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Title: Engineering pathways of polymersome production and characterisation
Author: Lopez Vazquez, Ciro
ISNI:       0000 0004 8507 979X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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Polymeric vesicles, also known as polymersomes, have been widely studied for their use in biological applications and have shown great potential for their application as delivery systems. Current polymersome production methods usually require a long period of time to produce highly monodisperse samples. Therefore, there is an unmet need for a process able to speed up the production of polymersomes. In this work, an engineered top-down process based on the hydration of polymer coated glass beads is presented, along with the computation of particle molecular parameters and their TEM characterisation, based on the staining agent brightness intensity. Polymersomes prepared by the beads hydration method were characterised by TEM and DLS techniques, showing a high vesicle throughput with a narrow average diameter in just a few hours, compared to the 4-6 weeks of hydration needed for alternative hydration techniques. Particle characterisation was carried out with an asymmetric flow fi eld-flow fractionation (AF4) system on PMPC25-b-PDPAn (n=43,68,100) self-assemblies. AF4 allowed the simultaneous particle analysis by DLS and SLS, making it feasible to infer particle morphology and the computation of the block copolymer packing factor, by applying the corresponding geometrical model. For the shortest PDPA chain (n=43), AF4 suggested a disk-like micelle morphology and a 0.4 packing factor whilst for the remaining PDPA chain lengths (n=68,100) AF4 indicated the presence of both disk-like micelles and vesicle-like morphologies with a packing factor value characteristic of bilayer assemblies (0.5). Finally, a TEM brightness intensity is described with the brightness intensity of the staining agent used during the TEM grids preparation. Due to the bilayer comprised within a vesicle, the number of MPC monomers is greater, compared to a disk micelle, therefore the contrast produced by the staining agent would be more signi cant, making it possible to differentiate disks from vesicles. TEM intensity analysis con firmed the presence of only one particle morphology for PMPC25-b-PDPA43, as suggested by AF4, and showed a correlation between size and morphology for PMPC25-b-PDPA68 and PMPC25-b-PDPA100. In conclusion, a novel and more effective method for the production of polymersomes is described, which decreases the waiting time for vesicle formation. AF4 system validated the growth of disk-like micelles into vesicles for block copolymers with a packing factor value of 0.5. Moreover, a TEM analysis based on particle brightness intensity aided in the differentiation of particle morphology, considering that disk micelles can show a wide range of sizes which makes it challenging to categorise them in a common TEM micrograph.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available