Drug-Induced Micelle-to-Vesicle Transition of a Cationic Gemini Surfactant: Potential Applications in Drug Delivery.

An impetus for the sustained interest in the formation of vesicles is their potential application as efficient drug-delivery systems. A simple approach for ionic surfactants is to add a vesicle-inducing drug of opposite charge. In ionic gemini surfactants (GSs) two molecules are covalently linked by a spacer. Regarding drug delivery, GSs are more attractive candidates than their single-chain counterparts because of their high surface activity and the effect on the physicochemical properties of their solutions caused by changing the length of the spacer and inclusion of heteroatoms therein. Herein, the effect of the (anionic) anti-inflammatory drug diclofenac sodium (DS) on the morphology of aqueous micellar aggregates of gemini surfactant hexamethylene-1,6-bis (dodecyldimethylammonium) dibromide (12-6-12) at 25 °C is reported. Several independent techniques are used to demonstrate drug-induced micelle-to-vesicle transition. These include UV/Vis spectrophotometry, dynamic light scattering, TEM, and small-angle neutron scattering. The micelles are transformed into vesicles with increasing [DS]/[12-6-12] molar ratio; precipitation of the catanionic (DS-GS) complex then occurred, followed by partial resuspension of the weakly anionic precipitate. The stability of some of the prepared vesicles at human body temperature shows their potential use in drug delivery.