Manganese-Doped Hollow Cerium Oxide Nanozyme as a Potent Cigarette Smoke Purifier for Vapor-Phase Reactive Oxygen Species Scavenging

Tobacco smoke-induced lung disease remains a major global health threat. Reactive oxygen species (ROS) present in cigarette smoke including superoxide (^•O₂^-), hydroxyl radicals (^•OH), and hydrogen peroxide (H₂O₂) contribute substantially to oxidative injury, yet conventional acetate filters are ineffective at removing these gaseous free radicals. Here, we report manganese-doped hollow cerium oxide (Mn-CeO₂) nanospheres as robust antioxidative nanozymes for scavenging gas-phase ROS. Mn-CeO₂ exhibits enhanced superoxide dismutase (SOD)-like, catalase (CAT)-like activities and superior ^•OH scavenging compared with undoped CeO₂. After being filled into a commercial cigarette filter, Mn-CeO₂ removed over 56.2% of targeted ROS from smoke under our test conditions. In a mouse passive-smoking model, cigarette filters filled with Mn-CeO₂ markedly reduced pulmonary inflammation and histological lung injury relative to the controls. Serum biochemical markers showed no significant systemic toxicity. Our research demonstrates that manganese doping significantly improves the ROS scavenging performance of CeO₂ nanozymes and suggests a feasible route to reduce cigarette smoke-derived oxidative damage.