Understanding and controlling the nature of interactions at interfaces between various materials and systems has always been of interest, but with the fast development and need of new technologies it has become crucial to employ these interactions for various applications that range from biosensing of analytes in bodily fluids and the environment, to the development of bio-compatibatible and bio-mimicking surfaces that can be used to successfully couple biological systems to artificial materials and also build models for understanding biological systems better. Self-assembled monolayers (SAMs) are organized molecular assemblies that are formed by spontaneous adsorption of a compound in solution to a surface. They can change the surface properties without the need of changing the physical properties of the bulk material. Formation of SAMs on different substrates was investigated and performed in the work described in the thesis to be used in the detection of nucleic acids and enzyme inhibitors, development of surfaces with anti-adhesive and anti-microbial properties, development of surfaces for directed and patterned cell adhesion, and the construction of artificial membranes that can be used for studying the interaction of membrane proteins and the discovery of new pharmaceuticals. The surface of gold substrates was modified with alkanethiol compounds in order to attach biomolecules such as nucleic acids and proteins which allowed the modified surface to be used as a biosensor. Binding interactions were detected by electrochemical impedance spectroscopy and surface plasmon resonance. A surface resonance sensor provided a platform for the detection of DNA and RNA oligonucleotide sequences and also the detection of one-nucleotide mismatches from the hybridization these oligonucleotides. The same sensor platform, but with a different surface modification, was used to covalently attach an enzyme whose inhibitors are used as therapeutic drugs and also as pesticides and nerve agents. The sensor was able to detect two of these inhibitors, which are used in the treatments of Alzheimer's disease, at a range of concentrations. This allowed the determination of binding affinity constants for the two inhibitors. The surface of gold was modified with functional groups in order to obtain inert surfaces with anti-adhesive properties with regard to the attachment of proteins. These surfaces are of interest in generating bio-compatible medical implants that can resist rejection from the host's immune system andor the formation of bacterial biofilms. The inert property was combined with anti bacterial properties by attaching an antibiotic which is known to kill bacteria by binding to the cell membrane. Following characterization of gold surfaces by contact angle measurements, ellipsometry, grazing angle FT-IR, cyclic voltammetry and electrochemical impedance spectroscopy, the surface of glass substrates was modified with similar functional groups, by switching to a different coupling ligand for the substrate. Alkoxysilanes were used to modify the surface of glass, which can also be used to modify other materials, such as polymers and stainless steel. Gold and glass surfaces were also modified with antibodies, other proteins, and other functional groups which favored or prevented cell adhesion. This led to the ability for patterned and directed adhesion, and differentiation of several cell lines. Preparation and chemical modification of magnetic beads and the ability to modify the bead surface created the possibility to grow and trap cells in a flow-through magnetic bioreactor, which will be used for the continuous production of metabolites and growth of tissue in a three-dimensional construct. Modification of gold substrates also led to the construction of artificial phospholipid membranes, whose composition can be controlled and most importantly can be used for the insertion and characterization of membrane proteins on a two-dimensional platform. This will allow for characterization of ligand-protein and protein-protein interactions with surface characterization techniques such as surface plasmon resonance and electrochemical impedance spectroscopy. The various surface modifications and applications described in this work underscore a general theme that the surface of many different materials can be modified by using the correct functional groups for the formation of the self-assembled monolayer on the substrate surface, thus obtaining the same surface properties without the need to change the physical and chemical properties of the bulk material.

No description available.

