Electrochemical sensors and biosensors: new horizons and challenges in their integration in multisensor systems for food industry applications

La presente Tesis doctoral, plantea el desarrollo de sensores y biosensores para el análisis de alimentos, empleando diferentes materiales y nanomateriales sensibles. Se trata de sensores y biosensores electroquímicos que permiten detectar compuestos de interés en alimentos líquidos tales como leches o vinos. Los sensores se han diseñado empleado diferentes materiales sensibles y tecnologías relacionadas con la Nanociencia, con el propósito de mejorar parámetros analíticos como son: selectividad, sensibilidad, reproducibilidad y repetitividad. Los sensores y biosensores se han utilizado para desarrollar redes de sensores que forman lenguas electrónicas y bioelectrónicas. La preparación y caracterización de los sensores y biosensores desarrollados, así como sus respuestas electroquímicas y su funcionamiento como parte de lenguas electrónicas, se discuten mediante los artículos científicos, indexados en revistas internacionales, incluidos en esta Tesis Doctoral.Departamento de Química Física y Química InorgánicaDoctorado en Físic

Discrimination of milks with a multisensor system based on layer-by-layer films

Producción CientíficaA nanostructured electrochemical bi-sensor system for the analysis of milks has been developed using the layer-by-layer technique. The non-enzymatic sensor [CHI+IL/CuPcS]2, is a layered material containing a negative film of the anionic sulfonated copper phthalocyanine (CuPcS) acting as electrocatalytic material, and a cationic layer containing a mixture of an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate) that enhances the conductivity, and chitosan (CHI), that facilitates the enzyme immobilization. The biosensor ([CHI+IL/CuPcS]2-GAO) results from the immobilization of galactose oxidase on the top of the LbL layers. FTIR, UV–vis, and AFM have confirmed the proposed structure and cyclic voltammetry has demonstrated the amplification caused by the combination of materials in the film. Sensors have been combined to form an electronic tongue for milk analysis. Principal component analysis has revealed the ability of the sensor system to discriminate between milk samples with different lactose content. Using a PLS-1 calibration models, correlations have been found between the voltammetric signals and chemical parameters measured by classical methods. PLS-1 models provide excellent correlations with lactose content. Additional information about other components, such as fats, proteins, and acidity, can also be obtained. The method developed is simple, and the short response time permits its use in assaying milk samples online.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project AGL2015-67482-R)Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA-011U16)Junta de Castilla y León (grant BOCYL-D-4112015-9

Biosensors Platform Based on Chitosan/AuNPs/Phthalocyanine Composite Films for the Electrochemical Detection of Catechol. The Role of the Surface Structure

Producción CientíficaBiosensor platforms consisting of layer by layer films combining materials with different functionalities have been developed and used to obtain improved catechol biosensors. Tyrosinase (Tyr) or laccase (Lac) were deposited onto LbL films formed by layers of a cationic linker (chitosan, CHI) alternating with layers of anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS or gold nanoparticles, AuNP). Films with different layer structures were successfully formed. Characterization of surface roughness and porosity was carried out using AFM. Electrochemical responses towards catechol showed that the LbL composites efficiently improved the electron transfer path between Tyr or Lac and the electrode surface, producing an increase in the intensity over the response in the absence of the LbL platform. LbL structures with higher roughness and pore size facilitated the diffusion of catechol, resulting in lower LODs. The [(CHI)-(AuNP)-(CHI)-(CuPcS)]2-Tyr showed an LOD of 8.55∙10−4 μM, which was one order of magnitude lower than the 9.55·10−3 µM obtained with [(CHI)-(CuPcS)-(CHI)-(AuNP)]2-Tyr, and two orders of magnitude lower than the obtained with other nanostructured platforms. It can be concluded that the combination of adequate materials with complementary activity and the control of the structure of the platform is an excellent strategy to obtain biosensors with improved performances.Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (project RTI2018-097990-B-100)Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA275P18)Infraestructuras Red de Castilla y León (grant UVA01

Promoting laccase sensing activity for catechol detection using LBL assemblies of chitosan/ionic liquid/phthalocyanine as immobilization surfaces

