Development and Characterization of Shikonin-Loaded NLC with Enhanced Photostability in Hydrogel-Based Dermal Patch

Background/Objectives: Shikonin is a bioactive compound with promising pharmaceutical potential, particularly for anti-inflammation and ability to inhibit proliferative scar formation. However, its applications are limited by poor photostability. Therefore, this research aimed to develop and optimize shikonin-loaded NLC to improve the photostability of shikonin. The optimized NLC formulation was subsequently incorporated into a hydrogel matrix to fabricate a dermal patch, providing a potential alternative for topical scar treatment and self-care application. Methods: Shikonin-loaded NLCs were developed, optimized, and evaluated for physicochemical properties, entrapment efficiency, photostability, and in vitro release. The optimized NLC was incorporated into a hyaluronic acid-carboxymethyl cellulose hydrogel matrix to fabricate and evaluate an NLC-based dermal patch. Results: The optimized shikonin-loaded NLC exhibited a particle size of 104.94 nm with a narrow polydispersity index of 0.15, and a zeta potential of -34.34 ± 0.02 mV. The NLC achieved high entrapment efficiency (>90%). The NLC significantly enhanced the photostability of shikonin, by increasing the percentage of shikonin remaining after light exposure from 37.36 to 64.55% (p < 0.05). In addition, the cumulative shikonin release over 12 h was 15.61 ± 4.18%, following Korsmeyer-Peppas model. A combination of hyaluronic acid and carboxymethyl cellulose (1% w/w) was employed as the biopolymer for the hydrogel dermal patch. The shikonin-loaded NLC-based dermal patch exhibited favorable physicochemical characteristics. Conclusions: The NLC demonstrated enhanced photostability and release properties, which are preserved upon their integration into the hydrogel. The incorporation of shikonin-loaded NLC into a hydrogel matrix provides a viable strategy for stabilizing this light-sensitive bioactive compound. Consequently, this NLC-loaded hydrogel system represents a promising platform for future topical dermal delivery in pharmaceutical and cosmetic applications.