Les recherches décrites dans ce travail appartiennent à une branche de la science relativement jeune et interdisciplinaire, la nanophotonique. Les projets réalisés avaient pour objectif de décrire les phénomènes qui apparaissent lors de l’irradiation par un faisceau lumineux d’un matériau restreint à la dimension de quelques nanomètres à quelques centaines de nanomètres. Les phénomènes qui ont été examinés sont la génération d’absorption, de dispersion et d’émission fluorescente ainsi que le renforcement d’émission fluorescente et le renforcement du champ électromagnétique à une échelle plus petite que la limite de diffraction restreignant l’optique classique. Dans cette thèse, j’ai profité de nouvelles propriétés de la matière générées quand les dimensions sont réduites à l’échelle nanométrique (10-9 m). Elles se distinguent significativement des propriétés classiques qui caractérisent un matériau de plus grandes dimensions. Le changement de propriétés résulte de la limitation spatiale de la structure du nuage d'électrons et de l’augmentation du rapport entre la surface du matériau et son épaisseur. 23 Les particules plasmoniques, largement décrites dans ce travail, en sont un excellent exemple puisque leurs colloïdes possèdent une section efficace d'absorption très importante dans le domaine visible. Un colloïde peut présenter des couleurs différentes en fonction des formes, des dimensions et de la composition des particules qui le constituent, contrairement à une surface métallique qui ne doit son aspect qu'à la réflexion presque totale de la lumière visible et au lustre métallique. À l’échelle nanométrique, nous avons affaire à la résonance plasmonique de surface, un phénomène qui ouvre la porte à la manipulation, à la modification et au renforcement du champ électromagnétique autour de la nanostructure métallique. La possibilité de concentrer la lumière autour d’une nanoparticule au-dessous de la limite de diffraction a trouvé un bon nombre d’applications, dont la microscopie en champ proche, la spectroscopie Raman exaltée de surface (ang. Surface-enhanced Raman spectroscopy, SERS), la théranostique , la production de lecteurs de carte mémoire ou de cellules photovoltaïques. Les recherches décrites dans ce travail ont un caractère interdisciplinaire, elles améliorent nos connaissances dans le domaine de la synthèse de nanostructures plasmoniques, et des méthodes de séparation permettant d'obtenir des colloïdes qui contiennent des nanoparticules presque monodispersives. La méthode de synthèse d'un nouveau métamatériau, produit lors du transfert des nanobâtonnets d’or de l’eau à l’isopropanol, a aussi été présentée dans cette thèse. Par ailleurs, ces recherches ont montré une forte exaltation du champ électromagnétique parmi les nanoparticules. J’ai aussi dénoté une application potentielle de ce matériau en tant que substrat pour la détection de biomolécules. En outre, j’ai préparé des nanocoques d’or largement stables et dont l’épaisseur de dorure est contrôlée. À l’aide de la technique Z-scan, j’ai fait la mesure des propriétés non-linéaires des nanocoques d’or et je les ai comparées avec celles des nanobâtonnets d’or et de colorants organiques en indiquant une application possible. J’ai discuté aussi d'une nouvelle méthode de biofonctionnalisation des nanobâtonnets d’or qui m’a permis de créer un marqueur afin de visualiser des cellules vivantes. Il est aussi possible de convertir l’énergie lumineuse en énergie thermique par le biais des nanostructures plasmoniques, ce qui pourrait trouver d’autres applications intéressantes dans les recherches en théranostique. / This dissertation shows the experimental results, which I strongly believe prove the possibility of application the proposed bioprobe in theranostics treatment. The advantages and disadvantages of the probe were discussed on the basis of imaging of cancer cells, toxicity and fluorescent efficiency. It is important to mention that the process of synthesis of the biomarker was controlled on each step, starting from the selection of appropriate size and shape of the core, through optical characterization, effective way of biofunctionalization and finally application in cell visualization.At first, I presented an improved method of separation of distinct shapes of gold nanoparticles from a heterogeneous mixture. The method of centrifugation in a glucose density gradient was applied in order to get homogenous fractions. The procedure of sample preparation, centrifugation and collection of the separated nanoparticles is described. Moreover, I discussed the synthesis with and without Ag+ ions added to the growth solution.Then, I had a closer look on transferring procedure of the NRs from water into IPA solvent, which induce self-organization of the nanoparticles. Optical characterization as well as recorded ATR spectra gave the foundations to understanding of the assembly process taking place. Additionally the work is enriched with the theoretical calculations indicating that individual self-assembled nanostructures show strong light polarization dependent properties. The electric field localized in the gap between NRs is estimated