Direct Detection of Nucleic Acid with Minimizing Background and Improving Sensitivity Based on a Conformation-Discriminating Indicator.

As well known, the nucleic acid indicator-based strategy is one of the major approaches to monitor the nucleic acid hybridization-mediated recognition events in biochemical analysis, displaying obvious advantages including simplicity, low-cost, convenience and generality. However, conventional indicators either hold strong self-fluorescence or can be lighted by both ssDNA and dsDNA, lacking absolute selectivity for a certain conformation, always with high-background interference and low sensitivity in sensing; and additional processing (e.g. nanomaterial-mediated background suppression and enzyme-catalyzed signal amplification) is generally required to improve the detection performance. In this work, a carbazole derivative, EBCB, has been synthetized and screened as a dsDNA-specific fluorescent indicator. Compared with conventional indicators under the same conditions, EBCB displayed a much higher selective coefficient for dsDNA, with little self-fluorescence and negligible effect from ssDNA. Based on its superior capability in DNA conformation-discriminating, high sensitivity with minimizing background interference was demonstrated for direct detection of nucleic acid, and monitoring nucleic acid-based circuit with good reversibity, resulting in low detection limit and high capability for discriminating base-mismatching. Thus, we expect that this highly-specific DNA conformation-discriminating indicator will hold good potential for application in biochemical sensing and molecular logic switching.