Sánchez, B.; Vega, D.; Rodriguez, A.; Bragos, R.; Marco, M.P.; Valera, E. Sensors and actuators B. Chemical Vol. 203, p. 444-451 DOI: 10.1016/j.snb.2014.06.139 Data de publicació: 2014-11-01 Article en revista
A magnetic interdigitated microelectrode (m-ID mu E) has been developed, characterized and evaluated. In order to demonstrate the potential use of these electrodes in the biosensors field, impedimetric measurements of bovine serum albumin (BSA) biofunctionalized magnetic mu-particles (BSAMP) were performed. Thanks to their magnetic capabilities and to the use of magnetic mu-particles, the developed electrodes were successfully regenerated and could be reused several times. The classical stepped-sine impedance spectroscopy (IS) technique and the state-of-art frequency response analyzer (FRA) multisine IS method based on the local polynomial method (LPM) were used as measurement techniques. The significant reduction of measuring time and accuracy of the multisine IS LPM-based technique reveals a promising performance for fast and accurate real-time on-line screening applications. (C) 2014 Elsevier B.V. All rights reserved.
Valera, E.; Ramón, J.; Barranco, A.; Alfaro, B.; Sánchez-Baeza, F.; Marco, M.P.; Rodriguez, A. Food chemistry Vol. 122, p. 888-894 DOI: 10.1016/j.foodchem.2010.03.030 Data de publicació: 2010 Article en revista
The potential of a conductimetric immunosensor to detect residual amounts of atrazine in a complexv matrix, such as red wine, is evaluated. The immunosensor presented is based on interdigitated μ-electrodes (IDμEs), immunoreagents specifically developed to detect atrazine, and antibodies labelled with gold nanoparticles. Due to the amplification of the conductive signal, produced by the presence of the gold particles, atrazine can be detected using simple and inexpensive direct current (DC) measurements.
Then, sensors response is related to the atrazine concentration in the sample. Likewise, the presence of gold particles generates an increase in the intensity of the electric field between the electrodes. The time for assay completion, for 48 samples, was 5 h. Nevertheless, during the first hour (devoted to the incubation
assays), the number of samples could be increased without prejudice the assay duration. Sensor responses obtained using red wine samples are compared with results obtained using buffer solutions. As a consequence, the strong matrix effect related to red wine samples has been identified as a non-specific increase of the current intensity through the device.
The limits of detection (LODs) obtained are far below the Maximum Residue Level (50 μg kg-1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products. This opens the door to commercial sensors of simple manipulation, transportable and economics.
The present paper describes a simple and low-cost method for the fabrication of mechanically flexible interdigitated μ-electrodes (FIDμEs) and its application as immunosensor.
FIDμEs consist of two coplanar non-passivated interdigitated metallic μ-electrodes supported on a flexible transparent substrate, polyethylene naphthalate (PEN). Bioreagents deposition on PEN substrates becomes possible by depositing SiO2 on the electrodes surface (fingers and inter-digits space).
These FIDμEs were successfully applied for the development of a selective conductimetric immunosensor for the quantification of atrazine residues. The immunosensor has been demonstrated for detection of small amounts of atrazine, thanks to the use of immunoreagents specifically developed to detect this pesticide.
The detection method applied is based on the use of antibodies labelled with gold nanoparticles. The presence of these particles amplifies the conductive signal; hence the immunosensor response was quantified using simple and inexpensive DC measurements.
Immunochemical detection of the concentrations of atrazine is achieved by a competitive reaction which occurs before the inclusion of the labelled antibodies.
The immunosensor shows limits of detection in the order of 2–3 μg L−1, far below the maximum residue level (50 μg kg−1) established by EU for residues of atrazine as herbicide in the wine grapes and other foodstuff products.
This contribution describes the development of an impedimetric immunosensor for atrazine detection. This
immunosensor is based on the use of interdigitated metallic
μ-electrodes (IDμEs) The method described in this work does not use any redox mediator and relies on the direct detection of
immunochemical competitive reaction between the pesticide and
a haptenized-protein immobilized on interdigitated
μ-electrodes for the specific antibody.
The immunoreagents used were specifically developed to detect atrazine. The immunochemical detection of this pesticide is achieved without using any label. The immunosensor shows a limit of detection of 8.34±1.37 μg L-1, witch is lower than the Maximun Residue Level (MRL) (50μg L-1)established by EU (European Union)for residues of atrazine as herbicide in the wine grapes and other foodstuff products.
Two novel immunosensors, one impedimetric and other one conductimetric, for atrazine detection in red wine samples have been developed. Impedimetric immunosensor is based on an array of interdigitated μ-
electrodes (IDμEs) and bioreagents specifically developed to detect this pesticide. Conductimetric immunosensor incorporates additionally gold nanoparticles. Bioreagents were covalently immobilized on the surface of the electrodes (interdigital space). In both cases the biochemical determination of atrazine is
possible without any redox mediator. For the case of the impedimetric immunosensor, the detection method is based on impedimetric measurements (in a wide range of frequencies), whereas in the case of the
conductimetric immunosensor the detection method is based on conductimetric measurements (DC measurements).The potential of the impedimetric immunosensor to analyze atrazine in complex sample matrices, such as red wine, have been evaluated. This immunosensor can detect atrazine with limits of detection in the order sub-ppb, far below the maximum residue level (MRL) (50 μg L−1) established by European Union (EU) for residues of this herbicide in the wine grapes.
