The goal of this project is to achieve targeted delivery of angiostatic agents to sites of neovascularization. This is a widely accepted strategy that is limited in part by technologies of delivery and validation. The proposed studies center around a novel, biocompatible delivery device, the nanoparticle (NP), as a means to provide sustained, targeted delivery of angiostatic agents to sites of angiogenesis: wounds and tumors. The key elements of the delivery system are low toxicity and compositional flexibility, based interactions of charged polymer pairs. As a model system, we have utilized novel peptide analogs of thrombospondin-l (TSP-1) previously shown to have angiostatic properties. To provide retention within NP, these peptides have been prepared as polyethylene glycol conjugates that retain both heparin binding and biological activity. NP prepared with TSP-1 peptide conjugates show a markedly different biodistribution than empty NP and localization to sites of neovascularization. This proposal sets out to accomplish three goals: (1) optimization of the NP formulation, including dose-setting and incorporation of other targeting agents; (2) use of imaging and tracer technologies to ascertain biodistribution of targeted NP in mice; (3) validation of the efficacy of targeted delivery of NP containing angiostatic agents to wounds and tumors. In further studies, a peptide sequence derived from apolipoprotein E will be incorporated into the nanoparticle to enhance selective targeting of endothelial cells. Tumor delivery and targeting will be tested by noninvasive imaging using luciferase bioluminescence, 123I-scintigraphic imaging, and magnetic resonance imaging with gadolinium contrast. Conventional tracer technologies and microscopic localization of fluorescently labeled NP will be applied as well. In vivo, real-time image analysis of tumor vascularity will be determined by power Doppler ultrasound, and tumor mass will be determined by magnetic resonance imaging. In addition, conventional morphometric and histological techniques will be used to quantify the efficacy of this novel drug delivery system. The objective is to design drug delivery systems that will specifically target pathological angiogenesis with minimal effects on the normal vasculature.
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