Single-chain antibody-targeted nanoparticles for diagnosis of vascular diseases

This project aims to develop nanoparticle contrast agents for magnetic resonance imaging (MRI) that selectively target molecular markers of cardiovascular disease (CVD). These imaging agents will be developed for the early detection of unstable, rupture-prone, vulnerable atherosclerotic lesions, thrombosis and difficult to diagnose vessel occlusions, such as pulmonary embolism. We have generated specific single-chain antibodies (scFv) that can selectively target markers associated with atherosclerosis and thrombosis. These include 1) scFv59D8, which targets fibrin, the end product of humoral coagulation; and 2) scFv anti- GPIIbIIIa, which targets activated platelets. We have already demonstrated that non-covalent coupling of superparamagnetic iron oxide (SPIO)-beads to scFv anti-GPIIbIIIa can target and image activated platelets in vessels in vitro and in vivo by MRI. We will use Gadolinium (Gd)- loaded dendrimers to give contrast in MRI. Dendrimers have a highly branched, three- dimensional, nanoscale architecture, low polydispersity and multivalent surfaces that allow simultaneous binding of Gd for imaging and scFvs for targeting. The antigen-specific binding capacity of the scFv-dendrimer constructs will be confirmed using fluorescence-labelled dendrimers in flow cytometry. Optimal size and Gd-loading will be determined via in vitro MRI of human thrombi. Finally, efficacy studies in a mouse model of atherosclerosis and a rabbit model of pulmonary embolism will provide in vivo proof of the imaging capability of the constructs.