Apical-to-basolateral exchange across endothelial monolayer of fluorescent Aβ42 (FAM-labeled Human β-Amyloid (1-42) and Fluor ? 488-labeled β-Amyloid (1-42)) or scramble Aβ42 ( FAM-labeled scrambled β-Amyloid (1-42) ) (1-100 μM) is monitored in transendothelial electrical resistance (TEER) during cell monolayer’s formation over time (over 120?min in presence or absence of Aβ24). Human β-Amyloid (1-24) (1 μM) results in H-Aβ42 retention, thus reducing its efflux through the BBB and therefore preventing an efficient mechanism of Aβ42 clearance[1].The in vitro BBB model is used to investigate the passage of FAM-labeled or 488-conjugated H-Aβ42 across the endothelial cell monolayer.?The addition of fluorescently labeled H-Aβ42 (FAM-labeled Human β-Amyloid (1-42) or Fluor ? 488-labeled β-Amyloid (1-42)) to the apical side of cell inserts results in effective BBB crossing, FAM-labeled scrambled β-Amyloid (1-42) is not efficiently transcytosed.