Estudo das características espectroscópicas da tetracarboxi- porfirina e seu grau de interação com bicamada lipídica

Abstract

Photodynamic therapy (PDT) has been studied as an alternative in the treatment of cancer and chronic diseases that use conventional treatments, such as therapy and radiotherapy, for example. PDT works from a photosensitizer (FS) that, after being applied to the patient, reacts only where the light is incident at an adjustable wavelength, applying a smaller number of special cells. FSs have different physicochemical characteristics and are molecules capable of interacting with light in order to generate highly reactive oxygen species (ROS) such as singlet oxygen (1O2) and other radical forms. Porphyrin compounds have been extensively used in PDT as photosensitizers (FSs) because they have favorable characteristics for this type of treatment. It is known that in addition to the photochemical properties, the photoactivity of these compounds depends on their ability to be incorporated into cells through membranes. Thus, small differences in the physicochemical properties of FS can change the sites of interaction, modifying their binding in membranes and efficiency in causing cell death. In this project, the spectroscopic properties of Tetra-(4-carboxy)phenyl porphyrin (TCPP) were studied, such as the spectroscopic characterization of FS in different solvents, where TCPP showed solubility in methanol and ethanol. Furthermore, the molar absorptivity coefficient (ε) of TCPP porphyrin was determined. The study of porphyrin aggregation in homogeneous mixtures of water and methanol was also carried out and it was estimated that the "Critical Aggregation Percentage - PAC" occurs in about 55% water. The interaction of porphyrin with membrane mimetic was evaluated, correlating its molecular characteristics with the efficiency in causing membrane damage. In addition, membrane damage was verified via carboxyfluorescein, in which TCPP presented negative percentage values. The experiment was carried out to assess whether TCPP is stable or degrades when exposed to light, and no significant decrease in absorbance was observed as a function of irradiation time, indicating that this compound is photostable under the analyzed experimental conditions.