DNA nanodevices monitored with fluorogenic looped-out 2-aminopurine†
We report several DNA nanodevices monitored with fluorogenic looped-out 2-aminopurine. It is found that looped-out 2-AP, an analogue of adenine, in split parallel G-quadruplexes, triplexes and duplexes always shows much higher fluorescence intensity than that in single- or double-stranded DNAs, due to the weaker quenching effects derived from the reduced base stacking environments. Taking advantage of these traits, we introduce a new strategy to monitor the behaviours of DNA nanodevices via the fluorescence signal output by utilizing changes in the base stacking environment of 2-AP. As proof-of-principle experiments, two nanoplatforms for detecting disease genes, as well as a triplex nanoswitch, are constructed and monitored by fluorogenic looped-out 2-AP, illustrating that fluorogenic looped-out 2-AP holds great promise for reading the behaviours of diverse DNA nanodevices. Compared with conventional fluorescence labelling, looped-out 2-AP as a reporter shows good photostability and can be quenched by base-pairing, thereby providing an efficient quencher-free methodology for monitoring DNA nanodevices.