Uptake of silica particulate drug carriers in an intestine-on-a-chip: towards a better in vitro model of nanoparticulate carrier and mucus interactions.

Micro and nano-particulate carriers have potential to increase bioavailability of oral drugs, but must first overcome the mucus barrier of the intestinal epithelium to facilitate absorption and entry to systemic circulation. We report on mucus-silica nanoparticulate carrier interactions in an in vitro intestine-on-a-chip (IOAC) microfluidic model. Caco-2 cells cultured within the IOAC model recapitulate the morphology of the human intestinal epithelium that is currently lacking in traditional static Transwell models. Fine control over the cell culture conditions produced a mucus layer, previously problematic to achieve without employing cell co-culture. The microdevice design also allowed for direct imaging of silica particulate carrier (40-700 nm) uptake through the mucus and cellular monolayer. PEGylated particulate carriers penetrated more readily through the mucus layer compared to non-PEGylated particulate carriers while larger particulate carriers tended to retard particulate carrier penetration through a dense mucus mesh. This was confirmed via imaging flow cytometry and UV-fluorescence spectroscopy. The IOAC also demonstrated the ability to mimic intestinal peristaltic fluidic conditions, which in turn affects the particulate carrier uptake. This in vitro IOAC model has potential to directly elucidate mucus interactions and uptake mechanisms for a range of drug carrier systems.