Ligament and tendon injuries remain a persistent clinical challenge, accounting for up to 45% of the 32 million musculoskeletal injuries reported in the U.S. each year. However, current soft tissue repair and reconstruction techniques are limited by insufficient integration with subchondral bone, potentially leading to graft failure and suboptimal functional outcomes. Therefore, there is a pressing clinical need for functional solutions that can enable integrative soft tissue reconstruction via regeneration of the fibrocartilaginous insertion present at the junction between bone and major ligaments and tendons. This fibrocartilaginous enthesis consists of compositionally distinct but structurally continuous tissue regions (non-calcified and calcified fibrocartilage), and it plays a critical role in mediating complex load transfer between soft tissue and bone while minimizing the formation of stress concentrations at the insertion. Given the functional significance of the insertion site and using the anterior cruciate ligament (ACL) as a model tissue, the objective of this thesis is identify and optimize tissue engineering strategies for regeneration of the fibrocartilaginous interface. Thus, the studies detailed in this thesis consist of elucidation of key interface characteristics that can inform interface scaffold design, identification of an optimal cell source, and optimization of chemical and physical stimuli for fibrocartilage formation. To guide biomimetic scaffold design, this thesis began with quantitative mapping of the compositional and structural properties of the native ligament-to-bone interface. As both the aligned collagen matrix structure and distinctive mineral distribution pattern across the insertion were shown to be highly conserved over time, an ideal scaffold for fibrocartilage interface regeneration should therefore consist of aligned fibers and must be able to support the formation of both non-mineralized and mineralized fibrocartilage tissues. Additionally, evaluation of ex vivo behavior of insertion fibrochondrocytes cultured on aligned nanofiber scaffolds indicated that an ideal system for fibrocartilage regeneration should also support cell-mediated deposition of both types I and II collagen as well as proteoglycans. Comparison of potential cell sources for fibrocartilage tissue engineering showed that synovium-derived mesenchymal stem cells (SDSCs) exhibited higher proliferative and fibrochondrogenic differentiation potential compared to bone marrow-derived mesenchymal stem cells. Thus, subsequent studies focused on optimization of culture parameters for SDSC-mediated fibrocartilage formation. Nanofiber scaffolds that provided controlled release of transforming growth factor (TGF)-β3, which is known to play a critical role in development of the insertion as well as in scarless healing, were developed to guide SDSC differentiation. Scaffold-mediated TGF-β3 delivery enhanced cell proliferation and matrix synthesis in a dose-dependent manner, resulting in synthesis of fibrocartilaginous matrix consisting of both type I and II collagen as well as proteoglycans. As mechanical loading is known to also play a critical role in insertion development, a custom bioreactor that mimics the complex loads sustained at the interface was also developed. It was shown that the bioreactor simultaneously generated both tensile and compressive stresses and modulated SDSC matrix synthesis, where deposition of fibrocartilaginous matrix was observed on mechanically loaded scaffolds without any additional chemical co-stimulation. Finally, as a functional scaffold for integrative ACL repair must support the establishment of both non-mineralized and mineralized tissue regions, the combined effects of TGF-β3 and hydroxyapatite (HA) on MSC-mediated formation of mineralized fibrocartilage were also explored. The addition of HA nanoparticles to the scaffold was shown to enhance cell proliferation and matrix synthesis and represents a promising strategy for formation of mineralized fibrocartilage. Collectively, these observations delineate the importance of bioinspired chemical and physical stimuli in fibrochondrogenic differentiation, and how they can be optimized for stem cell-mediated interface regeneration. These studies yield valuable scaffold design criteria and establish in vitro culture parameters that can be applied to functional integration of soft connective tissue with bone at various critical attachments throughout the musculoskeletal system, including the ligament and tendon-to-bone entheses, as well as for regeneration of other important fibrocartilaginous tissues.

