Integrating Pt Nanoparticles with Carbon Nanodots to Achieve Robust Cascade Superoxide Dismutase-Catalase Nanozyme for Antioxidant Therapy

Nanozymes, nanomaterials with intrinsic enzyme mimetic activity, have emerged and been used in a broad range of applications yet are constrained with limited catalytic efficiency. Herein, by integrating carbon nanodots (CNDs) with platinum nanoparticles (PtNPs), a novel Pt@CNDs nanocomposite is engineered as an efficient nanozyme with SOD- and CAT-like specific activities of 12605 U/mg and 1588 U/mg, respectively. The PtNPs were deposited on the surface of CNDs by in situ chemical decomposition of Pt4+ to produce Pt@CNDs, in which CNDs served as a superoxide dismutase (SOD) mimic while PtNPs could mimic catalase (CAT), thereby forming a cascade antioxidant nanozyme system. Of note, the Pt@CNDs could significantly scavenge hydroxyl radical as well. The carbonyl and hydroxyl groups of CNDs could bind with PtNPs, which promotes the electron transfer between PtNPs and CNDs that endow the Pt@CNDs with excellent catalytic performance. Furthermore, Pt@CNDs could enter living cells and target mitochondria, thereby reducing the upregulated reactive oxygen species (ROS) level induced by oxidation stress. Moreover, in vivo experimental results indicated that Pt@CNDs could effectively relieve ROS-induced inflammation in living mice. This work provides a promising strategy to design nanozymes with desired catalysis activity evidence by integrating CNDs and nanometals.