Double-layered PLGA/HA microneedle systems as a long-acting formulation of polyphenols for effective and long-term management of atopic dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory disorder that requires long-term treatment to achieve optimal control. Topical corticosteroids or calcineurin inhibitors are the mainstay of treatment, but the safety and efficacy of their daily use remain a concern. Here, we report a double-layered poly(lactic-co-glycolic acid) (PLGA)/sodium hyaluronate (HA) microneedle (MN) patch as a long-acting formulation for sustained delivery of natural polyphenols, curcumin (CUR) and gallic acid (GA), into the inflamed skin. Upon insertion into the skin, the HA layer is rapidly dissolved within 5 min for triggering GA release; the PLGA tip is embedded into the dermis for sustained release of CUR for 2 months. Initially, CUR and GA are simultaneously released from the MNs to exert synergistic antioxidant and anti-inflammatory effects, thus promptly relieving AD symptoms. After the complete release of GA, the extended CUR release can maintain the improvement obtained for at least 56 days. Our results revealed that compared with the CUR-only MN and untreated AD groups, the administration of CUR/GA-loaded MNs not only rapidly reduced the dermatitis score from Day 2 but also significantly inhibited epidermal hyperplasia and mast cell accumulation, reduced serum IgE and histamine levels, and downregulated reactive oxygen species production in the skin lesions of Nc/Nga mice on Day 56. These findings demonstrated that the double-layered PLGA/HA MN patch can serve as an effective dual-polyphenol delivery system for rapid and long-term management of AD.