Oxido nítrico (NO) é uma molécula que participa de várias atividades fisiológicas no organismo, entre as quais incluem-se ação vasodilatadora e antitumoral. Entretanto sua resposta biológica é dependente da concentração, que quando alta apresenta citotoxicidade. Um fator limitante para sua aplicação em sistemas biológicos é seu curto tempo de meia vida no organismo, o que direcionou os estudos de complexos de rutênio-nitrosilo (RuNO) como doadores de NO. Complexos RuNO apresentam interesse especial devido suas propriedades termoestáveis e fotoquímicas. O uso da luz como um estímulo externo torna-se vantajoso pela capacidade de controlar-se a localização, o tempo de liberação da droga e a dosagem. A terapia fotodinâmica (TFD) tem sido aplicada na terapia clínica contra o câncer. TFD depende da concentração de oxigênio para a produção de espécies reativas, o que é limitado em alguns tipos de tumores devido a hipóxia. Os Pontos quânticos (PQs), semicondutor nanocristalino, destacam-se como materais funcionais com propriedade ópticas únicas dependentes do tamanho. Podem atuar como antenas na captação de luz e fotossensibilização de complexos rutênio-nitrosilo para a liberação de moléculas bioativas. Neste trabalho descrevemos a síntese e caracterização de diferentes PQs (CdS, CdSe e CdTe) utilizando diferentes agentes passivantes (ATG, TOPO e AMP)e a síntese e caracterização do complexo rutênio-nitrosilo cis-[Ru(NO)(4-amp)(bpy)2]3+ (4-amp= 4-aminopiridina; bpy = 2,2 \'bipiridina. Estudos das propriedades fotofísicas e avaliação fotoquímica da interação entre PQ e RuNO foram realizados como também a avaliação da atividade citotóxica x desta associação sobre cultura de células de melanoma murino B16-F10. As medidas das propriedades fotofísicas demonstraram interação pela supressão da fluorescência analisada pela equação de Stern-Volmer. Pela determinação do número de sítios de ligação (≈ 2) e a constante de ligação (kb) verificou-se que a interação entre as espécies apresentaram supressão da emissão em um gráfico não linear de Stern-Volmer resultante do processo de agregação entre os compostos. Os dados obtidos corroboram para o mecanismo proposto, demonstrando que cada PQ540 interage com duas moléculas de RuNO. Ainda observou-se que, sob irradiação na região do visível, em 532 nm, aumenta-se o número de mols de NO liberado de no mínimo 6 vezes quando irradiado na presença de PQs comparado à irradiação do complexo sozinho em solução. O processo de transferência eletrônica fotoinduzida foi proposto como o mecanismo fotoquímico para a liberação de NO, enquanto que o processo de transferência de energia mostrou-se desfavorável devido a não sobreposição entre os espectros de absorção do complexo nitrosilo e o espectro de emissão do PQ. As análises de imagem fluorescentes demonstraram o potencial dos PQs como marcadores celulares. As concentrações utilizadas nos experimentos não demonstraram toxicidade sobre as células de melanoma murino na ausência de luz. Porém quando irradiadas, apresentaram citotoxicidade parcial. Portanto, essa transferência pode ocorrer pela redução do NO+ para NO0, seguida pela liberação de NO ou por fotoaquação e consequente fotoredução do nitrito em solução. / Nitric oxide (NO) is a molecule involved in many physiological activities in human body among them include vasodilator and antitumoral. However, the biological response is concentration dependent and in high concentrations it causes cytotoxicity. A limiting factor for biological applications is the short half-life of NO in the body which has led to the research of nitrosyl ruthenium complexes (RuNO) as NO donors. RuNO complexes are of special interest because of their thermal stability and photochemical properties. The use of light as an external stimulus is advantageous as we can track the location, timing of drug release and dosage. Photodynamic therapy (PDT) has been used in clinical therapy for cancer treatment. PDT depends on oxygen concentrations for reactive oxygen species production what is limited in some types of tumors because of hypoxia. The Quantum dots (QDs), semiconductor nanocrystal, as functional materials, possess unique optical size-dependent properties. QDs can act as antennas in capturing light and photosensitizing ruthenium- nitrosyl complexes for release of bioactive molecules. In this work we describe the synthesis and characterization of different PQs (CdS, CdSe and CdTe) using different passivating agents (TGA, TOPO and MPA), the synthesis and characterization of ruthenium- nitrosyl complex cis-[ Ru(NO)(4- amp)( bpy )2]3+ (4 -amp = 4 - aminopyridine; bpy = 2,2 \'bipyridine ). The photophysical properties and photochemical evaluation from the interaction between QD and RuNO were done as well the citotoxicity activity from thi association on murine melanoma cell line B16-F10 . Measurements