Microcápsulas inteligentes de híbridos de derivados de Porfirina Ouro para libertação acionada pela luz

Raquel Brito Cabaça

Key information

Authors:

Raquel Brito Cabaça (Raquel Brito Cabaça)

Supervisors:

Pedro Miguel Neves Ribeiro Paulo (Pedro Miguel Neves Ribeiro Paulo); Vanda Isabel Roldão Canelas Vaz Serra (Vanda Isabel Roldão Canelas Vaz Serra)

Published in

December 3, 2024

Abstract

The aim of this dissertation is the development of photoactive polyelectrolyte microcapsule systems with enhanced optical and photodynamic properties, to enable their application in the theranostics of tumor tissues. Hybrid systems functionalized with both a photosensitizer and gold nanorods were constructed, promoting the enhancement of the photosensitizer fluorescence through plasmonic effects. Two distinct photosensitizers were used: the tetra-cationic porphyrin 5,10,15,20-tetrakis (4-N-methypyridinium), TMPyP, and the tetrasulfonated aluminum phthalocyanine, AlPcS4. To study the influence of the relative position of the fluorophore and the gold nanorods on fluorescence enhancement and singlet oxygen production, systems with different architectures were developed. In the porphyrin-functionalized system, the porphyrin was incorporated into the core, while in the phthalocyanine-functionalized system, the phthalocyanine was adsorbed onto the outermost layer of the microcapsules. The successive layer-by-layer adsorption of oppositely charged polyelectrolytes was monitored by measuring the zeta potential. The optical and electronic properties of the hybrid systems were analyzed through UV-Vis absorption spectroscopy and steady-state fluorescence, and the results were compared with control systems containing only one of the functionalities. Fluorescence lifetime imaging microscopy (FLIM) analysis revealed a 400-fold enhancement factor for TMPyP-functionalized hybrid, while no fluorescence enhancement was observed for the AlPcS4-functionalized hybrid. Singlet oxygen production by each photosensitizer was indirectly studied through the degradation of 9,10-Anthracenediyl-bis(methylene)dimalonic acid (ABDA), monitored by UV-Vis spectroscopy. It was concluded that the encapsulation of the photosensitizer in the microcapsule limits the oxidation reaction of ABDA, negatively affecting the quantification of the generated singlet oxygen.