Une pléthore de processus biologiquement pertinents dépend directement de la sécrétion de biomolécules dans le milieu extracellulaire, aux fonctions régulatrices ou composants structurels. L’analyse de processus biologiques complexes nécessite ainsi la mise au point de nouveaux outils de biodétection. Par conséquent, le but de cette thèse est de fournir des stratégies polyvalentes pour la génération de biocapteurs et de biopuces innovants basés sur la Résonance des Plasmons de Surface (SPR). À l’issue de ces travaux, une méthode de photofonctionnalisation indirecte a été mise au point. Ce procédé a permis de générer des micro-réseaux de protéines dans des conditions entièrement aqueuses, et ainsi de préserver la fonctionnalité des protéines greffées. De plus, nous avons créé et évalué une nouvelle biopuce SPR microstructurée pour le suivi en temps réel des sécrétions cellulaires. Cette biopuce microstructurée présente deux phénomènes optiques différents qui peuvent être utilisés pour la détection cellulaire et le suivi de leurs sécrétions. Enfin, de multiples stratégies de fonctionnalisation ont été évaluées pour la conception d’une biopuce SPR nanostructurée à faisceau de fibres optiques. Parmi ces approches, la génération de monocouches photoréactives auto-assemblées a été la plus adaptée à ce système et est en cours d’optimisation. Une fois réalisée, cette biopuce nanostructurée pourrait ouvrir la voie à la poursuite du développement de systèmes prometteurs de biodétection in vivo. / A plethora of biologically relevant processes depends directly on the effective secretion of biomolecules, from regulatory molecules to structural components. Thus, the analysis of complex biological processes requires the development of novel biosensing tools. Therefore, the aim of this thesis is to provide versatile strategies for the generation of innovative biosensors and biochips based on Surface Plasmon Resonance (SPR). As a result from this research, an indirect photofunctionalization method was developed. This procedure allowed the generation of protein microarrays in fully aqueous conditions while preserving the functionality of the grafted proteins. Furthermore, we created and evaluated a novel microstructured SPR biochip for real-time monitoring of cellular secretions. This microstructured biochip presents two different optical phenomena which could be used for cell detection and the monitoring of their secretions. Finally, multiple functionalization strategies were evaluated for the conception of a nanostructured fiber-bundle SPR biochip. Among the approaches, the generation of photoreactive self-assembled monolayers was the most adapted to this system and currently is being optimized. Once achieved, this nanostructured biochip could pave the way for further development of promising in vivo biosensing systems.

The air-water interface is an important natural boundary layer that has been neglected as an area of environmental field research. This study establishes that comparative microscopy can be an effective environmental method, and establishes that the term metallic surface films, is a more accurate descriptor than iron oxide surface films. This research shows that surface films are complex, often with layered structure, serve as habitat for significant biota, and act as a point of mineralization to several transition metal elements including manganese, iron, copper, nickel and zinc. This study demonstrates that surface films form under several conditions and can have diverse morphology. Activity of biota, microbes, particularly diatoms, suggests that bacteria and cyanobacteria integrate into the film often in patches, represented by forms and casts. Analytical imaging is used to document and compare film morphology and structures, using scanning electron microscopy, photoemission electron microscopy and transmission electron microscopy with elemental analysis by energy dispersive spectroscopy to confirm the hypothesis. Instrument parameters and strengths are reviewed. Component layers of a copper/zinc film were used to confirm metallic layers and elemental distribution. Bacterial casts were used to confirm film interaction, and to show entrainment and enrichment of the film to incorporate autochthonous and allochthonous materials into the films themselves. Most samples were from Oregon selected sites, with some samples from Maryland and Barbados.

