Medicine & Health

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Now showing 1 - 10 of 10
  • (2022) Cao, Jun
    Thesis
    This thesis focuses on the development and applications of magnetic resonance electrical properties tomography (MREPT), which is an emerging imaging modality to noninvasively obtain the electrical properties of tissues, such as conductivity and permittivity. Chapter 2 describes the general information about human research ethics, MRI scanner, MR sequence and the method of phase-based MREPT implemented in this thesis. Chapter 3 examines the repeatability of phase-based MREPT in the brain conductivity measurement using balanced fast field echo (bFFE) and turbo spin echo (TSE) sequences, and investigate the effects of compressed SENSE, whole-head B_1 shimming and video watching during scan on the measurement precision. Chapter 4 investigates the conductivity signal in response to short-duration visual stimulus, compares the signal and functional activation pathway with that of BOLD, and tests the consistency of functional conductivity imaging (funCI) with visual stimulation across participants. Chapter 5 extends the use of functional conductivity imaging to somatosensory stimulation and trigeminal nerve stimulation to evaluate the consistency of functional conductivity activation across different types of stimuli. In addition, visual adaptation experiment is performed to test if the repetition suppression effect can be observed using funCI. Chapter 6 explores if resting state conductivity networks can be reliably constructed using resting state funCI, evaluates the consistency of persistent homology architectures, and compares the links between nodes in the whole brain. Chapter 7 investigates the feasibility of prostate conductivity imaging using MREPT, and distinctive features in the conductivity distribution between healthy participants and participants with suspected abnormalities.

  • (2022) Yu, Tsz Tin
    Thesis
    The rapid emergence and development of antibacterial resistance is a major global threat to public health. There is an urgent need for the development of antibacterial agents with novel therapeutic strategy to tackle the increasing incidence of antibacterial resistance. In recent years, antimicrobial peptides (AMPs) and their synthetic mimics have been under the spotlight of the development of a novel class of antibiotics to combat antibiotic resistance. This research project focused on the utilisation of phenylglyoxamide and benzothiazole scaffolds in the development of antimicrobial peptidomimetics. The synthesis of phenylglyoxamide-based peptidomimetics was achieved via the ring-opening reactions of N-sulfonylisatins with primary amines followed by salt formation. Minimum inhibitory concentrations (MIC) of the peptidomimetics against different bacterial strains were determined to assess their antibacterial activity. Structure-activity relationship (SAR) studies revealed the inverse relationship between the alkylsulfonyl chain length and the bulkiness of the phenyl ring system for high antibacterial activity. The most active peptidomimetics exhibited high antibacterial activity with the lowest MIC to be 4, 16 and 63 μM against S. aureus, E. coli and P. aeruginosa, respectively. These peptidomimetics also showed significant biofilm disruption (up to 50%) and inhibition (up to 70%) against S. aureus at 2–4× MIC. In addition, terphenylglyoxamide-based peptidomimetics synthesised by the ring-opening reaction of N-acylisatins with amines and amino acid esters were evaluated for their quorum sensing inhibition (QSI) activity against P. aeruginosa MH602. The most potent peptidomimetic possessed high QSI activity of 82%, 65% and 53% at 250, 125 and 62.5 μM, respectively, with no bacterial growth inhibition. On the other hand, benzothiazole-based peptidomimetics were synthesised via the Jacobson method of cyclisation of phenylthioamides, followed by the installation of cationic groups. 2-Naphthyl and guanidinium hydrochloride as the hydrophobic and cationic groups, respectively, were important for high antibacterial activity of the peptidomimetics against both Gram-positive and Gram-negative bacteria. The most potent peptidomimetics against S. aureus, E. coli and P. aeruginosa possessed MIC values of 2, 16 and 32 μM, respectively. These active peptidomimetics inhibited 39% of S. aureus biofilm formation and disrupted 42% of preformed S. aureus biofilms at sub-MIC.

