Bulk and dispersed aqueous behaviour of an endogenous lipid, selachyl alcohol: Effect of Tween 80 and Pluronic F127 on nanostructure

Tween 80 has been reported to provide a means of targeting drug nanocarriers to the blood- brain barrier. This study investigated the influence of addition of Tween 80 on the formation of different bulk and dispersed lyotropic liquid crystalline phases in selachyl alcohol-based systems. The effect of increasing concentrations of Tween 80 and Pluronic F127 (as a control) (0–25% w/w relative to SA) on the bulk phase behaviour and dispersions of selachyl alcohol (SA) were investigated using small angle X-ray scattering, dynamic light scattering, and cryogenic transmission electron microscopy. The addition of Tween 80 to SA bulk phase samples triggered concentration-dependent phase changes with the structure sequentially evolving from a reverse hexagonal phase (H₂) to a mixed H₂ and inverse bicontinuous cubic (V₂) then a V₂ phase alone. In contrast, the addition of Pluronic F127 resulted in a phase change from H₂ phase to a mixed lamellar and H₂ phase system. The mean particle size of internally structured particles was 125–190 nm with low polydispersity indices (0.1–0.2). Nanoparticles retained the bulk phase internal structure in the presence of Tween 80, whereas in the presence of Pluronic F127, the additional lamellar phase that formed in bulk phase systems was not observed. Cryo-TEM revealed the formation of cubosomes and hexosomes by SA in excess water in the presence of Tween 80 and Pluronic F127 respectively. In summary, it was shown that stabilisation of SA dispersions using Tween 80 resulted in a decrease in negative curvature leading to a change in internal structure from H₂ to V₂ phase. The studies provide the core understanding of particle structure to progress these structured lipid nanocarriers into delivery studies with Tween 80 as a mechanism to target the blood-brain barrier.