Proximity ligation assay induced and DNAzyme powered DNA motor for fluorescent detection of thrombin
A novel DNA motor for thrombin detection was described here based on proximity ligation assay (PLA) induced DNAzyme recycling cleavage. Fluorophore labeled DNA is modified on gold nanoparticles (AuNPs) and the fluorescent signal is quenched by AuNPs. The PLA between target thrombin and two aptamers induces the forming of Mg2+-dependent DNAzyme. The fluorophore labeled DNA is cleaved circularly by the DNAzyme, releasing the fluorescent fragment from AuNPs surface. The cleavage and rebinding process create a processive walking along AuNPs surface track. As a result, the fluorescent intensity recovers significantly. A good linear relationship is obtained between the ratio of fluorescence intensity and thrombin concentration in the range from 10 pM to 10 nM. The limit of detection is calculated to be 4 pM. These results are comparable or even better than other amplification based methods.