Postgraduates: PACE
Seminar Series 2008
Friday Forums start at 3:30 pm and are held in the Doug McDonnell Building, Room 911 - unless otherwise stated.
29 Feb 2008 - Chayuda Chuanuwatanakul - Ceramic Foams for tissue engineering purpose
Nowadays, ceramic foams are used in various applications. The property requirements in each application are different. Tissue engineering is one application of ceramic foams which the most advantage of this is to extend patient life. The aim of this project is to fabricate and control the macro-, and micro- properties, the strength, porosity, pore size, and morphology, of ceramic foams for tissue engineering purpose. As these properties depend on chemical compositions, foaming method, and casting process, the effect of surfactant concentration, surfactant type, pH, and foaming method on the macro-, and micro- properties are investigated.
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29 Feb 2008 - Chong, Siow Feng - Encapsulation of Oligopeptides
A variety of oligopeptides have been synthesized as therapeutic vaccines in order to stimulate the process of artificial induction of immunity. However, these low molecular-weight drugs generally exhibit a short half-life in the blood stream and a high overall clearance rate. To decrease the adverse effects of such vaccination, encapsulation strategies are usually employed to prolong its blood residence and achieve targeted drug delivery. The present encapsulation of therapeutics utilises the layer-by-layer (LbL) technique to assemble conservative deposition of interacting polymers onto a colloidal particle. However, the current composition of capsules is too permeable to preserve small solutes such as oligopeptides. To resolve this problem, we propose an approach to encapsulate small peptide, with the conjugation of appropriate polymeric carrier so as to improve its efficiency to be trapped in the capsule. Herein, we report the preparation of conjugated oligopeptides, and its high concentration confinement within different sizes of degradable carrier vehicles.
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28 Mar 2008 - Innocent Beckard - Aβ40 A Amyloid Assembly: The Systematic Effect of Agitation
Amyloid ß-peptide fibrillation is a pathological hallmark of Alzheimer's disease. Although stirring is a common method used in inducing fibril formation in vitro, its mode of action is ill defined. The systematic effect of stirring on the formation of Aß40 fibril formation was studied. Stirring accelerated the nucleation as well as assembly phases of Aß40 fibrillation. It was established that oligomeric aggregates served as the building blocks in Aß40 fibril assembly and their formation is the rate-determining step in agitated Aß40 solutions. On the other hand, the emergence of protofibrils and acquisition of a ß-sheet structure consolidates fibril formation in quiescent Aß40 solutions. A mechanistic model of heat-induced Aß40 fibril assembly in the presence or absence of stirring is proposed.
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28 Mar 2008 - Melissa Leung - Loading Therapeutics
Nano- and microparticles labelled with specific cell targeting ligands like antibodies have attracted a great deal of interest in drug delivery. This project focuses on designing targeted drug delivery systems for the killer diseases colorectal cancer and thrombosis. Biocompatible, nano-/micrometre-scaled, multilayered, degradable polymer capsules are prepared as the drug delivery vehicles. These multilayered vehicles can be formed by the layer-by-layer (LbL) self-assembly technique or the coupling of LbL with click chemistry, giving the LbL and click-LbL capsules respectively. The therapeutic agent is either encapsulated or covalently linked to the capsules. Specific cleavage sites are constructed within the multilayers and cleavable only under certain physiological conditions, therefore a controlled drug release mechanism would be achieved. Lastly, these therapeutics-loaded LbL capsules will be surface functionalised with antibodies for the targeting purposes. Herein, we report preliminary studies on the loading of the therapeutics.
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30 May 2008 - Zuratul Ain Abdul Hamid - Synthesis of IPNs Hydrogel Scaffold for Tissue Engineering Application
Hydrogels are a potential type of biomaterial that has shown great promise as a scaffold for tissue engineering. These materials have tissue-like water contents, may be formed in situ for ease of implantation, and can encapsulate cells as they crosslink. The physical and biological properties of the hydrogel scaffold play an important role in the development of engineered tissues.