populärwissenschaftlicher Abstract:<br /> Kristallisation, Biomimetik und halbleitende Polymere in räumlich begrenzten Systemen:<br /> Öl und Wasser mischen sich nicht, man kann aber aus beiden Flüssigkeiten Emulsionen herstellen, bei denen Tröpfchen der einen Flüssigkeit in der anderen Flüssigkeit vorliegen. Das heißt, es können entweder Öltröpfchen in Wasser oder Wassertröpfchen in Öl erzeugt werden. Aus täglichen Erfahrungen, z.B. beim Kochen weiß man jedoch, dass sich eine Emulsion durch Schütteln oder Rühren herstellen lässt, diese jedoch nicht besonders stabil ist. Mit Hilfe von hohen Scherenergien kann man nun sehr kleine, in ihrer Größe sehr einheitliche und außerdem sehr stabile Tröpfchen von 1/10000 mm erhalten. Eine solche Emulsion wird Miniemulsion genannt. <br /> In der Dissertation wurden nun z.B. Miniemulsionen untersucht, die aus kleinen Wassertröpfchen in einem Öl bestehen. Es konnte gezeigt werden, dass das Wasser in diesen Tröpfchen, also in den räumlich begrenzten Systemen, nicht bei 0 &#176;C, sondern bei -22 &#176;C kristallisierte. Wie lässt sich das erklären? Wenn man einen Eimer Wasser hat, dann bildet sich normalerweise bei 0 &#176;C Eis, da nämlich in dem Wasser einige (manchmal ganz wenige) Keime (z.B. Schutzteilchen, ein Fussel etc.) vorhanden sind, an denen sich die ersten Kristalle bilden. Wenn sich dann einmal ein Kristall gebildet hat, kann das Wasser im gesamten Eimer schnell zu Eis werden. Ultrareines Wasser würde bei -22 &#176;C kristallisieren. Wenn man jetzt die Menge Wasser aus dem Eimer in kleine Tröpfchen bringt, dann hat man eine sehr, sehr große Zahl, nämlich 1017 Tröpfchen, in einem Liter Emulsion vorliegen. Die wenigen Schmutzpartikel verteilen auf sehr wenige Tröpfchen, die anderen Tröpfchen sind ultrarein. Daher kristallisieren sie erst bei -22 &#176;C.<br /> <br /> Im Rahmen der Arbeit konnte auch gezeigt werden, dass die Miniemulsionen genutzt werden können, um kleine Gelatine-Partikel, also Nanogummibärchen, herzustellen. Diese Nanogummibärchen quellen bei Erhöhung der Temperatur auf ca. 38 &#176;C an. Das kann ausgenutzt werden, um zum Beispiel Medikamente zunächst in den Partikeln im menschlichen Körper zu transportieren, die Medikamente werden dann an einer gewünschten Stelle freigelassen. In der Arbeit wurde auch gezeigt, dass die Gelatine-Partikel genutzt werden können, um die Natur nachzuahnen (Biomimetik). Innerhalb der Partikel kann nämlich gezielt Knochenmaterial aufgebaut werden kann. Die Gelatine-Knochen-Partikel können dazu genutzt werden, um schwer heilende oder komplizierte Knochenbrüche zu beheben. Gelatine wird nämlich nach einigen Tagen abgebaut, das Knochenmaterial kann in den Knochen eingebaut werden.<br /> <br /> LEDs werden heute bereits vielfältig verwendet. LEDs bestehen aus Halbleitern, wie z.B. Silizium. Neuerdings werden dazu auch halbleitende Polymere eingesetzt. Das große Problem bei diesen Materialien ist, dass sie aus Lösungsmitteln aufgebracht werden. Im Rahmen der Doktorarbeit wurde gezeigt, dass der Prozess der Miniemulsionen genutzt werden kann, um umweltfreundlich diese LEDs herzustellen. Man stellt dazu nun wässrige Dispersionen mit den Polymerpartikeln her. Damit hat man nicht nur das Lösungsmittel vermieden, das hat nun noch einen weiteren Vorteil: man kann nämlich diese Dispersion auf sehr einfache Art verdrucken, im einfachsten Fall verwendet man einfach einen handelsüblichen Tintenstrahldrucker. / The colloidal systems are present everywhere in many varieties such as emulsions (liquid droplets dispersed in liquid), aerosols (liquid dispersed in gas), foam (gas in liquid), etc. Among several new methods for the preparation of colloids, the so-called miniemulsion technique has been shown to be one of the most promising. Miniemulsions are defined as stable emulsions consisting of droplets with a size of 50-500 nm by shearing a system containing oil, water, a surfactant, and a highly water insoluble compound, the so-called hydrophobe<br /> <br /> 1. In the first part of this work, dynamic crystallization and melting experiments are described which were performed in small, stable and narrowly distributed nanodroplets (confined systems) of miniemulsions. Both regular and inverse systems were examined, characterizing, first, the crystallization of hexadecane, secondly, the crystallization of ice. It was shown for both cases that the temperature of crystallization in such droplets is significantly decreased (or the required undercooling is increased) as compared to the bulk material. This was attributed to a very effective suppression of heterogeneous nucleation. It was also found that the required undercooling depends on the nanodroplet size: with decreasing droplet size the undercooling increases.<br /> <br /> 2. It is shown that the temperature of crystallization of other n-alkanes in nanodroplets is also significantly decreased as compared to the bulk material due to a very effective suppression of heterogeneous nucleation. A very different behavior was detected between odd and even alkanes. In even alkanes, the confinement in small droplets changes the crystal structure from a triclinic (as seen in bulk) to an orthorhombic structure, which is attributed to finite size effects inside the droplets. An intermediate metastable rotator phase is of less relevance for the miniemulsion droplets than in the bulk. For odd alkanes, only a strong temperature shift compared to the bulk system is observed, but no structure change. A triclinic structure is formed both in bulk and in miniemulsion droplets.<br /> <br /> 3. In the next part of the thesis it is shown how miniemulsions could be successfully applied in the development of materials with potential application in pharmaceutical and medical fields. The production of cross-linked gelatin nanoparticles is feasible. Starting from an inverse miniemulsion, the softness of the particles can be controlled by varying the initial concentration, amount of cross-link agent, time of cross-linking, among other parameters. Such particles show a thermo-reversible effect, e.g. the particles swell in water above 37 &#176;C and shrink below this temperature. Above 37 &#176;C the chains loose the physical cross-linking, however the particles do not loose their integrity, because of the chemical cross-linking. Those particles have potential use as drug carriers, since gelatin is a natural polymer derived from collagen.<br /> <br /> 4. The cross-linked gelatin nanoparticles have been used for the biomineralization of hydroxyapatite (HAP), a biomineral, which is the major constituent of our bones. The biomineralization of HAP crystals within the gelatin nanoparticles results in a hybrid material, which has potential use as a bone repair material.<br /> <br /> 5. In the last part of this work we have shown that layers of conjugated semiconducting polymers can be deposited from aqueous dispersion prepared by the miniemulsion process. Dispersions of particles of different conjugated semiconducting polymers such as a ladder-type poly(para-phenylene) and several soluble derivatives of polyfluorene could be prepared with well-controlled particle sizes ranging between 70 - 250 nm. Layers of polymer blends were prepared with controlled lateral dimensions of phase separation on sub-micrometer scales, utilizing either a mixture of single component nanoparticles or nanoparticles containing two polymers. From the results of energy transfer it is demonstrated that blending two polymers in the same particle leads to a higher efficiency due to the better contact between the polymers. Such an effect is of great interest for the fabrication of opto-electronic devices such as light emitting diodes with nanometer size emitting points and solar cells comprising of blends of electron donating and electron accepting polymers.

