Nancy Fabiana Ferreyra - Academia.edu (original) (raw)

Papers by Nancy Fabiana Ferreyra

Multi-walled carbon nanotubes (MWCNTs) dispersed in different polyelectrolytes were used to devel... more Multi-walled carbon nanotubes (MWCNTs) dispersed in different polyelectrolytes were used to develop electrochemical (bio)sensors by drop-coating of glassy carbon electrodes (GCEs). MWCNTs dispersed in polyhistidine were used for the quantification of uric acid or dopamine in the presence of large excess of ascorbic acid, and as platform to build glucose biosensors by self-assembling of glucose oxidase (GOx). The strong interaction of calf thymus-double stranded DNA (dsDNA) with the walls of bamboo-MWCNTs allowed us to obtain stable dispersions and modified GCEsfor sensitive dopamine sensing. The usefulness of GOx to disperse MWCNTs was also demonstrated. The enzyme not only disperses MWCNTs in a very efficient way, but also gives to them excellent biorecognition properties and allows to use it as platform for further immobilization of dsDNA. MWCNTs dispersed in polyethylenimine allowed the development of stable and robust electrochemical sensors for dopamine in complex mixtures and ...

SOUTHERN JOURNAL OF SCIENCES

Background: A crucial aspect of electrochemical enzymatic biosensor development is the immobiliza... more Background: A crucial aspect of electrochemical enzymatic biosensor development is the immobilization of the enzymes, as it directly influences the sensitivity of the bioelectrode. Among the different methods used to incorporate enzymes on the surface of the transducers, layer-by-layer (LbL) self-assembly based on electrostatic interaction with polyelectrolytes of opposite charge stands out due to its simplicity and reproducibility. Aims: The aim of the work was to develop an electrochemical glucose biosensor by LbL assembly of a new functionalized chitosan polycation and the enzyme glucose oxidase (GOx). Methods: Chitosan was chemically functionalized with glucose by the Maillard reaction. The resulting polycation, named G-Chit, is soluble in the medium compatible with the enzyme. The bioelectrode was obtained by alternating adsorption of G-Chit and GOx onto carbon paste electrodes. By selecting the number of bilayer of G-Chit/GOX, the enzyme concentration, and the pH, the electroa...

Surfaces and Interfaces, Jun 1, 2022

Colloids and Surfaces B: Biointerfaces, 2017

The specificity of carbohydrate-protein interaction is a key factor in many biological processes ... more The specificity of carbohydrate-protein interaction is a key factor in many biological processes and it is the foundation of technologies using glycoliposomes in drug delivery. The incorporation of glycolipids in vesicles is expected to increase their specificity toward particular targets such as lectins; however, the degree of exposure of the carbohydrate moiety at the liposome surface is a crucial parameter to be considered in the interaction. Herein we report the synthesis of mannose derivatives with one or two hydrophobic chains of different length, designed with the purpose of modifying the degree of exposure of the mannose when they were incorporated into liposomes. The interaction of glycovesicles with Con A was studied using: (i) agglutination assays; measured by dynamic laser light scattering (DLS); (ii) time resolved fluorescence methods and (iii) surface plasmon resonance (SPR) kinetic measurements. DLS data showed that an increase in hydrophobic chain length promotes a decrease of liposomes hydrodynamic radius. A longer hydrocarbon chain favors a deeper insertion into the bilayer and mannose moiety results less exposed at the surface to interact with lectin. Fluorescence experiments showed changes in the structure of glycovesicles due to the interaction with the protein. From SPR measurements the kinetic and equilibrium constants associated to the interaction of ConA with the different glycolipid synthetized were determined. The combination of SPR and fluorescence techniques allowed to study the interaction of Con A with mannosyl glycovesicles at three levels: at the surface, at the interface and deeper into the bilayer.

Journal of Electroanalytical Chemistry, 2000

The electroreduction of methyl viologen (MV) in the presence of nitrite was studied by cyclic vol... more The electroreduction of methyl viologen (MV) in the presence of nitrite was studied by cyclic voltammetry. A catalytic wave for the reduction of MV 2 + was observed at −0.740 V for which an EC catalytic mechanism is proposed. The rate constant for this chemical reaction under pseudo-first-order conditions, evaluated using working curves, was employed in the simulation of the voltammetric response. The second-order rate constant was also evaluated. Influences of the reaction at − 0.800 V on enzymatic electrodes employing nitrate reductase (NR) and MV + as mediator were also analysed by chronoamperometry.