Producción CientíficaThe performance of electrochemical laccase-based biosensors can be improved by immobilizing the enzyme on composite Layer-by-Layer (LbL) supports in which materials with complementary functions are combined. LbL films are formed by layers combining an electrocatalytic material which favors electron transfer (sulfonated copper phthalocyanine, CuPcS(−)), an ionic liquid which enhances the electrical conductivity of the layers (1-butyl-3-methylimidazolium tetrafluoroborate, IL(+)) and a material able to promote enzyme immobilization (chitosan, CHI(+)). Composite films with different structures have been demonstrated to be efficient electrocatalysts, producing an increase in the magnitude of the responses towards catechol. The most intense and reproducible electrocatalytic effect was observed when a layer of the CuPcS(−) was placed on top of a layer formed by a mixture of CHI(+) + IL(+) to obtain [CHI(+) + IL(+)|CuPcS(−)]2 films. Biosensors with laccase immobilized on the surface of the LbL layers [CHI(+) + IL(+)|CuPcS(−)]2|Lac showed mediated electron transfer between the redox enzyme and the film and a reproducibility of device-to-device performance of 4.1%. The amperometric biosensor showed a sensitivity of 0.237 A·M−1 and a linear detection range from 2.4 μM to 26 μM for catechol. The excellent Limit of detection (LOD) of 8.96·10−10 M (3·σ /m) is one order of magnitude lower than that obtained in similar studies. A Michaelis-Menten constant of 3.16 μM confirms excellent enzyme-substrate affinity.Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (projects AGL2015-67482-R and RTI2018_097990-B-100)Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (project VA275P18

Concurrent study of the electrochemical response and the surface alterations of silver nanowire modified electrodes by means of EC-AFM. The role of electrode/nanomaterial interaction

Producción CientíficaThe use of nanomaterials as electrode modifiers permits the enhancement of electrode performance using a great variety of approaches, from electrocatalytic enhancement to the improvement of charge transfer processes. The control and understanding of the interaction between the modifiers and the electrode itself are of key importance for the final performance of the modified electrode. This becomes especially relevant in the case of nanostructured materials since their physical response is rarely trivial. In this work, we combined electrochemistry and atomic force microscopy (EC-AFM) to in-situ investigate the surface condition of electrodes modified with silver nanowires (AgNWs) during EC measurements for the first time. EC-AFM allows us to perform cyclic voltammetry and electrochemical impedance spectroscopy together with the assessment of the electrode surface directly in the electrolytic solution. On the other hand, the use of the Langmuir-Blodgett technique provides homogeneity and reproducibility to the electrode modification process. The electrochemical response of the modified electrodes has been found to strongly depend on the selected substrate, but also on the deposition procedure. This opens the path for a better understanding of electrode modification process, and also supports the viability of EC-AFM on open problems involving electrochemistry and surface science.MINECO-FEDER (RTI2018–097990-B-100)Junta de Castilla y León-FEDER (VA202P20)Programa EU-FEDER (CLU-2019–04)Unión Europea–NextGenerationEU y la Universidad de Valladolid (CONVREC-2021–23)

Improved corrosion behavior and biocompatibility of porous Titanium samples coated with bioactive Chitosan-based nanocomposites

Producción CientíficaPorous titanium implants can be a good solution to solve the stress shielding phenomenon. However, the presence of pores compromises mechanical and corrosion resistance. In this work, porous titanium samples obtained using a space-holder technique are coated with Chitosan, Chitosan/AgNPs and Chitosan/Hydroxyapatite using only one step and an economic electrodeposition method. The coatings’ topography, homogeneity and chemical composition were analyzed. A study of the effect of the porosity and type of coating on corrosion resistance and cellular behavior was carried out. The electrochemical studies reveal that porous samples show high current densities and an unstable oxide film; therefore, there is a need for surface treatments to improve corrosion resistance. The Chitosan coatings provide a significant improvement in the corrosion resistance, but the Chitosan/AgNPs and Chitosan/HA coatings showed the highest protection efficiency, especially for the more porous samples. Furthermore, these coatings have better adherence than the chitosan coatings, and the higher surface roughness obtained favors cell adhesion and proliferation. Finally, a combination of coating and porous substrate material with the best biomechanical balance and biofunctional behavior is proposed as a potential candidate for the replacement of small, damaged bone tissues.Ministerio de Ciencia, Innovación y Universidades (grants RTI2018-097990-B-I00 and PID2019-109371GB-I00)Junta de Andalucía - Fondo Europeo de Desarrollo Regional (project US-1259771)Junta de Castilla y León (projects VA275P18 and VA044G19

Development of a bioelectronic tongue modified with gold nanoparticles for dairy analysis

