Chez les levures, organismes eucaryotes unicellulaires, le glucose est la source d'énergie préférée. La levure modèle Kluyveromyces lactis possède deux perméases au glucose. L'expression d'une de ces deux perméases, codée par le gène RAG1, est induite par la présence de glucose extracellulaire et cette régulation transcriptionnelle dépend de la détection du glucose par un senseur membranaire spécifique, Rag4. Cependant, la régulation de l'expression de RAG1 dépend également de la capacité des cellules à métaboliser le glucose via la glycolyse. En effet, l'expression de RAG1 est fortement affectée dans des mutants glycolytiques malgré la présence de glucose extracellulaire. Au cours de cette thèse, nous nous sommes attachés à déterminer les mécanismes via lesquels la glycolyse contrôle l'expression de RAG1. Grâce à l'utilisation de mutants glycolytiques ou d'inhibiteurs chimiques de la glycolyse chez K. lactis, nous avons démontré que la glycolyse régule la stabilité du senseur Rag4 à la membrane plasmique et contrôle ainsi la voie de signalisation du glucose et l'expression de RAG1. De plus, ce mécanisme de contrôle est conservé chez la levure modèle Saccharomyces cerevisiae. L'étude plus approfondie de Rag4 nous a permis de déterminer que la transmission du signal glucose requiert la queue C-terminale cytoplasmique de Rag4, qui sert de plateforme d'interaction protéique. La caractérisation fonctionnelle de Rag4 nous a permis de mettre en évidence que la protéine contient plusieurs domaines impliqués dans le contrôle de sa stabilité en fonction du type de signal induisant la déstabilisation: signal glycolytique ou changement de source de carbone. Enfin, la nature du signal issu de la glycolyse qui cible le senseur membranaire Rag4 a été étudiée en testant deux hypothèses : le signal est protéique (enzyme de la glycolyse) ou métabolique (métabolite intermédiaire de la glycolyse). Ces travaux de thèse ont permis de mettre en évidence un rôle inédit de la glycolyse dans le contrôle de la stabilité des senseurs membranaires du glucose chez les levures K. lactis et S. cerevisiae / Yeasts are unicellular eukaryotic organisms which prefer glucose as energy source. The yeast model Kluyveromyces lactis has two glucose permeases. The expression of one of its permeases, RAG1, is induced by extracellular glucose. The glucose signaling pathway responsible for RAG1 expression regulation is dependent upon glucose sensing through a specific membrane glucose sensor, Rag4. However, RAG1 expression is also dependent upon glucose metabolism by glycolysis. Indeed, in glycolytic mutants RAG1 expression is strongly affected even when glucose is present. During these doctoral studies, we characterized mechanisms involved in glycolytic control on glucose signaling. Using glycolytic mutant or glycolysis chemical inhibitors, we have demonstrated that, in K. lactis, glycolysis targets the stability of the glucose sensor Rag4, controlling glucose signaling and RAG1 expression. This glycolytic control appears to be conserved in the yeast model Saccharomyces cerevisiae. We have shown that the C-terminal cytoplasmic tail of glucose sensor Rag4 is necessary for glucose signaling and forms a protein interaction platform. Rag4 protein contains several domains controlling Rag4 stability in response to different destabilization signals: glycolytic signal or carbon source signal. Finally, the nature of the glycolytic signal was studied considering two hypotheses: protein nature (e.g. glycolytic enzyme) or metabolic nature (e.g. glycolysis metabolic intermediate). This doctoral thesis underlines a new role of glycolysis in controlling membrane glucose sensor stability in K. lactis and S. cerevisiae

The main objective of nanotechnology is to build self-powered nanosystems that are ultrasmall in size, exhibit super sensitivity, extraordinary multi functionality, and extremely low power consumption. As we all know that 21st century has brought two most important challenges for us. One is energy shortage and the other is global warming. Now to overcome these challenges, it is highly desirable to develop nanotechnology that harvests energy from the environment to fabricate self-power and low-carbon nanodevices. Therefore a self-power nanosystem that harvests its operating energy from the environment is an attractive proposition. This is also feasible for nanodevices owing to their extremely low power consumption. One advantageous approach towards harvesting energy from the environment is the utilization of semiconducting piezoelectric materials, which facilitate the conversion of mechanical energy into electrical energy. Among many piezoelectric materials ZnO has the rare attribute of possessing both piezoelectric and semiconducting properties. But most applications of ZnO utilize either the semiconducting or piezoelectric property, and now it’s time to fully employ the coupled semiconducting-piezoelectric properties to form  the basis for electromechanically coupled nanodevices. Since wurtzite zinc oxide (ZnO) is structurally noncentral symmetric and has the highest piezoelectric tensor among tetrahedrally bonded semiconductors, therefore it becomes a promising candidate for energy harvesting applications. ZnO is relatively biosafe