Fig. 1

Preparation and characterization of blank NPs and RBA-NPs. a Schematic illustration of the preparation and therapeutic mechanism of RBA-NPs against RA. b The chemical structure and molecular weight of RBA. c, d TEM images showed that the blank NPs and RBA-NPs were roughly spherical with uniformed size. e, f The particle sizes of blank NPs and RBA-NPs were about 174.2 nm and 249.4 nm as measured by DLS. g, h The zeta potentials of blank NPs and RBA-NPs were −19.9 mV and −17.6 mV, respectively. i The in vitro release of RBA from RBA-NPs at different conditions (pH = 5.0, 6.8 or 7.4) in 72 h. j Stability of RBA-NPs at different conditions (pH = 5.0, 6.8 or 7.4) in 24 h