Die Benetzbarkeit und Nichtbenetzbarkeit von Oberflächen durch eine Flüssigkeit sind faszinierende und wichtige Phänomene in Wissenschaft und Technologie. Jüngst wurde entdeckt, dass Partikel die Benetzung einer Wasseroberfläche durch ein Öl unterstützen können. Es wurde eine Theorie entwickelt, das Prinzip der zu beschreiben. In der vorliegenden Doktorarbeit wurde diese Theorie im Experiment sowohl qualitativ als auch quantitativ untersucht, wobei zwei Arten von Kieselgelpartikeln Verwendung fanden. Mit Hilfe einer Reihe unregelmäßig geformter Partikel mit variierender Hydrophobie wurde der Einfluss der Oberflächenhydrophobie der Partikel auf die partikel-assistierte Benetzung untersucht. Es wurde herausgefunden, dass die Partikel mit höchster Hydrophilie Linsen aus reinem Öl bilden, während die Partikel in die Wasserphase abtauchen. Die Partikel mit größter Hydrophobie hingegen bewirken die Ausbildung von kleinen Bereichen, in denen Öl und Partikel eine stabile homogene Schicht formen. Für Partikel mit mittlerer Hydrophobie wurden beide Phänomene beobachtet. Diese drei verschiedenen Beobachtungen bestätigen, dass die Oberflächenhydrophobie der Partikel das Benetzungsverhalten des Öls auf der Wasseroberfläche bestimmen. Für die unregelmäßig geformten Partikel war aufgrund des unbekannten Kontaktwinkels ein direkter Vergleich zur Theorie nicht möglich. Um die Theorie quantitativ zu prüfen, wurden sphärische Partikel synthetisiert und ihre Oberflächen mit Hilfe von zehn Silanisierungsmittel modifiziert. Anschließend wurde ein Vergleich der experimentellen Ergebnisse mit dem entsprechenden theoretischen Phasendiagramm durchgeführt. Die Untersuchungen zeigten, dass die theoretischen Vorhersagen zum Großteil mit den experimentellen Ergebnissen übereinstimmen. Es wurden alle Fälle der Benetzung beobachtet, die auch in der theoretischen Beschreibung berücksichtigt wurden. Darüber hinaus wurden auch Abweichungen von der Theorie festgestellt. Haben die Partikel ähnliche Affinitäten zur Luft/Öl- und Öl/Wasser-Grenzfläche, hängt die Beschaffenheit der Benetzungsfilme zusätzlich vom Oberflächendruck ab. Deshalb könnte es notwendig sein, die einfache Theorie zu erweitern um den beschriebenen Beobachtungen Rechnung zu tragen. / Wetting and de-wetting of surfaces by a liquid are fascinating and important phenomena in science and technology. Recently, it was discovered that particles can assist the wetting of a water surface by an oil, and a theory describing the principle behind particle assisted wetting was developed. In this thesis, the theory was experimentally investigated qualitatively and quantitatively by using two series of silica particles. The influence of the surface hydrophobicity of the particles on particle assisted wetting was investigated by a series of irregular shaped particles with varying hydrophobicity. By applying mixtures of particles and oil to a water surface, it was found that for the most hydrophilic particles, only lenses of pure oil formed, with the particles being submerged into the aqueous phase. The most hydrophobic particles helped to form patches of stable homogenous mixed layers composed of oil and particles. For particles with intermediate hydrophobicity, lenses and patches of mixed layers were observed. These three different observations verified that the hydrophobicity of the particle surface determines the wetting behaviour of the oil at the water surface. For the irregular shaped particles with unknown contact angles with liquid interfaces, no direct comparison to the theory was possible. To test the theory quantitatively, a series of spherical particles was synthesized and their surfaces were modified by ten kinds of silane coupling agents; then the experimental results were compared with the corresponding theoretical phase diagram. It indicated that the theory agrees at large with the experimental results. All scenarios of wetting layers taken into account in the theoretical description were observed. In the fine print, deviations from the theory were also observed. If the particles have similar affinities to air/oil and oil/water interfaces, the experimentally observed morphology of the wetting layers depends in addition on the surface pressure. It might therefore be necessary to extend the simple theoretical picture to take these observations into accounts.