Bioelectrochemistry, 2004

The enzyme-catalysed reduction of nitrate was studied utilising Aspergillus niger nitrate reducta... more The enzyme-catalysed reduction of nitrate was studied utilising Aspergillus niger nitrate reductase (NR) and phenosafranin in solution as the enzyme regenerator, working at lower potentials than that of the more common methyl viologen mediator. Cyclic voltammograms when enzyme, phenosafranin and substrate were together put in evidence the enzyme-catalysed reduction of nitrate, although with a relatively slow kinetics. From slope values not dependent on mediator concentration, the apparent Michaelis-Menten constant was evaluated. Analytical parameters for the enzyme-modified electrode in the presence of phenosafranin for the determination of nitrate content in water were assessed, including a recovery assay for nitrate added to a river water sample. The stability of the electrode was checked.

Proceedings of the SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 2021 INTERNATIONAL VIRTUAL CONFERENCE, 2022

Multilayer films made of glucose-functionalized chitosan (G-Chit) and glucose oxidase (GOx) were ... more Multilayer films made of glucose-functionalized chitosan (G-Chit) and glucose oxidase (GOx) were built by layer-by-layer self-assembly technique onto carbon paste electrodes (CPE). The obtained bioelectrodes were characterized by cyclic voltammetry and chronoamperometry. Results indicated that catalytic response increases with the number of bilayers G-Chit/GOx and the enzyme concentration obtaining the best responses for 3 bilayers and 2 mg ml-1, respectively. The effect of pH on the bioelectrode response was also investigated, it was found that the optimal working value is 7.0. Under optimized experimental conditions, the biosensor exhibits a sensitivity of (0.81 ± 0.03) µA mM-1 in a glucose concentration range 0.18 to 1.75 mM. The analytical response of the biosensor was tested in milk samples with negligible matrix effects. Results show that G-Chti appears promising for the immobilization of enzymes.

Journal of Electroanalytical Chemistry, 2020

Electrochimica Acta, 2016

The immobilization of three amino-b-cyclodextrin derivatives on gold surfaces via different botto... more The immobilization of three amino-b-cyclodextrin derivatives on gold surfaces via different bottom-up approaches was evaluated using cyclic voltammetry and surface plasmon resonance. Direct adsorption on gold and covalent attachment via amide bond formation with carboxylic groups of both the selfassembled monolayer of 4-mercapto benzoic acid (4-MBA) and the electrografted diazonium salt synthesized in situ from 4-amino benzoic acid (4-ABA) were tested. Amino b-CD with 1, 2 or 7 amine groups on the primary rim were used. The influence of the immobilization methodologies on the electrochemical properties of the resulting surfaces was studied using hydroquinone and ferricyanide as redox probes. The results indicate that the surface coverage of the molecules as well as their organization at the gold substrate depends on the number of amine groups on the primary rim of b-CD. A higher coverage via direct adsorption is obtained using the 7-amino groups derivative, while the highest coverage is reached with the 2-amino groups derivative via covalent attachment at diazonium salt electrografted surfaces. A critical discussion about the influence of different strategies used for the immobilization and the number of terminal amine groups on the b-CD structure is performed.

Advances in Electrochemical Sciences and Engineering, 2016

On the basis of the number of concentric walls, carbon nanotubes (CNTs) can be divided into singl... more On the basis of the number of concentric walls, carbon nanotubes (CNTs) can be divided into single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). In the last few years, the noncovalent treatment of CNTs has been widely used in the preparation of both aqueous and organic solutions to obtain a high weight fraction of individual nanotubes or small aggregates of dispersed nanotubes. Noncovalent functionalization of nanotubes is of particular interest, because it improves solubility and processability without compromising their physical properties. Polymers have allowed the successful dispersion of CNTs. This chapter describes the electrochemical behavior and characteristics of modified electrodes with the most reported and relevant CNT dispersions mediated by different polymers, ionic liquids (ILs), and small molecules. The toxicity of CNTs is a critical aspect that requires important research to know about the uptake of CNTs by living cells and their distribution in the environment.Fil: Primo, Emiliano Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gutierrez, Fabiana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Rubianes, María Dolores. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Ferreyra, Nancy Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Rodriguez, Marcela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Pedano, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gasnier, Aurelien. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gutierrez, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Eguílaz Rubio, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Dalmasso, Pablo Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Luque, Guillermina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Bollo, Soledad. Universidad de Chile; ChileFil: Parrado, Concepción. Universidad Complutense de Madrid; EspañaFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad…

