Electrochemiluminescence Bioassays with a Water‐Soluble Luminol Derivative Can Outperform Fluorescence Assays

The most efficient and commonly used electrochemiluminescence (ECL) emitters are luminol, [Ru(bpy) 3 ] 2+ , and derivatives thereof. Luminol stands out due to its low excitation potential, but applications are limited by its insolubility under physiological conditions. The water‐soluble m ‐carboxy luminol was synthesized in 15 % yield and exhibited high solubility under physiological conditions and afforded a four‐fold ECL signal increase (vs. luminol). Entrapment in DNA‐tagged liposomes enabled a DNA assay with a detection limit of 3.2 pmol L −1 , which is 150 times lower than the corresponding fluorescence approach. This remarkable sensitivity gain and the low excitation potential establish m ‐carboxy luminol as a superior ECL probe with direct relevance to chemiluminescence and enzymatic bioanalytical approaches.