Chemiluminescence assay for detection of 2-hydroxyfluorene using the G-quadruplex DNAzyme-H2O2-luminol system

A chemiluminescence (CL) based assay is described for the determination of the environmental pollutant 2-hydroxyfluorene (2-HOFlu) which is found to inhibit the CL of a system composed of the G-quadruplex/hemin complex (a DNAzyme), H2O2, and luminol. The G-rich aptamer PW17 is transformed to a potassium(I)-stabilized G-quadruplex-hemin complex which displays peroxidase-like activity to catalyze the oxidation of luminol by H2O2 which is accompanied by strong blue CL emission. On addition of 2-HOFlu, it will participate in the Gquadruplex DNAzyme-mediated oxidation by H2O2. As a result, CL intensity is decreased. The difference in CL intensity (Delta I) before and after addition of 2-HOFlu serves as the signal for its quantitation. In water of pH 9.0, a linear relationship is found for the 1 nM to 1 mu M concentration range, with a 0.2 nM detection limit. The assay is highly selective over other fluorene derivatives. It was successfully applied to the determination of 2-HOFlu in spiked lake water samples. The method is rapid, cost-effective and convenient. Conceivably, it has a wide scope in that it may be applied to other target pollutants for which G-quadruplexes are available.