<p>The role of mechanical forces in the fate and function of adherent cells has been revealed to be a pivotal factor in understanding cell biology. Cells require certain physical cues to be present in their microenvironment or the cell will begin apoptosis. Mechanical signals from the environment are interpreted at the cellular level and biochemical responses are made due to the information from outside the cell, this process is known as mechanotransduction. Misinterpretation of physical cues has been indicated in many disease states, including heart disease and asthma. When a cell is bound to the ECM, proteins such as integrins are engaged at static and stable adhesion sites. These tight and static anchoring points found at the ECM exist in stark contrast to the dynamic conditions seen at intercellular junctions. Intercellular junctions, such as gap and adherens junctions, are formed between cells to act as a mechanism to relay information and exchange material. Due to the important role intercellular junctions play in processes of wound healing, epithelial-mesenchymal transition and cancer metastasis developing more sophisticated levels of understanding of these mechanisms would provide valuable insight.</p> <p>Complex biological processes, including immune cell signaling and cellular ECM adhesions, have been effectively replicated in model systems. These model systems have included the use of solid supported lipid bilayers and polymeric hydrogels that display cell adhesion molecules. Studies of cellular mechanotransduction at ECM adhesion sites has also been completed with covalently functionalized polymeric substrates of adjustable elasticity. However, developing model systems that allow the accurate reproduction of properties seen at intercellular junctions, while also allowing the investigation of cellular mechanosensitivity has proven to be a difficult task. Previous work has shown that polymer-tethered lipid bilayers (PTLBs) are a viable material to allow the replication of the dynamics and adhesion seen at intercellular junctions. Although efforts have been made to produce PTLBs with different mechanical properties, there is currently not a material with sufficient tunable elastic properties for the study of cellular mechanotransduction.</p> <p>To establish a system that allows the study of stiffness effects across a biologically relevant range (~0.50 – 40 kPa) while maintaining the dynamic properties seen at cell-to-cell junctions, polymer gel-tethered bilayers (PGTBs) were developed. A fabrication strategy was established to allow the incorporation of a hydrogel support with easily tunable stiffness and a tethered lipid bilayer coating, which produced a powerful platform to study the effects of stiffness at intercellular junctions. Careful attention was given to maintain the beneficial properties of membrane diffusion, and it was shown that on different linking architectures lipid bilayers could be established and diffusion was preserved. Microscopy-based FCS and FRAP methodology were utilized to measure lipid diffusion in these systems, while confocal microscopy was used to analyze cell spreading and adhesion. Three distinct architectures to link the lipid membrane to the underlying polyacrylamide hydrogel were pursued in this work, a non-covalent biotin-streptavidin system, a covalently linked design with fibronectin, and a direct covalent linkage utilizing crosslinker chemistry. In this work, it was shown that cells were able to spread and adhere on these substrates, with cell adhesion zones visualized under plated cells that demonstrate the capability of the cell to rearrange the presented linkers, while maintaining a stable material. Also confirmed is the tunability of the polymer hydrogel across a wide range of stiffness, this was shown by quantitative changes in cell spreading area in response to polymer properties.</p>

Emulsion polymerizations of vinyl acetate (VAc) were performed by fully or partially replacing poly(vinyl alcohol) (PVA) with renewable materials as protective colloids or by adding renewable materials, as additives or fillers, to the emulsions during or after polymerization. The purpose of the study was to increase the amount of renewable materials in the emulsion. A total of 19 emulsions were synthesized. Different recipes were used for the synthesis. The following renewable materials were studied; hydroxyethyl cellulose (HEC) with different molecular weights, starch and proteins. HEC and starch were used as protective colloids. Proteins were used as additives or fillers. Cross-linking agent A and Cross-linking agent B were used as cross-linking agents. A total of 26 formulations were pressed, either cold or hot. The synthesized emulsions were evaluated with respect to pH, solids content, viscosity, minimum film formation temperature (MFFT), glass