A Titanium Nitride Nanozyme for pH-Responsive and Irradiation-Enhanced Cascade-Catalytic Tumor Therapy.

Nanozyme-based catalytic tumor therapy is an emerging therapeutic method with high reactivity in response to tumor microenvironments (TMEs). To overcome the current limitations of deficient catalytic activity of nanozymes, we studied the contributing factors of enzymatic activity based on non-metallic-atom doping and irradiation. Nitrogen doping significantly enhanced the peroxidase activity of Ti-based nanozymes, which was shown experimentally and theoretically. Based on the excellent NIR-adsorption-induced surface plasmon resonance and photothermal effect, the enzymatic activity of TiN nanoparticles (NPs) was further improved under NIR laser irradiation. Hence, an acidic TME-responsive and irradiation-mediated cascade nanocatalyst (TLGp) is presented by using TiN-NP-encapsulated liposomes linked with pH-responsive PEG-modified glucose oxidase (GOx). The integration of pH-responsive GOx-mediated H O self-supply, nitrogen-doping, and irradiation-enhanced enzymatic activity of TiN NPs and mild-photothermal therapy enables an effective tumor inhibition by TLGp with minimal side effects in vivo.