Folate-targeted optical and magnetic resonance dualmodality PCL-b-PEG micelles for tumor imaging

A biodegradable tumor targeting nano-probe based on poly(ɛ-caprolactone)-b-poly(ethylene glycol) block copolymer (PCL-b-PEG) micelle functionalized with a magnetic resonance imaging (MRI) contrast agent diethylenetriaminepentaacetic acid-gadolinium (DTPA-Gd3+) on the shell and a near-infrared (NIR) dye in the core for magnetic resonance and optical dual-modality imaging was prepared. The longitudinal relaxivity (r1) of the PCL-b-PEGDTPA-Gd3+ micelle was 13.4 (mmol/L)−1s−1, three folds of that of DTPA-Gd3+, and higher than that of many polymeric contrast agents with similar structures. The in vivo optical imaging of a nude mouse bearing xenografted breast tumor showed that the dual-modality micelle preferentially accumulated in the tumor via the folic acid-mediated active targeting and the passive accumulation by the enhanced permeability and retention (EPR) effect. The results indicated that the dualmodality micelle is a promising nano-probe for cancer detection and diagnosis.