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As a self-assembled mimetic structure of biological membranes, polydiacetylene liposomes have been studied for the development of platforms for various applications including nano-containers, nano-transporters, and nano-delivery systems for biological-, life- and materials-science applications. Liposomes incorporating amphiphilic polymer poly(10, 12 pentacosadiynoic acid) (PDA) was used as a building block for investigations mimicking cellular reaction and processes at the membrane cell. Changes in local membrane micro-organization and packing as a result of biomolecular and bioparticle reactions and processes at the liposomal membrane were investigated through the use of colorimetric and emission responses of PDA liposomes in solution phase. My dissertation comprises of six chapters. I provide brief overview of each chapter in the following paragraphs: Chapter 1: Introduction. In this chapter, an introduction is given on structure and function of lipid bilayer and multilayer of liposomes from a perspective of shared features with biological membranes. Amphiphilic molecules along with natural lipids at (or higher) critical micelle concentration self-assemble in aqueous medium, thereby, forming a lipid bilayer or multilayer to reduce the free energy of the system. When one of the components of the lipid bilayer is a polymerizable monomer, micelles/liposomes with enhanced mechanical and chemical stability are achieved. The lipid bilayer of liposomes is a boundary that includes at least three different regions: inside aqueous cavity, hydrophobic membrane zone, and membrane-aqueous interfaces. The membrane surface is available for further functionalization. In general, all three regions of the liposomes are utilized for both fundamental and applied studies. For example, the PDA liposomes have been employed for biosensing, drug/protein/nucleic acid transport and delivery and target release, and various probing cellular-like reactions and processes at the membranes. Here, in this chapter, literature on PDA was reviewed for a time period of 2008-2015. Furthermore, emphasis was given to application of PDA liposomes as (bio) sensing elements utilizing colorimetric, fluorescence, and FRET mechanisms. Chapter 2. Polydiacetylene (PDA) liposomes have been accepted as attractive colorimetric bionanosensors. The molecular recognition elements, either embedded within the liposomal membrane or covalent bound at the membrane surface, are available for interaction with biological and chemical analytes. Usually, PDA liposomes perform transduction activity through perturbation of the conjugated polymer backbone, which provides a colorimetric change in solution or solid-state phase. Here, we report that trapping self-quenched fluorescent specie within inner cavity of the liposomes is a simple and effective analytical tool for evaluating biomolecular binding events at the membrane surface. The release of fluorophores in response to the membrane binding event led to amplified emission signal which was utilized for probing reactions at the membrane surface that mimics reactions occurring at the cellular membrane surface. Specifically, a covalent binding on enzyme-substrate reaction resulted in a change of membrane fluidity, thereby releasing inner fluorophore content of the PDA liposomes. Fluorescent markers were loaded at or higher self-quenched concentration in the cavity of the liposome. Amplification of the fluorescence intensity was positively correlated with the concentration of protein added in the solution. The bilayer fluidity alteration also appears to depend on the molecular weight of the protein bound at the membrane. Overall, binding of protein with membrane promoted changes in the local PDA membrane organization and packing that enhanced the membrane permeability. The encapsulated content therefore leaked through “transient pores” formed in the membrane yielding substantial emission amplification. Chapter 3. Inspired by stability of the PDA liposomes, surface functionalization with a variety of molecules and loading within bilayer and inner cavity of the liposomes, we utilized liposomes as biocatalytical nanoreactors. Removable template molecules were embedded in the lipid bilayer and active protein encapsulated in the internal cavity was used for studying the transport properties of liposomes through substrate-enzyme