Supramolecular Biopolymeric Composite Materials: Green Synthesis, Characterization and Applications

Macrocycles, such as crown ethers (CRs) and resorcinarenes (RESs), exhibit selective complexation of heavy metal ions and organic pollutants respectively. Consequently, they have been investigated for their suitability in adsorbing these aqueous pollutants. However, they are difficult to handle and recycle for reuse because, by themselves, they can only be fabricated in powder form. To alleviate this challenge, we developed a method to encapsulate these macrocycles into film-forming polysaccharides--cellulose (CEL) and chitosan (CS). This was achieved by using a green and recyclable solvent, an ionic liquid, to dissolve both macrocycles and polysaccharides and regenerate corresponding composites in water. Resultant composites were characterized by FTIR, UV-Visible, X-ray powder diffraction and scanning electron microscopy. These polysaccharides are attractive because they are naturally abundant, biodegradable and biocompatible. The composites retained desirable properties of their individual constituents, namely superior mechanical strength (from CEL), excellent adsorption capability for cadmium and zinc ions (from CRs and CS) and organic solutes (from RESs and CS). Specifically, increasing the concentration of CEL from 50% to 90% in [CEL+CR] resulted in almost 2X increase in tensile strength. Adding 40% benzo 15-crown-5 ether (B15C5) to CS led to a 4X enhancement in the amount of cadmium ions adsorbed by [CS+B15C5]. Interestingly, RES-based composites exhibited selectivity amongst dinitrobenzene (DNB) isomers. For example, one g of [CEL+RES] adsorbed more 1,2-DNB (5.37±0.05 mol L-1) than 1,3-DNB (4.52±0.03 mol L-1) and 1,4-DNB (2.74±0.04 mol L-1). These results help to extend the potential applications of supramolecular composites in water remediation. We also successfully synthesized hydroxyapatite (HAp) in situ by alternately soaking [CEL+CS] composite films in calcium and phosphate salt solutions. These composites will be expected to be osteoconductive (due to HAp), thereby necessitating their use in bone tissue engineering. In another related study, we developed a simple, one step process to encapsulate an antibiotic, ciprofloxacin (CPX) in composites containing various proportional concentrations of CEL, CS, and keratin (KER). KER was found to slow down the release of CPX from the composites. These results clearly indicate that the release of CPX can be controlled by judicious adjustment of the concentrations of KER in the composites

User-Centric Quality of Service Provisioning in IP Networks

The Internet has become the preferred transport medium for almost every type of communication, continuing to grow, both in terms of the number of users and delivered services. Efforts have been made to ensure that time sensitive applications receive sufficient resources and subsequently receive an acceptable Quality of Service (QoS). However, typical Internet users no longer use a single service at a given point in time, as they are instead engaged in a multimedia-rich experience, comprising of many different concurrent services. Given the scalability problems raised by the diversity of the users and traffic, in conjunction with their increasing expectations, the task of QoS provisioning can no longer be approached from the perspective of providing priority to specific traffic types over coexisting services; either through explicit resource reservation, or traffic classification using static policies, as is the case with the current approach to QoS provisioning, Differentiated Services (Diffserv). This current use of static resource allocation and traffic shaping methods reveals a distinct lack of synergy between current QoS practices and user activities, thus highlighting a need for a QoS solution reflecting the user services. The aim of this thesis is to investigate and propose a novel QoS architecture, which considers the activities of the user and manages resources from a user-centric perspective. The research begins with a comprehensive examination of existing QoS technologies and mechanisms, arguing that current QoS practises are too static in their configuration and typically give priority to specific individual services rather than considering the user experience. The analysis also reveals the potential threat that unresponsive application traffic presents to coexisting Internet services and QoS efforts, and introduces the requirement for a balance between application QoS and fairness. This thesis proposes a novel architecture, the Congestion Aware Packet Scheduler (CAPS), which manages and controls traffic at the point of service aggregation, in order to optimise the overall QoS of the user experience. The CAPS architecture, in contrast to traditional QoS alternatives, places no predetermined precedence on a specific traffic; instead, it adapts QoS policies to each individual’s Internet traffic profile and dynamically controls the ratio of user services to maintain an optimised QoS experience. The rationale behind this approach was to enable a QoS optimised experience to each Internet user and not just those using preferred services. Furthermore, unresponsive bandwidth intensive applications, such as Peer-to-Peer, are managed fairly while minimising their impact on coexisting services. The CAPS architecture has been validated through extensive simulations with the topologies used replicating the complexity and scale of real-network ISP infrastructures. The results show that for a number of different user-traffic profiles, the proposed approach achieves an improved aggregate QoS for each user when compared with Best effort Internet, Traditional Diffserv and Weighted-RED configurations. Furthermore, the results demonstrate that the proposed architecture not only provides an optimised QoS to the user, irrespective of their traffic profile, but through the avoidance of static resource allocation, can adapt with the Internet user as their use of services change.France Teleco

