Symmetrical Diiodinated Squaraine as an Efficient Photosensitizer for PDT Applications: Evidence from Photodynamic and Toxicological Aspects

Abstract

Photodynamic therapy (PDT) is emerging as a promising non-invasive treatment for cancers. It involves three key components; a photosensitizer, light and tissue oxygen. Even though several photosensitizers have been investigated for their use in PDT, they have several disadvantages and hence the search for more effective sensitizers has become important in recent years. The dye selected in our study - symmetrical diiodinated benzothiazolium squaraine (SQDI) - is one of the newly developed photosensitizers. The study aimed to evaluate the in vitro cytotoxicity of the dye on Ehrlich's Ascites Carcinoma (EAC) cells and to assess the in vivo toxicity on Swiss Albino mice. The EAC cells were maintained in the peritoneum of mice and used to study the dark toxicity and phototoxicity by Trypan blue dye exclusion method, estimation of Reactive Oxygen Species (ROS), caspase activity and levels of thiobarbituric acid reactive substances (TBARS). The in vitro studies revealed that the dye induces toxicity in the presence of light and mediates cell death. The in vivo part of the study, which dealt with the toxicity evaluation in the body of Swiss Albino mice, was done by analyzing the parameters like serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), lactate dehydrogenase (LDH), creatine kinase (CK) and alkaline phosphatase (ALP). No significant change was observed in the above mentioned parameters in the dye administered group when compared to control. Altogether, this experiment indicates that the SQDI selected for our study may be used as an efficient photosensitizer for PDT applications and does not elicit acute toxicity to normal tissues in the absence of light.