Diffusion of organic dyes in a niosome immobilized on a glass surface using fluorescence correlation spectroscopy

Giant multilameller niosomes containing cholesterol and triton X-100 are studied using fluorescence correlation spectroscopy (FCS). Dynamic light scattering (DLS) data indicates formation of niosomes of broadly two different sizes (diameter) - ∼150 nm and ∼1300 nm. This is confirmed by field emission scanning electron microscopy (FE-SEM) and confocal microscopy. The diffusion coefficient ( D t ) of three organic dyes in the niosome immobilized on a glass surface is studied using fluorescence correlation spectroscopy. On addition of the room temperature ionic liquids (RTIL) (1-methyl-3-pentylimidazolium bromide, [pmim][Br] and 1-methyl- 3-pentylimidazolium tetra-fluoroborate, [pmim][BF 4 ]) the size of the niosome particles increases. The D t of all the organic dyes (DCM, C343 and C480) increases on addition of RTILs, indicating faster diffusion. The viscosity calculated from the D t of the three dyes exhibits weak probe dependence. Unlike lipid or catanionic vesicle, the D t values in a niosome exhibit very narrow distribution. This indicates that the niosomes are fairly homogeneous with small variation of viscosity. This work demonstrates a fluorescence correlation spectroscopic (FCS) study of organic dyes inside a niosome.