Photodynamic Inactivation of Escherichia Coli and Staphylococcus Aureus by Cationic Diketopyrrolopyrroles

Abstract

Diketopyrrolopyrroles (DPP) display remarkable photophysical and electronic properties, and are well-known for their application in the optoelectronic field. Currently, these compounds have gained special relevance for biological applications, including bioimaging, photodynamic therapy or as theranostic agents. In this work, the potential of two new cationic diketopyrrolopyrroles to (photo)inactivate Gram-positive Staphylococcus aureusand Gram-negative Escherichia coli was assessed. Despite the low production of singlet oxygen (1O2), the combined action of these compounds with potassium iodide, after white light activation, triggers the production of reactive iodine species (RIS) which effectively inactivate the bacteria. The photoinactivation efficiency was influenced by the overall charge of the compounds, being both Gram-positive and Gram-negative strains successfully inactivated by the dicationic derivative, whereas the monocationic analogue was only effective against S. aureus.

Keywords: Diketopyrrolopyrrole, Photoinactivation, Photodynamic Inactivation, Reactive oxygen species (ROS), Reactive iodine species (RIS)