An Enzyme-Encapsulated MOF@MOF Nanocomposite for Detecting HO Derived From Superoxide Anion Released by Mitochondria of HeLa Cells.

In this work, a horseradish peroxidase (HRP)-encapsulated metal organic framework (MOF)@MOF nanocomposite is developed for detecting HO converted by dismutation of superoxide anions released from live HeLa mitochondria. Initially, an HRP-polyacrylic acid cluster is incorporated on a mesoporous, peroxidase-like Cu/Co-1,4-benzenedicarboxylate (BDC) MOF platform to avoid structural change and deactivation of HRP through its interactions with MOF metal ions. Additionally, a Cu/Co-BDC(HRP)@1,3,5-benzenetricarboxyate (BTC) core-shell MOF/MOF structure, also with peroxide-like properties, serves as a protective matrix for HRP. Then, ultrathin porous carbon shells (UPCS) are adopted to improve the electrical conductivity of the MOF@MOF. The Cu/Co-BDC(HRP)@BTC|UPCS sensing platform exhibits two linear ranges of 0.05-1 µM and 1-1000 µM with a sensitivity of 172 mA mM cm and 1.63 mA mM cm, respectively. A limit of detection of 0.057 µM, good selectivity and stability over 35 days for HO detection are also achieved. After treating the mitochondrial complex with specific inhibitors, amperometric results at the sensing platform confirmed complex I and III within mitochondria as the main electron leakage sites in the electron transfer chains. Therefore, this sensing platform provides a tool that may aid in predicting and even developing treatments for some oxidative stress diseases caused by mitochondrial abnormalities.