Fig. 4

PDA NPs successfully penetrated BBB to enter the brain. a Schematic illustration showing the experimental procedures for fluorescent images of mice. b Representative Cy5.5 fluorescence imaging showing the whole-body distribution of PDA NPs in mice after 2 h and 24 h of Cy5.5-PDA-SiO₂ NPs injection. c Quantification of Cy5.5 intensity in brain 2 h and 24 h after injection. d The Cy5.5 fluorescent images and e the corresponding bar graphs showing the organ distribution of PDA NPs. PBS phosphate-buffered saline, Cy5.5-PDA-SiO₂ NPs cyanine 5.5-polydopamine-silica nanoparticles