APP and Alzheimer disease: As shown in Figure 7 and the time-lapse movies (Movies S1 and 2), AD mouse brain showed bare autofluorescence in the NIR region before administration of probe 9; however, after injection of probe 9, bright NIR fluorescence could be immediately observed in the blood vessels and brain parenchyma of the APP/PS1 mouse, suggesting that probe 9 could rapidly cross the BBB and enter the parenchyma.