NONIONIC SURFACTANT BASED ORGANOGELS INCORPORATING NIOSOMES

A novel anhydrous organogel was formulated as a potential delivery veh icle from a solution of two non-ionic surfactants, sorbitan monosteara te (Span 60) and polyoxyethylene sorbitan monolaurate (Tween 20), in h exadecane at 60 degrees C, which cools to a white, semi-solid, thermor eversible gel at room temperature. The gel comprises microscopic ''clu sters'' of tubules and fibrils dispersed in the organic medium, as rev ealed by optical microscopy. The addition of an aqueous phase (water o r niosome suspension) up to 17% v/v to the oil phase at 60 degrees C p roduces water-in-oil (w/o) and vesicle-in-water-in-oil (v/w/o) systems , respectively. On cooling, the oil phase of these emulsions gels and surfactants rods, fibrils and some distorted droplets are observed. Th e release rate of hydrophilic solute from these gels was found to be l owest when a disperse system of spherical water droplets in the contin uous oil phase is formed at high temperatures, compared to the faster release from the gel where the fibril structures act as nearly continu ous aqueous channels running through the organic medium, providing a m eans of traversing the oil phase.