  • (2022) Sanchez Miranda, Marta
    Thesis
    The aim of this thesis is the development of microscopy-compatible electronic devices to advance the field of biosensing in two main directions. First, the development of a platform that allows electrical and optical studies of membrane proteins at the single molecule level. We have fabricated InAs nanowire field-effect transistors and PEDOT:PSS organic electrochemical-transistors on 170 μm thick glass slides for their integration with fluorescence microscopes. Each electronic device was fabricated at the bottom of a circular well sealed with a lipid bilayer. A wide range of membrane proteins can be inserted into this lipid bilayer, most of which work as pores or active pumps for the transport of ions across the membrane. This platform allows simultaneous electrical and optical studies of such proteins, achieving single-molecule resolution when a single protein is inserted in the bilayer. We present the fabrication procedures for these devices and the creation of a lipid membrane over them, as well as electrical characterization and ion sensitivity measurements. The development of novel hardware to achieve electrical contact with the devices while performing fluorescence microscopy is also presented. We demonstrate the viability of our platform via the correlation of electrical and optical signals in response to ion concentration and lipid bilayer rupture. We also present a computational model that provides insight into this system and propose future optimization steps towards the incorporation of membrane proteins into the system. Second, the creation of a sensor that allows electrical detection of a moving target at the single molecule level. In this thesis, we present a theoretical model to determine the feasibility of detecting an actin filament or microtubule passing in close proximity to a carbon nanotube field-effect transistor. This platform would allow the detection of moving biomolecules without the need to physically attach the molecules to the electronic devices. Our results showed that electrical detection is possible given the right experimental conditions. This would enable tracking of large numbers of molecules at once, an important advance for applications where the detection of biological agents is relevant, such as biocomputation.

  • (2022) Gadde, Satyanarayana
    Thesis
    High-risk neuroblastoma is one of the most aggressive and treatment-refractory childhood malignancies. MYCN (v-myc avian myelocytomatosis viral related oncogene, neuroblastoma derived) is a major oncogenic driver for neuroblastoma (NB) tumorigenesis. Developing direct inhibitors of MYCN has been challenging due to several limitations. Hence, targeting MYCN-binding proteins which regulate the stability of MYCN protein is a promising alternative approach. This study is aimed at developing novel inhibitors of ubiquitin specific protease 5 (USP5), a deubiquitinating enzyme, which is known to prevent MYCN protein degradation by deubiquitination. The first results chapter describes the synthesis of novel pyrido[1,2-a]benzimidazole compounds and their cytotoxicity against MYCN amplified NB cells with high expression of USP5 protein (SK-N-BE(2)-C and Kelly cells). However, none of the tested compounds displayed better cytotoxicity than the parental compound, SE486-11. The second results chapter describes a one-pot synthesis of novel γ-carbolinone, γ-carboline and spiro[pyrrolidinone-3,3′]indoles. One of the γ-carboline compounds (42d) displayed promising cytotoxicity against NB cells (SK-N-BE(2)-C (IC50 = 1.21 μM) and Kelly (IC50 = 3.09 μM)) but showed little therapeutic selectivity when compared to normal human fibroblasts, MRC-5 cells (IC50 = 3.75μM). The synthesis and cytotoxicity of novel pyrimido[1,2-a]benzimidazoles is described in the third results chapter. The active compound, 65a displayed promising cytotoxicity against SK-N-BE(2)-C (IC50 = 0.78 μM) and Kelly (IC50 = 2.00 μM) cells with a reasonable therapeutic window compared to MRC-5 cells (IC50 = 15.0 μM). 65a bound to USP5 protein by microscale thermophoresis assay (Kd = 0.47 µM). USP5 and MYCN protein levels were decreased in NB cells by treatment with 65a. Moreover, the cytotoxicity of 65a was dependant on the expression of USP5 and MYCN proteins. 65a showed synergy in combination with HDAC inhibitors, SAHA and panobinostat. In the fourth results chapter, the synthesis of more potent pyrimido[1,2-a]benzimidazoles with di- and tri- substitutions on the pendant phenyl ring (86b (SK-N-BE(2)-C IC50 = 0.31 μM; Kelly IC50 = 0.65 μM) and 91 (SK-N-BE(2)-C IC50 = 0.03 μM; Kelly IC50 = 0.07 μM)) are described. Importantly, 86b displayed significant in vivo efficacy in TH-MYCN homozygous NB mice when treated with 60 mg/kg for three weeks. The last results chapter describes the synthesis and cytotoxicity of novel benzo[4,5]imidazo[2,1-b]thiazole and pyrido[2,3-b]indole compounds. Collectively, this thesis identifies promising novel scaffolds with great potential for further development.

