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Updated: Jun 23, 2026
Inactivation of Pathogens via Visible-Light Photolysis of Riboflavin-5′-Phosphate
Published on: April 6, 2022
Photodynamic inactivation of Aeromonas hydrophila by cationic phthalocyanines with different hydrophobicity
Veselin Kussovski1, Vanya Mantareva, Ivan Angelov
1Department of Pathogenic Bacteria, The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria. vkussovski@yahoo.com
Abstract:
Antibacterial photodynamic therapy is a pioneering method for the inactivation of pathogenic bacteria. Four tetra alkyl-substituted cationic phthalocyanines with different hydrocarbon chains attached to the pyridyloxy group were synthesized. These photodynamic sensitizers were studied for antibacterial inactivation of a multidrug-resistant strain of Gram-negative bacterium Aeromonas hydrophila. Aeromonas species are recognized as etiological agents of a wide spectrum of diseases in humans and animals. The uptake of phthalocyanines by the bacterial cells decreased with an increase in cell density. Following the phthalocyanine solubility from hydrophilic to hydrophobic complexes, the accumulation capacity increased. Full inactivation was achieved with phthalocyanine with (methoxy) pyridyloxy substitution following a short exposure time, low drug concentration and mild irradiation. Although the phthalocyanine with the longest hydrocarbon chain (C12) has some toxic effect in the absence of light, substantial phototoxic effect was obtained with the optimal combination of drug-irradiation parameters.
Insights
This study synthesized novel cationic phthalocyanines for antibacterial photodynamic therapy. A specific phthalocyanine derivative demonstrated potent inactivation of multidrug-resistant Aeromonas hydrophila with optimized light and drug parameters.
Area of Science:
- Photochemistry
- Microbiology
- Materials Science
Background:
- Antibacterial photodynamic therapy (aPDT) offers a promising alternative for combating pathogenic bacteria.
- Multidrug-resistant Aeromonas hydrophila poses a significant threat to human and animal health.
- Phthalocyanines are effective photosensitizers for aPDT.
Discussion:
- Synthesized tetra alkyl-substituted cationic phthalocyanines with varying pyridyloxy substituents.
- Investigated the antibacterial efficacy of these sensitizers against Aeromonas hydrophila.
- Observed decreased phthalocyanine uptake with increased bacterial cell density.
- Enhanced cellular accumulation of phthalocyanines with increased hydrophobicity.
Key Insights:
- A phthalocyanine derivative with (methoxy) pyridyloxy substitution achieved complete bacterial inactivation.
- Optimal inactivation was correlated with short exposure times, low drug concentrations, and mild irradiation.
- The C12-substituted phthalocyanine exhibited some dark toxicity but significant phototoxicity under optimal conditions.
Outlook:
- Further research into structure-activity relationships of phthalocyanines for enhanced aPDT.
- Potential development of targeted aPDT strategies for multidrug-resistant infections.
- Exploration of phthalocyanine-based therapies for diverse bacterial pathogens.
