Sensitive and Selective DNA Detection Based on Lambda Exonuclease Assisted Signal Amplification

A new versatile chemiluminescence biosensing platform with G-Quadruplexes/Hemin DNAzyme and lambda exonuclease (lambda exo) assisted signal amplification was designed for sensitive detection of DNA. The system involved target DNA, phosphate-DNA, auxiliary DNA and hairpin DNA. The selective digestion of lambda exo to 5'-phosphorylated strand of phosphate-DNA-auxiliary DNA-target DNA duplex sandwich structure resulted in the release of target DNA and auxiliary DNA. The released target DNA hybridized with another phosphate-DNA-auxiliary DNA duplex to trigger the target DNA recycling, while the released auxiliary DNA hybridized with hairpin DNA to activate DNAzyme segments. The activated DNAzyme segments interacted with hemin to form stable G-Quadruplexes/Hemin DNAzymes that could catalyze H2O2-mediated oxidation luminol to produce chemiluminescence signals. In the presence of 10 nits lambda exo, 1.0 x 10(-3) M luminol, 3.0 x 10(-2) M H2O2 and pH 9.0 buffer solution, the relative chemiluminescence intensity of luminol was linearly related with the concentrations of target DNA in the range of 2.0 x 10(-12) M to 8.0 x 10(-9) M. This unique analysis strategy provided a detection limit down to 7.0 x 10(-14) M. The present method was successfully applied to the determination of target DNA in serum samples, which was also capable of discriminating mismatched DNA from perfectly matched target DNA with a high selectivity.