transition temperature (Tg), particle size and molecular weight (Mw). The tensile shear strengths of the emulsions were evaluated according to EN 204 and WATT 91. It was possible to fully, or partially, replace PVA as protective colloid with renewable materials. It was also possible to use renewable materials as additives or fillers in the emulsions. The emulsions obtained properties that differed from the reference. Generally, emulsions with HEC as protective colloid showed lower viscosity and slightly higher MFFT, Tg and molecular weight than emulsions with PVA as protective colloid. Larger particle sizes than the reference were obtained for emulsions containing PVA combined with renewable materials. The emulsion with starch as protective colloid exhibited the largest particle size. 10 formulations passed the criteria for D2. The emulsions where PVA was fully or partially replaced with HEC or starch showed a water resistance similar to the reference (around D2). The addition of protein did not decrease the water and heat resistance compared to the reference. Addition of protein after polymerization increased the water resistance (D2) compared to addition during polymerization. Addition of cross-linking agents did not increase the water resistance further. Two formulations passed the criteria for D3. The emulsion in the first formulation had PVA as protective colloid and protein B was added during polymerization. The emulsion in the second formulation had HEC as protective colloid. To both of these emulsions, protein A was added after polymerization, as a filler, combined with Cross-linking agent B as cross-linking agent before hot pressing. The first formulation also showed a good heat resistance (passed the criteria for WATT 91).

<p>Microfluidics has established itself as a key technology in a wide range of fields including pharmaceuticals, point-of-care diagnostics, thermal management, and space technology. Most of these applications involve manipulation of small quantities (micro – nanoliters) of fluids and various particles or biological cells suspended in them. These platforms employ mechanical, thermal, acoustic, magnetic, optical, electric and many other means for creating particle and fluid motion. Many biological applications require handling cells that are vulnerable to getting damaged if proper physiological conditions are not maintained or if excessive force is applied on them. The non-invasive nature of optical and electrical micro-manipulation techniques such as rapid electrokinetic patterning (REP) has proven to be of great importance in such applications. These techniques enable handling, transportation, sorting and arrangement of fragile synthetic micro/nanoparticles and biological cells without compromising their structure and surface properties.</p> <p>REP is a recently developed micro-manipulation tool that employs optically induced electrothermal vortices to create custom flow patterns. Particle suspensions are entrained in these vortices and are trapped on an electrode surface through AC electrokinetic mechanisms. This work focuses on characterizing a REP trap and discusses its potential applications in handling biological cells. Polystyrene microparticles are confined in a REP trap and a MATLAB program is used to track their motion inside the trap. The tracked particle trajectory reveals that the potential energy of the trapped particle is parabolic and hence the trap is Hookean in nature. The trap is modelled as a spring-mass system and the stiffness coefficient of that system is found to be of the order of 10^-15 N/μm. The origin of the restoring force in the spring-mass model is found to be the drag force created by the electrothermal vortex. The ability to exert ultra-small forces in a stable trap enables REP to be used in various non-invasive particle manipulation applications.</p> <p>The transient nature of REP is studied using numerical modeling and particle image velocimetry (PIV) analysis of a vortex created by a moving laser spot. A numerical model suggests that custom-shaped steady state REP vortices can be created via superposition of multiple axisymmetric circular shaped vortices. However, the method of superposition cannot be extended to transient traps and a more involved 3D model is required to simulate them. The laser spot is scanned back-and-forth in a line with different speeds to create transient REP vortices. The PIV analysis, in agreement with the numerical model, shows that the location of the moving vortex is undiscernible at high speeds. Moreover, the circular shaped vortex is stretched out into a line when the laser scanning frequencies are more than 15 Hz.