Valera, E.; Ramón-Azcon, J.; Sánchez, F.; Marco, M.P.; Rodriguez, A. Congreso Español de Ingeniería de Alimentos y Congreso Iberoamericano sobre Seguridad Alimentaria (CESIA-CIBSA) p. 1-6 Data de presentació: 2008-11 Presentació treball a congrés
En este trabajo describimos un immunosensor impedimétrico para la detección de
pesticidas. Para demostrar dicho sensor hemos utilizado atrazina, como pesticida de test. Este sensor está basado en el uso de μ-electrodos interdigitados así como en reactivos específicamente desarrollados para la detección de este pesticida. Los anticuerpos utilizados no incluyen ningún tipo de etiqueta. Así mismo, el sensor no
incluye ningún tipo de par redox que amplifique la señal. La detección immunoquímica de atrazina se alcanza mediante una reacción competitiva entre el antígeno tapizado y el pesticida por una pequeña cantidad de anticuerpo. Los cambios en la impedancia producidos por la inclusión de los bioreactivos son interpretados utilizando un circuito equivalente, el
cual representa el sistema de manera fiable. La detección se monitoriza a partir de medidas impedimétricas diferenciales en un amplio espectro de frecuencia. El immunosensor muestra límites de detección en el rango de pocos ppb's, lo cual está muy
por debajo del Maximum Residue Level (MRL) (50 μg L-1) establecido por la Unión Europea
para los residuos de atrazina en uvas de vino así como en otros productos alimenticios.
Aunque en este trabajo el immunosensor se ha demostrado para la atrazina, otros pesticidas
podrían detectarse mediante este método siempre que se utilicen los reactivos adecuados.
Valera, E.; Ramón, J.; Sánchez, F.; Marco, M.P.; Rodriguez, A. Sensors and actuators B. Chemical Vol. 134, num. 1, p. 95-103 DOI: 10.1016/j.snb.2008.04.023 Data de publicació: 2008-09-28 Article en revista
A novel conductimetric immunosensor for atrazine detection has been designed and developed. This immunosensor is mainly based on antibodies labelled with gold nanoparticles. Additionally, the immunosensor consists of an array of two coplanar non-passivated interdigitated metallic µ-electrodes (IDµE) and immunoreagents specifically developed to detect this pesticide. The chemical recognition layer was covalent immobilized on the interdigital space. Immunochemical detection of the concentration of atrazine is achieved by a competitive reaction that occurs before the inclusion of the labelled antibodies. It is shown that the gold nanoparticles provide an amplification of the conductive signal and hence makes possible to detect atrazine by means of simple DC measurements.
The conductimetric immunosensor and its biofunctionalization steps have been characterized by chemical affinity methods and impedance spectroscopy.
This work describes the immunosensor structure, fabrication, physico-chemical and analytical characterization, and the immunosensor response using conductivity measurements. The immunosensor developed detects atrazine with limits of detection in the order of 0.1–1 µg L-1, far below the maximum residue level (MRL) (100 µg L-1) established by European Union (EU) for residues of this herbicide in the wine.
Although in this paper the competitive reaction occurs in buffer, an initial study of the wine matrix effect is also described.
Ramón, J.; Valera, E.; Rodriguez, A.; Barranco, A.; Alfaro, B.; Sánchez, F.; Marco, M.P.; Castañer, L. Biosensors and bioelectronics Vol. 23, num. 9, p. 1367-1373 DOI: 10.1016/j.bios.2007.12.010 Data de publicació: 2008-04-15 Article en revista
A novel impedimetric immunosensor for atrazine detection has been developed. The immunosensor is based on an array of interdigitated µ-electrodes (IDµE) and immunoreagents specifically developed to detect this pesticide. Immunochemical determination of atrazine is possible without the use of any label. An atrazine-haptenized protein was covalently immobilized on the surface of the interdigitated µ-electrodes area (interdigits space) previously activated with (3-glycidoxypropyl)trimethoxysilane. Before, the gold electrodes were blocked using N-acetylcysteamine to prevent non-specific adsorptions. All biofunctionalization steps were characterized by chemical affinity methods and impedance spectroscopy. Immunosensors measures are made by exposing the sensor to solutions containing a mixture of the analyte and the specific antibody. With this configuration, the immunosensor detects atrazine with a limit of detection of 0.04 µg L-1 without the use of any label. The potential of the immunosensor to analyze pesticide residues in complex sample matrices, such as red wine, has been evaluated. The results shown that after solid-phase extraction atrazine can be determined in this type of sample with a limit of detection of 0.19 µg L-1, far below the Maximum Residue Level (MRL) established by EC for residues of this herbicide in wine.