of photophysical xii properties show interactions by the quenching of fluorescence plotted with the Stern-Volmer equation. By determining the number of binding sites (≈ 2) and the binding constants ( kb ) it was found that the interaction between the species presented an emission suppression in a nonlinear curve Stern- Volmer plot resulted by the aggregation process between both compounds. The data corroborates the proposed mechanism that QD540 interacts with two molecules of RuNO. It was also observed that under irradiation in the visible region, 532 nm, that moles of NO released increases at least 6 times when irradiated in the presence of QDs compared to the irradiation of the RuNO complex alone in solution. The process of photo induced electron transfer was proposed as the mechanism for photochemical release of NO while the process of energy transfer was deemed unfavorable due to no overlap between nitrosyl complex absorption and the QD emission spectrum. The fluorescence image analysis demonstrated the potential of QDs as cell markers. The concentrations used in the experiments have not shown toxicity on murine melanoma cells in the absence of light. However when irradiated, QDs exhibited partial cytotoxicity. Therefore, this transfer may occur by the reduction of NO+ to NO0, followed by the release of NO or photoaquation and subsequent photoreduction of nitrite in solution.

Oxido nítrico (NO) é uma molécula que participa de várias atividades fisiológicas no organismo, entre as quais incluem-se ação vasodilatadora e antitumoral. Entretanto sua resposta biológica é dependente da concentração, que quando alta apresenta citotoxicidade. Um fator limitante para sua aplicação em sistemas biológicos é seu curto tempo de meia vida no organismo, o que direcionou os estudos de complexos de rutênio-nitrosilo (RuNO) como doadores de NO. Complexos RuNO apresentam interesse especial devido suas propriedades termoestáveis e fotoquímicas. O uso da luz como um estímulo externo torna-se vantajoso pela capacidade de controlar-se a localização, o tempo de liberação da droga e a dosagem. A terapia fotodinâmica (TFD) tem sido aplicada na terapia clínica contra o câncer. TFD depende da concentração de oxigênio para a produção de espécies reativas, o que é limitado em alguns tipos de tumores devido a hipóxia. Os Pontos quânticos (PQs), semicondutor nanocristalino, destacam-se como materais funcionais com propriedade ópticas únicas dependentes do tamanho. Podem atuar como antenas na captação de luz e fotossensibilização de complexos rutênio-nitrosilo para a liberação de moléculas bioativas. Neste trabalho descrevemos a síntese e caracterização de diferentes PQs (CdS, CdSe e CdTe) utilizando diferentes agentes passivantes (ATG, TOPO e AMP)e a síntese e caracterização do complexo rutênio-nitrosilo cis-[Ru(NO)(4-amp)(bpy)2]3+ (4-amp= 4-aminopiridina; bpy = 2,2 \'bipiridina. Estudos das propriedades fotofísicas e avaliação fotoquímica da interação entre PQ e RuNO foram realizados como também a avaliação da atividade citotóxica x desta associação sobre cultura de células de melanoma murino B16-F10. As medidas das propriedades fotofísicas demonstraram interação pela supressão da fluorescência analisada pela equação de Stern-Volmer. Pela determinação do número de sítios de ligação (≈ 2) e a constante de ligação (kb) verificou-se que a interação entre as espécies apresentaram supressão da emissão em um gráfico não linear de Stern-Volmer resultante do processo de agregação entre os compostos. Os dados obtidos corroboram para o mecanismo proposto, demonstrando que cada PQ540 interage com duas moléculas de RuNO. Ainda observou-se que, sob irradiação na região do visível, em 532 nm, aumenta-se o número de mols de NO liberado de no mínimo 6 vezes quando irradiado na presença de PQs comparado à irradiação do complexo sozinho em solução. O processo de transferência eletrônica fotoinduzida foi proposto como o mecanismo fotoquímico para a liberação de NO, enquanto que o processo de transferência de energia mostrou-se desfavorável devido a não sobreposição entre os espectros de absorção do complexo nitrosilo e o espectro de emissão do PQ. As análises de imagem fluorescentes demonstraram o potencial dos PQs como marcadores celulares. As concentrações utilizadas nos experimentos não demonstraram toxicidade sobre as células de melanoma murino na ausência de luz. Porém quando irradiadas, apresentaram citotoxicidade parcial. Portanto, essa transferência pode ocorrer pela redução do NO+ para NO0, seguida pela liberação de NO ou por fotoaquação e consequente fotoredução do nitrito em solução. / Nitric oxide (NO) is a molecule involved in many physiological activities in human body among them include vasodilator and antitumoral. However, the biological response is concentration dependent and in high concentrations it causes