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(2011)Journal ArticleThick anatase films were fabricated on graphite substrates using a method of anodic aqueous electrophoretic-deposition using oxalic acid as a dispersant. Thick films were subsequently fired in air and in nitrogen at a range of temperatures. The morphology and phase composition were assessed and the photocatalytic performance was examined by the inactivation of Escherichia coli in water. It was found that the transformation of anatase to rutile is enhanced by the presence of a graphite substrate through reduction effects. The use of a nitrogen atmosphere allows higher firing temperatures, results in less cracking of the films and yields superior bactericidal performance in comparison with firing in air. The beneficial effects of a nitrogen firing atmosphere on the photocatalytic performance of the material are likely to be a result of the diffusion of nitrogen and carbon into the TiO2 lattice and the consequent creation of new valence band states.
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(2022)ThesisAntibodies are increasingly useful therapeutics, and examples include the checkpoint inhibitors pembrolizumab1 and ipilimumab2 in cancer immunotherapy, and anti tau therapies in Alzheimer’s disease and dementia.3,4 However, specific applications requiring cytosolic delivery of the antibody, or transport across the blood-brain barrier pose challenges to antibody therapeutics. These issues may reduce the effectiveness of immunotherapy and restrict it to extracellular targets. Conjugating polymers to proteins and enzymes has been very effective at improving their stability and pharmacokinetics,5–8 and similar approaches have been studied for antibody conjugation.9–12 Finding an effective polymeric delivery system for antibodies can greatly improve immunotherapy. In this work three strategies were explored for the encapsulation and bioconjugation to antibodies. The first approach is the encapsulation via electrostatic interactions between the antibody and a charged block copolymer to form polyion complex (PIC) micelles. Polyphosphonium block copolymers were studied for the first time to encapsulate antibodies, and were compared to their ammonium counterpart. While this approach has the advantage of being reversible, the polymer-antibody electrostatic interactions were too weak for biological applications, and delivery by this means would require a crosslinking strategy. The second approach involves covalent attachment of polymers on the antibody’s surface via a grafting from polymerisation. An oxygen tolerant technique was employed for the screening of a large number of samples in low volumes (<100 μL). Successful grafting was demonstrated by AF4 and gel electrophoresis. Enzyme-linked immunosorbent assay (ELISA) showed retention of up to 40% binding activity relative to the native antibody with a marked improvement in stability. The third strategy introduces a novel acid sensitive linker for the reversible covalent attachment of polymers to the antibody’s surface. This was achieved by using Diels-Alder chemistry to create an activated PEG that forms an amide with a conformational lock similar to citraconic anhydride upon conjugation to the amines on the antibody. The ability of the linker to cleave at pH 5.5 is demonstrated, resulting in almost complete recovery of the original binding activity of the antibody. Overall, the reversible covalent attachment investigated here seems the most promising, and combining