Desde el primer diseño en 1962, los biosensores electroquímicos han demostrado una importante evo... more Desde el primer diseño en 1962, los biosensores electroquímicos han demostrado una importante evolución que los ha convertido en una alternativa muy interesante por sus ventajas de miniaturización, bajo costo, alta sensibilidad y portabilidad, permitiendo una eficiente asociación a nivel molecular de eventos de reconocimiento biológico y procesos electrónicos de transducción de señal para la cuantificación de analitos de interés clínico, ambiental y toxicológico. El uso de materiales a nanoescala (nanopartículas, nanoalambres, nanocilindros, nanoagujas, nanocintas, entre otras) para el diseño de biosensores electroquímicos ha tenido un crecimiento explosivo en los últimos cinco años. A diferencia de los materiales masivos, se puede ampliar significativamente el espectro de funcionalizaciones con los diseños basados en nanoestructuras, logrando notables mejoras en las señales analíticas, y la detección rápida, sensible y libre de marcadores. En esta presentación se discutirán los asp...

In recent years, there has been a marked interest in the study and use of chemical, electronic, o... more In recent years, there has been a marked interest in the study and use of chemical, electronic, optical and magnetic properties of metal nanoparticles (Nps) [1]. Among the highlights include research concerning the synthesis and characterization of physical and chemical properties [2]; application in nanostructures [3], clinical diagnosis, as markers for biomolecules [4] and more recently in therapeutic applications such as drug liberation and radiotherapy or hiperthermic treatments [5]. Moreover, the excellent electronic properties of the metal Nps make them very attractive for the development of electrical devices [6] and for its applications in molecular catalysis [7] and in sensors and biosensors [8-10]. The incorporation of Nps in organized molecular structures is crucial to develop new materials technologically useful. The Nps assembly in bi-or three-dimensional structures was described through different methodologies, between them the electrostatic adsorption with polyelectro...

La Resonancia de Plasmón Superficial (SPR) es una técnica espectroscópica, no invasiva, sensible ... more La Resonancia de Plasmón Superficial (SPR) es una técnica espectroscópica, no invasiva, sensible a cambios en el espesor o en el índice de refracción de biomateriales o películas adsorbidas en una interfase, entre una película delgada de oro (sustrato) y el medio ambiente (electrolito). Permite estudiar procesos de adsorción (formación de autoensamblados) o interacciones específicas (hibridación, antígenoanticuerpo, receptor-ligando), en tiempo real sin la necesidad de emplear marcadores. El objetivo de este trabajo fue estudiar la adsorción de cada componente durante la construcción de una estructura autoensamblada formada por el policatión polietilenimina (Pei), nanopartículas de oro (Nps) y la enzima glucosa oxidasa (Gox) sobre sustratos de oro modificados con el tiol 3-mercapto1-propansulfónico (MPS). Para monitorear la construcción de estas estructuras, se evaluó la cinética de adsorción midiendo el ángulo de SPR (θ) en función del tiempo, Δθ para cada capa adsorbida y las vari...

Resumen En este trabajo se caracterizaron la estructura y propiedades de multicapas autoensamblad... more Resumen En este trabajo se caracterizaron la estructura y propiedades de multicapas autoensambladas de nanopartículas (Nps) de oro con el policatión quitosano (CHI) mediante métodos ópticos (espectrofotometría y elipsometría in-situ) y electroquímicos (espectroscopía de impedancia electroquímica, EIE). Se analizó el efecto del tiempo de adsorción de las Nps en las propiedades ópticas y espesor de la estructura. Los resultados de EIE en presencia de [Fe(CN) 6 ] 3-/4-mostraron un incremento de la resistencia a la transferencia de carga al aumentar el tiempo de adsorción de Nps debida a una mayor repulsión electrostática entre el analito y la superficie modificada. Se incorporó la enzima glucosa oxidasa (GOD) en dichas estructuras y se evaluó la variación de la respuesta a glucosa. Se compararon resultados logrados en ausencia y en presencia de Nps, obteniéndose una mayor sensibilidad en el segundo caso con un incremento lineal al adsorber mayor número de capas de Nps. Palabras clave: ...

