A Cu(II)-benzoyl hydrazone based fluorescent probe for lipopolysaccharides

A novel fluorescent compound 7-diethylamino-3-[4׳-N-((2-ethoxy)ethanol)methyl aminobenzoylhydrazone]methyl coumarin (I) was synthesized and employed as a fluorescent probe for detecting lipopolysaccharides (LPS). This coumarin-based probe exhibited high fluorescence in aqueous environment, which could be quenched in the presence of Cu2+ ion due to the complexation between I and Cu2+. However, the fluorescence of I can be recovered upon addition of LPS, because the binding between LPS and Cu2+ ion is stronger than that between I and Cu2+ ion, which disassociates the complexation of I and Cu2+ ion and releases the fluorescence of I. Therefore, this three-component sensing system can be used to detect lipopolysaccharides in a facile manner. In addition, biological imaging studies have demonstrated that the probe can be used to evaluate the biosorptive capacity for Cu2+ ion in living bacteria.