Fig. 1

Preparation and characterization of PDA NPs. a Schematic illustration for the synthesis of PDA NPs. b Photographic and SEM images of PDA NPs (scale bar = 200 nm). c DLS analysis, d Zeta potentials analysis, and e FT-IR spectra of PDA NPs. f Photographs showing the quenching of purple-colored DPPH radicals by PDA NPs. 1: DPPH solution (0.1 mM). 2–5: the mixture DPPH solution and PDA NPs at different concentrations (10, 20, 40 and 50 μg/ml). g Bar graphs with dots showing the DPPH radical scavenging activity of PDA NPs and ascorbic acid [F (9, 20) = 136.8, P < 0.0001]. h Representative immunofluorescence images (scale bar = 200 μm) and i the corresponding bar graphs with dots showing ROS levels in the LPS-treated cells in the absence or presence of PDA NPs using DHE as the ROS probe [F (3, 8) = 68.30, P < 0.0001]. Data are presented as the means ± SEM. Results were analyzed by one-way ANOVA followed by Bonferroni test for post hoc comparisons. P < 0.05 was considered to be statistically significant. (*): P < 0.05, (**): P < 0.01 versus indicated groups; (n.s.): not significant. DA-HCL dopamine hydrochloride, PDA NPs polydopamine nanoparticles, SEM scanning electron microscope, DLS dynamic light scattering, FT-IR Fourier Transform Infrared, DPPH 2,2-Diphenyl-1-picrylhydrazyl, DHE dihydroethidium, LPS lipopolysaccharide