Postgraduates: PACE Seminar Series 2009

Friday Forums start at 3:30 pm and are held in the Chemical & Biomolecular Engineering Theatre - unless otherwise stated.

Please note the PACE AGM will be held on April 24th at 4:30pm following the seminar (same venue).

2008 presentations and abstracts

2007 presentations and abstracts

27th Feb 2009 - Innocent Bekard - Molecular Dynamics of Bovine Insulin Fibrillation Revealed by Intrinsic Tyrosine Fluorescence Quenching

The traditional approach to investigating the partial unfolding and fibrillation of insulin, and proteins at large, has involved use of the dyes 1-anilinonaphthalene-8-sulphonic acid (ANS) and Thioflavin T (ThT) respectively. We compare the kinetic profiles of ThT, ANS, light scattering and intrinsic Tyr fluorescence during insulin fibrillation. The data reveal that the sequence of structural changes (dimers - monomers - partially unfolded monomers - oligomeric aggregates - fibrils) accompanying insulin fibrillation can be detected directly using intrinsic Tyr fluorescence. The results indicate that at least two distinguishable structural intermediates precede fibril development. There is no evidence of tyrosinate or dityrosine during insulin aggregation. Obtaining such critical information from the protein itself affords the advantage of directly examining changes occurring at the molecular level; providing concrete detail on the early events preceding fibrillation. The absence of extrinsic fluorophores excludes the contributions of such molecules to the kinetics and structure of the fibrillating protein.

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27th Feb 2009 - John-Paul O'Shea - Solid-Liquid Separations with a Binary-Surfactant System

The application of temperature-responsive polymers to the field of solid-liquid separations presents manifold challenges. Experimentation in this area until now has shown the high separation efficiencies possible when the flocculant is added to a suspension at a temperature below the liquid-to-solid phase transition point of the polymer. However, poor separations occur when the polymer is added to suspensions above this critical temperature. In this presentation, in an attempt to canvas conditions closer to those found in industry, the problem of inducing flocculation when such polymers are added to high-temperature suspensions will be considered. To this end batch settling tests, competitive adsorption studies and indirect probes of solution hydrophobicity are used to demonstrate that separations can be achieved under these high temperature-polymer addition conditions.

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27th Mar 2009 - Nicolin Tirtaatmadja - Biomolecule Delivery Systems for Tissue Engineering and Skeletal Muscle Regeneration

Development of novel treatments for muscle wasting disorders and diseases is becoming a major field of health and medical research. Numerous diseases and conditions manifest symptoms of muscle wasting and/or weakness; including ageing, cancer cachexia, muscular dystrophies and physical trauma or injury. Treatments to alleviate or reverse these degenerative conditions will greatly improve the quality of life of many patients and may increase life expectancy. This project aims to develop systems which provide greater efficiency in the delivery of biomolecules for the treatment of muscle wasting disorders.

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27th Mar 2009 - Olga Kulygin - New Generation of Disulfide-Stabilized Capsules

Single-component (bio)degradable polymer capsules based on disulfide stabilized poly(methacrylic) acid, PMASH, have recently been developed for diverse biomedical applications including microencapsulated catalysis and controlled drug delivery. These capsules are obtained by the sequential deposition of thiolated poly(methacrylic acid) and poly(vinylpyrrolidone) (PVPON) onto silica particles, controlled oxidation of thiol groups into bridging disulfide linkages in the PMASH, removal of the silica particles, and finally, release of PVPON by altering the solution pH to disrupt hydrogen bonding between PMASH and PVPON.In this work, to gain a better control over permeability of the capsules and develop a facile surface fictionalization approach, we pioneered a strategy to retain PVPON, a low fouling non-toxic polymer, within the PMASH capsules. To achieve this, a sample of PVPON was successfully synthesized via RAFT polymerization, and its terminal groups were converted into an amine and a thiol to obtain a bifunctional polymeric linker. The terminal thiol group is then used to link PVPON to the PMASH network, while the amine terminus remains accessible for chemical modification and biofunctionalization. This was demonstrated with the use of biotin conjugation for specific protein binding. The novel capsules design afforded enhanced cargo retention, as will be shown on the example of siRNA encapsulation. The presented approach is expected to facilitate the development of polymer capsules with superior and controllable properties.

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21st Apr 2009 - Nathan Nicholas - The Influence of Shape Directing Molecules on the Nanostructure of Zinc Oxide During Dissolution

The hydrothermal growth of zinc oxide has undergone renewed interest in recent years due to the discovery that certain molecules, when introduced into the growth medium, can control the aspect ratio of single ZnO crystals. In contrast, little attention has been given to the process of dissolution and, in particular, how these same molecules affect the morphology of the etched ZnO. In this work Atomic Force Microscopy (AFM) was used to study the real time dissolution of m-plane (10-10) and c-plane (0001) ZnO under basic conditions in the presence of the known shape directing molecule tri-sodium citrate. Attenuated Total Internal Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) was then used to directly measure the bonding characteristics of citrate to the different faces of ZnO to better understand how these molecules control crystal morphology..