cytotoxicity. A limiting factor for biological applications is the short half-life of NO in the body which has led to the research of nitrosyl ruthenium complexes (RuNO) as NO donors. RuNO complexes are of special interest because of their thermal stability and photochemical properties. The use of light as an external stimulus is advantageous as we can track the location, timing of drug release and dosage. Photodynamic therapy (PDT) has been used in clinical therapy for cancer treatment. PDT depends on oxygen concentrations for reactive oxygen species production what is limited in some types of tumors because of hypoxia. The Quantum dots (QDs), semiconductor nanocrystal, as functional materials, possess unique optical size-dependent properties. QDs can act as antennas in capturing light and photosensitizing ruthenium- nitrosyl complexes for release of bioactive molecules. In this work we describe the synthesis and characterization of different PQs (CdS, CdSe and CdTe) using different passivating agents (TGA, TOPO and MPA), the synthesis and characterization of ruthenium- nitrosyl complex cis-[ Ru(NO)(4- amp)( bpy )2]3+ (4 -amp = 4 - aminopyridine; bpy = 2,2 \'bipyridine ). The photophysical properties and photochemical evaluation from the interaction between QD and RuNO were done as well the citotoxicity activity from thi association on murine melanoma cell line B16-F10 . Measurements of photophysical xii properties show interactions by the quenching of fluorescence plotted with the Stern-Volmer equation. By determining the number of binding sites (≈ 2) and the binding constants ( kb ) it was found that the interaction between the species presented an emission suppression in a nonlinear curve Stern- Volmer plot resulted by the aggregation process between both compounds. The data corroborates the proposed mechanism that QD540 interacts with two molecules of RuNO. It was also observed that under irradiation in the visible region, 532 nm, that moles of NO released increases at least 6 times when irradiated in the presence of QDs compared to the irradiation of the RuNO complex alone in solution. The process of photo induced electron transfer was proposed as the mechanism for photochemical release of NO while the process of energy transfer was deemed unfavorable due to no overlap between nitrosyl complex absorption and the QD emission spectrum. The fluorescence image analysis demonstrated the potential of QDs as cell markers. The concentrations used in the experiments have not shown toxicity on murine melanoma cells in the absence of light. However when irradiated, QDs exhibited partial cytotoxicity. Therefore, this transfer may occur by the reduction of NO+ to NO0, followed by the release of NO or photoaquation and subsequent photoreduction of nitrite in solution.

This dissertation investigates the chemical ingenuity into the development of various photoactive supramolecular donor – acceptor systems to produce clean and carbon free energy for the next generation. The process is inspired by the principles learned from nature’s approach where the solar energy is converted into the chemical energy through the natural photosynthesis process. Owing to the importance and complexity of natural photosynthesis process, we have designed ideal donor-acceptor systems to investigate their light energy harvesting properties. This process involves two major steps: the first step is the absorption of light energy by antenna or donor systems to promote them to an excited electronic state. The second step involves, the transfer of excitation energy to the reaction center, which triggers an electron transfer process within the system. Based on this principle, the research is focused into the development of artificial photosynthesis systems to investigate dynamics of photo induced energy and electron transfer events. The derivatives of Porphyrins, Phthalocyanines, BODIPY, and SubPhthalocyanines etc have been widely used as the primary building blocks for designing photoactive and electroactive ensembles in this area because of their excellent and unique photophysical and photochemical properties. Meanwhile, the fullerene, mainly its readily available version C60 is typicaly used as an electron acceptor component because of its unique redox potential, symmetrical shape and low reorganization energy appropriate for improved charge separation behavior. The primary research motivation of the study is to achieve fast charge separation and slow charge recombination of the system by stabilizing the radical ion pairs which are formed from photo excitation, for maximum utility of solar energy. Besides Fullerene C60, this dissertation has also investigated the potential application of carbon nanomaterials (Carbon nanotubes and graphene) as primary building blocks for the study of the artificial photosynthesis process.

