Janus microneedles enabling orderly vitiligo treatment through spatiotemporal sequential promoting melanogenesis to...

Vitiligo is characterized by a complex pathogenesis involving multiple factors, necessitating therapeutic strategies that simultaneously achieve immune regulation, melanocyte regeneration, and melanosome transfer modulation. Here, we designed a Janus microneedle (Janus MN) based on a core-shell bilayer structure, inspired by the melanin metabolism pathway and the stratified architecture of the skin. The shell of the MN was loaded with a complex of hypericin-assembled nanoparticles (HY-NPs) and astragalus polysaccharides, which preferentially dissolve in the epidermal hair follicle region and basal layer. This intervention ameliorated the microenvironment by scavenging reactive oxygen species and inhibiting CD8⁺ T-cell-mediated immune attacks on melanocytes for repair, while simultaneously activating the MAPK pathway to enhance melanin synthesis in melanocytes for regeneration. The MN core, encapsulated with stabilized trypsin in a hyaluronic acid matrix, targeted the upper epidermal keratinocytes. It activated the PAR2 signaling pathway to enhance melanosome transfer and phagocytosis, thereby promoting visible pigmentation. It integrated dual spatially heterogeneous targets within the epidermis and hair follicles for the first time, achieving multidimensional synergistic intervention through a sequence of "repair, regeneration, and transfer". Our study provides a novel, spatiotemporally sequential drug delivery strategy for the precise treatment of vitiligo.