Dissertations / Theses on the topic 'Colloidal Probes'

Los polímeros de coordinación y su diseño racional permiten la formación de materiales nanoestructurados con una amplia variedad de propiedades. Las múltiples combinaciones entre iones metálicos y ligandos orgánicos como precursores de materiales autoensamblados, han fascinado a los científicos durante décadas. La aplicación de la química de coordinación a nanoescala se considera uno de los enfoques más versátiles para el desarrollo de nuevos materiales nanoestructurados debido a las infinitas posibilidades para alcanzar propiedades sin precedentes. Además, el desarrollo de sistemas metal-orgánicos ha despertado en una gran cantidad de ejemplos para su uso en una amplia gama de aplicaciones. En esta Tesis hemos estado particularmente interesados ​​en el ajuste controlado de las propiedades de los materiales nanoestructurados basados ​​en polímeros de coordinación que se obtuvieron a través de diferentes rutas sintéticas. El método de síntesis, la selección adecuada de precursores y el estudio de las propiedades finales han centrado el trabajo realizado. Además, la formación de suspensiones coloidales estables en agua se estableció como un requisito principal para su potencial aplicación. Para eso, fue necesaria una sinergia multidisciplinaria con el objetivo de buscar la aplicación final de los nuevos materiales nanoestructurados desarrollados. El logro de este objetivo fue posible gracias a un diseño adecuado de la estrategia seguida junto con la caracterización completa de las nanoestructuras preparadas. En una primera parte de esta Tesis, la nanoestructuración de sistemas conmutables basados ​​en Fe(II) con comportamiento de entrecruzamiento de espín (SCO por sus siglas en inglés) se logró siguiendo dos estrategias diferentes. Por un lado, se aplicó una metodología descendente (top-down) basada en la exfoliación en fase líquida para el aislamiento de láminas 2D de cristales multilaminares. Por otro lado, a través de un enfoque ascendente (bottom-up), la síntesis de nuevas nanopartículas fue posible modulando la difusión de la reacción utilizando metodologías basadas en microfluidica. En ambos casos, los materiales nanoestructurados se integraron en matrices poliméricas para evaluar su aplicación potencial como películas termocrómicas para su prueba de concepto. En la segunda parte de la Tesis, se estableció una nueva familia de polímeros de coordinación a nanoescala (NCP por sus siglas en inglés) basados ​​en Fe(III), Gd(III), Mn(II), In(III) y Cu(II) a través de su síntesis racional usando una reacción en un sola etapa. Las nanopartículas obtenidas se validaron mediante pruebas preclínicas in vivo que muestran un rendimiento interesante como posibles agentes teranósticos para la obtención de imágenes (resonancia magnética, tomografía por emisión de positrones y tomografía computarizada por emisión de fotón único) y pretratamiento potencial de glioblastoma y enfermedades pulmonares.
Coordination polymers and its rational design let the formation of nanostructured materials with a broad variety of properties. The multiple combinations between metal ions and organic ligands as precursors of self-assembled materials have fascinated scientists for decades. The application of coordination chemistry at the nanoscale is considered one of the most versatile approaches for the development of new nanostructured materials due to the infinite possibilities for reaching unprecedented properties. Furthermore, the development of metal-organic systems has aroused in a plethora of examples for their use in a wide range of applications. In this Thesis we have been particularly interested in the fine tune of the properties of nanostructured materials based on coordination polymers whose were obtained through different synthetic routes. The method of synthesis, the properly selection of precursors and the study of the final properties has centred the work carried out. Additionally, the formation of water-stable colloidal suspensions was stablished as a main requirement for their potential application. For that, a multidisciplinary synergy was necessary with the aim to pursue the final application of the novel nanostructured materials developed. Achieving this objective was possible thanks to a properly design of the strategy followed together with complete characterization of the nanostructures prepared. In a first part of this Thesis, the nanostructuration of Fe(II)-based switchable systems with spin crossover behaviour was achieved by following two different strategies. On the one hand, a top-down methodology based on liquid-phase exfoliation was applied for the isolation of 2D flakes from the bulk crystal. On the other hand, through a bottom-up approach, the synthesis of novel nanoparticles was possible by modulating the reaction diffusion using microfluidic based methodologies. In both cases, the nanostructured materials were integrated in polymeric matrices to evaluate their potential application as proof-of-concept thermochromic films. In the second part of the Thesis, a novel family of nanoscale coordination polymers (NCPs) based on Fe(III), Gd(III), Mn(II), In(III) and Cu(II) was stablished through its rational synthesis by using one-pot reaction. The nanoparticles obtained were validated by pre-clinical in vivo tests showing interesting performance as potential theranostic agents for imaging (Magnetic resonance imaging, positron emission tomography and single-photon emission computed tomography) and potential pre-treatment of glioblastoma and lung diseases.

The study of the DNA has found application beyond our understanding of its cellular function and into a variety of materials assembly and nucleic acid detection systems. The current research investigates double-stranded DNA probes in both a colloidal particle assembly and fluorescent assay format utilizing competitive hybridization events. In both contexts, the affinity of the dsProbes is tuned by the sequence design parameters of duplex length and complementarity. These systems were incubated with nucleic acid targets of interest and, based on the mechanism of competitive hybridization, were responsive to the presence of a high affinity competitive target. In the case of the particle assemblies, incubation with the competitive target resulted in observable disassembly of particle structures. In the case of fluorescently labeled dsProbes, incubation with competitive targets resulted in a quantifiable loss of fluorescence as determined by flow cytometry. Utilizing the fluorescently labeled dsProbe system, the kinetics of competitive hybridization was characterized for nucleic acid targets of varying specificity and strand context. The results indicate promise for the development of the competitive hybridization approach in nucleic acid detection systems providing advantages over current single-stranded probe designs. By utilizing a fluorescently labeled dsProbe approach, it is unnecessary to chemically modify the target of interest to impart a signaling mechanism. Additionally, as the process of competitive hybridization of dsProbes with targets of interest is an affinity driven process, discrimination of targets based on specificity is decoupled from standard measures such as elevated temperature protocols, an important step in translating nucleic acid technologies from the controlled laboratory environment to field applications.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2008.
Vita.
Includes bibliographical references.
This thesis employs colloidal semiconductor nanocrystals (NCs) as nanoscale emissive probes to investigate the physics of light emitting diodes (LEDs), as well as to unveil properties of cells that conventional imaging techniques cannot reveal. On the LED side, in particular, Chapter 2 utilizes individual NCs to alter layered organic LED structures at nanometer scale, resulting in spectrally resolved electroluminescence from single colloidal CdSe/ZnS (core/shell) NCs at room temperature. Chapter 3 takes NCs as emissive probes in layered organic LEDs, and shows that the photoluminescence of single NCs is bias dependent which helps elucidate the interactions between NCs and organic semiconductors, knowledge useful for designing efficient NC organic optoelectronics. Instead of using a planar LED geometry, Chapter 4 presents a technique for making nanoscale gap LEDs which allow the spectrally coincidental photoluminescence and electroluminescence from NCs. The work investigates the interactions between NCs and different metal gaps, and suggests electromigrating leads made of different metals as a promising route to fabricating nanoscale gaps with workfunction offsets for optoelectronic devices. On the cell biology side, we develop a three-dimensional sub-diffraction limited single fluorophore imaging method for proteins labeled with NCs. Chapter 5 applies the method to measure the endothelial glycocalyx thickness in vitro for the first time, by labeling different proteins with NCs of different emission wavelengths. Taking a step further, Chapter 6 utilizes the NC based imaging method to investigate the flow induced dynamics of endothelial glycocalyx, and measures the shear modulus of glycocalyx.
by Hao Huang.
Ph.D.

