Antimicrobial photodynamic activity of rose bengal conjugated multi walled carbon nanotubes against planktonic cells and biofilm of Escherichia coli

Background: The global threat of antimicrobial resistance especially due to the bacterial biofilms has engaged researchers in the search of new treatment modalities. Antimicrobial photodynamic inactivation (aPDI) is one of the alternative treatment modalities which kills bacteria by generating endogenous reactive oxygen species (ROS). In this work authors evaluated the antibacterial and antibiofilm efficacy of rose Bengal (RB) conjugated to CNT against E. coli. Methods: The interaction of anionic dye to the CNT was studied using UV vis spectroscopy, HRTEM, FTIR and spectrofluorometry. Phototoxicity of RBCNT conjugate against E. coli was studied using a green light of 50 mW and radiant exposure of 1674.7 J/ cm(2) for 10 min. The antibiofilm activity and mechanism of action of RBCNT conjugate in presence of light was evaluated. Results: The loading and encapsulation was found to be 15.46 +/- 1.05 and 61.85 +/- 4.23% respectively. The photodynamic inactivation of planktonic cells of E. colt was found to 5.46 and 3.56 log(10) CFU/ml reduction on treatment with RBCNT and RB respectively. The conjugate also exhibited efficient and enhanced antibiofilm activity against E. coll. The study of mechanism of action has confirmed cell membrane and DNA damage were the two main targets of aPDI. Conclusion: This report has concluded the efficient photodynamic inactivation occurred in Gram negative bacteria E. coli due to the increased production of ROS inside the bacterial cells. Hence, the newly synthesized RBCNT conjugate can be efficiently utilized to control infections caused by E. coli.