A pH-responsive CaO2@ZIF-67 system endows a scaffold with chemodynamic therapy properties

The insufficient of H2O2 restricts the efficacy of chemodynamic therapy in tumor microenvironment. Calcium peroxide (CaO2) is expected to solve this problem due to its H2O2-evolving ability. However, it prematurely decomposes in the moist air or water before reaching tumor site. In this study, zeolitic imidazolate framework-67 (ZIF-67) was in-situ grown on the surface of CaO2 to construct a pH-responsive CaO2@ZIF-67 system and then incorporated into poly-L-lactic acid (PLLA) to prepare PLLA/CaO2@ZIF-67 scaffold by selective laser sintering technology. On the one hand, ZIF-67 is used as a chemodynamic therapy agent due to the release of cobalt ions after degradation. On the other hand, ZIF-67 can serve as protective layers to prevent premature decomposition of CaO2 due to its hydrophobic properties, and then CaO2 is exposed and reacts with water to form H2O2 after the pH-responsive degradation of ZIF-67 under tumor acidic microenvironment. Results showed that the PLLA/CaO2@ZIF-67 scaffold could sustainedly produce H2O2 under acidic pH and achieve 84.64% antitumor ratio against MG-63 cells. In addition, the scaffold also promoted proliferation and osteogenic differentiation of mouse bone marrow mesenchymal stem cells due to the release of calcium ions. The prepared PLLA/CaO2@ZIF-67 scaffold with chemodynamic antitumor and osteogenic effects has great potential to treat tumorous bone defect.