Influence of cosurfactant on the behavior of structured emulsions under simulated intestinal lipolysis conditions

Abstract

Structured emulsion-based delivery systems, fabricated from natural lipids and polymers, are finding increasing use to control the biological fate of ingested lipids within the gastrointestinal tract. The purpose of this study was to elucidate the impact of cosurfactants on the digestion behavior of structured emulsions using a simulated intestinal lipolysis model. Lipid droplets were first prepared by membrane homogenization using a globular protein (β-lactoglobulin) as the primary surfactant, and a non-ionic surfactant (Tween 20) as the cosurfactant. The structured emulsion was fabricated by mixing lipid droplets (+), alginate solution (−), and subsequently chitosan solution (+). With an outer chitosan coating, the electrical charge on the structured emulsion droplets changed from positive to negative when the pH was varied from 2 to 7.5 both in the absence and presence of cosurfactant. However, the particle size was much smaller in the presence of the cosurfactant. The rate and extent of lipid digestion under simulated intestinal lipolysis conditions were influenced by cosurfactant, interfacial structure, and digestion conditions (fasted versus fed). Under high calcium fed conditions (20 mM Ca2+), lipid digestion was highly suppressed and delayed in delivery systems containing cosurfactant and chitosan, which was similar to the system containing alginate but no cosurfactant. This reduction in lipid digestion could be largely overcome by including cosurfactant in the delivery systems. The information obtained in this study may prove useful in designing oral delivery systems that control the digestion and release of lipids in the gastrointestinal tract.