L'imagerie de fluorescence s'est particulièrement développée au fil de ces dernières décennies notamment pour l'exploration des systèmes biologiques. De nombreux développements portant à la fois sur les instruments d'analyse et les agents de contraste (sondes) ont été entrepris pour améliorer cette technique de bioanalyse. Mes travaux de thèse avaient pour but d'explorer diverses plateformes moléculaires pro-fluorescentes pouvant générer, sous l'effet d'un stimulus biologique / chimique, un fluorophore organique. Cette approche de synthèse chimique in-situ met en jeu des réactions domino caractérisées par la formation et la rupture de liaisons covalentes. Ce processus devrait ouvrir la voie à des sondes fluorogéniques possédant des rapports signal sur bruit élevés. Cette étude avait aussi pour but d'étudier la synthèse in-situ de fluorophores déclenchée par plusieurs stimuli afin de concevoir des portes logiques moléculaires de type "AND", dans un but de détection "multi-analytes". Pour établir la preuve de principe, la formation d'un coeur 7-hydroxy-2-iminocoumarine fluorescent déclenchée par divers couples d'enzymes (hydrolase / nitroréductase) a été étudiée. L'ensemble de ces travaux sont décrits dans le chapitre I de ce manuscrit. Par la suite et comme présenté dans les chapitres II et III, notre intérêt s'est porté sur le développement des plateformes fluorogéniques libérant des fluorophores ayant des maxima d'absorption / émission décalés vers le rouge en comparaison de ceux des coumarines. Une première réalisation a concerné la conception d'un précurseur "cagé" agissant comme sonde à peptidases ou nitroréductase par libération d'un dérivé pyronine. Des travaux portant sur la formation in-situ d'une benzophénoxazine sont également en cours et sont présentés au chapitre III. Un dernier aspect de ce travail a concerné la chimie d'une nouvelle famille de fluorophores proche-IR (les hybrides dihydroxanthène-hémicyanine) dont la formation in-situ pourra être envisagée pour des applications in-vivo. / Fluorescence imaging is a growing field of biology over the past decades. Intensive works mainly focused on instrumental developments and chemistry of contrast agents (probes), were already done to improve such bioanalytical technique. The main goal of this Ph. D. thesis was to explore various fluorogenic molecular platforms responsive to various (bio)chemical stimuli and capable of releasing organic fluorophores in the biological medium to analyze. This approach named "in-situsynthesis" is based on domino reactions belonging to the repertoire of "covalent chemistry", triggered by the target (bio)analyte. This kind of process should provide advanced fluorogenic probes with high signal-to-noise ratio. Another purpose of this work was to investigate some dualtriggering events to access to fluorogenic molecules acting as "AND-type" molecular logic gates for dual-analytes detection applications. To establish this approach, the formation of highly fluorescent7-hydroxy-2-iminocoumarin scaffolds triggered by several enzyme pairs (hydrolase and nitroreductase) was studied and now described in the first chapter of this manuscript. The second part of this work, described in chapters II and III, was devoted to the development of original "caged" precursors able to release fluorophores whose absorption / emission maxima are dramatically redshifted compared to those of coumarin derivatives. The first achievement concerned the detection of protease or nitroreductase activities through in-situ formation of a pyronin scaffold. Further works, currently in progress, are focused on "caged" precursors whose the dual reaction with a model protease should lead to the release of a benzophenoxazine derivative. Finally, some chemistry aspects related to an emerging and promising class of NIR fluorophores (dihydroxanthene-hemicyanine hybrids) are presented and the opportunity to form them in biological media, upon enzymatic triggering is also discussed.

In the last decade, there has been a growing interest in the use of differential sensing for molecular recognition. Inspired by the mammalian olfactory system, differential sensing employs an array of non-selective receptors, which through cross-reactive interactions, create a distinct pattern for each analyte tested. The unique fingerprints obtained for each analyte with differential sensing are studied with statistical analysis techniques, such as principal component analysis and linear discriminant analysis. It was postulated that serum albumin proteins would be applicable to differential sensing schemes due to significant differences in sequence identity between different serum albumin species, and due to the wide range of hydrophobic molecules which are known to bind to these proteins. Consequently, cross-reactive serum albumin arrays were developed, utilizing hydrophobic fluorescent indicators to detect hydrophobic molecules. As such, serum albumin cross-reactive arrays were employed to discriminate subtly different hydrophobic analytes, and mixtures of these analytes, in the form of terpenes and perfumes, plasticizers and plastic explosive mixtures, and glycerides and adipocyte extracts. In this doctoral work, a detailed review of the field of differential sensing, and a thorough study of principal component analysis and linear discriminant analysis in various differential sensing scenarios, are given. These introductory chapters aid in better understanding the methods and techniques applied in later experimental chapters. In chapter 3, serum albumins, a PRODAN indicator, and an additive are shown to discriminate five terpene analytes and terpene doped perfumes. Chapter 4 describes an array with serum albumins, two dansyl fluorophores, and an additive which successfully differentiate the plasticizers found within the plastic explosives C4 and Semtex and simulated C4 and Semtex mixtures. Discrimination of these simulated mixtures was also achieved with this array in the presence of soil contaminants, demonstrating the potential real-world applicability of this sensing ensemble. Finally, chapter 5 details an array consisting of serum albumins, several fluorescent indicators, and a Grubb's olefin metathesis reaction, to differentiate saturated and unsaturated triglycerides, diglycerides, and monoglycerides. Mixtures of glycerides in adipocyte extracts taken from rats with different health states were then successfully discriminated, showing promise for clinical applications in differentiating adipoctyes from pre-diabetic, type 2 diabetic, and non-diabetic individuals. / text

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