Transferrin Functionization Elevates Transcytosis of Nanogranules across Epithelium by Triggering Polarity-Associated Transport Flow and Positive Cellular Feedback Loop

Overcoming
the epithelial barriers to enhance drug transport is
a focused topic for gastrointestinal, intratracheal, intranasal, vaginal,
and intrauterine delivery. Nanomedicines with targeting functionization
promote such a process owing to specific ligand–receptor interaction.
However, compared to the cell uptake of targeting nanotherapies, currently
few studies concentrate on their transcytosis including endocytosis
for “in” and exocytosis for “out”. In
fact, the cellular regulatory mechanism for these pathways as well
as the principle of ligand’s effect on the transcytosis are
almost ignored. Here, we fabricated transferrin (Tf) functionalized
nanogranules (Tf-NG) as the nanomedicine model and confirmed the difference
in polar distributions of Tf receptors (TfRs) between two epithelium
models (bipolarity for Caco-2 and unipolarity for MDCK cells). Compared
to the nonspecific reference, Tf-conjugation boosted the endocytosis
by different pathways in two cell models and transformed the intracellular
route of Tf-NG in both cells differently, affecting exocytosis, recycling,
and degradation but not the secretion pathway. Only bipolar cells
could establish a complete transport flow from “in”
to “out”, leading to the enhanced transcytosis of Tf-NG.
Importantly, epithelia could make responses to Tf-NG transcytosis.
Based on the quantitative proteomics, the intracellular trafficking
of Tf-NG altered the protein expression profiles, in which the endocytosis-
and transcytosis-related proteins were specifically upregulated. Particularly,
only bipolar cells could positively feed back to such trafficking via accelerating the subsequent Tf-NG transcytosis. Here,
all the cell transport of Tf-NG was polarity associated. In summary,
Tf modification elevated the transcytosis of Tf-NG across the epithelium
by triggering the polarity-associated transport flow and positive
cell feedback loop. These findings provided an insight into the targeting
nanodelivery for efficient transport through epithelial barriers.