Effect of Ouratea sp. butter in the crystallinity of solid lipids used in nanostructured lipid carriers (NLCs)

Abstract

The aim of this work was to evaluate the effect of Ouratea sp. butter (OB) on crystallinity of solid lipids used in nanostructured lipid carriers systems. Firstly, the composition of fatty acids in OB was evaluated by transesterification reaction for gas chromatography fatty acid methyl ester analysis. The solid lipids such as stearic acid (SA), beeswax (BW) and carnauba wax (CW) were submitted to recrystallization process (heating–cooling). Moreover, binary mixtures between solid lipids and OB were prepared in ratio 1:1 (w/w) by heating of the components above the melting point followed by cooling at room temperature. Thus, the samples were characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), X ray diffraction (XRD) and hot-stage polarized optical microscopy (HSPOM). DSC curves showed a shift of the melting point to lower temperatures in the lipid mixtures with OB. TG data suggested a thermal stability reduction in the lipid mixtures containing SA and CW and an increase thermal stability in the mixture containing BW. XRD data confirmed DSC results, showing a reduction in intensity of main diffraction peaks of the lipid mixtures and a presence of the amorphous portion in angle 2θ: 22°. Finally, HSPOM demonstrated that the microstructures of solid lipids decreased in size and thickness in the mixtures containing OB at room temperature and slightly before the melting point, confirming previous characterizations. These results suggest that lipid mixtures with OB present a lower crystallinity, and it is expected that amorphous portion facilitates drug incorporation, for example.