Spectroscopic features of PHOTOGEM® in human Rhabdomyosarcoma (RD) cellular model

Abstract

Our study demonstrated the biological changes produced in the Rhabdomyosarcoma (RD) cell line triggered by the photochemical reaction between PHOTOGEM® (photosensitizing agent) and He-Ne laser light (wavelength = 632.8 nm of red light). The basic parameters of photodynamic therapy were optimized to study photosensitizer localization/uptake, PHOTOGEM® absorption spectra, cytotoxic effects, phototoxic effects, and morphological changes in the RD cell line. The experiment included three steps. First, spectrometric measurements were obtained to optimize the absorbance and optimal density of PHOTOGEM® in the experimental biological model (RD cell line). A neutral red assay was used to estimate the loss of cellular viability. Second, the RD cell line containing PHOTOGEM® was irradiated with laser light (dose up to 100 J/cm2). In addition, a non-fluorescent compound was used to determine the intracellular production of reactive oxygen species. The treated cells were examined and photographed. The optical density of the PHOTOGEM®-exposed RD cell line was insignificant after 0–2 h but increased significantly after 20 and 24 h. A photosensitizer concentration of 120 μg/ml and a red He-Ne laser dose of 100 J/cm2 having wavelength 632.8 nm produced the maximum phototoxic effect in the RD cell line. The cell viability of the PHOTOGEM®-labeled RD cells decreased to 65% in the absence of the laser dose, but there was significant cell viability loss under suitable laser exposure (100 J/cm2).