In situ amplification signaling-based autonomous aptameric machine for the sensitive fluorescence detection of cocaine.

The development of autonomous DNA machines and their use for specific sensing purpose have recently attracted considerable research attention. In existing autonomous machines, the target recognition process and signal transduction are separated from each other. This results in misunderstanding of the operation behavior, and the assay capability is compromised when serving as a sensing tool. In this communication, the integrated signal transduction-based autonomous aptameric machine, in which the recognition element and signal reporters are integrated into a DNA strand, is developed. This new machine can execute the in situ amplification of target binding-induced signal. The authentic operation behavior of autonomous DNA machine is discovered: the machine's products directly hybridize to the "track" rather than to the signaling probes. Along this line, the machine is employed to detect the cocaine in a more straightforward fashion, and improved assay characteristics (for example, the dynamic response range is widened by more than 500-fold) are achieved. Our efforts not only clarify the concept described in traditional autonomous DNA machines but also have made technological advancements that are expected to be especially valuable in designing nucleic acid-based machines employed in basic research and medical diagnosis.