to be enhanced over 350 fold.In the next part of my thesis I have performed a systematic and quantitative description of the interactions of NRs with light (femtosecond laser pulses, 130 fs, 800 nm) in order to characterize the optical properties and design NRs with specific functionalities. In this work I focused on the investigation of structural changes of the NRs and the parameters influencing the reshaping, like surface modification using sodium sulfide, laser power and the position of the longitudinal surface plasmon resonance band (l-SPR) with respect to the laser wavelength.In the next part of the thesis I have quantified the probability of simultaneous absorption of two photons by plasmonic nanoparticles: gold nanorods and gold nanoshells, and by several dye molecules, by using the open-aperture Z-scan technique available in the laboratory at WUT in Poland. At first, I started from fabrication of stable and highly monodisperse NSs suspensions in water, with a varying degree of gold coverage. Then, the NLO properties of the nanoshells were quantified in terms of the two-photon absorption coefficient (α2), the nonlinear refractive index (n2), and the saturation intensity for one-photon absorption (Isat), which are extensive quantities. Then I calculated the two-photon absorption cross-section (σ2) taken per nanoparticle, which was also interpreted in terms of the merit factor σ2/M (where M is the molar mass of the nanoparticle), the quantity suitable for comparisons with other types of nonlinear absorbers.Finally, in the last chapter I have combined the results and knowledge from all previously described experiments in order to propose a new bioprobe. The probe is based on NR functionalized by DNA strand with attached fluorophore. The distance between gold surface and dye is selected in a such way as to maximize the fluorescent emission. The viability tests show low toxicity for cells and high compatibility. I showed that biofunctionalized NRs can provide fluorescent labeling of cancer cells and enable effective photothermal therapy. This is one of the first demonstrations of coupling a bioimaging application to a cancer therapy application using NRs targeted against a clinical relevant biomarker. I hope that the future studies will extend the in vitro concept demonstrated here to in vivo animal experiments.

In this work a bio-inspired flapping actuator based on varied magnetic fields is developed, controlled and characterized. The actuator is sought to contribute to the toolbox of options for bio-mimetics research. The design is that of a neodymium bar magnet on one end of an armature which is moved by two air core electromagnetic coils in the same manner as agonist and antagonist muscle pairs function in biological systems. The other end of the armature is fitted to a rigid fin extending beyond the streamline enclosure body to produce propulsion. A series of tests in still water were performed to measure the kinematics and propulsive force for different control schemes including the effect of adding antagonistic resistance to the control schemes. Control methods based on armature position and based on setpoint error were tested and antagonist force was found to increase consistency of control of the systems in certain cases. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Modeling a biological systems, is a cyclic process which involves constructing a model from current theory and beliefs and then validating that model against the data. If the data does not match, qualitatively or quantitatively then there may be a problem with either our beliefs or the current theory. At the same time directly finding a model from the existing data would make generalizing results difficult. A considerable difficultly in this process is how to specify the model in the first place. There is a need to be practice which accounts for the growing use of mathematical and statistical methods. However, as a systems becomes more complex, standard mathematical approaches may not be sufficient. In the field of ecology, the standard techniques involve discrete maps, and continuous models such as ODE's. The intent of this work is to present the mathematics necessary to study hybrids of these two models, then consider two case studies. In first case we con sider a coral reef with continuous change, except in the presence of hurricanes. The results of the data are compared quantitatively and qualitatively with simulation results. For the second case we consider a model for rabies with a periodic birth pulse. Here the analysis is qualitative as we demonstrate the existence of a strange attractor by looking at the intersections of the stable and unstable manifold for the saddle point generating the attractor. For both cases studies the introduction of a discrete event into a continuous system is done via a Dirac Distribution or Measure. