Fabrication of pH-responsive system based on cationic gemini surfactant/sodium octanedioate and its application on controlled release of paclitaxel

Abstract

A pH-responsive surfactant system has been self-assembled between a cationic gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and sodium octanedioate (C8Na2), which was characterized by surface tension, proton nuclear magnetic resonance (1H NMR), dynamic light scattering (DLS), transmission electronic microscopy (TEM) and fluorescence probe spectroscopy. The interaction between 12 and 6–12 and C8Na2 are based on the electrostatic and hydrophobic interaction as evidenced by surface tension and 1H NMR. The self-assembled 12-6-12/C8Na2 system has been demonstrated to be concentration dependence and pH dependence. With increasing the concentration of C8Na2, the vesicle form of 12-6-12 can transform to micelles. Vesicle-to-micelle transition of the 12-6-12/C8Na2 aggregates is reversible with tuning the pH values. The micropolarity inside the 12-6-12/C8Na2 aggregates was characterized by fluorescence spectroscopy using pyrene as probe, indicating that the micropolarity is enhanced with the increased pH. Furthermore, the release assay of an oil-soluble drug paclitaxel performs well in this pH-responsive surfactant system and the drug releasing rate could be controlled by pH values.