Construction,Catalytic Activity And Radiation Protection Of Cerium Nanozymes

Superoxide dismutase(SOD)is one of major antioxidants in vivo and is expected to play critical roles on the defense against reactive oxygen species(ROS)-mediated damages,such as ionizing radiation damages.Herein,inspired by the function and structure of natural SODs and cerium oxide nanozymes,two monovalent cerium-based metal organic frameworks(Ce-MOFs),CeⅢBTC and CeⅣBTC,were designed for superoxide radicals(O2·-)elimination and ionizing radiation protection.We successfully synthesized two Ce-MOFs with a single valence state by solvothermal method.The CeⅢBTC and CeⅣBTC were characterized by TEM,XPS,PXRD,FTIR,TGA and N2 adsorption experiments.Electron spin resonance(ESR)and NBT method were used to verify that CeⅢBTC and CeⅣBTC nanozymes with single valence state have the ability to selectively remove O2·-and have good SOD-like activity.Compared with CeⅢBTC,the hyper valent CeⅣBTC showed higher SOD-like activity.Electrochemical tests showed that the reduction potential of CeⅣBTC was between that of O2·-disproportionation reaction.Therefore,the reduction of O2·-catalyzed by CeⅣBTC is more favorable than CeⅢBTC thermodynamically.At the same time,CeⅣBTC can catalyze the decomposition of O2·-disproportionated product H2O2 at low pH to improve SOD-like activity.However,the low price CeⅢBTC nanozymes does not support the disproportionation of O2·-and the decomposition of H2O2.The CeⅣBTC nanozyme was selected for ionizing radiation protection studies due to its smaller size,better monodispersity,and more efficient SOD-like activity.The in vitro radioprotective effect of CeⅣBTC nanozyme was evaluated by CCK-8 assay,cloning assay,comet assay and intracellular ROS level.Then,the in vivo radioprotective effect of CeⅣBTC nanozyme was evaluated by 30-day survival assay,tissue oxidative stress level,hematopoietic system and inflammation related indicators.Finally,we investigated pharmacokinetic indices of the CeⅣBTC nanozyme and evaluated its toxicity in vivo by H&E staining of major organs,blood biochemistry,and blood routine tests.Both in vitro and in vivo results demonstrated that CeⅣBTC nanozymes could efficiently scavenge ROS,prevent cells from y-ray radiation induced cell viability decrease and DNA damages,and improve the survival rate of irradiated mice by recovering the bone marrow DNA damage and alleviating oxidative stress of tissues.The protective effect and good biocompatibility of CeⅣBTC nanozymes will enable the development of Ce-MOFs based radioprotectants and facilitate treatment of other ROS-related diseases.