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A focus on critical aspects of uptake and transport of milk-derived extracellular vesicles across the Caco-2 intestinal barrier modelRoerig, Josepha, Schiller, Laura, Kalwa, Herrmann, Hause, Gerd, Vissiennon, Cica, Hacker, Michael C., Wölk, Christian, Schulz-Siegmund, Michaela 10 October 2022 (has links)
Bovine milk-derived extracellular vesicles (EVs) hold promises as oral drug delivery systems. Since EV
bioavailability studies are difficult to compare, key factors regarding EV uptake and intestinal
permeability remain little understood. This work aims to critically study uptake and transport
properties of milk-derived EVs across the intestinal barrier in vitro by standardization approaches.
Therefore, uptake properties were directly compared to liposomes in intestinal Caco-2 cells. Reliable
staining results were obtained by the choice of three distinct EV labeling sites, while non-specific dye
transfer and excess dye removal were carefully controlled. A novel fluorescence correction factor was
implemented to account for different labelling efficiencies. Both EV and liposome uptake occurred
mainly energy dependent with the neonatal Fc receptor (FcRn) providing an exclusive active pathway
for EVs. Confocal microscopy revealed higher internalization of EVs whereas liposomes rather
remained attached to the cell surface. Internalization could be improved when changing the liposomal
formulation to resemble the EV lipid composition. In a Caco-2/HT29-MTX co-culture liposomes and EVs
showed partial mucus penetration.
For transport studies across Caco-2 monolayers we further established a standardized protocol
considering the distinct requirements for EVs. Especially insert pore sizes were systematically
compared with 3 µm inserts found obligatory. Obtained apparent permeability coefficients (Papp)
reflecting the transport rate will allow for better comparison of future bioavailability testing.
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