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) - similar to 150 nm and similar to 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][BF4]) 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.