Glycopolymer Polyelectrolyte Multilayers Based on Maltose-Modified Hyperbranched Poly(ethyleneimine) For Future Drug Delivery Coatings and Biomedical Applications

Establishing highly sophisticated polymer films for delivery systems in a biological environment and bioanalytical tasks, the formation, thickness, swelling behavior, and (physiological) stability of highly biocompatible polyelectrolyte multilayers (PEMs) are described. These PEMs are composed of the very weak polycation maltose-modified hyperbranched poly(ethyleneimine) (PEI-Mal), strongly polyanion heparin sodium salt (HE − Na +) or weakly charged polyanion hyaluronic acid sodium salt (HA-Na+) deposited on Si wafer substrates. Two different glyco architectures for PEI-Mal are used, characterized by two different degrees of maltose decoration on a PEI scaffold. Using three pH-dependent deposition approaches for optimizing the (physiological) PEM stability and swelling, PEMs are characterized by (in situ) ellipsometry, atomic force microscopy (AFM), and (in situ) attenuated total reflection-Fouriertransform infrared (ATR-FTIR). Thus, PEMs reveal significantly different thicknesses, growth mechanisms (linear versus exponential), and swelling behavior in dependence of both the polycation architectures and the deposition protocol. These PEMs will allow the study of their complexation and release properties as preswollen PEMs against anionic drug molecules, adenosine triphosphate sodium salt (ATP), especially under physiological conditions for future drug delivery coatings

Turbo-slice-and-patch: an algorithm for metropolitan scale VBR video streaming.

Kong Chun Wai.Thesis submitted in: July 2003.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 53-54).Abstracts in English and Chinese.Contentsacknowledgement --- p.IAbstract --- p.II摘要 --- p.IIIChapter Chapter 1 --- Introduction --- p.1Chapter Chapter 2 --- Related Works --- p.4Chapter 2.1 --- Previous Work --- p.4Chapter 2.2 --- Comparison --- p.5Chapter Chapter 3 --- System Architecture --- p.7Chapter 3.1 --- Transmission Scheduling --- p.7Chapter 3.2 --- Admission Control --- p.9Chapter 3.3 --- Challenges in Supporting VBR-encoded Video --- p.10Chapter Chapter 4 --- Priority Scheduling --- p.12Chapter 4.1 --- Static Channel Priority (SCP) --- p.13Chapter 4.2 --- Dynamic Channel Priority (DCP) --- p.16Chapter Chapter 5 --- Turbo-Slice-and-Patch --- p.19Chapter 5.1 --- Video Pre-processing --- p.19Chapter 5.2 --- Bandwidth Allocation --- p.22Chapter 5.3 --- Three-Phase Patching --- p.23Chapter 5.4 --- Client Buffer Requirement --- p.27Chapter Chapter 6 --- Playback Continuity --- p.30Chapter Chapter 7 --- Performance Evaluation --- p.39Chapter 7.1 --- Average Latency --- p.40Chapter 7.2 --- Client Buffer Requirement --- p.43Chapter 7.3 --- Choice of Parameter Rcut --- p.44Chapter 7.4 --- Latency versus Arrival Rate --- p.46Chapter 7.5 --- Server Bandwidth Comparison --- p.48Chapter 7.6 --- Bandwidth Partitioning --- p.50Chapter Chapter 8 --- Conclusions --- p.52Bibliography --- p.5

MULTIPHASE MICROFLUIDIC FABRICATION OF POLYMERIC MICRO-CONTAINERS FOR BIO-ENCAPSULATION

Ph.DDOCTOR OF PHILOSOPH

Surface Modification of Ti Implant for Enhancing Biotribology and Cells Attachment

