Cellular bioenergetic and migratory responses of human gingival fibroblasts to 940 nm diode laser photobiomodulation
摘要
Wound healing in the oral cavity is challenged by continuous microbial exposure, mechanical loading, and fluctuating pH, making rapid and predictable soft tissue repair clinically relevant. Photobiomodulation (PBM) refers to the application of low-dose, non-ionizing light to modulate cellular behavior and support tissue repair. PBM effects have been documented not only in the red (600–700 nm) and near-infrared (780–1100 nm) ranges, but also, in more recent studies, using blue (~ 450 nm) and green (~ 532 nm) light, where measurable intracellular and extracellular matrix changes have been observed. This in vitro study examined how different energy densities of 940 nm diode laser PBM influence human gingival fibroblast (HGF) metabolism and migration, two key components of early wound repair. Commercially available human gingival fibroblasts were cultured as monolayers and irradiated with a 940 nm continuous-wave diode laser (Epic X, Biolase) at energy densities of 6.49, 8.84, and 14.92 J/cm²; non-irradiated cells served as controls. Metabolic activity (MTT assay), membrane integrity (LDH release), nitric oxide (NO) production (Griess assay), and intracellular ATP levels (CellTiter-Glo) were assessed up to 24 h after PBM. Cell migration and wound closure dynamics were quantified in a scratch model using digital holographic live-cell imaging. At 24 h, MTT analysis showed a modest increase in metabolic activity in PBM-treated cells, with the highest energy density (14.92 J/cm²) reaching approximately 19% above control. LDH release and NO levels remained similar to controls across all groups, indicating no detectable cytotoxicity or NO-mediated inflammatory response under the tested conditions. ATP quantification revealed time- and dose-dependent changes, with the largest increase (around 25% above control at 24 h) at 8.84 J/cm². Digital holography demonstrated that 6.49 J/cm² slightly increased migration speed and produced the fastest gap closure, whereas 14.92 J/cm² reduced migration velocity and delayed closure, consistent with a biphasic dose response. In this HGF monolayer wound model, short-exposure 940 nm PBM within a restricted fluence window (6.49–8.84 J/cm²) enhanced cellular energy metabolism without detectable cytotoxicity and selectively modulated fibroblast migration. Because these findings derive from a single-cell-line in vitro model, they should be viewed as experimentally defined irradiation parameters that can inform, but not replace, future in vivo and clinical studies on PBM-assisted oral soft tissue repair.