A turn-on near-infrared fluorescent probe for monitoring carbon monoxide in bacterial pneumonia and cadmium ion induced abiotic stress responses in plants.

Carbon monoxide (CO) is known as a highly toxic gas being emitted during industrial activities. Recent studies confirmed the roles of CO in various biological processes, such as bacterial pneumonia and plants response to abiotic stresses, that can be evaluated in situ using fluorescence probe technology. In this work, a Nile Red-based near-infrared fluorescence probe (Z1CO) is developed to evaluate CO production in animal and plant systems. The probe Z1CO is designed by conjugating allyl formate moiety that responds to CO specifically to Nile Red fluorophore. In the presence of CO with palladium chloride (PdCl2), Tsuji-Trost reaction facilitates the cleavage of the allyl formate moiety, resulting in bathochromic-shift of absorption spectra and enhancement of the emission at 665 nm within 60 min. Z1CO features several advantages, including near-infrared emission, large Stokes shift (75 nm), high selectivity, low detection limit (0.84 μM) and low cytotoxicity in vitro, enabling its applications in monitoring CO production in animal and plant systems. Visualization of CO production in lipopolysaccharide (LPS)-induced acute pneumonia mouse model, monitoring of CO-mediated inflammatory treatment responses and CO functions in plants response to cadmium ion (Cd2 +)-induced abiotic stress are then demonstrated. This work thus provides a new tool for evaluating the roles of CO in animal and plant systems.