Effect of Lipid and Oil Compositions on Physicochemical Properties and Photoprotection of Octyl Methoxycinnamate-loaded Nanostructured Lipid Carriers (NLC).

This study aimed to evaluate the effect of solid lipid and oil structures on the physicochemical properties, kinetic release, photostability, and photoprotection of nanostructured lipid carriers (NLC) containing octyl methoxycinnamate (OMC). OMC was used as a model compound since it is an effective sunscreen agent and is widely used in sunscreen products; however, it is unstable after ultraviolet radiation (UVR) exposure. OMC-loaded NLC were prepared from different solid lipids (cetyl palmitate (CP) or tristearin) and oils (caprylic/capric triglyceride, isopropyl myristate or isononyl isononanoate) at a 4:1 ratio. After production, the particle size (z-ave) and polydispersity index (PDI) of OMC-loaded NLC ranged from 190 to 260 nm and were lower than 0.25, respectively, and the zeta potential (ZP) values were higher than |50 mV|. The Fourier transform infrared (FTIR) spectroscopy results indicated no interaction among the components. Data obtained from differential scanning calorimetry (DSC) and X-ray diffraction showed that the incorporation of oil into solid lipids disturbed the crystallinity of the lipid matrix, depending on the structure of the oil molecule. OMC loaded in tristearin-based NLC (OMC-tristearin-NLC) showed higher release of OMC than OMC loaded in CP-based NLC (OMC-CP-NLC). For photostability properties, OMC-CP-NLC prepared from isononyl isononanoate showed the highest stability owing to the less-ordered structure, providing space for accommodation of OMC, whereas the percentage of OMC remaining in tristearin-based NLC was comparable. Therefore, the degree of protection was dependent on the type of solid lipid and oil. As a result, branched-chain fatty acids provided a higher degree of disturbance than linear-chain fatty acid.