In this dissertation, we describe a novel method that we call Diffusing Colloidal Probe Microscopy (DCPM), which integrates Total Internal Reflection Microscopy (TIRM) and Video Microscopy (VM) methods to monitor three dimensional trajectories in colloidal ensembles levitated above macroscopic surfaces. TIRM and VM are well established optical microscopy techniques for measuring normal and lateral colloidal excursions near macroscopic planar surfaces. The interactions between particle-particle and particle-substrate in colloidal interfacial systems are interpreted by statistical analyses from distributions of colloidal particles; dynamic properties of colloidal assembly are also determined from particle trajectories. Our studies show that DCPM is able to detect many particle-surface interactions simultaneously and provides an ensemble average measurement of particle-surface interactions on a homogeneous surface to allow direct comparison of distributed and average properties. A benefit of ensemble averaging of many particles is the diminished need for time averaging, which can produce orders of magnitude faster measurement times at higher interfacial particle concentrations. The statistical analyses (Ornstein- Zernike and three dimensional Monte Carlo analyses) are used to obtain particle-particle interactions from lateral distribution functions and to understand the role of nonuniformities in interfacial colloidal systems. An inconsistent finding is the observation of an anomalous long range particle-particle attraction and recovery of the expected DLVO particle-wall interactions for all concentrations examined. The possible influence of charge heterogeneity and particle size polydispersity on measured distribution functions is discussed in regard to inconsistent particle-wall and particle-particle potentials. In the final part of this research, the ability of DCPM is demonstrated to map potential energy landscapes on patterned surfaces by monitoring interactions between diffusing colloidal probes with Au pattern features. Absolute separation is obtained from theoretical fits to measured potential energy profiles and direct measurement by sticking silica colloids to Au surfaces via electrophoretic deposition. Initial results indicate that, as colloidal probe and pattern feature dimensions become comparable, measured potential energy profiles suffer some distortion due to the increased probability of probes interacting with surfaces at the edges of adjacent pattern features. Measurements of lateral diffusion via analysis of mean square displacements also indicated lateral diffusion coefficients in excellent agreement with rigorous theoretical predictions.

The role of forces is fundamental in a wide variety of biological processes, such as cell adhesion, migration, proliferation and differentiation. The ability of cells to perceive the nanotopographical features of the surrounding microenvironment (i.e. the extracellular matrix, ECM), called mechanotransduction, is mediated by specific trans-membrane proteins, called integrins, clustered together in Integrin Adhesion Complexes (IAC). Unraveling which mechanical and nanoscale morphological properties of the ECM determine the IAC composition and tune specific cellular response, is particularly challenging. Works have shown that biocompatible nanostructured thin films, grown by assembling zirconia nanoparticles (ns-ZrO2) on a substrate by Supersonic Cluster Beam Deposition technique, possess a morphological disorder on nanometer scale with structural features that mimic topographical properties of the ECM. Experiments performed with the neuron-like cell line PC12 demonstrated a link between the nanotopography of the ns-ZrO2 films and mechanotransductive events, which eventually foster neuronal differentiation. During my three years of PhD, I have developed novel approach based on Atomic Force Microscopy (AFM) to quantify cell sensing of nanotopographical features of the microenvironment, represented by ns-ZrO2 films reproducing the nanostructured surface of the ECM. Using custom ns-ZrO2–coated colloidal probes, we have carried out a quantitative analysis of adhesion strength and distribution of IACs by AFM-based adhesive force spectroscopy. We deposited ns-ZrO2 on custom AFM colloidal probes5. Bringing these nanostructured colloidal probes into contact with the body of living PC12 cells, it was possible to measure the strength, number and distribution of the IAC bonds by AFM force spectroscopy6, for different morphological properties of the interface. Furthermore, I used these functionalized probes to characterize the role of the surface pericellular layer, known as the Glycocalyx, in relation to the cell capability to react to external stimuli. Eventually, along with my personal research project, I had the opportunity to participate to two external collaboration with the Istituto Nazionale dei Tumori and with Istitute of Nuclear Physiscs from the Polish academy of Science. These collaborations aimed to exploit the knowledge in the mechanobiolgy field to study the mechanical implications of cells and tissues in cancer development and survival.

In this thesis I will describe my experimental work based on ultrafast optical spectroscopy techniques applied to colloidal nanocrystals. Colloidal semiconductor nanocrystals in recent years have attracted a lot of attention in particular in optoelectronic applications, because they present unique optical, electronic and charge carrier transport properties that can be easily modified via colloidal chemical synthesis. In the first chapter of this thesis, I will introduce the basic concepts of nanocrystals and their optical properties, I will consider some simple models to explain the physical properties of semiconductor nanocrystals. I will briefly describe the colloidal chemical synthesis of these nanocrystals and how we can change the optical properties by simply acting on the colloidal chemical synthesis. In the second chapter I will describe the basic concepts of ultra fast optical spectroscopy techniques used in my experimental work. I will describe the basic principles and the experimental set-up of the two main techniques that I used: time-resolved photoluminescence spectroscopy (TR-PL) and transient absorption spectroscopy or also called Pump Probe. These two techniques allow to investigate in a very precise way the main optical properties and dynamics of charge carriers in nanocrystals. In the third chapter I will describe my experimental work based on timeresolved photoluminescence spectroscopy applied to CdSe=CdS core=shell nanocrystals. These nanocrystals are a reference nanocrystals and their optical properties are extensively investigated, however, some aspects are not fully understood, for example, the instability or blinking of the light emission under constant illumination in these nanocrystals is still an unsolved problem that limits the real applications. The particular spectroscopic technique that I have used variable pulse rate photoluminescence spectroscopy revealed the causes of this issue, and will give us a solution to resolve it. In the fourth chapter I will discuss novel nanostructures of CdSe=CdS multi branched shape, in this case octapod shaped nanocrystals consist of eight arms made of CdS grown on a CdSe core, these present a large crosssection for light absorption and efficient charge separation ideally suited for applications of photocatalysis. The optical spectroscopy technique used to investigate the properties of these nanocrystals are the transient absorption spectroscopy. In the fifth chapter I will discuss experimental work on Bi2S3 semiconductor nanocrystals and I will describe related optical techniques used to study the optical and electronic properties. This nanocrystal has excellent properties of optical absorption of solar radiation and can be used for the realization of solar cells. Another important property of Bi2S3 is its nontoxicity that will allow in the future to achieve efficient solar cells and easy disposal and simultaneously not damaging to the environment.

In this work, microfluidic and millifluidic droplets are utilized to study and control complex fluid behavior with high composition resolution. Different techniques are used on two length scales to create unique approaches towards the same goal of merging droplet-based experiments with classical colloidal characterization experiments. First, a microfluidic dehydrating droplet device is characterized and a procedure established by concentrating a phase separating organic-inorganic system on chip and using geometric calculations to determine composition. The device is then expanded to a more complex, particle-polymer system to investigate suspension stability and interparticle behavior. A model system containing silica particles and PEO polymer is found to transition from a bridging flocculation mechanism to polymer-coated particle jamming based on the mass ratio of polymer to particle. Lastly, a phase separating particle-polymer system consisting of polystyrene particles and hydroxyethyl cellulose is concentrated on-chip. Interparticle interactions are controlled by varying particle size, polymer size, and polymer type and the effects on phase behavior are examined. Droplet experiments are scaled-up to millifluidic droplets and concentration gradients are used to produce high composition resolution in place of time, used in the dehydrating microfluidic experiments. A novel, millifluidic containment device is created to study aggregation and sedimentation in droplets containing carbon black and OLOA surfactant suspended in dodecane. A slow increase in stabilization behavior is observed as opposed to the previously observed sharp “on-off” effect. The droplet production technique is then improved to achieve more complex composition paths and the device is expanded for a small angle neutron scattering (SANS) application. SANS is performed on flowing droplets with varying concentration to map interparticle interactions and phase behavior of complex particulate systems. Feasibility of device is demonstrated and preliminary model systems of silica particles and polymer, salt, and surfactant are analyzed and characterized.

