Multifunctional aptamer probe mediated cascade amplification for label-free detection of adenosine

Herein, a multifunctional aptamer probe mediated cascade amplification strategy has been constructed for sensitive and label-free detection of adenosine. First, the multifunctional aptamer probe was designed with an aptamer for adenosine identification and a template for cascade amplification. These two regions could partially hybridize with each other and formed a stem-loop structure. Thus, in the absence of adenosine, the probe could be inhibited by itself and the interference signals could be reduced effectively. In the presence of adenosine, the probe identified the adenosine, resulting in the conformational transformation and the release of the template. Then, the 3′-end of the probe-adenosine complex acted as primer to trigger the cascade amplification of strand displacement amplification (SDA) and catalytic hairpin assembly (CHA), yielding a lot of G-quadruplex. Finally, by inserting N-methy mesoporphyrin IX (NMM), an enhanced and label-free fluorescence signal was achieved. This strategy suggested a high sensitivity with a detection limit of 1.3 × 10−7 mol/L that attributes to the low interference signals of the probe and the amplification capability of the cascade amplification. Moreover, adenosine analysis in human urines was performed, indicating that this method was reliable and could be further used in the early clinical diagnosis and medical research.