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Abstract:
This study investigates the potential of high-intensity narrow-spectrum (HINS) 405-nm light as a wound decontamination method that avoids harming healing processes. Using fibroblast-populated collagen lattices (FPCLs) as an in vitro wound healing model, the effects of HINS light on fibroblast function (contraction, proliferation, α-smooth muscle actin expression) and morphology were assessed. Bactericidal efficacy was tested against Staphylococcus epidermidis. Results indicate that lower doses of HINS light (up to 5 mW/cm² for 1 hour, delivering 18 J/cm²) did not significantly inhibit fibroblast activity or viability. In contrast, a higher dose (15 mW/cm² for 1 hour, 54 J/cm²) caused significant damage and functional inhibition. Importantly, the maximum non-inhibitory dose for fibroblasts (5 mW/cm² for 1 hour) achieved almost complete inactivation (3-log reduction) of S. epidermidis. The findings suggest HINS 405-nm light shows promise for disinfecting wounds without adversely affecting cellular healing mechanisms, meriting further research.
Summary of HINS Light Effects on Wound Healing Model and Bacteria:
Context: Healthcare-associated infections (HAI) and antibiotic resistance necessitate novel wound decontamination methods that do not impede healing. High-intensity narrow-spectrum (HINS) 405nm light is explored for this purpose.
Mechanism: HINS 405nm light inactivates bacteria by exciting endogenous porphyrins, leading to reactive oxygen species generation, without requiring external photosensitizers.
Methodology: The study used 3T3 mouse fibroblast-populated collagen lattices (FPCLs) as an in vitro wound healing model. FPCLs were exposed to HINS 405nm light at various intensities (0.5, 1.8, 3.6-15 mW/cm²) for 1 hour.
Fibroblast Assessment: Effects on FPCL contraction, cell number/viability (MTT assay, staining), cell morphology, and α-smooth muscle actin (α-SMA) expression were measured.
Bacterial Assessment: The bactericidal effect of the maximum non-damaging fibroblast dose was tested against Staphylococcus epidermidis (NCTC 10956) suspended in PBS.
Low-Dose Fibroblast Effects: Exposures up to 5 mW/cm² (18 J/cm²) for 1 hour showed no significant inhibitory effects on FPCL contraction, cell number, α-SMA expression, or cell morphology compared to controls.
High-Dose Fibroblast Effects: Exposure at 15 mW/cm² (54 J/cm²) for 1 hour halted FPCL contraction, caused an ~80% reduction in cell number within 24h, inhibited α-SMA expression, and altered cell morphology.
Maximum Safe Dose Identified: 5 mW/cm² for 1 hour was determined as the maximum intensity tested that did not significantly inhibit fibroblast function in the FPCL model.
Bactericidal Efficacy: Exposure to 5 mW/cm² HINS light for 1 hour resulted in almost complete inactivation (a 3-log10 reduction) of a 10³ CFU/ml S. epidermidis population.
Clinical Relevance:S. epidermidis is a common wound pathogen. The bacterial reduction achieved by the fibroblast-safe dose suggests potential for maintaining wound sterility against typical environmental contamination levels.
Future Work: Further studies are needed to test effects on primary human cells (fibroblasts, keratinocytes), other bacterial species, and in environments mimicking wound beds (e.g., presence of plasma).
Conclusion: HINS 405nm light at 5 mW/cm² for 1 hour demonstrates potential as a wound disinfection tool, effectively reducing bacterial load (S. epidermidis) without impairing fibroblast function in this in vitro model.