Thiopyridinium phthalocyanine for improved photodynamic efficiency against pathogenic fungi

Author(s)

Prandini, Juliana A. ; Castro, Kelly A. D. F. ; Biazzotto, Juliana C. ; Brancini, Guilherme T. P. ; Tome, Joao P. C. ; Lourenco, Leandro M. O. ; Braga, Gilberto U. L. ; da Silva, Roberto S.

• Document type: Journal article
• Source: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY; v. 231, p. 8-pg., 2022-06-01.

Abstract

The emergence of opportunistic pathogens and the selection of resistant strains have created a grim scenario for conventional antimicrobials. Consequently, there is an ongoing search for alternative techniques to control these microorganisms. One such technique is antimicrobial photodynamic therapy (aPDT), which combines photosensitizers, light, and molecular oxygen to produce reactive oxygen species and kill the target pathogen. Here, the in vitro susceptibilities of three fungal pathogens, namely Candida albicans, Aspergillus nidulans, and Colletotrichum abscissum to aPDT with zinc(II) phthalocyanine (ZnPc) derivative complexes were investigated. Three ZnPc bearing thiopyridinium substituents were synthesized and characterized by several spectroscopic techniques. The Q-band showed sensitivity to the substituent with high absorptivity coefficient in the 680-720 nm region. Derivatization and position of the rings with thiopyridinium units led to high antifungal efficiency of the cationic phthalocyanines, which could be correlated with singlet oxygen quantum yield, subcellular localization, and cellular uptake. The minimum inhibitory concentrations (MIC) of the investigated ZnPc-R complexes against the studied microorganisms were 2.5 mu M (C. albicans) and 5 mu M (A. nidulans and C. abscissum). One ZnPc derivative achieved complete photokilling of C. albicans and, furthermore, yielded low MIC values when used against the tolerant plant-pathogen C. abscissum. Our results show that chemical modification is an important step in producing better photosensitizers for aPDT against fungal pathogens. (AU)

• FAPESP's process: 16/11386-5 - Mechanistic study of perception and response to visible light in the entomopathogenic fungus Metarhizium acridum
• Grantee: Gilberto Úbida Leite Braga
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/19448-8 - Effect of photobiomodulation as synergistic addendum on photocytotoxicity of ruthenium-phthalocyanine compounds as nitric oxide and singlet oxygen producers: in vitro biochemical evaluation in two- and three-dimensional (3D) tumor cell lines
• Grantee: Roberto Santana da Silva
• Support Opportunities: Regular Research Grants