Safe Mitochondrial Activation Through Photobiomodulation: Distinct Red and Near‐Infrared Responses in Normal and Malignant Cells

Photobiomodulation (PBM) with red or near-infrared (NIR) light enhances mitochondrial metabolism and tissue repair, yet its safety regarding malignant cells remains under debate. This study examined wavelength- and fluence-dependent PBM effects on skeletal muscle and cancer cells. Murine myoblasts (C2C12) and human lung adenocarcinoma cells (A549) were exposed to 660 nm LED or 830 nm NIR laser light at 0-20 J/cm². Viability (CCK-8), reactive oxygen species (ROS), and ATP levels were quantified. PBM produced a biphasic response in C2C12, with maximal viability and ATP at 5 J/cm² under NIR and moderate ROS elevation. Conversely, A549 showed stable or slightly reduced viability despite increased ROS, suggesting a distinct redox sensitivity. Both wavelengths enhanced mitochondrial activity in muscle cells while avoiding overstimulation in carcinoma cells. These wavelength- and cell type-specific effects indicate the bioenergetic safety of PBM and its potential for muscle regeneration research.