and biocompatible as well, so it can be used at large scale without any harm to the living environment. The synthesis of another transition metal oxide known as Co3O4 is also important due to its potential usage in the material science, physics and chemistry fields. Co3O4 has been studied extensively due to low cost, low toxicity, the most naturally abundant, high surface area, good redox, easily tunable surface and structural properties. These significant properties enable Co3O4 fruitful for developing variety of nanodevices. Co3O4 nanostructures have been focused considerably in the past decade due to their high electro-chemical performance, which is essential for developing highly sensitive sensor devices. I started my work with the synthesis of ZnO nanostructures with a focus to improve the amount of harvested energy by utilizing oxygen plasma treatment. Then I grow ZnO nanorods on different flexible substrates, in order to observe the effect of substrate on the amount of harvested energy. After that I worked on understanding the mechanism and causes of variation in the resulting output potential generated from ZnO nanorods. My next target belongs to an innovative approach in which AFM tip decorated with ZnO nanorods was utilized to improve the output energy. Then I investigated Co3O4 nanostructures though the effect of anions and utilized one of the nanostructure to develop a fast and reliable pH sensor. Finally to take the advantage of higher degree of redox chemistry of NiCo0O4 compared to the single phase of nickel oxide and cobalt oxide, a sensitive glucose sensor is developed by immobilizing glucose oxidase. However, there were problems with the mechanical robustness, lifetime, output stability and environmental adaptability of such devices, therefore more work is going on to find out new ways and means in order to improve the performance of fabricated nanogenerators and sensors.

Objectif : Déterminer la fiabilité et la précision d’un prototype d’appareil non invasif de mesure de glucose dans le tissu interstitiel, le PGS (Photonic Glucose Sensor), en utilisant des clamps glycémiques multi-étagés. Méthodes : Le PGS a été évalué chez 13 sujets avec diabète de type 1. Deux PGS étaient testés par sujet, un sur chacun des triceps, pour évaluer la sensibilité, la spécificité, la reproductibilité et la précision comparativement à la technique de référence (le Beckman®). Chaque sujet était soumis à un clamp de glucose multi-étagé de 8 heures aux concentrations de 3, 5, 8 et 12 mmol/L, de 2 heures chacun. Résultats : La corrélation entre le PGS et le Beckman® était de 0,70. Pour la détection des hypoglycémies, la sensibilité était de 63,4%, la spécificité de 91,6%, la valeur prédictive positive (VPP) 71,8% et la valeur prédictive négative (VPN) 88,2%. Pour la détection de l’hyperglycémie, la sensibilité était de 64,7% et la spécificité de 92%, la VPP 70,8% et la VPN : 89,7%. La courbe ROC (Receiver Operating Characteristics) démontrait une précision de 0,86 pour l’hypoglycémie et de 0,87 pour l’hyperglycémie. La reproductibilité selon la « Clark Error Grid » était de 88% (A+B). Conclusion : La performance du PGS était comparable, sinon meilleure que les autres appareils sur le marché(Freestyle® Navigator, Medtronic Guardian® RT, Dexcom® STS-7) avec l’avantage qu’il n’y a pas d’aiguille. Il s’agit donc d’un appareil avec beaucoup de potentiel comme outil pour faciliter le monitoring au cours du traitement intensif du diabète. Mot clés : Diabète, diabète de type 1, PGS (Photonic Glucose Sensor), mesure continue de glucose, courbe ROC, « Clark Error Grid». / Objective: To determine the reliability and precision of a prototype of a non-invasive device for continuous measurement of interstitial glucose, the PGS (Photonic Glucose Sensor), using multi-level glycaemic clamp. Methods: The PGS was evaluated in 13 subjects with type 1 diabetes. Two PGS were tested with each subject, one on each triceps, to evaluate the sensitivity, specificity, reproducibility and accuracy compared to the reference technique, the glucose analyzer Beckman®. Each subject was submitted to a multi-level 8 hour glucose clamp at 3, 5, 8 and 12 mmol / L, 2 hours each. Results: The correlation between the PGS and the Beckman® was 0.70. For the detection of hypoglycaemia, the sensitivity was 63.4%, the specificity 91.6%, the positive predictive value (PPV) 71.8% and the negative predictive value (NPV) 88.2%. For the detection of hyperglycaemia, the sensitivity was 64.7% the specificity 92%, the PPV 70.8% and the NPV: 89.7%. The ROC (Receiver Operating Characteristics) curve showed an accuracy of 0.86 and 0.87 for hypoglycaemia and hyperglycaemia respectively. Reproducibility according to the Clark Error Grid was 88% in the A and B zone. Conclusion: The performance of the PGS was comparable or better than other continuous glucose monitoring devices on the market (Freestyle® Navigator, Medtronic Guardian® RT, Dexcom® STS-7) with the advantage that it has no needle. It is therefore an interesting device and hopefully, which could facilitate the monitoring in the intensive treatment of diabetes. Key words: Diabetes, type 1 diabetes, PGS (Photonic Glucose Sensor), ROC curve, Clark Error Grid, continuous glucose monitoring, CGMS.

