Creating high resolution, or high-density, electrode arrays may be the key for improving cochlear implant users' speech perception in noise, comprehension of lexical languages, and music appreciation. Contemporary electrode arrays use multipolar stimulation techniques such as current steering (shifting the spread of neural excitation in between two physical electrodes) and current focusing (narrowing of the neural spread of excitation) to increase resolution and more specifically target the neural population. Another approach to increasing resolution incorporates microelectromechanical systems (MEMS) fabrication to create a thin film microelectrode (TFM) array with a series of high density electrodes. Validating the benefits of high density electrode arrays requires a systems-level approach. This hypothesis will be tested computationally via cochlea and auditory nerve simulations, and in vitro studies will provide structural proof-of-concept. By employing Rattay's activating function and entering it into Litvak's neural probability model, a first order estimation model was obtained of the auditory nerve's response to electrical stimulation. Two different stimulation scenarios were evaluated: current steering vs. a high density electrode and current focusing of contemporary electrodes vs. current focusing of high density electrodes. The results revealed that a high density electrode is more localized than current steering and requires less current. A second order estimation model was also created COMSOL, which provided the resulting potential and current flow when the electrodes were electrically stimulated. The structural tests were conducted to provide a proof of concept for the TFM arrays' ability to contour to the shape of the cochlea. The TFM arrays were integrated with a standard insertion platform (IP). In vitro tests were performed on human cadaver cochleae using the TFM/IP devices. Fluoroscopic images recorded the insertion, and post analysis 3D CT scans and histology were conducted on the specimens. Only three of the ten implanted TFM/IPs suffered severe delamination. This statistic for scala vestibuli excursion is not an outlier when compared to previous data recorded for contemporary cochlear electrode arrays.

Des études in vitro ont été menées pour évaluer les effets biologiques potentiels de deux types d'ondes radiofréquences. Dans une première partie, nous avons étudié les ondes radiofréquences (300 et 500 MHz) utilisées en imagerie médicale à haute résolution (IRM). Ces ondes sont en régime impulsionnel (de l'ordre de la milliseconde) et avec des puissances crêtes élevées (E= 1.8 kV/m). Toutefois, il n'existe actuellement aucune donnée dans la littérature sur l'impact biologique éventuel de ce type de signaux. Dans ce travail de thèse des cellules gliales humaines (U251 MG) en culture ont été exposées pendant 45 minutes, ou 2 heures, en condition athermique, et plusieurs analyses biologiques ont été réalisés : expression génique d'une batterie de gènes biomarqueurs du stress cellulaire et analyse par microscopie de l'intégrité cellulaire. Quel que soit le test utilisé, les résultats ont toujours été négatifs. Ceci montre qu'aucun stress cellulaire n'a eu lieu lors de l'exposition des cellules à une onde électromagnétique de 300 ou 500 MHz, de forte puissance crête. La seconde partie de ce travail de thèse porte sur l'évaluation des effets des ondes millimétriques (OMM) à 60,4 GHz, en cas de stress énergétique. Nous avons étudié l'impact de l'exposition aux OMM, en présence ou en absence de 2-déoxy-glucose, sur la production d'ATP, le potentiel redox (NADPH) et l'expression génique. Par une approche transcriptomique, nous avons observé qu' un traitement au 2-déoxy-glucose, induit une forte réponse cellulaire. La co-exposition aux OMM modifie faiblement cette réponse génique (4 gènes sur 523 semblent être différentiellement exprimés). Par contre, l'exposition est sans effet sur le potentiel redox ou sur la production d'ATP. / In vitro studies were conducted to evaluate the biological effects of two types of radiofrequency waves. In the first part, we studied the radiofrequency (300 and 500 MHz) used in medical imaging at high resolution (MRI). These radio waves are pulsed (millisecond) with strong peaks power (E = 1.8 kV/m). However, there is currently no data in the literature, on the potential biological impact of such signals. This thesis examines whether exposure to this type of signal, may or may not, trigger a cellular stress. Human glial cells (U251 MG) in culture were exposed for 45 minutes or 2 hours in athermal conditions, and several biological tests were performed: gene expression of stress biomarkers or cell integrity by Cellomics technology. Whatever the test used, no significant modification was observed between the control and the exposed cells. This strongly suggests that no cellular stress occurred during the exposure of cells to high peak power RF pulses. The second part of this thesis specifically examines the effect of millimeter waves (MMW) at 60.4 GHz in cells deprived from glucose. We investigated whether exposure to MMW, in the presence or absence of 2-deoxy-glucose has an effect on ATP production, redox potential (NADPH) and gene expression. We found no genes differentially expressed between the sham control and the exposed cells. In contrast, when cells are submitted to a metabolic stress (treated with 2dG), we found that MMW radiation significantly modifies the gene expression (4 genes out of 523 are differentially expressed). However, OMM exposure has no effect on the redox potential or ATP production.