</p> <p>The particle-electrode attraction force, which entraps the particles at the electrode surface, is characterized using particle diffusometry (PD) and defocusing particle tracking. PD is used to measure the diffusion coefficient of polystyrene particles under different electric field parameters near an electrode surface. It is found that the particle diffusivity decreases with a decrease in the electric field frequency from 150 – 30 kHz and with an increase in the applied voltage from 4 – 8 V_pp. A MATLAB program is used to track the number of in-focus particles and their distance from the electrode surface. A histogram of the particles’ distance from the electrode surface shows an increase in the particle concentration near the electrode at low frequencies (30 – 60 kHz). These observations suggest that the average height of an entrapped particle decreases with a decrease in applied field frequency and an increase in applied voltage. This suggests that the attractive trapping force is significant at 30 kHz but diminishes at around 150 kHz.</p> <p>Salt and sugar-based isotonic media used for cell suspensions pose several challenges for electrokinetic mechanisms such as REP. Various solutions to overcome these challenges for bio-manipulation applications are discussed in this work. The presence of DC offset in the AC electric field is found to enhance particle entrapment in sugar-based media. The effect of DC offset on trapping performance in bio-relevant media is assessed by measuring the stability of the REP trap. This work also shows entrapment and manipulation of Mice pancreatic cancer cells (KPC2) suspended in the sugar-based isotonic media using REP. The biological applications of the REP technology are highly promising, but they have not yet been well-explored. This work lays the foundation of understanding how REP can be operated in high osmolarity media for bio-manipulation applications.</p>

<p>  </p> <p>A staggering number of problems in materials chemistry relate to controlling the assembly of matter at <10 nm scales, including those with applications in nanoelectronics, energy harvesting, and biomedical device design. It is difficult to achieve precise chemical patterning at the short length scales required for such applications using traditional top-down fabrication methods (<em>e.g., </em>lithographic techniques). On the other hand, biological systems create high-resolution chemical patterns with remarkable efficiency, by assembling simple molecular building blocks with nm-scale features (<em>e.g.,</em> nucleotides, amino acids, lipids) into structurally complex motifs capable of carrying out the diverse functions required for life. </p> <p>Drawing inspiration from the diverse structures and functions of lipids in biological membranes, this work uses lipids to create high-resolution chemical patterns at interfaces, control the growth and self-assembly of nanocrystals, and to facilitate interactions that precisely template nanocrystals at chemically patterned surfaces.</p> <p>Functional alkanes assemble into striped phase monolayers on highly oriented pyrolytic graphite (HOPG), in which the alkyl chains are oriented parallel to the substrate, expressing both the polar and nonpolar regions of the amphiphile at the environmental interface. The same is true for diyne phosphoethanolamine (dPE), a phospholipid with a zwitterionic headgroup. When assembled into striped phases on HOPG, the headgroup zwitterions of dPE are confined in 1-nm-wide rows of functional groups with a pitch of ~7 nm, resulting in ordered arrays of orientable dipoles at the HOPG surface. The chemistry of dimensionally confined functional groups is distinct from bulk solution phase chemistry, and in this case enables powerful directing effects which can be used to template the adsorption of ultranarrow gold nanowires (AuNWs) in precise alignment with the template stripes. </p> <p>Technical grade oleylamine (<em>cis</em>-9-octadecen-1-amine, OLAm, 70% purity) serves as the capping ligand for the AuNWs used in this work, and additionally plays an important role in the assembly of AuNWs at dPE/HOPG surfaces. While technical-grade reagents enable cost-effective and scalable production of materials, variation in the composition of impurities between different batches have significant impacts on nanocrystal morphology and assembly. We show that thermal transitions of alkyl chain impurities (<em>trans</em> and saturated chains) in AuNW ligand shells can be used to regulate AuNW assembly at chemically patterned interfaces. </p> <p>Characterization of OLAm reagents by 1H NMR and mass spectrometry reveals significant and highly variable fractions elaidylamine (ELAm, <em>trans</em>-9-octadecen-1-amine) and octadecylamine (ODAm) between different batches of OLAm. To understand the phase behavior of mixtures of the C18 alkylamines commonly found in technical grade OLAm, we synthesize isomerically pure OLAm and its <em>trans</em> isomer, elaidylamine (ELAm), to generate binary and ternary mixtures with (ODAm), which is commercially available in high purity. Differential scanning calorimetry reveals limited miscibility of the C18 chains, and demonstrates the significant impact of chain composition on the physical properties of mixtures of alkyl chains (<em>e.g.,</em> tech. grade OLAm). Finally, we examine the impacts of <em>trans</em> and saturated alkyl chains on AuNW synthesis. We find that inclusion of ODAm and ELAm in the ligand blend used for AuNW synthesis each result in shorter AuNWs than those synthesized with pure OLAm. We also observe enhanced stability of surface adsorbed AuNWs conferred by <em>trans </em>and saturated chains. </p>