Recent research has shown that Newtonian liquids can slip at solid surfaces in confined geometries, which contradicts the classical no-slip boundary condition in which the liquid is stationary at the solid surface. The study of liquid boundary conditions that provides a fundamental understanding of the physics of liquid flow in confined geometries, such as in porous media, and also could benefit various commercial applications, such as micro and nanofluidic applications. The aim of our work was to build a reliable experimental and theoretical framework to investigate liquids slip on solid surfaces by colloid probe atomic force microscopy (AFM). Colloid probe AFM provides an accurate way to study slip at a solid surface by measuring the hydrodynamic drainage force between a colloid probe and a solid substrate as the two surfaces approach to contact. In our studies, we have investigated the slip of a one-component viscous liquid (di-n-octylphthalate) on bare silicon substrates and hydrophobised silicon substrates. In order to obtain reliable slip results, we solved experimental problems in previously published experiments and improved the theoretical modeling which affects the reliability and accuracy of the measured slip lengths. In the new improved experimental protocol we used a closed loop scanner to produce a constant driving velocity, minimised the virtual deflection due to top-scan AFM by removing a constant slope in the force curve, and clarified the true compliance and zero separation in the force curve. The need for tight control over experimental conditions in slip measurements was highlighted, such as extremely careful surface cleaning, the use of a one-component liquid, continuous monitoring of the liquid temperature, and repeat measurements in different locations of the substrate. By performing slip measurements in symmetric and asymmetric systems, a new method was developed to self-assess the accuracy and reproducibility of the slip force measurements. A new mathematical algorithm was built to predict the hydrodynamic drainage force independently of experimental data. This new mathematical algorithm reduced the noise greatly in the theoretical forces over that in the previous treatments; it was demonstrated by blind test that this new calculation method provides reproducible and reliable slip length values and spring constant values with the uncertainty within 3%. The new mathematical algorithm can be easily applied to simulate slip lengths and hydrodynamic forces in different experimental conditions, such as the presence of nanoparticle contamination on the substrate surface and the flattening of the colloid probe, which were both demonstrated to affect the measured slip lengths. The exact variable drag force on soft cantilevers was calculated for the first time and applied to fit the experimental force. This calculation revealed that the dependence of slip on the driving velocity and the cantilever shape found in literature could be a spurious effect due to the assumption that the drag force on the cantilever is constant during force measurements. In our studies, it was also shown that the measured slip length actually decreases with increasing shear rate, rather than being a constant value as commonly assumed. A new shear dependent model for slip fitted well experimental hydrodynamic forces for all separations down to a few nanometres. A possible molecular explanation was proposed for the mechanism of shear rate dependent slip in our experiments.

"Polyelectrolyte multilayer (PEM) thin films prepared via the Layer-by-Layer (LbL) deposition technique are of special interest in this research. The purpose of this study is to replace current mechanical closure systems, based on hook-and-loop type fasteners (i.e. Velcro), with PEM thin film systems. The technique is simple, cheap, versatile and environmental friendly; as a consequence a variety of thin films can be easily fabricated. By proposing PEMs as non-mechanical and nanoscopic molecular closures, we aim to obtain hermetic sealing, good adhesive strength, and peel off ease. Atomic force microscopy (AFM) and colloidal probe techniques were used to characterize the morphology, roughness and adhesive properties of PEMs. AFM measurements were conducted in air, necessarily requiring careful control of ambient humidity. PEMs were formed by consecutive deposition of polyanions and polycations on a charged polyethylene terephthalate (PET) solid surface, the result of which was stable nanostructured films. By systemically varying the parameters of PEM build-up process: different combinations of polyelectrolytes, different numbers of bilayers (polyanion/polycation pairs), and miscellaneous types and concentrations of salts (NaCl, NaBr and NaF salts at 0.5 M and 1.0 M concentrations), the adhesion and morphology of PEMs were thoroughly investigated. The PEM thin films specifically investigated include poly(ethyleneimine) (PEI), poly(styrene sulfonate) (PSS), poly(allylamine hydrochloride) (PAH), poly(acrylic acid) (PAA), and poly(diallydimethylammonium chloride) (PDADMAC). Silica colloidal probes were utilized in the investigation, some of which were functionalized with COOH and/or coated with PEI-PSS. Silica colloidal probes were used in order to quantify interaction forces on the PEMs. A functionalized silica colloidal probe (a probe with COOH surface chemistry) and a silica colloidal probe coated with PEI-PSS were used to simulate PEM-PEM interactions. The results suggest that adhesion in the PEMs depend on the number of layers, the salt concentration and the salt type used during the build-up process, the environmental conditions where the adhesion force measurements were made, and the choice of probe. "

Warfarin is a well-known anticoagulant drug that is used to prevent cardiovascular disease and blood coagulation such as thrombosis. In this study, the main aim was to investigate the photo physical characteristics of warfarin in the different molecular environments provided by sodium dodecyl sulfate (SDS) micelles by using ultraviolet absorption and fluorescence emission spectroscopic techniques. Warfarin and a structural analogue not existing in solution as a cyclic hemiketal, phenprocoumon, were mixed with different concentrations of SDS and spectral changes for these warfarin and phenprocoumon were recorded. Interestingly, results demonstrated, based on an evident increase in the absorption intensity at 273 nm and an evident blue shift in the fluorescence emission spectrum after the addition of an increasing concentration of SDS, that primarily the cyclic hemiketal isomer of warfarin was found to be solvated by SDS micelles at an apparent recorded critical micelle concentration of ~8mM.  Altogether these observations suggest that warfarin may be used as a molecular probe to explore the polarities of complex colloidal mixtures. Moreover, the possibility of using micelles for controlling the isomeric state of warfarin is interesting and can potentially be used for better controlling dosage of warfarin thereby reducing side effects.

In the first part of this thesis, we study the kinetics of the complexation of a double-stranded DNA byNCp7 protein. To do this, we study the evolution of mechanical properties of DNA and its complexation by stretching the DNA/NCp7 complex with a optical trap. We observed that the persistence length of the complex decreases progressively during the complexation. Using astatistical model we describe the evolution of the flexibility of DNA complexed with NCp7. Our main result is that the fraction phi of base pairs that have reacted is not a linear function of time at low phi.We interpret our results assuming that the adsorption of NCp7 on DNA is highly cooperative. In the second chapter, we describe the dynamics of probe particles in a colloidal glassy suspension of Laponite. Laponite is a colloidal discoidal particle of 25 nm in diameter and 0.92 nm thick. We take advantage of evanescent wave microscopy, and follow the movement of fluorescent latex particles.Then we image these particles. We show that for a movement that has a single characteristic time scale, it is simply a linear function of time. We find that, what ever their size, the motion of probe particles can be described by a succession of two dynamic modes, where the fastest mode corresponds to the diffusion of particles in a viscoelastic fluid.