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Neste trabalho, foi realizado um estudo da obtenção de nanomateriais luminomagnéticos visando potenciais aplicações biológicas, a partir de dois diferentes tipos de estruturas, sendo elas: a formação de heteronanoestruturas luminomagnéticas de NPM de FePt/Fe3O4-CdSe recobertas com sílica; e a formação de nanomateriais luminomagnéticos por ligação covalente entre NPM de FePt/Fe3O4-Dopa-PIMA-PEG-NH2 e pontos quânticos de CdSe/ZnS-LA-PEG-COOH. Para o primeiro tipo de nanomaterial citado, foram testadas duas metodologias para obtenção das heteronanoestruturas: a mudança da estabilidade coloidal pela adição de pequenas quantidades de NaCl no meio contendo as NPM e os pontos quânticos previamente sintetizados; e o método de injeção a quente do precursor de selênio em um meio contendo as NPM como sementes, o precursor de cádmio e os agentes de superfície. O método de injeção a quente foi o que apresentou melhores condições para a formação das heteronanoestruturas. Para providenciar estabilidade coloidal em meio aquoso e superfície com biocompatibilidade, foi realizado o recobrimento com sílica na superfície das heteronanoestruturas luminomagnéticas com melhores condições. Para essa amostra, o tamanho médio obtido foi de 25,0 nm, com polidispersividade de 8,4 %, Ms = 11,1 emu.g-1 e comportamento superparamagnético, além de duas bandas de emissão (com excitação de 400 nm) centradas em 452 nm e 472 nm, respectivamente. Já para o segundo tipo de nanomaterial obtido neste trabalho, foram primeiramente obtidas NPM de FePt/Fe3O4 pelo método do poliol modificado acoplado à metodologia do crescimento, e pontos quânticos luminescentes de CdSe/ZnS pelo método de decomposição térmica de precursores organometálicos, sendo que ambas nanoestruturas apresentaram superfície hidrofóbica. Para a troca de ligantes para transferência das nanoestruturas para a fase aquosa e para providenciar biocompatibilidade visando aplicações biológicas, foram previamente preparados ligantes poliméricos de Dopa-PIMA-PEG-NH2 para recobrimento das NPM e de LA-PEG-COOH para recobrimento dos pontos quânticos. A conjugação química entre as nanoestruturas de FePt/Fe3O4-Dopa-PIMA-PEG-NH2 e CdSe/ZnS-LA-PEG-COOH foi realizada pelo método da carbodiimida em solução aquosa para a formação de uma ligação covalente amida entre os grupos amina e carboxilato em cada uma das nanoestruturas. Os nanomateriais luminomagnéticos obtidos apresentaram estabilidade coloidal em meio aquoso, com estreita distribuição de tamanho, apresentando RH de 79,96 nm, Ms de, aproximadamente, 10 emu.g-1 com coercividade e remanência quase nulos e intensa banda de emissão centrada em 580 nm. Espera-se que os nanomateriais obtidos neste trabalho possam ser promissores nanomateriais com propriedades multifuncionais para potenciais aplicações biológicas. / Here, luminomagnetic nanomaterials were obtained for potential biological applications. We have studied two different types of luminomagnetic nanomaterials, which are: formation of silica-coated FePt/Fe3O4-CdSe heteronanostructures; and formation of luminomagnetic nanomaterials from covalent bond between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 magnetic nanoparticles and CdSe/ZnS-LA-PEG-COOH luminescent quantum dots. For the first type of luminomagnetic nanomaterials obtained, two methodologies were studied for formation of heteronanostructures, which are: modification of colloidal stability by addition of small amounts of NaCl into a solution with hydrophobic magnetic nanoparticles and luminescent quantum dots; and hot injection method of selenium precursor into a solution with magnetic nanoparticles seeds, cadmium precursors and surface agents. The hot injection method obtained better results than the other method studied for formation of heteronanostructures. To provide colloidal stability in aqueous solution and biocompatibility, the heteronanostructures were coated using silica shell. After silica coating, the heteronanostructures showed average diameter of 25 nm and polidispersivity of 8.4%, with Ms = 11.1 emu.g-1 and superparamagnetic behavior. Moreover, these nanomaterials showed two emission peaks centered at 452 and 472 nm. For the second type of nanomaterials obtained, FePt/Fe3O4 magnetic nanoparticles were synthesized by modified polyol method coupled to seeded-mediated growth, and CdSe/ZnS luminescent quantum dots were obtained by thermal decomposition of organometallic precursors. For the ligand exchange to transfer the nanostructures from organic media to aqueous solution, were used Dopa-PIMA-PEG-NH2 and LA-PEG-COOH polymers to provide colloidal stability and biocompatibility on magnetic nanoparticle surface and quantum dot surface, respectively. The chemical conjugation between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 and CdSe/ZnS-LA-PEG-COOH nanostructures was obtained by EDC coupling in aqueous solution, which linked amine and carboxylate groups in each nanostructure to provide the formation of amide bond. The luminomagnetic nanomaterials obtained showed colloidal stability in aqueous solution, narrow size distribution, with RH equal to 79.96 nm, MS around 10 emu.g-1 with low coercivity and remanent magnetization, and intense emission peak centered at 580 nm. We expect these luminomagnetic nanomaterials be promisor nanomaterials with multifunctional properties for potential biological applications.

