Nanotubes de carbone biparois : fonctionnalisation et détection in vitro

Depuis plusieurs années, les nanotubes de carbones (NTCs) présentent un important potentiel dans le secteur des applications biomédicales (imagerie médicale, vectorisation de médicaments, etc.). Toutes ces applications impliquent des modifications au niveau de la paroi des NTCs par le biais de fonctionnalisations chimiques afin de pouvoir y greffer des molécules d’intérêt. Il existe deux principales voies de fonctionnalisation impliquant différents types d’interactions et des changements plus ou moins conséquents au niveau des NTCs. D’une part, la fonctionnalisation covalente, la plus largement utilisée, conduit à la formation de liaisons covalentes stables mais modifie en même temps la structure et donc les propriétés intrinsèques des NTCs. D’autre part, les NTCs peuvent être fonctionnalisés de manière non-covalente, c’est-à-dire par le biais d’interactions faibles (interactions hydrophobes, π- π stacking, interactions ioniques, etc.), ce qui n’affecte pas la structure des NTCs. Les objectifs de cette thèse ont été, dans un premier temps, de déterminer le meilleur processus de purification des nanotubes de carbone biparois (DWNTs) synthétisés par CCVD au CIRIMAT afin d’en éliminer toutes traces de nanoparticules métalliques mais surtout d'espèces carbonées indésirables (carbone désorganisé), le but étant de partir d’un échantillon oxydé le plus pur possible et dans lequel le carbone n'est présent que sous forme de NTCs. Ainsi, toute éventuelle compétition entre les différentes espèces carbonées, pouvant rendre impossible toute conclusion claire, est évitée. Les DWNTs ont été choisis comme structure idéale pour représenter à la fois les NTCs mono-paroi (morphologie similaire) et les NTCs multi-parois de manière générale. Les protocoles de fonctionnalisations covalente et non-covalente des DWNTs purifiés ont été mis au point dans un deuxième temps. Le choix des molécules d’intérêt à greffer s’est porté principalement sur des fluorophores (isothiocyanate de fluorescéine FITC ; Cy5 ; une streptocyanine uniquement fluorescente par liaison covalente), permettant ainsi une visualisation directe de la fonctionnalisation. La détermination des taux de greffage, réalisée grâce à différentes techniques de caractérisation, a soulevé les questions de la stabilité dans le temps de la fonctionnalisation non-covalente et de la quantité réellement greffée de façon covalente sur les NTCs lorsque cette voie est choisie. Enfin, les DWNTs ainsi fonctionnalisés ont été par la suite incubés en présence de plusieurs types de cellules afin de tester leur détection in vitro et la stabilité de la fonctionnalisation dans ce type d'environnement. La co-localisation des DWNTs fluorescents au niveau des cellules a été rendue possible par le croisement des résultats obtenus par les microscopies confocales de fluorescence et Raman. ABSTRACT : For many years now, carbon nanotubes (CNTs) show an important potential for biomedical applications (medical imaging, targeted drug delivery, tissue engineering, cancer treatment). All these applications involve modifications of the CNTs walls, through chemical functionalisation, in order to make possible the attachment of molecules of interest. There are two main approaches for functionalisation, involving different interactions and more or less substantial changes in CNTs. On the one hand, the most widely used is the covalent functionalisation that leads to stable covalent bonds but also modifies the structure and thus the inherent properties of CNTs. On the other hand, CNTs can be functionalised by a non-covalent way, that is, through weak interactions (hydrophobic interactions, π- π stacking, ionic interactions, etc.), which do not affect the structure of CNTs. The goals of this thesis were, in a first phase, to determine the best purification strategy for double-walled carbon nanotubes (DWNTs), synthesized by a Catalytic Chemical Vapour Deposition process developed at the CIRIMAT, in order to remove all traces of metal nanoparticles but especially of unwanted carbonaceous species (disorganised carbon); the aim was to start from the cleanest oxidised sample in which CNTs are the only form of carbon, in order to avoid any competition between different carbon species, making then impossible to get a clear conclusion. DWNTs were selected as an ideal structure which would represent both single-walled CNTs (similar morphology) and multi-walled CNTs in general. The protocols of covalent and non-covalent functionalisations of purified DWNTs were developed in a second stage. The choice of the molecules of interest to graft mainly fell on fluorophores (fluorescein isothiocyanate FITC; Cy5; a streptocyanine only fluorescent when it is covalently attached), thus allowing a direct observation of the functionalisation. Grafting ratios could be determined thanks to the combination of several characterisation techniques, which raised some questions on the stability with time of the non-covalent functionalisation, and on what is really covalently grafted on the CNTs when this way is chosen. Finally, such functionalised DWNTs were incubated with several types of cells to test their in vitro detection and the functionalisation stability in this kind of environment. Co-localisation of fluorescent DWNTs in the cells was achieved by comparison of the results obtained from confocal fluorescence and confocal Raman microscopies

