Antioxidant Evaluation of PDA-PEG Nanoparticles

The antioxidant activities of PDA-PEG NPs in water and organic solvent were evaluated by ABTS and DPPH assay, respectively. A total antioxidant capacity assay kit with a rapid ABTS method was purchased from Beyotime Biotechnology (China). The green ABTS^•+ could be catalyzed to form ABTS in the presence of antioxidants. The degree of discolouration was quantified as a drop in the absorbance of 734 nm [61 (link)]. The antioxidant activities of PDA-PEG NPs were calculated referring to Trolox, which was used as a standard. DPPH (Nanjing Jiancheng Bioengineering Institute, China) was dissolved in 80% methanol. PDA and PDA-PEG NPs at various concentrations (0, 25, 50, and 100 µg/ml) were mixed with 100 µL DPPH solution and incubated for 30 min in the dark. The absorbance of reaction mixtures was detected at a wavelength of 517 nm. The radical scavenging activity was calculated referring to a previous study [62 (link)].