Enhanced antimicrobial photodynamic activity of photosensitizer encapsulated copper based metallocatanionic vesicles against E.coli using visible light

Abstract

In this research, we demonstrated preparation of metallo-catanionic vesicles by proper mixing of desired stoichiometric molar ratios of a cationic metallosurfactant, hexadecyltrimethyl ammonium copper trichloride and anionic conventional surfactant, sodium dodecyl sulphate. The characterization of synthesized metallo-catanionic vesicles was done by using various analytical tools. Further, these synthesized metallo-catanionic vesicles were used for encapsulation of a cationic dye (Toluidine blue (TB)), as well as an anionic dye (Rose Bengal (RB)). The dye encapsulated metallo-catanionic vesicles were tested for singlet oxygen generation and were employed for antimicrobial Photodynamic Therapy (aPDT) against Escherichia coli (E.coli). Also, a comparison is made between TB and RB encapsulated metallo-catanionic vesicles. These vesicles exhibited enhanced singlet oxygen quantum yield thereby showing photodynamic activity against Escherichia coli that was investigated using colony forming unit count method. The bacterial growth was tremendously decreased from 5.84× 106 CFU/mL to 0.06 × 106 CFU/ mL using TB encapsulated metallo-catanionic vesicles SDS:CuC I (30:70) under irradiation and to 0.34 × 106 CFU/mL using TB encapsulated 70:30 fraction. With variable charge and the presence of metal, the metallo-catanionic vesicles work effectively for PDT against E.coli. Interestingly, the RB encapsulated metallocatanionic vesicles exhibited much enhanced effect, as the bacterial growth was diminshed and almost zero colony formation was observed. Herein developed metallo-catanionic vesicles of variable charge perform efficiently and effectively in PDT against E. coli and can be scalable for affordable industrial applications.