Bacterial DNA analysis based on target aided self-assembly cycle amplification coupled with DNA-AgNCs/three-way DNA junction

We have constructed a simple, enzyme-free and label-free detection method for bacterial DNA. First, bacterial DNA (T) is designed as a trigger to make the designed metastable hairpin probes P1, P2, P3 (carrying DNA silver nanoclusters sequences) autonomously cross-open to achieve catalytic self-assembly, inducing a three-way DNA junction formation through the catalyzed hairpin self-assembly (CHA) mode. Then, G-rich sequences are introduced to form DNA silver nanoclusters G quadruplex (DNA-AgNCs-G quadruplex), and a strong fluorescence signal can be collected under the action of silver nitrate and sodium borohydride solutions. Through the fluorescent reporter of DNA silver nanoclusters (DNA-AgNCs) and the amplification of CHA, we successfully detected target DNA at concentrations as low as 19.95 fM. Compared with the constructed acyclic system, the sensitivity of this cyclic system is improved about three orders of magnitude. Moreover, this recycling system achieves good selectivity for mismatched target DNA and excellent recovery rate in practical samples. Therefore, bacterial DNA analysis based on target-aided self-assembly cycle amplification coupled with DNA-AgNCs/three-way DNA junction is successfully developed, promising its great application in biological sensing.