Redox-responsive dextran based theranostic nanoparticles for near-infrared/magnetic resonance imaging and magnetically targeted photodynamic therapy.

Photodynamic therapy (PDT) is a site-specific treatment of cancer using much lower optical power densities with minimal nonspecific damage to normal tissues. To improve the therapeutic efficiency of PDT, we fabricated a multifunctional theranostic nanoparticle system (DSSCe6@Fe3O4 NPs) by loading Fe3O4 nanoparticles in redox-responsive chlorin e6 (Ce6)-conjugated dextran nanoparticles for near-infrared (NIR)/magnetic resonance (MR) dual-modality imaging and magnetic targeting. The obtained DSSCe6@Fe3O4 NPs demonstrated a uniform nanospherical morphology consisting of Fe3O4 clusters. The fluorescence signal of Ce6 of this theranostic system could turn "ON" from a self-quenching state in a reductive intracellular environment. T2-Weighted MR imaging revealed a high transverse relaxivity (r2) measured to be 194.4 S-1 mM-1, confirming that it was also a distinctive contrast agent in T2-weighted MR imaging. Confocal images and flow cytometry results showed that the cellular uptake of DSSCe6@Fe3O4 NPs was enhanced effectively under an extra magnetic field, which resulted in promoted PDT therapeutic efficiency. In vivo MR imaging showed that DSSCe6@Fe3O4 NPs effectively accumulated in tumors under an extra magnetic field. These results illustrated that the DSSCe6@Fe3O4 NPs could be a promising theranostic system for both NIR/MR imaging-guided PDT precision therapy.