Defect-rich titanium nitride nanoparticle with high microwave-acoustic conversion efficiency for thermoacoustic imaging-guided deep tumor therapy

Pulse microwave excite thermoacoustic (TA) shockwave to destroy tumor cells in situ. This has promising applications for precise tumor therapy in deep tissue. Nanoparticle (NP) with high microwave-acoustic conversion is the key to enhance the efficiency of therapy. In this study, we firstly developed defect-rich titanium nitride nanoparticles (TiN NPs) for pulse microwave excited thermoacoustic (MTA) therapy. Due to a large number of local structural defects and charge carriers, TiN NPs exhibit excellent electromagnetic absorption through the dual mechanisms of dielectric loss and resistive loss. With pulsed microwave irradiation, it efficiently converts the microwave energy into shockwave via thermocavitation effect, achieving localized mechanical damage of mitochondria in the tumor cell and yielding a precise antitumor effect. In addition to the therapeutic function, the NP-mediated TA process also generates images that provide valuable information, including tumor size, shape, and location for treatment planning and monitoring. The experimental results showed that the TiN NPs could be efficiently accumulated in the tumor via intravenous infusion. With the deep tissue penetration characteristics of microwave, the proposed TiN-mediated MTA therapy effectively and precisely cures tumors in deep tissue without any detectable side effects. The results indicated that defect-rich TiN NPs are promising candidates for tumor therapy.