A way to reinforce the hydrogel is through interpenetrating polymer networks (IPNs). IPNs are defined as a combination of two or more intertwined polymers cross-linked into a matrix, with at least one of them being cross-linked in the immediate presence of the other. IPN-based biomaterials have been studied for drug delivery, tissue prosthesis and repair, and also wound healing. For that reason we have been investigating this approach to synthesize hydrogels with better mechanical and biocompatible properties. In this study, ?,?-diamino functionalized PCL was synthesised and reacted with the diepoxide, polyethylene glycol diglycidyl ether (PEGDGE), in the presence of the primary cross-linker, 1,2-ethylenediamine (EDA) or cystamine (CYS). Various Mw of a,w-diamino PCL was synthesised and incorporated into the hydrogel networks. The hydrophobicity properties of a,w-diamino PCL is expected to improve the hydrogel strength. The swelling and mechanical properties of the resulting IPN hydrogels were investigated with different amount of a,w-diamino PCL loading. Furthermore the toxicicty of these hydrogel was determined via MTS assay.
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30 May 2008 - Cameron Kinnane - Biocompatible films through the click LbL assembly method
Reducing protein and cell adhesion at the surface is crucial in the engineering of biomaterials for applications such as drug delivery, gene therapy and tissue engineering. We combine the Layer-by-Layer technique and highly efficient click chemistry to assemble a number of low-biofouling multilayer films from components such as poly(ethylene glycol). When contacted with a number of plasma proteins, these films demonstrate significantly less fouling in comparison with conventional multilayers. Furthermore, by functionalising these films with an adhesion promoting peptide we demonstrate specific cell adhesion and growth onto the films. These films demonstrate two important aspects of biomaterials; namely low-fouling and functionality. Given that the LbL technique can be applied to a myriad of templates, this general technique opens up new pathways for the development of bioreactors, biomarkers, surfaces for tissue engineering, and drug delivery devices.
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27 June 2008 -
Ranya Simons - An Investigation into the Structure-Property Relationships in Micro/Nano-reinforced Thermoplastic and Thermoset Polymer Systems.
There has been huge surge of interest over the last decade in polymer clay nanocomposites. Polymer-clay nanocomposites represent an attractive alternative to conventionally filled polymers, because even at very low concentrations of clay (1-5 weight %) significant property enhancements can be achieved, while at the same time decreasing the weight of the polymer. The clay montmorillonite has been widely investigated as a polymer filler due to its structure, which allows it to disperse under the correct conditions on a nano-scale into its individual sheets, leading to vastly improved properties. The ability of the montmorillonite to disperse or ‘exfoliate’ completely into nanosized individual clay platelets in a polymer matrix depends on the polarity and structure of the polymer and the interaction between the clay and the polymer. Most effort in this field has focused on either modifying the clay to become more organophilic or the polymer to become more hydrophilic. Polymer clay nanocomposites have been used in automobile components, and as packing materials, flame-retardants, protective films, electrical conductors and construction materials. Despite all the research in this field, the use of polymer clay composites in industry has not been as widespread as originally envisaged, partly because the exact chemical mechanism of exfoliation and the clay-polymer interaction is not well understood. This project aims to better understand the interactions between montmorillonite clay and the polymer matrix and thus be better placed to design nanocomposite materials. To this end, montmorillonite was organically modified to introduce vinyl functional groups which can participate in the free radical polymerization. By investigating different organic modifications, the effect of the architecture of the surfactant on the interactions of the clay and polymer can be understood, with a mind to determine the optimum structure.
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27 June 2008 -
Adrian Sulistio - Protein Crosslinking Using Natural Phenolic Compounds – A Study on the Development of Model System.
Protein crosslinking is important in the food industry because it can affect the texture of the food as well as influencing the solubility, foaming, whipping and emulsifying properties (Matheis and Whitaker, 1987). Not only that, it has also been used widely in medical research area such as tissue engineering and drug delivery system.
So far, aldehyde-based chemical crosslinkers have been used for protein crosslinking. However, the high toxicity of these chemical crosslinkers promoted the search for alternatives crosslinking agents which have lower toxicity and are preferably derived from nature. Naturally occurring phenolic compounds such as tannin and caffeic acid commonly found in plants and fruits such as coffee, grape, apple and pear has the potential to replace the chemical crosslinkers. This project aims to elucidate the covalent interaction between plant phenolic compounds and protein by developing a model system which would reduce the complication of the reaction. In doing so, the project hopes to gain understanding on how the crosslinking mechanism in protein system works as well as the relationship between the crosslinkers, cross-linked structures and their properties. This would help to design of a modified protein system with controlled properties which would have potential benefits in food processing applications, such as making a bio-degradable packaging film, such as synthetic sausage skin or chocolate packaging from gelatin. There is also a potential application in microencapsulation for drug delivery.
