Photochemical and Sono-Photochemical Studies of Zn (II) Porphyrin-conjugated Chitosan Hydrogels for Enhanced Singlet Oxygen Generation

This study explores the synthesis, characterization, photochemical, and sono-photochemical properties of covalently conjugated porphyrin-chitosan hydrogels for potential application in photodynamic therapy (PDT) and sono-photodynamic therapy (SPDT). The efficient production of singlet oxygen, a crucial reactive oxygen species (ROS) in these therapies, was investigated. Zinc(II) porphyrins 1 and 2 were synthesized by metal insertion to free based porphyrins and covalently linked to chitosan via Schiff-base reaction to produce chitosan hydrogel CS-1 and CS-2 (conjugation via phenylacetylene spacer). The synthesized compounds were characterized using standard spectroscopic techniques, confirming successful conjugation. Scanning electron microscopy (SEM) analysis demonstrating the homogeneous distribution of porphyrins within the hydrogel matrix. Photophysical and photochemical properties, including ground state absorption and singlet oxygen generation, were evaluated for both porphyrin complexes and chitosan-conjugated hydrogels in DMSO. The porphyrin-hydrogel structures showed superior singlet oxygen generation efficiency. Sono-photochemical studies showed further enhanced singlet oxygen generation, with the highest quantum yield (ΦΔ= 0.81) observed for the chitosan hydrogel CS-2. The results demonstrated enhanced singlet oxygen generation in the hydrogel structures, particularly under simultaneous ultrasound and light irradiation, indicating their potential efficacy in PDT and SPDT applications. Additionally, photo degradation studies revealed the stability of the synthesized compounds under light irradiation. These findings highlight the potential of porphyrin-conjugated chitosan hydrogels as effective photosensitizers for PDT and SPDT applications.