Orientador: Ana Paula Rosifini Alves Claro / Resumo: Titânio e suas ligas têm sido amplamente aplicados em materiais biomédicos devido as suas excelentes propriedades de volume (relação massa específica e resistência mecânica), biocompatibilidade e resistência à corrosão. As ligas de titânio utilizadas comercialmente são a Ti CP (comercialmente puro) e Ti6Al4V e apesar de muito utilizadas apresentam problemas de citotoxicidade e dessa maneira se faz importante o desenvolvimento de novas ligas que levem a substituição das mesmas. Ligas de titânio do tipo beta têm sido amplamente exploradas devido a sua excelente relação baixo peso específico e módulo de elasticidade, fator que reduz o efeito de Stress Shielding. O objetivo deste trabalho foi processar e caracterizar uma liga de titânio do tipo beta com composição Ti10Mo8Nb6Zr (%m) visando aplicações biomédicas. Os lingotes da liga foram obtidos em um forno de fusão a arco voltaico com atmosfera inerte de gás argônio. A liga foi tratada em um forno tubular a vácuo a 1000ºC por 24 horas para garantir a homogeneidade química, forjada a frio em barras de 9,60 mm de diâmetro e tratadas termicamente novamente a 950°C por 2 horas, seguido de resfriamento em água. A microestrutura e as fases presentes de cada etapa do processamento da liga foram investigadas por Microscopia Óptica (MO), Difração de Raios X (DRX) e Calorimetria Exploratória Diferencial (DSC). Sendo possível constatar a presença da fase beta e a presença de uma possível fase metaestável a ω, comprovando o diagrama de prev... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Titanium and its alloys have been widely applied in biomedical materials because of their excellent volume properties (specific mass ratio and strength), biocompatibility and corrosion resistance. The titanium alloys used commercially are Ti CP (commercially pure) and Ti6Al4V, although they are widely used they present problems of cytotoxicity (Ti6Al4V) and high Young's modulus (Ti CP) and in this way it is important to develop new alloys that lead to their replacement. Beta-type titanium alloys have been extensively explored because of their excellent low specific weight ratio and low modulus of elasticity, which reduces the effect of Stress Shielding, besides absence of problems with citotoxicity. The purpose of this study was processing and characterization of the new beta-titanium alloy Ti10Mo8Nb6Zr (%wt) for biomedical applications. The ingots were obtained in an eletric arc furnace with an inert atmosphere of argon gas. They were heat treated in a tubular vacuum furnace at 1000°C for 24 hours to ensure chemical homogeneity, cold worked in rods with 9.60 mm diameter, and solubilized in tubular furnace under vacuum at 950°C for 2 hours followed by cooling in water. The microstructure and the phases present in each step of the alloy processing were investigated by The microstructure and the phases present at each step of the processing of the alloy were investigated by optical microscopy, X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). It was possible ... (Complete abstract click electronic access below) / Mestre

Le récepteur humain de la mélatonine MT1 appartient à la famille des récepteurs couplés aux protéines G (RCPG). En raison du rôle majeur qu'il joue dans la régulation du rythme circadien, ce récepteur est impliqué dans les troubles du sommeil et la dépression et présente donc un intérêt thérapeutique important. Afin de progresser vers une meilleure caractérisation structurale et fonctionnelle de ce récepteur, nous avons élaboré une stratégie globale visant à générer les échantillons et méthodes nécessaires pour de telles études. Nous avons ainsi mis au point un ensemble original de conditions de production et de purification permettant d'isoler les récepteurs MT1 sous forme relativement pure, homogène et fonctionnelle. Parallèlement, à partir d'un RCPG de référence, le récepteur de l’adénosine A2A, nous avons mis au point un panel de techniques d’analyses biochimiques et biophysiques qui contribuent à une caractérisation fine des récepteurs purifiés et leur interaction avec des ligands. / The human MT1 melatonin receptor belongs to the family of G protein-coupled receptors (GPCRs). It plays a major role in the regulation of circadian rhythm and is involved in sleep disorders and depression. This receptor is thus of significant therapeutic interest. However, very few in vitro studies have been conducted on this receptor and in particular no structural characterization and interactio studies by biophysical methods. In order to progress on these aspects, we developed conditions of production and purification of MT1 receptors for obtaining samples compatible with this type of study. Furthermore, we initiated stabilization tests of the purified receptors. Meanwhile, we have developed biochemical and biophysical analysis techniques to characterize the purified receptors and study their interactions with ligands, on a reference GPCR, the A2A adenosine receptor.

