Ru@CeO yolk shell nanozymes: Oxygen supply in situ enhanced dual chemotherapy combined with photothermal therapy for orthotopic/subcutaneous colorectal cancer.

Hypoxia is an important factor in forming multidrug resistance, recurrence and metastasis in solid tumors. Nanozymes respond to tumor microenvironment for tumor-specific treatment is a new and effective strategy. In this study, one-pot method was used to synthesize hollow Ru@CeO yolk shell nanozymes (Ru@CeO YSNs), which possess excellent light-to-heat conversion efficiency and catalytic performance. Antitumor drug ruthenium complex (RBT) and resveratrol (Res) were dual-loaded in Ru@CeO YSNs, and a double outer layer structure using polyethylene glycol was constructed to form dual-drug delivery system (Ru@CeO-RBT/Res-DPEG) that was released on demand. The double outer layer structure increased the biocompatibility of Ru@CeO YSNs and effectively prolong the circulation time in blood. Ru@CeO-RBT/Res-DPEG catalyzes endogenous HO to produce oxygen, which achieve in situ oxygen supply and enhanced dual-chemotherapy and photothermal therapy (PTT) for colorectal cancer. In vitro studies found that Ru@CeO-RBT/Res-DPEG has good tumor penetration depth and antitumor effect. In addition, Ru@CeO-RBT/Res-DPEG can alleviate tumor hypoxia, and inhibit metastasis and recurrence of orthotopic and subcutaneous colorectal cancer. Accordingly, the study shows that yolk shell nanozymes can be used as an efficient synergistic system for dual-chemotherapy and PTT to kill tumor and inhibit orthotopic colorectal cancer metastasis and recurrence.