No description available.

Biologically-inspired materials have emerged as promising substrates for enhanced repair in various therapeutic and regenerative medicine applications, including nervous and vascular tissues, bone, and cartilage. These strategies focus on the development of materials that integrate well-characterized domains from biomacromolecules to mimic individual functions of the extracellular matrix (ECM), including cell adhesive motifs, growth factor binding sites, and protease sensitivity. A vital property of the ECM is the fibrillar architecture arising from supramolecular assembly. For example, the fibrillar structure of fibronectin (FN) matrices modulates cell cycle progression, migration, gene expression, cell differentiation, and the assembly of other matrix proteins. Current biomaterials do not actively promote deposition and assembly of ECM. In this research, we describe the rational design and investigation of non-fouling biomimetic surfaces in which an oligopeptide sequence (FN13) from the self-assembly domain of FN is tethered to non-fouling substrates. This surface modification directs cell-mediated co-assembly of robust fibrillar FN and type I collagen (COL) matrices reminiscent of ECM, and increases in cell proliferation rates. Furthermore, the effect of this peptide is surface-directed, as addition of the soluble peptide has no effect on matrix assembly. We have also identified a critical surface density of the immobilized peptide to elicit the full activity. These results contribute to the development and design of biomimetic surface modifications that direct cell function for biomedical and biotechnology applications.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 163-191).

Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Tsukruk, Vladimir; Committee Member: Shofner, Meisha; Committee Member: Srinivasarao, Mohan; Committee Member: Thio, Yonathan; Committee Member: Weissburg, Marc. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Bioinspired design uses biological systems to inspire engineering designs. One of bioinspired design’s challenges is identifying relevant information sources in biology for an engineering design task. Currently information can be retrieved by searching biology texts or journals using biology-focused keywords that map to engineering functions. However, this search technique can overwhelm designers with unusable results. This work explores the use of text classification tools to identify relevant biology passages for design. Further, this research examines the effects of using biology passages as stimuli during idea generation. Four human-subjects studies are examined in this work. Two surveys are performed in which participants evaluate sentences from a biology corpus and indicate whether each sentence prompts an idea for solving a specific design problem. The surveys are used to develop and evaluate text classification tools. Two idea generation studies are performed in which participants generate and record solutions for designing a corn shucker using either different sets of biology passages as design stimuli, or no stimuli. Based 286 sentences from the surveys, a k Nearest Neighbor classifier is developed that is able to identify helpful sentences relating to the function “separate” with a precision of 0.62 and recall of 0.48. This classifier could potentially double the number of helpful results found using a keyword search. The developed classifier is specific to the function “separate” and performs poorly when used for another function. Classifiers developed using all sentences and participant responses from the surveys are not able to reliably identify helpful sentences. From the idea generation studies, we determine that using any biology passages as design stimuli increases the quantity and variety of participant solutions. Solution quantity and variety are also significantly increased when biology passages are presented one at a time instead of all at once. Quality and variety are not significantly affected by the presence of design stimuli. Biological stimuli are also found to lead designers to types of solution that are not typically produced otherwise. This work develops a means for designers to find more useful information when searching biology and demonstrates several ways that biology passages can improve ideation.