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27 June 2008 -
Anat Kiviti-Manor - The impact of aggregate densification on thickener performance
The aim of gravity thickening processes is to increase the solids concentration of particulate slurries via dewatering. The solids settle under gravity, creating a compact bed at the thickener base, while relatively solids free liquid rises to the overflow at the top of the thickener.
Gravity thickening depends on the difference in densities between the solid and liquid phases. Studies of a range of industrial thickeners show that current mathematical models underestimate thickener throughput at a given solids concentration by factors of up to 100. One phenomenon proposed to partially account for this discrepancy is aggregate densification, whereby aggregates compact and become smaller when subjected to low shear forces in the thickening process. As the aggregates densify and decrease in size, the tortuosities around the aggregates will decrease, thus leading to a significant net decrease in the resistance to fluid flow, which improves permeability and dewatering behavior. The impact of these phenomena on gravity thickening performance is predicted to be significant. The aim of this study is to quantify the relationship between shear force and dewatering performance for a range of floc formation conditions and flocculant types.
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25 July 2008 - Wade Mosse - Direct Peptide Synthesis on a Silicon Surface
This work introduces the use of solid phase peptide synthesis on a silicon substrate as a means of directly forming a peptide layer on a surface. We have synthesised a 15 residue peptide from the surface of an aminosilanized silicon wafer; the peptide contains a zwitterionic sequence of alternating lysine and glutamic acid residues. We confirmed the presence of the peptide layer on the surface by X-ray photoelectron spectroscopy (XPS) and ellipsometry. Atomic force microscopy (AFM) was then used to study the forces between the peptide-modified surface and a borosilicate glass sphere, and pH dependent behaviour consistent with the presence of the peptide was observed. Immobilisation of peptides at interfaces has previously been achieved by either physisorption or a “grafting to” approach. The “grafting from” method detailed in this work will allow the formation of peptide brushes and layers with much higher density than was previously possible, while also minimising the expense associated with the commercial purchase of peptides. Layers formed by this technique may be used instead of conventional polymer brushes to make use of the fine sequence control and range of functionalities available in peptides; the method also allows easy biofunctionalization of a surface for nanotechnology and biomedical applications.
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29 August 2008 - Mehdi Nasiri - Development of Mesoporous Materials for Bioseparation Applications
Mesoporous materials have attracted attention during the last 15 years for many applications like catalysis, biomolecular separation, enzyme immobilization, etc., owing to their sophisticated properties (e.g.
ordered pore structure and narrow pore size distribution). Among these applications protein separation is one of the most important processes, especially in the food industry (e.g. separation of wine proteins that cause haze formation). In this study we synthesised one kind of mesoporous silica with the name of FDU-12 using nonionic block copolymer
EO106PO70EO106 (EO is poly(ethylene oxide) and PO is poly(propylene
oxide)) as a template in acidic condition and tetraethyl orthosilicate
(TEOS) as the silica source. Characterisation of this material was done by gas adsorption methods and scanning electron microscopy. Surface functionalisation was conducted by sulfonic acid group to make it suitable for protein separation from wine model solution. -Lactoglobulin was chosen as a model of wine protein and adsorption was done with different synthesised and functionalised FDU-12.
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26 September 2008 - Peter Asimakis - Protein Aggregation during Processing
Protein therapeutics has emerged as one of the fastest growing areas of the pharmaceutical industry. A major issue for protein therapeutics is the susceptibility of proteins to denaturation during manufacture and their instability in liquid formulations. As a result, many protein therapeutic manufacturing processes are low yielding and often the final product is only stable in the frozen or freeze-dried form. Liquid formulation of protein therapeutics is desirable as it reduces manufacturing costs and enhances convenience to the end user. Instability of liquid formulation often presents as formation of aggregates upon storage. If the propensity for protein instability can be reduced during the manufacture and storage of protein therapeutics the safety, yield and shelf-life may be improved.
