Fig. 1

Characterization of HPDA nanoparticles and HPDAlR. A The scheme detailing the preparing procedure of HPDA and HPDAlR. PS powder was thoroughly mixed with dopamine aqueous solution at room temperature, with PS/PDA composite nanospheres then formed after stirring using a magnetic agitator. These composite nanospheres were centrifuged, washed and dried. The organic template was removed to obtain HPDA nanospheres. The RL-QN15 peptide was incubated with the decentralized HPDA nanoparticles, then the mixture was centrifuged and the supernatants were discarded and the rests were considered as HPDAlR. B TEM image of HPDA nanoparticles. HPDA particles with an average diameter of 52 nm showed well-defined spherical morphologies and hollow structures. Scale bar (200 nm) was indicated by a line in the bottom-left corner of Figure. C EDX analysis of HPDA nanoparticles revealed a uniform distribution of C, N, and O elements, which implied the formation of HPDA nanoparticles. The scale bar (50 nm) was indicated by lines in the bottom-left corner of in Figures. D Nitrogen adsorption–desorption isotherms of HPDA nanoparticles. E Pore size distribution of HPDA nanoparticles. F FTIR analysis of HPDA (black line) and HPDAlR (red line). By the loading of RL-QN15, peaks at 3 417.34 cm⁻¹ and 1 637.69 of HPDA were shifted to 3381.45 cm⁻¹ and 1629.42 cm⁻¹. G XPS analysis of HPDA (black line) and HPDAlR (red line). After the loading of RL-QN15, compared with the HPDA, a weak S2_P signal peak appeared in the HPDAlR sphere spectrum. H Loading efficiency of HPDA against RL-QN15. The data were displayed as Mean ± SD, n = 4. I Slow-releasing efficiency of HPDAlR against RL-QN15. The data were displayed as Mean ± SD, n = 4