Electron transition materials on the basis of transition metal ions usually possess higher photothermal transduction efficiency but lower extinction ability, which have not been considered as efficient photothermal agents for therapeutic applications. In this work, we demonstrate a facile and feasible approach for enhancing 808 nm photothermal conversion effect of d orbits transition Cu(II) ions by forming Cu-carboxylate complexes. The coordination with carboxylate groups greatly enlarges the splitting energy gap of Cu(II) and the capability of electron transition, thus enhancing the extinction ability in near-infrared region. The cupreous complexes are further loaded in biocompatible and biodegradable polymer nanoparticles (NPs) of chitosan to temporarily lower the toxicity, which allows the photothermal therapy of human oral epithelial carcinoma (KB) cells in vitro and KB tumors in vivo. Animal experiments indicate the photothermal tumor inhibition rate of 100%. In addition, the gradual degradation of chitosan NPs leads to the release of cupreous complexes, thus exhibiting additional chemotherapeutic behavior in KB tumor treatment. Onefold chemotherapy experiments indicate the tumor inhibition rate of 93.1%. The combination of photothermal therapy and chemotherapy of cupreous complex-loaded chitosan NPs indicates the possibility of inhibiting tumor recurrence.
Keywords: chemotherapy; chitosan; cupreous complexes; nanocomposites; photothermal therapy.