Le domaine du diagnostic moléculaire connait un essor impressionnant depuis plusieurs dizaines d’années. Différents outils d’analyse d’interactions moléculaires sont présents sur le marché. La plupart d’entre eux sont basés sur des tests immunologiques utilisant la fluorescence comme technique de lecture. Or, l’utilisation de techniques de détection avec marquage comme la fluorescence augmente le coût d’une analyse et peut dénaturer un échantillon. Dans cette perspective, une technique de lecture optique sans marquage, qui est une alternative à la fluorescence, a été développée. Le principe de lecture est basé sur le suivi des modifications du spectre de diffraction de réseaux périodiques, composés de molécules sondes, lors d’interactions avec différentes solutions à analyser. Cette thèse CIFRE est le fruit d'une collaboration entre le LAAS CNRS et la société Innopsys, spécialisée dans la commercialisation d'outils de lecture optique. Elle porte sur le développement d’une plateforme dédiée à l’analyse biomoléculaire (ADN, protéines) au travers de l’utilisation de biopuces multiplexées et d’un instrument de lecture optique sans marquage automatisée. Nous montrons que cette technologie de biodétection sans marquage nécessite le développement d’une chimie de surface permettant l’organisation de molécules sondes en réseaux de lignes périodiques, tout en minimisant l’adsorption non-spécifique entre les lignes. Nous présentons l’optimisation d’un procédé de bi-fonctionnalisation de surface, qui met en jeu un dépôt multiplexé par microcontact printing sur des couches de polymères passivantes. Ces surfaces structurées à l’échelle moléculaire ont permis la détection d’interactions protéines/protéines sans marquage et le concept semble également transférable pour la détection d’hybridation de courtes séquences d’ADN / Development of bioassays has become the matter of intense research in the field of molecular diagnostic. Biodetection techniques have been drastically used in laboratory since the past 20 years and tend now to reach the in-vitro diagnostic industry. Most commercially available biosensing methods rely on immunoassays and use fluorescence as reading technique. However, the use of labeling methods such as fluorescence increases the cost of a single bioassay and may interfere with the biological functions of molecules. In this perspective, we have developed an optical label-free technique of microarray reading, which is an alternative to fluorescence. In this work, we use a label free biosensing method based on the diffraction of light by molecular gratings. Molecular gratings are employed as diffractive probe arrays for protein interaction analysis, as the diffraction efficiency changes in response to analyte binding. This Ph.D is supported by the French company Innopsys, which provides optical solutions for microarray reading and the Nanobiosystems group at the LAAS-CNRS. This work deals with the development of a detection platform for biomolecular interactions analysis, through the use of multiplexed biochips and the validation of an optical scanner. We present a special surface chemistry, based on blocking layers to reduce the non-specific protein adsorption and consequently decrease the limit of detection. Thanks to bi-functionalized biochips and this label free instrument, we have detected proteins interactions involving low molecular weight molecules

Developing a fundamental understanding of the interactions of chemical warfare agents (CWAs) with surfaces is essential for the rational design of new sorbents, sensors, and decontamination strategies. The interactions of chemical warfare agent simulants, molecules which retain many of the same chemical or physical properties of the agent without the toxic effects, with amorphous silica were conducted to investigate how small changes in chemical structure affect the overall chemistry. Experiments investigating the surface chemistry of two classes of CWAs, nerve and blister agents, were performed in ultrahigh vacuum to provide a well-characterized system in the absence of background gases. Transmission infrared spectroscopy and temperature-programmed desorption techniques were used to learn about the adsorption mechanism and to measure the activation energy for desorption for each of the simulant studied. In the organophosphate series, the simulants diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), dimethyl chlorophosphate (DMCP), and methyl dichlorophosphate (MDCP) were all observed to interact with the silica surface through the formation of a hydrogen bond between the phosphoryl oxygen of the simulant and an isolated hydroxyl group on the surface. In the limit of zero coverage, and after defect effects were excluded, the activation energies for desorption were measured to be 57.9 ± 1, 54.5 ± 0.3, 52.4 ± 0.6, 48.4 ± 1, and 43.0 ± 0.8 kJ/mol for DIMP. DMMP, TMP, DMCP, and MDCP respectively. The adsorption strength was linearly correlated to the magnitude of the frequency shift of the ν(SiO-H) mode upon simulant adsorption. The interaction strength was also linearly correlated to the calculated negative charge on the phosphoryl oxygen, which is affected by the combined inductive effects of the simulants' different substituents. From the structure-function relationship provided by the simulant studies, the CWA, Sarin is predicted to adsorb to isolated hydroxyl groups of the silica surface via the phosphoryl oxygen with a strength of 53 kJ/mol. The interactions of two common mustard simulants, 2-chloroethyl ethyl sulfide (2-CEES) and methyl salicylate (MeS), with amorphous silica were also studied. 2-CEES was observed to adsorb to form two different types of hydrogen bonds with isolated hydroxyl groups, one via the S moiety and another via the Cl moiety. The desorption energy depends strongly on the simulant coverage, suggesting that each 2-CEES adsorbate forms two hydrogen bonds. MeS interacts with the surface via a single hydrogen bond through either its hydroxyl or carbonyl functionality. While the simulant work has allowed us to make predictions agent-surface interactions, actual experiments with the live agents need to be conducted to fully understand this chemistry. To this end, a new surface science instrument specifically designed for agent-surface experiments has been developed, constructed, and tested. The instrument, located at Edgewood Chemical Biological Center, now makes it possible to make direct comparisons between simulants and agents that will aid in choosing which simulants best model live agent chemistry for a given system. These fundamental studies will also contribute to the development of new agent detection and decontamination strategies. / Ph. D.

