Ratiometric fluorescence sensing of bacterial lipopolysaccharide by a simple combination of a cationic dye and an anionic dye.

Two cationic fluorophore coralyne and one anionic fluorophore 9,10-anthracenediyl-bis(methylene)dimalonic acid can form 2:1 ion pair complex in aqueous solutions. The complex experiences dissociation along with significant changes in fluorescence profile in the presence of bacterial lipopolysaccharide, which is utilized to sensitively and selectively detect the bacterial lipopolysaccharide in ratiometric fluorescence mode with the detection limit down to submicromolar concentration.