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The bio-conjugation of Cytochalasin B
Thesis (MSc)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2019
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| _version_ | 1867614053120081920 |
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| access_status_str | Open Access |
| author | Bertossi, Luca |
| author2 | Klumperman, Bert |
| author_browse | Bertossi, Luca Klumperman, Bert |
| author_facet | Klumperman, Bert Bertossi, Luca |
| author_sort | Bertossi, Luca |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/105667 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:45:54.519Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2019 |
| publishDateRange | 2019 |
| publishDateSort | 2019 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/105667 The bio-conjugation of Cytochalasin B Bertossi, Luca Klumperman, Bert Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Cytochalasins Polymeric drugs Drug delivery systems Malariotherapy Fragmentation reactions Thesis (MSc)--Stellenbosch University, 2023. ENGLISH ABSTRACT: The focus of this study was on the bio-conjugation of Cytochalasin B to a poly(N-vinylpyrrolidone) (PVP) based polymeric drug delivery system designed to combat malaria. The amphiphilic character of the PVP-cytochalasin conjugate induces the self-assembly of nanostructures and the incorporation of an acid labile linker between cytochalasin and PVP provides potential for pH stimuli-triggered release of the cytochalasin from the PVP construct intact. Two multi-functional reversible-addition fragment chain transfer (RAFT) agents were prepared. Both RAFT agents contained a xanthate based Z group, however, they differed in their R groups. One contained a linear acetal along with a triazole linker, RAFT-(1), compared to a cyclic acetal (1,3- dioxolane) connected via an ethylene glycol linker, in RAFT-(2). Both RAFT agents controlled the polymerisation of N-vinylpyrrolidone (NVP) in aqueous media in the preparation of ω,αheterotelechelic PVP containing the desired and protected aldehyde group at the α end and the thiol functionality at the ω end. A one-pot deprotection procedure was employed to elicit the aldehyde and thiol functionalities on both RAFT systems however the end group functionalised PVP prepared via RAFT-(2) was used in subsequent experiments. This was done as the xanthate end group retention was greater when using RAFT-(1) and the scope of the study was increased by using a novel RAFT agent. A model targeting ligand was conjugated to the aldehyde functionalised, α end of the PVP construct via a reductive amination reaction with the N-terminus on the model targeting ligand. Cholesterol was used as a model drug and conjugated to the ω end of the polymer through a Michael addition, thiolene click reaction onto the acylated cholesterol, generating an acid labile β-thiopropionate linker. The PVP-cholesterol (PVP-Chol) conjugate was characterised by 1H-NMR spectroscopy. The amphiphilic PVP-Chol conjugate was self-assembled into micelles when placed in aqueous media, other larger nanostructures were also observed via TEM analysis. Cytochalasin B (CB), a strong glucose transport inhibitor, was regio-selectively acylated using an enzyme catalysed esterification method, as characterised by electronspray ionisation mass spectrometry (ESI-MS). The acylated product could not be prepared on a practical scale for further use. Therefore, cytochalasin A (CA), a weaker glucose transport inhibitor, was deemed a viable alternative and was acylated using conventional methods. Acylated cytochalasin A (Ac-CA) was conjugated to the PVP in the same fashion as the model drug (cholesterol), through a Michael addition reaction. The conjugate was characterised by 1H-NMR spectroscopy, diffusion ordered spectroscopy (DOSY) and size exclusion chromatography (SEC). With two α,β-unsaturated ester functionalities present on Ac-CA, the region of conjugation was indistinguishable, however all three techniques confirmed 1:1 PVP conjugation to cytochalasin A. Self-assembly experiments indicated that the amphiphilic PVPcytochalasin A (PVP-CA) conjugate could attain different morphologies (micelles ranging from 26-32 nm and vesicles of 326 nm when measured using TEM images) when changing the water content added to the N,N-Dimethylformamide (DMF) solution after transmission electron microscopy (TEM) analysis. This indicated that the PVP-CA conjugate behaves similarly to block copolymer systems that undergo