Abstract 2238: New Pharmacokinetic Models for Quantitative Molecular Imaging of Plaque Angiogenesis with Intergrin-targeted Nanoparticles

Abstract

Cardiovascular molecular imaging with targeted nanoparticles has emerged as a promising method for early detection of atherosclerosis and vulnerable plaque. However, traditional pharmacokinetic models for diffusible drugs are inadequate to describe the efficacy of nanoparticle carriers of diagnostic and therapeutic cargos. To quantify blood and MRI tissue signals from gadolinium-loaded nanoparticles (Gd-NP) targeted to avb3 integrins expressed on angiogenic capillaries in the aortas of cholesterol-fed rabbit, a novel 4 compartment open PK model was developed that utilized a unique simultaneous fitting scheme. In 10 rabbits fed 0.25% cholesterol for 3 months, the concentration of nanoparticles was measured serially from blood samples after injection of 1 ml/kg of targeted or nontargeted Gd-NP. The MRI proton signatures emanating from nanoparticles bound to the expanded vasa vasorum of the descending thoracic aorta was computed for all aortic cross sections in 1.5T T1w fa-suppressed spin-echo images. Based on the PK analysis, the concentration of targeted nanoparticles in the aortic wall is double that of non-targeted nanoparticles. Notably, this signal enhancement is achieved with 20x less gadolinium (4.6x10 −3 mmol Gd/kg BW) as compared with the dose of conventional gadolinium agents (0.1 mmol/kg). Further, the PK analysis shows that the targeted nanoparticles are more than three times more effective at reaching the aortic wall. These results should facilitate development and use of nanotechnologies intended for early detection of atherosclerosis and provide enhanced understanding of the kinetics and mechanisms of active targeting of plaque angiogenesis.