Yeast‐derived vacuoles as a novel carrier with enhanced hCMEC/D3 cell monolayer penetration

Abstract The blood–brain barrier (BBB) is a brain protection structure that restricts drug delivery from the blood to the central nervous system. Thus, we developed a novel drug carrier using yeast vacuoles to overcome this problem. The purpose of this study was to assess the drug transportability of yeast vacuoles using a human cerebral microvascular endothelial cell line (hCMEC/D3) cell monolayer. Here, we used daunorubicin (DNR) as a microtubule‐targeting agent with the ability to disaggregate pre‐formed fibrils and prevent Tau fibrillization. An in vitro model was developed by culturing hCMEC/D3 cells on Transwell inserts in EBM‐2 endothelial basal medium until the cells formed a monolayer. Next, nano‐sized yeast vacuoles were loaded with DNR, and the signals inside and outside the hMEC/D3 cell monolayer were detected using the GloMax ® Explorer fluorometer. DNR penetrated the cell monolayer and was regulated by endocytosis via receptor‐mediated macropinocytosis on the surface of the cell. Confocal imaging showed a significant increase in intracellular DNR fluorescence when the cells were treated with the vacuole‐encapsulated drug. These results indicate that the drug penetrated the hCMEC/D3 cell monolayer via encapsulation into the vacuoles. Overall, yeast‐derived vacuoles are promising candidates as drug carriers to the brain.