Indocyanine green loaded SPIO nanoparticles with phospholipid-PEG coating for dual-modal imaging and photothermal therapy

A biodegradable nanotheranostic agent has been successfully constructed for fluorescence/magnetic resonance dual-modal imaging guided photothermal therapy by loading indocyanine green (ICG) molecules into 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol)] (DSPE-PEG) coated superparamagnetic iron oxide (SPIO) nanoparticles (NPs). It was proved that the obtained SPIO@DSPE-PEG/ICG NPs with an average diameter around 27.4 nm could serve as an efficient probe to simultaneously enhance fluorescence imaging and magnetic resonance imaging greatly in vivo. After tail vein injection, the SPIO@DSPE-PEG/ICG NPs were found selectively accumulate at the tumor site. Encapsulation of ICG into the lipid coating of SPIO NPs results in higher photostability than free ICG due to the protection from degradation. SPIO@DSPE-PEG/ICG NPs exhibited significant photothermal cytotoxicity. Cancer cells could be killed in vitro and tumors could be ablated in vivo efficiently through photothermal effects of SPIO@DSPE-PEG/ICG NPs under laser irradiation. In summary, SPIO@DSPE-PEG/ICG NPs integrate multiple capabilities for effective tumor imaging and therapy. This is very helpful for accurately interpreting the obtained images, identifying the size and location of the tumor, as well as guiding and monitoring the photothermal therapy through a single agent.