Novel Deep Eutectic Solvent–Hydrogel Systems for Synergistic Transdermal Delivery of Chinese Herb Medicine and Local Treatments for Rheumatoid Arthritis

In this study, a novel hydrogel system incorporating an amino acid-based deep eutectic solvent (DES) was prepared, and the skin-permeation enhancement of traditional Chinese herb medicine was evaluated using "sanwujiaowan" extract as the model formula. Briefly, a DES-extract complex was constructed by co-heating the herb formula extracts with the amino acid as the hydrogen receptor and citric acid as the hydrogen donor. The DES-extract complex demonstrated excellent dissolution and skin permeability of the complicated ingredients in the extracts. Consequently, the DES-extract complex was introduced to a hydrogel system, which showed better mechanical properties and viscoelasticity performance. Using a collagen-induced arthritis rat model, the DES-hydrogels exerted an enhanced therapeutic effect that significantly reduced the inflammatory response with systemic toxicity of the extracts. Therefore, our work suggests a novel strategy for synergistic transdermal delivery of Chinese herb medicine and local treatments for rheumatoid arthritis.