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Capteurs chimiques à base de matrices nanoporeuses pour la détection de métabolites volatils de la tuberculose

Abstract : Tuberculosis kills nearly 2 million people each year, mainly because of late or inefficient diagnostic or late cures. The most efficient methods are often too expensive and too complex to implement in developing countries, areas of greater incidence of the disease. The aim of this project is the design of luminescent sensors for the detection of a very specific tuberculosis metabolite, nicotinic acid, detected in concentration ranging from around ten to hundred ppq, present in sick people’s breath, and to discriminate it from other metabolites.A terbium nitrate complex is used as its luminescence can be sensitized by organic ligands, as nicotinic acid. A first step was the optimization of the pH of aqueous solution to enhance the complexation between Tb3+ ion and nicotinic acid. A solution buffered at pH 6,4 using hexamine allows optimization of the complex formation and energy transfer from nicotinic acid to terbium. Sampling of nicotinic acid can be done in the range 400 nM-100 μM, or from 7,2 to 1,8 ppm.The second step was to design nanoporous matrices from silicon alcoxydes to obtain matrix with an intraporous pH of 6,4. We studied the changes of the matrix intraporous pH while trapping water vapor or carbon dioxide, present in high concentration in breath, using bromothymol blue as pH indicator. The matrices were produced from 2 silicon precursors, one of them containing an aminopropyle carbon chain, conferring an alkaline nature. Changes of the matrix pH between 6,5 and 6 were observed following the exposure of a silica matrix containing 3 % of the aminated precursor to water vapor to saturation. This range of pH value is optimized to favor Tb3+-nicotinic acid complex formation.In the last step, silica matrix containing 3% of the aminated precursor, doped with terbium and buffered at pH 6,4 with hexamine were designed. Luminescence measurements made on matrix exposed to vapors from pure nicotinic acid or saturated aqueous solution, showed an increase of the matrix luminescence, proof of the trapping of nicotinic acid in the nanoporous matrix and of the complexation between nicotinic acid and Tb3+. Trapping of nicotinic acid and subsequent complexation with Tb3+ are lowered by the presence of water vapor, which can partially deactivate the luminescent excited state of Tb3+. Interference studies showed that secondary metabolites as methyl nicotinate can only affect the luminescence of Tb3+/AN complex by competitive absorption of the excitation radiation. Detection methods free of interferences from the secondary metabolites are studied.
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William Bamogo. Capteurs chimiques à base de matrices nanoporeuses pour la détection de métabolites volatils de la tuberculose. Chimie théorique et/ou physique. Université Paris Sud - Paris XI, 2015. Français. ⟨NNT : 2015PA112010⟩. ⟨tel-01128414⟩

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