Detecting adenosine with an autonomic cycle of cascading DNA polymerizations

In this study, an autonomic DNA-reaction cycle involving two cascading DNA polymerization steps was established and utilized for adenosine detection. The reaction cycle was operated based on a probe that was immobilized on the magnetic beads (MBs) and tagged with PbS nanoparticle (NP). Adenosine, as the target, was recognized by its aptamer segment in the probe to initiate the cycle. Two strand-displacement polymerizations took place successively, and in the second polymerization, adenosine was released into the solution, which was then able to initiate another round of cycle. The cycles were automatically repeated, thus adenosine was repetitively utilized as target, amplifying the signal to a great extent. The PbS NP tags were released with the aptamer segments in the cycle, after being separated from the MBs, they were quantified with anodic stripping voltammetry (ASV). It was found that adenosine could be quantified in the range from 2.0 × 10−11 M to 1.0 × 10−9 M. The detection limit was 3.6 × 10−12 M based on 3σ rule. Good selectivity against the analogous nucleosides was shown for this system. The system was also proven to be capable of detecting adenosine in real human serum samples.