The blood brain barrier (BBB) remains a major challenge to the advancement and application of systemic anti-cancer therapeutics into the central nervous system. The structural and physiological delivery constraints of the BBB significantly limit the effectiveness of conventional chemotherapy, thereby making systemic administration a non-viable option for the vast majority of chemotherapy agents. Furthermore, the lack of specificity of conventional systemic chemotherapy when applied towards malignant brain tumors remains a major shortcoming. Hence novel therapeutic strategies that focus both on targeted and enhanced delivery across the BBB are warranted. In recent years nanoparticles (NPs) have emerged as attractive vehicles for efficient delivery of targeted anti-cancer therapeutics. In particular, gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provide a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, the permeation of AuNPs across the BBB has not been well characterized, and hence is a potential limitation for successful application of AuNP-based therapeutics within the central nervous system (CNS).
In this dissertation, we designed and characterized AuNPs and assessed the role of polyethylene glycol (PEG) on the physical and biological properties of AuNPs. We established a size-dependent permeation profile with respect to core size as well as PEG length when AuNPs were assessed through a transport-permissive in-vitro BBB. This study was the first of its kind to systematically examine the influence of design on permeation of AuNPs through transport-permissive BBB. Given the significant delivery limitations through the non-transport permissive and intact BBB, we also assessed the role of magnetic resonance imaging (MRI) guided focused ultrasound (MRgFUS) disruption of the BBB in enhancing permeation of AuNPs across the intact BBB and tumor BBB in vivo. MRgFUS is a novel technique that can transiently increase BBB permeability thereby allowing delivery of therapeutics into the CNS. We demonstrated enhanced delivery of AuNPs with therapeutic potential into the CNS via MRgFUS. Our study was the first to establish a definitive role for MRgFUS in delivering AuNPs into the CNS. In summary, this thesis describes results from a series of research projects that have contributed to our understanding of the influence of design features on AuNP permeation through the BBB and also the potential role of MRgFUS in AuNP permeation across the BBB.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/33988 |
| Date | 11 December 2012 |
| Creators | Etame, Arnold |
| Contributors | Rutka, James T. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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