Multicationic ruthenium phthalocyanines as photosensitizers for photodynamic inactivation of multiresistant microbes

Area of Science:

• Photodynamic Therapy
• Antimicrobial Research
• Materials Science

Background:

• Multiresistant microorganisms pose a significant global health threat.
• Traditional antibiotics face challenges due to increasing resistance.
• Phthalocyanine-based photosensitizers are explored for antimicrobial applications.

Purpose of the Study:

• To design and evaluate novel multicationic ruthenium(II) phthalocyanines (RuPcs) for photodynamic inactivation (PDI) of multiresistant microorganisms.
• To investigate the structure-activity relationship of RuPcs with varying cationic charges and amphiphilic properties.
• To assess the efficacy of RuPcs against Gram-positive (MRSA), Gram-negative (E. coli), and fungal (C. albicans) pathogens.

Main Methods:

• Synthesis of four RuPcs (PS1a-PS4a) with 4-12 terminal ammonium salts.
• Evaluation of PDI efficacy under low light conditions.
• Assessment of antimicrobial activity against MRSA, E. coli, and C. albicans.
• Investigation of synergistic effects with subinhibitory doxycycline doses.

Main Results:

• Hydrophilic PS1a, PS2a, and amphiphilic PS3a demonstrated superior PDI activity against MRSA compared to conventional phthalocyanines.
• PS1a, PS2a, and PS3a exhibited high activity against E. coli.
• PS4a showed limited activity alone but a significant synergistic effect with doxycycline against MRSA, enhancing log reduction.
• Weak fungicidal activity was observed against fluconazole-resistant C. albicans.

Conclusions:

• Multicationic RuPcs are effective photosensitizers for PDI of resistant bacteria.
• Amphiphilic properties and cationic charge influence RuPc localization and efficacy.
• RuPcs offer a promising alternative or adjunct therapy for combating multidrug-resistant infections.