L'exaltation de fluorescence par un métal est de plus en plus utilisée pour augmenter la sensibilité de détection dans les systèmes utilisant la fluorescence. Au cours de ce travail de thèse, nous avons étudié ce phénomène dans des nanoparticules hybrides Métal@SiO2 possédant des émetteurs de fluorescence immobilisés sur la silice. Dans un premier temps, nous avons élaboré les nanoparticules cœur-coquille Métal@SiO2 (Métal = Au ou Ag) en utilisant différentes méthodes et en les comparant pour choisir la plus adaptée selon le diamètre du cœur métallique. Dans un deuxième temps, nous avons étudié les propriétés de fluorescence exaltée des nanoparticules hybrides. Deux types d'émetteurs de fluorescence ont été sélectionnés : des nanoparticules semi-conductrices (SiC) et des fluorophores organiques (cyanine 3 et fluorescéine). Après fonctionnalisation de la silice, les émetteurs de fluorescence ont été greffés à la surface des nanoparticules Métal@SiO2. L'exaltation de leur fluorescence a été analysée en fonction de leur densité surfacique, de leur distance par rapport au cœur métallique (fixée par l'épaisseur de silice), du diamètre du cœur métallique et de la longueur d'onde d'excitation. Le facteur d'exaltation le plus important (de l'ordre de 103) a été obtenu avec une faible épaisseur de silice (10 nm) pour les nanoparticules de SiC dont le rendement quantique intrinsèque est très faible (inférieur à 1%). Enfin, la surface de nanoparticules hybrides a été fonctionnalisée avec des nanoparticules d'oxyde de fer de manière à obtenir une combinaison de propriétés optiques (fluorescentes et plasmoniques) et magnétiques à l'intérieur d'une même nanoparticule hybride.

The design and development of a versatile time resolved fluorescence spectroscopy (TRFS) system capable of near real time data acquisition and processing for potential clinical diagnostic applications is reported. The TRFS apparatus is portable, versatile and compatible with the clinical environment. The main excitation source is a UV nitrogen laser with a nanosecond pulse width and the detection part consists of a dual grating spectrograph coupled with an MCP-PMT. The nitrogen laser also has a dye module attached to it, which enables broadband excitation of the sample. This setup allows rapid acquisition (250 ms for fluorescence decay at a wavelength) of time resolved fluorescence data with a high spectral (as low as 0.5 nm) and temporal (as low as 25 picoseconds) resolution. Alternatively, a state diode pumped pulsed laser can be used for excitation to improve data collection speed. The TRFS system is capable of measuring a broad range of fluorescence emission spectra (visible to near infra-red) and resolving a broad range of lifetimes (ranging from a few hundred picoseconds to several microseconds). The optical setup of the system is flexible permitting the connection of different light sources as well as optical fiber based probes for light delivery/collection depending on the need of the application. This permits the use of the TRFS apparatus in in vitro, ex vivo and in vivo applications. The system is fully automated for real-time data acquisition and processing, facilitating near-real time clinical diagnostic applications.

The design of chromophores targets materials with optoelectronic properties necessary for advanced applications. Organic materials possess properties which emerge from the collective impact of the constituent backbone and substituents as well as their connectivity (i.e. molecular architecture), necessitating the exploration of novel conjugated architectures. This thesis chronicles our examination of 1,4-distyryl-2,5-bis(arylethynyl)benzenes (cruciforms, XFs). Electronic substitution of this 'X-shaped' cross-conjugated scaffold tunes both the energy levels and the spatial distribution of the frontier molecular orbitals (FMOs) in XFs. The resulting fluorophores exhibit FMO separation, imbuing XFs with desirable properties for sensory applications. Using model analytes, we examine how the underlying FMO arrangement and the nature of analyte interaction elicit observable responses. These studies provide a foundation for future access of functional responsive ratiometric cores. This case study demonstrates the importance and unique potential of FMO-separated fluorophores.