self-assembly in aqueous media. AFRIKAANSE OPSOMMING: Die fokus van hierdie studie was op die bio-vervoeging van cytochalasin na 'n poly(N-vinielpyrrolidoon) (PVP) gebaseerde polimeriese dwelm afleweringsisteem wat ontwerp is om malaria te bestry. Die amfifiliese karakter van die PVP-cytochalasin-konjugaat veroorsaak die self-samestelling van nanostrukture en die inkorporering van 'n suur labiele skakelaar tussen cytochalasin en PVP bied potensiaal vir pH-stimuli-geaktiveerde vrystelling van die cytochalasin van die PVP-konstruksie ongeskonde. Twee multi-funksionele RAFT agente is voorberei. Beide RAFT-agente bevat 'n xanthate Z-groep, maar hulle het in hul R-groepe verskil. Een bevat 'n lineêre acetaal saam met 'n triasool-skakelaar, RAFT-(1), in vergelyking met 'n sikliese aksetal (1,3-dioxolaan) wat in 'n etileenglykol skakelaar in RAFT-(2) verbind word. Beide RAFT-agente beheer die polimerisasie van N-vinylpyrrolidoon (NVP) in waterige media by die bereiding van ω,α-heterotelecheliese PVP wat die gewenste en beskermde aldehiedgroep by die α-einde en die tiolfunksionaliteit by die ω-einde bevat. 'N Eendeprotbeskermingsprosedure is gebruik om die aldehied- en tiolfunksionaliteite op beide RAFT-stelsels uit te lok, maar die eindgroep funksionaliseerde PVP wat via RAFT-(2) voorberei is, is in volgende eksperimente gebruik. Dit is gedoen omdat die xanthate-eindgroep-retensie groter was toe RAFT-(1) gebruik is en die omvang van die studie verhoog is deur 'n nuwe RAFT-agent te gebruik. 'N Modellerende ligand is gekonjugeer aan die aldehied funksie, α-einde van die PVP-konstruksie via 'n reduktiewe aminasiereaksie met die N-terminus van die model-teikenligand. Cholesterol is gebruik as 'n model geneesmiddel en gebuig aan die ω einde van die polimeer deur middel van 'n Michaelbyvoeging, tiol-een kliekreaksie op die geaksileerde cholesterol, wat 'n suur labiele β-tiopropionaat skakelaar opwek. Die PVP-cholesterol (PVP-Chol) -konjugaat is gekenmerk deur 1H-NMRspektroskopie. Die amfifile PVP-Chol-konjugaat was selfmengsel in micelle wanneer dit in waterige media geplaas is, ander groot nanostrukture is ook waargeneem via TEM-analise. Cytochalasin B (CB), 'n sterk glukose vervoermiddel inhibitor, is streek-selektief geoksileer met behulp van 'n ensiem gekataliseerde veresteringsmetode, wat gekenmerk word deur elektronsprei ionisasie massaspektrometrie (ESI-MS), maar dit kon nie op 'n praktiese skaal vir verdere gebruik bereik word nie. Daarom is cytochalasin A (CA), 'n swakker glukosevervoer inhibitor, beskou as 'n lewensvatbare alternatief en geaktiveer deur gebruik te maak van konvensionele metodes. Geacyleerde cytochalasin A (Ac-CA) is op dieselfde wyse as die model dwelm (cholesterol) by die PVP gekonjugeer, deur middel van 'n Michael-addisie reaksie. Die vervoeging is gekenmerk deur 1H-NMR spektroskopie, diffusie bestel spektroskopie (DOSY) en grootte negatief chromatografie (SEC). Met twee α, β-onversadigde esterfunksionaliteite teenwoordig op Ac-CA, was die vervoegingsgebied ononderskeibaar, maar al drie tegnieke het 1:1 PVP-vervoeging tot cytochalasin A bevestig. Self-samestellingseksperimente het aangedui dat die amfifiele PVP-cytochalasin A (PVP-CA) konjugate kon verskillende morfologieë bereik (micelle wat wissel van 26-32 nm en vesikels van 114 nm, gemeet deur gebruik te maak van TEMbeelde) wanneer die wt % van die water na die DMF-oplossing na TEM-analise verander. Dit het aangedui dat die PVP-CA-vervoeging op soortgelyke wyse optree as blokko-polimeerstelsels wat selfmonteer in waterige media ondergaan. Masters 2019-02-21T08:35:40Z 2019-04-17T08:07:17Z 2022-08-21T03:00:13Z 2019-02 Thesis http://hdl.handle.net/10019.1/105667 en_ZA Stellenbosch University xiv, 74 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Cytochalasins Polymeric drugs Drug delivery systems Malariotherapy Fragmentation reactions Bertossi, Luca The bio-conjugation of Cytochalasin B |
| title | The bio-conjugation of Cytochalasin B |
| title_full | The bio-conjugation of Cytochalasin B |
| title_fullStr | The bio-conjugation of Cytochalasin B |
| title_full_unstemmed | The bio-conjugation of Cytochalasin B |
| title_short | The bio-conjugation of Cytochalasin B |
| title_sort | bio conjugation of cytochalasin b |
| topic | Cytochalasins Polymeric drugs Drug delivery systems Malariotherapy Fragmentation reactions |
| url | http://hdl.handle.net/10019.1/105667 |
| work_keys_str_mv | AT bertossiluca thebioconjugationofcytochalasinb AT bertossiluca bioconjugationofcytochalasinb |