the high throughput method with the cleavable linker approach holds great potential for advancing in immunotherapy. References (1) Reck, M. Pembrolizumab as First-Line Therapy for Metastatic Non-Small-Cell Lung Cancer. Futur. Med. 2018, 10, 93–105. (2) Gao, J.; Ward, J. F.; Pettaway, C. A.; Shi, L. Z.; Subudhi, S. K.; Vence, L. M.; Zhao, H.; Chen, J.; Chen, H.; Efstathiou, E.; Troncoso, P.; Allison, J. P.; Logothetis, C. J.; Wistuba, I. I.; Sepulveda, M. A.; Sun, J.; Wargo, J.; Blando, J. VISTA Is an Inhibitory Immune Checkpoint That Is Increased after Ipilimumab Therapy in Patients with Prostate Cancer. Nat. Med. 2017, 23 (5), 551–555.. (3) Pedersen, J. T.; Sigurdsson, E. M. Tau Immunotherapy for Alzheimer’s Disease. Trends Mol. Med. 2015, 21 (6), 394–402. (4) Castillo-Carranza, D. L.; Sengupta, U.; Guerrero-Munoz, M. J.; Lasagna-Reeves, C. A.; Gerson, J. E.; Singh, G.; Estes, D. M.; Barrett, A. D. T.; Dineley, K. T.; Jackson, G. R.; Kayed, R. Passive Immunization with Tau Oligomer Monoclonal Antibody Reverses Tauopathy Phenotypes without Affecting Hyperphosphorylated Neurofibrillary Tangles. J. Neurosci. 2014, 34 (12), 4260–4272. (5) Abolmaali, S. S.; Tamaddon, A. M.; Salmanpour, M.; Mohammadi, S.; Dinarvand, R. Block Ionomer Micellar Nanoparticles from Double Hydrophilic Copolymers, Classifications and Promises for Delivery of Cancer Chemotherapeutics. Eur. J. Pharm. Sci. 2017, 104 (January), 393–405. (6) Kurakhmaeva, K. B.; Djindjikhashvili, I. A.; Petrov, V. E.; Balabanyan, V. U.; Voronina, T. A.; Trofimov, S. S.; Kreuter, J.; Gelperina, S.; Begley, D.; Alyautdin, R. N. Brain Targeting of Nerve Growth Factor Using Poly(Butyl Cyanoacrylate) Nanoparticles. J. Drug Target. 2009, 17 (8), 564–574. (7) Jiang, Y.; Fay, J. M.; Poon, C. D.; Vinod, N.; Zhao, Y.; Bullock, K.; Qin, S.; Manickam, D. S.; Yi, X.; Banks, W. A.; Kabanov, A. V. Nanoformulation of Brain-Derived Neurotrophic Factor with Target Receptor-Triggered-Release in the Central Nervous System. Adv. Funct. Mater. 2017, 1703982, 1–11. (8) Klyachko, N. L.; Manickam, D. S.; Brynskikh, A. M.; Uglanova, S. V.; Li, S.; Higginbotham, S. M.; Bronich, T. K.; Batrakova, E. V.; Kabanov, A. V. Cross-Linked Antioxidant Nanozymes for Improved Delivery to CNS. Nanomedicine Nanotechnology, Biol. Med. 2012, 8 (1), 119–129. (9) Bin Liu, Khushboo Singh , Shuai Gong , Mine Canakci, Barbara A. Osborne, and S. T. Protein Antibody Conjugates PACs A Plug‐and‐Play Strategy for Covalent Conjugation and Targeted Intracellular Delivery of Pristine Proteins. Angew. Chemie 2021, 133, 12923–12928. (10) Chan, L. J.; Bulitta, J. B.; Ascher, D. B.; Haynes, J. M.; Mcleod, V. M.; Porter, C. J. H.; Williams, C. C.; Kaminskas, L. M. PEGylation Does Not Signi Fi Cantly Change the Initial Intravenous or Subcutaneous Pharmacokinetics or Lymphatic Exposure of Trastuzumab in Rats but Increases Plasma Clearance after Subcutaneous Administration. Mol. Pharm. 2015, 12, 794–809. (11) Subasic, C. N.; Ardana, A.; Chan, L. J.; Huang, F.; Scoble, J. A.; Butcher, N. J.; Meagher, L.; Chiefari, J.; Kaminskas, L. M.; Williams, C. Poly ( HPMA- Co -NIPAM ) Copolymer as an Alternative to Polyethylene Glycol-Based Pharmacokinetic Modulation of Therapeutic Proteins. Int. J. Pharm. 2021, 608 (September), 121075. (12) Keita Hironaka,a,b Erika Yoshihara, Ahmed Nabil, James J. Lai, A. K. and M. E. Conjugation of Antibody with Temperature-Responsive Polymer via in Situ Click Reaction to Enable Biomarker Enrichment for Increased Diagnostic Sensitivity. Biomater. Sci. 2021, 9, 4870–4879.
