Use this URL to cite or link to this record in EThOS:
Title: Design, assembly and characterisation of peptide-targeted nanoparticles for cancer-specific delivery of DNA and RNA
Author: Wang, Ming
ISNI:       0000 0004 2699 5747
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
Decoration of nanoparticle surfaces with receptor-specific ligands can improve functional drug delivery to cancer cells. Our ligand of interest is a short peptide, U11, sequenced to show high affinity for the Urokinase Plasminogen Activator receptor (uPAR), a receptor overexpressed on the surface of many tumours. We prove that the presentation of the peptide ligand, along with the nature of the liposomal platform, play synergic roles in the exhibition of the nanoparticle’s targeting effect. U11 peptides were loaded onto PEGylated liposomal nanoparticle surfaces by covalent conjugation. In vitro pDNA transfection and uptake studies established the viability of the U11 peptide as a ligand for cancer cell targeting. Circular dichroism and fluorescence spectroscopy methods were used to examine the secondary and tertiary conformations of the surface peptides. siRNA encapsulation assays, nanoparticle turbidity and in vitro gene silencing experiments were used to optimise the targeted nanoparticle for in vivo delivery. In vivo siRNA (luciferase) experiments were performed on mice carrying uPAR-positive (DU145- luc and MDA-MB-231-luc) and uPAR-negative (PC3-luc) cancer xenografts. Biodistribution properties of the nanoparticles were examined by administrating fluorescently-labelled or microRNA-encapsulated nanoparticles. U11-targeted nanoparticles were able to enhance gene delivery (pDNA and siRNA) to uPARpositive cells. Nanoparticle platforms of lower zetapotential reduced non-specific electrostatic interactions with cell membranes, hence allowed enhanced exhibition of the ligand’s targeting effect. Adding further percentages of PEG increased nanoparticle stability, and maximised ligand exposure by forcing the U11-associated PEG chains into a brush conformation. In vivo, U11-nanoparticles indicated enhanced delivery efficacies of siRNA to models bearing small, uPAR-positive tumours. In larger, uPAR-negative xenografts, the accumulation of both targeted and non-targeted nanoparticles (by the enhanced permeation and retention effect) into tumours was equal, and indicated reduced protein expression to the same extent. 24- hours post-administration, accumulation into the liver and the spleen of targeted nanoparticles was higher compared to non-targeted nanoparticles, most likely a result of increased recognition of the nanoparticles by organ-specific macrophages. Without doubt, the introduction of surface ligands can enhance nanoparticle deliver to cancer cells, although careful organisation is required to maximise their effect. Low ligand densities, ligand extension via a PEG spacer, high platform PEGylation and low zetapotentials can aid the maximum exhibition of the ligand’s targeting effect. Such a presentation of surfaceligands can increase nanoparticle interaction with cancer cell receptors, although it can also lead to greater accumulation into the liver and spleen.
Supervisor: Thanou, Maya ; Miller, Andrew Sponsor: EPSRC ; Royal Society ; Imperial College IC Trust ; JSPS
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral