Axe et rotaxane parapluie : vers de nouveaux transporteurs transmembranaires de chlorures et de médicaments cycliques

La membrane cellulaire est principalement une bicouche phospholipidique constituant une barrière qui régule les échanges entre la cellule et son environnement. Son intérieur hydrophobe empêche le passage d’espèces hydrophiles, chargées, de grande masse moléculaire et polaires, qui sont généralement transportées par des protéines à travers la bicouche. Dans certains cas de systèmes défectueux (e.g. les canalopathies), l’équilibre des concentrations en ions à l’intérieur et à l’extérieur des cellules est perturbé et les cellules sont compromises. C’est pourquoi le développement de transporteurs transmembranaires synthétiques est nécessaire. De nombreux travaux ont été faits dans le développement de transporteurs synthétiques d’anions (particulièrement du chlorure). Dans cette thèse, nous présentons nos travaux sur un nouveau transporteur d’anion appelé axe parapluie, capable de changer de conformation dépendamment de la polarité de son environnement. Dans un premier temps, nous avons conçu le design, puis synthétisé ces axes parapluie qui montrent une importante activité en tant que transporteur de chlorures. Ces composés réunissent deux concepts : - Le parapluie, constitué d’acides biliaires amphiphiles (une face hydrophile, une face hydrophobe). La flexibilité des articulations combinée à la grande surface des acides choliques permettent d’empêcher les interactions défavorables entre les parties hydrophiles et hydrophobes, ce qui facilite l’insertion dans la bicouche. - Un site ammonium secondaire en tant que site de reconnaissance, capable de former des ponts hydrogène avec des ions chlorure. De plus, l’axe peut complexer une roue de type éther couronne pour former un pseudo-rotaxane ou rotaxane parapluie ce qui résulte en l’inhibition partielle de leurs propriétés de transport. Ceci nous mène au second objectif de cette thèse, le développement d’un nouveau moyen de transport pour les médicaments cycliques. Certains macrocycles polaires et biologiquement actifs tels que les nactines ont besoin d’atteindre leur objectif à l’intérieur de la cellule pour jouer leur rôle. La membrane cellulaire est alors un obstacle. Nous avons imaginé tirer profit de notre axe parapluie pour transporter un médicament cyclique (en tant que roue d’un rotaxane parapluie). Les assemblages des rotaxanes parapluie furent accomplis par la méthode de clipage. Le comportement de l’axe et du rotaxane parapluie fut étudié par RMN et fluorimétrie. Le mouvement du parapluie passant d’une conformation fermée à exposée dépendamment du milieu fut observé pour le rotaxane parapluie. Il en fut de même pour les interactions entre le rotaxane parapluie et des vésicules constituées de phospholipides. Finalement, la capacité du rotaxane parapluie à franchir la bicouche lipidique pour transporter la roue à l’intérieur de la vésicule fut démontrée à l’aide de liposomes contenant de la α-chymotrypsine. Cette dernière pu cliver certains liens amide de l’axe parapluie afin de relarguer la roue.

Precursors and prices : structuring the Quebec synthetic drug market

Information recueillie sur les marchés des drogues de synthèse est beaucoup moins avancée que les études sur d'autres marchés de drogues illicites. La classification relativement récente des drogues de synthèse comme substances illicites, couplée avec ses caractéristiques distinctes qui empêchent son observation, a entravé le développement d’évaluations complètes et fiables des caractéristiques structurelles des marchés. Le but de cet article est de fournir un aperçu fiable sur la dynamique interne du marché des drogues synthétiques, en particulier sur ses caractéristiques structurelles et organisationnelles. En utilisant l'information obtenue à partir de 365 drogues de synthèse saisies par les policiers pendant un an, cette étude sera la fusion de deux techniques, soit la composition des drogues illicites et des analyses économiques, afin de tirer des évaluations fiables des caractéristiques structurelles du marché du Québec de drogues synthétiques. Les résultats concernant l'analyse de la composition des drogues indiquent que le marché des drogues synthétiques au Québec est probablement composé d'un nombre élevé de petites structures, ce qui indique un marché compétitif. L'analyse économique a également fourni des informations complémentaires sur le marché des drogues. Selon la région géographique les couts de la production et les relations entre trafiquant et consommateur influencent le prix des drogues. Les résultats de cette recherche mettent l'accent sur la nécessité de concevoir des politiques qui tient compte des différences régionales dans la production de drogue et reflète la nature compétitive de ce marché.

