Synthesis and Characterisation of Novel Polymeric Nano-Systems for Pharmaceutical Applications

Abstract

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
Original language	English
Awarding Institution	University of Brighton
Supervisor	Jonathan Salvage (Supervisor)