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21st Apr 2009 - Chris Ochs - Mesoporous silica capsules as versatile platforms for LbL assembled drug delivery vehicles

Recently, there has been a surge of interest in hollow silica capsules (HSCs) and spheres with well-defined morphologies due to their low density, high surface area and permeability, and possible applications in catalysis, separation, cosmetics and drug delivery. The main methods used for the synthesis of mesoporous silica structures include interfacial synthesis using micelles, emulsions, or polymer beads as sacrificial templates. Other approaches investigated the spontaneous dissolution-regrowth of silica capsules from solid spheres, combinations of surfactants to synthesize a variety of silica structures or high ammonia concentrations to achieve capsule formation without additional calcination to remove the sacrificial PS template core. Among solid templates, polystyrene (PS) beads are attractive templates, which are commercially available in a range of sizes, surface functionality, monodispersity and at relatively low cost. Usually, the template is easily removed after silica formation by either calcination at elevated temperatures or dissolution with organic solvents. The resulting capsules can be further modified and polymer-coated using Layer-by-Layer assembly for possible applications as drug delivery systems.

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29th May 2009 - 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. Also, different carbon chain length of surfactant tail affect the microstructure of ceramic gelled bodies.

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29th May 2009 - Jinguk Kim (Department of Environmental Engineering and Biotechnology, Myongji University, Republic of Korea) - Facilitated transport of CO2 through immobilization of carbonic anhydrase on poly(vinyl alcohol) membranes

Carbon dioxide (CO2) capture is of great importance for energy production and environmental protection of the atmosphere. Concerns over global warming consequent to the release of CO2, the most important greenhouse gas, continue to grow. The best available technologies to abate CO2 include liquid absorption using a chemical solvent such as monoethanolamine, cryogenic separation, absorption through porous solids such as alumina and activated-carbon, and membrane separation. Due to modularity and ease of operation, membrane technologies for CO2 separation would be a promising alternative option. In this study, we fabricated bio-mimic gas separation membranes with a well-known enzyme, carbonic anhydrase (CA). Carbonic anhydrases are among the most active enzymes known to transform CO2 into bicarbonate and proton in aqueous phase. The turnover rate can be as high as 1.4x106 CO2 molecule per enzyme molecule per second. Cross-linked poly(vinyl alcohol) (PVA) membrane was used as a support material, with its hydroxyl groups serving as linkers to the amine groups of CA. The fixation of CA was performed with a simple imidocarbonate reaction by varying the concentrations of CA in the membranes. The membranes for permeation experiment were placed between the gas phase where a gas mixture of CO2 and N2 was applied, and the liquid phase where the gas permeates and the transformed bicarbonates and protons are dissolved. The characteristics of CA on the transport of CO2 through the membrane and the transformation of CO2 into bicarbonate were investigated for different permeation conditions such as the applied concentration of CO2, pH of the medium, and temperature.

26th June 2009 - Stefanie Sham - Synthesis of Hollow Silica Shells - for the use in Total Internal Reflection Microscopy (TIRM)

The application of hollow microspheres has attracted immense attention in recent decades. In order to gain more insights into the basic fundamentals of forces between two interacting surfaces, hollow shells will be utilised in force measurements in Total Internal Reflection Microscopy (TIRM). This presentation aims to discuss the synthesis methods that were employed in generating hollow silica shells as well as the characterisation of their mechanical strength.

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26th June 2009 - Cameron Kinnane - Low-fouling and low-cytotoxic polymer films and capsules by the Click Layer-by-Layer technique

Polymers such as poly(vinyl pyrrolidone) (PVPON) and poly(ethylene glycol)
(PEG) are highly attractive for use in biomaterials due to their well-known low cytotoxicity and capacity to reduce the absorption of proteins. However, the key characteristic that makes PEG and PVPON suitable, namely their inertness, also presents a challenge in developing stable biomaterials by conventional assembly techniques. The combination of highly efficient covalent click chemistry and the Layer-by-Layer (LbL) method of sequential assembly of components based on molecular interactions provides a number of means of constructing robust, covalently assembled materials using uncharged, low-fouling polymers. PEG-on-PEG films were assembled using this click LbL approach and were rendered cell responsive by post-functionalization with a variant of the tripeptide sequence arginine–glycine–aspartate (RGD) to promote specific cell adhesion and growth on the films. PVPON microcapsules were also assembled which could be constructed under model intracellular conditions.
Furthermore, these capsules were found to be low-fouling to a number of proteins and showed negligible cytotoxicity to human colon cancer cell lines by MTT assay. With the ability to assembly inherently low-cytotoxic and low-fouling films and capsules, these click LbL materials offer potential in a number of bioapplications, including tissue engineering, drug delivery, and biosensing.

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