The topic of this thesis is investigation of models applied to different aspects of separations and colloid science. Many tools are used for solving the models, which are manifested as boundary value problems. The problems are to determine the equilibrium electrostatics of a fluid droplet, the electrokinetics of such, the (nonuniform) temperature profile of an electrophoresis capillary due to Joule heating, and the temperature at the wall of the capillary. In the fluid drop model, special attention given to a drop that, in addition to the surrounding fluid, supports electrolytes. Matched asymptotic expansions based on thin double layers are applied to the equilibrium electrostatics problem. Attention is given to how conditions on the interface of the drop, such as discontinuity of equilibrium potential and the presence of surface excesses of solutes, affect the electrokinetics. A perturbation scheme is used to formulate a problem for the electrophoretic mobility of a droplet. An approximate solution for the mobility of a drop is derived, based on small interfacial potentials. The formula encompasses those of several past theoretical studies. A regular perturbation is used to determine heating effects in capillary electrophoresis, based on a small power input to the system. The resulting expression for temperature in the capillary is then used implicitly to determine the temperature at the wall of the capillary. Some of the results are compared with experimental data. For the drop electrophoresis problem, the electrophoretic mobility formula is compared with measured mobility of oil drops and drops in aqueous two-phase systems. In the study of heating in capillary electrophoresis, the implicit expression is used to make reasonable estimates of the wall temperature based on published operating conditions. Accuracy of all analytic estimates of the problems are tested against numerical solutions, taken to be exact. In all cases, the analytic approximations are satisfactorily accurate under appropriate conditions.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.
Zhang, John, Committee Member ; Wang, Zhong, Committee Member ; El-Sayed, Mostafa, Committee Chair ; Orlando, Thomas, Committee Member ; Lyon, Andrew, Committee Member.

Adhesion between different objects is happening everywhere. Without it, simple procedures like walking or holding something in a hand or attaching a postage stamp would be impossible. The life itself depends on adhesion on all levels, starting from the interactions between the living cells. Adhesion between two substrates is a complex phenomenon, which at present is still not well understood. There are several factors determining the strength of adhesion: (i) molecular interactions at interface, (ii) mechanical properties of adhesive, and (iii) area of contact between adhesive and probing surface. Two surfaces are tacky when they possess the right balance between these factors. Controlling the adhesion of materials is important in many fields ranging from industrial purposes to biomedical applications and everyday usage. There is a demand for “smart” materials with integrated functionalities that make them responsive, switchable, biocompatible, anti-bacterial, more energy efficient, or autonomous. In particular, materials for such cutting-edge applications like cell culture, drug delivery, tissue engineering, biosensors, anti/biofouling, microfluidics, climbing robots, sport equipment and many others require adjustable/tuneable adhesive properties. Many efforts were directed towards fabrication of materials with either weak or strong adhesion depending on the field of application. However, design of “smart” surfaces with reversibly switchable/controllable adhesion is still a highly challenging task. Therefore, the thesis aims on design of smart polymeric materials with responsive / adaptive adhesion properties. For this, fabrication and investigation of two types of switchable polymer layers based on stimuli-responsive polymer brushes will be performed. The first group is dealing with thermoresponsive polymer brushes: poly-(N-isopropylacrylamide) and two types of biocompatible polyethylene glycol-based systems. These polymer layers undergo phase transition below and above LCST between hydrophilic and hydrophobic states. The second part of the work is related to solvent-responsive comb-like and block copolymer brushes consisted of hydrophilic PEG and hydrophobic PDMS biocompatible and biodegradable polymers.

Cancer is a disease that varies dramatically from person to person due to the specifics of the individual's physiology and the source of the cancer. In most cases, the origin of the cancer can be determined but metastasis can lead to tumors anywhere and thus many cancers require treatment of the whole body. Since many of the drugs that are used to treat cancer are toxic to healthy cells as well as cancerous ones, there has been considerable interest in developing ways to convey the drug specifically to the cancer cells with minimal exposure to healthy cells. Colloid drug delivery vehicles have shown considerable progress toward this end, while also reducing degradation of the drug prior to delivery to targeted sites (particularly important for oligonucleotide and protein therapeutics), and controlling release rates. Toward the end of improved drug delivery, this thesis work investigates the encapsulation of DNA in gelatin microspheres (GMS) and the subsequent temperature controlled release of the encapsulated DNA from these GMS. DNA-loaded GMS were then used as templates for colloidal satellite assemblies and the released DNA was shown to competitively displace the original partner strands of immobilized DNA on the surface of the assemblies. To support these investigations, hybridization of DNA at colloidal surfaces was also investigated using in situ measurements and found to significantly deviate from solution behavior. DNA hybridization is of particular interest as means of controlling the functionality of colloidal structures because it is uniquely reversible and tunable as well as biocompatible. Gelatin was chosen as the encapsulation matrix for its superior biocompatibility, convenient gel to liquid phase transition at ~35 oC, and economical availability.

Doctor of Philosophy
Department of Physics
Bruce M. Law
Three diverse first author surfaces science experiments conducted by Sean P. McBride 1-3 will be discussed in detail and supplemented by secondary co-author projects by Sean P. McBride, 4-7 all of which rely heavily on the use of an atomic force microscope (AFM). First, the slip length parameter, b of liquids is investigated using colloidal probe AFM. The slip length describes how easily a fluid flows over an interface. The slip length, with its exact origin unknown and dependencies not overwhelming decided upon by the scientific community, remains a controversial topic. Colloidal probe AFM uses a spherical probe attached to a standard AFM imaging tip driven through a liquid. With the force on this colloidal AFM probe known, and using the simplest homologous series of test liquids, many of the suspected causes and dependencies of the slip length demonstrated in the literature can be suppressed or eliminated. This leaves the measurable trends in the slip length attributed only to the systematically varying physical properties of the different liquids. When conducting these experiments, it was realized that the spring constant, k, of the system depends upon the cantilever geometry of the experiment and therefore should be measured in-situ. This means that the k calibration needs to be performed in the same viscous liquid in which the slip experiments are performed. Current in-situ calibrations in viscous fluids are very limited, thus a new in-situ k calibration method was developed for use in viscous fluids. This new method is based upon the residuals, namely, the difference between experimental force-distance data and Vinogradova slip theory. Next, the AFM’s ability to acquire accurate sub nanometer height profiles of structures on interfaces was used to develop a novel experimental technique to measure the line tension parameter, τ, of isolated nanoparticles at the three phase interface in a solid-liquid-vapor system. The τ parameter is a result of excess energy caused by the imbalance of the complex intermolecular forces experienced at the three phase contact line. Many differences in the sign and magnitude of the τ parameter exist in the current literature, resulting in τ being a controversial topic.

Biological samples like cells and Extracellular matrices (ECMs) may be classified among the most challenging specimens, mainly due to their intrinsic complexity, which manifests itself at multiple levels, from the nano- to the microscale. Nevertheless, the relevance of an in-depth study of the biophysical properties and reciprocal interactions of cells and ECMs is undeniable, since the established evidence of a strong correlation between the latter, and the physiopathological state of tissues and organisms. In particular, in the last decades the mechanical phenotype of cells and tissues turned out to be an important biophysical marker of hidden and fine-tuned molecular processes. In this context, the Atomic Force Microscope (AFM) offers a strong support to standard biochemical techniques, mainly thanks to its great versatility, which allows on the one hand to map simultaneously the topography and diverse physico-chemical properties of the sample; on the other hand, it allows matching the typical physical dimensions of the system under study by a suitable choice of the probe. In the light of these considerations, the first goal of my PhD project has been the development of a comprehensive and quantitative protocol for the AFM-based topographic and mechanical imaging of living cells, ECMs, and tissues. This, in turn, has provided a solid background for the investigation of biologically relevant systems: the mechanisms at the basis of cell adhesion and migration processes; the interplay between cells and ECMs in the framework of colorectal carcinoma and inflammatory bowel disease progression; the quantitative characterization of the mechanotransductive events promoting the differentiation of neuron-like cells cultured on biomimetic nanostructured substrates, produced by means of Supersonic Cluster Beam Deposition. The results obtained can provide a significant progress towards the effective standardization of AFM-based mechanical characterization of soft and biological samples, with potential applications in the fields of clinical and regenerative medicine.

The object of this work is to obtain a fundamentalunderstanding of the principal issues concerning the handlingof an aqueous WC-Co powder suspension.

