Daylight-stimulated antibacterial activity for sustainable bacterial detection and inhibition

Owing to the abuse of antibiotics, antibiotic resistance is spreading fast, which poses a potential threat to human beings. However, methods of the detection of bacterial viability, e.g., the plate count method, high-resolution microscopy, etc., require complicated preparation and expensive facilities, which restricts their further application. Here, we report a multifunctional nanocomplex containing polyethyleneimine modified with arginine (Arg) and β-cyclodextrin (CD) (PEI-CD-Arg) and an aggregation-induced emission (AIE) active molecule (4,4'-(1,2-diphenylethene-1,2-diyl)bis(1,4-phenylene)diboronic acid, TPEDB), namely, PEI-CD-Arg-TPEDB, which exhibited non-resistance and significant antibacterial potency by means of an initial cationic component for the electrostatically propelled accumulation of bacteria and a subsequent phototoxic component for the daylight-regulated generation of reactive oxygen species (ROS) to damage the bacteria. Moreover, TPEDB is capable of imaging dead bacteria and the long-term identification and surveillance of bacteria (residues). Upon contact with bacteria, the emission of PEI-CD-Arg-TPEDB increased because of restrictions on the intramolecular motion of TPEDB, and then the emission decreased to a constant value, accompanied by the death of the bacteria, which was slightly higher than that of the initial fluorescence of PEI-CD-Arg-TPEDB alone. Finally, the dead bacteria were imaged and no washing step was required in the imaging process. Therefore, this new type of multifunctional nanomaterial should be highlighted as a rational alternative to antibiotics for the detection and elimination of bacteria.