No description available.

Malignant melanoma cancer is the sixth common cancer diagnosed in the United States. Surgery, chemotherapy and radiation are some of the successful techniques in killing tumor cells. However, in these techniques, it is not easy to distinguish tumor cells from the healthy once which inadvertently get exposed to chemical agent/radiation. Therefore it is required to develop an anticancer agent which selectively kills the cancer cells, while still protecting the normal tissues. In our preliminary work, we have shown that Dextran (1000Da) coated Cerium oxide nanoparticles (Dex-CNPs) selectively kills the cancer cells (50% killing at a concentration of 150μM) without inducing toxicity to the normal cells. However, the mechanism involved on how CNPs/Dex-CNPs attain the selectivity and efficiently kill the tumor cells is still unknown. In this study we have synthesized Dextran coated ceria nano particles (Dex- CNPs) with different surface oxidation state ratio (Ce4+/Ce3+). This will provide an in depth understanding of the key chemical and physical properties of the system that can improve its efficacy. The varied surface oxidation of the particles is achieved by exposing Dex-CNPs to light which initiates a color change from dark to pale yellow indicating the reduction of Ce4+ to Ce3+. Interestingly we have found that the DexCNPs exposed to light have reduced cytotoxicity towards squamous cell carcinoma cell line (CCL30) compared to the protected once. Characterization of the same revealed that Dex- CNPs exposed to light have decreased Ce4+ /Ce3+ surface oxidation ratio compared to the other. This provides more insight in useful synthesis of Dex-CNPs in terms of storage and handling. In summary, higher Ce4+ /Ce3+ surface oxidation ratio is more efficient in hindering tumor growth by effectively hindering the tumor-stoma interaction.