Étude des tachykinines et de leurs dérivés peptidiques associés à la douleur neuropathique grâce à l’utilisation de modèles animaux et de la chromatographie en phase liquide couplée à la spectrométrie de masse

Thèse réalisée en co-tutelle avec l'Université Claude Bernard de Lyon 1, en France.

High-amylose carboxymethyl starch matrices for oral sustained drug-release : in vitro and in vivo evaluation

Les amidons non modifiées et modifiés représentent un groupe d’excipients biodégradables et abondants particulièrement intéressant. Ils ont été largement utilisés en tant qu’excipients à des fins diverses dans des formulations de comprimés, tels que liants et/ou agents de délitement. Le carboxyméthylamidon sodique à haute teneur en amylose atomisé (SD HASCA) a été récemment proposé comme un excipient hydrophile à libération prolongée innovant dans les formes posologiques orales solides. Le carboxyméthylamidon sodique à haute teneur en amylose amorphe (HASCA) a d'abord été produit par l'éthérification de l'amidon de maïs à haute teneur en amylose avec le chloroacétate. HASCA a été par la suite séché par atomisation pour obtenir le SD HASCA. Ce nouvel excipient a montré des propriétés présentant certains avantages dans la production de formes galéniques à libération prolongée. Les comprimés matriciels produits à partir de SD HASCA sont peu coûteux, simples à formuler et faciles à produire par compression directe. Le principal objectif de cette recherche était de poursuivre le développement et l'optimisation des comprimés matriciels utilisant SD HASCA comme excipient pour des formulations orales à libération prolongée. A cet effet, des tests de dissolution simulant les conditions physiologiques du tractus gastro-intestinal les plus pertinentes, en tenant compte de la nature du polymère à l’étude, ont été utilisés pour évaluer les caractéristiques à libération prolongée et démontrer la performance des formulations SD HASCA. Une étude clinique exploratoire a également été réalisée pour évaluer les propriétés de libération prolongée de cette nouvelle forme galénique dans le tractus gastro-intestinal. Le premier article présenté dans cette thèse a évalué les propriétés de libération prolongée et l'intégrité physique de formulations contenant un mélange comprimé de principe actif, de chlorure de sodium et de SD HASCA, dans des milieux de dissolution biologiquement pertinentes. L'influence de différentes valeurs de pH acide et de temps de séjour dans le milieu acide a été étudiée. Le profil de libération prolongée du principe actif à partir d'une formulation de SD HASCA optimisée n'a pas été significativement affecté ni par la valeur de pH acide ni par le temps de séjour dans le milieu acide. Ces résultats suggèrent une influence limitée de la variabilité intra et interindividuelle du pH gastrique sur la cinétique de libération à partir de matrices de SD HASCA. De plus, la formulation optimisée a gardé son intégrité pendant toute la durée des tests de dissolution. L’étude in vivo exploratoire a démontré une absorption prolongée du principe actif après administration orale des comprimés matriciels de SD HASCA et a montré que les comprimés ne se sont pas désintégrés en passant par l'estomac et qu’ils ont résisté à l’hydrolyse par les α-amylases dans l'intestin. Le deuxième article présente le développement de comprimés SD HASCA pour une administration orale une fois par jour et deux fois par jour contenant du chlorhydrate de tramadol (100 mg et 200 mg). Ces formulations à libération prolongée ont présenté des valeurs de dureté élevées sans nécessiter l'ajout de liants, ce qui facilite la production et la manipulation des comprimés au niveau industriel. La force de compression appliquée pour produire les comprimés n'a pas d'incidence significative sur les profils de libération du principe actif. Le temps de libération totale à partir de comprimés SD HASCA a augmenté de manière significative avec le poids du comprimé et peut, de ce fait, être utilisé pour moduler le temps de libération à partir de ces formulations. Lorsque les comprimés ont été exposés à un gradient de pH et à un milieu à 40% d'éthanol, un gel très rigide s’est formé progressivement sur leur surface amenant à la libération prolongée du principe actif. Ces propriétés ont indiqué que SD HASCA est un excipient robuste pour la production de formes galéniques orales à libération prolongée, pouvant réduire la probabilité d’une libération massive de principe actif et, en conséquence, des effets secondaires, même dans le cas de co-administration avec une forte dose d'alcool. Le troisième article a étudié l'effet de α-amylase sur la libération de principe actif à partir de comprimés SD HASCA contenant de l’acétaminophène et du chlorhydrate de tramadol qui ont été développés dans les premières étapes de cette recherche (Acetaminophen SR et Tramadol SR). La modélisation mathématique a montré qu'une augmentation de la concentration d’α-amylase a entraîné une augmentation de l'érosion de polymère par rapport à la diffusion de principe actif comme étant le principal mécanisme contrôlant la libération de principe actif, pour les deux formulations et les deux temps de résidence en milieu acide. Cependant, même si le mécanisme de libération peut être affecté, des concentrations d’α-amylase allant de 0 UI/L à 20000 UI/L n'ont pas eu d'incidence significative sur les profils de libération prolongée à partir de comprimés SD HASCA, indépendamment de la durée de séjour en milieu acide, le principe actif utilisé, la teneur en polymère et la différente composition de chaque formulation. Le travail présenté dans cette thèse démontre clairement l'utilité de SD HASCA en tant qu'un excipient à libération prolongée efficace.