Ce travail décrit de nouveaux composés thérapeutiques anticancéreux traçables par imagerie optique appelés théranostiques optiques.Après un premier chapitre bibliographique décrivant le contexte de l’imagerie et la thérapie des cancers, un deuxième chapitre présente une première série de théranostiques BODIPY-phosphine-or dont la synthèse a été optimisée (diminution du nombre d’étapes, baisse du temps de réaction, compatibilité avec une augmentation d’échelle). Leur conjugaison à des biomolécules (glucose, peptide) a été réalisée par une méthode simple et efficace par couplage entre l’atome d’or de la sonde et la fonction thiol de la biomolécule (modifiée ou non), conduisant à une liaison or-soufre. Elle permet une biovectorisation pour rendre les composés plus sélectifs des cellules tumorales vis à vis des cellules saines. Les études photophysiques et biologiques réalisées ont démontré tout le potentiel de ces théranostiques dans le cadre d’un suivi de composé in vitro et l’impact que pouvait avoir le vecteur choisi.Le troisième chapitre présente deux autres séries de théranostiques et précurseurs visant deux objectifs distincts pour rendre la sonde plus compatible avec une imagerie optique in vivo. La modification structurale de la plateforme BODIPY par introduction de groupements augmentant la conjugaison permet d’obtenir des BODIPYs absorbant et émettant dans la « fenêtre thérapeutique » (650 900 nm, proche infrarouge). Des études préliminaires in vivo ainsi que des tests en imagerie photoacoustique ont donné des résultats prometteurs. Une deuxième modification structurale par introduction de groupements encombrants sur chaque face du BODIPY vise à empêcher l’agrégation des BODIPYs en milieu biologique (phénomène connu pour affecter leurs propriétés optiques). Cette approche « Picket-Fence » des porphyrines transposée en série BODIPY a permis d’appliquer pour la première fois en série BODIPY le concept d’atropoisomérie et d’atropoisomères interconvertibles. / This work describes new anticancer agents that could be detected by optical imaging, namely optical theranostics.After a first chapter describing the context of cancer imaging and therapy, a second chapter describes a first series of BODIPY-phosphine-gold theranostics, the synthesis of which has been optimized (less steps, shortening the reaction time, scale up). Their conjugation with biomolecules (glucose, peptide) has been achieved by developing a simple and efficient method that leads to the coupling between the gold atom of the probe and the thiol of the biomolecule (modified or not), leading to a gold sulfur bound. Hence, it makes the biovectorization of the probes possible in order to get selectivity against tumor cells compared with healthy cells. Subsequent photophysical and biological studies demonstrated the potential of such theranostics, such as in vitro monitoring, and the impact of a chosen biomolecule (vector).A third chapter presents two additional series of theranostics and precursors with two distinct objectives aimed at making the probe more suitable for in vivo optical imaging. A first structural modification of the BODIPY platform was achieved upon introducing chemical groups allowing an extention of the π conjugation. It leads to BODIPYs that absorb and emit in the « therapeutic window » (650 900 nm, NIR). Preliminary in vivo studies and preliminary photoacoustic imaging studies with such compounds led to promising results. A second structural modification upon introducing bulky groups on each face of the probe was aimed at preventing stacking of BODIPYs platforms in biological media (a phenomenon known to affect their optical properties). Hence, a porphyrin « Picket Fence » approach was successfully transposed to BODIPY together with the concept of atropisomery and atropisomer interconversion.