  • (2022) Bello, Idris
    Thesis
    The inflammatory artery diseases atherosclerosis and abdominal aortic aneurysm (AAA) are major causes of morbidity and mortality and there is significant attention towards identifying and targeting prominent inflammatory mediators underpinning these cardiovascular diseases. In the first chapter, the role of the pro-inflammatory and pro-oxidant enzyme myeloperoxidase (MPO) in inflammatory artery disease was studied. A clinical study showed that while circulating plasma MPO levels were not different in AAA patients versus healthy controls, immunohistochemistry showed that the MPO protein was prevalent in human AAA tissue. In the angiotensin II (AngII)-infusion model of AAA and atherosclerosis in apolipoprotein-E gene-deficient (ApoE–/–) mice, administration of 2-thioxanthines (2-TX), a clinically-trialled MPO inhibitor, significantly inhibited AAA but not atherosclerosis. Paradoxically, MPO gene-deficiency did not affect AngII-induced AAA but attenuated atherosclerosis. Notably, 2-TX significantly inhibited AAA in ApoE–/–MPO–/– mice, indicating 2-TX protects against aortic disease in the absence of MPO. The role of MPO in the diabetes-accelerated atherosclerosis in ApoE–/– mice was also examined. While MPO gene-deficiency did not impact on the degree of diabetes it significantly reduced diabetes-accelerated atherosclerosis at the brachiocephalic artery and aortic sinus, but not aortic arch, indicating that MPO exhibits site-specific effect on atherosclerosis. A second chapter focused on semicarbizide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1), a pro-inflammatory enzyme that facilitates the vascular recruitment of activated leukocytes. Treatment of AngII-infused ApoE–/– mice with a clinically-viable SSAO/VAP-1 inhibitor significantly protected against AAA and atherosclerosis, independent of alterations to plasma lipid levels. A third chapter tested the therapeutic efficacy of apolipoprotein A-I (ApoA-I), the major cardioprotective protein in high-density lipoproteins, and a class of immunomodulatory nanoparticles (INPs), which selectively target and disable a pro-inflammatory monocyte subset. Although ApoA-I treatment did not impact on the development of arterial disease in AngII-infused, aged ApoE–/– mice, INPs provided significant protection against AAA and atherosclerosis in these mice. This novel research provides new insights on the roles of MPO and SSAO in AAA and atherosclerosis and identified clinically-viable inhibitors of MPO and SSAO and a class of biodegradable immunomodulatory nanoparticles as potential new therapeutics for treating inflammatory artery disease.

  • (2023) Paul, Kishor Kumar
    Thesis
    The transmission of dengue fever is already being impacted by the changing climate. This phenomenon poses a considerable public health challenge for countries like Bangladesh, where regular seasonal outbreaks of dengue fever are already prevalent. This thesis aims to investigate how changing climate will impact long-term dengue epidemiology in Bangladesh as a whole and more specifically in Dhaka, the capital city of the country over the 21st Century. Several statistical models have been developed to estimate the short-term risk of dengue outbreaks as a function of climate variables but the underlying causal relationships that contribute to dengue transmission and the observed patterns of dengue epidemiology are not accounted for in these models. Initially, we determined the suitability of using climate projections for 21st Century from Global Climate Models (GCM) to assess the impact of changing climate on future dengue risk in Bangladesh setting. We then used the GCM output to assess the impact of changing climate on one aspect of dengue transmission by calculating the change in vectorial capacity (VC) of Aedes aegypti mosquitoes at a seasonal level for all regions in Bangladesh under two future climate change scenarios. The analysis indicates that the annual VC in all divisions of Bangladesh is expected to consistently exceed the threshold for dengue transmission throughout the 21st Century, regardless of the climate change scenarios considered. However, during the latter half of the century, there is a projected decline in the annual VC compared to the period between 1986 and 2005. Despite this, monthly VC variations reveal that the winter/dry season could see an increase in VC, potentially leading to a longer dengue season with outbreaks occurring year-round. The application of the VC calculation is limited by the fact that it only accounts for temperature and does not consider the impact of other climate variables such as rainfall and humidity, as well as the role of host immunity. To incorporate these factors, we then developed a mechanistic dengue transmission model that considers the influence of temperature, rainfall, and humidity on the transmission of two different dengue serotypes among human hosts and mosquito vectors. We calibrated and validated the model against observed dengue epidemiology data from Dhaka for 1995-2014 using observed climate data