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<p>Aggregation of the<strong> </strong>Alzheimer’s Aβ peptide in the brain and blood plasma is controlled by endogenous Aβ binding proteins. The structural basis for the interaction between the Aβ peptide and the Aβ binding proteins is critical not only to understand how Aβ amyloids are controlled in vivo, but also to guide the design of novel Aβ-self association inhibitors. However, the current knowledge of the structures of the Aβ/Aβ binding protein complexes is still sparse. This thesis focuses mainly on the interaction of the Aβ peptide with Human Serum Albumin (HSA). It is known that HSA binds ~90% of the Aβ in human plasma and prevents the Aβ self-association into amyloid fibrils. However, the mechanism of Aβ self-association inhibition by albumin was not understood prior to our work. We have shown that albumin preferentially binds toxic Aβ oligomers and fibrils inhibiting their growth into larger Aβ assemblies through a “monomer competitor” mechanism. Using a combination of NMR, domain deletion mutants, dynamic light scattering and ultrafiltration we have investigated the stoichiomery and affinity of the Aβ oligomer: HSA complexes. Our results indicate that all three domains of HSA bind Aβ oligomers and fibrils with an affinity in the 1-100 nM range. Such binding site degeneracy explains how albumin minimizes competition by other ligands such as fatty acids and drugs. Moreover we have used the soluble and NMR suitable domain 3 of albumin to dissect further the determinants of the Aβ oligomer binding to albumin at subdomain and peptide resolution. We show that both subdomains of the HSA domain 3 (<em>i.e</em>. 3A and 3B) bind the Aβ oligomers. In addition, we identified a peptide sequence within subdomain 3B that displays significant potency in the inhibition of Aβ self-association.</p> / Doctor of Philosophy (PhD)

Fouling properties of materials such as polyethylene glycol (PEG) have been extensively studied over the past decades. Traditionally, the factors believed to result in protein adsorption resistance have included i) steric exclusion arising from the compression of longer chains and ii) grafting density contribution which may provide shielding from the underlying material. Recent studies have suggested that PEG interaction with water may also play a role in its ability to resist protein adsorption suggesting that steric exclusion may not be the only mechanism occurring during PEG/protein interactions. Star-shaped PEG polymers have been utilized in protein adsorption studies due to their high PEG segment concentration, which allows to increase the PEG chain grafting density compared to that achieved with linear PEG chains. Most studies that have investigated the interactions of tethered linear and star-shaped PEG layers with proteins have considered linear PEG molecules with molecular weights several orders of magnitude smaller than those considered for star-shaped PEG molecules (i.e. 10 000 g/mol vs. 200 000 g/mol, respectively). Additionally, the star-shaped PEG molecules which have been considered in the literature had up to ~70 arms and were therefore modeled by hard-sphere like structures and low chain densities near the surface due to steric hindrance. This resulted in some difficulties to achieve grafted PEG chain overlap for star molecules. Here, triethoxysilane end-functionalized linear PEG molecules have been synthesized and utilized to form star-shaped PEG derivatives based on ethoxy hydrolysis and condensation reactions. This resulted in PEG stars with up to ~4 arms, which were found to result in grafted star-shaped PEG chains with significant chain overlap. Linear PEG derivatives were synthesized so that their molecular weight would match the overall molecular weight of the star-shaped PEG molecules. These 2 PEG molecular architectures were covalently self-assembled to hydroxylated silicon wafers and the thickness, grafting density, and conformation of these films were studied. The adsorption of human albumin (serum protein) on linear and star-shaped PEG films was compared to that obtained on control samples, i.e. uncoated silicon wafers. Both film architectures were found to significantly lower albumin adsorption. / Ph. D.

