Photosensitizer’s Dynamics Studies in Different Biological Samples using Laser Irradiation

Abstract

Photodynamic therapy (PDT) is an emerging treatment modality that employs the photochemical interaction of three components. These are light of suitable wavelength, photosensitizer, and singlet oxygen. The main objective of this work is the determination of pharmacokinetics of different photosensitizers after laser irradiation in different biological samples like cell lines and tissues to improve the efficacy of PDT. Present study investigates the dynamic behaviour of different photosensitizers under laser irradiation e.g. (a) biodistribution of Photofrin® (b) laser induced effects (c) depth of necrosis under exposure of different wavelengths of light sources (d) synergistic effect of toxicity of ZnO nanostructures bare and conjugated with photosensitizers like Aminolevulinic acid (5-ALA), Photofrin® and protoporphyrin dimethyl ester (PPDME) determined for the treatment of localized cancer cells. Firstly, biodistribution of Photofrin® into Sprague Dawley rat has been investigated by methodology for radiolabelleing of Photofrin® with labelling efficiency of Photofrin® with 99m Tc. In addition, it was explored that 99m Tc is more than 95%. The current technique is simpler and efficient as compared to the earlier published protocol. In the second part of this experimental study, different photosensitizer‟s uptake was explored in the in vitro model e.g. different cell lines (HepG2, RD, Hep2C, AG1518 and FM55P). Study of optimal dose of laser, cellular totoxicity and phototoxicity were also the part of our experiment. The third aspect of study relates to in vivo study, normal rat liver were treated as biological sample, PDT under illumination of different wavelengths of light (630 nm, 660 nm, 600 nm and its alternate combinations) has been performed and proved that effectiveness of 630 nm of wavelength is more efficient for depth of necrosis as compare to other wavelengths of light source. Finally, the synergistic effect of toxicity of zinc oxide nanorods (ZnO NRs) conjugated with 5-ALA, Photofrin® and PPDME was determined for the treatment of localized cancer cells. Cell toxicity due to microinjection and free standing drug delivery was observed by detection of reactive oxygen species (ROS) liberation, and verified by MTT assay. It is successfully demonstrated that UV-A irradiation increased toxicity and caused significant production of ROS which leads to cell necrosis within few minutes. Zinc oxide nanorods are toxic for both normal as well as malignant cells under exposure of ultraviolet (UV) containing 240 nm of wavelength.