The synthesis and development of new materials and the improvement of the existing materials are a continuous quest for scientists. There is a constant need for new materials that have more advantages over the existing ones. The research to develop new materials can be appreciated in high magnitude, as the new materials improve the livelihood. In this dissertation, we are presenting our progress in developing new materials, such as fluorescence fluorophores as probes, and esterification catalysts. In the first part of the dissertation, the synthesis and characterization of a novel silicon analog of fluorescein (silyl fluorescein) was studied in detail. The photo-physical properties and toxicity studies of these fluorophores are also discussed. Compared to fluorescein, silyl fluorescein displayed a 90 nm longer wavelength in its absorption and emission. Silyl fluorescein showed good solubility in water and organic solvents, and has a considerable fluorescence quantum yield compared to fluorescein. Silyl fluorescein was found to be moderately toxic under light and non-toxic in dark, where as fluorescein toxicity was found to be greater than silyl fluorescein both in the dark and under light. Two probes from our novel silyl fluorescein fluorophore were developed and studied. SIF HySOx is probe for hypochlorous acid (HOCl), which is a reactive oxygen species (ROS) found in cells that are stressed due to various diseases. The HOCl probe was synthesized and its photo-physical properties were studied. It was found to be selective and sensitive only to HOCl. A fluoride probe (DTBDMS SIF P) was also developed from silyl fluorescein. Its synthesis and photo-physical properties were also studied. The probe displayed excellent selectivity and sensitivity to fluoride (TBAF) in the presence of other halides and bases. Future directions on novel fluorophore are briefly mentioned. Second part of the dissertation is focused on the screening of two organic esterification catalysts which were synthesized by Dr. Liu and Dr. Wong. The catalysts which are synthesized from pyridine and dinitrobenzene moieties were screened with several carboxylic acids and alcohols. Catalyst 8-4 was shown to be moderately active in the esterification of carboxylic acids and alcohols. It has no selectivity in the esterification of primary, secondary, tertiary alcohols, and the carboxylic acids that are attached to those carbons. Catalyst 9-1 however, was more efficient in the esterification of carboxylic acids and alcohols. Catalyst 9-1 displayed selectivity in the esterification of primary, over secondary, over tertiary alcohols, and the carboxylic acids that are attached to those carbons. Catalyst 9-1 gave up to 95% isolated yields.

Nanoesferas de sílica contendo fluoróforos encapsulados (o complexo quercetina- Al+3 e o corante rodamina B) foram preparadas com alto controle de tamanho e morfologia, utilizando catálise ácida e básica do tetraetilortossilicato (TEOS). As nanopartículas obtidas apresentaram diâmetro da ordem de 200-300 nm, possuindo maior regularidade quando preparadas em meio alcalino. Nas preparações foram utilizados o método de Stöber e o método caroço-casca. Devido à hidrólise da quercetina em meio básico, as partículas funcionalizadas com o flavonóide ou com o complexo quercetina-Al+3, apresentaram maior intensidade de emissão sob catálise ácida. No caso da catálise básica, as partículas apresentaram emissão significativa quando preparadas utilizando um sol de alumina, porém foram obtidos paralelepípedos nanométricos. Os decaimentos de fluorescência para o sistema quercetina-alumina são biexponenciais, em concordância com os dois complexos quercetina-Al+3 formados no interior da nanopartícula de sílica. No caso da rodamina B, foram realizadas medidas de espectroscopia de correlação de fluorescência, que mostraram uma relação entre relaxação difusional com tamanho e autoagregação das partículas. / Silica nanospheres doped with quercetin-Al+3 and rhodamine B were synthesized with high size control and morphology, using acid and basic catalysis of tetraethylorthosilicate (TEOS). The nanoparticle diameter obtained was about 200- 300 nm, with higher regularity when synthesized in alkaline media. The Stöber\'s and core-shell methods were used as preparation methods. Because the alkaline hydrolysis of quercetin, the flavonoid or the quercetin-Al+3 complex doped nanoparticles showed higher emission intensity when acid catalysis was used. When basic catalysis was performed, the particles prepared with an alumina-sol showed expressive emission intensity, but nanometric parallelepipeds were obtained. The quercetin-alumina fluorescence decays are biexponential, agreeing with the two types of quercetin-Al+3 complexes formed in the nanoparticles domain. In the case of rhodamine B, fluorescence correlation spectroscopy (FCS) measurements were performed, showing a relation between diffusion relaxation with size and aggregation behavior.

No description available.

