Target-triggered programming of cascaded catalytic hairpin assemblies for enzyme-free and highly sensitive sensing of cytokines

Sensitive detection and quantification of cytokines can play important roles in immunology research and diseases diagnosis. In this regard, by using a new target-triggered programming of cascaded catalytic hairpin assembly (CHA) signal enhancement strategy, we have developed an enzyme-free approach for the highly sensitive detection of cytokines, where interferon-gamma (IFN-gamma) is selected as the target model molecule. IFN-gamma associates with a hairpin aptamer probe and triggers a conformation change of the aptamer to expose an initiation sequence for the formation of three independent and cascaded CHA of four hairpins into dsDNAs, which results in drastically enhanced fluorescence recovery from the fluorescently quenched hairpin signal probes for detecting IFN-gamma in a dynamic range between 0.001 and 50 nM with detection limit down to 0.6 pM. Furthermore, this elaborately designed signal amplified approach displays efficient selectivity for the target molecules and can realize the detection of IFN-gamma in diluted human serums, demonstrating its potential for monitoring a variety of biomarkers with high sensitivity by using appropriate hairpin aptamer/target molecule pairs.