Sensors and Actuators B: Chemical, 2015

Electroanalysis, 2014

This work is focused on the critical analysis of the influence of the experimental conditions on ... more This work is focused on the critical analysis of the influence of the experimental conditions on the efficient dispersion of hollow-type (hMWCNT) and bamboolike (bMWCNT) multiwall carbon nanotubes with polyethyleneimine (PEI). Spectroscopic and electrochemical studies demonstrated that the adequate combination of optimized ultracavitation and centrifugation is essential to obtain successful dispersions. The selected conditions were 1.0 mg mL À1 hMWCNT in 3.0 mg mL À1 PEI sonicated with a sonicator probe operating at 50 % of amplitude for 300 s and centrifuged at 9000 rpm for 15 min. Bamboo-like multiwall carbon nanotubes were faster exfoliated and glassy carbon electrodes (GCE) modified with the resulting dispersion allowed the amperometric detection of hydrogen peroxide at lower potentials (0.100 V) with a detection limit of 5.5 mM.

Electroanalysis, 2014

ABSTRACT This work reports the advantages of using glassy carbon electrodes modified with multiwa... more ABSTRACT This work reports the advantages of using glassy carbon electrodes modified with multiwall carbon nanotubes (MWCNT) dispersed in polyethylenimine (PEI). The presence of MWCNTs wrapped by PEI largely facilitated the strong adsorption of uric acid (UA) and allowed its highly sensitive and selective quantification even in the presence of high excess of ascorbic acid. The selected conditions for the electrochemical sensing were 5 s accumulation at −0.300 V under stirring and quantification in a 0.050 M phosphate buffer solution pH 7.40 by differential pulse voltammetry adsorptive-stripping after medium exchange. The platform allowed the successful application in the quantification of UA in urine.

Electrochimica Acta, 2014

Self-assembled multilayers of quaternized chitosan (QCHI) and gold nanoparticles (AuNPs) were bui... more Self-assembled multilayers of quaternized chitosan (QCHI) and gold nanoparticles (AuNPs) were built up on quartz and gold substrates. To evaluate the effect of the surface coverage of AuNPs on the structural, optical and electrochemical properties of multilayers prepared with different AuNPs adsorption time were compared. UV-Vis and AFM characterization indicated that AuNPs in each bilayer are spatially separated, and interparticle interactions are mainly produced between bilayers. The complex refractive index and thickness of the QCHI-AuNPs multilayers were properly determined using an anisotropic single layer model. The optical constants obtained were quite different from those of bulk gold, and their values depend on the coverage of AuNPs. The thickness per bilayer of the structures present a progressive increase as AuNP's coverage augments, reaching a value close to the nominal AuNPs diameter after 60 min of adsorption. These results indicate that the interpenetration of bilayers in the structure depends on the surface concentration of AuNPs. The charge transport through the QCHI-AuNPs film was studied using different redox probes. The effects of the adsorption time of AuNPs and the number of bilayers (n) of the structure on the charge transfer rate constants, k ct , were analyzed. The incorporation of AuNPs in the structure produces an increase of k ct , as the adsorption time of AuNPs rise. In addition, the values of k ct were independent of n, in the interval studied (up to n = 5), suggesting that the electronic communication in the multilayered structure was mediated by the AuNPs.

Talanta, 2007

This work reports on the analytical performance of composites obtained by dispersing copper micro... more This work reports on the analytical performance of composites obtained by dispersing copper microparticles and multi-wall carbon nanotubes within a mineral oil binder (CNTPE-Cu) for the determination of amino acids and albumin. The strong complexing activity of amino acids towards copper makes possible an important improvement in the sensitivity for the determination of amino acids and albumin. This new electrode permits the highly sensitive amperometric detection of amino acids, even the non-electroactive ones, at very low potentials (0.000 V) and physiological pH (phosphate buffer solution pH 7.40). The response of the electrode is highly dependent on the amount of copper, demonstrating the crucial role of the metal in the analytical performance of the sensor. The best analytical performance is obtained for the electrode containing 6.0% (w/w) copper. The resulting sensor shows a fast response (7 s) and a sensitivity that depends on the nature of the amino acid. The electrode surface demonstrates an excellent resistance to surface fouling, with R.S.D. of 4% for the sensitivities of 10 successive calibration plots. Albumin is determined with CNTPE-Cu using a protocol based on the accumulation of the protein for 10 min at −0.100 V, followed by the square-wave voltammetric analysis. The quantification of albumin concentration in lyophilized control serum gives excellent agreement with the classical spectrophotometric methodology and with the value informed for the supplier.