as input. We then used GCM output for two future climate change scenarios to simulate the model for two future periods (2030-2049 and 2080-2099) to assess the potential changes in dengue epidemiology in Dhaka. When utilizing observed climate data and climate projections from GCMs specific to Dhaka, our mechanistic model reasonably reproduced the observed dengue epidemiology in Dhaka between 1995 and 2014 in terms of the recurring annual dengue outbreaks, the seasonal pattern of transmission, and the increase in seroprevalence. Simulations for 2030-2049 indicate that dengue transmission is likely to increase regardless of the combination of initial seroprevalence, GCM, and climate change scenario, when compared to the baseline period of 1995-2014. However, for the period 2080-2099, the projected changes in dengue transmission vary, with some combinations of initial seroprevalence, GCM, and climate change scenario predicting a slight increase and others indicating a decrease. The simulations also suggest the seasonal pattern of dengue infections is likely to change in future, with more pronounced change projected for the 2080-2099 period, resulting in a lengthening of the dengue season. The primary contribution of this thesis is to present a modelling framework that considers the anticipated changes in the future climate and immunological factors to project the long-term risk of dengue epidemics. The model is flexible enough to be adapted to other settings and other pathogens transmitted by the same mosquito vector.

  • (2023) Chakraborty, Sudip
    Thesis
    Orthopaedic devices and biomaterials have significantly improved the livelihood of patients suffering from debilitating health conditions and have offered healthcare institutions and governments the tools to intervene for better health outcomes. However, like with many other life-saving technologies, there are challenges hindering the optimal effectiveness of orthopaedic biomaterials, key amongst which is bacterial infections. These infections often result in multiple surgeries and implant failure. Traditional therapeutic strategies that have relied on antibiotics are being challenged by the rapid evolution and prevalence of antibiotic resistant bacteria. Therefore, exploring alternative strategies to kill bacteria and reduce medical devices associated infections is the need of the hour. Traditional antibiotics are susceptible to bacterial resistance primarily because of their mechanisms of action which involve identifying and binding to specific targets within bacteria. Alternatives to traditional antibiotics such as antimicrobial peptides and their mimics, quaternary ammonium compounds, antibacterial hydrogels, metal ions, etc., have emerged as potent antibacterial agents, some of which are less susceptible to bacterial resistance due to their non-specific modes of action. In the context of biomedical devices and implants, the attachment strategies employed for tethering antimicrobial compounds to their surfaces play crucial roles in determining the magnitude of antibacterial activity observed on the device surfaces and in the surrounding region. Plasma Immersion Ion Implantation and Deposition (PIIID) has emerged as an exciting single-step process for attaching molecules to material surfaces. It is relatively easy to perform and successfully generates stable coatings for materials. In this, study, we have explored two small-molecule antimicrobial peptidomimetics, an antimicrobial polymer, two antimicrobial peptides, a quaternary ammonium polymer, and an vi antimicrobial hydrogel as coatings and fillings for hydroxyapatite (HA) and polyether ether ketone (PEEK) surfaces. We have explored two strategies for attachment of these compounds to the materials, physical attachment via weak interactions and covalent attachment via PIIID treatment. Chapters 2 and 3 describe the attachment and properties of the peptidomimetics-based coatings for HA surfaces while chapter 4 details the properties of the polymer-based coatings for the same. Chapter 5 deals with the two antimicrobial peptides and chapter 6 talks about the quaternary ammonium polymer-based coating and the antimicrobial hydrogel-based filling for HA discs. Finally, chapter 7 describes the properties of peptidomimetics and polymer-coated PEEK sheets. Overall, several non-traditional strategies for generating antibacterial coatings for materials of relevance in orthopaedics were investigated. All the compounds demonstrated excellent antibacterial activity and were successful in inhibiting the attachment of bacteria (S. aureus (peptidomimetics, peptides, quaternary ammonium polymer and hydrogel), E. coli (polymer, peptides, and hydrogels) and P. aeruginosa (peptides)) to the material surfaces and in the surrounding solution. The covalently coated surfaces could retain their activity over a prolonged period of time while the physically coated surfaces exhibited significant activity immediately after the coating. These compounds and attachment strategies represent exciting alternatives to traditional therapeutic strategies.