Delay aspects in Internet telephony

In this work, we address the transport of high quality voice over the Internet with a particular concern for delays. Transport of interactive audio over IP networks often suffers from packet loss and variations in the network delay (jitter). Forward Error Correction (FEC) mitigates the impact of packet loss at the expense of an increase of the end-to-end delay and the bit rate requirement of an audio source. Furthermore, adaptive playout buffer algorithms at the receiver compensate for jitter, but again this may come at the expense of additional delay. As a consequence, existing error control and playout adjustment schemes often have end-to-end delays exceeding 150 ms, which significantly impairs the perceived quality, while it would be more important to keep delay low and accept some small loss. We develop a joint playout buffer and FEC adjustment scheme for Internet Telephony that incorporates the impact of end-to-end delay on perceived audio quality. To this end, we take a utility function approach. We represent the perceived audio quality as a function of both the end-to-end delay and the distortion of the voice signal. We develop a joint rate/error/playout delay control algorithm which optimizes this measure of quality and is TCP-Friendly. It uses a channel model for both loss and delay. We validate our approach by simulation and show that (1) our scheme allows a source to increase its utility by avoiding increasing the playout delay when it is not really necessary and (2) it provides better quality than the adjustment schemes for playout and FEC that were previously published. We use this scheme in the framework of non-elevated services which allow applications to select a service class with reduced end-to-end delay at the expense of a higher loss rate. The tradeoff between delay and loss is not straightforward since audio sources may be forced to compensate the additional losses by more FEC and hence more delay. We show that the use of non-elevated services can lead to quality improvements, but that the choice of service depends on network conditions and on the importance that users attach to delay. Based on this observation, we propose an adaptive service choosing algorithm that allows audio sources to choose in real-time the service providing the highest audio quality. In addition, when used over the standard IP best effort service, an audio source should also control its rate in order to react to network congestion and to share the bandwidth in a fair way. Current congestion control mechanisms are based on packets (i.e., they aim to reduce or increase the number of packets sent per time interval to adjust to the current level of congestion in the network). However, voice is an inelastic traffic where packets are generated at regular intervals but packet size varies with the codec that is used. Therefore, standard congestion control is not directly applicable to this type of traffic. We present three alternative modifications to equation based congestion control protocols and evaluate them through mathematical analysis and network simulation

Online learning on the programmable dataplane

This thesis makes the case for managing computer networks with datadriven methods automated statistical inference and control based on measurement data and runtime observations—and argues for their tight integration with programmable dataplane hardware to make management decisions faster and from more precise data. Optimisation, defence, and measurement of networked infrastructure are each challenging tasks in their own right, which are currently dominated by the use of hand-crafted heuristic methods. These become harder to reason about and deploy as networks scale in rates and number of forwarding elements, but their design requires expert knowledge and care around unexpected protocol interactions. This makes tailored, per-deployment or -workload solutions infeasible to develop. Recent advances in machine learning offer capable function approximation and closed-loop control which suit many of these tasks. New, programmable dataplane hardware enables more agility in the network— runtime reprogrammability, precise traffic measurement, and low latency on-path processing. The synthesis of these two developments allows complex decisions to be made on previously unusable state, and made quicker by offloading inference to the network. To justify this argument, I advance the state of the art in data-driven defence of networks, novel dataplane-friendly online reinforcement learning algorithms, and in-network data reduction to allow classification of switchscale data. Each requires co-design aware of the network, and of the failure modes of systems and carried traffic. To make online learning possible in the dataplane, I use fixed-point arithmetic and modify classical (non-neural) approaches to take advantage of the SmartNIC compute model and make use of rich device local state. I show that data-driven solutions still require great care to correctly design, but with the right domain expertise they can improve on pathological cases in DDoS defence, such as protecting legitimate UDP traffic. In-network aggregation to histograms is shown to enable accurate classification from fine temporal effects, and allows hosts to scale such classification to far larger flow counts and traffic volume. Moving reinforcement learning to the dataplane is shown to offer substantial benefits to stateaction latency and online learning throughput versus host machines; allowing policies to react faster to fine-grained network events. The dataplane environment is key in making reactive online learning feasible—to port further algorithms and learnt functions, I collate and analyse the strengths of current and future hardware designs, as well as individual algorithms

