Effect of photobiomodulation using red LED (630 nm) on the metabolism of human osteoblasts

Photobiomodulation (PBM) using red LED light (630 nm) has been investigated for its ability to modulate cellular functions relevant to tissue regeneration. This in vitro study evaluated the effects of PBM on the viability, metabolism, and migration of human osteoblast-like SAOS-2 cells. Cultures were irradiated with fluences of 2, 4, or 6 J cm^-2 in three applications spaced 12 h apart and compared with a nonirradiated control. Cell viability, total protein production, alkaline phosphatase (ALP) activity, collagen synthesis, mineralized nodule formation, and wound-closure migration were assessed at 7 and 14 days. PBM did not alter viability. Total protein and collagen synthesis increased at day 14, with significantly greater collagen levels at 6 J cm^-2. ALP activity peaked at day 7 and declined thereafter; at day 7, the 2 and 6 J cm^-2 groups showed lower ALP levels than the control group, while mineralization increased over time in all groups without any between-group differences. Migration was greatest at 2 J cm^-2, and SEM images revealed higher cell density at 6 J cm^-2. These dose-dependent responses indicate distinct PBM-sensitive stages in osteoblast physiology, supporting biological rationale for parameter selection in future PBM protocols targeting bone repair and craniofacial applications.