Gadolinium-Functionalized Peptide Amphiphile Micellesfor Multimodal Imaging of Atherosclerotic Lesions

摘要

The leading causes of morbidity and mortality globally are cardiovascular diseases, and nanomedicine can provide many improvements including disease-specific targeting, early detection, and local delivery of diagnostic agents. To this end, we designed fibrin-binding, peptide amphiphile micelles (PAMs), achieved by incorporating the targeting peptide cysteine-arginine-glutamic acid-lysine-alanine (CREKA), with two types of amphiphilic molecules containing the gadoliniuim (Gd) chelator diethylenetriaminepentaacetic acid (DTPA), DTPA-bis(stearylamide)(Gd), and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[(poly(ethylene glycol) (PEG))-2000]-DTPA(Gd) (DSPE-PEG2000-DTPA(Gd)). The material characteristics of the resulting nanoparticle diagnostic probes, clot-binding properties in vitro, and contrast enhancement and safety for dual, optical imaging–magnetic resonance imaging (MRI) were evaluated in the atherosclerotic mouse model. Transmission electron micrographs showed a homogenous population of spherical micelles for formulations containing DSPE-PEG2000-DTPA(Gd), whereas both spherical and cylindrical micelles were formed upon mixing DTPA-BSA(Gd) andCREKA amphiphiles. Clot-binding assays confirmed DSPE-PEG2000-DTPA(Gd)-basedCREKA micelles targeted clots over 8-fold higher than nontargeting(NT) counterpart micelles, whereas no difference was found betweenCREKA and NT, DTPA-BSA(Gd) micelles. However, in vivo MRI and opticalimaging studies of the aortas and hearts showed fibrin specificitywas conferred by the peptide ligand without much difference betweenthe nanoparticle formulations or shapes. Biodistribution studies confirmedthat all micelles were cleared through both the reticuloendothelialsystem and renal clearance, and histology showed no signs of necrosis.In summary, these studies demonstrate the successful synthesis, andthe molecular imaging capabilities of two types of CREKA-Gd PAMs foratherosclerosis. Moreover, we demonstrate the differences in micelleformulations and shapes and their outcomes in vitro versus in vivofor site-specific, diagnostic strategies, and provide the groundworkfor the detection of thrombosis via contrast-enhancing agents andconcurrent therapeutic delivery for theranostic applications.