Integrity and access control in untrusted content distribution networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Vita.Includes bibliographical references (p. 129-142).A content distribution network (CDN) makes a publisher's content highly available to readers through replication on remote computers. Content stored on untrusted servers is susceptible to attack, but a reader should have confidence that content originated from the publisher and that the content is unmodified. This thesis presents the SFS read-only file system (SFSRO) and key regression in the Chefs file system for secure, efficient content distribution using untrusted servers for public and private content respectively. SFSRO ensures integrity, authenticity, and freshness of single-writer, many-reader content. A publisher creates a digitally-signed database representing the contents of a source file system. Untrusted servers replicate the database for high availability. Chefs extends SFSRO with key regression to support decentralized access control of private content protected by encryption. Key regression allows a client to derive past versions of a key, reducing the number of keys a client must fetch from the publisher. Thus, key regression reduces the bandwidth requirements of publisher to make keys available to many clients.(cont.) Contributions of this thesis include the design and implementation of SFSRO and Chefs; a concrete definition of security, provably-secure constructions, and an implementation of key regression; and a performance evaluation of SFSRO and Chefs confirming that latency for individual clients remains low, and a single server can support many simultaneous clients.by Kevin E. Fu.Ph.D

Bioactive Membranes and Nanocoatings for Guided Tissue Regeneration in Periodontal Diseases

