Highly selective and sensitive detection of adenosine utilizing signal amplification based on silver ions-assisted cation exchange reaction with CdTe quantum dots

Adenosine (AD) is a biomarker for monitoring the progress of lung cancer and its analysis in biological fluids of patients is significant. Here, we report a novel signal amplification platform for the sensitive and selective monitoring of AD in the biological fluids on the basis of silver ions-assisted cation exchange reaction with CdTe quantum dots (QDs). The AD aptamer was engineered to consist of two pieces of ssDNA which were respectively attached to Fe3O4 magnetic nanoparticles and CdTe QDs. In the presence of AD, it would reassemble the two pieces of ssDNA into the intact aptamer tertiary structure, and then form the stable nanoparticle sandwich structure. After magnetic separation, the final fluorescence signal with amplification process based on silver ions-assisted twice cation exchange reactions would make AD detection more sensitive, compared with directly measuring the fluorescence intensity of sandwich structure. The platform exhibits excellent sensitivity and high specificity, with a detection limit of 0.217 nM for AD. Moreover, the present platform was successfully applied to the determination of AD in urine samples of lung cancer patients and the range of the recoveries was from 90％ to 106％. The results revealed that the developed platform may provide a promising analytical platform for various target molecules in the biomedical field and clinical diagnosis.