Injectable Thermoresponsive Hyaluronic Acid–GelMA Composite Hydrogel Loaded with Tacrolimus and Tyrosinase-Activating Peptides for Local Immunomodulation and Melanocyte Regeneration in Vitiligo

Vitiligo is an autoimmune skin disorder characterized by localized melanocyte loss due to immune-mediated destruction, resulting in depigmented lesions. Current therapies often lack targeted delivery and regenerative capacity. In this study, we developed a multifunctional injectable hydrogel system composed of methacrylated hyaluronic acid (HAMA) and gelatin methacrylate (GelMA), designed for localized immunomodulation and melanocyte regeneration. The composite hydrogel was synthesized via photoinitiated free-radical polymerization using lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as a cytocompatible photoinitiator under visible light (405 nm). This method enabled tunable crosslinking density, which was optimized for mechanical stiffness mimicking native dermis (~1–3 kPa). The hydrogel formulation incorporated tacrolimus encapsulated within biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles for sustained, pH-responsive release and synthetic tyrosinase-activating peptides to promote melanogenic signaling. Rheological analysis confirmed shear-thinning behavior and sol–gel transition at physiological temperature (37 °C). The hydrogel demonstrated excellent biocompatibility and functional efficacy in vitro, as shown by the 3D co-culture of primary human keratinocytes and melanocytes embedded within the hydrogel matrix, which exhibited enhanced melanogenesis through melanin quantification assays and upregulation of MITF and TYR gene expression. Immunomodulatory effects were validated by co-culture with activated CD8+ T-cells, which showed reduced cytotoxicity and altered cytokine release profiles. Hydrogel degradation kinetics and tacrolimus release profiles were characterized under simulated dermal pH (5.5) and physiological pH (7.4), confirming controlled biodegradability and sustained drug release. Overall, the injectable HAMA–GelMAhydrogel platform provided a dual-function localized immunosuppressive and regenerative microenvironment, offering a promising strategy for vitiligo treatment. These findings support further in vivo evaluation and potential clinical translation.