Doctoral Degrees (Molecular Biology and Human Genetics)
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Browsing Doctoral Degrees (Molecular Biology and Human Genetics) by browse.metadata.advisor "Allie, Nasiema"
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- ItemAntimycobacterial activity of ascidian fungal symbionts(Stellenbosch : Stellenbosch University, 2022-12) Tapfuma, Kudzanai Ian; Mavumengwana, Vuyo; Malgas-Enus, Rehana; Loxton, Andre Gerhard; Allie, Nasiema; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.ENGLISH ABSTRACT: Tuberculosis (TB) is an infectious disease which primarily affects the lungs. Treatment of TB is complicated because the causative agent, Mycobacterium tuberculosis, is an intracellular pathogen which infects and kills cells of the innate immune system, while exhibiting intrinsic and extrinsic resistance to many of the currently available antimicrobial agents. A sizeable percentage of TB patients in the world-population are infected by M. tuberculosis strains which are resistant to currently utilized first- and second-line anti-TB drugs. Drug-discovery studies bioprospecting for compounds with novel anti-TB activities are therefore essential in order to control the spread of TB and to prevent a catastrophic pandemic. In this study, extracts from marine fungi were considered for antimycobacterial activity bioprospecting as they are largely underexplored. A total of 46 cultivable fungi were isolated from ascidians and 32 of these fungal isolates were sequenced and consequently identified. Among these fungi, the methanol crude extract from Clonostachys rogersoniana MGK33 was found to possess the highest antimycobacterial activity with minimum inhibitory concentrations of 0.125 and 0.200 µg/mL against Mycobacterium smegmatis mc2 155 and M. tuberculosis H37Rv, respectively. Untargeted metabolite profiling of the crude extract from C. rogersoniana MGK33 revealed the presence of bionectin F (among other compounds) which has previously been shown to possess antimicrobial activity in other studies. In silico molecular docking and simulation experiments in this study showed that bionectin F is a potential inhibitor of M. tuberculosis β-ketoacyl-ACP reductase (MabA). An attempt was then made to generate novel agents that would be composed of nanoparticles surface functionalized with the bioactive fungal extract from C. rogersoniana MGK33. In particular, mono-metallic SPIONs were synthesized using the co-precipitation method and then surface modified to produce bi-metallic superparamagnetic iron oxide nanoparticles (SPIONs) using nickel, zinc, gold, copper and silver, to produce Ni-SPIONs, Zn-SPIONs, Au-SPIONs, Cu-SPIONs and Ag-SPIONs. Functionalization was then performed using the MGK33 extract to produce Ni-SPIONs@MGK33, Zn-SPIONs@MGK33, Au-SPIONs@MGK33, Cu SPIONs@MGK33 and Ag-SPIONs@MGK33. Among these agents, Cu-SPIONs and Ag SPIONs were found to exhibit the strongest antimycobacterial activity, comparatively stronger than that of the counterparts, Cu-SPIONs@MGK33 and Ag-SPIONs@MGK33. In an experiment involving the treatment of RAW 264.7 macrophage cells infected with M. smegmatis mc2 155, the MGK33 extract exhibited the highest early apoptosis activity (9.61%), followed by Cu-SPIONs@MGK33 (3.34%), both agents tested at 1.96 µg/mL for 24 hours. The MGK33 extract further showed strong antimycobacterial activity against intracellular M. smegmatis mc2 155, compared with the nanoparticles synthesized in this study. Results in this study led to the conclusion that the marine fungus, C. rogersoniana MGK33 is a prolific source of compounds with antimycobacterial and immunomodulatory activity, and that further studies should be done to develop Cu-SPIONs and Ag-SPIONs into lead agents for anti-TB drug development.
- ItemInvestigation of the antimycobacterial activity of fungal endophytes and their magnetic dendrimer stabilized nanoparticles against mycobacteria(Stellenbosch : Stellenbosch University, 2024-03) Hussan, Raeesa Hoosen; Mavumengwana, Vuyo; Malgas-Enus, Rehana; Loxton, Andre Gareth; Allie, Nasiema; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.ENGLISH ABSTRACT: Tuberculosis (TB), is a disease caused by a single infectious agent Mtb, remains a global health threat that claimed the lives of 1.4 million people worldwide between 2020- 2021. Despite current anti tuberculosis treatment, TB remains one of the leading causes of infection highlighting the imminent need for drug discovery of alternative and novel treatments with distinct modes of action against Mycobacteria. In this context, the present study investigated the antimycobacterial activities of fungal endophyte metabolites functionalized on magnetic dendrimer stabilized nanoparticles (DSNPs) against mycobacterial models. To achieve the aim, fungal endophytes were isolated from four Fynbos families (Asteraceae, Lamiaceae, Ericaceae, and Droseraceae), sequenced and identified by phylogeny. Methanolic crude extracts obtained from cultivated fungi were tested for antimycobacterial activity against Mycobacterium tuberculosis H37Rv (Mtb H37Rv) and Mycobacterium smegmatis mc2155 (Msmeg mc2155). Metabolites within the bioactive fungal extracts were identified by untargeted liquid chromatography-mass spectrometry (LC-QTOF-MS/MS). The infection of THP-1 macrophage cells with Msmeg mc2155 was performed to determine the intracellular antimycobacterial activity of fungal crude extracts. The DSNPs were synthesized from modified magnetic iron oxide nanoparticles (MIONs) and G3-dendrimer micelles. Microscopic and spectral techniques (SEM, FTIR, UV-Vis, and ICP-AES) were used to characterize nanoparticles, followed by antimycobacterial activity assays. Twenty unique fungal isolates were identified with Penicillium being the abundant genera. Penicillium thomii, Diaporthe leucospermi, Penicillium rubens, Cadophora sp. and Penicillium sp. possess antimycobacterial activity. Cadophora sp. demonstrated the most significant inhibition of Msmeg mc2155 and the bioactivity was enhanced in the host-directed approach against intracellular Msmeg mc2155. The metabolites N-benzyl-1-tetradecanamine, N-benzyl-1-hexadecanamine, asperthecin, meleagrin, roquerfortine F, chlamydocin and neoxaline, (-)5-methylmellein, and 9-octadecenamide were identified with the latter two possessing antimycobacterial activity. The nanoparticles (G3- dendrimer micelles, MIONs and DSNPs) were successfully synthesized. G3-dendrimer micelles and DNSPs inhibited Msmeg mc2155 and the former Mtb H37Rv. MIONs possessed enhanced bioactivities against intracellular Msmeg mc2155. Functionalization of DSNPs with bioactive metabolites (nano metabolites) demonstrated no antimycobacterial activity against Msmeg mc2155 directly but antimycobacterial activity was observed intracellularly. Enhanced activity of nano-metabolites was observed directly against Mtb H37RV. Fungal extracts, nanoparticles and functionalized nanoparticles have distinct mechanisms of antimycobacterial activities against the strains of mycobacteria (Msmeg mc2155 and Mtb H37Rv). This study highlighted that the properties of nanoparticles greatly influence their antimycobacterial activities i.e., the ferrous content of a naked nanoparticle opposed to a modified nanoparticle. Functionalization of a nanoparticle contributes to its modification which has an impact on the antimycobacterial activity. Hence, this necessitates further investigations about nanoparticles, their properties and modifications against mycobacterial models. In addition, the nanoparticles have the potential to be modified to accommodate or scaffold existing anti-Tb drugs and to potentiate antimycobacterial effects through pathogen- and host directed approaches.