Lipid Droplet-Specific Red Aggregation-Induced Emission Luminogens: Fast Light-Up of Gram-Positive Pathogens for Identification of Bacteria

Gram-positive (G+) and Gram-negative (G–) bacteria require considerable differences in their therapeutic strategies. Thus, the development of highly efficient techniques for differentiating G+ and G– bacteria is of vital importance for practical clinical applications. Herein, we present 2-((10-ethyl-10H-phenothiazin-3-yl)methylene)-1H-indene-1,3(2H)-dione(PH-ID), which is an electrically neutral, red fluorophore with aggregation-induced enhanced emission (AIEE) characteristic, to selectively stain G+ bacteria membranes with high specificity and sensitivity. The staining result can be accomplished within 10 min and can be read by the naked eye. Lipopolysaccharide (LPS) in the outer leaflet of the membrane of G– bacteria prevents the staining of the bacteria by PH-ID, which is the mechanism underlying the Gram selectivity of PH-ID. This study not only provides a highly efficient method for bacteria imaging and discrimination, but also provides insight into the bacteria imaging mechanism, which is beneficial for the exploration of new electroneutral AIE luminogens for bacteria surveillance applications.