Papers by María Begoña González García
The development of user-friendly, time-saving and cost-effective analytical strategies for the de... more The development of user-friendly, time-saving and cost-effective analytical strategies for the detection and quality control of carbohydrates in food industry is continuously highly demanded. Therefore, in this work, two strategies for the non-enzymatic detection of reducing sugars (glucose and fructose), employing miniaturized screen-printed gold electrodes, were proposed. On the one hand, a high-throughput flow-injection analysis (FIA) system that employed gold electrodes integrated in a one channel flow-cell was developed. The injection of sample volume (60 µL) was done through an "in-line luer" injection port, placed closest to the electrochemical cell, and highly controlled by operator through a syringe. This configuration brings important advantages since it simplifies operability and effectiveness of working in FIA systems. The sugars detection was carried out by applying a potential of + 0.5 V in a NaOH 0.1 M flow carrier stream of 1 ml min-1. On the other hand, a batch mode approach using disposable gold electrodes for sugars detection by dropping the sample (60 µL) directly in the electrochemical cell was also investigated. The analytes were measured amperometrically, by applying a constant potential of + 0.5 V during 2 min, and by determining the anodic oxidation peak current by cyclic voltammetry. Accuracy and precision studies were performed and the limits of detection and linear ranges were established. Finally, the applicability of the developed non-enzymatic sensors has been successfully evaluated by determining reducing sugars in commercial foodstuffs.
Physical Chemistry Chemical Physics, 2020
Spectro-electrochemiluminescence is a powerful technique that allows the detailed analysis of the... more Spectro-electrochemiluminescence is a powerful technique that allows the detailed analysis of the ECL interaction of different luminophores as luminol and tris(2,2′-bipyridyl)dichlororuthenium(ii) (Ru(bpy)32+).
Current Opinion in Electrochemistry, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Research into electrochemical biosensors (EBs) has been continuously growing. The development of new materials and fabrication techniques are playing a key role. Important advances in wearable and self-powered devices are being accomplished. Wireless real-time data acquisition is a relevant feature for EBs development. EBs are expected to occupy an important place in the market as analytical tools.
Comprehensive Analytical Chemistry, 2007
Publisher Summary The objectives of this chapter are (i) to construct a hybridization-based genos... more Publisher Summary The objectives of this chapter are (i) to construct a hybridization-based genosensor for a 110 bp region of the TNFRSF21 gene (human tumor necrosis factor receptor superfamily, member 21 precursor) on a screen-printed carbon electrode (SPCE) modified with streptavidin which works as immobilization and transduction surface, (ii) to obtain both polymerase chain reaction (PCR) products labelled with FITC and unlabelled PCR products; latter products are labeled with fluorescein ULSs Kit, and (iii) to test these PCR products on the genosensor using alkaline phosphatase as enzymatic label and 3-indoxyl phosphate as enzymatic substrate. The results indicate that when the PCR products are labeled using the FITC labeled 5'-primer the analytical signals are higher and more reproducible than those obtained using the ULS labeling kit. Moreover, the PCR blank is higher in the latter case. The limit of detection, calculated as the copies of plasmid DNA corresponding to a signal which is the PCR blank signal plus three times the standard deviation of the PCR blank signal, results to be 360 copies of plasmid DNA.
Sensors and Actuators, B: Chemical, 2012
O editor não permite o depósito e disponibilização em acesso aberto do PDF que solicita. Para... more O editor não permite o depósito e disponibilização em acesso aberto do PDF que solicita. Para consultar o documento deve aceder ao endereço do editor.
Electroanalysis, 2014
ABSTRACT Here is presented a Flow Injection Analysis (FIA) system using a flow cell with an integ... more ABSTRACT Here is presented a Flow Injection Analysis (FIA) system using a flow cell with an integrated magnet, applied to biotin determination. The mixture of magnetic beads modified with streptavidin (Strep-MB), biotin and B-HRP is left 15 minutes under stirring and then a washing step is performed in an automatic way thanks to the external magnets coupled in the FIA system. After the immobilization of the MBs on the surface of the electrode, 3,3′,5,5′-Tetramethylbenzidine (TMB) is injected. The linear range obtained is between 0.5 to 10 pM of biotin and the sensitivity is 85 nA/pM.
Sensors and Actuators B: Chemical, 2006
Streptococcus pneumoniae has consistently been shown to be the most common cause of community-acq... more Streptococcus pneumoniae has consistently been shown to be the most common cause of community-acquired pneumonia in both adults and children, accounting for about two-thirds of cases in which an etiologic diagnosis is made [1] and is likely to be the leading cause ...
Electrochimica Acta, 2005
ABSTRACT
Electroanalysis, 2009
Gold nanostructured screen‐printed carbon electrodes are demonstrated to be suitable transducers ... more Gold nanostructured screen‐printed carbon electrodes are demonstrated to be suitable transducers for the determination of lead using square‐wave voltammetry. Reproducible gold nanostructures have been obtained by direct electrochemical deposition. A calibration plot from 2.5 to 250 μg/L was obtained in acidic solutions of Pb(II) with a reproducibility of 4% (n=10). The detection limit was 0.09 μg/L of lead. The method is then applied to perform a blood lead analysis by adjusting square‐wave parameters in capillary or venous blood with a minimum sample pretreatment and excellent accuracy and reproducibility.
