Liposomal nanoformulations of rhodamine for targeted photodynamic inactivation of multidrug resistant gram negative bacteria in sewage treatment plant.

The antimicrobial photodynamic therapy is an alternative method for killing bacterial cells in view of the rising problem of antibiotic resistance microorganisms. The present study examined the effect of a water soluble photosensitizer, Rhodamine 6G (R6G) in stealth liposomes on multidrug resistant Pseudomonas aeruginosa in the presence of visible light. Liposomes were prepared with cholesterol and phospholipids that extracted from hen eggs in a cost effective way and characterized by light microscopy, particle size analyzer, electron microscopy, steady state spectrophotometry and spectrofluorometry. The photoefficacies of R6G in polymer encapsulated liposomes and positively charged liposomes are much higher compared to the free R6G (R6G in water) in terms of singlet oxygen quantum yield. This high potential of producing more reactive oxygen species (ROS) by liposomal nanoformulated R6G leads to efficient photodynamic inactivation of multidrug resistant gram negative bacteria in waste water. Though the singlet oxygen quantum yield of polymer coated liposomal R6G was higher than the cationic liposomal formulation, a faster decrease in bacterial survival was observed for positively charged liposomal R6G treated bacteria due to electrostatic charge interactions. Therefore, it can be concluded that the positively charged liposomal nanoformulations of laser dyes are efficient for photodynamic inactivation of multiple drug resistant gram negative microorganisms.