Ultrasound Enhancement of Drug Release Across Non Ionic Surfactant Vesicle Membranes

Nonionic surfactant vesicles (niosomes) have potential applications in targeted drug delivery and imaging because of their ability to encapsulate therapeutic agents and their enhanced uptake by physiological membranes. Ultrasound may be used to mediate delivery non-invasively by altering the niosome membrane structure. Niosomes composed of polyoxyethylene sorbitan monostearate (Tween 61), cholesterol, and dicetyl phosphate were synthesized via a thin film hydration technique. A fluorescing dye, carboxyfluorescein (CF), was encapsulated and used as a drug model. The amount of dye in the niosomes, the concentration of the vesicles, and their mean particle size after each 5 minute incremental exposure to ultrasound were monitored. Dye concentration encapsulated by the niosomes in the samples decreased while the population and size distribution of the niosome remained largely unchanged. Our conclusion is that ultrasound enhances the rate of dye diffusion across the niosome membrane non-destructively.