Multi-walled carbon nanotubes (MWCNTs) dispersed in different polyelectrolytes were used to devel... more Multi-walled carbon nanotubes (MWCNTs) dispersed in different polyelectrolytes were used to develop electrochemical (bio)sensors by drop-coating of glassy carbon electrodes (GCEs). MWCNTs dispersed in polyhistidine were used for the quantification of uric acid or dopamine in the presence of large excess of ascorbic acid, and as platform to build glucose biosensors by self-assembling of glucose oxidase (GOx). The strong interaction of calf thymus-double stranded DNA (dsDNA) with the walls of bamboo-MWCNTs allowed us to obtain stable dispersions and modified GCEsfor sensitive dopamine sensing. The usefulness of GOx to disperse MWCNTs was also demonstrated. The enzyme not only disperses MWCNTs in a very efficient way, but also gives to them excellent biorecognition properties and allows to use it as platform for further immobilization of dsDNA. MWCNTs dispersed in polyethylenimine allowed the development of stable and robust electrochemical sensors for dopamine in complex mixtures and ...

SOUTHERN JOURNAL OF SCIENCES

Background: A crucial aspect of electrochemical enzymatic biosensor development is the immobiliza... more Background: A crucial aspect of electrochemical enzymatic biosensor development is the immobilization of the enzymes, as it directly influences the sensitivity of the bioelectrode. Among the different methods used to incorporate enzymes on the surface of the transducers, layer-by-layer (LbL) self-assembly based on electrostatic interaction with polyelectrolytes of opposite charge stands out due to its simplicity and reproducibility. Aims: The aim of the work was to develop an electrochemical glucose biosensor by LbL assembly of a new functionalized chitosan polycation and the enzyme glucose oxidase (GOx). Methods: Chitosan was chemically functionalized with glucose by the Maillard reaction. The resulting polycation, named G-Chit, is soluble in the medium compatible with the enzyme. The bioelectrode was obtained by alternating adsorption of G-Chit and GOx onto carbon paste electrodes. By selecting the number of bilayer of G-Chit/GOX, the enzyme concentration, and the pH, the electroa...

Surfaces and Interfaces, Jun 1, 2022

Colloids and Surfaces B: Biointerfaces, 2017

The specificity of carbohydrate-protein interaction is a key factor in many biological processes ... more The specificity of carbohydrate-protein interaction is a key factor in many biological processes and it is the foundation of technologies using glycoliposomes in drug delivery. The incorporation of glycolipids in vesicles is expected to increase their specificity toward particular targets such as lectins; however, the degree of exposure of the carbohydrate moiety at the liposome surface is a crucial parameter to be considered in the interaction. Herein we report the synthesis of mannose derivatives with one or two hydrophobic chains of different length, designed with the purpose of modifying the degree of exposure of the mannose when they were incorporated into liposomes. The interaction of glycovesicles with Con A was studied using: (i) agglutination assays; measured by dynamic laser light scattering (DLS); (ii) time resolved fluorescence methods and (iii) surface plasmon resonance (SPR) kinetic measurements. DLS data showed that an increase in hydrophobic chain length promotes a decrease of liposomes hydrodynamic radius. A longer hydrocarbon chain favors a deeper insertion into the bilayer and mannose moiety results less exposed at the surface to interact with lectin. Fluorescence experiments showed changes in the structure of glycovesicles due to the interaction with the protein. From SPR measurements the kinetic and equilibrium constants associated to the interaction of ConA with the different glycolipid synthetized were determined. The combination of SPR and fluorescence techniques allowed to study the interaction of Con A with mannosyl glycovesicles at three levels: at the surface, at the interface and deeper into the bilayer.

Journal of Electroanalytical Chemistry, 2000

The electroreduction of methyl viologen (MV) in the presence of nitrite was studied by cyclic vol... more The electroreduction of methyl viologen (MV) in the presence of nitrite was studied by cyclic voltammetry. A catalytic wave for the reduction of MV 2 + was observed at −0.740 V for which an EC catalytic mechanism is proposed. The rate constant for this chemical reaction under pseudo-first-order conditions, evaluated using working curves, was employed in the simulation of the voltammetric response. The second-order rate constant was also evaluated. Influences of the reaction at − 0.800 V on enzymatic electrodes employing nitrate reductase (NR) and MV + as mediator were also analysed by chronoamperometry.

