Transparent, 3D-printed microneedle patches that co-deliver ALA and guide blue light for preclinical photodynamic therapy of acne.

Acne is a common chronic inflammatory skin disease associated with Cutibacterium acnes (C. acnes). Although photodynamic therapy (PDT) effectively improves acne, the transdermal delivery of photosensitizers and limited light penetration through the skin restrict its therapeutic efficacy. In this study, we developed a dual-functional flexible microneedle patch using 3D printing technology, capable of simultaneously delivering the photosensitizer 5-aminolevulinic acid (ALA) and blue light. The microneedle patch exhibits favorable mechanical properties (a fracture force of 2.47 N per patch and a drug loading capacity of 655 ± 0 µg per patch) and increases the light penetration depth in tissue by 128.6%. The combination of the microneedle patch and blue light achieved an antibacterial rate of 97.10 ± 1.1% against C. acnes in vitro. In animal experiments, this strategy resulted in significantly smaller acne lesions by day 7 (size: 1.53 ± 0.30 mm; thickness score: 0.20 ± 0.45; n = 5 per group, P < 0.05), with no significant adverse effects observed during the experimental period. Our preclinical findings demonstrate that this dual-function microneedle patch provides proof-of-concept for its future development as a novel integrated platform for PDT.