Aqueous sodium dehydrocholate-sodium deoxycholate mixtures at low concentration.

Area of Science:

• Colloid and Surface Science
• Biophysical Chemistry
• Surfactant Systems

Background:

• Bile salts, such as sodium dehydrocholate (NaDHC) and sodium deoxycholate (NaDC), are amphipathic molecules crucial for biological processes.
• Understanding their behavior in mixed systems is vital for applications in drug delivery and formulation.
• The self-assembly and interfacial behavior of these bile salts in solution are complex and influenced by their molecular structure.

Purpose of the Study:

• To investigate the behavior of sodium dehydrocholate (NaDHC)-sodium deoxycholate (NaDC) mixed systems.
• To characterize the interactions within mixed micelles and at the air-solution interface.
• To elucidate the role of molecular structure in the non-ideal behavior of these bile salt systems.

Main Methods:

• Utilized a battery of methods to study monomers, micelles, and mixed systems.
• Applied Rubingh's model to analyze mixed micellar behavior.
• Investigated bile salt behavior in mixed monolayers at the air-solution interface.

Main Results:

• Micellar interactions were repulsive when aggregates were rich in NaDHC.
• Inclusion of NaDC induced structural transformation and attractive interactions in micelles.
• Mixed monolayers were monotonically rich in NaDC, forming stable and compact adsorbed layers.
• Interactions in both micelles and monolayers deviated from ideal behavior.

Conclusions:

• The non-ideal behavior of NaDHC-NaDC mixed systems in both micelles and monolayers is attributed to structural factors within their hydrocarbon backbones.
• Bile salt composition significantly influences aggregate structure and interaction type (repulsive vs. attractive).
• Mixed monolayers exhibit enhanced stability and compactness, driven by NaDC enrichment.