Microneedle Patch Delivering Multifunctional Melanin-like Nanoparticles for Vitiligo Remission and Repigmentation.

Vitiligo is an autoimmune disorder characterized by the destruction of melanocytes, resulting in white skin patches that significantly affect patients' social interactions. Current clinical interventions, including immunosuppressants, phototherapy, and transplantation, aim to restore pigmentation but often fail in distal areas or long-standing cases. Bioinspired melanin-like nanoparticles (NPs), such as polydopamine (PDA) NPs, are developed as synthetic analogs of eumelanin with antioxidative and immunomodulatory properties. Here, various melanin-like NPs are compared in terms of their physical characteristics and redox activities. Based on these findings, PDA NPs modified with polyethylene glycol (PEG), termed PDA@PEG NPs, are incorporated into dissolvable microneedle (MN) patches for transdermal delivery. In a vitiligo mouse model, these patches deliver NPs into the superficial dermis, where PDA@PEG NPs serve a dual role in promoting repigmentation: (1) they offer a brown-toned concealing effect to camouflage depigmented areas and (2) they alleviate oxidative stress and reduce CD8+ T cell infiltration. Mechanistically, the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway is activated by PDA@PEG NPs. These findings support the potential of PDA@PEG/MN patches as a minimally invasive, multifunctional platform for accelerating repigmentation in vitiligo.