Abstract
Photodynamic therapy (PDT) is a selective and minimally invasive therapeutic approach, involving the combination of a light-sensitive compound, called a photosensitizer (PS), visible light and molecular oxygen. The interaction of these per se harmless agents results in the production of reactive species. This triggers a series of cellular events that culminate in the selective destruction of cancer cells, inside which the photosensitizer preferentially accumulates. The search for ideal PDT photosensitizers has been a very active field of research, with a special focus on porphyrins and porphyrin-related macrocycle molecules. The present study describes the photophysical characterization and in vitro phototoxicity evaluation of 5,10,15,20-tetra(quinolin-2-yl)porphyrin (2-TQP) as a potential PDT photosensitizer. Molar absorption coefficients were determined from the corresponding absorption spectrum, the fluorescence quantum yield was calculated using 5,10,15,20-tetraphenylporphyrin (TPP) as a standard and the quantum yield of singlet oxygen generation was determined by direct phosphorescence measurements. Toxicity evaluations (in the presence and absence of irradiation) were performed against HT29 colorectal adenocarcinoma cancer cells. The results from this preliminary study show that the hydrophobic 2-TQP fulfills several critical requirements for a good PDT photosensitizer, namely a high quantum yield of singlet oxygen generation (Φ∆ 0.62), absence of dark toxicity and significant in vitro phototoxicity for concentrations in the micromolar range.
Highlights
Cancer is one of the leading causes of death worldwide [1]
Our results show that 2-TQP exhibits a high quantum yield of singlet oxygen generation and, at the concentrations tested, a significant in vitro phototoxicity for concentrations of minimal dark cytotoxicity, fulfilling two critical requirements for a good Photodynamic therapy (PDT) photosensitizer
Gibco® fetal calf from Thermo Fisher Scientific Inc. (Waltham, MA, USA). 2-TQP (Figure 1a) was synthesized by serum was obtained from Thermo Fisher Scientific Inc. (Waltham, MA, USA). 2-TQP (Figure 1a) was condensation of 2-quinolinecarboxaldehyde with pyrrole in acid media, according to a procedure synthesized by condensation of 2-quinolinecarboxaldehyde with pyrrole in acid media, according to already described by usdescribed
Summary
Cancer is one of the leading causes of death worldwide [1]. This disease, characterized by uncontrolled growth and spread of abnormal cells, may be triggered by external or internal factors, such as chemicals, sunlight, hormones, immune conditions and hereditary mutations [2]. Awareness that the efficiency of this therapeutic approach is critically dependent on the properties of the photosensitizer used prompted, in the last decades, an active search for an ideal photosensitizer, with porphyrins and porphyrin-related macrocycles at the forefront of the photosensitizers developed and clinically used [7,13,14] This preference can be explained in terms of the selectivity of these compounds towards tumor tissue and of their easy synthesis, versatility, chemical purity and unique photophysical properties (e.g., aromatic stability, high absorption in the red region of the visible spectrum, where light is most penetrating and less harmful to the tissues, and high quantum yields of singlet oxygen generation).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