Drug-loaded nanocarriers : passive targeting and crossing of biological barriers

Poor bioavailability and poor pharmacokinetic characteristics are some of the leading causes of drug development failure. Therefore, poorly-soluble drugs, fragile proteins or nucleic acid products may benefit from their encapsulation in nanosized vehicles, providing enhanced solubilisation, protection against degradation, and increased access to pathological compartments. A key element for the success of drug-loaded nanocarriers (NC) is their ability to either cross biological barriers themselves or allow loaded drugs to traverse them to achieve optimal pharmacological action at pathological sites. Depending on the mode of administration, NC may have to cross different physiological barriers in their journey towards their target. In this review, the crossing of biological barriers by passive targeting strategies will be presented for intravenous delivery (vascular endothelial lining, particularly for tumour vasculature and blood-brain barrier targeting), oral administration (gastrointestinal lining) and upper airway administration (pulmonary epithelium). For each specific barrier, background information will be provided on the structure and biology of the tissues involved as well as available pathways for nano-objects or loaded drugs (diffusion and convection through fenestration, transcytosis, tight junction crossing, etc.). The determinants of passive targeting − size, shape, surface chemistry, surface patterning of nanovectors − will be discussed in light of current results. Perspectives on each mode of administration will be presented. The focus will be on polymeric nanoparticles and dendrimers although advances in liposome technology will be also reported as they represent the largest body in the drug delivery literature.

Isolation, purification and characterization of Protease Inhibitor from Moringa oleifera Lam.

Protease inhibitors are one of the most important tools of nature for regulating the proteolytic activity of their target proteases. They are synthesized in biological systems and they play a critical role in controlling a number of diverse physiological functions. The current investigation focused on the isolation, purification and characterization of a novel protease inhibitor from Moringa oleifera. The results obtained during the course of study opens new perspectives for the utilization of protease inhibitor from Moringa oleifera for various pharmaceutical, agricultural and food industries. The biological and physicochemical properties exhibited by the novel protease inhibitor from Moringa oleifera clearly testify its suitability for the development as a drug for application in pharmaceutical industries such as anticoagulant agent or biocontrol agent in agriculture and even as a food preservant. There is a scope for further research on the structure elucidation and protein engineering towards a wide range of further applications. Detailed structure/function analysis of these proteins is important to facilitate their use in genetic engineering for various applications.

