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(2023) Al Taief, KarrarThesisSelf-assembled short peptide hydrogels based on natural proteins have been designed to mimic natural environment of extracellular matrix (ECM) in tissue. Yet this class of hydrogels solely lacks the ability to represent the entire complexity of the ECM. To address this problem, requires novel design of synthetic materials incorporating natural biopolymers. In this work, library of peptides based on protein motifs were designed that form self-assembled hydrogel. Animal source or human source biopolymers were then mixed with these peptides to fabricate dual-functional hybrid hydrogels. The incorporation of biopolymers at a concentration much lower than the peptide concentration, drastically enhanced the mechanical property of these hybrid systems. Both animal and human biopolymers are commercially available at high cost, however, incorporating minimum concentrations of both into this novel hybrid hydrogel will reduce the need for the biopolymer in a cost-effective manner. Additionally, these hybrid hydrogel systems are readily tuned by designing or re-arranging the target peptides sequences to fulfil the required applications of these hydrogels. Another peptide carrying cell-adhesion epitope, was designed based on a key binding motif for skin cells. The peptide self-assembled into self-supporting hydrogel. While biological compatibility of this gelator with skin cells was suboptimal over a long period of time, on the other hand, in 2D cultures of human Mesenchymal Stem Cells (hMSCs) no adverse reactions were noted and the hMSCs were shown to spread over a 7 days period on top of the hydrogel formed. Remarkably, exposure of this peptide to light triggered dynamic assembly. This photo-induced modulation of peptide assembly could be harvested for future therapeutic applications.
(2023) Pappas, BillyThesisDevices which exploit the quantum properties of materials are widespread, with information processors and sensors showing significant recent progress. Organic materials offer interesting opportunities for quantum technologies owing to their engineerable spin properties, with spintronic operation and magnetic field sensing demonstrated in research grade devices, as well as proven compatibility with large scale fabrication techniques. Yet several important challenges remain as we move toward scaling these proof-of-principle quantum devices to larger integrated logic systems or spatially smaller sensing elements – particularly those associated with the variation of spin properties both within and between devices. In this thesis, we explore three aspects influencing the homogeneity of spin interactions experienced by excitations in their local molecular environments – spatial, temporal and energetic variations. The resolution of these variations is realised through magneto-optical spin spectroscopy, whereby the modulation of optoelectronic processes in organic light-emitting diodes are imaged under the application of external magnetic fields. Using this technique, we map the spatiotemporal and energetic distributions of important spin quantum properties common to many molecular compounds, the results of which highlight the challenges of miniaturising and integrating these technologies for sensing and logic-based applications. In addition to characterising the variability of hyperfine interactions across the microscopic molecular landscape, we observe the spatial correlation of this property for lengths up to 7 micrometres in both a polymer and small molecule material, and dynamic at room temperature. The energy dependence of exchange interaction strengths were also resolved in thermally activated delayed fluorescence materials, with variabilities exceeding 50% and which should be accounted for in future design rules of high performance fluorescent molecules. Our investigations into the variation and correlation of spin interactions in space, time and energy provide important characterisations of the spin properties possessed by molecular materials for use in quantum devices. The miniaturisation, integration and scaling of technologies employing these materials will have to contend with this variation.
(2023) Lam, NgaThesisThe self-assembly of proteins into intricate high-order structures can be harnessed for the precise positioning of functional molecules in nanotechnology. The organisation of enzymes on protein scaffolds has been previously shown to enhance enzyme catalytic activity. Additionally, the alignment of metal-binding proteins, known as metalloproteins, on filamentous proteins has been exploited to produce electrically conductive nanowires. The focus of this thesis is on the development of improved biosynthetic strategies for the creation of multifunctional nanomaterials by harnessing the self-assembly of filamentous proteins. Central to the engineering in this thesis is prefoldin, which is a molecular chaperone from archaea with the ability to self-assemble into hetero-hexameric complexes and filamentous structures. Prefoldin proteins exhibits high thermal stability and have engineerable interfaces for bioconjugation of functional proteins. Therefore, the research goal of this thesis was to engineer robust and modular protein scaffolds for the precise position of enzymes and alignment of electrically conductive subunits to create biocatalysis and bioelectronic systems. The first aim of the research was to construct a protein scaffold from a hexameric self-assembling protein and immobilise enzymes on the protein scaffold to examine for enhanced sequential catalytic reactions. The second aim explored the capability of prefoldin filaments to align various metalloproteins in proximity over large distances for electron transfer. Distinct metalloproteins were exploited to create nanowires with various electronic properties for applications in bioelectronic devices. The third aim developed a strategy to localise redox enzymes at either end of the metalloprotein nanowires and potentially demonstrate energy transfer along the nanowire between enzymes undergoing redox reactions. The successful achievement of these aims establishes a biostrategy to use a controllable and modular prefoldin protein scaffold for the fabrication of biocatalysis and bioelectronic devices.