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(2022)ThesisChronic wounds are a major issue in public health. One of the contributing factors in the development of chronic wounds is bacterial infection, which is exacerbated by the presence of multidrug-resistant (MDR) bacteria. One approach to tackle wound infection is the use of non-antibiotic antimicrobials with rapid killing effect without inducing resistance. This thesis aims to investigate the application of antimicrobial polymers and iodine in the development of antimicrobial wound dressing platforms. Firstly, contact-active antimicrobial wound dressings were explored. An inert silk sponge was prepared as the substrate and functionalized with antimicrobial polymers on the surface via layer-by-layer assembly. Electrostatic interactions in the multilayer construct confined the antimicrobial polymers and prevented leaching. The sponge was able to suck bacteria into the porous network and kill them upon contact as evidenced by up to 4 log10 reduction against Gram-negative and Gram-positive bacteria. Additionally, the antimicrobial efficacy was found to be strongly affected by the construction of multilayer assembly. As the contact-active mechanism may reach saturation point on the surface, in the second approach, an antimicrobial platform with a release-killing mechanism was developed. Employing the ability of silk to self-assemble into a thin film, antimicrobial polymers were loaded in the silk matrix. The release of antimicrobial polymers correlated to polymer concentration, silk to polymer ratio, and film configuration. The efficacy of the films was demonstrated by 5 to 7 log10 reduction of planktonic and 3 to 7 log10 reduction of biofilm cells against Pseudomonas aeruginosa and Staphylococcus aureus, including MDR strains. Furthermore, the straightforward coating method was as effective on glass or cotton substrates. The third approach investigated the immobilization of iodine onto wound dressings for a sustained release system. The immobilization was facilitated by polyamide iodophors that were synthesized on the dressing via plasma polymerization of the gaseous amide monomers. The antimicrobial activity correlated strongly to the structure of the polyamide with the short and linear polymer recorded 4 log10 reduction against P. aeruginosa and 7 log10 reduction S. aureus, including a MDR strain. Overall, the immobilization of iodophors on wound dressings demonstrated a potential new approach in reducing bacteria proliferation in wounds.
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(2018)ThesisGraphene oxide is a single layer of carbon atoms with decorated oxygen functional groups. Stacked monolayers in the laminate form create an interlayer space of sub-nanometer scale with oxygenated functional group to attract water molecules, and graphitic domains to allow frictionless flow of water molecules and achieve maximum efficiency of water transportation. The research reported herein is aimed to understand and explore characteristics of the diffusion-dependent mass transportation across an array of cascading nanochannels confined by graphene oxide laminates at sub-nanometer level. This dissertation has 6 Chapters. Chapter 1 is the introduction and Chapter 2 reports the recent progress in graphene oxide for mass transport application. Chapter 3 discusses efforts of engineering the channel confinement, which is represented by the interlayer spacing in between graphene oxide laminates. By adjusting the fundamental factors of graphene oxide suspension, the interlayer spacing can be controlled at 0.7 to 0.8 nm. Based on the engineered interlayer spacing, separation of vaporous mixture by graphene oxide membrane is studied in Chapter 4. Numerical description of nanochannels enclosed by graphene oxide monolayers is determined by time lag analysis. The feature of ethanol vapor transportation with the support of water vapor is revealed, showing accelerated transportation of non-permeable matter, which enriches the existing knowledge. A geometrical model of graphene oxide membrane for vapor separation was established and analyzed. In Chapter 5, adsorption and intercalated of molecules and solvated ions are studied and proved as a size-dependent enlargement of graphene oxide nanochannels. Carriers such as water and ethanol are used for transporting ions and molecules into graphene oxide slits. Taking the adsorption into consideration, permeation of vaporous substances through adsorbed graphene oxide membrane is investigated in Chapter 6. The research initiates researching crystallization of adsorbed matters in graphene oxide interlayer structure. A simplified model was directed to predict the water vapor permeation behavior of intercalated graphene oxide membrane. Such efforts not only lead to a better understating of graphene oxide membrane for gas separation but also give a hint of spatially efficient matter transport in achieving excellent electrochemical devices with graphene oxide components.