Realisation of a Target Classifier For Noise Sources in the Ocean

This thesis addresses one of the emerging topics in Sonar Signal Processing.,viz.the implementation of a target classifier for the noise sources in the ocean, as the operator assisted classification turns out to be tedious,laborious and time consuming.In the work reported in this thesis,various judiciously chosen components of the feature vector are used for realizing the newly proposed Hierarchical Target Trimming Model.The performance of the proposed classifier has been compared with the Euclidean distance and Fuzzy K-Nearest Neighbour Model classifiers and is found to have better success rates.The procedures for generating the Target Feature Record or the Feature vector from the spectral,cepstral and bispectral features have also been suggested.The Feature vector ,so generated from the noise data waveform is compared with the feature vectors available in the knowledge base and the most matching pattern is identified,for the purpose of target classification.In an attempt to improve the success rate of the Feature Vector based classifier,the proposed system has been augmented with the HMM based Classifier.Institutions where both the classifier decisions disagree,a contention resolving mechanism built around the DUET algorithm has been suggested.

Underwater Target Localization, Tracking and Classification

Underwater target localization and tracking attracts tremendous research interest due to various impediments to the estimation task caused by the noisy ocean environment. This thesis envisages the implementation of a prototype automated system for underwater target localization, tracking and classification using passive listening buoy systems and target identification techniques. An autonomous three buoy system has been developed and field trials have been conducted successfully. Inaccuracies in the localization results, due to changes in the environmental parameters, measurement errors and theoretical approximations are refined using the Kalman filter approach. Simulation studies have been conducted for the tracking of targets with different scenarios even under maneuvering situations. This system can as well be used for classifying the unknown targets by extracting the features of the noise emanations from the targets.

1st Kassel Student Workshop on Security in Distributed Systems

With this document, we provide a compilation of in-depth discussions on some of the most current security issues in distributed systems. The six contributions have been collected and presented at the 1st Kassel Student Workshop on Security in Distributed Systems (KaSWoSDS’08). We are pleased to present a collection of papers not only shedding light on the theoretical aspects of their topics, but also being accompanied with elaborate practical examples. In Chapter 1, Stephan Opfer discusses Viruses, one of the oldest threats to system security. For years there has been an arms race between virus producers and anti-virus software providers, with no end in sight. Stefan Triller demonstrates how malicious code can be injected in a target process using a buffer overflow in Chapter 2. Websites usually store their data and user information in data bases. Like buffer overflows, the possibilities of performing SQL injection attacks targeting such data bases are left open by unwary programmers. Stephan Scheuermann gives us a deeper insight into the mechanisms behind such attacks in Chapter 3. Cross-site scripting (XSS) is a method to insert malicious code into websites viewed by other users. Michael Blumenstein explains this issue in Chapter 4. Code can be injected in other websites via XSS attacks in order to spy out data of internet users, spoofing subsumes all methods that directly involve taking on a false identity. In Chapter 5, Till Amma shows us different ways how this can be done and how it is prevented. Last but not least, cryptographic methods are used to encode confidential data in a way that even if it got in the wrong hands, the culprits cannot decode it. Over the centuries, many different ciphers have been developed, applied, and finally broken. Ilhan Glogic sketches this history in Chapter 6.

Note on the quasimolecular M radiation in very heavy collision systems

The quasimolecular M radiation emitted in collisions between Xe ions of up to 6 MeV energy and solid targets of Ta, Au, Pb and Bi, as well as a gaseous target of Pb(CH_3)_4, has been studied. Using a realistic theoretical correlation diagram, a semiquantitative explanation of the observed peak structure is given.