Interactions hommes-chimpanzés-forêt. Approche spatiale et territoriale de la répartition des chimpanzés, des perceptions locales et de la gestion de la biodiversité (Sebitoli, parc national de Kibale, Ouganda)

In a context of hyper-proximity between chimpanzees (Pan troglodytes schweinfurthii) and human population, human and non-human territories and their interactions are studied at the extreme north of Kibale National Park (Uganda). Sebitoli area, cul de sac of the protected forest, is crossed by a highly frequented tarmac road and surrounded by densely populated villages and cash crops. Limits of humans, chimpanzees (classified "endangered"; Appendix I, CITES) and protected areas are historically and spatially interlocked, forbidding humans to enter the forest while wild animals go and crop-raid peoples' gardens at its edges. Compared to two chimpanzee communities within Kibale National Park, located less than 17 kilometers away, Sebitoli - former logged area - hosts an important density of this species that is explained by spatial and temporal variation of chimpanzee feeding resources within the forest. At Sebitoli site’s scale (25 km2), Maxent species distribution model shows that crops located at park's edges and the maintenance work on the road crossing the area can actually favour chimpanzee distribution, adding complementary food resources to wild species of the forest. While territories seem legally disjointed, believes and spirits trespass them and the contact with nature is maintained though imagination, culture and some practices. A mitigated adequation between institutional actions toward crop protection and villagers needs leads to a feeling of detachment toward wild fauna and flora conducting to silent (crop raiding compensations are not continuous) and selective (elephants and baboons concentrate villagers' attention compared to chimpanzees) opposition. Positive (species and spaces conservation) and negative (crop-raiding, poaching) retroactions coexist within local biodiversity management. These results provide useful inputs to adapt political measures of endangered-species conservation within increasing anthropogenic contexts.Les territoires humains et ceux des chimpanzés (Pan troglodytes schweinfurthii), ainsi que leurs interactions, sont étudiés à l'extrémité nord du parc national de Kibale (Ouganda), dans un contexte d'hyper-proximité entre la faune sauvage et les populations humaines. Le site de Sebitoli - cul de sac de forêt protégée - est traversé par une route goudronnée très fréquentée et entouré de villages densément peuplés et de cultures de rente. Les limites du territoire des hommes, des chimpanzés (espèce classée « en danger »; annexe I, CITES) et de la forêt protégée s'y superposent historiquement et spatialement, interdisant aux hommes de fréquenter la forêt alors que les animaux sauvages en sortent pour piller les cultures vivrières en lisière. Comparée à deux autres communautés de chimpanzés du parc national de Kibale situées à moins de 17 kilomètres, la densité importante de chimpanzés à Sebitoli - poche de forêt anciennement exploitée - s'explique par la variation spatiale et temporelle de leurs ressources alimentaires en forêt. A l’échelle du site de Sebitoli (25 km2), le modèle Maxent de distribution des espèces montre que la présence de cultures en lisière du parc et l’entretien de la route qui le traverse peuvent favoriser la présence des chimpanzés, en prodiguant des ressources alimentaires complémentaires de celles de la forêt. Alors que les territoires se veulent disjoints légalement, les croyances et les esprits les transcendent et le contact avec la nature est entretenu dans l'imaginaire, dans la culture et dans certaines pratiques. Une adéquation mitigée entre les actions institutionnelles de protection des cultures et les besoins des villageois produit parmi eux un sentiment de désappropriation vis- à-vis de la faune et de la flore sauvage voire d’opposition feutrée (les actions de compensation des incursions de la faune sauvage dans les jardins vivriers sont discontinues) et sélective (les éléphants et les babouins concentrent le mécontentement des villageois par rapport aux chimpanzés). Coexistent ainsi des rétroactions positives (conservation des espèces et des espaces) et négatives (pillage des cultures, braconnage) dans la gestion locale de la biodiversité. Ces résultats apportent des enseignements pour adapter les politiques de conservation des espèces menacées à des espaces de plus en plus anthropisés

