Author(s): Chaves, Inês ; Morais, Filipe F. M. ; Vieira, Cátia ; Bartolomeu, Maria ; Gomes, Ana T. P. C. ; Faustino, M. Amparo F. ; Neves, M. Graça P. M. S. ; Almeida, Adelaide ; Moura, Nuno M. M.
Date: 2025
Persistent ID: http://hdl.handle.net/10400.14/54543
Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Subject(s): Antimicrobial photodynamic therapy; Bacteria; Metalloporphyrin; Photosensitizers; Triphenylphosphonium; Zinc(II)
The influence of metal ions on the photochemical, photophysical, and antibacterial properties of three cationic porphyrin-triphenylphosphonium conjugates was investigated for the first time. Coordination with Zn(II), Pd(II) and Co(II) enabled fine-tuning of these conjugates properties, with Zn(II) complexes demonstrating particular promise. While Pd(II) and Co(II) complexes failed to generate singlet oxygen (1O2), thereby reducing their efficacy in bacteria photoinactivation, Zn(II) complexes exhibited efficient 1O2 generation and strong bacterial adhesion. Among these, the Zn(II) metalloporphyrin 2-Zn, featuring a well-optimized structure with three triphenylphosphonium units and six positive charges, showed exceptional effectiveness against Gram-negative Escherichia coli at lower concentrations. It significantly outperformed its free-base counterpart, reducing the required irradiation time by more than 65 %. Furthermore, 2-Zn demonstrates to be safe, exhibiting no cytotoxicity towards Vero cells. These findings highlight the potential of Zn(II) porphyrin-triphenylphosphonium complexes as efficient photosensitizers for antimicrobial photodynamic therapy (aPDT), offering a promising approach to address the growing challenge of antibiotic bacterial resistance in both clinical and environmental contexts.