reactions. Detergent Triton X-100 was used to remove a small portion of lipid and template molecules embedded in the membrane. The removal of lipid/template molecules not only affected the membrane fluidity but also provided transient pores in the membrane, allowing transport of substrate for enzymatic oxidation of glucose and 2-deoxy-glucose. Three important biological-relevant properties of cellular membrane: transport, bioavailability, and bio-reactivity of enzyme and substrate were studied. We found that enzyme molecules retained their reactivity when encapsulated within the aqueous inner cavity of the PDA liposomes, and that their activity was comparable to that in the bulk solution. Chapter 4. This chapter introduces studies on (at least partially) answering important questions how and if anchored enzyme activity at the liposome surface is affected through limited diffusion and spatial constraints. A further crucial question was investigated what effect of protein binding at the surface of the liposomes to enzymatic activity was. These relevant questions were important for increasing our fundamental knowledge related to reactions, interactions, and transport processes in biological cellular systems. A functionalized liposome system containing enzyme (Trypsin) covalently attached at the PDA liposome surface was synthesized. Using PDA liposomes as an immobilization scaffold, we evaluated and compared the cleavage behaviors of Trypsin in either immobilized at the membrane surface or in the free form. The covalent binding interaction and tryptic cleavage at the membrane-water interface was monitored by UV-vis and fluorescent spectroscopy, fluorescent anisotropy and spectro-micro-imaging. Trypsin binding at the membrane appeared to be significantly affected the enzymatic activity of the bound enzyme as seen from colorimetric response of the PDA liposomes. Chapter 5. Hierarchical structures support structures with new functionalities, therefore, advances in fabrication and characterization of biomimetic systems based on biological building blocks may present substantial potential rewards in material science. We take advantage of non-covalent forces known in biology for creating spatial organization by assembly tobacco mosaic virus-liposome polymeric hierarchical systems through biotin-streptavidin linkages. The advantage of using the biological thin rods such as TMV is that it can span the whole liposomal membrane allowing us to create microscopic hinge structures that connected liposomes. Our findings through electron and fluorescence microscopy confirmed that SA-TMV motif was able to stay inserted within the lipid bilayer of liposomes which yielded hierarchical structures after binding with Bt-liposomes. These hierarchical structures may find potential applications in targeted load (drug/protein/DNA) delivery, investigations involving virus-cell interactions, and sensing of virus particles. Chapter 6. Conclusions and Future work The present work in this dissertation utilized exploitation of biological self-assembly of small lipid molecules and larger biological-like motifs for enhancing our understanding of reactions and processes occurring at the cellular membrane surface. Overall the following four major studies were accomplished; 1. Sensing through amplified delivery, 2. Triggering an encapsulated bioreactor system at nanometric size, 3. Holding active biological elements when liposomes perform an attachment matrix, 4. Formation of hierarchical structures promoted by self-assembling of biological motifs with mimickers of cell membrane From our findings by mimicking the lipid bilayer of cell structures through liposomal membrane future work holds different ways to contribute in enhancing fundamental understanding of biological behavior. Active transport is an important function of all natural cells, playing important roles in intercellular communication. Liposomes composed of natural and polymerizable lipids may allow investigation involving exocytosis, formation of filopodia, vesicle fusion, budding and reproduction of neural synapses. Our liposome system may also mediate a broader range of highly selective and sensitive detection and sensing of cellular reactions and processes in physiological condition. I hope that this work in collaboration with multiple PIs will contribute to the fields at the interface of biology and material science.

