Chemiluminescence of coelenterazine catalyzed by cyclodextrins as a luminescence reference standard for luminometers v1

Abstract

Bioluminescence and chemiluminescence are widely used in sensitive detection methods in biomedical sciences and analytical chemistry. A limitation of this type of measurements is that luminometers and platereaders do not directly quantify absolute quantum output of the reaction but report "relative luminescence units" (RLU) which are specific for a given instrument and reaction vessel design. At the same time, there are no simple and convenient luminescence reference standards that would have been universally available, so results (RLU measurements) reported by different instruments and laboratories usually cannot be directly compared.I have found that cyclodextrins -which are often used to solubilize coelenterazine (CTZ) analogs and other compounds in water buffers -catalyze a weak chemiluminescence of CTZ (and its analogs). Chemiluminescence of 20 µM CTZ in the presence of 10 mM β-cyclodextrin or 10 mM trimethyl-β-cyclodextrin in the 50 mM Naphosphate buffer (pH 7.40) can be used as a simple and convenient reference standard to define and compare RLU readings obtained by different instruments. This system is composed of only small molecules of a defined chemical composition which are not expensive and available in high purity from multiple suppliers making this system convenient for the general use as a luminescence reference standard.