The effect of cetyl palmitate crystallinity on physical properties of gamma-oryzanolencapsulated in solid lipid nanoparticles

Abstract

This present study was aimed at investigating the effect of the crystallinity of cetylpalmitate based solid lipid nanoparticles (SLNs) on the physical properties ofγ-oryzanol-loaded SLNs. SLNs consisting of varying ratios of cetyl palmitate andγ-oryzanol were prepared. Their hydrodynamic diameters were inthe range 210–280 nm and the zeta potentials were in the range−27 to−35 mV. The size of SLNs increased as the amount of cetyl palmitate decreased whereas no significantchange of zeta potentials was found. Atomic force microscopy pictures indicated the presenceof disc-like particles. The crystallinity of SLNs, determined by differential scanning calorimetryand powder x-ray diffraction, was directly dependent on the ratio of cetyl palmitate toγ-oryzanol and decreased with decreasing cetyl palmitate content in the lipidmatrix. Varying this ratio in the lipid mix resulted in a shift in the meltingtemperature and enthalpy, although the SLN structure remained unchanged as anorthorhombic lamellar lattice. This has been attributed to a potential inhibition byγ-oryzanol during lipid crystal growth as well as a less ordered structure of the SLNs. Theresults revealed that the crystallinity of the SLNs was mainly dependent on the solid lipid,and that the crystallinity has an important impact on the physical characteristics ofactive-loaded SLNs.