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(2023)ThesisEpidemic thunderstorm asthma (ETSA) outbreaks are triggered by airborne pollen allergens combined with thunderstorm activity. ETSA can affect anyone, as observed in the world’s largest ETSA event in Australia. Allergens from rye grass pollen affect the respiratory airways and the fundamental physicochemical causes, biochemical interactions, and the role of the thunderstorm in ETSA have been the source of much speculation. In this thesis, the physicochemical interactions of thunderstorm-derived reactive oxygen nitrogen species (RONS) and pollen-derived molecules are examined. It is hypothesised that RONS from the plasma-activated water (PAW) react with the airborne pollen allergens, exerting physicochemical changes to enhance allergenicity and subsequently causing ETSA. Simple biomimetic models are demonstrated, examining the key biointerfacial interactions and the influences of the conditions of plasma formation, pH, and temperature, employing advanced interface-sensitive techniques including QCM-D and neutron reflectometry. Firstly, cellulose-mucin interactions were analysed, mimicking the interactions between the walls of inhaled pollen (intine) and mucosa of the respiratory tract (mucin). Interaction with plasma-treated cellulose surfaces led to adsorption and conformational alterations to mucin, potentially indicating changes to the permeability of the mucosa. Secondly, the effect of PAW on the interactions between a model-allergen plant protein and lipid monolayers mimicking alveolar surfactant was studied. The protein took up RONS and PAW-treated protein showed stronger adsorption to the lipid monolayers, implying PAW-treatment enhances transport of the protein into lung tissue. Lastly, the effect of PAW on allergen penetration into epithelial bilayers was elucidated. Solid-supported model lipid bilayers were allowed to interact with model allergen and rye grass derived proteins to deduce the structural integrity of the membrane. PAW-treatment increased adsorption of the proteins to the lipid bilayers, and enabled the penetration into the membrane, corroborating the enhanced allergenicity of PAW-treated allergens. Overall, PAW was seen to enhance three relevant nonspecific biointerfacial interactions; these physicochemical studies complement extant in vitro cell studies in an effort to enable the development of effective monitoring platforms, diagnostics, and therapeutic interventions for the prevention and treatment of ETSA.
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(2023)ThesisTumbling ball milling is a critical comminution process in materials and mineral processing industries. It is an energy intensive process with low energy efficiency. It is important that ball mills and the milling process are properly designed and operated. To achieve this, models at different scales are needed to provide accurate prediction of mill performance under various conditions. This study aimed to develop a combined discrete element method (DEM) and machine learning (ML) modelling framework to link mill design, operation parameters with particle flow and mill efficiency. A scale-up model was developed based on DEM simulations to link mill size ratio, rotation rate, and filling level with power draw and grinding rate. Then, an ML model using the Support Vector Machine (SVM) algorithm was developed to predict the angle of repose (AoR) and collision energy based on various operation conditions. The ML model was trained by the data generated from the DEM simulations and able to predict the AoR and collision energy. In the process monitoring, an artificial neural network (ANN) was firstly proposed to predict internal particle flow properties of a rotating mill based on acoustic emission (AE) signal generated using the DEM. Main features of AE signals and power draw were fed into the ANN to predict flow properties such as particle size distributions, collision energy distribution and filling levels. Further, a convolution neural network (CNN) was used to replace the ANN to extract more efficient features of AE signals non-linearly based on different local frequency ranges in a ball milling process partially filled with steel balls and grinding particles. Last, a physics-informed ML model was developed based on continuous convolution neural network (CCNN) to learn particle contact mechanisms provided by DEM data at different rotation speeds. The ML model coupled with DEM simulation can accelerate DEM simulation to accurately predict particle flow in a long time series. In summary, this work has demonstrated that combining physics-based numerical models DEM to ML models not only improves the efficiency and accuracy of predictions of complicated processes but also provides more insight to the process and makes predictions more transparent.