Bioelectrochemistry, 2004

The enzyme-catalysed reduction of nitrate was studied utilising Aspergillus niger nitrate reducta... more The enzyme-catalysed reduction of nitrate was studied utilising Aspergillus niger nitrate reductase (NR) and phenosafranin in solution as the enzyme regenerator, working at lower potentials than that of the more common methyl viologen mediator. Cyclic voltammograms when enzyme, phenosafranin and substrate were together put in evidence the enzyme-catalysed reduction of nitrate, although with a relatively slow kinetics. From slope values not dependent on mediator concentration, the apparent Michaelis-Menten constant was evaluated. Analytical parameters for the enzyme-modified electrode in the presence of phenosafranin for the determination of nitrate content in water were assessed, including a recovery assay for nitrate added to a river water sample. The stability of the electrode was checked.

Proceedings of the SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 2021 INTERNATIONAL VIRTUAL CONFERENCE, 2022

Multilayer films made of glucose-functionalized chitosan (G-Chit) and glucose oxidase (GOx) were ... more Multilayer films made of glucose-functionalized chitosan (G-Chit) and glucose oxidase (GOx) were built by layer-by-layer self-assembly technique onto carbon paste electrodes (CPE). The obtained bioelectrodes were characterized by cyclic voltammetry and chronoamperometry. Results indicated that catalytic response increases with the number of bilayers G-Chit/GOx and the enzyme concentration obtaining the best responses for 3 bilayers and 2 mg ml-1, respectively. The effect of pH on the bioelectrode response was also investigated, it was found that the optimal working value is 7.0. Under optimized experimental conditions, the biosensor exhibits a sensitivity of (0.81 ± 0.03) µA mM-1 in a glucose concentration range 0.18 to 1.75 mM. The analytical response of the biosensor was tested in milk samples with negligible matrix effects. Results show that G-Chti appears promising for the immobilization of enzymes.

Journal of Electroanalytical Chemistry, 2020

Electrochimica Acta, 2016

The immobilization of three amino-b-cyclodextrin derivatives on gold surfaces via different botto... more The immobilization of three amino-b-cyclodextrin derivatives on gold surfaces via different bottom-up approaches was evaluated using cyclic voltammetry and surface plasmon resonance. Direct adsorption on gold and covalent attachment via amide bond formation with carboxylic groups of both the selfassembled monolayer of 4-mercapto benzoic acid (4-MBA) and the electrografted diazonium salt synthesized in situ from 4-amino benzoic acid (4-ABA) were tested. Amino b-CD with 1, 2 or 7 amine groups on the primary rim were used. The influence of the immobilization methodologies on the electrochemical properties of the resulting surfaces was studied using hydroquinone and ferricyanide as redox probes. The results indicate that the surface coverage of the molecules as well as their organization at the gold substrate depends on the number of amine groups on the primary rim of b-CD. A higher coverage via direct adsorption is obtained using the 7-amino groups derivative, while the highest coverage is reached with the 2-amino groups derivative via covalent attachment at diazonium salt electrografted surfaces. A critical discussion about the influence of different strategies used for the immobilization and the number of terminal amine groups on the b-CD structure is performed.

Advances in Electrochemical Sciences and Engineering, 2016

On the basis of the number of concentric walls, carbon nanotubes (CNTs) can be divided into singl... more On the basis of the number of concentric walls, carbon nanotubes (CNTs) can be divided into single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). In the last few years, the noncovalent treatment of CNTs has been widely used in the preparation of both aqueous and organic solutions to obtain a high weight fraction of individual nanotubes or small aggregates of dispersed nanotubes. Noncovalent functionalization of nanotubes is of particular interest, because it improves solubility and processability without compromising their physical properties. Polymers have allowed the successful dispersion of CNTs. This chapter describes the electrochemical behavior and characteristics of modified electrodes with the most reported and relevant CNT dispersions mediated by different polymers, ionic liquids (ILs), and small molecules. The toxicity of CNTs is a critical aspect that requires important research to know about the uptake of CNTs by living cells and their distribution in the environment.Fil: Primo, Emiliano Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gutierrez, Fabiana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Rubianes, María Dolores. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Ferreyra, Nancy Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Rodriguez, Marcela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Pedano, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gasnier, Aurelien. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Gutierrez, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Eguílaz Rubio, Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Dalmasso, Pablo Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Luque, Guillermina Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Bollo, Soledad. Universidad de Chile; ChileFil: Parrado, Concepción. Universidad Complutense de Madrid; EspañaFil: Rivas, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad…