Optimizing Robust Quantum Gates in Open Quantum Systems

We are currently at the cusp of a revolution in quantum technology that relies not just on the passive use of quantum effects, but on their active control. At the forefront of this revolution is the implementation of a quantum computer. Encoding information in quantum states as “qubits” allows to use entanglement and quantum superposition to perform calculations that are infeasible on classical computers. The fundamental challenge in the realization of quantum computers is to avoid decoherence – the loss of quantum properties – due to unwanted interaction with the environment. This thesis addresses the problem of implementing entangling two-qubit quantum gates that are robust with respect to both decoherence and classical noise. It covers three aspects: the use of efficient numerical tools for the simulation and optimal control of open and closed quantum systems, the role of advanced optimization functionals in facilitating robustness, and the application of these techniques to two of the leading implementations of quantum computation, trapped atoms and superconducting circuits. After a review of the theoretical and numerical foundations, the central part of the thesis starts with the idea of using ensemble optimization to achieve robustness with respect to both classical fluctuations in the system parameters, and decoherence. For the example of a controlled phasegate implemented with trapped Rydberg atoms, this approach is demonstrated to yield a gate that is at least one order of magnitude more robust than the best known analytic scheme. Moreover this robustness is maintained even for gate durations significantly shorter than those obtained in the analytic scheme. Superconducting circuits are a particularly promising architecture for the implementation of a quantum computer. Their flexibility is demonstrated by performing optimizations for both diagonal and non-diagonal quantum gates. In order to achieve robustness with respect to decoherence, it is essential to implement quantum gates in the shortest possible amount of time. This may be facilitated by using an optimization functional that targets an arbitrary perfect entangler, based on a geometric theory of two-qubit gates. For the example of superconducting qubits, it is shown that this approach leads to significantly shorter gate durations, higher fidelities, and faster convergence than the optimization towards specific two-qubit gates. Performing optimization in Liouville space in order to properly take into account decoherence poses significant numerical challenges, as the dimension scales quadratically compared to Hilbert space. However, it can be shown that for a unitary target, the optimization only requires propagation of at most three states, instead of a full basis of Liouville space. Both for the example of trapped Rydberg atoms, and for superconducting qubits, the successful optimization of quantum gates is demonstrated, at a significantly reduced numerical cost than was previously thought possible. Together, the results of this thesis point towards a comprehensive framework for the optimization of robust quantum gates, paving the way for the future realization of quantum computers.

Efficient Characterisation and Optimal Control of Open Quantum Systems - Mathematical Foundations and Physical Applications

Since no physical system can ever be completely isolated from its environment, the study of open quantum systems is pivotal to reliably and accurately control complex quantum systems. In practice, reliability of the control field needs to be confirmed via certification of the target evolution while accuracy requires the derivation of high-fidelity control schemes in the presence of decoherence. In the first part of this thesis an algebraic framework is presented that allows to determine the minimal requirements on the unique characterisation of arbitrary unitary gates in open quantum systems, independent on the particular physical implementation of the employed quantum device. To this end, a set of theorems is devised that can be used to assess whether a given set of input states on a quantum channel is sufficient to judge whether a desired unitary gate is realised. This allows to determine the minimal input for such a task, which proves to be, quite remarkably, independent of system size. These results allow to elucidate the fundamental limits regarding certification and tomography of open quantum systems. The combination of these insights with state-of-the-art Monte Carlo process certification techniques permits a significant improvement of the scaling when certifying arbitrary unitary gates. This improvement is not only restricted to quantum information devices where the basic information carrier is the qubit but it also extends to systems where the fundamental informational entities can be of arbitary dimensionality, the so-called qudits. The second part of this thesis concerns the impact of these findings from the point of view of Optimal Control Theory (OCT). OCT for quantum systems utilises concepts from engineering such as feedback and optimisation to engineer constructive and destructive interferences in order to steer a physical process in a desired direction. It turns out that the aforementioned mathematical findings allow to deduce novel optimisation functionals that significantly reduce not only the required memory for numerical control algorithms but also the total CPU time required to obtain a certain fidelity for the optimised process. The thesis concludes by discussing two problems of fundamental interest in quantum information processing from the point of view of optimal control - the preparation of pure states and the implementation of unitary gates in open quantum systems. For both cases specific physical examples are considered: for the former the vibrational cooling of molecules via optical pumping and for the latter a superconducting phase qudit implementation. In particular, it is illustrated how features of the environment can be exploited to reach the desired targets.