The WO3 surface layer on the oxidised tungsten carbidepowder dissolves at pH>3 with the tungsten concentrationincreasing linearly with time. Adding cobalt powder to thetungsten carbide suspension resulted in a significant reductionof the dissolution rate at pH<10. Electrokinetic studiesindicated that the reduced dissolution rate may be related tothe formation of surface complexes; the experiments showed thatCo species in solution adsorb on the oxidised tungsten carbidepowder.

The surface forces of oxidised tungsten and cobalt surfaceswere investigated using the atomic force microscope (AFM)colloidal probe technique. The interactions at various ionicstrengths and pH values are well described by DLVO theory. Theadsorption of cobalt ions to tungsten oxide surfaces resultedin an additional non-DLVO force and a reduced absolute value ofthe surface potential. It was shown that the adsorption ofpoly(ethylene imine) (PEI) to the WO3 surfaces induces anelectrosteric repulsion.

The properties of spray-dried WC-Co granules were related tothe WC primary particle size, and the poly(ethylene glycol)(PEG) binder and PEI dispersant content in aqueous WC-Cosuspensions. The granule characterisation includes a new methodfor measuring the density of single granules. The increase inthe fracture strength of granules produced from suspensionsthat were stabilised with PEI was related to a more densepacking of the WC-Co particles.

The AFM was used to study the friction and adhesion ofsingle spray-dried WC-Co granules containing various amounts ofPEG binder. The adhesion and friction force between two singlegranules (intergranular friction) and between a granule and ahard metal substrate (die-wall friction) have been determinedas a function of relative humidity. The granule-wall frictionincreases with binder content and relative humidity, whereasthe granule-granule friction is essentially independent of therelative humidity and substantially lower than the granule-wallfriction at all PEG contents.

Key words:Hard Metal, Cemented Carbide, WC-Co, TungstenCarbide, Cobalt, Oxidation, Dissolution, Surface Complexation,XPS, AFM, Colloidal Probe, Hamaker Constant, Cauchy, WO3,CoOOH, ESCA, Zeta-Potential, Surface Potential, Poly(ethyleneimine), PEI, Suspension, van der Waals, Steric, Spray-Dried,Poly(ethylene glycol), Strength, Density, Friction, Adhesion,Granule, PEG, Pressing, FFM.

The aim of this thesis work was to gain understanding of the interactions between talc mineral and surfaces, liquids and chemicals relevant for industrial applications, such as pulp and paper. Talc is used in the pulp and paper industry as a filler pigment, in control of pitch (lipophilic extractives) deposits and as a coating pigment. A deeper understanding of talc interactions will be beneficial in optimizing its use. Long-range attractive interactions between talc and hydrophobic model probes, as well as pitch probes, have been measured using the atomic force microscope (AFM) colloidal probe method. Two procedures for preparation of pitch colloidal probes were developed to allow these studies. Model hydrophobic, nanorough surfaces with surface energy characteristics similar to talc have also been prepared and their interactions with hydrophobic model probes compared to interactions between hydrophobic model probes and talc. It is demonstrated that talc mineral interacts with model hydrophobic particles, as well as with pitch, by long-range attractive forces, considerably stronger than the expected van der Waals force. The possible origin of the measured interaction forces is discussed, and the conclusion is that the main cause is an attractive capillary force due to formation of a gas/vapor capillary between the surfaces. Force measurements using model hydrophobic, nanorough surfaces show that a large-scale waviness does not significantly influence the range and magnitude of the capillary attraction, but large local variations in these quantities are found. It is demonstrated that a large variation in adhesion force corresponds to a small variation in local contact angle of the capillaries at the surfaces. The nature of the surface topographical features influences the capillary attraction by affecting the local contact angle and by pinning of the three-phase contact line. The effect is clearly dependent on the size of the surface features and whether they exist in the form of crevices or as extending ridges. Entrapment of air also affects the imbibition of water in pressed talc tablets. The effects of wetting and dispersion agents on the interactions between talc and hydrophobic probes have also been investigated. It is demonstrated that a common dispersing agent used for talc, poly(acrylic acid), does not affect the capillary attraction between talc and non-polar probes. In fact, the results strongly suggest that poly(acrylic acid) does not adsorb on the basal plane of talc. From this finding it is inferred that the stabilizing effect of this additive most likely is due to adsorption to the edges of talc. In contrast, a wetting agent (the non-ionic triblock copolymer Pluronic PE6400) removes the long-range capillary attraction. It is suggested that such an ability to replace air at the talc surface is of great importance for an efficient wetting agent. The Hamaker constant for talc has also been estimated by using optical data obtained from spectroscopic ellipsometry. It is demonstrated that a nanocrystalline talc mineral, cut in different directions displays very small differences in Hamaker constant between the different crystallographic orientations, whereas a microcrystalline sample displays a significantly higher value. The estimated Hamaker constants are discussed for different material combinations of relevance for the pulp- and paper industry, such as cellulose and calcium carbonate.
Målet med detta avhandlingsarbete var att öka förståelsen för interaktioner mellan talkmineral och ytor, vätskor och kemikalier relevanta för industriella applikationer, såsom papper och massa. Talk används i pappers- och massaindustrin som fyllmedel, för kontroll av hartsrika (lipofila extraktivämnen) avsättningar och som bestrykningspigment. En djupare förståelse för talkinteraktioner kommer att vara användbart för att optimera dess användning. Långväga attraktiva interaktioner mellan talk och hydrofoba modellpartiklar, såväl som mellan talk och hartspartiklar, har uppmätts med hjälp av atomkraftsmikroskopi (AFM) genom att fästa kolloidala partiklar på kraftsensorn. Två metoder för att framställa partiklar gjorda av harts har utvecklats för att möjliggöra dessa studier. Hydrofoba, nanostrukturerade modellytor med ytenergier liknande de för talk har också tillverkats och deras växelverkan med hydrofoba modellpartiklar har jämförts med dem mellan talk och hydrofoba modellpartiklar. Studierna visar att talkmineral växelverkar med hydrofoba modellpartiklar, såväl som med harts, genom långväga attraktiva krafter som är betydligt starkare än den förväntade van der Waals kraften. Möjliga orsaker till de uppmätta växelverkanskrafterna diskuteras och slutsatsen blir att huvudorsaken är en attraktiv kapillärkraft som uppkommer genom att en gas-/ångkapillär bildas mellan ytorna. Kraftmätningar gjorda med hydrofoba nanostrukturerade modellytor visar att en storskalig vågighet inte nämnvärt påverkar storleken av kapillärattraktionen, men stora lokala variationer existerar. Det demonstreras att en stor variation i adhesionskraft motsvaras av en liten variation i lokal kontaktvinkel för kapillärerna på ytorna. Ytornas topografi påverkar kapillärattraktionen genom att påverka den lokala kontaktvinkeln samt genom att trefaskontaktlinjen inte kan röra sig fritt över ytan. Effekten är tydligt beroende av huruvida ytojämnheterna existerar i form av nedsänkningar eller upphöjningar. Instängd luft påverkar också pressade talktabletters uppsugningsförmåga av vatten. Vätnings- och dispergeringsmedels inverkan på växelverkan mellan talk och hydrofoba partiklar har undersökts. Resultaten visar att ett vanligt dispergeringsmedel för talk, polyakrylsyra, inte påverkar kapillärattraktionen. I själva verket tyder data på att polyakrylsyra inte adsorberas på talks basalplan. Utifrån dessa resultat dras slutsatsen att polyakrylsyra stabiliserar talkdispersioner genom att adsorbera på talkkanterna. Ett vanligt vätmedel (nonjonisk triblock sampolymer Pluronic PE6400) tar å andra sidan bort långväga kapillärattraktion. Detta antyder att egenskapen att ersätta luft på talkytan är av stor betydelse för effektiva vätmedel. Hamakerkonstanten för talk har uppskattats genom att utnyttja optiska data från ellipsometrimätningar. Det demonstreras att ett nanokristallint talkmineral kapat i olika riktningar uppvisar mycket små skillnader i Hamakerkonstant mellan de olika kristallografiska orienteringarna, medan ett mikrokristallint prov uppvisar ett betydligt högre värde. De beräknade Hamakerkonstanterna diskuteras för olika materialkombinationer relevanta för pappersindustrin, såsom cellulosa och kalciumkarbonat.
QC 20100813

