One Stone, Three Birds: One AIEgen with Three Colors for Fast Differentiating Three Pathogens

Visually identifying pathogens favors the rapid diagnosis at point-of-care testing level. Here, we developed a microenvironment-sensitive aggregation-induced emission luminogen (AIEgen), namely IQ-Cm, for achieving fast discrimination of Gram-negative bacteria, Gram-positive bacteria and fungi by naked-eye. With a twisted donor-acceptor and multi-rotors structure, IQ-Cm shows twisted intramolecular charge transfer (TICT) and AIE properties with sensitive fluorescence color response to the microenvironment of pathogens. Driven by the intrinsic structural difference of pathogens, IQ-Cm with a cationic isoquinolinium moiety and a membrane-active coumarin unit as targeting and interacting groups selectively locates in different sites of three pathogens and gives three naked-eye discernable emission colors. Gram-negative bacteria are weak pink, Gram-positive bacteria are orange-red and fungi are bright yellow. Meanwhile, based on their distinctive fluorescence response, IQ-Cm can directly discriminate three pathogens at the cell level under a fluorescence microscope. Furthermore, we demonstrated the feasibility of IQ-Cm as a visual probe for fast diagnosis of urinary tract infections, timely monitoring of hospital-acquired infection process and fast detection of molds in the food field. This simple visualization strategy based on one single AIEgen provides a promising platform for rapid pathogen detection and point-of-care diagnosis.