Comparative analysis of pulsed-wave and continuous-wave 808nm laser photobiomodulation on HUVEC viability and migration

Low-level laser therapy (LLLT) is a non-invasive technique that uses low-power lasers (600-1100 nm) to regulate cellular functions, offering promising applications in tissue repair, inflammation reduction, and vascular regeneration. The laser operation mode is a key parameter affecting the therapeutic efficacy of LLLT by modulating cellular responses. Continuous-wave (CW) mode provides continuous output that may cause heat accumulation, while pulsed-wave (PW) mode reduces thermal effects by emitting light intermittently. To evaluate these effects, we employed an 808 nm laser to compare CW and PW modes at different energy densities (3.12, 6.24, 9.36, and 12.48 J/cm²) on the viability of human umbilical vein endothelial cells (HUVECs). The results showed that at the same power density (312 mW/cm²), PW mode significantly increased cell viability at 3.12, 6.24, and 9.36 J/cm² (^∗p<0.05, ^∗∗p<0.01, ^∗∗∗p<0.001), but viability declined at 12.48 J/cm², indicating possible energy saturation. In contrast, CW mode showed no cytotoxicity from 3.12 to 9.36 J/cm² and slightly promoted viability at 6.24 J/cm². However, at 12.48 J/cm², cell viability dropped significantly, suggesting phototoxicity at high energy. Furthermore, scratch assay results demonstrated that PW irradiation at 9.36 J/cm² promoted HUVEC migration compared to the control, indicating that pulsed-mode LLLT facilitates wound closure and vascular remodeling. Overall, our study provides guidance for optimizing LLLT parameters and demonstrates the potential benefits of PW mode in endothelial cell therapies. Future studies should further explore the optimization of pulsed laser parameters, including frequency and duty cycle, to improve therapeutic outcomes.