Broad distribution and activity limit the utility of anti-cancer compounds by causing unacceptable systemic toxicity and narrow therapeutic indices. To improve tumour accumulation, drug-loaded macromolecular assemblies have been designed to replace conventional surfactant-based formulations. Their nanoscale size enhances tumour accumulation via hyperpermeable vasculature and reduced lymphatic drainage. Incorporating targeting ligands introduces cell specificity through receptor-specific binding and uptake, enabling drugs to reach intracellular targets. In this work, the targeting properties of polymer nanoparticle micelles of poly(2-methyl-2-carboxytrimethylene carbonate-co-D,L-lactide)-graft-poly(ethylene glycol)-furan (poly(TMCC-co-LA)-g-PEG) were verified using in vitro and in vivo models of breast cancer.
To select a relevant mouse model, the vascular and lymphovascular properties of two tumour xenograft models were compared. Greater accumulation of a model nanocarrier was observed in orthotopic mammary fat pad (MFP) tumours than size matched ectopic subcutaneous tumours, suggesting that the organ environment influenced the underlying pathophysiology. Immunostaining revealed greater vascular thickness, density and size, and thinner basement membranes in MFP tumours, likely contributing to greater blood perfusion and vascular permeability.
Based on these observations, MFP tumour-bearing mice were used to characterize the pharmacokinetics and biodistribution of a taxol drug, docetaxel, encapsulated in poly(TMCC-co-LA)-g-PEG nanoparticles. The nanoparticle formulation demonstrated longer docetaxel circulation in plasma compared to the conventional surfactant-based formulation. As a result, greater docetaxel retention was uniquely measured in tumour tissue, extending exposure of tumour cells to the active compound and suggesting potential for increased anti-cancer efficacy.
Furthermore, active targeting of antibody-modified nanoparticles to live cells was shown to be selective and receptor-specific. Binding isotherms were used to quantify the impact of antibody density on binding strength. The equilibrium binding constant increased linearly with the average number of antibodies per particle, which is consistent with a single antibody-antigen interaction per particle. This mechanistic understanding enables binding behaviour to be adjusted in a predictive manner and guides rational nanoparticle design.
These studies validate poly(TMCC-co-LA)-g-PEG nanoparticles as a platform for targeted delivery to cancer on both a tissue and cellular level, forming a compelling justification for further pre-clinical evaluation of this system for safety and efficacy in vivo.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/34054 |
| Date | 13 December 2012 |
| Creators | Ho, Karyn |
| Contributors | Shoichet, Molly |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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