ROS-Scavenging Hyperbranched Polymer Dot Nanozymes Combined with Fractional CO₂ Laser Microchannels for Hair Follicle...

Topical nanomaterials for hair regeneration are limited by poor follicular penetration, while the regenerative window opened by fractional laser injury is transient and accompanied by rep air-constraining oxidative stress. We investigated whether fractional CO₂ laser-generated microchannels could unlock the nanozyme activity of hyperbranched polymer dots (HPD) and accelerate hair follicle regeneration.

HPD (3-5 nm), synthesized by A₂+B₃ condensation polymerization and displaying concentration-dependent scavenging of hydroxyl radicals, hydrogen peroxide, and superoxide anions, were tested in telogen-synchronized female C57BL/6 mice. Laser energy and spot density were optimized for microchannel formation and tissue tolerability. Five groups (n = 6) received vehicle, 5% minoxidil, HPD, laser alone, or laser plus HPD; laser was applied once on Day 1 and topical treatment daily through Day 15. Outcomes were hair coverage, skin pigmentation, optical coherence tomography (OCT), hematoxylin-eosin histomorphometry, and Ki67 and β-catenin immunofluorescence at Days 8, 11, and 15.

Optimized irradiation (30 mJ, 196 spots cm^-2, 6.5% coverage) produced reproducible microchannels reaching ~191 μm into the perifollicular dermis without ulceration. Combined treatment outperformed all comparators, increasing hair coverage 16.58-fold versus control by Day 10 (p = 0.0313), follicle length 2.96-fold by Day 11 (p = 0.0001), Ki67⁺ cells 30.49-fold (p < 0.0001), and β-catenin 9.32-fold (p < 0.0001), both still elevated at Day 15. OCT showed more complete microchannel closure with HPD than laser alone. Follicle number per cross-sectional field was highest after combined treatment but did not differ significantly from control (1.91-fold, p = 0.1016).

Laser microchannels act as both delivery portals and regenerative triggers, while HPD scavenges post-injury reactive oxygen species and sustains Wnt/β-catenin activation, producing a greater-than-additive acceleration of hair follicle regeneration exceeding minoxidil. This reflects activation and accelerated growth of existing follicles rather than de novo neogenesis, and offers a drug-free platform for regenerative dermatology.