  • (2023) Seyed Tajaddini, Aynaz
    Thesis
    Much evidence indicates that maternal obesity programs a range of complications in offspring, highlighting the need to identify beneficial interventions. The present thesis examined if the programmed effects of maternal obesity on offspring are exacerbated by exposure to a high-fat, high-sugar ‘Cafeteria’ (Caf) diet and investigated the effects of a healthy diet intervention in adulthood. The first study examined whether a diet switch intervention could reverse the adverse effects of an unhealthy postweaning diet in male and female rat offspring born to dams fed standard chow or a high-fat, high-sugar, Caf diet. Weanling offspring from Caf dams were smaller and lighter, yet had more retroperitoneal (RP) fat, particularly in males. Maternal obesity enhanced the impact of postweaning Caf exposure on adult (14-week-old) body weight, RP fat, liver mass and plasma leptin in males but not females. Maternal Caf diet significantly increased relative expression of ACACA and Fasn in male and female weanling liver, whereas PPARα was increased in males from Caf dams. Hepatic CPT-1 expression was reduced in adult males from Caf fed dams. The results underline the sex-specific detrimental effects of maternal obesity on offspring; maternal obesity exacerbated the obesogenic phenotype produced by postweaning Caf diet in male, but not female offspring. A subset of rats from this first cohort were maintained on their postweaning diets until 22 weeks of age, when postweaning Caf groups were switched to chow for a further 5 weeks. Switching from Caf to chow in adulthood suppressed energy intake below groups maintained on chow. Consequently, body weight and adiposity fell in switched groups, but remained significantly higher than chow-fed controls. The diet switch improved a deficit in place recognition memory observed in Caf-fed groups, with no significant change over time in chow-fed groups. Importantly, the effects of the switch did not differ between offspring born to chow or Caf-fed dams. Thus, in these older adult offspring a healthy dietary intervention led to benefits regardless of prior exposure to maternal obesity. To complement these data, our second study investigated if the programming effects of maternal obesity were aggravated by offspring exposure to a Caf diet when introduced in adulthood. Male and female offspring from lean and obese dams were weaned onto chow until 9 weeks of age; siblings were then either continued on chow or switched to Caf diet for 5 weeks. Offspring from Caf dams were smaller than those from chow dams at birth, and exhibited greater adiposity, plasma glucose and leptin levels at weaning in both sexes. Offspring of Caf dams exhibited elevated liver triglyceride content at weaning but no significant changes in the liver antioxidant enzymes GPx, SOD, and CAT. The switch to Caf diet elevated body weight and fat mass, with more pronounced effects in females than males. As in our first study, adult males (14 week old) from Caf-fed dams exhibited increased body weight, adiposity, and plasma insulin and leptin levels relative to offspring from chow dams. In female offspring, only RP fat mass and plasma insulin were increased by maternal obesity. Moreover, there were behavioural effect of maternal obesity (reduced anxiety-like behaviour) on offspring. Thus, the effects of maternal Caf diet exposure were absent until a cafeteria diet challenge in adulthood, indicating that Caf diet-induced maternal obesity programs a latent vulnerability to obesogenic diet exposure in offspring, particularly in males. Further studies are needed to investigate the beneficial effects of reprogramming strategies such as healthy diet intervention in offspring, which are likely to be influenced by the duration, timing and mode of intervention.