Functional bisphosphonate synthesis for the development of new anti-resorption bone drug candidates

Herein we present the synthesis of b-mono and b-bis-substituted vinylidenebisphosphonate esters bearing a carboxylic ester moiety to be used as building blocks for further functionalizations. Reactions of these new bisphosphonate scaffolds through hydrogenation of the unsaturated CQC bond and through metal mediated addition of aryl boronic acids and indoles provide a wide range of new bisphosphonate products as potential leads to contrast osteoporosis

Adaptive evolution of testis-specific, recently evolved, clustered miRNAs in Drosophila

The propensity of animal miRNAs to regulate targets bearing modest complementarity, most notably via pairing with miRNA positions approximately 2-8 (the "seed"), is believed to drive major aspects of miRNA evolution. First, minimal targeting requirements have allowed most conserved miRNAs to acquire large target cohorts, thus imposing strong selection on miRNAs to maintain their seed sequences. Second, the modest pairing needed for repression suggests that evolutionarily nascent miRNAs may generally induce net detrimental, rather than beneficial, regulatory effects. Hence, levels and activities of newly emerged miRNAs are expected to be limited to preserve the status quo of gene expression. In this study, we unexpectedly show that Drosophila testes specifically express a substantial miRNA population that contravenes these tenets. We find that multiple genomic clusters of testis-restricted miRNAs harbor recently evolved miRNAs, whose experimentally verified orthologs exhibit divergent sequences, even within seed regions. Moreover, this class of miRNAs exhibits higher expression and greater phenotypic capacities in transgenic misexpression assays than do non-testis-restricted miRNAs of similar evolutionary age. These observations suggest that these testis-restricted miRNAs may be evolving adaptively, and several methods of evolutionary analysis provide strong support for this notion. Consistent with this, proof-of-principle tests show that orthologous miRNAs with divergent seeds can distinguish target sensors in a species-cognate manner. Finally, we observe that testis-restricted miRNA clusters exhibit extraordinary dynamics of miRNA gene flux in other Drosophila species. Altogether, our findings reveal a surprising tissue-directed influence of miRNA evolution, involving a distinct mode of miRNA function connected to adaptive gene regulation in the testis

How variable is a primate`s world : spatial and temporal variation in potential ecological drivers of behaviour?

Long-term phenological data from the same area over two decades shows that fruit availability can vary as much as eight-fold. Environments have often been characterized by single studies of two years or less, which does not sufficiently account for environmental variation. This book chapter presents examples of behavioural and ecological variation, and considers ways to advance behavioural studies of primates by considering these variations. Perhaps one area of such research is the development of the "Primate Socioecological Model." For instance, in Madagascar where female dominance is common, climate and fruiting patterns are more unpredictable than in other tropical regions where male dominance is the norm.Canada Research Chairs ProgramNatural Science and Engineering Research Council of CanadaFonds Québécois de la Recherché sur la Nature et les TechnologiesNational Geographic Societ

Exploring multiple dimensions of conservation success : long-term wildlife trends, anti-poaching efforts and revenue sharing in Kibale National Park, Uganda

Parks are essential for protecting biodiversity and finding ways to improve park effectiveness is an important topic. We contributed to this debate by examining spatial and temporal changes in illegal activities in Kibale National Park, Uganda between 2006 and 2016 and used existing data to evaluate how the changes were correlated with the living conditions of people in neighboring communities, as well as patrolling effort. We explore the effectiveness of conservation strategies implemented in Kibale, by quantifying changes in the abundance of nine animal species over two to five decades. While uncertainty in such animal survey data are inherently large and it is hard to generalize across a 795-km2 area that encompasses diverse habitat types, data suggest an increase in animal abundance in the National Park. An increase in patrolling effort by park guards over the decade was correlated with a decline in the number of traps and snares found, which suggests patrolling helped limit resource extraction from the park. The park’s edge was extensively used for illegal forest product extraction, while the setting of snares occurred more often deeper in the forest. Perhaps counter-intuitively, increased community wealth or park-related employment in a village next to the park were positively correlated with increased illegal forest product extraction. Overall, our results suggest that the portfolio of conservation strategies used over the last two to five decades were effective for protecting the park and its animals, although understanding the impact of these efforts on local human populations and how to mitigate any losses and suffering they sustain remains an important area of research and action. It is evident that complex social, political and economic drivers impact conservation success and more interdisciplinary studies are required to quantify and qualify these dimensions

