Magnetite nanocluster@poly(dopamine)-PEG@ indocyanine green nanobead with magnetic field-targeting enhanced MR imaging and photothermal therapy in vivo.

Multifunctional nanomaterials with the magnetic resonance imaging (MRI) guided tumor photothermal ablation ability have been extensively applied in biomedical research as one of the most exciting and challenging strategies for cancer treatment. Nevertheless, most of these nanomaterials still suffer from low accumulation in tumor tissues and insufficient photothermal ablation of tumors so far. Here, we report a novel approach to overcome these limitations using a core-shell magnetite nanocluster@poly(dopamine)-PEG@ICG nanobead compositing of magnetite nanocluster core with coating of poly(dopamine), then further conjugating with polyethylene glycol (PEG) and adsorbing indocyanine green (ICG) on the surface. The adsorbed ICG in the nanobead displays a higher photostability and photothermal conversion ability than free ICG, as well as additional photothermal effect rather than magnetite nanocluster and poly(dopamine), which endow the nanobead with enhanced photothermal killing efficiency against cancer cells under near-infrared (NIR) laser irritation. Furthermore, it is proved that these nanobeads have excellent biocompatibility, T2-weighted MR imaging and magnetic field targeting ability. By applying an external magnetic field (MF) focused on the targeted tumor, a magnetic targeting mediated enhanced accumulation is observed at tumor site as proved by a darker T2-weighted MR image. Utilizing the magnetic targeting strategy, enhanced photothermal tumor ablation was achieved under laser irradiation in vivo, which is reflected by the degree of tumor tissue damage and tumor growth delay. Therefore, this nanobead integrates the abilities of magnetic field-targeting, MR imaging and photothermal cancer therapy, and might be a promising theranostic platform for tumor treatment.