Ce travail de thèse de doctorat propose et évalue différentes solutions pour caractériser, avec des outils optiques et électromagnétiques non intrusifs, les nanoparticules et agrégats observés dans différents systèmes physiques : suspensions colloïdales, aérosols et plasma poussiéreux. Deux types de modèles sont utilisés pour décrire la morphologie d'agrégats fractals (p. ex. : suies issues de la combustion) et agrégats compacts (qualifiés de « Buckyballs » et observés dans des aérosols produits par séchage de nano suspensions). Nous utilisons différentes théories et modèles électromagnétiques (T-Matrice et approximations du type dipôles discrets) pour calculer les diagrammes de diffusion (ou facteur de structure optique) de ces agrégats, de même que leurs spectres d'extinction sur une large gamme spectrale. Ceci, dans le but d'inverser différentes données expérimentales. Différents outils numériques originaux ont également été mis au point pour parvenir à une analyse morphologique quantitative de clichés obtenus par microscopie électronique. La validation expérimentale des outils théoriques et numériques développés au cours de ce travail est focalisée sur la spectrométrie d'extinction appliquée à des nano agrégats de silice, tungstène et silicium
This Ph.D. work provides and evaluates various solutions to characterize, with optical/electromagnetic methods nanoparticles and aggregates of nanoparticles found in suspensions, aerosols and dusty plasmas. Two main models are introduced to describe the morphology of particle aggregates with fractal-like (for particles in plasmas and combustion systems) and Buckyballs-like (aerosols, suspensions) shapes. In addition, the author proposes various solutions and methods (T-Matrix, Rayleigh type approximations) to calculate the scattering diagrams (optical structure factors) of fractal aggregates as well as algorithms to inverse extinction spectra. As a reference case for the performed analysis, several tools to describe the morphology of fractal aggregates from electron microscopy images have been also developed. The experimental validation carried out with the Light Extinction Spectrometry (LES) technique (for nano silica beads, tungsten, dusty plasma and silicon aggregates) clearly proves the validity of the algorithms developed as well as the potential of the LES technique

Un polyélectrolyte hydrophobe est un polymère portant des charges électriques lorsqu'il est en solution aqueuse et dont l'eau est un mauvais solvant pour le squelette. Cette thèse a pour objectif d'établir l'influence de la nature hydrophobe du squelette sur les propriétés physiques des polyélectrolytes. Pour cela, nous avons tout d'abord synthétisé une série de poly(styrène-\emph(co)-styrènesulfonate de sodium), appelés PSS, possédant des taux de charge $f$ variant entre 30\% et 100\% et comportant entre $N=120$ et $N=2520$ monomères par chaîne. Ces PSS sont caractérisés précisément et peuvent être considérés comme des polyélectrolytes hydrophobes modèles. Nous avons alors étudié leurs propriétés volumiques puis interfaciales.\\ \emph(1. Propriétés en volume.) Le taux de charge effectif de la chaîne unique est anormalement réduit par rapport au cas du polyélectrolyte hydrophile. D'autre part, les propriétés structurales ont été caractérisées par la diffusion des rayons X et la technique de la sonde colloïdale en microscopie à force atomique (AFM). La conformation des chaînes se fait ressentir puisque la longueur de corrélation varie comme $N^0C_p^(-\alpha)$ où $C_p$ est la concentration en polymère et $\alpha$ un exposant dépendant de $f$, décroissant de 1/2 ($f=100\%$) à 1/3 au voisinage de la limite de solubilité. Ces observations sont interprétées dans le cadre d'un modèle théorique prédisant la conformation de la chaîne isolée comme un collier de perles, constitué de globules denses (les perles) reliés deux à deux par un segment de chaîne étirée. La dynamique collective des chaînes, quant à elle, est très proche de celle des polyélectrolytes hydrophiles.\\ \emph(2. Propriétés aux interfaces.) Nous avons conçu une expérience permettant, par adsorption électrostatique ou hydrophobe, de fixer les chaînes de PSS sur une surface solide plane modifiée chimiquement. La couche de PSS adsorbée, immergée dans l'eau, est caractérisée $in~situ$ par ellipsométrie, réflectivité des rayons X haute énergie et microscopie à force atomique. Nous avons ainsi trouvé que la taille de perles varie entre 1 et 5 nm en fonction de $f$. Cette variation est en parfait accord avec les prédictions du modèle dit du collier de perles. Enfin, les polyélectrolytes hydrophobes s'adsorbent également aux interfaces hydrophobes, les perles, dans certains cas, s'étalant sur la surface.

The theory of Brownian motion is a cornerstone of modern physics. In this thesis, we introduce a nonequilibrium extension to this theory, namely an effective Markovian theory of the Brownian motion of a heated nanoparticle. This phenomenon belongs to the class of nonequilibrium steady states (NESS) and is characterized by spatially inhomogeneous temperature and viscosity fields extending in the solvent surrounding the nanoparticle. The first chapter provides a pedagogic introduction to the subject and a concise summary of our main results and summarizes their implications for future developments and innovative applications. The derivation of our main results is based on the theory of fluctuating hydrodynamics, which we introduce and extend to NESS conditions, in the second chapter. We derive the effective temperature and the effective friction coefficient for the generalized Langevin equation describing the Brownian motion of a heated nanoparticle. As major results, we find that these parameters obey a generalized Stokes–Einstein relation, and that, to first order in the temperature increment of the particle, the effective temperature is given in terms of a set of universal numbers. In chapters three and four, these basic results are made explicit for various realizations of hot Brownian motion. We show in detail, that different degrees of freedom are governed by distinct effective parameters, and we calculate these for the rotational and translational motion of heated nanobeads and nanorods. Whenever possible, analytic results are provided, and numerically accurate approximation methods are devised otherwise. To test and validate all our theoretical predictions, we present large-scale molecular dynamics simulations of a Lennard-Jones system, in chapter five. These implement a state-of-the-art GPU-powered parallel algorithm, contributed by D. Chakraborty. Further support for our theory comes from recent experimental observations of gold nanobeads and nanorods made in the the groups of F. Cichos and M. Orrit. We introduce the theoretical concept of PhoCS, an innovative technique which puts the selective heating of nanoscopic tracer particles to good use. We conclude in chapter six with some preliminary results about the self-phoretic motion of so-called Janus particles. These two-faced hybrids with a hotter and a cooler side perform a persistent random walk with the persistence only limited by their hot rotational Brownian motion. Such particles could act as versatile laser-controlled nanotransporters or nanomachines, to mention just the most obvious future nanotechnological applications of hot Brownian motion.