Neste trabalho, foi realizado um estudo da obtenção de nanomateriais luminomagnéticos visando potenciais aplicações biológicas, a partir de dois diferentes tipos de estruturas, sendo elas: a formação de heteronanoestruturas luminomagnéticas de NPM de FePt/Fe3O4-CdSe recobertas com sílica; e a formação de nanomateriais luminomagnéticos por ligação covalente entre NPM de FePt/Fe3O4-Dopa-PIMA-PEG-NH2 e pontos quânticos de CdSe/ZnS-LA-PEG-COOH. Para o primeiro tipo de nanomaterial citado, foram testadas duas metodologias para obtenção das heteronanoestruturas: a mudança da estabilidade coloidal pela adição de pequenas quantidades de NaCl no meio contendo as NPM e os pontos quânticos previamente sintetizados; e o método de injeção a quente do precursor de selênio em um meio contendo as NPM como sementes, o precursor de cádmio e os agentes de superfície. O método de injeção a quente foi o que apresentou melhores condições para a formação das heteronanoestruturas. Para providenciar estabilidade coloidal em meio aquoso e superfície com biocompatibilidade, foi realizado o recobrimento com sílica na superfície das heteronanoestruturas luminomagnéticas com melhores condições. Para essa amostra, o tamanho médio obtido foi de 25,0 nm, com polidispersividade de 8,4 %, Ms = 11,1 emu.g-1 e comportamento superparamagnético, além de duas bandas de emissão (com excitação de 400 nm) centradas em 452 nm e 472 nm, respectivamente. Já para o segundo tipo de nanomaterial obtido neste trabalho, foram primeiramente obtidas NPM de FePt/Fe3O4 pelo método do poliol modificado acoplado à metodologia do crescimento, e pontos quânticos luminescentes de CdSe/ZnS pelo método de decomposição térmica de precursores organometálicos, sendo que ambas nanoestruturas apresentaram superfície hidrofóbica. Para a troca de ligantes para transferência das nanoestruturas para a fase aquosa e para providenciar biocompatibilidade visando aplicações biológicas, foram previamente preparados ligantes poliméricos de Dopa-PIMA-PEG-NH2 para recobrimento das NPM e de LA-PEG-COOH para recobrimento dos pontos quânticos. A conjugação química entre as nanoestruturas de FePt/Fe3O4-Dopa-PIMA-PEG-NH2 e CdSe/ZnS-LA-PEG-COOH foi realizada pelo método da carbodiimida em solução aquosa para a formação de uma ligação covalente amida entre os grupos amina e carboxilato em cada uma das nanoestruturas. Os nanomateriais luminomagnéticos obtidos apresentaram estabilidade coloidal em meio aquoso, com estreita distribuição de tamanho, apresentando RH de 79,96 nm, Ms de, aproximadamente, 10 emu.g-1 com coercividade e remanência quase nulos e intensa banda de emissão centrada em 580 nm. Espera-se que os nanomateriais obtidos neste trabalho possam ser promissores nanomateriais com propriedades multifuncionais para potenciais aplicações biológicas. / Here, luminomagnetic nanomaterials were obtained for potential biological applications. We have studied two different types of luminomagnetic nanomaterials, which are: formation of silica-coated FePt/Fe3O4-CdSe heteronanostructures; and formation of luminomagnetic nanomaterials from covalent bond between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 magnetic nanoparticles and CdSe/ZnS-LA-PEG-COOH luminescent quantum dots. For the first type of luminomagnetic nanomaterials obtained, two methodologies were studied for formation of heteronanostructures, which are: modification of colloidal stability by addition of small amounts of NaCl into a solution with hydrophobic magnetic nanoparticles and luminescent quantum dots; and hot injection method of selenium precursor into a solution with magnetic nanoparticles seeds, cadmium precursors and surface agents. The hot injection method obtained better results than the other method studied for formation of heteronanostructures. To provide colloidal stability in aqueous solution and biocompatibility, the heteronanostructures were coated using silica shell. After silica coating, the heteronanostructures showed average diameter of 25 nm and polidispersivity of 8.4%, with Ms = 11.1 emu.g-1 and superparamagnetic behavior. Moreover, these nanomaterials showed two emission peaks centered at 452 and 472 nm. For the second type of nanomaterials obtained, FePt/Fe3O4 magnetic nanoparticles were synthesized by modified polyol method coupled to seeded-mediated growth, and CdSe/ZnS luminescent quantum dots were obtained by thermal decomposition of organometallic precursors. For the ligand exchange to