Janus Microneedles Enabling Orderly Vitiligo Treatment Through Spatiotemporal Sequential Promotion of Melanogenesis via PAR2 Activation

The study introduces a novel Janus microneedle (Janus MN) designed for vitiligo treatment, which targets immune regulation, melanocyte regeneration, and melanosome transfer. The microneedle features a core-shell bilayer structure, with the shell containing hypericin-assembled nanoparticles and astragalus polysaccharides to improve the microenvironment by reducing oxidative stress and inhibiting immune attacks on melanocytes. The core, containing stabilized trypsin, activates the PAR2 signaling pathway to enhance melanosome transfer, promoting pigmentation. This approach achieves a multidimensional intervention by integrating dual targets within the epidermis and hair follicles, offering a precise, spatiotemporally sequential treatment strategy for vitiligo.