Shikonin-Loaded ROS-Responsive Microneedles for Psoriasis Therapy: Formulation, Transdermal Delivery, and Mechanistic Evaluation

Background/Objectives: Shikonin (SKN) is a potential anti-psoriatic agent, yet its clinical application is hindered by poor water solubility and low stratum corneum permeability. This study aimed to develop a reactive oxygen species (ROS)-responsive hydrogel microneedle system encapsulating SKN-loaded polymeric micelles (SKN-M@MN) to enhance transdermal delivery and evaluate its therapeutic effects in psoriasis. Methods: Shikonin-loaded micelles (SKN-M) were optimised using a thin-film hydration method. SKN-M@MN was fabricated via a two-step casting method using phenylboronic acid-modified hyaluronic acid (HA-PBA) and polyvinylpyrrolidone K90 as the tip matrix. Skin penetration, ROS-responsive release, and anti-psoriatic efficacy were assessed in an imiquimod (IMQ)-induced mouse model. Mechanistic studies included RNA-seq, qPCR, and Western blotting. Results: SKN-M achieved an encapsulation efficiency of 93.45 ± 0.24%, a particle size of 62.49 ± 0.92 nm, and a zeta potential of −36.78 ± 1.12 mV. SKN-M@MN showed 100% skin penetration, sustained drug release, and accelerated degradation under high ROS conditions. In psoriatic mice, SKN-M@MN significantly alleviated skin lesions, reduced epidermal hyperplasia (Ki67), and downregulated IL-17A and TNF-α levels both locally and systemically. Mechanistically, it inhibited the PI3K/AKT and NF-κB signalling pathways. Conclusions: The SKN-M@MN microneedle platform integrates physical skin penetration, ROS-responsive drug release, and pathway inhibition, offering an effective strategy for transdermal delivery of poorly soluble drugs in psoriasis therapy.