A new green titania with enhanced NIR absorption for mitochondria-targeted cancer therapy

A new kind of green titania (G-TiO_2-x) with obvious green color was facilely synthesized from black titania (B-TiO_2-x) through subsequently strong ultrasonication. Comparatively, this stable G-TiO_2-x shows much enhanced near infrared (NIR) absorption, especially around 920 nm, which can be ascribed to the obvious change of TiO_2-x lattice order owing to the effect of ultrasonication. This feature enables G-TiO_2-x to be stimulated with 980 nm laser in the combined photodynamic therapy (PDT) and photothermal therapy (PTT), which is greatly beneficial for improving tissue penetration depth. Furthermore, since mitochondria are preferred subcellular organelles for PDT/PTT, G-TiO_2-x was further designed to conjugate with triphenylphosphonium (TPP) ligand for mitochondria-targeted PDT/PTT to obtain precise cancer treatment. Attributing to the high mitochondria-targeting efficiency and simultaneously synergistic PDT/PTT, high phototherapeutic efficacy and safety with a much lower laser power density (980 nm, 0.72 W c_m-2) and low materials dosage were achieved both in vitro and in vivo. In addition, negligible toxicity was found, indicating high biocompatibility. This novel G-TiO_2-x could provide new strategies for future precise minimal/non-invasive tumor treatment.