Electroanalysis, 2004
A new methodology, based on silver electrocatalytic deposition and designed to quantify gold depo... more A new methodology, based on silver electrocatalytic deposition and designed to quantify gold deposited onto carbon paste electrode (CPE) and glassy carbon electrode (GCE), has been developed in this work. Silver (prepared in 1.0 M NH3) electrodeposition at −0.13 V occurs only when gold is previously deposited at an adequate potential on the electrode surface for a fixed period of time. When a CPE is used as working electrode, an adequate oxidation of gold is necessary. This oxidation is carried out in both 0.1 M NaOH and 0.1 M H2SO4 at oxidation potentials. When a GCE is used as working electrode, the oxidation steps are not necessary. Moreover, a cleaning step in KCN, which removes gold from electrode surface, is included. To obtain reproducibility in the analytical signal, the surface of the electrodes must be suitably pretreated; this electrodic pretreatment depends on the kind of electrode used as working electrode. Low detection limits (5.0×10−10 M) for short gold deposition ti...
Analytical Chemistry, 2005
Analytical and Bioanalytical Chemistry, 2006
Hydrolysis of indoxyl-based substrates by hydrolytic enzymes is a commonly used semiquantitative ... more Hydrolysis of indoxyl-based substrates by hydrolytic enzymes is a commonly used semiquantitative detection system that generates a water-insoluble indigo dye which is difficult to quantify. This work describes the quantitative analysis and enzyme kinetics for alkaline phosphatase (AP) and 5-bromo-4-chloro-3-indoxyl phosphate (BCIP) in solution obtained by applying known solubilization methodology from the textiles industry to the enzymatic product. This proposal is based on the reduction of the tetrahalo-indigo blue dye in a basic medium with the aim of generating its aqueoussoluble parent compound termed indigo white, which gives a rich yellow color in solution and is fluorescent. A quantitative ELISA (where a soluble end product is required) is accomplished for first time using BCIP as substrate.
Biosensors and Bioelectronics, 2000
Carbon paste electrodes, previously anodised in a basic media, are the basis for the development ... more Carbon paste electrodes, previously anodised in a basic media, are the basis for the development of a new voltammetric immunosensor device. Passive adsorption of the appropriate immunochemical reagent was performed onto the electrode surface. Alkaline Phosphatase labelled immunoglobulin was the tracer used in this work, 3-indoxyl phosphate being a very suitable enzymatic substrate for the electrochemical detection of the corresponding affinity reaction. The hydrolysis of this molecule generates indigo dimmer. This product was detected by alternating current voltammetry taking advantage of the adsorptive and inherent electrodic properties that it exhibits. The same electrochemical anodisation was used at the end of one assay to remove the entire protein layer attached to the carbon paste surface, allowing the formation of a new sensing phase and the use of the same support in several consecutive experiments. The methodology was applied to the design of two different immunoassays for the determination of human IgG. Good reproducibility of the electrodic signal and a limit of detection around 10 − 10 M were achieved.
ECS Meeting Abstracts, 2021
Electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an outstanding procedure th... more Electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an outstanding procedure that ensures the enhancement of Raman signal by the electrochemical activation of the electrode surface. In that way, activation of metallic screen-printed electrodes (SPEs) by electrochemical routes leads to the generation of reproducible nanostructures with excellent SERS properties [1,2] and opens new gates for analytical applications. In this work, detection of thiram, imidacloprid and chlorpyrifos pesticides is achieved by the development of a new procedure. This methodology offers a quick and easy protocol which consists of three steps: (1) preconcentration of the sample, (2) electrochemical activation of SPE and (3) Raman detection of pesticides (Figure 1). Figure 1. Raman spectrum of thiram obtained following the proposed procedure. Analysis of tap water samples provides suitable results that demonstrate the capabilities of the proposed method. In that way, Raman spectroelectrochem...
Determination of cell growth and viability is crucial for bioprocesses monitoring. Traditionally,... more Determination of cell growth and viability is crucial for bioprocesses monitoring. Traditionally, the control of the cell culture growth is performed by cell counting, which can be a time-consuming procedure that requires an expert user. Thus, in order to take the cell culture control to the next level, electrochemical enzymatic sensors for the in-situ measurement of substrates and metabolites of interest in cell cultures were developed. Two of the most commonly monitored parameters are glucose, as the major carbon and energy source, and lactate, as a metabolic product. Therefore, two amperometric enzymatic sensors specific towards this key analytes were developed. Glucose and lactate sensors were based on screen-printed miniaturized technology which allowed collecting samples from the media in order of microliters, without disturbing the cell culture. The proposed glucose and lactate sensors were able to distinguish differences in glucose and lactate levels in cell media 24 h after the cells have been seeded. Due to the quantitative establishment of the uptake of glucose and production of lactate it was possible to effectively control the growth process stages. Aspects such as the limits of detection, reproducibility and repeatability were studied and the figures of merit were obtained. The developed sensors revealed to be robust, highly stable, user-friendly and time-saving, demonstrating the possibility of being used as a cell culture monitoring trustful tool.
