Ultrasensitive electrochemical analysis of two analytes by using an autonomous DNA machine that works in a two-cycle mode.

We report a novel autonomous DNA machine for amplified electrochemical analysis of two DNAs. The DNA machine operates in a two-cycle working mode to amplify DNA recognition events; the working mode is assisted by two different nicking endonucleases (NEases). Two bio-barcode probes, a ZnS nanoparticle (NP)-DNA probe and a CdS NP-DNA probe, were used to trace two target DNAs. The detection system was based on a sensitive differential pulse anodic stripping voltammetry (DPASV) method for the simultaneous detection of Zn(II) and Cd(II) tracers, which were obtained by dissolving the two probes. Under the optimised conditions, detection limits as low as 5.6×10(-17) (3σ) and 4.1×10(-17)  M (3σ) for the two target DNAs were achieved. It has been proven that the DNA machine system can simultaneously amplify two target DNAs by more than four orders of magnitude within 30 min at room temperature. In addition, in combination with an aptamer recognition strategy, the DNA machine was further used in the aptamer-based amplification analysis of adenosine triphosphate (ATP) and lysozyme. With the amplification of the DNA machine, detection limits as low as 5.6×10(-9)  M (3σ) for ATP and 5.2×10(-13)  M (3σ) for lysozyme were simultaneously obtained. The satisfactory determination of ATP and lysozyme in Ramos cells reveals the good selectivity and feasibility of this protocol. The DNA machine is a promising tool for ultrasensitive and simultaneous multianalysis because of its remarkable signal amplification and simple machine-like operation.