Graphene oxide covalently grafted upconversion nanoparticles for combined NIR mediated imaging and photothermal/photodynamic cancer therapy

Theranostics, the integration of diagnostics and therapies, has become a new concept in the battles with various major diseases such as cancer. Here, we report a multifunctional nanoplatform, which is developed by covalently grafting core–shell structured upconversion nanoparticles (UCNPs) with nanographene oxide (NGO) via bifunctional polyethylene glycol (PEG), and then loading phthalocyanine (ZnPc) on the surface of NGO. The obtained UCNPs-NGO/ZnPc nanocomposites are not only be used as upconversion luminescence (UCL) imaging probes of cells and whole-body animals with high contrast for diagnosis, but also can generate cytotoxic singlet oxygen under light excitation for photodynamic therapy (PDT), as well as rapidly and efficiently convert the 808 nm laser energy into thermal energy for photothermal therapy (PTT). A remarkably improved and synergistic therapeutic effect compared to PTT or PDT alone is obtained, providing high therapeutic efficiency for cancer treatment. Therefore, benefiting from the unique multifunctional hybrid nanostructure, UCNPs-NGO/ZnPc nanocomposites developed herein are promising as an integrated theranostic probe for potential UCL image-guided combinatorial PDT/PTT of cancer.