Double emulsions enable in situ generation of permeation enhancers for oral delivery of macromolecules.

Oral administration of peptide therapeutics is limited by gastrointestinal degradation and poor epithelial permeability. Here, water-in-oil-in-water (W/O/W) double emulsions produced by microfluidics were designed to co-entrap octreotide and medium-chain triglycerides, enabling digestion-triggered generation of permeation-enhancing medium chain fatty acids. Synthesis parameters were systematically optimized to obtain stable, monodisperse droplets with defined core-shell morphology. The emulsions comprised an inner aqueous phase containing the payload, encapsulated within a Miglyol® 812 N oil phase stabilized by polyglycerol polyricinoleate (PGPR), and dispersed in an external aqueous phase stabilized by Tween® 80. The produced double emulsion had droplets of ∼190 μm in diameter with a single inner aqueous core of ∼78 μm. Lipolysis studies confirmed minimal fatty acid release under gastric conditions, but substantial release of caprylic (C8) and capric (C10) acids following small intestinal digestion, accompanied by release of payload. In Caco-2 monolayers, digested emulsions increased the apparent permeability (Papp) of fluorescein isothiocyanate-dextran (FD-4) and octreotide in a fatty acid concentration-dependent manner. Immunostaining showed occludin redistribution under permeation-enhancing conditions. Ex vivo studies with rat colonic mucosae mounted in Ussing chambers demonstrated a ∼ 4-fold increase in FD-4 permeability for the digested emulsions, comparable to matched concentrations of free fatty acids, while octreotide permeability remained unchanged. Coarse-grained molecular dynamics simulations revealed strong association of octreotide with mixed bile salt-fatty acid micelles, limiting its freely dissolved fraction, whereas FD-4 remained predominantly solvated, consistent with the experimental findings. This study demonstrates that digestion of structured double emulsions enables in situ generation of permeation enhancers while simultaneously releasing hydrophilic cargo, providing a formulation strategy for oral delivery of peptide therapeutics.