Polymeric nano-systems formed by self-assembling block copolymers have
attracted attention due to their ability to load and deliver therapeutic agents
intracellularly, and high in-vitro and in-vivo stability. Systems utilising
biocompatible phosphorylcholine (PC) based copolymers have shown promise,
particularly the diblock copolymer poly(2-methacryloyloxyethyl
phosphorylcholine-b-poly(2-(diisopropylamino)ethyl methacrylate) (MPC-DPA).
However, previous studies have not elucidated the relationships of ethanolic atom
transfer radical polymerisation (ATRP) to MPC-DPA block length limits, MPCDPA
block length to particle size, morphology, and cell uptake, and the ability to
load and delivery the anticancer drug Docetaxel (DTX) to human cancer cell lines.
In this project, a series of novel block length MPC-DPA diblock copolymers were
successfully synthesised at ambient temperature via ethanolic ATRP. 1H-NMR and
gel permeation chromatography (GPC) revealed the copolymers to be well defined
with molecular weights (Mn) ranging from 10 K-64 K and polydispersity (Mw/Mn)
< 1.1. Dynamic light scattering (DLS) revealed the copolymers formed
controllable, and stable, nanoparticle systems, ranging from 25 nm to 140 nm
diameter, relative to polymer molecular weight. The MPC-DPA formed selfassembled
nanoparticles at physiological pH, with unimer to micelle transition
occurring between pH 6.0-7.0, and were stable across a wide temperature range (5-
70°C). Critical micelle concentration (CMC) and DLS particle stability upon
dilution data were comparable, suggesting that the MPC-DPA nano-systems were
resistant to dissociation, and therefore a suitable candidate for pharmaceutical
application development. DLS and scanning transmission electron microscopy
(STEM) indicated that the MPC-DPA formed differing colloidal aggregates, such
as micelles or vesicles, as MPC and DPA block lengths were adjusted. The
toxicological profile of the MPC-DPA was assessed via clonogenic, MTT, and LDH
assays, which revealed the copolymers to be of low cytotoxicity. In-vitro cellular
uptake was studied in response to changes in the physical properties of MPC-DPA,
via flow cytometry and confocal laser scanning microscopy, and demonstrated
successful and rapid uptake of MPC-DPA nanoparticles in healthy and cancer cell
lines. The anticancer drug DTX was successfully encapsulated into the MPC-DPA
micelles via nanoprecipitation and direct dissolution. Subsequent in-vitro studies of
DTX loaded MPC-DPA nano-systems were performed on the human cancer cell
lines, MCF-7, SKOV-3, and PC3, which revealed that 42 nm diameter DTX loaded
MPC-DPA micelles produced an anticancer effect in SKOV-3 ovarian cancer and
PC3 prostate cancer cells. Therefore, the novel data obtained from this study
suggested that MPC-DPA diblock copolymers have the potential for pharmaceutical
application in the form of a DTX anticancer drug delivery system.
Date of Award | 2018 |
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Original language | English |
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Awarding Institution | |
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Supervisor | Jonathan Salvage (Supervisor) |
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Synthesis and Characterisation of Novel Polymeric Nano-Systems for Pharmaceutical Applications
Shakargi, S. (Author). 2018
Student thesis: Doctoral Thesis