Self-assembly of triglyceride nanocrystals in suspension

The interparticle interactions in aqueous monoacid triglyceride nanosuspensions prepared by melt homogenization are strongly influenced by the thickness distribution of the platelet-shaped particles. Small-angle X-ray scattering and transmission electron microscopy investigations on the native, undiluted tripalmitin dispersions stabilized with phospholipids and sodium glycocholate indicate that the dispersed nanocrystals can form aggregates of particles which are oriented in the same direction (stacked lamellae) with interparticle distances around 20 nm. The relative concentration of the particles in the stacks increases with the total triglyceride concentration in a dispersion. The stacked lamellae almost disappear after dilution with the aqueous phase or by increasing the temperature just below the onset of melting of the tripalmitin nanocrystals. This observation indicates that the energy gained by the formation of a stack is of the order of k(B)T. The tendency to form stacked lamellae is reduced for trimyristin and even more for trilaurin suspensions, despite the fact that they also contain platelet-shaped nanocrystals.