Development and characterization of curcumin loaded topical formulations

Curcuma longa L., commonly known as turmeric, is renowned for its therapeutic benefits attributed to bioactive compounds, namely curcumin and aromatic turmerone, present in its rhizome. These compounds exhibit diverse therapeutic properties, including antiinflammatory, antioxidant, and antitumor effects. However, the topical application of these compounds has a significant potential for inducing skin irritation. This study focuses on the development of Curcumin and Turmerone loaded solid lipid nanoparticles intending to reduce irritation on the skin. Solid lipid nanoparticle formulations were prepared by a method using hot homogenization followed by ultrasonication procedures and optimized by applying response surface methodology. The amounts of solid lipid Compritol® 888 ATO (glyceryl behenate) and surfactant Plantacare® 810 (capryl glucoside) were determined as independent variables and encapsulation efficiency and particle size were determined as responses. Experimental design studies were applied to all prepared formulations under the premise of determined critical parameters. It was observed that increasing the solid lipid level led to a statistically significant increase in encapsulation efficiency, while increasing the amount of surfactant positively affected the encapsulation efficiency. When the particle size was analysed, it was observed that the changes in the amount of Plantacare® 810 showed a statistically significant effect, while the changes in the amount of Compritol® 888 ATO did not show a statistically significant effect on the size. The optimized solid lipid nanoparticle formulation demonstrated high entrapment efficiencies for Curcumin and Turmerone. The obtained nanoparticles were confirmed to be spherical and uniform in shape via environmental scanning electron microscopy (ESEM) images. The in vitro release study indicated cumulative releases of 71.32 ± 3.73% for Cur and 67.23 ± 1.64% for Tur after 24 hours under sink conditions. Physical stability tests confirmed the stability of the formulation, allowing storage at 5 ± 3°C °C for a minimum of 60 days. Notably, in-vitro skin irritation studies, utilizing the reconstructed human epidermal model EpiDerm™, revealed a significant reduction in irritation with the solid lipid nanoparticle containing Curcumin and Turmerone compared to nonencapsulated Cur and Tur. These findings support the optimized solid lipid nanoparticle as a suitable carrier system for various topical uses of Curcumin and Turmerone by reducing irritation levels.