Producción CientíficaThe objective of this work was to create an all-solid-state potentiometric bioelectronic tongue with an array of polymeric membrane-based sensors, which could then be used in the dairy sector. Membranes were modified with gold nanoparticles, and enzymes were covalently linked to the sensor’s surface to create an array of sensors with greater sensitivity. The responses of the sensors modified with gold nanoparticles and covalently associated enzymes, showed higher sensitivities. Moreover, the developed bioelectronic tongue was able to perform the discrimination of milks with different nutritional characteristics by applying principal component analysis. In addition, the results obtained showed that by applying partial least squares analysis, the system could be used as a prediction system for different chemical parameters (such as acidity, proteins, lactose, etc.).Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (FEDER) - (Project RTI2018-097990-B-100)Junta de Castilla y León y Fondo Europeo de Desarrollo Regional (FEDER) - (Project VA275P18

Nanocomposites of conductive polymers and nanoparticles deposited on porous material as a strategy to improve its corrosion resistance

Producción CientíficaA strategy for the corrosion protection of porous materials using conductive polymers and nanocomposites of polymers and nanoparticle is presented. Several conductive polymers, various dopants and different electropolymerization conditions are studied to select the films with the highest corrosion resistance on porous and non-porous materials. It is found that nanocomposite films prepared from two different methods i.e., the co-generation of Au nanoparticles and the dispersion of TiO2 nanoparticles inside the selected polymer coating give rise to an excellent corrosion resistance. Coated porous samples have the most noble corrosion potentials, the lowest stable passive current densities and the highest polarization resistances.Ministerio de Educación y Formación Profesional (project RTI2018-097990-B-I00)Junta de Castilla y León (projects VA275P18 and VA044G19

A new data analysis approach for an AgNPs-modified impedimetric bioelectronic tongue for dairy analysis

Producción CientíficaAn alternative approach to analyze complex matrices, such as milk, lies on multivariate description of the chemical composition of samples, where fingerprints for each sample are generated using data mining methods (Principal Component Analysis, PCA, and Supported Vector Machine). Electronic tongues (ET) hold substantial potential for the dairy industry as analytical tools due to their fast analysis. The purpose of this work was to create an impedimetric ET with an array of microelectrode sensors for application in the dairy industry. A sensor array with enhanced sensitivity and selectivity silver nanoparticles and enzymes were developed. Higher sensitivity was evident in the responses of this array to milk components of interest like glucose, galactose, lactose, and urea. PCA of the signals obtained using the optimized ET has allowed the discrimination of milks with different characteristics. SVM was used to stablish correlations between the signals obtained from the ET and the physicochemical parameters. Electrochemical Impedance Spectroscopy have also shown that the ET in combination with the equivalent circuits approach could be a potential tool for its further application in dairy analysis. Moreover, the study of milk samples confirmed the high cross-selectivity of the system which allowed the development of classification models and to stablish correlations between the ET and physicochemical parameters.MICINN-FEDER (PID2021-122365OB-I00) «Infraestructuras Red de Castilla y León (INFRARED)»Junta de Castilla y León - Consejería de Educación - FEDER (VA275P18)Calidad Pascual farm (Aranda de Duero) (ALIVAC-IDI-20211051

Analysis of red wines using an electronic tongue and infrared spectroscopy. Correlations with phenolic content and color parameters

Producción CientíficaThe objective of this work was to develop a methodology based on multiparametric methods (FTIR and a voltammetric e–tongue based on SPE) to evaluate simultaneously fourteen parameters related to the phenolic content of red wines. Eight types of Spanish red wines, elaborated with different grape varieties from different regions and with different aging, were analyzed with both systems. Input variables used for multivariate analysis were extracted from FTIR spectra and voltammograms using the kernel method. PCA analysis could discriminate wines according to their phenolic content with PC1, PC2 and PC3 explaining the 99.8% of the total variance between the samples for FTIR analysis and 85.8% for the e-tongue analysis. PLS calculations were used to establish regression models with phenolic content parameters measured by UV–Vis spectroscopy (TPI, Folin-Ciocalteu, CIELab and Glories) with high correlation coefficients (R2 > 0.85), and low RMSEs (<3.0) and number of factors (<4). Both, PCA and PLS, were carried out using the full cross validation method. As time is a critical factor in the food industry, the main advantage of these multivariate techniques is their capability to evaluate many parameters in a single experiment and in shorter time than using independent classical techniques.Ministerio de Educación y Formación Profesional (project RTI2018-097990-B-I00)Junta de Castilla y Leon (grants VA275P18 and BOCYL-D-24112015-9