Model-Based Troubleshooting of Digital Systems

This thesis describes a methodology, a representation, and an implemented program for troubleshooting digital circuit boards at roughly the level of expertise one might expect in a human novice. Existing methods for model-based troubleshooting have not scaled up to deal with complex circuits, in part because traditional circuit models do not explicitly represent aspects of the device that troubleshooters would consider important. For complex devices the model of the target device should be constructed with the goal of troubleshooting explicitly in mind. Given that methodology, the principal contributions of the thesis are ways of representing complex circuits to help make troubleshooting feasible. Temporally coarse behavior descriptions are a particularly powerful simplification. Instantiating this idea for the circuit domain produces a vocabulary for describing digital signals. The vocabulary has a level of temporal detail sufficient to make useful predictions abut the response of the circuit while it remains coarse enough to make those predictions computationally tractable. Other contributions are principles for using these representations. Although not embodied in a program, these principles are sufficiently concrete that models can be constructed manually from existing circuit descriptions such as schematics, part specifications, and state diagrams. One such principle is that if there are components with particularly likely failure modes or failure modes in which their behavior is drastically simplified, this knowledge should be incorporated into the model. Further contributions include the solution of technical problems resulting from the use of explicit temporal representations and design descriptions with tangled hierarchies.

Targeted Stimuli-Responsive Dextran Conjugates for Doxorubicin Delivery to Hepatocytes

A targeted, stimuli-responsive, polymeric drug delivery vehicle is being developed in our lab to help alleviate severe side-effects caused by narrow therapeutic window drugs. Targeting specific cell types or organs via proteins, specifically, lectin-mediated targeting holds potential due to the high specificity and affinity of receptor-ligand interactions, rapid internalization, and relative ease of processing. Dextran, a commercially available, biodegradable polymer has been conjugated to doxorubicin and galactosamine to target hepatocytes in a three-step, one-pot synthesis. The loading of doxorubicin and galactose on the conjugates was determined by absorbance at 485 nm and elemental analysis, respectively. Conjugation efficiency based on the amount loaded of each reactant varies from 20% to 50% for doxorubicin and from 2% to 20% for galactosamine. Doxorubicin has also been attached to dextran through an acid-labile hydrazide bond. Doxorubicin acts by intercalating with DNA in the nuclei of cells. The fluorescence of doxorubicin is quenched when it binds to DNA. This allows a fluorescence-based cell-free assay to evaluate the efficacy of the polymer conjugates where we measure the fluorescence of doxorubicin and the conjugates in increasing concentrations of calf thymus DNA. Fluorescence quenching indicates that our conjugates can bind to DNA. The degree of binding increases with polymer molecular weight and substitution of doxorubicin. In cell culture experiments with hepatocytes, the relative uptake of polymer conjugates was evaluated using flow cytometry, and the killing efficiency was determined using the MTT cell proliferation assay. We have found that conjugate uptake is much lower than that of free doxorubicin. Lower uptake of conjugates may increase the maximum dose of drug tolerated by the body. Also, non-galactosylated conjugate uptake is lower than that of the galactosylated conjugate. Microscopy indicates that doxorubicin localizes almost exclusively at the nucleus, whereas the conjugates are present throughout the cell. Doxorubicin linked to dextran through a hydrazide bond was used to achieve improved killing efficiency. Following uptake, the doxorubicin dissociates from the polymer in an endosomal compartment and diffuses to the nucleus. The LC₅₀ of covalently linked doxorubicin is 7.4 μg/mL, whereas that of hydrazide linked doxorubicin is 4.4 μg/mL.

An hybrid methodology for RL-based behavior coordination in a target following mission with an AUV

Proposes a behavior-based scheme for high-level control of autonomous underwater vehicles (AUVs). Two main characteristics can be highlighted in the control scheme. Behavior coordination is done through a hybrid methodology, which takes in advantages of the robustness and modularity in competitive approaches, as well as optimized trajectories