Measurement Time Reduction by Means of Mathematical Modeling of Enzyme Mediated RedOx Reaction in Food Samples Biosensors

The possibility of measuring in real time the different types of analytes present in food is becoming a requirement in food industry. In this context, biosensors are presented as an alternative to traditional analytical methodologies due to their specificity, high sensitivity and ability to work in real time. It has been observed that the behavior of the analysis curves of the biosensors follow a trend that is reproducible among all the measurements and that is specific to the reaction that occurs in the electrochemical cell and the analyte being analyzed. Kinetic reaction modeling is a widely used method to model processes that occur within the sensors, and this leads to the idea that a mathematical approximation can mimic the electrochemical reaction that takes place while the analysis of the sample is ongoing. For this purpose, a novel mathematical model is proposed to approximate the enzymatic reaction within the biosensor in real time, so the output of the measurement can be estimated in advance. The proposed model is based on adjusting an exponential decay model to the response of the biosensors using a nonlinear least-square method to minimize the error. The obtained results show that our proposed approach is capable of reducing about 40% the required measurement time in the sample analysis phase, while keeping the error rate low enough to meet the accuracy standards of the food industry

Analytical Parameters of an Amperometric Glucose Biosensor for Fast Analysis in Food Samples

Amperometric biosensors based on the use of glucose oxidase (GOx) are able to combine the robustness of electrochemical techniques with the specificity of biological recognition processes. However, very little information can be found in literature about the fundamental analytical parameters of these sensors. In this work, the analytical behavior of an amperometric biosensor based on the immobilization of GOx using a hydrogel (Chitosan) onto highly ordered titanium dioxide nanotube arrays (TiO2NTAs) has been evaluated. The GOx–Chitosan/TiO2NTAs biosensor showed a sensitivity of 5.46 μA·mM−1 with a linear range from 0.3 to 1.5 mM; its fundamental analytical parameters were studied using a commercial soft drink. The obtained results proved sufficient repeatability (RSD = 1.9%), reproducibility (RSD = 2.5%), accuracy (95–105% recovery), and robustness (RSD = 3.3%). Furthermore, no significant interferences from fructose, ascorbic acid and citric acid were obtained. In addition, the storage stability was further examined, after 30 days, the GOx–Chitosan/TiO2NTAs biosensor retained 85% of its initial current response. Finally, the glucose content of different food samples was measured using the biosensor and compared with the respective HPLC value. In the worst scenario, a deviation smaller than 10% was obtained among the 20 samples evaluated

The effect of short sleep duration and exercise on glycaemic control in healthy adults

Short sleep durations are common amongst adults across the world. They have been linked to metabolic disorders, and, more specifically, impaired glycaemic control. Acute and chronic physical activity are known to have beneficial effects on metabolic health, and therefore may be able to attenuate the link between short sleep and impaired glycaemic control. The purpose of this thesis was to explore the potential for exercise to alter glycaemic control in short sleep durations. Specifically, the aims were threefold: (a) to understand the impaired glycaemic response to glucose intake over consecutive nights of sleep restriction (Chapter 4); (b) to investigate if exercise could alleviate the sleep restriction induced impairment in insulin sensitivity (Chapter 5); and (c) to determine if these factors act in a similar manner when transferred to the free-living environment (Chapter 6). The findings in Chapter 4 demonstrated that the number of nights of sleep restriction did not appear to affect the impairment in glycaemic control. These findings informed the study in Chapter 5, which used a randomised cross-over design to explore the potential for acute exercise to attenuate the impairment in glucose regulation after a single night of sleep restriction. The findings suggest that sprint interval exercise may be beneficial for the late postprandial period after sleep restriction, as demonstrated by a reduced insulin area under the curve. However, when examined in the free-living environment (Chapter 6), habitual short sleep duration did not show any evidence of impairing markers of glycaemic control when confounding factors such as sex, diet, and body composition were taken into consideration. Collectively, the studies in this thesis confirm that short-term short sleep impairs glucose regulation and suggest that exercise may be beneficial for glucose regulation after short sleep in the acute setting, but findings may be contradictory in chronic settings. Further study is warranted to establish the effects of different exercise modalities on glucose regulation after sleep restriction and to fully understand the link between habitual sleep duration, physical activity, and glycaemic control. However, a session of sprint interval exercise could be recommended to individuals after acute sleep restriction to alleviate the impairment in insulin sensitivity

Novel electrochemical components as tools for pharmaceutical application

Según el Instituto Nacional sobre el Envejecimiento, la expectativa de vida promedio de la población ha aumentado significativamente en los últimos cien años. Sin embargo, no fue seguido por la esperanza de vida saludable. Junto con la globalización, el cambio de las dietas tradicionales a los productos alimenticios procesados ha aumentado la prevalencia de la obesidad y la sobrenutrición, que es responsable de muchos problemas de salud, como las enfermedades no transmisibles que pueden convertirse en enfermedades de por vida. Es fundamental monitorear los analitos del organismo asociados con esos trastornos de salud y los factores que los promueven para controlar y lograr la disminución de tales condiciones médicas. Con el propósito de profundizar en la comprensión de las condiciones fisiológicas que desencadenan algunas enfermedades, será fundamental rastrear algunas moléculas biológicas dentro del organismo humano. Un ejemplo es la vigilancia de los receptores dopaminérgicos, que son responsables del sistema de recompensa en el cerebro y, por lo tanto, están indirectamente relacionados con los problemas de adicción. Alternativamente, los niveles de concentración de H2O2 en fluidos biológicos ya que, en altas cantidades extracelulares, son indicativos de varios procesos fisiopatológicos dentro del cuerpo humano. Los métodos electroquímicos son relevantes para determinar varias moléculas a través del monitoreo de la reacción redox en la superficie del electrodo, proporcionando métodos de alta sensibilidad y bajo límite de detección para rastrear biomoléculas importantes en la sangre humana. En la mayoría de los biosensores, la monitorización se realiza mediante una inmovilización enzimática en la superficie del electrodo. Sin embargo, considerando las vulnerabilidades enzimáticas, como la baja estabilidad y las restricciones de temperatura y pH, el método de detección ideal se basa en la reacción directa del sustrato en la superficie de un electrodo no enzimático. Por lo tanto, el detector amperométrico no enzimático es una opción adecuada. Además de la vigilancia de algunos elementos vitales entre los fluidos corporales, también es de gran interés explorar la capacidad de determinadas membranas de intercambio iónico comerciales en algunos procesos electrodialíticos estándar utilizados en el desarrollo y producción de medicamentos en la industria farmacéutica. Este estudio tiene como objetivos: Prospectar la aplicación de dos aleaciones bimetálicas como un nuevo tipo de transductor en la detección electroquímica de H2O2. Estudiar el empleo de dos tipos de membranas de intercambio iónico como separadores para los procesos de filtración por electrodiálisis utilizados en los procedimientos químicos de la industria farmacéutica. Materializar una combinación adecuada de nanopartículas de plata AgNPs sintetizadas con extracto de terpenoides biológicos, con un polímero altamente conductivo, soportado en carbón negro Vulcan para ser utilizado como material altamente catalítico de un nuevo electrodo para la vigilancia electroquímica sensible de algunas especies electroactivas importantes. Palabras clave: Aleación bimetálica; electrodiálisis; detector electroquímico; electrodo modificado; Síntesis a base dde extractos de terpenoides

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