Les hydrogénases ont été identifiées comme des protéines clé de la corrosion induite par les microorganismes (CIM) mais leur réel impact est encore sujet à controverses. Bien qu’elles soient présentes dans la plupart des microorganismes impliqués dans la biocorrosion anaérobie, leur participation dans un transfert électronique direct a rarement été démontrée. L’objectif de ce travail est d’étudier l’influence de l’hydrogénase sur la corrosion anaérobie de l’acier en approfondissant la compréhension des phénomènes interfaciaux qui régissent son action. Il s’agit en particulier d’étudier l’incidence des centres Fe-S présents dans la protéine et qui s’étaient révélés être des acteurs majeurs lors de précédents travaux au LGC. Pour cela, différents types d’hydrogénases ont été conçus, élaborés en collaboration avec l’équipe EAD3 du LISBP, INSA Toulouse, et étudiés : la native et des mutants possédant un nombre plus ou moins important de centres Fe-S. Dans un premier temps, le choix des matériaux a été réalisé sur la base des résultats de caractérisation et d’étude du comportement électrochimique dans le milieu Tris-HCl. L’acier doux S235JR a été choisi car c’est le matériau le plus réactif pour mettre en évidence l’influence de l’hydrogénase. Par la suite, les premières études en présence de divers types d’hydrogénases (native et mutants) ont révélé que la présence de certaines molécules additionnelles dans le milieu de purification ne permet pas d’obtenir un saut du potentiel d’abandon et une vitesse de corrosion exclusivement liés aux enzymes. Le protocole de purification des enzymes a donc été optimisé pour permettre un meilleur rendement de purification avec une activité enzymatique haute, tout en ayant le moins possible d’impact sur les signaux électrochimiques. Enfin, l’utilisation d’un sac de dialyse pour concentrer l’hydrogénase au voisinage de l’électrode de travail a permis d’exacerber l’effet de l’enzyme : une augmentation du potentiel d’abandon ainsi que de la vitesse de corrosion a été observée. La spectroscopie d’impédance couplée à des analyses de surface a également confirmé le fort pouvoir corrosif de l’hydrogénase. En outre, les électrolyses réalisées à potentiel cathodique ont mis en évidence la catalyse de la réaction de réduction par transfert électronique direct entre l’hydrogénase et la surface de l’acier. Le moteur responsable de la prise d’électrons est le centre catalytique de l’enzyme, les centres Fe-S jouant seulement un rôle de transfert des électrons au sein de la protéine. / Hydrogenases have been identified as key proteins in microbially induced corrosion (MIC) phenomena but their real impact is still a controversial issue. Even though they are present in most of the microorganisms involved in anaerobic biocorrosion, their participation in a direct electron transfer mechanism has rarely been demonstrated. The purpose of the present work is to study the influence of hydrogenase on the anaerobic corrosion of steel by deepening the understanding of interfacial phenomena governing its action. The study is particularly focusing on the effect of Fe-S clusters, which had proved to be major players in earlier work at LGC. To achieve this, different types of hydrogenases were designed, developed in collaboration with the EAD3 team of LIBP, INSA Toulouse, and studied: the native and mutants, containing a higher or lower number of Fe-S. First, the material choice was carried out on the base of the characterization results and electrochemical behavior study in TrisHCl medium. The S235JR mild steel was chosen since it is the more reactive material to highlight the influence of hydrogenase. Thereafter, the first studies in presence of various types of hydrogenases (native and mutants) have revealed that the presence of additional molecules in the purification medium does not permit to get an open-circuit potential jump and a corrosion rate that could be attributed solely to enzymes. The enzyme purification protocol has been then optimized to simultaneously allow a better purification performance with a high enzymatic activity and a lower impact on electrochemical signals. Finally, the use of a dialysis bag to concentrate hydrogenase in the close vicinity of the working electrode led to the exacerbation of the enzyme effect: an open-circuit potential ennoblement as well as a corrosion rate increase were observed. Impedance spectroscopy coupled with surface analysis also confirmed the strong corrosiveness of hydrogenase. Electrolysis performed at a cathodic potential brought to light the catalysis of the reduction reaction that occurred by direct electronic transfer between the hydrogenase and the steel surface. The driving force of the electron uptake is the catalytic center of the enzyme, the Fe-S clusters only acting in the electron transfer within the protein.