Desde el primer diseño en 1962, los biosensores electroquímicos han demostrado una importante evo... more Desde el primer diseño en 1962, los biosensores electroquímicos han demostrado una importante evolución que los ha convertido en una alternativa muy interesante por sus ventajas de miniaturización, bajo costo, alta sensibilidad y portabilidad, permitiendo una eficiente asociación a nivel molecular de eventos de reconocimiento biológico y procesos electrónicos de transducción de señal para la cuantificación de analitos de interés clínico, ambiental y toxicológico. El uso de materiales a nanoescala (nanopartículas, nanoalambres, nanocilindros, nanoagujas, nanocintas, entre otras) para el diseño de biosensores electroquímicos ha tenido un crecimiento explosivo en los últimos cinco años. A diferencia de los materiales masivos, se puede ampliar significativamente el espectro de funcionalizaciones con los diseños basados en nanoestructuras, logrando notables mejoras en las señales analíticas, y la detección rápida, sensible y libre de marcadores. En esta presentación se discutirán los asp...

In recent years, there has been a marked interest in the study and use of chemical, electronic, o... more In recent years, there has been a marked interest in the study and use of chemical, electronic, optical and magnetic properties of metal nanoparticles (Nps) [1]. Among the highlights include research concerning the synthesis and characterization of physical and chemical properties [2]; application in nanostructures [3], clinical diagnosis, as markers for biomolecules [4] and more recently in therapeutic applications such as drug liberation and radiotherapy or hiperthermic treatments [5]. Moreover, the excellent electronic properties of the metal Nps make them very attractive for the development of electrical devices [6] and for its applications in molecular catalysis [7] and in sensors and biosensors [8-10]. The incorporation of Nps in organized molecular structures is crucial to develop new materials technologically useful. The Nps assembly in bi-or three-dimensional structures was described through different methodologies, between them the electrostatic adsorption with polyelectro...

La Resonancia de Plasmón Superficial (SPR) es una técnica espectroscópica, no invasiva, sensible ... more La Resonancia de Plasmón Superficial (SPR) es una técnica espectroscópica, no invasiva, sensible a cambios en el espesor o en el índice de refracción de biomateriales o películas adsorbidas en una interfase, entre una película delgada de oro (sustrato) y el medio ambiente (electrolito). Permite estudiar procesos de adsorción (formación de autoensamblados) o interacciones específicas (hibridación, antígenoanticuerpo, receptor-ligando), en tiempo real sin la necesidad de emplear marcadores. El objetivo de este trabajo fue estudiar la adsorción de cada componente durante la construcción de una estructura autoensamblada formada por el policatión polietilenimina (Pei), nanopartículas de oro (Nps) y la enzima glucosa oxidasa (Gox) sobre sustratos de oro modificados con el tiol 3-mercapto1-propansulfónico (MPS). Para monitorear la construcción de estas estructuras, se evaluó la cinética de adsorción midiendo el ángulo de SPR (θ) en función del tiempo, Δθ para cada capa adsorbida y las vari...

Resumen En este trabajo se caracterizaron la estructura y propiedades de multicapas autoensamblad... more Resumen En este trabajo se caracterizaron la estructura y propiedades de multicapas autoensambladas de nanopartículas (Nps) de oro con el policatión quitosano (CHI) mediante métodos ópticos (espectrofotometría y elipsometría in-situ) y electroquímicos (espectroscopía de impedancia electroquímica, EIE). Se analizó el efecto del tiempo de adsorción de las Nps en las propiedades ópticas y espesor de la estructura. Los resultados de EIE en presencia de [Fe(CN) 6 ] 3-/4-mostraron un incremento de la resistencia a la transferencia de carga al aumentar el tiempo de adsorción de Nps debida a una mayor repulsión electrostática entre el analito y la superficie modificada. Se incorporó la enzima glucosa oxidasa (GOD) en dichas estructuras y se evaluó la variación de la respuesta a glucosa. Se compararon resultados logrados en ausencia y en presencia de Nps, obteniéndose una mayor sensibilidad en el segundo caso con un incremento lineal al adsorber mayor número de capas de Nps. Palabras clave: ...

