Oxygen vacancy engineering of TiO2 nanosheets for enhanced photothermal therapy against cervical cancer in the second near-infrared window

Cervical cancer is the most common and deadly female cancer on the worldwide scale. Considering that the conventional surgery treatment and chemotherapy would cause certain side effects, photothermal therapy (PTT) possesses desired therapeutic efficiency and insignificant side effects against cervical cancer. However, the lack of efficient and safe photothermal agents that operate in the second near-infrared (NIR-II) window is a main obstacle hindering the clinical transformation of PTT. Titanium dioxide (TiO2)-based nanomaterials are commonly applied in the biomedicine field, but the weak absorption and low photothermal conversion efficiency (PCE) of TiO2 in the NIR region limit their applications in PTT. Herein, we report the oxygen vacancy engineering that is a robust strategy to regulate the electronic structures of TiO2 for photothermal conversion properties optimizing. The obtained oxygen vacancy-doped TiO2_ x nanosheets exhibit strong NIR-II absorption and high PCE owing to their decreased bandgap. Specifically, the PCE of TiO2_x nanosheets is determined to be 69.5 % in the efficient NIR-II window, which is much higher than that of widely reported PTT agents. Complete tumor recession without recurrence or pulmonary metastasis is realized by enhanced NIR-II PTT via TiO2_x nanosheets at an ultralow and safe laser exposure (0.6 W/cm2). Our findings suggest that oxygen vacancy engineering of nanomaterials could regulate their photothermal conversion performances, promoting the further application of TiO2-based nanomaterials in the biomedical.