Dyes and Pigments, 2019
Raman and fluorescence spectroelectrochemistry techniques have been used for the in-situ study of... more Raman and fluorescence spectroelectrochemistry techniques have been used for the in-situ study of the reaction mechanism of resazurin/resorufin/dihydroresorufin system. Resazurin (RZ) is one of the most highly referenced substances used in studies on cell viability and cytotoxicity for a wide range of biological and environmental systems. Electrochemical behaviour of this tracer is based on the irreversible reduction of RZ, a slightly fluorescent compound, to resorufin (RS), a high fluorescent compound, while a subsequent and reversible reduction of RS generates dihydroresorufin (DHRS), a non-fluorescent compound. Time-resolved Raman spectroelectrochemistry has been used, for the first time, to perform dynamic studies of this system. The continuous optical acquisition provides a large number of spectra during the whole electrochemical reaction and not only at discrete potentials, offering a novel contribution to the literature related to this tracer. The characteristic Raman and fluorescence bands associated with each molecule as well as their evolution with potential allow us to obtain valuable information about the interconversion between RZ, RS and DHRS. In addition, spectroelectrochemistry demonstrates that experimental parameters play an essential role in the fluorescent response of this coloured system. In that way, operando multiresponse techniques shed more light for the complete understanding of RZ, RS and DHRS system, and they yield novel information to explain the electrochemical conversion of these compounds.
Talanta, 2019
Raman spectroelectrochemistry based on electrochemical surface-enhanced Raman scattering (EC-SERS... more Raman spectroelectrochemistry based on electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an interesting alternative to overcome the lack of sensitivity of normal Raman spectroscopy. Electrochemical activation of metallic screen-printed electrodes (SPEs) leads to the reproducible generation of nanostructures with excellent SERS properties. In that way, gold SPEs circumvent the traditional reproducibility limitation and produce the enhancement of the Raman intensity to favor the detection of low concentrations. Furthermore, fingerprint features of Raman spectroscopy make possible the dynamic spectroelectrochemical analysis of B vitamins. The accuracy assignments of Raman bands associated with B1, B2, B3, B6 and B12 vitamins present in multivitamin complexes provides valuable information, allowing us not only the detection of B vitamin present in mixtures, but also to understand the interaction between vitamins and metallic SERS surfaces.
Chemical communications (Cambridge, England), Jan 31, 2018
Dynamic time-resolved Raman spectroelectrochemistry demonstrates the strong influence of nanostru... more Dynamic time-resolved Raman spectroelectrochemistry demonstrates the strong influence of nanostructuring and surface charge of in situ activated disposable substrates for SERS detection. Under specific conditions, a large enhancement factor and estimated calculations agree with the feasible detection of only a few molecules, approaching the limit of single-entity detection.
Electrochemistry Communications, 2016
Two graphene oxide (GO) materials with different layer size and proportion of functional groups i... more Two graphene oxide (GO) materials with different layer size and proportion of functional groups in the basal planes (hydroxyl and epoxy) and in the edges (carbonyl and carboxyl) were used to modify the surface of commercially available screen printed electrodes. Cyclic voltammetry in 0.1 M KNO 3 was evaluated as an easy to use electrochemical methodology to reduce GO attached to the surface of screen-printed electrodes (SPEs). A cathodic peak related to the reduction of GO was identified, and the peak potential was correlated to the difficulty to reduce GO to Electrochemically Reduced Graphene Oxide (ERGO) depending on the functional groups present in the basal plane and in the edges of the original GO monolayers. Time resolved UV-VIS absorption spectroelectrochemistry in near-normal reflection mode on a screen-printed electrode is used for the very first time as an in-situ characterization technique for real time monitoring unambiguously the electrochemical reduction of graphene oxide.
Biosensors and Bioelectronics, 2015
A gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the deve... more A gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the development of an electrochemical immunosensor for Ara h 1 (a major peanut allergen) detection in food samples. Gold nanoparticles (average diameter¼32 nm) were electrochemically generated on the surface of screen-printed carbon electrodes. Two monoclonal antibodies were used in a sandwich-type immunoassay and the antibody-antigen interaction was electrochemically detected through stripping analysis of enzymatically (using alkaline phosphatase) deposited silver. The total time of the optimized immunoassay was 3 h 50 min. The developed immunosensor allowed the quantification of Ara h 1 between 12.6 and 2000 ng/ml, with a limit of detection of 3.8 ng/ml, and provided precise (RSD o8.7%) and accurate (recovery 496.6%) results. The immunosensor was successfully applied to the analysis of complex food matrices (cookies and chocolate), being able to detect Ara h 1 in samples containing 0.1% of peanut.
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Papers by María Begoña González García