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dc.contributor.advisor Chilkoti, Ashutosh en_US
dc.contributor.author Simnick, Andrew Joseph en_US
dc.date.accessioned 2010-05-10T20:16:20Z
dc.date.available 2011-07-26T04:30:03Z
dc.date.issued 2010 en_US
dc.identifier.uri http://hdl.handle.net/10161/2426
dc.description Dissertation en_US
dc.description.abstract <p>Antivascular targeting is a promising strategy for tumor therapy. This strategy overcomes many of the transport barriers and has shown efficacy in many preclinical models, but targeting epitopes on tumor vasculature can also promote accumulation in healthy tissues. We used Elastin-like Polypeptide (ELP) to form block copolymers (BCs) consisting of two separate ELP blocks seamlessly fused at the genetic level. ELPBCs self-assemble into spherical micelles at a critical micelle temperature (CMT), allowing external control over monovalent unimer and multivalent micelle forms. We hypothesized that thermal self-assembly could trigger specific binding of ligand-ELPBC to target receptors via the multivalency effect as a method to spatially restrict high-avidity interactions. We termed this approach Dynamic Affinity Modulation (DAM). The objectives of this study were to design, identify, and evaluate protein-based drug carriers that specifically bind to target receptors through static or dynamic multivalent ligand presentation.</p> <p>ELPBCs were modified to include a low-affinity GRGDS or GNGRG ligand and a unique conjugation site for hydrophobic compounds. This addition did not disrupt micelle self-assembly and facilitated thermally-controlled multivalency. The ability of ligand-ELPBC to specifically interact with isolated AvB3 or CD13 was tested using an in vitro binding assay incorporating an engineered cell line. RGD-ELPBC promoted specific receptor binding in response to multivalent presentation but NGR-ELPBC did not. Enhanced binding with multivalent presentation was also observed only with constructs exhibiting CMT < body temperature. This study establishes proof-of-principle of DAM, but ELPBC requires thermal optimization for use with applied hyperthermia. Static affinity targeting of fluorescent ligand-ELPBC was then analyzed in vivo using intravital microscopy (IM), immunohistochemistry (IHC), and custom image processing algorithms. IM showed increased accumulation of NGR-ELPBC in tumor tissue relative to normal tissue while RGD-ELPBC and non-ligand ELPBC did not, and IHC verified these observations. This study shows (1) multivalent NGR presentation is suitable for static multivalent targeting of tumors and tumor vasculature, (2) multivalent RGD presentation may be suitable for DAM with thermal optimization, and (3) ELPBC micelles may selectively target proteins at the tumor margin.</p> en_US
dc.format.extent 4371190 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Engineering, Biomedical en_US
dc.subject Engineering, Materials Science en_US
dc.subject Biology, Molecular en_US
dc.subject Biomaterials en_US
dc.subject Block Copolymers en_US
dc.subject Cancer en_US
dc.subject Drug Delivery en_US
dc.subject Multivalency en_US
dc.subject Vascular Targeting en_US
dc.title Affinity-Modulation Drug Delivery Using Thermosensitive Elastin-Like Polypeptide Block Copolymers en_US
dc.type Dissertation en_US
dc.department Biomedical Engineering en_US
duke.embargo.months 12 en_US

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