Small milk-derived extracellular vesicles: suitable vehicles for oral drug delivery?

Current treatments for inflammatory bowel disease often fail due to systemic side effects, but bovine milk-derived extracellular vesicles (EVs) show promise for targeted delivery to inflamed gut tissue via the leaky gut effect. This study assessed the stability of EVs as drug carriers in simulated gastrointestinal (GI) fluids and their efficacy in a colitis mouse model. EVs were characterised after incubation in PBS at various pH levels, and their lipid bilayer stability in biorelevant GI fluids was evaluated using the polar probe laurdan. Two small molecules, acridine orange (lipophilic) and riboflavin (hydrophilic), were loaded into EVs to test their release under GI conditions, while unloaded EVs were investigated for therapeutic effect via oral gavage or rectal enema in a colitis mouse model. Although no significant changes in EVs’ physical properties were observed at different pH levels, lipid bilayer damage was evident in acidic (p ≤ 0.05) and enzyme-rich environments (p ≤ 0.01). Acridine orange release was significant (p ≤ 0.05), but riboflavin remained encapsulated, and no therapeutic effect was observed with unloaded EVs in vivo. These results suggest that physical characterisation alone does not reflect EV stability, that bovine milk EVs have limited potential for oral drug delivery and are better suited for hydrophilic drugs.