Objectif : Déterminer la fiabilité et la précision d’un prototype d’appareil non invasif de mesure de glucose dans le tissu interstitiel, le PGS (Photonic Glucose Sensor), en utilisant des clamps glycémiques multi-étagés. Méthodes : Le PGS a été évalué chez 13 sujets avec diabète de type 1. Deux PGS étaient testés par sujet, un sur chacun des triceps, pour évaluer la sensibilité, la spécificité, la reproductibilité et la précision comparativement à la technique de référence (le Beckman®). Chaque sujet était soumis à un clamp de glucose multi-étagé de 8 heures aux concentrations de 3, 5, 8 et 12 mmol/L, de 2 heures chacun. Résultats : La corrélation entre le PGS et le Beckman® était de 0,70. Pour la détection des hypoglycémies, la sensibilité était de 63,4%, la spécificité de 91,6%, la valeur prédictive positive (VPP) 71,8% et la valeur prédictive négative (VPN) 88,2%. Pour la détection de l’hyperglycémie, la sensibilité était de 64,7% et la spécificité de 92%, la VPP 70,8% et la VPN : 89,7%. La courbe ROC (Receiver Operating Characteristics) démontrait une précision de 0,86 pour l’hypoglycémie et de 0,87 pour l’hyperglycémie. La reproductibilité selon la « Clark Error Grid » était de 88% (A+B). Conclusion : La performance du PGS était comparable, sinon meilleure que les autres appareils sur le marché(Freestyle® Navigator, Medtronic Guardian® RT, Dexcom® STS-7) avec l’avantage qu’il n’y a pas d’aiguille. Il s’agit donc d’un appareil avec beaucoup de potentiel comme outil pour faciliter le monitoring au cours du traitement intensif du diabète. Mot clés : Diabète, diabète de type 1, PGS (Photonic Glucose Sensor), mesure continue de glucose, courbe ROC, « Clark Error Grid». / Objective: To determine the reliability and precision of a prototype of a non-invasive device for continuous measurement of interstitial glucose, the PGS (Photonic Glucose Sensor), using multi-level glycaemic clamp. Methods: The PGS was evaluated in 13 subjects with type 1 diabetes. Two PGS were tested with each subject, one on each triceps, to evaluate the sensitivity, specificity, reproducibility and accuracy compared to the reference technique, the glucose analyzer Beckman®. Each subject was submitted to a multi-level 8 hour glucose clamp at 3, 5, 8 and 12 mmol / L, 2 hours each. Results: The correlation between the PGS and the Beckman® was 0.70. For the detection of hypoglycaemia, the sensitivity was 63.4%, the specificity 91.6%, the positive predictive value (PPV) 71.8% and the negative predictive value (NPV) 88.2%. For the detection of hyperglycaemia, the sensitivity was 64.7% the specificity 92%, the PPV 70.8% and the NPV: 89.7%. The ROC (Receiver Operating Characteristics) curve showed an accuracy of 0.86 and 0.87 for hypoglycaemia and hyperglycaemia respectively. Reproducibility according to the Clark Error Grid was 88% in the A and B zone. Conclusion: The performance of the PGS was comparable or better than other continuous glucose monitoring devices on the market (Freestyle® Navigator, Medtronic Guardian® RT, Dexcom® STS-7) with the advantage that it has no needle. It is therefore an interesting device and hopefully, which could facilitate the monitoring in the intensive treatment of diabetes. Key words: Diabetes, type 1 diabetes, PGS (Photonic Glucose Sensor), ROC curve, Clark Error Grid, continuous glucose monitoring, CGMS.