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(2023)ThesisClean chemical fuels such as molecular hydrogen are promising eco-friendly alternatives to CO2-emitting fossil fuels ; hydrogen can be generated using solar-driven photoelectrochemical water splitting with an efficient semiconductor photoelectrode. However, to optimize the process and reduce costs, exploring new materials and photoelectrode structures, as well as understanding their fundamental characteristics and impact on energy conversion, is crucial. Sulfide-based semiconductors such as CuS and ZnS have gained interest due to their earth abundance, non-toxicity, and suitable band gaps, but have limitations such as rapid recombination of photoexcited charge carriers and susceptibility to (photo)corrosion for CuS, and a wide band gap for ZnS. This thesis explores various approaches, such as varying synthesis conditions for the deposition of CuS thin films, forming CuS-ZnS mixtures, and doping, to improve the performance of both semiconductors. Firstly, CuxS thin films were synthesized using pulsed laser deposition. The deposition conditions such as substrate temperature and background gas pressure were varied to analyze their impact on structural and optoelectronic properties. Substrate temperature had a more significant effect on film growth than background gas pressure, and the highest temperature used (500°C) yielded the best performance with a reduced band gap and higher photocurrent density. However, poor stability was observed. To enhance the stability and overall performance of CuS, mixed films of CuS-ZnS were synthesized; they showed better optoelectronic properties and enhanced photoelectrode performance compared to films of CuS and ZnS on their own. Computational studies using DFT were also used to investigate the CuS-ZnS mixtures, which confirmed the enhanced charge separation as well as reduced band gaps compared to bulk CuS and ZnS. Altering the thickness of the ZnS layer also affected both stability and band gap, attributed to changes in interfacial bond lengths and atomic charges. From DFT calculations, it was found that doping CuS with transition metal and alkaline earth metal dopants affects the bonding behavior and can switch CuS between plasmonic and typical fluorescent semiconductor behavior. Overall, the thesis highlights the importance of exploring new materials and photoelectrode structures and understanding their fundamental characteristics to optimize the process of solar-driven water splitting and reduce costs.
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(2024)ThesisThe design of advanced hollow fibre ultrafiltration (UF) membrane technologies for use in wastewater treatment facilities has culminated from a combination of improvements in plant operation and optimising feed water interactions. With global demands in water quality increasing, this has placed increased pressure on MBR factories to develop high strength, anti-fouling fibre modules with improved permeabilities. The fabrication of such membranes, however, is restricted by the trade-off that exists between mechanical strength and filtration properties, as well as scalability concerns that arise when transitioning from laboratory trials to field testing of prototypes. This places increased importance on the need to establish a reliable formulation plan that addresses these trade-off limitations, in addition to furthering our understanding of membrane-foulant interactions. Modifications of polymer concentration will offer deeper insight into the role that polymer phase materials have on membrane formation and high strength performance. Further variations in pore-former content will provide a route towards optimising membrane surface porosity, translating into potential improvements in fibre permeability and anti-fouling propensity. Three different experimental approaches were implemented to assess the impact of fibre composition on membrane performance. These include (1) modifying the total concentration of poly(vinylidene fluoride) (PVDF) material, (2) tailoring the composition of PVDF material with distinct molecular weights, and (3) adjusting the proportion of poly(vinyl pyrrolidone) (PVP) and poly(ethylene glycol) (PEG) pore-forming additives. Microscopy techniques were used to document any structural changes across each formulation series, whilst porometer and tensile testing instruments were utilised to provide insight into membrane permeability and strength, respectively. Membranes formulated with elevated PVDF concentrations were found to exhibit improvements in mechanical integrity at the expense of reduced clean water fluxes. This was overcome by optimizing the incorporated PVDF molecular weight, which allowed for incremental boosts in toughness without adversely affecting permeability. Testing also revealed that fibres formed with higher concentrations of pore-forming agents, most notably PEG material, were found to be more permeable. Feedwater filtration cycling was implemented to provide insight into the relative fouling behaviour of membranes formed via these three approaches. Changes in resistance were found to be primarily dictated by membrane pore size, with intermediary pore size distributions being desirable targets for balancing out the effects of short- and long-term filtration. By tracing these trends in fouling propensity back to underlying fibre compositions, this study reinforces the importance of adjusting polymer formulations for achieving high strength, anti-fouling membranes. This study also acknowledges the limitations that exist in comparing laboratory-scale filtration data of fibre samples to prototype field testing of full-scale modules. Addressing these drawbacks through an analysis of feedwater conditions used in research and industry allows us to reach an informed decision on selecting appropriate formulations in the design of innovative membrane technologies.