Rodriguez, A.; Valera, E.; Ramón-Azcón, J.; Sanchez, J.; Marco, M.P.; Castañer, L. Sensors and actuators B. Chemical Vol. 129, num. 2, p. 921-928 DOI: 10.1016/j.snb.2007.10.003 Data de publicació: 2008-02-22 Article en revista
A novel impedimetric immunosensor for the detection of a wide variety of compounds, based on a two coplanar non-passivated interdigitated metallic µ-electrodes and non-labeled immunoreactives, has been designed and developed. A very useful detection method is the impedance spectroscopy sweeping a wide frequency range. This is a powerful, but cumbersome tool to study the sensor performance providing trustworthy results. In this work, it is shown that the exploitation of the changes observed of the impedance at a single frequency provide very good correlation with antibody concentration and hence greatly reduces the signal acquisition and processing complexity. It has thereby a great potential for low cost, low power, fast response and simple use for the in-field or at-line applications. In this work, the application of the method to atrazine detection is described. The results show that the immunosensor signal is a function of the pesticide concentration following a competitive binding relationship, with limits of detection lower than the maximum residue level required by EC for atrazine in wine grapes and other foodstuff products.
Steady-state and transient conductance measurements of gold nanobeads solutions deposited on top of interdigitated electrodes have been performed. It is shown that the application of an electric field of moderate value between electrodes during the drying process of the droplet makes the resulting steady-state conductance value to increase significantly. The dynamics of the gold nanobeads in the solution has been studied by means of transient current measurements during the drying process and the effects correlated to the changes in the morphology of the association of the gold nanobeads when they reach the substrate. It is seen that the application of the electric field foster the formation of gold beads monolayers, chains, and dendritic associations which, in combination with the humidity conditions of the sample surface, are believed to be the reasons for the conductance increase.
Urbiztondo, M.; Valera, E.; Trifonov, T.; Alcubilla, R.; Irusta, S.; Pina, M.; Rodriguez, A.; Santamaria, J. Journal of catalysis Vol. 250, num. 1, p. 190-194 DOI: 10.1016/j.jcat.2007.05.022 Data de publicació: 2007-08-15 Article en revista
Regular structures of SiO2 microneedles and Si micromonoliths have been formed using processing methods similar to those used in the microelectronics field; then these structures have been used as supports for zeolite (silicalite) films, grown on them by means of seeded hydrothermal synthesis. The procedure leads to microstructured nanoporous coatings with external characteristic dimensions of a few microns in size and short diffusion lengths, allowing intimate fluid–solid contact. Depending on the preparation conditions, the resulting films exhibit values of the external surface to volume ratio in the 400,000–700,000 m2/m3 range.
Valera, E.; Ramón, J.; Rodriguez, A.; Castañer, L.; Sánchez, F.; Marco, M.P. Sensors and actuators B. Chemical Vol. 125, num. 2, p. 526-537 DOI: 10.1016/j.snb.2007.02.048 Data de publicació: 2007-08-08 Article en revista
A novel impedimetric immunosensor for atrazine detection, a widely used pesticide, is described. It is based on a two coplanar non-passivated interdigitated metallic µ-electrodes (IDµE) and the differential measurement of the impedance frequency spectrum. No redox electrodes have been included in the sensor. The chemical recognition layer was deposited on top of the interdigitated µ-electrodes area (fingers and inter-digits space). Immunochemical detection of the atrazine concentration is achieved by a competitive reaction without using any label. Furthermore immunoreagents specifically developed to detect this pesticide have been used.
The immunosensor and its functionalization steps have been characterized by means of chemical affinity methods and impedance spectroscopy. This work describes immunosensor development and its physico-chemical and analytical characterization. The immunosensor shows a limit of detection of 8.34 ± 1.37 µg L-1, which is lower than the Maximum Residue Level (MRL) (100 µg L-1) established by EU (European Union) for residues of atrazine as herbicide in the wine grapes and other foodstuff products.
Rodriguez, A.; Molinero, D.; Valera, E.; Trifonov, T.; Marsal, L.; Pallarès, J.; Alcubilla, R. Sensors and actuators B. Chemical Vol. 109, num. 1, p. 135-140 DOI: 10.1016/j.snb.2005.03.015 Data de publicació: 2005-04 Article en revista
This paper presents a novel technique for silicon dioxide (SiO2) microneedle fabrication. Microneedles are hollow microcapillaries with tip diameters in the range of micrometers. They can be used in the fabrication of microsyringes. These structures can be of high interest in medical and biological applications, such as DNA injection, antibody manipulation and drug delivery, and cell manipulation. Fabrication process is based on electrochemical etching of n-type silicon in hydrofluoric acid (HF) solutions. Basic process flow and etching conditions that ensure a stable pore growth are described. These conditions also determine the geometry of the resulting microneedle structure. Microneedle arrays of different dimensions can be fabricated in a single run on the same wafer. In this work, microneedle arrays with pore diameters ranging from 2 to 5 µm, pore lengths from 30 to 140 µm and wall thicknesses in the range of 70–110 nm are reported.