Enhancing Skin Repair and Photodamage Reversal With 755‐nm Picosecond Laser and Bioactive Polymer Dots in a Nude Mouse Model

ABSTRACT Picosecond laser technology has emerged as a promising intervention for reversing photodamage by promoting epidermal repair and collagen regeneration. Polymer dots (PDs) have shown antioxidant and wound‐healing properties. This study evaluates the efficacy of a combined 755‐nm picosecond laser and bioactive PDs treatment to enhance skin repair and reverse photodamage in a nude mouse model subjected to UVB irradiation. Using twelve 6‐week‐old BALB/c nude mice, the experiment was conducted over 10 weeks, with the mice assigned to one of four groups: UVB alone, UVB + PEG1000, UVB + PD + PEG1000 and UVB + Laser +PD + PEG1000. Assessment methods included immunohistochemistry, enzyme‐linked immunosorbent assay and Masson's trichrome staining to evaluate collagen content, epidermal thickness and protein expression associated with skin repair. The UVB + Laser + PD + PEG1000 group achieved a significant reduction in epidermal thickness by Day 22 ( p = 0.0017) and showed superior collagen retention compared to the UVB group ( p < 0.0001). In addition, MMP‐9 levels in the UVB + PD + PEG1000 group reduced by 4.2% on Day 11 versus 9.3% in the UVB‐only group on Day 1 ( p = 0.03), while IL‐6 levels markedly decreased in all treated groups compared to the UVB group, indicating diminished inflammation ( p < 0.001). Analysis of Smad2/3 signalling on Day 11 in the UVB + PD + PEG1000 group revealed enhanced activation of skin repair pathways, with values reaching 2.8% compared to 1.3% in the UVB group on Day 1 ( p = 0.0026). These findings suggest that combining the 755‐nm picosecond laser with bioactive PDs offers a novel therapeutic approach for photodamage repair, enhancing collagen synthesis and inflammation reduction and supporting further investigation into its potential in skin ageing and damage reversal.