Curcumin Nanoemulgel: Characterization, Optimization, and Evaluation of Photoprotective Efficacy, Anti-Inflammatory Properties, and Antibacterial Activity

As a natural bioactive compound, curcumin (Cur) has traditionally used for various therapeutic purposes, but due to low solubility, poor skin permeability, and the possibility of superficial staining, its topical applications is restricted. Thus, this study aimed to develop a topical formulation, increasing the solubility of Cur and promoting potential applications. In this context, Cur nanoemulsions were prepared through continuous emulsification and optimized with different ratios of components to achieve desirable properties and superior encapsulation. Accordingly, nanoemulsions prepared by the oleic acid (10%w/w) as oil phase, PEG 400 (6%w/w) as co-surfactant and mixture of Tween 80® and Span 80® (8%w/w) as surfactant showed the most favorable properties with a droplet size of 12.26 nm and polydispersity index (PDI) of 0.254. Afterward, the optimized formulation was converted to nanoemulgel using 1%w/w of Carbopol 940. The Cur formulation presented good physiochemical properties in terms of uniformity, thermodynamic stability, spreadability, and droplet size. The results showed that the release profile follows the Higuchi kinetic model. Moreover, this formulation presented excellent antioxidant capacity (FRAP value of 533.49 ± 2.84 µM Fe (II)/g) and potential photoprotective efficacy (SPF value of 13.86). It was also found to have high anti-inflammatory properties and antibacterial activity (250 µg/ml ≤ MIC < 500 µg/ml) against Staphylococcus aureus and Escherichia coli. According to the results, the current formulation of Cur is a promising candidate to improve the solubility and promote its efficacy for various topical applications.

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