Biodegradable titanium nitride MXene quantum dots for cancer phototheranostics in NIR-I/II biowindows

As a prominent member of two dimensional (2D) materials, MXenes have shown encouraging photophysical properties and so there is highly desirability to explore their phototherapeutic potential in cancer. Herein, we demonstrate a facile top-down strategy for the synthesis of nitride-based MXene, titanium nitride quantum dots (Ti2N QDs) in solution. With a size of around 5 nm, the obtained Ti2N QDs exhibit extraordinarily high photothermal conversion efficiency under laser irradiation in both first and second near-infrared (NIR) biowindows (NIR-I, 808 nm, 48.62%; and NIR-II, 1064 nm, 45.51%). In vitro and in vivo assessments demonstrate that the Ti2N QDs possess excellent biocompatibility, photoacoustic (PA) effect, and photothermal therapy (PTT) efficiency. Moreover, the Ti2N QDs showing obvious aggregation in tumors after 4 h post-injection, which enables facilitate PA imaging-guided PTT in both NIR-I/II biowindows without noticeable toxicity. Encouragingly, the Ti2N QDs with appropriate degradation property also show an applicable excretion rate from the body in vivo, which ensures sufficient stability in circulation to accomplish therapeutics roles and then can be smoothly discharged from the body after that. These results indicate the high potential of biodegradable Ti2N QDs in PA imaging-guided PTT in both NIR-I/II biowindows for precision cancer treatment.