Les espaceurs auto-immolables sont des assemblages moléculaires inactifs permettant de découpler deux entités chimiques A (un groupe protecteur subissant une activation) et B (un composé d'intérêt, tel qu'un principe actif, un rapporteur ou un autre espaceur) par des liaisons covalentes. Sous l'effet d'un stimulus externe (activation), A est clivé spontanément lors d'un processus irréversible appelé auto-immolation, qui provoque la libération de l'espèce B. Cette dernière est généralement inactive lorsqu'elle est intégrée dans l'espaceur ; en revanche, une fois libérée, elle retrouve son activité intrinsèque.La cinétique du processus d'auto-immolation contrôle la corrélation spatio-temporelle existant entre l'activation et la libération de la substance active. L'objectif principal de ce travail a été précisément de fournir un ensemble complet de données permettant d'établir des relations structure/propriétés cinétiques fiables dans une série d'espaceur auto-immolable contenant une structure aromatique portant un substituant hydroxyle et s'appuyant sur un mécanisme impliquant une cascade électronique. Ainsi, nous avons utilisé un groupe photactivable et la lumière pour déclencher le processus d'auto-immolation d'une grande banque d'espaceurs auto-immolables, qui présentent un temps caractéristique d'auto-immolation s'étalant sur un large éventail d'échelle de temps (10-4-104s).Au cours de ce travail, nous avons également développé des espaceurs auto-immolables, qui libérent deux composés après activation. Ces systèmes ont été mis en ¿uvre pour répondre à l'analyse quantitative d'un substrat libéré par photodéprotection dans les systèmes biologiques. / Self-immolative spacers are inactive molecular assemblies decoupling two chemical entities A (a protecting group undergoing activation) and B (a compound of interest such as a drug, a reporter or another spacer) via covalent bonds. Under the effect of an external stimulus (activation), A is cleaved thus spontaneously initiating an irreversible process called self-immolation, which ultimately causes the release of the species B. The latter is usually inactive by binding on the spacer but, once released, it recovers its intrinsic activity. The kinetics of the self-immolation process controls the spatiotemporal correlation existing between activation and release of the active compound. Although many kinetic studies have been already reported on various series of self-immolative spacers, literature still lacked homogeneous information permitting comparative analysis of the kinetics of self-immolation. The major aim of this work was precisely to provide an extensive set of data drawing reliable structure property relationships in a series of self-immolative spacers containing an aromatic structure bearing a hydroxyl substituent and relying on a mechanism involving an electronic cascade. Thus we used a photactivable group and light to trigger the disassembly process of a large collection of self-immolative spacers, which exhibit self-immolation time varying over a wide range of time scale (10-4-104s). During this work, we also developed self-immolative spacers, which could release two compounds after a single activation. These systems have been implemented to address the quantitative analysis of a substrate released by uncaging in biological systems.

No description available.

No description available.

La fluorescence excitée à deux photons est actuellement largement utilisée pour l’imagerie de tissus biologiques, mais la faible sensibilité des fluorophores utilisés en microscopie confocale (excitation à un photon) à une excitation à deux photons (ADP) rend nécessaire la conception et la synthèse de nouveaux fluorophores spécifiques pour la microscopie de fluorescence par excitation bi-photonique (MFEB). Mon travail de thèse a ainsi porté sur l’ingénierie moléculaire (conception, synthèse et caractérisations) de nouveaux fluorophores pour la MFEB. Nous nous sommes particulièrement intéressés à des systèmes unidimensionnels (1D) de petite taille comportant des systèmes π étendus autour d’un cœur rigide (dicétopyrrolopyrrole ou DPP) et entourés de différents systèmes électro-actifs. Nous avons modifié par la suite les fluorophores précédents de manière à pouvoir les conjuguer à des molécules d’intérêt biologique, comme des protéines. Ces fluorophores bio-conjugables ont été greffés sur un peptide du virus HIV étudié au laboratoire : TAT (Trans-Activator of Transcription). L’imagerie par microscopie biphotonique a été effectuée avec succès sur des cellules HeLa. Nous nous sommes ensuite tourné vers la mise au point de nouvelles sondes multimodales pour associer la MEBP à une autre modalité d’imagerie : la résonance magnétique nucléaire et la microscopie électronique (imagerie corrélative). Pour ce faire nous avons développé des colorants fluorescents par excitation bi-photonique comportant une entité paramagnétique ou dense aux électrons (nanoparticules de magnétite, ion gadolinium III ou atomes lourds comme le platine et l’or). / Two-photon induced fluorescence is nowadays widely used for the imaging of biological tissues. The classical fluorophores used in confocal microscopy exhibit low sensitivity to two-photon excitation for the two-photon excitation microscopy (TPEM), led the researchers towards the development of new fluorophores, specifically engineered for TPEM. This manuscript describes our work on conception, synthesis and characterizations of new one-dimensional fluorophores based on dicétopyrrolopyrrole (DPP) central core, surrounded by various electro-active systems through π conjugated systems. We also modified such fluorophores to be able to conjugate them to molecules of biological interest, such as proteins. These bio-conjugable fluorophores were grafted on a peptide of HIV virus studied in our laboratory: TAT (Trans-Activator of transcription). The imaging by TPEM was successfully performed on HeLa cells. In addition we developed new multimodal probes for the correlative light electronic microscopy and for the correlative imaging fluorescence microscopy/ Magnetic resonance imaging (MRI). Theses multimodal probes associate a fluorescent moiety based on the DPP core associated to a paramagnetic or electron dense entity (magnetite nanoparticles, gadolinium III or heavy atoms such as platinum or gold).