Development and optimization of asiaticoside co-crystal-loaded transdermal patch for topical therapy

The objective of this study was to develop and optimize a transdermal patch incorporating asiaticoside co-crystals to enhance solubility, mechanical properties, and sustained release for effective topical therapy in wound management. Asiaticoside co-crystals were prepared by the solvent evaporation method using ethanol-water (70:30) with succinic acid (1:1 molar ratio) as co-former and incorporated into hydrogel-based transdermal patches using HPMC K100M and PEG 400. A 3² full factorial design was applied to evaluate the effect of these excipients on thickness (Y₁) and folding endurance (Y₂), with optimization conducted using Design-Expert® software. The formulations were evaluated for physicochemical properties, in vitro drug release, in vivo skin irritation, wound healing activity, and accelerated stability. DSC analysis confirmed co-crystal formation through melting point depression from 232.44 to 207.61 °C. FTIR confirmed successful co-crystal formation and compatibility with excipients. The optimized batch (F²) contained 200 mg HPMC K100M and 10 mg PEG 400, with predicted vs. experimental values for thickness (0.38 mm vs. 0.36 mm) and folding endurance (226.31 vs. 216), showing low relative errors (5.26%, 4.56%). F² exhibited 95.2 ± 2.1% drug release over 12 h, 87.56 ± 0.75% drug content, and a pH of 5.72 ± 0.03. Drug release kinetics followed the Hixson-Crowell model (R² = 0.9994) with a Fickian diffusion mechanism (n = 0.5). No erythema or edema was observed in skin irritation studies. In vivo wound contraction reached 95.0% by day 9, comparable to the standard group treated with 5% povidone-iodine ointment (96.4%). The objective of the study was to develop a sustained-release, non-irritant transdermal patch offering comparable healing with improved patient convenience. Stability studies showed minimal changes over 3 months with f² > 78.9. The optimized patch demonstrated excellent physicochemical and biological performance, offering a non-invasive, sustained-release system for wound care. Its clinical promise lies in enhanced healing efficacy, reduced application frequency, and patient compliance, warranting further in vivo pharmacokinetic and translational studies.