Effect of sodium deoxycholate and sodium cholate on DPPC vesicles: A fluorescence anisotropy study with diphenylhexatriene

Abstract

Effects of two bile salts, namely sodium deoxycholate (NaDC) and sodium cholate (NaC), on DPPC small unilamellar vesicles have been investigated using the steady-state fluorescence anisotropy (r ss ) of diphenylhexatriene (DPH) as a tool. It was found that the variation of r ss is sensitive enough to monitor different stages of interaction of bile salts with DPPC vesicles. NaDC induced significant changes in the membrane well below its CMC (6 mM). Even at 4 mM, which is still lower than the CMC, the phospholipids were completely solubilised by the NaDC micelles. The effect of NaC on DPPC vesicles, however, was much less significant, especially in the sub-micellar concentration regime. Being more hydrophilic NaC does not interact with the membrane efficiently. Complete solubilisation of phospholipids took place only when the concentration of NaC was above its CMC (16 mM). The experiments also showed that the bile salt-induced changes of vesicle structure were strongly dependent on the concentration of the bile salt and not on the molar ratio of lipid and bile salt.

Bile salts-containing vesicles: promising pharmaceutical carriers for oral delivery of poorly water-soluble drugs and peptide/protein-based therapeutics or vaccines

“…Based on the research published by Subuddhi & Mishra (2007), vesicles solubilization by bile salts occurs in three stages depending on bile salt concentrations. At low bile salts concentration, the surfactants partition into the lipid bilayer.…”

Spectroscopic investigation of interaction of Nile Blue A, a potent photosensitizer, with bile salts in aqueous medium

“…This is also supported by the slightly higher blue shift in the emission maximum and higher fluorescence anisotropy value of NB in NaDC than in NaC micelles. NaDC is known to form large and firm micelles that provide a relatively more hydrophobic microenvironment as compared to that of NaC to the solubilized molecules [26][27][28][29][30]32]. …”

“…They are referred to as biosurfactants taking into account their capacity to solubilize and emulsify cholesterol, bilirubin, lecithin, lipids and fat soluble vitamins in living organisms [26][27][28][29][30][31]. Apart from their biological importance, bile salts also have got much recognition as delivery systems for medicines, cosmetics and several other chemicals and are also used as membrane penetration enhancers in drug formulations [31].…”

Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

“…Compared to the membranolytic resistance of membranes with unsaturated acyl chains [59], it is observed that phospholipids with saturated acyl chains [56,92] are more easily transformed into micelles. In other words, less detergent is required for the solubilisation of saturated bilayer membranes compared to unsaturated lipid analogues.…”