Periodontal diseases are highly prevalent in population of all ages. Initiated by bacterial accumulation at the interface of bone and soft tissue, they lead to the loss of gingival tissue adherent to the root surface and, eventually, to tooth loss. Regenerative approaches to treat periodontitis offer exciting possibilities; guided tissue/bone regeneration (GTR/GBR) approaches are promising because, through the insertion of a physical barrier, they can exclude unwanted epithelial and gingival connective tissue cells from the healing area and allow bone tissue cells to repopulate the bony defect. Different resorbable and non-resorbable membranes have been developed. Expanded polytetrafluoroethylene (ePTFE) membranes are the “gold standard” for GTR/GBR applications but they are non-resorbable and they need a second surgical operation to repair dehiscence. Biodegradable synthetic membranes avoid a second surgical operation but they show drawbacks concerning the capacity of space maintenance, early/late absorption, mechanical properties and bacterial infection during degradation. Collagen membranes have advantages related to collagen biological properties but are characterized by low mechanical strength. The “ideal” membrane for use in periodontal regenerative therapy has yet to be developed. The main purpose of this thesis was the design of biologically active products, with improved osteoconductive and antimicrobial properties, for GTR/GBR applications in periodontal diseases. In a more traditional approach, a commercially available membrane (based on PTFE) was surface modified by environmentally friendly technique to allow rapid bone re-growth and exert antimicrobial action. Binding ability of 3,4-dihydroxy-DL-phenylalanine (DOPA) to samples of any type, size and shape was exploited to improve PTFE surface properties. In particular, a hydroxyapatite nanoparticles (HAp) coating was applied by DOPA self-polymerization on PTFE surface in the presence of HAp nanoparticles, to promote the bone re-growth properties of PTFE films. Chemical composition analysis demonstrated the successful deposition of polyDOPA and HAp on coated films. Morphological and topographical characterizations further confirmed the total surface coverage causing an increase in surface roughness (39.8±5.2 nm for PTFE films vs 236.5±12.0 nm for polyDOPA/HAp coated films) and wettability (110.8±2.8° for PTFE films vs 46.1±12.4° for polyDOPA/HAp coated samples). A discontinuous HAp coating was still present after 14 days of incubation of coated PTFE films in phosphate buffered saline. Pre-osteoblastic MC3T3-E1 cells cultured on polyDOPA/HAp coated films showed a pronounced increase of cell proliferation and adhesion. Regarding the antimicrobial action, silver nanoparticles (AgNPs) have been selected due to their good antimicrobial efficacy against bacteria, viruses and other eukaryotic micro-organisms. The successful deposition of AgNPs on PTFE surface, through the functional groups of DOPA, has been demonstrated by physico-chemical and morphological analyses. Nanoparticles exhibited a diameter around 68 nm and were homogeneously distributed on the surface. In vitro cell tests with fibroblast NIH 3T3 cells showed an inhibition of cells proliferation on AgNPs functionalized films after 3 days of culture, while good cell adhesion was observed with cells randomly distributed on sample surface and extensively spread. The antimicrobial efficiency was demonstrated against S. aureus and Ag release was sustained for at least 14 days. The mussel-inspired coated PTFE membrane could find potential application as GTR/GBR strategy for the treatment of periodontal diseases. In a highly innovative approach, a bi-layered bioabsorbable membrane was developed, by the assembly of a compact and a porous layer. GTR/GBR membranes can be considered an interface-implant between gingival connective tissue/epithelium and alveolar bone tissue. Developing a multi-component structure membrane with compositional and structural gradients that meet the local functional requirements could represent a challenge. Binary blends of poly(DL-lactide-co-ε-caprolactone) (PLCL) and poly(DL-lactide-co-glycolide) (PLGA) with various compositions (100/0, 75/25, 50/50, 25/75, 0/100 wt/wt) were prepared by solvent casting technique as compact layer of the bi-layered membrane. Morphological analysis did not evidence phase separation between PLCL and PLGA and the behavior of blend glass transition temperatures as a function of composition suggested some degree of blend compatibility. However, blends elastic modulus showed a negative deviation from the additive law of mixture. In vitro cell tests with fibroblast NIH 3T3 cells showed improved cell adhesion and growth on PLCL/PLGA 25/75 blend. Due to its biocompatibility, its superior mechanical properties (E=10.2±0.6 MPa, σmax=0.8±0.0 MPa, and εmax=548.8±57.9%) and compatibility between the components, PLCL/PLGA 25/75 blend was selected for this application. Compact films were then surface modified via layer-by-layer (LbL) technique to enhance fibroblast cell response and confer antibacterial efficacy. A surface priming treatment (aminolysis) was optimized before depositing LbL coating. The following parameters were used: C=0.08 g/mL, t=8 min and T=37 °C. Then, multilayered chondroitin sulfate/chitosan (CHS/CH) coatings were deposited on the aminolysed films. The feasibility of multilayer coating was confirmed by QCM-D analysis. Further confirmations derived from water contact angle measurements (contact angle jumped alternatively between 45° and 65° depending on the outmost layer component) and FTIR-ATR analysis (appearance of absorbance peaks characteristics of CHS and CH). FTIC-labelled CH was also employed to follow LbL built up by fluorescence microscopy analysis. In vitro cell tests demonstrated the ability of coated samples to improve NIH 3T3 fibroblast adhesion and proliferation. Biocompatibility properties increased with increasing the layer number and were superior in the case of CH-terminating layers but no antibacterial activity was observed for films coated with 16 layers. Three dimensional sponge-like composite membranes fabricated by freeze-drying, with a composition similar to natural bone, and based on β-tricalcium phosphate (TCP) dispersed in a chitosan/gelatin (CH/G) network cross-linked with genipin (GP) and disodium phosphate salt (DSP) were developed as porous layer of the bi-layered device. Three membranes were developed (CH/G, CH/G+GP-DSP and CH/G/TCP+GP-DSP) and characterized. Successful double cross-linking of CH/G network was confirmed by Kaiser test, chemical and thermal analysis. All membranes showed a typical foam-like morphology with interconnected pores having an average diameter of 100-200 μm. Both cross-linking and TCP presence caused a marked increase of membrane stability in water solution, as well as of tensile modulus and maximum tensile strength (respectively, 14.9±5.1 MPa and 0.6±0.0 MPa for CH/G, and 29.4±2.7 MPa and 0.8±0.1 MPa for CH/G/TCP+GP-DSP.). Compared to CH/G samples, CH/G+GP-DSP and CH/G/TCP+GP-DSP membranes showed improved MG-63 human osteoblast-like cells response, in terms of cell viability and morphology. The assembly process of the compact and porous layer was developed based on the insertion of an intermediate adhesive layer composed by a polyvinylpyrrolidone/polyethylene glycol 70/30 wt/wt blend. Preliminary characterizations were carried out. Morphological analysis did not show changes in compact and porous layer structure due to the presence of the adhesive. The final device showed an elastic modulus of about 61 MPa in dry condition that markedly decreased in wet state (to about 5 MPa). Qualitative analysis of membrane manageability revealed its ability to adapt to mandible conformation after immersion in physiological solution. Despite the need for additional tests, the bi-layered membrane appeared promising for GTR/GBR applications

