Solid lipid nanoparticles enhance the delivery of poorly water-soluble cosmetic ingredients, improving their stability and protection. They are used in both pharmaceutics and cosmetics, as they have many advantages, such as controlled release of incorporated active ingredients, occlusive effect on the skin and improvement of penetration of active ingredients into the skin. One of the lipophilic cosmetically active ingredients that presents a challenge for incorporation into various cosmetic products is cannabidiol. Due to its wide therapeutic potential and positive effects in various skin conditions and diseases, it has also attracted attention in the field of use in cosmetics. The aim of the thesis was to produce stable solid lipid nanoparticles with cannabidiol.
First, we produced empty lipid nanoparticles with the smallest possible hydrodynamic diameter and the narrowest possible particle size distribution, which we achieved by changing the manufacturing parameters. Then, cannabidiol was incorporated into the final formulation, namely, we prepared solid lipid nanoparticles with 10% and 2% (w/w) cannabidiol. The physical stability of the nanoparticle dispersion was monitored using photon correlation spectroscopy during 8 weeks of storage at room temperature and at 4 °C. We found that the physical stability of solid lipid nanoparticles with cannabidiol was not the best, as the particle size increased greatly within 8 weeks, and the polydispersity index also increased. The worst physical stability was for the sample with 10% (w/w) cannabidiol in solid lipid nanoparticles, which was stored in a refrigerator at a temperature of 4 °C. We also evaluated the content of cannabidiol in the dispersion of solid lipid nanoparticles using high-performance liquid chromatography. Based on the findings, we can conclude that cannabidiol in formulations with 2% (m/m) and 10% (m/m) active ingredient content in solid lipid nanoparticles is chemically unstable. After 8 weeks, in the formulation of solid lipid nanoparticles with 10% (w/w) cannabidiol, we measured 79.2% of the original content of the cosmetically active ingredient when stored at room temperature and only 65.4% when stored in the refrigerator. The best chemical stability of cannabidiol was found in a formulation with 2% (w/w) cannabidiol in solid lipid nanoparticles, which was stored in a refrigerator. In this dispersion, the content was 90.2% of the original content of cannabidiol in solid lipid nanoparticles. For the same formulation, the storage stability at room temperature was much lower (60.7% of the initial content).
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