(a) Illustration of the construction of the transwell model to evaluate the potential contribution by the microglia. The AuNCs were always incubated with the cells on the BV-2 cells side, while the post-passage AuNCs were detected on the opposite. The single bEnd.3 cells layer in transwell model were set as control. The permeability of the AuNC@BSA (b) and AuNC@GSH (c) under the condition of with or without BV-2 cells, post 4 or 24 h of incubation. (d) The confocal images of the bEnd.3 and BV-2 cells after incubation with CFSE-labelled AuNCs, the nuclei were showed in blue, red indicated the AuNCs that were just phagocytosed, and the green signal demonstrated the AuNCs that located close to the cytoplasm membrane for subsequent exocytosis, bars represent 5 μm. The TEM captures showed BV-2 cells with sufficient exosomes for the trafficking of AuNC@BSA (e) and AuNC@GSH (f). The arrows indicate the numerous exosomes secreted by the cells. The amplified pictures showed the multivesicular bodies inside the cells, secreted exosomes and the cargo in the exosomes, respectively.