transfer the nanostructures from organic media to aqueous solution, were used Dopa-PIMA-PEG-NH2 and LA-PEG-COOH polymers to provide colloidal stability and biocompatibility on magnetic nanoparticle surface and quantum dot surface, respectively. The chemical conjugation between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 and CdSe/ZnS-LA-PEG-COOH nanostructures was obtained by EDC coupling in aqueous solution, which linked amine and carboxylate groups in each nanostructure to provide the formation of amide bond. The luminomagnetic nanomaterials obtained showed colloidal stability in aqueous solution, narrow size distribution, with RH equal to 79.96 nm, MS around 10 emu.g-1 with low coercivity and remanent magnetization, and intense emission peak centered at 580 nm. We expect these luminomagnetic nanomaterials be promisor nanomaterials with multifunctional properties for potential biological applications.

In this thesis we summarise several results in the literature which show the approximation capabilities of multilayer feedforward artificial neural networks. We show that multilayer feedforward artificial neural networks are capable of approximating continuous and measurable functions from Rn to R to any degree of accuracy under certain conditions. In particular making use of the Stone-Weierstrass and Hahn-Banach theorems, we show that a multilayer feedforward artificial neural network can approximate any continuous function to any degree of accuracy, by using either an arbitrary squashing function or any continuous sigmoidal function for activation. Making use of the Stone-Weirstrass Theorem again, we extend these approximation capabilities of multilayer feedforward artificial neural networks to the space of measurable functions under any probability measure.

In this note we explain the use of the Akiake Information Criterion and its related model comparison indices (usually derived for maximum likelihood estimator inverse problem formulations) in the context of least squares (ordinary, weighted, iterative weighted or “generalized”, etc.) based inverse problem formulations. The ideas are illustrated with several examples of interest in biology.

The present work describes a selection of strategies for the synthesis of functional aliphatic polycarbonates. Using an end-group functionalization strategy, a series of DNA-binding cationic poly(trimethylene carbonate)s was synthesized for application as vectors for non-viral gene delivery. As the end-group functionality was identical in all polymers, the differences observed in DNA binding and in vitro transfection studies were directly related to the length of the hydrophobic poly(trimethylene carbonate) backbone and the number of functional end-groups. This enabled the use of this polymer system to explore the effects of structural elements on the gene delivery ability of cationic polymers, revealing striking differences between different materials, related to functionality and cationic charge density. In an effort to achieve more flexibility in the synthesis of functional polymers, polycarbonates were synthesized in which the functionalities were distributed along the polymer backbone. Through polymerization of a series of alkyl halide-functional six-membered cyclic carbonates, semicrystalline chloro- and bromo-functional homopolycarbonates were obtained. The tendency of the materials to form crystallites was related to the presence of alkyl as well as halide functionalities and ranged from polymers that crystallized from the melt to materials that only crystallized on precipitation from a solution. Semicrystallinity was also observed for random 1:1 copolymers of some of the monomers with trimethylene carbonate, suggesting a remarkable ability of repeating units originating from these monomers to form crystallites. For the further synthesis of functional monomers and polymers, azide-functional cyclic carbonates were synthesized from the bromo-functional monomers. These were used as starting materials for the click synthesis of triazole-functional cyclic carbonate monomers through Cu(I)-catalyzed azide–alkyne cycloaddition. The click chemistry strategy proved to be a viable route to obtain structurally diverse monomers starting from a few azide-functional precursors. This paves the way for facile synthesis of a wide range of novel functional cyclic carbonate monomers and polycarbonates, limited only by the availability of suitable functional alkynes.