Self-assembled micellar photosensitizers for combating bacterial infections and activating systemic acquired resistance

Abstract

Bactericides are still the main tools for managing plant diseases, while long-term and large-scale use often brings many problems, such as resistance to the applied chemicals and damage to ecological environment. To address these issues, we develop visible-light-absorbing photosensitizers (TTT and MTTT) with aggregation-induced emission feature, and further assemble them with a cationic surfactant octadecyltrimethylammonium bromide (OTAB) to form the micellar photosensitizer (MTTT@OTAB). The fabricated MTTT@OTAB can target phytopathogen Pseudomonas syringae pv. tomato DC3000 at the infection sites of the model plant Arabidopsis thaliana via electrostatic interactions, and then eliminate them through photodynamic effect under white light irradiation. More importantly, reactive oxygen species (ROS) produced through the photosensitization of MTTT@OTAB can also induce an immune response known as systemic acquired resistance by regulating the ROS-azelaic acid (AzA)- glycerol-3-phosphate (G3P) signaling pathway in Arabidopsis, thereby preventing secondary infections. Collectively, the present study demonstrates the development of photosensitizer systems with robust photodynamic effect under the normal plant growth conditions, which holds great potential as alternatives to the conventional agrochemicals for sustainable protection of agriculture against destructive bacterial infections.