Characterization and applications of soft tissue mimicking materials are presented. A skin mimicking material and a skin mimicking gel is characterized for industrial, scientific, and medical (ISM) band (2.40 GHz-2.48 GHz). Also a wide band (0.3 GHz – 2.5 GHz) muscle mimicking material is developed. A dual band implantable antenna operating at medical implant communication service (MICS) band (402 MHz – 405 MHz) and ISM band is tested in vitro with skin mimicking material for ISM band. MICS band measurements of the implantable antenna tested in vitro by placing the antenna on the interface of muscle and skin mimicking gel. An on-body antenna operating at ISM Band is designed for wireless cardiac monitoring applications. The mutual coupling between the antennas is minimized by placing antennas with 90 degree phase difference. The recipes for tissue mimicking materials and results such as, comparison of electrical properties, return loss, and mutual coupling measurements is given.

"Ultrasound phantoms that mimic injury are training devices that can emulate pre- and post-injury conditions within specific regions of human anatomy. They have the potential to be useful tools for teaching medical personnel how to recognize trauma conditions based on ultrasound images. This is particularly important because the increased use of portable ultrasound systems allows earlier diagnosis of internal trauma at locations such as traffic accidents, earthquakes, battlefields and terrorist attacks. A physical injury mimicking ultrasound phantom of the peritoneal cavity was constructed that mimicked the ultrasonic appearance of internal bleeding. Bleeding was simulated by injecting 600 mL of fluid of varying densities into the bulk of the phantom and comparing the ultrasonic appearance to before bleeding was simulated. The physical phantom was used to investigate whether or not the density of the injected fluid had any influence on the increase of inter-organ fluid volumes. The physical phantom was imaged in 3D with a 4.5 MHz phased array transducer, and two fluid volumes were segmented using the segmentation software ITK-SNAP. The 3D image representation of the phantom showed a difference qualitatively and quantitatively between pre-injury and post-injury conditions. Qualitatively, the physical model was analyzed. These specific criteria were analyzed within each image: 1) the number of individual organs that are present, 2) the number of other organs that each individual organ touches, 3) the appearance of fluid between the organs and the scanning membrane and 4) the merging of two separate fluid pockets. Using a Wilcoxon Rank-Sum test, a statistically significant difference was shown to exist between pre-injury and post-injury ultrasound images with a 95% level of confidence. Quantitatively, a Chi-Squared test was used to show that the volume of fluid between adjacent organs, calculated by ITK-SNAP, had no dependence on the density of the injected fluid. Furthermore, using a one-tailed T-test, there was at least a 99.9% confidence that the inter-organ volume estimations for the pre-injury and post-injury configurations were statistically different. As a final means of evaluation, the experimental phantom was taken to Harvard Medical School in November 2006 and analyzed by ultrasonographers. The doctors were very excited about its potential uses and found other interesting characteristics that the phantom was not designed for. In addition to modeling the appearance of an injected fluid volume, visualization of fluid flowing into the phantom, modeling the appearance of air in the inter-peritoneal space and simulating a surgical tool or bandage being accidentally left inside the patient could be modeled as well. The injury mimicking phantom was also modeled numerically, using ADINA finite element software. Using the same external dimensions as the experimental model, the numerical model showed that for physiologically unrealistic, very high fluid injection densities, the displacement of the organs had no statistical dependence on the density of the injected fluid, using an acceptance criterion of: P-value < 0.05. This was confirmed using an F-test of the average organ phantom tip displacement tabulated at several different times during simulation. The P-value obtained for analyzing the average tip displacement was 0.0506. However, a plot of the mass ratio, an expression of how the injected fluid has dispersed into the bulk of the phantom, showed that an unrealistically high fluid injection density had a different mass ratio profile than the other fluid injection densities that were simulated. This F-test revealed a strong indication, P-value = 0.0069, that the very high density caused a different fluid dispersion pattern. The numerical phantom offered a distinct advantage over the experimental model in that the dispersion of the injected fluid could be modeled numerically but not observed experimentally. Modeling the phantom numerically had some disadvantages. The numerical model had to have a large gap between adjacent organs. This had to occur because the contact algorithm within ADINA is incapable of modeling dynamic contact when fluid-structure interactions are modeled. This led to a volume fraction representation of the solid domain that was too low compared with the experimental model and what is found anatomically. For future iterations of the injury mimicking phantom, the numerical model will be used to help design the physical phantoms."

Shear wave (SW) imaging is an ultrasound elastogrpahy technique for estimating the elastic properties of biological tissues. Increasing the frequency would improve both the confinement of the radiation force generating the shear wave, and the imaging spatial resolution. The objectives of the study were to realize a simple high frequency (HF) system for the generation and detection of SW propagation and to implement this system to develop and characterize tissue-mimicking gelatin phantoms (TMGP) for HF SWI with elastic properties in the range of those encountered in biological tissue. A 5 MHz and 10 MHz focused transducer were used to induced SW’s in TMGP ranging from 4% to 12% gelatin with 3% silica for scattering and a 25 MHz single-element focused transducer recorded pulse-echo signals in order to capture the SW. The shear wave speeds in the TMGP were found to range linearly from 1.59-4.59 m/s in the 4% to 12% gelatin samples.

Shear wave (SW) imaging is an ultrasound elastogrpahy technique for estimating the elastic properties of biological tissues. Increasing the frequency would improve both the confinement of the radiation force generating the shear wave, and the imaging spatial resolution. The objectives of the study were to realize a simple high frequency (HF) system for the generation and detection of SW propagation and to implement this system to develop and characterize tissue-mimicking gelatin phantoms (TMGP) for HF SWI with elastic properties in the range of those encountered in biological tissue. A 5 MHz and 10 MHz focused transducer were used to induced SW’s in TMGP ranging from 4% to 12% gelatin with 3% silica for scattering and a 25 MHz single-element focused transducer recorded pulse-echo signals in order to capture the SW. The shear wave speeds in the TMGP were found to range linearly from 1.59-4.59 m/s in the 4% to 12% gelatin samples.

