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 was engineered as an efficient nanozyme with superoxide dismutase (SOD)- and catalase (CAT)-like specific activities of 12,605 U/mg and 3172 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 SOD mimic while PtNPs could mimic CAT, thereby forming a cascade antioxidant nanozyme system. Of note, the Pt@CNDs could significantly scavenge hydroxyl radicals as well. The carbonyl and hydroxyl groups of CNDs could bind with PtNPs, which promoted the electron transfer between PtNPs and CNDs that endowed 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. 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.