Nanostructured lipid carriers for delivery of free phytosterols: Effect of lipid composition and chemical interesterification on physical stability

The objective of this study was to develop new nanostructured lipid carrier (NLC) formulations loaded with free phytosterols (FPs) using interesterified and simple lipid phases. The simple and interesterified lipid phases were composed of soybean oil as liquid lipid and fully hydrogenated palm (HPO) and crambe (HCO) oils s solid lipids. High-pressure homogenization was the preparation method, with soy lecithin as a natural emulsifier. The characteristics of NLCs were influenced by chemical interesterification and the composition of solid lipid, mainly with respect to the fatty acid chain size. All developed FP-loaded NLCs displayed an appropriate nanoscale size from approximately 167 to 330 nm (d(32)) and appropriate physical stability with zeta potential values ranging from -29.83 to -43.70 mV after 30 days of storage. The changes observed in these parameters were influenced by the lipid phase of the NLCs and the crystallization of FP on the surface of the NLCs. FP-loaded NLCs formulated with interesterified blends displayed smaller particle size values, with less evidence of particle agglomeration and higher absolute zeta potential values than NLCs formulated with simple blends. These results indicated that NLCs developed with interesterified lipid blends were more stable than those developed with single blends NLCs produced from solid lipids with fatty acids with larger chain sizes (HCO) had larger particle sizes but were less likely to flocculate and coalesce. Thermal behavior study revealed that interesterification caused a reduction in the melting temperature and recrystallization index of the NLCs. These findings indicated decreased crystallinity and a less organized structure. This behavior favored the highest encapsulation efficiency and load capacity observed for NLCs developed with interesterified blends.