The emergence of microneedle (MN) technologies offers a route for a pain free, straightforward and efficient way of transdermal drug delivery, but technological barriers still exist which pose significant challenges for manufacture of MN systems with high volume outputs at low cost. The main aim of this research was to develop new ways for MN manufacture primarily using micro-injection moulding processes with high performance engineering thermoplastics. During the moulding process these polymeric melts will be subjected to extreme stress and temperature gradients and detailed material characterisation combined with in-line monitoring is desirable to optimise the moulding parameters and will help in achieving sharp microneedles with acceptable quality. Hence high shear rheology of these selected materials was performed at wall shear rates carried out in excess of 107 s-1 over a range of temperatures to predict the flow behaviour of polymer melts at such high shear strain rates. This information was fed into injection moulding simulation software tools (Moldflow) to assist the MN production process design. The optimal design was then used to produce a full 3D solid model of the injection mould and mould insert. Furthermore various design of experiments were conducted considering input parameters such as injection pressure, injection speed, melt temperature, filling time and mould cavity temperature. Response variables including product quality and data acquired from the cavity pressure and temperature transducers were used to optimise the manufacturing process. The moulded MNs were geometrically assessed using a range of characterisation techniques such as atomic force microscopy, confocal microscopy and scanning electron microscopy. An attempt to make hollow MNs was performed and encountered many challenges like partial cavity filling and part ejection during processing. Studies were carried out to understand the problem and identified the major problem was in tool design and improvements to the moulding tool design were recommended. Plasma treatment and mechanical abrasion were employed to increase the surface energy of the moulded polymer surfaces with the aim of enhancing protein adsorption. Sample surface structures before and after treatment were studied using AFM and surface energies have been obtained using contact angle measurement and calculated using Owens-Wendt theory. Adsorption performance of bovine serum albumin and release kinetics for each sample set was assessed using a Franz diffusion cell. Results indicate that plasma treatment significantly increases the surface energy and roughness resulting in better adsorption and release of BSA. To assist design-optimisation and to assess performance, a greater understanding of MN penetration behaviour is required. Contact stiffness, failure strength and creep behaviour were measured during compression tests of MN against a steel surface, and in-vitro penetration of MNs into porcine skin. The MN penetration process into porcine skin was imaged using optical coherence tomography. Finally, a finite element model of skin was established to understand the effect of tip geometry on penetration. The output of findings from this research will provide proof of concept level development and understanding of mechanisms of MN penetration and failure, facilitating design improvements for micro-injection moulded polymeric MNs.

<p dir="ltr">In the three conducted studies, we investigated the role of serum albumin in metabolic processes, particularly in lipid metabolism and glucoregulation. The first study explored how disrupting the binding of free fatty acids (FFA) to circulating albumin affects lipid metabolism and glucose control. Male and female albumin knockout mice exhibited significantly reduced plasma FFA levels, hepatic lipid content, and blood glucose during tolerance tests compared to wild-type mice. Additionally, albumin deficiency led to changes in adipose tissue gene expression, indicating the importance of albumin and plasma FFA concentration in metabolic regulation. In the second study, the focus was on determining if impeding serum albumin's function in transporting FFAs could prevent hepatic steatosis and metabolic dysfunction in obesity. Albumin knockout mice, despite being obese due to a high-fat diet, showed lower plasma FFA levels, improved glucose tolerance, and reduced hepatic lipid accumulation compared to wild-type mice. Elevated gene expression in liver and adipose tissues suggested albumin's involvement in hepatic lipid accumulation and glucose metabolism in obesity. Lastly, in the third study, we examined the phenotype of heterozygous albumin knockout mice and compared it to wild-type and homozygous knockout mice. While homozygous knockout mice exhibited improved glucoregulation and reduced plasma FFA concentration, heterozygous knockout mice did not show significant improvements compared to wild-type mice. The findings imply that a minor suppression of albumin expression may not be adequate to enhance glucoregulation. In summary, the studies emphasize the crucial role of serum albumin in metabolic processes, illustrating how disrupting FFA binding to albumin leads to improved glucose control and reduced hepatic lipid accumulation. However, minor suppression of albumin expression may not effectively enhance metabolic health. These findings provide valuable insights into potential therapeutic interventions targeting the albumin-FFA pathway to improve metabolic outcomes.</p><p dir="ltr"><br></p>

Yes / Plasma technology has been widely used to increase the surface energy of the polymer surfaces for many industrial applications; in particular to increase in wettability. The present work was carried out to investigate how surface modification using plasma treatment modifies the surface energy of micro-injection moulded microneedles and its influence on drug delivery. Microneedles of polyether ether ketone and polycarbonate and have been manufactured using micro-injection moulding and samples from each production batch have been subsequently subjected to a range of plasma treatment. These samples were coated with bovine serum albumin to study the protein adsorption on these treated polymer surfaces. Sample surfaces structures, before and after treatment, were studied using atomic force microscope and surface energies have been obtained using contact angle measurement and calculated using the Owens-Wendt theory. Adsorption performance of bovine serum albumin and release kinetics for each sample set was assessed using a Franz diffusion cell. Results indicate that plasma treatment significantly increases the surface energy and roughness of the microneedles resulting in better adsorption and release of BSA.

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