We have used two therapeutic proteins, immunoglobulin G (IgG) and albumin to investigate the effects caused by processing proteins and the causes of instability during formulation and manufacturing. We have focused on the shear rate (0-500 s-1) and temperature changes (20-80ºC), which are common during processing, typically in the form of mixing, pumping, filtering and pasteurisation. Protein unfolding was monitored by using the auto-fluorescence of tryptophan, while aggregation was monitored by using extrinsic dye binding. Our results show that protein unfolding and aggregation are dependent on shear rate. Protein unfolding was shown to be irreversible for shear flow and reversible for temperature changes.
Understanding the effects of processing on protein unfolding and aggregation can help in devising improvements to manufacturing processes which ensure product stability.
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26 September 2008 - Prang Chuanuwatanakul - Ceramic Foam for Engineering Application
Ceramic foams have use in a wide variety of applications such as particulate filters for diesel engines, molten metal filters and bone scaffolds. The aim of the research project is to investigate the factors that influence the amount, size and morphology (such as connectivity) of porosity. The focus is on gelcast, particle stabilized foams. The suspension contains a surfactant which makes the particles slightly hydrophobic. These hydrophobic particles stabilize the foam generated by whipping or beating, for example, because removal of the hydrophobic particles from the air solution interface requires energy. The suspension also contains a soluble polymer such as poly vinyl alcohol and a temperature activated crosslinking agent. The foam can then be gelled after casting into a complex shaped mould by heating up. The results indicate that the concentration of the surfactant has significant influence on the amount, size and morphology of the porosity.
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31st October 2008 - Josephine Lim - Start-of-pipe strategy to control swelling clay behaviour in suspension
Clays can be the source of significant problems in mineral processing operations. Due to their presence as impurities in low grade ores, they can cause issues such as high pumping energy consumption and poor tailings dewaterability. In order to minimize these clay-related issues, an efficient method to regulate the adverse behaviour of clay in suspension needs to be implemented. In this project, the utilisation of start-of-pipe strategy using controlled dispersion method is studied whereby the initial break-up of the dry clay on wetting is inhibited via chemical approaches. The effectiveness of the method on the swelling clay mineral subgroup is compared to the traditional end-of-pipe approach, which is normally done through coagulant addition into the tailings, well after the clays have been fully dispersed.
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31st October 2008 - Annette Haebich - Selective Adsorption of Chiral Molecules at Solid-liquid Interfaces
Chiral compounds are molecules that cannot be superimposed with their mirror image, which results in two distinct isomers called enantiomers. Biological molecules like amino acids and sugars are chiral and in nature nearly always appear in one form.
In pharmacology only one enantiomer may be medically active, whilst the other may not be effective or even cause an adverse reaction. Thus an enantiomerically pure synthesis is desirable but not always possible; so separation of the enantiomers is mostly done by chromatography on a chiral stationary phase. The separation efficiency depends upon the column material used in a specific system.
To make separation of chiral compounds more effective it is necessary to understand the interactions between chiral molecules with a chiral surface on a molecular level.
In this project interactions between amino acid surfactants and a chiral surface are studied by the use of attenuated total reflection infrared spectroscopy (ATR-IR).
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28th November 2008 - Nikko Chan - Polymer Molecule Deformation in Couette Flow
Polymer molecules in solution deform elastically under applied stress, and molecular theories have been developed which relate the elasticity to the entropy change induced through work done on the random chain. Theoretical models have assumed that the deformation of the polymer molecules is caused by extensional hydrodynamic forces in simple flow.
A polymeric system with fluorescence resonance energy transfer (FRET) end tags to allow direct measurement of end-to-end distances of the polymer molecules in response to the applied stress has been developed. Donor and acceptor FRET tags have been attached to the opposite ends of a monodisperse poly(methyl methacrylate) (PMMA) polymer system using the reversible-addition fragmentation chain transfer (RAFT) technique. FRET relies on non-radiative energy transfer between two fluorescent tags with spectral overlap in order to give a measure of the distance between the two tags. A fluorescent conjugated polymer system of MEH-PPV has been exposed to the same Couette shear flow to examine the effect of shear deformation on the molecules. The fluorescent properties of conjugated polymers are determined by the molecule conformation and length of conjugated segments.
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