Molecular structure and dynamical properties of niosome bilayers with and without cholesterol incorporation: A molecular dynamics simulation study

Niosomes are non-ionic surfactant vesicles having a bilayer structure formed by self-assembly of hydrated surfactants, usually with cholesterol incorporation. Stability and mechanical properties of niosomes strongly depend on type of non-ionic surfactants and compositions used. In this study we present the structural and dynamical properties of niosome bilayers composed of sorbitan monostearate (Span60) with 0% and 50% cholesterol compositions which are investigated by using molecular dynamics simulations. The simulations reveal that niosome bilayer without cholesterol prefer to form in the gel phase with a higher order structure, while in the presence of cholesterol the bilayer exhibits more fluidity having a less ordered structure. The niosome bilayer with 50% cholesterol inclusion shows an increase of area per lipid (similar to 11%) and thickness (similar to 39%) compared with the niosome bilayer without cholesterol. The Span60 tailgroup orientation of the niosome bilayers without cholesterol exhibits more tilt (34.5 + 0.5) than that of the bilayer with 50% cholesterol (15.4 + 0.8). Additionally, our results show that the addition of cholesterol to the bilayer causes the higher in lateral and transverse diffusion, as well as an increase in the hydrogen bond number between Span60 and water. Such characteristics not only enhance the niosome stability but also increase the fluidity, which are necessary for the niosomal drug delivery. (C) 2016 Elsevier B.V. All rights reserved.