Biomineralization

This open access book is the proceedings of the 14th International Symposium on Biomineralization (BIOMIN XIV) held in 2017 at Tsukuba. Over the past 45 years, biomineralization research has unveiled details of the characteristics of the nano-structure of various biominerals; the formation mechanism of this nano-structure, including the initial stage of crystallization; and the function of organic matrices in biominerals, and this knowledge has been applied to dental, medical, pharmaceutical, materials, agricultural and environmental sciences and paleontology. As such, biomineralization is an important interdisciplinary research area, and further advances are expected in both fundamental and applied research

Development of Novel Strategies for Musculoskeletal Tissue Engineering

The drastic rise in the world’s population coupled to an ever increasing aging population poses a considerable challenge to the orthopaedic community to maintain healthy activity levels. The field of Tissue Engineering and Regenerative Medicine aims to tackle these challenges by implementing more biomimetic strategies to improve upon current treatments. The success of new therapeutic developments in musculoskeletal tissue engineering relies on our ability to study and understand the complex biological interactions between cells, materials, and native tissues so that we may subsequently guide neotissue formation. This thesis is focused on the development of novel, welldefined, and reproducible in-vitro tissue culture models to explore, characterise, and control cellular behaviour and differentiation for osteochondral regeneration. In particular, these models utilised combinations of polymeric biomaterials, differentiated osteoblasts, human periosteal stem cells, and physico-chemical cell signalling cues. In a commercial venture with PolyNovo Ltd (Melbourne, Australia), a novel two-component injectable polymer platform was synthesized and evaluated for uses as a biomaterial construct in orthopaedic applications. The second aspect of this thesis focuses on the harvest, isolation, expansion, and extensive characterisation of human periosteal cells in-vitro. The periosteum is a bi-layered membrane that covers the outside of cortical bone and has been recently identified as a potential stem cell source; with the ability to form osteogenic, chondrogenic, adipogenic, and myogenic tissue types. To detail the heterogeneous cellular features and behaviours of human periosteal cells in-vitro, cells were isolated from surgical explants, expanding in monolayer in the absence of differentiation supplements, and characterised for changes in morphology, growth rate, cell-cycle, gene expression, and phenotype. Additionally, enrichment techniques were designed to preferentially isolate distinct progenitor cell types identified in periosteal cell cultures. Most interestingly, a novel cell-sorting platform utilising droplet microfluidic approaches, was developed and evaluated for its ability to identify and separate periosteal progenitor cells. In the third part of this thesis, a 3-dimensional agarose culture model was created to control and monitor lineage specific human periosteal cell differentiation in various biomechanical and biochemical environments. The work presented herein further demonstrates the potential of human periosteal cells for osteochondral repair and more importantly provides critical information regarding human periosteal cell expansion, phenotype, and differentiation

Sol-gel derived hydroxyapatite, fluorhydroxyapatite and fluorapatite coatings for titanium implants

Currently, most titanium implant coatings are made using hydroxyapatite and a plasma-spraying technique. There are however limitations associated with the plasma-spraying process including; poor adherence, high porosity and cost. An alternative - the sol-gel technique offers many potential advantages but is currently lacking research data for this application. Hydroxyapatite (HA), fluorhydroxyapatite (FHA) and fluorapatite (FA) have been synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the FHA and FA sol-gels. Optimisation and characterisation of the sol-gels was carried out using, X-ray Diffraction (XRD), High Temperature X-Ray Diffraction (HTXRD), Fourier Transform Infrared Analysis (FTIR) and Differential Thermal Analysis (DTA). Rheology and hydrophilicity of the sol-gels showed that increasing fluoride ion substitution caused an increase in viscosity and contact angle. The dissolution (Ca2+ and PO4 3-rates) rates of the fluoride-substituted powders from the sol-gels were considerably lower than that of HA and all rates could be decreased by increasing the sintering temperature. This suggests the possibility of tailoring the solubility of any coatings made from the sol-gels through fluoride ion substitution and increased sintering temperature. A spin coating protocol has been established for coating the sol-gels onto titanium. Increasing the coating speed decreased the porosity and thickness of the coatings. Bond strengths to titanium were investigated. Fluoride substitution and sintering temperature were shown to be important factors. Cellular proliferation studies revealed that increasing the level of fluoride substitution in the apatite structure significantly increased the biocompatibility of the material. The sol-gel technique may be an alternative to plasma spraying for coating titanium implants. Furthermore it may also be suitable for producing HA, FHA and FA as bone grafting materials