QbD-engineered EGCG-rosmarinic acid cubosomal hydrogel for controlled skin delivery and antimelanoma efficacy

This study reports the development of a nanostructured topical delivery system comprising cubosomes co-encapsulating epigallocatechin-3-gallate (EGCG) and rosmarinic acid (RA) for melanoma therapy using a quality-by-design (QbD) framework. Risk assessment, Taguchi screening, and Box-Behnken design (BBD) optimization were employed to establish a robust design space and optimize formulation variables. The optimized cubosomes exhibited a particle size of 134.9 nm, polydispersity index of 0.23, and zeta potential of -17.9 mV, indicating good colloidal stability, with high encapsulation efficiencies for EGCG (89.2%) and RA (86.2%). The cubosomes were incorporated into a xanthan gum hydrogel, forming a pseudoplastic system suitable for dermal application. The formulation demonstrated significantly enhanced ex vivo skin permeation (EGCG: 90.5 ± 0.24%; RA: 93.4 ± 0.41%) and improved in vitro drug diffusion (82.3 ± 3.4% and 86.0 ± 1.35% for EGCG and RA, respectively). Drug release followed a non-Fickian mechanism. Enhanced cellular uptake and mitochondrial localization were observed. The formulation exhibited potent cytotoxicity against melanoma cells, with IC₅₀ values of 11.3 ± 1.56 µg/mL (Human malignant melanoma cells, A375) and 32.6 ± 1.45 µg/mL (Murine melanoma cells, B16F10), while showing minimal toxicity toward normal human epidermal melanocytes (NHEM) cells. In vivo studies demonstrated significant tumor growth inhibition with good dermal tolerability and no systemic toxicity. Collectively, the EGCG-RA cubosomal hydrogel offers a promising platform for controlled dermal delivery and effective melanoma therapy.