Transcellular Transport of HDL Bearing Gold Nanoparticles Across the Blood Brain Barrier

The overall objective of this study was to develop a HDL-based multifunctional platform for transport and delivery of highly hydrophobic gold nanoparticles (AuNP) bearing photothermic properties across the blood brain barrier (BBB). We exploited the ability of apolipoprotein E3 (apoE3) to act as a high affinity ligand for the low-density lipoprotein receptor to gain entry into endothelial and glioblastoma cells. The issue of poor aqueous solubility of AuNP of varying diameters (3, 10, or 10 nm) was overcome by integrating them with phospholipids and apoE3, yielding reconstituted rHDL bearing AuNP (rHDL-AuNP). Transmission electron microscopy (TEM) revealed the presence of AuNP embedded in spherical particles. Incubation of human brain microvasculature endothelial cells or glioblastoma cells with rHDL-AuNP bearing unlabeled or FITC-labeled apoE3 revealed robust uptake of particles that were localized in endocytic/lysosomal vesicles. The transport of rHDL-AuNP across an in vitro BBB model developed from primary porcine endothelial cells was examined. The addition of rHDL-AuNP to the luminal side of the cells did not affect the integrity of the BBB as assessed by the localization of key tight junction markers such as occludin, claudins and ZO-1 by immunofluorescence, and, by continual measurement of the transepithelial electrical resistance by impedance spectroscopy under physiological conditions. Lastly, the appearance of fluorescein fluorescence and AuNP in the abluminal side suggested transport of rHDL-AuNP across the neurovascular junction. These findings demonstrate that rHDL bearing apoE3 acts as a detergent in solubilizing and dramatically improving the aqueous solubility of AuNP, facilitates cellular uptake and transcellular transport of rHDL-AuNP across endothelial cells. They are significant since they present rHDL bearing apoE3 as an effective platform for delivering AuNP across the BBB.