bean (Canavalia ensiformis) after adding into the electropolymerization media 300 \'mü\'g/mL of purified urease or 100 \'mü\'L of crude extract. The urease solutions had units of active enzyme of 34.375 U/g (purified) and 13.000 UA/mL (crude extract), and the crude extract was obtained from Jack beans by titrimétric methods. The presence of urease immobilized into the PPy film was verified by cyclic voltammetry, FTIR, scanning electron microscopy (SEM), atomic force microscopy (AFM), and by electrochemical quartz crystal microbalance (EQCM) The activity of the enzyme after immobilizing into the PPy films was confirmed by the presence of ammonium ions in solution, since they are formed as catalytic products by urea hydrolysis reaction catalyzed enzyme. The transducer element influences the efficiency and sensitivity of the biosensor, and two transducer methods were studied: chronoamperometry, by applying a potential of -0.28 V during 120 s in buffer phosphate at pH 7.0 and chronopotentiometry, by applying a current of 1.0 mA during 120 s in buffer phosphate at pH 7.0 both after varying the urea concentration. Our main purpose was to evaluate the efficiency of the biosensors for detecting urea by means of potentiometric and amperometric transducers and then compare the efficiencies of PPY/purified urease e PPY/crude extract as biosensors

Not available

Este trabalho descreve a síntese eletroquímica, a caracterização eletroquímica e estrutural e as propriedades ópticas dos filmes de poli(p−fenileno) (PPP), poli−3−metiltiofeno (P3MET), polipirrol (PPI) e dos derivados poli−p−fenileno−3−metiltiofeno (CP3MET) e poli−p−fenileno−pirrol (CPPI). Nossa motivação pode ser justificada pelo fato de o PPP e dos derivados serem polímeros conjugados eletroluminescentes na região do azul e importantes candidatos a serem empregados como camadas ativas em dispositivos emissores de luz (LEDs). Os filmes foram eletroquimicamente sintetizados sobre eletrodos de óxido de estanho dopado com flúor (FTO) em um meio não−aquoso de acetonitrila e perclorato de tetrabutilamônio. A resposta eletroquímica dos filmes de PPP, P3MET, PPI, CP3MET e CPPI foi investigada por voltametria cíclica em uma solução livre de monômeros, quando se verificou a formação de filmes eletroativos e estáveis eletroquimicamente. As propriedades ópticas dos filmes foram investigadas por espectroscopia de absorção in situ no UV−VIS, uma técnica amplamente usada para se estudar a estrutura eletrônica da maioria dos polímeros. Os espectros de UV−VIS dos filmes de PPP, P3MET, PPI, CP3MET e CPPI foram obtidos a diferentes potenciais, quando se verificou a ocorrência da transição π− π∗ dos filmes em seu estado neutro e a formação de estados polarônicos e bipolarônicos dos polímeros durante a sua oxidação. A caracterização estrutural dos filmes foi investigada por espectroscopia FT−Raman e FTIR, quando se verificou que o espectro dos filmes de CP3MET e CPPI, preparados por eletrooxidação de co−monômeros, apresentavam apenas as bandas características dos filmes dos homopolímeros, P3MET e PPIThis work describes the e1ectrochemical synthesis, structural and electrochemical characterization, and the optical properties of poly(p−phenylene) (PPP), poly(3−methylthiophene) (P3MET), polypyrrole (PPI) and their derivatives poly(p−phenylene−3−methylthiophene) (CP3MET) and poly(p−phenylene−pyrrole) (CPPI) films. Our motivation cab be justified by the fact that poly(p−phenylene) (PPP) and its derivatives are conjugated polymers that emit in the blue range of energy, and they appoint as potential candidates as active layers in displays (LEDs). The films were electrochemically synthesized on fluorine−tin−oxide glass (FTO) electrodes in a nonaqueous medium contend acetonitrile and TBAClO4. The electrochemical response of the PPP, P3MET, PPI, CP3MET and CPPI films were investigated by cyc1ic voltammetry in a monomer−free solution with the films showing a typical electroactive response. Their optical properties were investigated by in situ UV−VIS absorption spectroscopy, a technique widely used aiming at understanding the electronic structure of most polymers. The UV−VIS spectra of the PPP, P3MET, PPI, CP3MET and CPPI films were obtained at different p−doping states, i.e., at different applied potential allowing us to calculate the π− π∗ transition of the films at their neutral, and polaronic and bipolaronic states. The structural characterization of the films was investigated by FT−Raman and FTIR spectroscopy, where it was verified that the films prepared by the electrooxidation of co−monomers showed only the bands that were typical of those ones observed in the spectra of the homopolymers, P3MET and PPI

Electrochemical biosensors fabricated by the immobilization of urease in polypyrrole films

