Compartmentalised enzyme-induced phase transformations in self-assembling lipid systems.

Area of Science:

• Biophysical Chemistry
• Materials Science
• Drug Delivery

Background:

• Optimizing drug and nutrient delivery requires understanding lipid digestion in pharmaceutical and food systems.
• Traditional pH-stat methods are unsuitable for studying individual lipid droplet interfaces.
• Existing microfluidic methods lack controlled stoichiometry for interface studies.

Purpose of the Study:

• To investigate the enzymatic digestion of lipid formulations using the internal interface of Janus droplets.
• To establish Janus droplets as a precise model for studying lipid-water interfaces.
• To explore phase transformations occurring during lipid digestion.

Main Methods:

• Janus-like droplets were created using microfluidic techniques by coalescing emulsion droplets with lipid formulation and pancreatic lipase.
• Polarized light microscopy (PLM) was employed to observe droplet morphology.
• In-situ small-angle X-ray scattering (SAXS) was used to analyze phase transformations.

Main Results:

• Enzymatic digestion induced the growth of an aligned inverse hexagonal phase (H2) within the droplets, confirmed by PLM and SAXS.
• A subsequent partial transformation from the H2 phase to an inverse bicontinuous cubic phase was observed upon introduction of simulated intestinal fluid.
• These findings suggest the diffusion of phospholipids and bile salts across the internal interface, influencing local lipid structures.

Conclusions:

• The internal interface of Janus droplets provides a precise microfluidic platform for studying lipid digestion.
• Janus droplets accurately mimic the conditions at individual lipid droplet interfaces in biological systems.
• This method enables detailed investigation of phase behavior and transformations during enzymatic digestion of lipid formulations.