Fig. 4

Catalytic mechanism and in vitro evaluation of the clusters. a Schematic illustration of the catalytic mechanism and selectivity of the clusters. Cu and Cd as single active sites exhibit superiorities against reactive oxygen species (ROS) and reactive nitrogen species (RNS) respectively, resulting in free radical scavenging and inspire their use in brain injury. b Fluorescence images of ROS (green) and O₂^·− (red) levels induced by 100 µM H₂O₂ with or without clusters treatment, illustrating the high activity of scavenging ROS of the clusters. c HT22 cell viability under treatment of H₂O₂ and treated with or without the clusters (n = 5 per group, data are presented as mean ± SD), which showed the ability of the clusters to rescue the lethality induce by H₂O₂. d, e Quantitative analysis of Au₂₅, Au₂₄Cu₁ and Au₂₄Cd₁ against O₂^·− and ROS, respectively (n = 3 independent experiments, data are presented as mean ± SD). Data are analyzed by one-way ANOVA with Tukey test (adjusted p values are shown, *p< 0.05, ***p< 0.001, compared with the Con group)