The effect of laser wavelength in photodynamic therapy and phototherapy for superficial skin diseases

Due to the low dose absorption in epidermis layer in photodynamic therapy (PDT) and non-ionizing interaction, red laser 635 nm wavelengths radiation proved to be a potential tool for propagating laser in skin. The laser enable sufficient amount of light to penetrate biological tissue and activate the dyes for treatment of superficial skin diseases. Therapy with photodynamic sensitizers and modulation of tissue activation, which cannot be controlled by the ultraviolet (UV) lasers as in phototherapy due to a high absorption of the dose in epidermis layer by chromophore. Thus, the wide application of red laser has been greatly used in PDT in skin because the red laser light transport in biological tissue is scattering dominated than the absorption with a chromophore concentration. Accurate understanding of scattering and absorption is required to determine the laser distribution for a given sample in terms of dose absorption; this is a main aim of this study to predict dose absorption in melanin and photosensitizer. Furthermore, to ensure that red laser exposure were in a proper choice for biologically relevant range and also good agreement with skin in PDT. In this issue, a standard software system is used, known as Advance System Analysis Program (ASAP) to calculate transporting laser intensity in a skin sample. Illumination by several laser wavelengths within the range of 308, 365, 405, 532 and 635 nm has been studied. We also studied the ability of long-wavelength and short-wavelength radiations to show the power uptake effect in chromophore cell in human skin. These wavelengths of UV laser are largely effective in stimulating chromophore cell in human skin. However, the visible laser wavelengths and the chromophore in epidermis are found to be less effective. We compare the dose absorption with visible and UV wavelength regions in skin layers. We show that selection of red laser wavelength in PDT lead to significance reduction in adverse effects and predict penetration of dose.