Efficient photodynamic therapy against Gram-positive and Gram-negative Bacteria Using rose bengal encapsulated in metallocatanionic vesicles in the presence of visible light

Significant consumption of antibiotics has generated multidrug resistance in bacteria, which is a major menace to human beings. Antibacterial photodynamic therapy (aPDT) is a progressing technique for inhibition of bacterial infection with minimal side effects. Metals and delivering agents play a major role in aPDT efficiency. Herein, we report a formulation to enrich the antibacterial photodynamic therapy utilizing metallocatanionic vesicles (MCVs) against both Gram-positive and Gram-negative bacteria. These MCVs were synthesized by utilizing iron-based double-chain metallosurfactant [FeCPC(II)] as a cationic surfactant and AOT, a double-chain anionic surfactant. These synthesized MCV fractions were characterized by distinct techniques like DLS, zeta potential, FE-SEM, confocal microscopy, SAXS, and UV-Visible spectroscopy. Polyhedral-shaped MCVs with a size of 200 nm were formed, wherein the charge and size of the catanionic vesicle can be controlled by varying the mixing ratios. Both Gram-positive bacteria, i.e., methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria, i.e., Escherichia coli (E. coli), were used for aPDT using Rose Bengal (RB) as a photosensitizer (PS) encapsulated in MCVs in the presence of a 532 nm wavelength laser. The aPDT against bacterial cells was evaluated for both dark and light toxicities. Pure MCVs also exhibited good antibacterial properties; however, much enhancement was observed in the presence of RB encapsulated in MCVs under light, where eradication of bacteria (E. coli and MRSA) was achieved in 30 min. The observations demonstrated that it is the presence of metal that enhances the singlet oxygen quantum yield of RB and MCVs help in retarding self-quenching and enhanced solubilization of RB. The cationic surfactant-rich fraction shows strong adhesion toward bacteria via electrostatic interactions. The outcome of this research shows that these newly fabricated metal-based metallocatanionic vesicles were effective against both Gram-positive and Gram-negative bacteria using aPDT and must be exploited for clinical applications as well as an alternative for antibiotics in the future.