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 (Ti 2 N QDs) in solution. With a size of around 5 nm, the obtained Ti 2 N 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 Ti 2 N QDs possess excellent biocompatibility, photoacoustic (PA) effect, and photothermal therapy (PTT) efficiency. Moreover, the Ti 2 N 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 Ti 2 N 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 Ti 2 N QDs in PA imaging-guided PTT in both NIR-I/II biowindows for precision cancer treatment.