Sensors and Actuators B: Chemical, 2015

Electroanalysis, 2014

This work is focused on the critical analysis of the influence of the experimental conditions on ... more This work is focused on the critical analysis of the influence of the experimental conditions on the efficient dispersion of hollow-type (hMWCNT) and bamboolike (bMWCNT) multiwall carbon nanotubes with polyethyleneimine (PEI). Spectroscopic and electrochemical studies demonstrated that the adequate combination of optimized ultracavitation and centrifugation is essential to obtain successful dispersions. The selected conditions were 1.0 mg mL À1 hMWCNT in 3.0 mg mL À1 PEI sonicated with a sonicator probe operating at 50 % of amplitude for 300 s and centrifuged at 9000 rpm for 15 min. Bamboo-like multiwall carbon nanotubes were faster exfoliated and glassy carbon electrodes (GCE) modified with the resulting dispersion allowed the amperometric detection of hydrogen peroxide at lower potentials (0.100 V) with a detection limit of 5.5 mM.

Electroanalysis, 2014

ABSTRACT This work reports the advantages of using glassy carbon electrodes modified with multiwa... more ABSTRACT This work reports the advantages of using glassy carbon electrodes modified with multiwall carbon nanotubes (MWCNT) dispersed in polyethylenimine (PEI). The presence of MWCNTs wrapped by PEI largely facilitated the strong adsorption of uric acid (UA) and allowed its highly sensitive and selective quantification even in the presence of high excess of ascorbic acid. The selected conditions for the electrochemical sensing were 5 s accumulation at −0.300 V under stirring and quantification in a 0.050 M phosphate buffer solution pH 7.40 by differential pulse voltammetry adsorptive-stripping after medium exchange. The platform allowed the successful application in the quantification of UA in urine.

Electrochimica Acta, 2014

Self-assembled multilayers of quaternized chitosan (QCHI) and gold nanoparticles (AuNPs) were bui... more Self-assembled multilayers of quaternized chitosan (QCHI) and gold nanoparticles (AuNPs) were built up on quartz and gold substrates. To evaluate the effect of the surface coverage of AuNPs on the structural, optical and electrochemical properties of multilayers prepared with different AuNPs adsorption time were compared. UV-Vis and AFM characterization indicated that AuNPs in each bilayer are spatially separated, and interparticle interactions are mainly produced between bilayers. The complex refractive index and thickness of the QCHI-AuNPs multilayers were properly determined using an anisotropic single layer model. The optical constants obtained were quite different from those of bulk gold, and their values depend on the coverage of AuNPs. The thickness per bilayer of the structures present a progressive increase as AuNP's coverage augments, reaching a value close to the nominal AuNPs diameter after 60 min of adsorption. These results indicate that the interpenetration of bilayers in the structure depends on the surface concentration of AuNPs. The charge transport through the QCHI-AuNPs film was studied using different redox probes. The effects of the adsorption time of AuNPs and the number of bilayers (n) of the structure on the charge transfer rate constants, k ct , were analyzed. The incorporation of AuNPs in the structure produces an increase of k ct , as the adsorption time of AuNPs rise. In addition, the values of k ct were independent of n, in the interval studied (up to n = 5), suggesting that the electronic communication in the multilayered structure was mediated by the AuNPs.

Talanta, 2007

This work reports on the analytical performance of composites obtained by dispersing copper micro... more This work reports on the analytical performance of composites obtained by dispersing copper microparticles and multi-wall carbon nanotubes within a mineral oil binder (CNTPE-Cu) for the determination of amino acids and albumin. The strong complexing activity of amino acids towards copper makes possible an important improvement in the sensitivity for the determination of amino acids and albumin. This new electrode permits the highly sensitive amperometric detection of amino acids, even the non-electroactive ones, at very low potentials (0.000 V) and physiological pH (phosphate buffer solution pH 7.40). The response of the electrode is highly dependent on the amount of copper, demonstrating the crucial role of the metal in the analytical performance of the sensor. The best analytical performance is obtained for the electrode containing 6.0% (w/w) copper. The resulting sensor shows a fast response (7 s) and a sensitivity that depends on the nature of the amino acid. The electrode surface demonstrates an excellent resistance to surface fouling, with R.S.D. of 4% for the sensitivities of 10 successive calibration plots. Albumin is determined with CNTPE-Cu using a protocol based on the accumulation of the protein for 10 min at −0.100 V, followed by the square-wave voltammetric analysis. The quantification of albumin concentration in lyophilized control serum gives excellent agreement with the classical spectrophotometric methodology and with the value informed for the supplier.