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(2021)ThesisImprovements in liquid lithium-ion battery electrolytes using of metal organic frameworks (MOFs) as a functional decoration on polymer membrane separators were investigated using a combination of experimental and theoretical methods. Zirconium-based MOF UiO-66 was introduced to the polymer support using the mixed matrix membrane (MMM) method. The method allowed the one-step manufacture of a robust, mechanically pliable polymer-MOF membrane composite of high MOF loading. MOF-MMMs imparted improved electrochemical behaviours such as a widened potential operating window, near-unity transference number, and increased presence of solid electrolyte interphase (SEI) components crucial to battery performance. Density functional theory (DFT) calculations were also performed to provide insights regarding electrolyte solvation in the presence of MOF. A simple dip-coating technique was utilised to modify the surface of the MOF-MMMs with polydopamine (PDA) for further improvement of the electrochemical properties. Increased transference numbers, as well as stability during rate cycling, were observed with the resulting PDA-MMM owing to the improved electrode/electrolyte interface. However, surface analyses using x-ray photoelectron spectroscopy (XPS) showed that there are reduced amounts vital SEI components compared to the original MOF-MMM support. The last section further explores the versatility of UiO-66 and tackled the preparation of gel polymer electrolytes (GPEs) decorated with UiO-66 via phase inversion technique. Using the phase inversion method, the fabricated GPE contained pores from both polymer substrate and the intrinsic pores of the 3D nanomaterial for improvement of electrochemical properties. It was demonstrated in this work that the MOF GPE is equally inert and suitable in ether or carbonate-based electrolytes. Overall, this study demonstrated the versatility of UiO-66 metal organic frameworks for use as a functional nanofiller for electrolyte membranes. With the use of inexpensive membrane fabrication methods, the composites obtained are viable for lithium-metal battery applications. Similarly, insights drawn can provide a springboard towards future study of MOF-based electrolytes.
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(2023)ThesisLow melting point post-transition metals are a class of materials that melt below 330 ℃. Their low melting points offer distinctive physical and chemical properties that are yet to be fully explored. The study of properties of low melting point post-transition metals in various organic or inorganic systems enable insights into the field of biomaterials. The first stage of this thesis reports the synthesis of a liquid metal-polymer system which has the potential for patterning of liquid metals on different substrates. A sonication method is utilised for dispersion of eutectic mix of gallium and indium (EGaIn) particles into a photo-polymer. After characterisation of this inorganic-organic system, patterning of the dispersion is demonstrated through conductive tracks on flexible and rigid substrates. This method provides straightforward patterning of conductive EGaIn liquid metal traces. In the second stage, the physical, mechanical and biocompatibility properties of another liquid metal system known as Field’s metal (a eutectic mix of indium, tin and bismuth) was explored. Field’s metal (FM) has a melting point of 61 ℃. Two eutectic mixes of FM and FM-with zinc were synthesised and compared. A proof-of-concept application was demonstrated for the two biocompatible materials shaped into body implants for clinical applications. The removal of these implants from within a tissue mimic was demonstrated by utilising a mild non-contact heat source. This approach was shown to negate the need for invasive surgery for removal of implants from the body to potentially improving the health of patients. In the third stage, another liquid metal system was investigated based on gallium as the reaction media. Magnesium/bismuth intermetallic was formed on the surface of gallium through selective solidification. The intermetallic system, with a very high intrinsic melting point, formed at low temperature and hexagonal shaped domains of intermetallics on the surface were established. This inorganic system was then studied to show favourable antibacterial properties in comparison to pure gallium control. The work was a successful experimental demonstration on the possibility of the usage of liquid metal media for the formation of various mixes and intermetallic species in mild thermal conditions. Altogether, the outcomes of this successful PhD thesis will provide fundamental insights into surface chemistry of liquid metals with potential benefits in biomedical applications.