Recent advances in surface science technology have opened new opportunities for atomic scale studies in the field of nanoparticle (NP) catalysis. The 2007 Nobel Prize of Chemistry awarded to Prof. G. Ertl, a pioneer in introducing surface science techniques to the field of heterogeneous catalysis, shows the importance of the field and revealed some of the fundamental processes of how chemical reactions take place at extended surfaces. However, after several decades of intense research, fundamental understanding on the factors that dominate the activity, selectivity, and stability (life-time) of nanoscale catalysts are still not well understood. This dissertation aims to explore the basic processes taking place in NP catalyzed chemical reactions by systematically changing their size, shape, oxide support, and composition, one factor at a time. Low temperature oxidation of CO over gold NPs supported on different metal oxides and carbides (SiO2, TiO2, TiC, etc.) has been used as a model reaction. The fabrication of nanocatalysts with a narrow size and shape distribution is essential for the microscopic understanding of reaction kinetics on complex catalyst systems ("real-world" systems). Our NP synthesis tools are based on self-assembly techniques such as diblock-copolymer encapsulation and nanosphere lithography. The morphological, electronic and chemical properties of these nanocatalysts have been investigated by atomic force microscopy (AFM), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). Chapter 1 describes briefly the basic principles of the instrumentation used within this experimental dissertation. Since most of the state-of-art surface science characterization tools provide ensemble-averaged information, catalyst samples with well defined morphology and structure must be available to be able to extract meaningful information on how size and shape affect the physical and chemical properties of these structures. In chapter 2, the inverse-micelle encapsulation and nanosphere lithography methods used in this dissertation for synthesizing uniformly arranged and narrow size- and shape-selected spherical and triangular NPs are described. Chapter 3 describes morphological changes on individual Au NPs supported on SiO2 as function of the annealing temperature and gaseous environment. In addition, NP mobility is monitored. Chapter 4 explores size-effects on the electronic and catalytic properties of size-selected Au NPs supported on a transition metal carbide, TiC. The effect of interparticle interactions on the reactivity and stability (catalyst lifetime) of Au NPs deposited on TiC is discussed in chapter 5. Size and support effects on the formation and thermal stability of Au2O3, PtO and PtO2 on Au and Pt NPs supported on SiO2, TiO2 and ZrO2 is investigated in chapter 6. Emphasis is given to gaining insight into the role of the NP/support interface and that played by oxygen vacancies on the stability of the above metal oxides. Chapter 7 reports on the formation, thermal stability, and vibrational properties of mono- and bimetallic AuxFe1-x (x = 1, 0.8, 0.5, 0.2, 0) NPs supported on TiO2(110). At the end of the thesis, a brief summary describes the main highlights of this 5-year research program.

In the search for the conformation of extant or extinct life in an extraterrestrial setting the detection of organic molecular species which may be considered diagnostic of life is a key objective. These molecular targets comprise a range of distinct chemical species, with recognisable spectroscopic features. This project aims to use these features to develop an in-situ molecular specific Raman spectroscopic methodology which can provide structural information about the organic–inorganic interface. The development of this methodology identified a surface enhanced Raman spectroscopic technique, that required minimal sample preparation, allowed for the detection of selected organic species immobilised on an inorganic matrix and was effective for quantities below those which conventional dispersive Raman spectroscopy would detect. For the first time spectral information was gained which allowed analysis of the organic–inorganic interface to be carried out, this gave an insight into the orientation with which molecules arrange on the surfaces of the matrices. Additionally a method for the detection of organic residues intercalated into the interlamellar space of smectite type clays was developed. An evaluation of the effectiveness of uni and multivariate methods for the analysis of large datasets containing a small number of organic features was also carried out, with a view to develop an unsupervised methodology capable of performing with minimal user interaction. It has been shown that a novel use of the Hotellings T2 test when applied to the principal component analysis of the datasets combined with SERS allows identification of a small number of organic features in an otherwise inorganic dominated dataset. Both the SERS and PCA methods hold relevance for the detection of organic residues within interplanetary exploration but may also be applied to terrestrial environmental chemistry.

Thesis advisor: Jeffery A. Byers / Thesis advisor: Petter Zhang / This thesis discusses the development of a surface-initiated N-carboxyanhydride (NCA) polymerization system from a redox-switchable catalyst for polyamide synthesis and further efforts towards the synthesis of polypeptide-based materials through the integration of NCA synthesis and its polymerization. In Chapter one, the most used methods to obtain polypeptide-based materials as well as their significant limitations are introduced. A new strategy is presented to access the polypeptide-based materials based on the integrated catalysis under spatial and temporal control. In Chapter two, a strategy to allow the attachment of a redox-switchable NCA polymerization catalyst on surface of titania for the synthesis of polyamide brushes will be demonstrated. Investigations about the kinetics of this surface-initiated ring-opening polymerization will be presented by carrying out the reaction in batch and under flow. Chapter three will discuss efforts towards achieving the integration of NCA synthesis and NCA polymerization, which includes an additional anchoring method to support polymerization catalyst and compatibility tests between the two separate reactions. / Thesis (MS) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

No description available.