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Novel tissue mimicking materials have been developed for cancer treatment research. In the present research work, the tissue mimicking material is printed using 3D bioprinting technology. The nanoparticles are homogeneously mixed with tissue mimicking materials to enhance the heating capacity. The thermal conductivity of tissue mimicking materials is measured using a micropipette thermal sensor (MTS). Further, the optimal value is identified based on optimization technique and incorporated into a theoretical model to predict the surface temperature of microsphere. The heat conduction governing equation with Lambert law is numerically solved using COMSOL Multiphysics software. To validate the present simulation results, the experiments are conducted using a continuous laser system.

Polyamides are versatile polymers and includes naturally occurring macromolecules such as proteins as well as purely synthetic materials such as Nylon-3 and Nylon-6 polymers. While there are different ways to prepare polyamides, polyamide synthesis using anionic ring opening polymerization of lactams is the most widely used technique, due to the ease in preparation, excellent control in molecular weight and availability of wide variety of monomers. Our group reported the preparation of carbohydrate-based polyamides called poly-amido-saccharides (PASs) using anionic ring opening polymerization of sugar b-lactam monomers. The PASs reported so far includes glucose, galactose, altrose and maltose PASs, and functional PASs with n-octyl, carboxylate and amine functionalities. Sulfated or block poly-amido-saccharides on the other hand are unknown. In this thesis, I describe the synthesis of sulfated and block poly-amidosaccharides as well as evaluation of their biomedical applications. Naturally occurring sulfated polysaccharides play important roles in anticoagulation, lubrication of cartilage, and in developmental processes. New glucose-based non-regioselectively and regioselectively sulfated poly-amido-saccharides are prepared by the polymerization of protected glucose b-lactams, followed by post-polymerization modification reactions. All polymers are water soluble, non-cytotoxic, and adopt helical conformations. I evaluated the anticoagulant activity of the sulfated polymers using in vitro, ex vivo, and in vivo methods as well as determined the mechanism of anticoagulation by amidolytic activity inhibition assays. Additionally, I synthesized new block copolymers as block copolymers are used for various applications including latex paints and pressure sensitive adhesives. Specifically, carbohydrate-based amphiphilic polymers are of interest for drug delivery applications, due to favorable properties such as cytocompatibility, low immunogenicity, and longer circulation time. We prepared PAS-based amphiphilic block polymers with varied polymer length, hydrophobic to hydrophilic ratio, and stereochemistry of hydrophilic component. I characterized these amphiphilic polymers by NMR, IR, GPC, DSC, TGA and CD, and they self-assemble in water to form nanostructures as determined by DLS, SEM, and cryo-TEM, and are non-cytotoxic. / 2024-11-16T00:00:00Z

Fighting videogames (also known as fighting games) are ever growing in popularity and accessibility. The isolated console experiences of 20th century gaming has been replaced by online gaming services that allow gamers to play from almost anywhere in the world with one another. This gives rise to competitive gaming on a global scale enabling them to experience fresh play styles and challenges by playing someone new. Fighting games can typically be played either as a single player experience, or against another human player, whether it is via a network or a traditional multiplayer experience. However, there are two issues with these approaches. First, the single player offering in many fighting games is regarded as being simplistic in design, making the moves by the computer predictable. Secondly, while playing against other human players can be more varied and challenging, this may not always be achievable due to the logistics involved in setting up such a bout. Game Artificial Intelligence could provide a solution to both of these issues, allowing a human player s strategy to be learned and then mimicked by the AI fighter. In this thesis, game AI techniques have been researched to provide a means of mimicking human player strategies in strategic fighting games with multiple parameters. Various techniques and their current usages are surveyed, informing the design of two separate solutions to this problem. The first solution relies solely on leveraging k nearest neighbour classification to identify which move should be executed based on the in-game parameters, resulting in decisions being made at the operational level and being fed from the bottom-up to the strategic level. The second solution utilises a number of existing Artificial Intelligence techniques, including data driven finite state machines, hierarchical clustering and k nearest neighbour classification, in an architecture that makes decisions at the strategic level and feeds them from the top-down to the operational level, resulting in the execution of moves. This design is underpinned by a novel algorithm to aid the mimicking process, which is used to identify patterns and strategies within data collated during bouts between two human players. Both solutions are evaluated quantitatively and qualitatively. A conclusion summarising the findings, as well as future work, is provided. The conclusions highlight the fact that both solutions are proficient in mimicking human strategies, but each has its own strengths depending on the type of strategy played out by the human. More structured, methodical strategies are better mimicked by the data driven finite state machine hybrid architecture, whereas the k nearest neighbour approach is better suited to tactical approaches, or even random button bashing that does not always conform to a pre-defined strategy.