Three-dimensional covalent organic frameworks as enzyme nanoprotector: preserving the activity of catalase in acidic environment for hypoxia cancer therapy

Utilizing catalase (CAT) to in situ catalyze the O2 generation in tumor tissue will significantly ameliorate tumor hypoxia. However, the acidic tumor microenvironment will cause CAT obviously lose its activity, attenuating its effect on hypoxia ameliorating. Herein, we reported a porphyrin-based three-dimensional covalent organic framework as the enzyme nanoprotector to immobilize CAT and provide pH-protectability to maintain its enzyme activity under acidic conditions. The three-dimensional covalent organic framework exhibits a high surface area to load CAT and is proposed to adopt a 2-fold interpenetrated pts topology with Pmc21 space group. Under laser irradiation, the nanoprotector could high-efficiently generate reactive oxygen species and realize photodynamic therapy (PDT) of cancer. CAT catalyzes the excessive H2O2 in the tumor tissue decomposition to generate O2 for PDT even at acidic tumor microenvironment, greatly enhancing PDT efficacy. The nanoprotector exhibits high tumor suppression efficiency, which provided a comprehensive consideration for using CAT in cancer therapy.