A urease (Canavalia ensiformis DC.) foi fisicamente imobilizada em matrizes de polipirrol (PPI) com o objetivo de se detectar uréia em amostras padrão. A eletropolimerização do pirrol foi realizada por voltametria cíclica em uma faixa de potencial de -1,0 a 1,0 V vs. ECS em um meio aquoso contendo 0,2 mol/L de \'LI\'CL\'O IND.4\' e 0,1 mol/L de pirrol. Este procedimento permitiu também a imobilização da enzima na matriz polimérica em suas formas, urease purificada (comercial) e como extrato bruto obtido a partir do feijão de porco (Jack Bean), após a adição de 300 \'mü\'g/mL de urease purificada ou 100 \'mü\'L de extrato bruto de feijão de porco. A urease purificada possui 34.375 U/g de sólido e o extrato bruto, 13.000 UA/mL, valores obtidos por titrimetria. A presença da enzima imobilizada nos filmes de PPI foi verificada por voltametria cíclica, FTIR, microscopia eletrônica de varredura (MEV), microscopia de força atômica (AFM) e por uma microbalança de cristal de quartzo (MCQE). A atividade da enzima após a imobilização nos filmes de PPI foi confirmada pela presença de íons amônio em solução, que são formados como produtos da reação de hidrólise da uréia catalisada pela enzima. Como o transdutor influencia a eficiência e a sensibilidade do biossensor, dois métodos de transdução foram estudados: cronoamperometria, aplicando-se um potencial de -0,28 V durante 120 s em tampão fosfato pH 7,0 e a cronopotenciometria, aplicando-se uma corrente de 1,0 mA durante 120 s em tampão fosfato pH 7,0 variando-se a concentração de uréia. O principal objetivo deste trabalho foi avaliar a eficiência do biossensores para a detecção de uréia por meio de transdutores potenciométricos e amperométricos e depois comparar as eficiências dos filmes de PPI/urease purificada e PPI/extrato bruto como biosensores.Urease (Canavalia ensiformis DC.) was physically immobilized on polypyrrole (PPy) films aiming at detecting urea in standard samples. The electropolymerization of pyrrole was performed by cyclic voltammetry at a potential range from -1.0 to 1.0 V vs SCE in an aqueous medium containing \'LI\'CL\'O IND.4\' 0.2 mol/L and 0.1 mol/L pyrrole. This procedure also allowed us to immobilize the enzyme into the PPy matrix in forms, commercially purified and crude extract of urease obtained from Jack Bean (Canavalia ensiformis) after adding into the electropolymerization media 300 \'mü\'g/mL of purified urease or 100 \'mü\'L of crude extract. The urease solutions had units of active enzyme of 34.375 U/g (purified) and 13.000 UA/mL (crude extract), and the crude extract was obtained from Jack beans by titrimétric methods. The presence of urease immobilized into the PPy film was verified by cyclic voltammetry, FTIR, scanning electron microscopy (SEM), atomic force microscopy (AFM), and by electrochemical quartz crystal microbalance (EQCM) The activity of the enzyme after immobilizing into the PPy films was confirmed by the presence of ammonium ions in solution, since they are formed as catalytic products by urea hydrolysis reaction catalyzed enzyme. The transducer element influences the efficiency and sensitivity of the biosensor, and two transducer methods were studied: chronoamperometry, by applying a potential of -0.28 V during 120 s in buffer phosphate at pH 7.0 and chronopotentiometry, by applying a current of 1.0 mA during 120 s in buffer phosphate at pH 7.0 both after varying the urea concentration. Our main purpose was to evaluate the efficiency of the biosensors for detecting urea by means of potentiometric and amperometric transducers and then compare the efficiencies of PPY/purified urease e PPY/crude extract as biosensors

Electrosynthesis and optical characterization of poly(p-phenylene), polypyrrole and poly(p-phenylene)-polypyrrole films

Poly(p-phenylene) (PPP), polypyrrole (PPY), and poly(p-phenylene-pyrrole) (PPP-PPY) films were electrochemically synthesized in acetronitrile by cyclic voltammetry. For comparison purposes, the films were characterized by cyclic voltammetry in a monomer-free solution, and their optical responses were also obtained in the UV-VIS range of energy after varying the applied potentials. The absorbance spectra of the PPP-PPY film exhibited bands typically seen in the spectra of the homopolymers, PPP and PPY films, but better defined, intense, and related to reversible color transitions. Although it was not possible to confirm by using infrared and Raman spectroscopy that a copolymer was in fact obtained, the presence of both monomers, pyrrole and biphenyl, in the polymerization medium turned easier the process of film formation, yielding darker, more uniform, and rougher films as it was verified by photographic images and AFM (atomic force microscopy) images

Amperometric urea biosensors based on the entrapment of urease in polypyrrole films

Urease (Urs) was immobilized in electrochemically prepared polypyrrole (PPy) and the resulting films were characterized by cyclic voltammetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet visible spectroscopy (UV-VIS). The enzymatic activity of Urs entrapped in the PPy matrix was confirmed by the catalytic conversion of urea into carbon dioxide and ammonia, when urea was detected amperometrically at different concentrations in standard samples and commercial fertilizers. The PPy/Urs biosensors exhibited selectivity, a relatively high efficiency at urea concentrations below 3.0 mmol L-1, and a sensitivity to urea of 2.41 mu A cm(-2) mmol(-1) L (C) 2011 Elsevier Ltd. All rights reserved.FAPESPFAPESPCAPESCAPESCNPqCNP