Solubilization of Span 80 Niosomes by Sodium Dodecyl Sulfate

The solubilization process of sorbitan monooleate (Span 80) niosomes, formed by sonication, by addition of the anionic surfactant sodium dodecyl sulfate (SDS) was studied in this work. The main parameters studied were the optical density at 350 nm wavelength, particle size distribution, zeta-potential, and the concentration of SDS monomers in the dispersions. Results allowed us to differentiate the stages of the solubilization process for each formulation, as well as to identify critical points of saturation by the SDS adsorbed in the bilayer, and the total niosome solubilization. The composition of these critical points turned out to be independent from time, thus allowing the construction of the pseudophase equilibrium diagram, where the lines of saturation and total solubilization of niosomes follow a linear behavior. Monomeric SDS concentration measurement corroborates the composition of the critical point of total solubilization and confirms that the niosome solubilization is a micellization process in which any amount of SDS added above critical values of total solubilization will increase the mixed micelle concentration, keeping constant the concentration of SDS monomers in solution. The results of this study shed light on further research of this biodegradable system regarding its possible use in multiple sustainable applications.