Platinum-based nanocomposites loaded with MTH1 inhibitor amplify oxidative damage for cancer therapy

Photodynamic therapy (PDT) is a promising therapeutic strategy for tumor ablation by generating highly toxic reactive oxygen species (ROS) to damage DNA and other biomacromolecules. However, the local hypoxic microenvironment of the tumor and the presence of ROS-defensing system, such as the mobilization of mutt homolog 1 (MTH1) to sanitize ROS-oxidized nucleotide pool, severely limit the efficiency of PDT. Therefore, a novel tumor ablation strategy was developed that not only focused on the enhancement of ROS generation but also weakened the ROS-defensing system by inhibiting MTH1 enzyme activity. In our work, a simple one-step reduction approach was applied to enable platinum nanoparticles (Pt NPs) with catalase activity to grow in situ in the nanochannels of mesoporous silica nanoparticles (MSNs). After physical encapsulation of photosensitizer chlorin e6 (Ce6) and MTH1 inhibitor TH588, the drug loading nanoplatform was modified with an arginine-glycine-aspartic acid (RGD) functionalized liposome shell, resulting in the fabrication of amplified oxidative damage nanoplatform MSN-Pt@Ce6/TH588 @Liposome-RGD (MPCT@Li-R). The prepared MPCT@Li-R NPs could continuously catalyze the decomposition of hydrogen peroxide (H₂O₂) into oxygen (O₂) in tumor, thus promoting the generation of singlet oxygen during PDT process for improved oxidative damage of bases. Simultaneously, acid responsive released TH588 hindered MTH1-mediated scavenging of oxidative bases, further aggravating DNA oxidative damage. Consequently, this cascade therapy strategy exhibited excellent tumor suppression efficiency both in vitro and in vivo.