Biosensoren stellen technische Geräte dar, die im Zentrum ihres Wirkmechanismus ein Biomolekül, also ein Molekül mit einer biologischen Funktion, aufweisen. Eine Vielzahl von Biosensoren findet in der Wissenschaft bereits Verwendung. Viele dieser Sensoren werden an planen Grenzflächen mit hoher Steifigkeit angewandt, welche weit von der in vivo Situation entfernt sind. Hierdurch ist unklar, ob diese Vereinfachung von natürlichen Prozessen inkorrekte oder in der biologischen Funktionalität veränderte Ergebnisse liefert. Aus diesem Grund soll mit dieser Arbeit die Vielseitigkeit eines neuen Biosensorsystems aufgezeigt werden, mit dem physikalische Phänomene von biologischen Systemen mimetisch nachgestellt und untersucht werden können. Der auf Hydrogelmikropartikeln basierende Biosensor bewies hierbei seine Verwendbarkeit für die Quantifizierung von unspezifischen Adhäsionsvorgängen an Materialgrenzflächen, wie auch für spezifische Rezeptor-Ligand-Wechselwirkungen von lebenden Zellen. Weiterhin konnte mit zwei verschiedenen Nachweismethoden, einer auf Reflektionskontrastmikroskopie basierenden und einer kraftspektroskopischen Methode, die breitgefächerte Anwendung der Hydrogelmikropartikel für biophysikalische Fragestellungen aufgezeigt werden. Die multivalenten und biomimetischen Eigenschaften der Mikropartikel erlauben hierbei ein quantitatives Verständnis von Wechselwirkungsvorgängen von Biomolekülen mit Materialgrenzflächen und spezifischen Rezeptorstrukturen, wobei das Biosensorsystem selbst einfach und leicht zu kontrollieren bleibt.

The most commonly known macro scale probing devices are simply comprised of metallic leads used for measuring electrical signals. On the other hand, micromachined probing devices are realized using microfabrication techniques and are capable of providing very fine, micro/nano scale interaction with matter; along with a broad range of applications made possible by incorporating MEMS sensing and actuation techniques. Micromachined probes consist of a well-defined tip structure that determines the interaction space, and a transduction mechanism that could be used for sensing a change, imparting external stimuli or manipulating matter. Several micromachined probes intended for biological and nanotechnology applications were fabricated, characterized and tested. Probes were developed under two major categories. The first category consists of Micro Electromagnetic Probes for biological applications such as single cell, particle, droplet manipulation and neuron stimulation applications; whereas the second category targets novel Scanning Probe topologies suitable for direct nanopatterning, variable resolution scanning probe/dip-pen nanolithography, and biomechanics applications. The functionality and versatility of micromachined probes for a broad range of micro and nanotechnology applications is successfully demonstrated throughout the five different probes/applications that were studied. It is believed that, the unique advantages of precise positioning capability, confinement of interaction as determined by the probe tip geometry, and special sensor/actuator mechanisms incorporated through MEMS technologies will render micromachined probes as indispensable tools for microsystems and nanotechnology studies.

碩士
國立中正大學
化學工程研究所
91
The theorem of this research applies the surface plasmon resonance of gold nanoparticles. The absorbance spectrum varied with different dielectric constant of the environment. We use self-assembled monolayers to modify the immobilized gold nanoparticle surface on unclad fibers and probe the nickel ion, biochemicals and the immunoassay of antigen and antibody. The sensor scheme is achieved building a semiconductor laser system as the lightsource probing signal and make the reflection fiber to undertake the test of sucrose solution with different refractive indices. The results show that the signal will vary linearly under different refractive index and the length of unclad fiber affect the linearity. The organic functional group of modified gold nanoparticles will show selectivity and binds with nickel ion effectively. For detecting biochemicals such as streptavidin, the detection limit is 7.82*10-10M. The results of immunoassay for Human IgG and SEB will attain down to 0.1 ng/ml. In conclusion, the reflection fiber shows promising results for biosensor.

Adhesion between different objects is happening everywhere. Without it, simple procedures like walking or holding something in a hand or attaching a postage stamp would be impossible. The life itself depends on adhesion on all levels, starting from the interactions between the living cells. Adhesion between two substrates is a complex phenomenon, which at present is still not well understood. There are several factors determining the strength of adhesion: (i) molecular interactions at interface, (ii) mechanical properties of adhesive, and (iii) area of contact between adhesive and probing surface. Two surfaces are tacky when they possess the right balance between these factors. Controlling the adhesion of materials is important in many fields ranging from industrial purposes to biomedical applications and everyday usage. There is a demand for “smart” materials with integrated functionalities that make them responsive, switchable, biocompatible, anti-bacterial, more energy efficient, or autonomous. In particular, materials for such cutting-edge applications like cell culture, drug delivery, tissue engineering, biosensors, anti/biofouling, microfluidics, climbing robots, sport equipment and many others require adjustable/tuneable adhesive properties. Many efforts were directed towards fabrication of materials with either weak or strong adhesion depending on the field of application. However, design of “smart” surfaces with reversibly switchable/controllable adhesion is still a highly challenging task. Therefore, the thesis aims on design of smart polymeric materials with responsive / adaptive adhesion properties. For this, fabrication and investigation of two types of switchable polymer layers based on stimuli-responsive polymer brushes will be performed. The first group is dealing with thermoresponsive polymer brushes: poly-(N-isopropylacrylamide) and two types of biocompatible polyethylene glycol-based systems. These polymer layers undergo phase transition below and above LCST between hydrophilic and hydrophobic states. The second part of the work is related to solvent-responsive comb-like and block copolymer brushes consisted of hydrophilic PEG and hydrophobic PDMS biocompatible and biodegradable polymers.

