Dual recycling signal amplification strategy based on autocatalytic entropy-driven circuit and DNAzyme for colorimetric detection of platelet-derived growth factor-BB.

Platelet-derived growth factor-BB (PDGF-BB), an important protein biomarker, is closely associated with tumorigenesis. Therefore, it is important to develop a simple and sensitive method to detect PDGF-BB. Herein, we developed a dual recycling signal amplification strategy for colorimetric and sensitive detection of PDGF-BB using a PDGF-BB specific aptamer. In the presence of PDGF-BB, the first entropy-driven circuit (EDC) reaction cycle was triggered for colorimetric signal amplification. Meanwhile, a catalytic Mg2+-dependent DNAzyme was formed on one side of the EDC product, which could cleave its substrate and generate numerous "mimic trigger" DNA products. Then, an autocatalytic EDC (AEDC) reaction was triggered by the "mimic trigger" DNA, and the signal amplification efficiency of this colorimetric assay was significantly improved. This AEDC- and DNAzyme-based colorimetric assay showed a good linear range from 5.0 to 100 nM for PDGF-BB and the limit of detection was calculated to be 2.2 nM. In addition, PDGF-BB has been quantitatively detected in human serum samples. This colorimetric assay can be easily extended to detect different protein biomarkers by using other recognition elements (aptamers) and shows great potential for clinical diagnosis and prognosis.