  • (2023) Listiyandini, Ratih Arruum
    Thesis
    Psychological distress is prevalent among university students worldwide, including in Low-and-middle income countries, such as Indonesia. Considering its promising scalability, a culturally relevant Internet-delivered mindfulness intervention has potential to treat psychological distress among Indonesian university students. However, there is no previous research into the development and impact of culturally relevant internet-delivered mindfulness interventions for Indonesian university students, leaving a gap in the research literature. The current thesis aims to: a) develop a culturally adapted internet-delivered mindfulness intervention and evaluate its relevancy for Indonesian university students; b) assess its feasibility and acceptability in a pilot open trial, and c) investigate its effectiveness for treating distress among Indonesian students in a randomised controlled trial. To achieve the thesis objectives, the systematic cultural adaptation framework proposed by Barrera and colleagues (2006; 2013) was employed as a guiding framework for culturally adapting an Australian internet-delivered mindfulness program to be more relevant for Indonesian university students. The development of a culturally adapted internet-delivered mindfulness intervention was achieved through two studies using mixed-methods approach. Study 1 was an online cross-sectional survey of Indonesian students’ openness and preferences toward an internet-delivered mindfulness program. Study 2 engaged Indonesian university students, as well as mindfulness or mental health experts in focus group discussions, structured interviews, and the completion of cultural relevancy questionnaires. The purpose of Study 2 was to gain feedback on an initial version of the culturally adapted program. These studies showed that an internet-delivered mindfulness intervention is relevant for Indonesian university students, but some adjustments needed to be made to enhance its cultural suitability and engagement. Based on these studies, an Indonesian counsellor-guided internet-delivered mindfulness program, called PSIDAMAI (Program Intervensi Mindfulness Daring Mahasiswa Indonesia) was developed. Subsequently, Study 3 assessed the feasibility, acceptability, and preliminary clinical outcomes of counsellor guided PSIDAMAI using a pre-post open trial study design. Study 3 showed that PSIDAMAI was feasible, acceptable, and associated with significant improvements in psychological distress between baseline and post-treatment, with good completion rates (70%). In Study 4, the clinical efficacy of PSIDAMAI was tested in a randomized controlled trial using a wait-list control group as a comparator. Study 4 found that PSIDAMAI was more effective at improving psychological distress compared to the wait-list control group with medium to large between-group effect sizes. The improvements were maintained up to one-month follow-up. In summary, the thesis is the first to demonstrate evidence that a culturally adapted internet-delivered mindfulness intervention is relevant, acceptable, feasible, effective, and has positive impacts for Indonesian university students’ mental health. Thus, strategies for wider implementation within the Indonesian higher education mental health system are now needed.

  • (2024) Rouaen, Jourdin
    Thesis
    Anti-GD2 immunotherapy has significantly enhanced survival of high-risk neuroblastoma patients however efficacy is strongly hampered by the immunosuppressive tumour microenvironment. Given the emerging link between copper and immune evasion, we assessed the impact of copper chelation therapy on neuroblastoma using the agents tetraethylenepentamine (TEPA) and the clinically approved analogue triethylenetetramine (TETA; marketed as Cuprior®). Using the preclinical TH-MYCN model, we performed single-cell RNA sequencing supported by OPAL multiplex immunohistochemistry and cytokine profiling to assess cellular and molecular changes occurring with TEPA treatment in the neuroblastoma tumour microenvironment. Copper chelation was observed to successfully deplete intratumoural copper to reinvigorate anti-tumour immunity as signalled by increased infiltration and activity of pro-inflammatory immune cells, specifically N1 neutrophils. Mechanistic in vitro assays reveal sequestration of copper by neuroblastoma cells causing dysregulated neutrophil function, with successful reversal upon TEPA treatment. Findings propose a novel mechanism of immune evasion, highlighting copper chelation as a therapeutic strategy to counteract immunosuppression. Copper chelation is further shown to increase GD2 expression, while also enhancing neutrophil antibody-dependent cellular cytotoxicity in vitro. Using the TH-MYCN model, TEPA was found to potentiate anti-GD2 therapy to achieve durable tumour control. This was associated with increased Fc-receptor-bearing natural killer and CD11B+ myeloid cells capable of performing antibody-dependent cellular cytotoxicity. Finally, we evaluated TETA for repurposing as a novel immunomodulatory agent. Comparative in vitro studies with TEPA confirm the ability of TETA to deplete intratumoural copper and downregulate immune checkpoint proteins Programmed Death-Ligand 1 (PD-L1) and indoleamine-pyrrole 2,3-dioxygenase (IDO). Using the preclinical NXS2 model, TETA exhibited an exceptional safety profile without altering copper levels or GD2 expression in healthy nerve tissue. Combination with anti-GD2 therapy achieved durable tumour control with no relapses occurring after treatment cessation and was similarly associated with infiltration of pro-inflammatory immune cells. Collectively, study findings credential copper chelation as a non-toxic strategy to overcome the immunosuppressive tumour microenvironment and improve neuroblastoma patient outcomes.