Palladium(II)-η3-Allyl Complexes Bearing N-Trifluoromethyl N-Heterocyclic Carbenes: A New Generation of Anticancer Agents that Restrain the Growth of High-Grade Serous Ovarian Cancer Tumoroids

The first palladium organometallic compounds bearing N-trifluoromethyl N-heterocyclic carbenes have been synthesized. These η3-allyl complexes are potent antiproliferative agents against different cancer lines (for the most part, IC50 values fall in the range 0.02–0.5 μm). By choosing 1,3,5-triaza-7-phosphaadamantane (PTA) as co-ligand, we can improve the selectivity toward tumor cells, whereas the introduction of 2-methyl substituents generally reduces the antitumor activity slightly. A series of biochemical assays, aimed at defining the cellular targets of these palladium complexes, has shown that mitochondria are damaged before DNA, thus revealing a behavior substantially different from that of cisplatin and its derivatives. We assume that the specific mechanism of action of these organometallic compounds involves nucleophilic attack on the η3-allyl fragment. The effectiveness of a representative complex, 4 c, was verified on ovarian cancer tumoroids derived from patients. The results are promising: unlike carboplatin, our compound turned out to be very active and showed a low toxicity toward normal liver organoids

Does the presence of elephant dung create hotspots of growth for existing seedlings?

In general, the addition of elephant dung did not increase seedling growth, and only increased the number of leaves in shade-tolerant plants with a large initial number of leaves. Researchers have speculated that the loss of elephants would shift the composition of African forests to slow-growing tree species. However, findings in this study show some slow-growing shade-tolerant plants grew more new leaves with additional nutrient input from elephant dung, a condition that would occur if elephant numbers increase. Forest elephant (Loxodonta cyclotis) populations declined by 62% between 2002 and 2011. The population is now only 10% of what it was historically, and occupies less than 25% of its original range

The anticancer activity of an air-stable Pd(i)-NHC (NHC = N-heterocyclic carbene) dimer

A new dinuclear Pd(i) complex coordinating two bis(NHC) ligands revealed an unsuspected stability despite the unsaturation of the two metal centres. Even more surprisingly, the compound showed high and selective antiproliferative activity against different cancer cell lines and ovarian cancer tumoroids, and the mechanism of action was different from that of cisplatin

Spatial and phylogenetical closeness between chimpanzees and humans and health consequences. Study case of Kibale national park, Uganda

Chimpanzee, our closest relative, is today severely threatened by habitat fragmentation. As a consequence, people and chimpanzees live in increasing proximity. In order to estimate the risks for both species due to such changes, we aim at understanding if chimpanzees avoid the interface and limit occasions of contact with human beings. Fifteen years of research on two chimpanzee communities at Kibale National Park (Uganda) demonstrate that chimpanzees do not avoid forest boundaries, cross tarmac road and that human activities are frequent in the protected area. Direct consequences on chimpanzee health include severe mutilations due to poaching. The diagnosis of similar parasites in both species underlines the potential risk of interspecific transmission and the necessity to expand such study for public health and conservation issuesLe Chimpanzé, espèce vivante la plus proche phylogénétiquement de l’homme, est aujourd’hui menacée de disparition en particulier par la fragmentation des forêts tropicales. Afin d’évaluer les risques pour les deux espèces de cette proximité spatiale en potentielle augmentation, notre objectif est d’étudier si les chimpanzés évitent les interfaces et si leur santé témoignent de ces éventuels contacts. Quinze années de recherche sur deux communautés de chimpanzés sauvages du parc national de Kibale (Ouganda) montrent que les chimpanzés n’évitent pas les lisières, traversent une route à fort trafic et que les activités humaines en forêt sont fréquentes. Nos observations révèlent des conséquences sévères sur leur santé: mutilations dues au braconnage et détection d’agents pathogènes similaires, impliquant probablement des transmissions interspécifiques. Dans un contexte où les maladies émergentes peuvent entraîner des conséquences fatales sur la santé des hommes et des chimpanzés, il est primordial d’approfondir ces travaux pour la santé publique et la conservatio