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

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 (C 8 Na 2 ), which was characterized by surface tension, proton nuclear magnetic resonance ( 1 H NMR), dynamic light scattering (DLS), transmission electronic microscopy (TEM) and fluorescence probe spectroscopy. The interaction between 12 and 6–12 and C 8 Na 2 are based on the electrostatic and hydrophobic interaction as evidenced by surface tension and 1 H NMR. The self-assembled 12-6-12/C 8 Na 2 system has been demonstrated to be concentration dependence and pH dependence. With increasing the concentration of C 8 Na 2 , the vesicle form of 12-6-12 can transform to micelles. Vesicle-to-micelle transition of the 12-6-12/C 8 Na 2 aggregates is reversible with tuning the pH values. The micropolarity inside the 12-6-12/C 8 Na 2 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.