Increase and homogenization of the endogenous production of protoporphyrin IX by photobiomodulation

Photodynamic therapy (PDT) and/or photodetection (PDD) based on protoporphyrin IX (PpIX) are used in many medical fields. However, the endogenous production of PpIX in tissues after administration of its precursor, 5-aminolevulinic acid (ALA) or derivatives thereof, is frequently insufficient and, in particular, inhomogeneous, leading to unsatisfactory treatment outcomes or false negatives. Photobiomodulation (PBM), which is based on the application of a sub-thermal dose of red or near infra-red light (typically in the range of 600 - 900 nm), is known to modulate, among others, the cell metabolism. Yet, the precise mechanism of PBM and, furthermore, the optimal irradiation conditions are to be determined. In the work reported here, we have studied the dependence of the endogenous PpIX production by U-87 MG glioma cells on various PBM irradiation protocols (wavelengths, irradiations, light doses). We have shown that PBM can increase, and even homogenize the endogenous production of PpIX in these cells. Therefore, combining PBM with PDT or PDD could lead to more potent and satisfying cancer treatments or detections outcomes, in particular in neurosurgery, dermatology, and urology.