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Etude des propriétés structurales, morphologiques et électrochimiques de couches minces de nanocomposites hybrides de type hydroxyde double lamellaire (HDL) / biomolécules : application aux biocapteurs de polyphénols

Abstract : Polyphenols are in abundance in diet, being present in various fruits or vegetables, but also in tea or wine. Their antioxidant properties attracted an increasing interest of different researchers in the field of medicine and food manufacturers. Consequently, very intensive studies have been conducted to develop efficient polyphenols biosensors, while respecting certain criteria (simplicity of use, speed of measurement, low cost). In the case of enzymatic biosensors, the decisive step is the immobilization of the enzyme on the transducer surface without affecting its performances.In this thesis, we used layered double hydroxides (LDHs) as a host matrix to immobilize tyrosinase, an enzyme recognizing specifically polyphenols, at the surface of screen printed gold electrodes. Polyphenols used to study the biosensors were extracted from green tea.LDHs nanosheets were prepared by the co-precipitation method. In a first step, their structural properties were characterized by X-ray powder diffraction, Raman and Infra-Red spectroscopies, confirming crystalline phase and chemical composition of LDHs. In a second step, LDHs-thin films were prepared by self-assembly and spin coating deposition under various experimental conditions (nature and concentration of LDHs …), and studied by Atomic Force Microscopy (AFM) to obtain information about the surface morphology of the host matrix before enzyme immobilization. The presence of tyrosinase after the immobilization step was also confirmed by AFM. Electrochemical characteristics of the amperometric biosensors, whose design is based on this study, were determined by cyclic voltammetry and chronoamperometry. This study showed that these systems are highly sensitive to polyphenols, detecting them by their oxidation but also by the reduction of compounds enzymatically generated. They exhibit also other very attractive characteristics for the detection of complex mixture of polyphenols: a large dynamic range (up to 1000 ng.mL-1)and a very low detection limit (few pg.mL-1).
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Asma Soussou. Etude des propriétés structurales, morphologiques et électrochimiques de couches minces de nanocomposites hybrides de type hydroxyde double lamellaire (HDL) / biomolécules : application aux biocapteurs de polyphénols. Autre. Université de Bordeaux, 2016. Français. ⟨NNT : 2016BORD0302⟩. ⟨tel-01673629⟩

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