Implant success strongly depends on the proper integration of bone to biomaterial surface. By the selected retrieval cases, inadequate integration of bone screws was a dominated factor caused failure. The surface modification technology that improve osteointegration by inducing TiO2 nanotubes (NT) on Ti-based implants has a potential applications in orthopaedic implants. NT generated by anodization method provide a vertically aligned nanotube structure that enhances the integration between bone tissue and implant surface by improving osteoblasts attachment. Although cells to NT is positive, the mechanical weakness of NT has also been well-documented and is an obstacle to its applications. The thesis comprise a detailed method to improve NT mechanical stability, by introducing an interfacial bonding layer at NT bottom and Ti substrate, and retaining vertically aligned nanotubes. The physicochemical properties of this structure optimized TiO2 nanotubes (SO-NT) was systematically characterized, the SO-NT has been demonstrated with improved biotribological and biocorrosive performance. The uniform hyperfine interfacial bonding layer with nano-sized grains exhibited a strong bonding to NT layer and Ti substrate. It was observed, the layer not only effectively dissipates external impacts and shear stress but also acts as a good corrosion resistance barrier to prevent the Ti substrate from corrosion. The SO-NT modified bone screw has also demonstrated with enhanced fretting corrosion resistance than NT and pristine Ti6Al4V on screws. Since the elongated osteoblasts were observed on NT and SO-NT compared with Ti surface, the nanotubes structure has been shown with promoting of osteoblasts attachment. However, the mechanism of cell nanotubes interactions are largely in controversial. In order to reveal the cell-nanomaterial interactions, nanotopographies including Nanoconvex, Nanoconcave and Nanoflat were generated and characterized to evaluate the cell initial attachment behaviour. Human osteoblasts were observed with spindle shape on Nanoconcave, cells on Nanoflat were well-spreading but in sphere shape, while the osteoblasts on Nanoconvex were with the minimum spreading areas. Cell-materials interface is mediated and influenced by the adsorption of ECM on nanomaterials. Thus, a novel fibronectin adsorption model was proposed by calculating Coulomb's force to illustrate the interact mechanism between protein and material that influence cell behaviours. The achievements of thesis are; 1. Retrieval analyzed two cases of implants failure and pointed out one of dominated failure factor, the lack of osteointegration. 2. Introduce the interfacial bonding layer that significantly improve the biotribological and biocorrosive performance of NT, and generated SO-NT. 3. Systematically evaluated the biotribological performance of Ti, NT and SO-NT, and propose a novel methodology to quantify the fretting degradation on bone screws. 4. Propose a novel model to estimate the fibronectin adsorption on Nanoflat, Nanoconvex and Nanoconcave by the Coulomb's force calculation

Molecular Machinery For The ‘kiss And Run’ Mechanism Of Insulin Secretion

The insulin secreting porosome is a supramolecular lipo-protein complex that measures roughly 100 – 120 nm in diameter. Porosomes allow transient fusion of insulin secretory granules to the cell plasma membrane and mediates partial release of secretory contents. Post secretion, the secretory granule reseals and re-enters to the cell interior. This is in contrast to the ‘total fusion’ phenomenon, where secretory vesicles completely fuse at the cell plasma membrane and release all of the contents to the cell exterior. This study involved a deeper understanding of the transient or ‘kiss-and-run’ mechanism of cell secretion that involves the insulin secreting porosome complex. In addition to the porosome, two other components of transient cell secretion, namely the t/v SNARE complex and the insulin secreting granules (ISGs) were also studied. We demonstrated for the very first time in the history of porosomes, its functional and stable reconstitution into live insulin secreting mouse insulinoma cells leading to improved glucose stimulated insulin releasing from the reconstituted cells. Further, we demonstrated a drop in intracellular pH once a cell has been stimulated for secretion. This lowering of pH is critical for locking in place, the t/v SNARE complex that are present at the base of the porosome. We also demonstrated a loss in glucose stimulated insulin secretion upon prevention of intracellular acidification utilizing Bafilomycin A, a pharmacological inhibitor of the vacuolar proton pump (vH+ ATPase). The vH+ ATPase is also present on the insulin secretory granule membrane, which led to our fourth aim of this study. Valproate, is an FDA approved anticonvulsant that is widely used in the treatment of various neurological disorders such as epilepsy and mood disorders by disturbing vH+ ATPase activity in the neurons. Since, vH+ ATPase is also present on ISG membrane we wanted to understand effects of valproate on insulin secretion. We demonstrated that valproate treatment significantly reduces glucose stimulated insulin secretion. Additionally, we also demonstrated that valproate leads to de-localization of one of the cytosolic subunits of vH+ ATPase from the ISG membrane, preventing complete assembly of the proton pump. These results coherently suggest the importance of porosomes in transient cell secretion and its critical regulation via interaction with various proteins namely SNARE complex and ISG membrane proteins that allows for cell secretion

Neurological Disease Diagnosis and Treatment via Precise Robotic Intervention

This work focuses on the development and application of mechatronic systems for measurement, diagnosis and treatment of acute and chronic neurological conditions. The development of an automated tendon reflex stimulation device, as well as analysis and classification methods for both automated and manual stimulus delivery will provide the groundwork for improvements to both diagnosis and treatment of neurological injuries. In a similar vein, development of a variable resonance actuator for Magnetic Resonance Elastography imaging enables tissue property measurement of the intervertebral discs, hopefully providing an early marker and better understanding of degeneration. In addition to MRI based spinal tissue property measurements, an MRI guided high precision robot is developed for direct injection into the spinal cord, along with an accompanying image guided control scheme. The novel parallel plane mechanism enables control of 4 degrees of freedom, while the linear piezoelectric actuators in a direct drive configuration enables superior accuracy. Taken together, these robotic device developments constitute contributions to the field of precision medical robotics with applications to physiological understanding of the human body.Ph.D