Highly sensitive label-free multi-signal sensing platform for Kras gene detection by exonuclease assisted target recycling amplification based on AIZS QDs

Abstract

In this study, a new multi-channel biosensor was constructed with exonuclease assisted target recycling signal amplification to sensitively determine Kras gene. The hairpin DNA (h-DNA) contained a recognition sequence to target Kras gene and can specifically hybridized with Kras gene. In the presence of Kras gene, G-quadruplex could be produced through exonuclease III (Exo III) assisted target recycling amplification strategy and then Kras gene was used as the trigger to initiate the next recycling. When hemin was introduced, a large quantity of hemin/G-quadruplex DNAzymes were formed to catalyze the oxidation of 2,4-dichlorophenol (2,4-DP). 4-aminoantipyrine (4-AP) could couple with the oxidation product of 2,4-DP to produce a red adduct (quinone imine) with a characteristic absorbance peak at 506 nm, resulting in the fluorescence quenching of AIZS QDs. Based on the changes of fluorometric and colorimetric dual-signals, Kras gene activity was sensitively detected with the limits of detection as low as 0.12 pM and 0.85 pM, respectively. Meanwhile, our sensing system could realize the visual detection through the color change of the reaction solution. Furthermore, the sensing platform showed satisfactory results for measuring the Kras gene in human serum and showed great potential in diagnostic analysis.