Bioorthogonal Click-Engineered Microneedle Patch Enables Adeno-Associated Virus-Mediated Dermal Acidic Fibroblast Growth Factor Expression for Hair Loss Treatment

Hair loss is a prevalent dermatological disorder with limited durable therapies. Although acidic fibroblast growth factor (aFGF) promotes hair regeneration, its poor bioavailability and rapid degradation constrain efficacy. Here, we report a bioorthogonal click-engineered microneedle patch (ClickMNP) that enables efficient intradermal delivery of adeno-associated virus encoding aFGF (AAV-aFGF) for localized, sustained transgene expression. ClickMNP is constructed by synthesizing dibenzocyclooctyne-modified hyaluronic acid (HA-DBCO) that undergoes strain-promoted azide-alkyne cycloaddition (SPAAC) with an azide-functionalized poly(lactide-<i>co</i>-glycolide) (PLGA-N₃) microneedle matrix, forming a cross-linked hydrogel network on the microneedle surface that immobilizes AAV while retaining infectivity, thereby creating a chemically robust, biologically active microneedle-virus interface for dermal gene transfer. Following intradermal application, ClickMNP breaches the stratum corneum and establishes a sustained viral depot that drives prolonged aFGF expression, addressing the low exposure and rapid clearance inherent to protein administration. In murine alopecia models, a single ClickMNP administration accelerates hair-follicle regeneration, enhances dermal angiogenesis, and prolongs anagen, outperforming free AAV-aFGF and recombinant aFGF controls. The platform preserves follicle viability and sustains regrowth across repeated depilation cycles, yielding native-like follicular architecture with increased indices of de novo folliculogenesis. Biocompatibility assessment indicates favorable local tolerability, and transcriptomic analysis reveals upregulation of pathways associated with fibroblast proliferation, angiogenesis, and follicular cycling, consistent with the observed phenotype. Collectively, ClickMNP establishes a versatile bioorthogonal microneedle-virus interface strategy that combines chemical engineering with gene therapy, offering a transformative solution for hair loss and broader cutaneous indications.