Fluorogenic substrate screening for G-quadruplex DNAzyme-based sensors

Due to the inherent higher sensitivity of fluorescence detection than colorimetric detection, it is necessary to screen out a suitable fluorogenic substrate for G-quadruplex DNAzymes to improve the sensitivities of G-quadruplex DNAzyme-based sensors. Herein, seven candidates were tested to determine the possibilities of them as fluorogenic substrates. Among these candidates, tyramine hydrochloride gave the maximum signal-to-background ratio for the sensing systems with and without G-quadruplexes, and thus was recommended as the fluorogenic substrate for the sensors that are developed on the basis of target-triggered G-quadruplex formation or destruction. 10-acetyl-3,7-dihydroxyphenoxazine gave the maximum fluorescence signal change between the sensing systems without and with H2O2, thus was recommended as the fluorogenic substrate for the sensors targeting the detection of H2O2 or H2O2-related analytes. In a model system of G-quadruplex DNAzyme-based Cu2+ sensor, fluorescence detection using tyramine hydrochloride as fluorogenic substrate could decrease the detection limit from 4 nM to 0.7 nM compared with the colorimetric detection.