Novel nanomaterials for lab on chip devices development: application to food system and their effect on the oxidative stress in cell cultures

This Doctoral Thesis has been formed in two well-defined areas within the field of design and development of electrochemical sensors, using nanomaterials with high analytical performance in terms of sensitivity, selectivity and reproducibility. On the one hand, the properties of transition metal chalcogenides as new nanomaterials were explored with the aim of developing new high-performance electrochemical sensors. The transition metal chalcogenides are formed by triatomic sheets with the general formula MX2, where M is a transition metal and X is a chalcogenide (S, Se or Te) and where, in turn, M is arranged in a plane surrounded by two others of X linked by covalent bonds. Each of these sheets is held by Van der Waarls forces, facilitating their exfoliation in individual layers by simple methods. First, the ultrasound-assisted exfoliation of transition metals of group VI (MoS2, WS2, MoSe2 and WSe2) was carried out. Subsequently, they were characterized by scanning electron microscopy, Raman spectroscopy, and electrochemical techniques. Next, the electrocatalytic properties of these nanomaterials in the oxidation of polyphenolic compounds, chosen for this purpose for their high antioxidant capacity, were studied. These nanomaterials demonstrated excellent resistance to sensor passivation, one of the limiting factors in the application of electrochemical techniques in the analysis of complex samples. Ultimately, its analytical application to the determination of endogenous polyphenolic compounds in complex food matrices was demonstrated. On the other hand, electrochemical sensors were developed for the in-situ detection of hydrogen peroxide in cell cultures as a marker of oxidative stress. To this end, electrodes based on high-performance nanomaterials were designed and developed aimed at electrochemical sensitivity and selectivity (Carbon Black and Prussian Blue) for the selective detection and quantification of hydrogen peroxide in a cellular model of Parkison's disease. Likewise, an on-chip platform with similar analytical performance was developed to develop cell cultures, detect hydrogen peroxide under conditions of oxidative stress, as well as evaluate the antioxidant effect of exogenous polyphenolic compounds on oxidative stress levels.