Self-assembled vesicles of sodium oleate and chitosan quaternary ammonium salt in acidic or alkaline aqueous solutions

Fatty acids are anionic surfactants under their deprotonated forms, which have biodegradability and biocompatibility. The fatty acid self-assembled aggregates exhibit many potential applications. Fatty acid vesicles are the most representative because of their special hollow double-layer membrane structure. However, their application is hindered by a poor stability against variations in pH, salt, and temperature. In this work, the anionic surfactant sodium oleate (SO) and the polycationic hydroxypropyltrimethyl ammonium chloride chitosan (HACC) were mixed to form complex vesicles in a wider pH scale. The formation of vesicles was proved through TEM, fluorescence spectroscopy, and DLS; meanwhile, the intermolecular force–formed vesicles were verified through FT-IR and zeta potential analyses. The effect of electrolyte and temperature on the stability of the vesicle was also studied. The experimental results showed that with the aid of H-bonding and the electrostatic attraction separately, amphiphilic molecules were formed and they self-assembled into vesicles in both acidic and alkaline aqueous solutions.

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