Cationic liposomes unlock the potential of ZnPc in antimicrobial photodynamic therapy

Abstract

Antimicrobial photodynamic therapy (aPDT) represents a promising alternative to conventional antibiotics for treating infections caused by resistant bacteria. In this work, Zinc(II) phthalocyanine (ZnPc) was incorporated into liposomes with varying lipid compositions to improve its photodynamic performance and overcome its poor aqueous solubility. The inclusion of cationic lipids in liposomal formulation can enhance the electrostatic interactions with bacterial cell walls. To assess the influence of surface charge on their photodynamic performance, zwitterionic and cationic liposomes were prepared using dipalmitoylphosphatidylcholine, cholesterol, and the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane. The formulations were evaluated against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The results demonstrated that liposomal encapsulation significantly improved the photodynamic activity of ZnPc compared to the free photosensitizer. Moreover, cationic liposomes demonstrated enhanced antimicrobial activity, particularly against Gram-negative strains, highlighting their potential as efficient delivery systems to improve aPDT outcomes.