In vivo angiogenesis imaging of solid tumors by α_vβ ₃-targeted, dual-modality micellar nanoprobes

The objective of this study was to develop and evaluate an α_vβ₃-specific nanoprobe consisting of fluorescent superparamagnetic polymeric micelles (FSPPM) for in vivo imaging of tumor angiogenesis. Spherical micelles were produced using poly(ethylene glycol)-b-poly(D,L-lactide) co-polymers conjugated with tetramethylrhodamine, a fluorescent dye, and loaded with superparamagnetic iron oxide nanoparticles. The resulting micelle diameter was 50-70 nm by dynamic light scattering and transmission electron microscopy measurements. Micelles were encoded with an α_vβ₃-specific peptide, cyclic RGDfK, and optimized for maximum fluorescence and targeting in α_vβ ₃-overexpressing cells in vitro. In mice, cRGD-FSPPM-treated animals showed α_vβ₃-specific FSPPM accumulation in human lung cancer subcutaneous tumor xenografts. Together with the histological validation, the three-dimensional gradient echo magnetic resonance imaging (MRI) data provide high spatial resolution mapping and quantification of angiogenic vasculature in an animal tumor model using targeted, ultrasensitive MRI nanoprobes.