<p>  </p> <p>As monoclonal antibodies (mAbs) become a more important part of the pharmaceutical industry, the need for better quicker analysis of then will also increase. To do this, better stationary phases specifically designed for mAbs need to be developed to analyze the quality of mAbs by their critical control attributes. The three main critical control attributes are size, charge, and glycosylation. This work focuses mainly on the development of stationary phases to analyze critical control attributes in size and charge through using a non-porous silica base and surface confined atom transfer radical polymerization to grow improved stationary phases that minimize undesired interactions and maximize desired interactions.</p>

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18306号 / 工博第3898号 / 新制||工||1598(附属図書館) / 31164 / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 山本 量一, 教授 松坂 修二, 教授 古賀 毅 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Colloidal dispersions such as oil-in-water or water-in-oil emulsions have found widespread use in the food industry. Oil-in-water emulsions consist of three principal components i.e. oil dispersed in the form of droplets, water surrounding the droplets as the continuous phase, and emulsifiers comprising the interface. Because of the complicated interaction among components, it is often difficult to predict the physicochemical properties and final functionalities of emulsions. Nevertheless, the structural and functional features of emulsions allow scientists to create many unique emulsions that may serve as suitable carriers for lipophilic functional compounds. These functional compounds may include antioxidants, flavors, colors and antimicrobials, the latter which is the principal topic of this thesis. Incorporation of food antimicrobials in emulsions could create value-added emulsions that may improve the safety and quality of a variety of foods, but to date, few systematic studies on their formulation have been reported. The objective of this thesis was therefore to formulate food emulsions that are physicochemically stable and able to deliver antimicrobial compounds to microbial target sites. Two antimicrobial agents, N-α-lauroyl-L-arginine ethyl ester monohydrochloride, (LAE) and eugenol were used as model compound to be incorporated into the colloidal food dispersion. The two antimicrobials were selected because they are either amphiphilic (LAE) or predominantly lipophilic (eugenol). When emulsions were formulated with eugenol, an essential oil component, it was found that O/W emulsions were only stable when emulsions were formulated with other lipids (hexadecane, dodecane, tetradecane, and corn oil). Above a critical loading of the carrier lipid with eugenol, Ostwald’s ripening led to rapid destabilization while above this critical loading concentration, the ripening rate was greatly reduced and depended on type of carrier lipid and concentration of eugenol. Alternatively, when emulsions were formulated with LAE as emulsifier, results indicated that emulsions were not stable to aggregation and coalescence. Consequently, LAE had to be combined with a nonionic surfactant (Tween 20) to improve the emulsion stability. Higher Tween20 composition led to more stable emulsions droplets. Both systems (emulsions with either eugenol or LAE) had high antimicrobial efficacies and were able to completely inhibit microbial growth at concentrations that depended on the type of microorganisms and formulation of the emulsions. Generally, eugenol were able to more effectively inhibit the growth of E.coli O157:H7 while LAE containing emulsions were more effective against L.monocytogenes. Finally, a food emulsion was formulated that contained both antimicrobial agents; eugenol in the lipid phase and LAE in the droplet interface. Interestingly, stability of these emulsions depended both on the LAE and eugenol loading. The antimicrobial activity in this double antimicrobial emulsion was high but was principally influenced by the interfacial formulation that is the ratio of LAE to Tween 20. The combined emulsion similar to the LAE stabilized emulsion more effectively inhibited growth of L.monocytogenes.