Do food microemulsions and dietary mixed micelles interact?

Using microemulsions (ME) as delivery vehicles requires understanding whether water-insoluble molecules are delivered by an interaction of the ME system with the dietary mixed micelles (DMM) in the small intestine to give new mixed micelles, or by alternate paths. Diluted DMM and ME systems were mixed at various weight ratios to address this question. The individual and mixed systems were characterized by physical techniques that address this interaction from different aspects. This research showed that increased DMM concentration in ME/DMM mixed systems caused: (1) increased conformational order of the acyl chains and perturbed hydrogen bonds between the ethoxylate headgroups (based on ATR-FTIR results); (2) significant increase in microviscosity (from 1.7 to 3.3 ns) (based on EPR results); (3) increased diffusivity of the surfactant molecules compared to their diffusivity in pure ME droplets, and decreased diffusivity of the taurochenodeoxycholate molecules compared to their diffusivities in pure DMM micelles (based on PGSE-NMR results); (4) formation or modification of intramolecular interactions (based on NOESY-NMR results); (5) decreased average droplet diameter and increased droplet density per unit area compared to pure ME systems (based on DLS and cryo-TEM results); and (6) fluorescence resonance energy transfer between two dyes (diphenylhexatriene and Nile Red), which were solubilized in each system separately (based on fluorescence resonance energy transfer results). These results show that DMM and ME interact to create ME–DMM mixed micelles, providing a potential pathway for delivering solubilized molecules.