The SCP-RICM assay employs the measurable surface energy (or adhesive work W_adh) of a micrometer-sized polymeric sphere (soft colloidal probe, SCP) interacting with a glass chip using reflection interfer-ence contrast microscopy (RICM). Depending on those two interacting surfaces' nature and functional-ization, the SCP will deform, creating a contact area with the hard glass chip. This contact area is clearly distinguishable from the sphere’s interference ring pattern and can be measured. The adhesive surface energy W_adh can be calculated from the size of the contact area. An immobilization can be overcome by choosing a two-component analyte-dependent interaction, here presented for the copper (Cu) detection. The detection of Cu was chosen as a proof-of-concept system. However, detecting metal ions is an essential endeavor because, in excessive amounts, they present a severe threat to health and the environment. The copper-dependent interaction of the yeast chaperones yCox17 (also Cox17) and ySco1 (also Sco1) were chosen as the two-component analyte-dependent interaction. The chaperones partic-ipate in vivo in the formation of the electron transport chain of S. cerevisiae and interact in the mito-chondrial inner membrane to transfer one Cu(I) ion from Cox17 to Sco1. It was necessary to immobilize one protein to the SCPs and one to the chip surface, to transfer the copper chaperones' interaction into the SCP-RICM assay core detection components. The unique self-assembling characteristics of the class I hydrophobin Ccg-2 from N. crassa were used to immobilize one interaction partner to the chip surface. Class I hydrophobins are known for the formation of re-sistant and uniform layers at hydrophilic/hydrophobic interfaces. Initial SCP-RICM assay measurements with Sco1Δ95_a-SCPs and the Cox17_c-chips indicate that copper detection using the proposed mechanism is possible (Figure 39-3). Measurements can be differentiated between 0 and 0.1 mM Cu(I) concentration in solution. Further screening of concentrations be-low 0.1 mM is still necessary. The presented proof-of-principle system for the indirect detection of copper shows copper-dependent behavior. These positive results give rise to many more options to use the SCP-RICM assay as an indirect detection system. The application range of the SCP-RICM assay could be enlarged for different analytes such as other heavy metals, bacteriophages, biomarkers, et cetera, and is relevant for fields from medicine to environmental monitoring.:TABLE OF CONTENT Table of Content I List of Figures VII List of Tables IX List of Abbreviations XI 1 Introduction 1 1.1 Biosensors 1 1.2 Analytical Detection Methods: Copper 2 1.3 SCP-RICM Assay 3 1.3.1 Sensor Chip Surface 4 1.3.2 Soft Colloidal Probes 5 1.3.3 Reflection Interference Contrast Microscopy 6 1.4 Hydrophobins 9 1.4.1 Structure and Functions of Hydrophobins 9 1.4.2 Ex vivo Applications of Hydrophobins 11 1.4.3 Class I Hydrophobin: Ccg-2 12 1.5 Mitochondrial Respiratory Chain 14 1.5.1 Copper Transport in Yeast 14 1.5.2 S. cerevisiae Sco1 protein 18 1.5.3 S. cerevisiae Cox17 protein 21 1.6 SCP-RICM Assay for Copper Detection 23 1.7 Aim of the Study 24 2 Materials and Methods 25 2.1 Laboratory Equipment 25 2.1.1 Devices 25 2.1.2 Chemicals 26 2.1.3 Consumables 28 2.1.4 Antibodies 29 2.1.5 Enzymes 30 2.1.6 Molecular Weight Standards 30 2.1.7 DNA Oligonucleotides 31 2.1.8 Plasmids and Vectors 32 2.2 Microorganisms 33 2.2.1 Strains 33 2.2.2 Cultivation of Microorganisms 34 2.2.3 Preparation of Electrocompetent E. coli Cells 36 2.2.4 Preparation of E. coli Glycerol Stocks 36 2.3 Protein Design 37 2.4 Molecular Cloning Methods 38 2.4.1 Vector Template Preparation 38 2.4.2 Agarose Gel Electrophoresis 40 2.4.3 DNA Extraction from Agarose Gels 41 2.4.4 Polymerase Chain Reaction 41 2.4.5 DNA Restriction Digest 42 2.4.6 DNA Dialysis 43 2.4.7 Ligation of DNA Fragments 43 2.4.8 Isolation of DNA from E. coli 44 2.4.9 DNA Sequencing 45 2.4.10 Transformation of E. coli via Electroporation 45 2.5 Protein Detection and Quantification 46 2.5.1 SDS PAGE 46 2.5.2 Coomassie Staining 50 2.5.3 Western Blot Analysis 51 2.5.4 Immunological Detection 51 2.5.5 Protein Quantification: Lowry Assay 52 2.5.6 Protein Quantification: Bradford Assay 53 2.5.7 Protein Quantification: NanoDrop Measurement 53 2.6 Protein Purification and Storage 54 2.6.1 Expression Analysis of Recombinant Proteins 54 2.6.2 Solubility Analysis 54 2.6.3 Protein Purification by Ni2+ Affinity Chromatography 55 2.6.4 Quantification of Purified Proteins 64 2.6.5 Dialysis of Purified Proteins 65 2.7 Glass Surface Functionalization 65 2.7.1 Glass Surface Preparation 66 2.7.2 Hydrophobin and Fusion Protein-Based Coating 66 2.7.3 Contact Angle Measurement 67 2.7.4 DRoPS Test 67 2.7.5 Atomic Force Microscopy 67 2.8 SCP Functionalization 68 2.8.1 Functionalization of SCPs with Proteins 68 2.8.2 Validation of SCP Functionalization with FITC Staining 69 2.9 SCP-RICM Assay and Its Analysis 69 3 Results 73 3.1 Generation of Recombinant Fusion Proteins 73 3.1.1 Sco1 and Sco1∆95 73 3.1.2 Cox17 84 3.1.3 Ccg-2 88 3.1.4 Overview: Optimization of Expression and Purification of Recombinant Proteins 90 3.2 His-Tag Cleavage 92 3.3 Chip Surface Functionalization 94 3.3.1 Optimization of the Glass Chip Preparation 94 3.3.2 Macroscopic Properties of the Functionalized Chip Surface 95 3.3.3 AFM Measurements 102 3.3.4 Theoretical Package of Hydrophobin Ccg-2 on the Chip Surface 103 3.4 SCP Functionalization 104 3.4.1 SCP Functionalization and FITC Staining 104 3.4.2 Theoretical Package of Proteins on SCPs 106 3.5 SCP-RICM Assay 107 4 Discussion and Further Prospectives 113 4.1 Discussion: SCP-RICM Assay and Protein-Protein Interaction 113 4.2 Outlook and Further Prospects 119 4.2.1 Heterologous Protein Expression and Purification: Methods, Cleavage and Refolding 119 4.2.2 Further Analysis of Chip Surface Functionalization 124 4.2.3 Alternative Chip Surface Functionalization Methods 126 4.2.4 SCP-RICM Assay: Data Acquisition and Evaluation 128 4.2.5 SCP-RICM Assay: Copper Detection 130 4.2.6 Exploiting the SCP-RICM Assay using Protein-Protein Interactions 131 4.2.7 Exploiting the SCP-RICM Assay with Alternative Interactions 133 5 Summary 137 6 Bibliography 141 7 Appendix 165 7.1 Sequences of Protein Constructs 165 7.1.1 Sequences of the Protein Construct Cox17_a 165 7.1.2 Sequences of the Hydrophobin-Cox17 Fusion Protein Cox17_b 165 7.1.3 Sequences of the Hydrophobin-Cox17 Fusion Protein Construct Cox17_c 166 7.1.4 Sequences of the Protein Construct Sco1_a and Sco1Δ95_a 167 7.1.5 Sequences of the Hydrophobin-Sco1 Fusion Protein Constructs Sco1_b and Sco1Δ95_b 169 7.1.6 Sequences of the Hydrophobin-Sco1 Fusion Protein Constructs Sco1_c and Sco1Δ95_c 171 7.1.7 Sequences of the Hydrophobin Ccg-2 173 7.2 pET-28b(+): Plasmid Map 173 7.3 Nickel Removal During Dialysis 175 7.4 DGR Assay 176 7.5 SCP diameter 179 Acknowledgements 181 Declaration of Authorship 183

The theory of Brownian motion is a cornerstone of modern physics. In this thesis, we introduce a nonequilibrium extension to this theory, namely an effective Markovian theory of the Brownian motion of a heated nanoparticle. This phenomenon belongs to the class of nonequilibrium steady states (NESS) and is characterized by spatially inhomogeneous temperature and viscosity fields extending in the solvent surrounding the nanoparticle. The first chapter provides a pedagogic introduction to the subject and a concise summary of our main results and summarizes their implications for future developments and innovative applications. The derivation of our main results is based on the theory of fluctuating hydrodynamics, which we introduce and extend to NESS conditions, in the second chapter. We derive the effective temperature and the effective friction coefficient for the generalized Langevin equation describing the Brownian motion of a heated nanoparticle. As major results, we find that these parameters obey a generalized Stokes–Einstein relation, and that, to first order in the temperature increment of the particle, the effective temperature is given in terms of a set of universal numbers. In chapters three and four, these basic results are made explicit for various realizations of hot Brownian motion. We show in detail, that different degrees of freedom are governed by distinct effective parameters, and we calculate these for the rotational and translational motion of heated nanobeads and nanorods. Whenever possible, analytic results are provided, and numerically accurate approximation methods are devised otherwise. To test and validate all our theoretical predictions, we present large-scale molecular dynamics simulations of a Lennard-Jones system, in chapter five. These implement a state-of-the-art GPU-powered parallel algorithm, contributed by D. Chakraborty. Further support for our theory comes from recent experimental observations of gold nanobeads and nanorods made in the the groups of F. Cichos and M. Orrit. We introduce the theoretical concept of PhoCS, an innovative technique which puts the selective heating of nanoscopic tracer particles to good use. We conclude in chapter six with some preliminary results about the self-phoretic motion of so-called Janus particles. These two-faced hybrids with a hotter and a cooler side perform a persistent random walk with the persistence only limited by their hot rotational Brownian motion. Such particles could act as versatile laser-controlled nanotransporters or nanomachines, to mention just the most obvious future nanotechnological applications of hot Brownian motion.:1 Introduction and Overview 2 Theory of Hot Brownian Motion 3 Various Realizations of Hot Brownian Motion 4 Toy Model and Numerical Methods 5 From Experiments and Simulations to Applications 6 Conclusion and Outlook