Prostate specific membrane antigen (PSMA) targeting polymer-peptide conjugates

Jokonya, Simbarashe (2017-03)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: The primary objective of the study was the development of a polymeric drug delivery system targeting prostate specific membrane antigen (PSMA) by employing amphiphilic poly(N-vinylpyrrolidone) (PVP) as a drug delivery vehicle and tyrothricin as an anti-tumour agent. Three xanthate based reversible addition-fragmentation chain-transfer (RAFT) agents were synthesised, namely: α-succinimide ω-xanthate, α-hydroxyl ω-xanthate, and α-acetal ω-xanthate. The RAFT agents were subsequently employed in the polymerisation of N-vinylpyrrolidone to form α- and ω-heterotelechelic PVP. The α-acetal ω-xanthate heterotelechelic PVP system was selected because of its ability to form aldehyde and thiol/disulphide functionalities on the α- and ω-chain ends respectively in a one pot deprotection strategy. The deprotected PVP was conjugated to a model ligand through Schiff base and reductive animation via the N-terminus and a model drug via thiol-ene Michael addition. Successful conjugation of model compounds was followed by a five stage synthesis of a glutamate urea based PSMA targeting small molecule ligand starting with L-lysine. The targeting ligand was subsequently conjugate to the α-chain end of PVP via the N-terminus. Tyrothricin was purified to remove erythrocyte haemolytic linear gramicidin and modified to introduce acrylate on the L-lysine and L-ornithine residues. Conjugation to PVP via an acid labile β-thiopropionamide was achieved through thiol-ene Michael addition. The resultant drug delivery construct was self-assembled into micellar structures and particle diameter was determined by dynamic light scattering (DLS); z average 151 d.nm and confirmed by scanning transmission electron microscopy (STEM). The release studies were done by dissolving the conjugates in formic acid solutions of pH = 5.5 and 3.0. Real time analysis on an ultra-performance liquid chromatography coupled to a mass spectrometer detector (UPLC-MS) was done by monitoring tyrothricin release over 24 hours. Tyrothrin was not detected after 24 hours leading to the conclusion that the amide bond was too strong to be destabilised by the β-thio ether in a similar way to the ester.

AFRIKAANSE OPSOMMING: Die primêre doel van die studie was om 'n polimeriese dwelmvervoerstelsel te ontwikkel wat fokus op ‘n prostaatspesifieke membraanantigeen (PSMA) deur die amfifiliese polivinielpirrolidoon as die dwelmafleweringsvoertuig en tirotrisien as die anti-kankermiddel te gebruik. Drie xantaat-gebaseerde omkeerbare addisie-fragmentasie kettingoordrag (OAFO) agente is gesintetiseer; α- succinimide ω- xantaat, α- hidroksiel ω- xantaat, en α- asetaal ω- xantaat. Die OAFO agente is daarna gebruik in die polimerisasie van N-Vinielpirrolidoon om α- en ω-heterotelecheliese polivinielpirrolidoon (PVP) te vorm. Die α- asetaal ω- xantaat heterotelecheliese PVP stelsel is gekies omdat dit onderskeidelik aldehiede en tiol/disulfied funksionelegroepe op die α- en ω- eindkettings vorm in 'n een-pot-sintese om die beskermings groepe te verwyder. Die beskermde PVP was gekonjugeerd aan ‘n modelligand deur Schiff basis en reduktiewe aminasie via die N-terminus en aan 'n modeldwelm via tiol-een Michael addisie. Suksesvolle konjugasie van die modelverbindings was gevolg deur 'n vyf stap sintese van 'n glutamaat ureum gebaseerde PSMA wat kleinmolekuul ligande teiken. Die ligand wat ‘n teiken sal bereik is daarna gekonjugeerd aan die α-eindketting van PVP via die N-terminus. Tirotrisien is gesuiwer om eritrosiet-hemolitiese-lineêre-gramisidien te verwyder en is daarna gemodifiseer om akrielaat funksionelegroepe aan die L-Lisien en L-ornitien te heg. Konjugasie aan die PVP via 'n suurlabiele β-tiopropionaatamied is bereik deur ‘n tiol-een Michael addisie. Die gevolglike geneesmiddelafleweringssisteem het miselstrukure gevorm tydens selfaddisie en deeltjiegrootte is bepaal deur skanderingtransmissie-elektronmikroskopie (STEM) en dinamieseligverspreiding (DLV); z gemiddelde 151 d.nm. Die vrystellingsstudies is gedoen deur die gekonjugeerdesisteem op te los in mieresuuroplossings van pH = 5.5 en 3.0. Regstreeksetydanalise op ‘n ultra-prestasie-vloeistofchromatograaf wat gekoppel is aan 'n massaspektrometerdetektor (UPLC-MS) is gedoen om tirotrisienvrylating oor ‘n tydperk van 24 uur te bestudeer. Tirotrisienvrylating is nie waargeneem na 24 uur nie. Dit lei tot die gevolgtrekking dat die amiedbinding te sterk was om gedestabiliseer te word deur die tiol.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100807
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