No description available.

Kaskadinė fermentinė reakcija yra tokia cheminių reakcijų grandinė, kai vienos fermentinės reakcijos produktas yra panaudojamas kitose fermentinėse reakcijose tol, kol gaunamas galutinis rezultatas. Tokių reakcijų pavyzdžiai gamtoje yra kraujo krešėjimo reakcija, celiulozės skaidymas bei signalų perdavimas neuronuose. Norint, kad kaskadinė fermentinė reakcija vyktų efektyviai, fermentai, reikalingi reakcijai vykti, turi būti išsidėstę taip, kad po kiekvieno reakcijos etapo tarpinis produktas efektyviai pasiektų kitą reakcijai reikalingą fermentą. Tokių reakcijų efektyvumą galima bandyti pagerinti sutelkiant visus reikalingus reakcijai fermentus šalia vienas kito. Vienas iš variantų kaip būtų galima sukurti daugiafermentį kompleksą yra panaudojant segmentuotus metalinius nanostrypelius kaip koduojančią matricą bei genetiškai modifikuotas fermentų molekules. Prie fermentų molekulių būtų prijungiamos dideli giminiškumą reikalingam nanostrypelio metaliniam segmentui turinčios oligopeptidinės uodegėlės, kurios sukurtų sąlygas fermentams savaime organizuotis ant segmentuoto nanostrypelio paviršiaus. Magistrinio darbo užduotys buvo charakterizuoti susintetintus nanostrypelius, patikrinti ar modifikuotas giminiškomis sidabrui peptidinėmis uodegėlėmis streptavidinas sugeba prisijungti biotiną bei palyginti modifikuoto ir ir nemodifikuoto streptavidino giminiškumą sidabro paviršiui. Atlikus eksperimentus buvo nustatyta, kad naudojantis atominės jėgos mikroskopija nepavyko patikimai... [toliau žr. visą tekstą] / Biochemical enzyme cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. If one could organize all the necessary enzymes for the reaction in close quarters this could possibly lead to more effective cascade reactions. One way of organizing enzymes is by fusing them on barcoded nanowire matrices. This could be achieved by tayloring enzyme molecules with genetically engineered proteins for inorganics (GEPIs). My assignment was to characterise possible nanowire candidates for these biohybrid complexes using AFM and examine silver binding characteristics of GEPI taylored streptavidin using SERS. I could not realiably characterise nanowires because the interaction between AFM probe and nanowires was to interfering. Also the nanowires used to aggregate and it was difficult to separate them using ultrasound. 15nm diameter nanowires aggregated more thant 30nm diameter nanowires. Streptavidin taylored with Ag binding GEPIs showed stronger interaction with Ag electrode surface than ordinary streptavidin. Also this modified streptavidin was capable of binding with biotin. This proves that added oligopeptide chains did not negatively affect the chemical structure of streptavidin.

Animals effectively move and negotiate a variety of environments exemplifying the neuromuscular system's ability to produce complex coordinated movements. Our central thesis is that the nonlinear dynamical properties of muscle play a critical role in power production and stability during such movements. We have developed a closed-loop system that couples an isolated muscle to a physical or computational load, facilitating the study of the interactions between intrinsic muscle properties and external forces. We used this system to determine how elastic elements in the frog semimembranosus can improve power production during a jumping task and how the contractile element automatically manages energy to maintain a stable bouncing gait. Our results reveal that, during ballistic movements (e.g. jumping), series elastic elements stretch and shorten to temporally concentrate energy transfer from the contractile element to the body, amplifying power production. We measured peak instantaneous power greater than twice the maximum power the contractile element could produce alone. Our results show how, during a bouncing gait, the contractile and elastic elements autonomously interact to produce, dissipate, and recycle energy and to maintain dynamic stability without sensory feedback. Our data suggest that muscles can recover over 75% of the kinematic energy from one step and apply it to the next. These results demonstrate the effects and importance of intrinsic muscle properties during movements. Ultimately, this research can guide the development of biomimetic robotic and prosthetic technologies capable of life-like mobility.