Morphology of bile salts micelles and mixed micelles with lipolysis products, from scattering techniques and atomistic simulations

Olivia Paboisa, Rob Ziolek, Chris Lorenz, Sylvain Prévosta, Najet Mahmoud, Maximilian W. A. Skoda, Rebecca J. L. Welbourn, Margarita Valero, Richard D. Harvey, Myriam M.-L. Grundy, Peter J. Wilde, Isabelle Grillo, Yuri Gerellia, Cecile Dreiss

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)
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Abstract

Hypotheses
Bile salts (BS) are biosurfactants released into the small intestine, which play key and contrasting roles in lipid digestion: they adsorb at interfaces and promote the adsorption of digestive enzymes onto fat droplets, while they also remove lipolysis products from that interface, solubilising them into mixed micelles. Small architectural variations on their chemical structure, specifically their bile acid moiety, are hypothesised to underlie these conflicting functionalities, which should be reflected in different aggregation and solubilisation behaviour.

Experiments
The micellisation of two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), which differ by one hydroxyl group on the bile acid moiety, was assessed by pyrene fluorescence spectroscopy, and the morphology of aggregates formed in the absence and presence of fatty acids (FA) and monoacylglycerols (MAG) – typical lipolysis products – was resolved by small-angle X-ray/neutron scattering (SAXS, SANS) and molecular dynamics simulations. The solubilisation by BS of triacylglycerol-incorporating liposomes – mimicking ingested lipids – was studied by neutron reflectometry and SANS.

Findings
Our results demonstrate that BS micelles exhibit an ellipsoidal shape. NaTDC displays a lower critical micellar concentration and forms larger and more spherical aggregates than NaTC. Similar observations were made for BS micelles mixed with FA and MAG. Structural studies with liposomes show that the addition of BS induces their solubilisation into mixed micelles, with NaTDC displaying a higher solubilising capacity.
Original languageEnglish
JournalJOURNAL OF COLLOID AND INTERFACE SCIENCE
Early online date27 Oct 2020
DOIs
Publication statusE-pub ahead of print - 27 Oct 2020

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