Intratumorally Injected Photothermal Agent-Loaded Photodynamic Nanocarriers for Ablation of Orthotopic Melanoma and Breast Cancer

Traditional chemotherapy of cancers may lead to serious adverse reactions due to little drug distribution in tumors. Here, a combination of photothermal therapy (PTT) and photodynamic therapy (PDT) was used for local treatment of orthotopic melanoma and breast cancer via intratumoral (i.t.) injection of photothermal agent-loaded photodynamic nanocarriers. A hydrophobic derivative of indocyanine green, DCC, was synthesized and entrapped into a pH-sensitive photosensitizer-core copolymer, PDCZP, to form DCC@PDCZP. The nanocarriers showed remarkable fluorescence, high singlet oxygen quantum yields, and a strong photothermal effect. Flow cytometry suggested that the nanocarriers were efficiently internalized by cancer cells. Near infrared thermal imaging and fluorescence self-imaging showed that the i.t. injected DCC@ PDCZP mainly remained in the tumors, but the intravenous (i.v.) nanocarriers were distributed a little. One i.t. injection of DCC@PDCZP was enough to ablate the orthotopic B16-F10 and 4T1 mouse tumors under 830 and 660 nm irradiation at 4 h postinjection. More importantly, no local recurrences were found, though swabs were formed at 9 days post-treatment. The major anticancer mechanisms included improvement of cancer cell necrosis due to hyperthermia, inhibition of neovascularization, and enhancement of cell apoptosis. The i.t. injection of PTT/PDT nanoformulations is thus a promising local treatment of superficial tumors.