Blue LED light dose-dependently reduces chronic wound bacterial burden, but not healing.

Chronic wounds represent a major healthcare challenge, often complicated by persistent bacterial infections and biofilm formation, which significantly impede healing. Standard antimicrobial treatments face increasing issues with antibiotic resistance, necessitating alternative strategies. Phototherapy, particularly blue LED light, has emerged as a promising non-pharmacological approach due to its known antimicrobial properties and potential to modulate cellular processes without inducing resistance. This study investigated whether varying doses of blue LED light could effectively reduce bacterial load in chronic wounds and consequently impact the healing process, addressing a critical gap in non-antibiotic infection management.

This clinical study enrolled 22 patients with chronic wounds, sequentially assigning them to receive one of three escalating doses of blue LED light (λ=405 nm): 20 J/cm² (n=7), 60 J/cm² (n=8), or 100 J/cm² (n=7). After baseline measurements of bacterial counts, cytokine levels, and wound size, patients received six irradiations over 2 weeks at 2-3-day intervals. Bacterial counts were semi-quantified using surface swab samples just before and immediately after each irradiation. Primary endpoints included changes in bacterial burden, wound size, and levels of inflammatory cytokines (e.g., IL-1α, TNF-α).

Blue LED light treatment significantly reduced bacterial counts in a dose-dependent manner (p < 0.0001). The mean log10 reduction of colony-forming units/swab across six treatments was significantly greater for higher fluences: 1.55 ± 0.33 for 60 J/cm² and 1.82 ± 0.22 for 100 J/cm², compared to 0.65 ± 0.095 for 20 J/cm². > The reductions achieved with 60 J/cm² and 100 J/cm² fluences did not significantly differ (p = 0.180), suggesting a plateau in efficacy beyond 60 J/cm². However, these bacterial reductions were transient; bacterial counts at follow-up, 4 days after the last irradiation, showed no significant difference among groups (p = 0.668). Furthermore, levels of selected cytokines (e.g., IL-1β, IL-6, VEGF) did not change significantly from baseline, and linear wound healing rates also showed no significant differences between the three groups (p = 0.815).