Fig. 2

ROS scavenging ability of PDA-PEG NPs. a Cytotoxicity of PDA-PEG NPs assessed by CCK-8. Free radical scavenging activities of PDA and PDA-PEG NPs were evaluated with b ABTS and c DPPH assay. d O2·⁻ was determined with ESR for detecting the ROS scavenging ability of PDA-PEG NPs in an acellular environment. e Intracellular ROS detected with a DCFH-DA probe, ×630 magnification. f Quantitative analysis of ROS-positive cells. n = 3. Symbol “**” denotes p < 0.01, NS indicates not significant