A ternary probe for target-triggered autonomous multi-branch rolling circle amplification for highly sensitive colorimetric sensing of platelet-derived growth factor BB

Highly sensitive detection of protein biomarkers has an important role in clinical diagnosis and disease treatment. On the basis of a newly designed ternary probe containing the aptamer, primer and circular DNA sequences, we have established an ultrasensitive and label-free colorimetric approach for detecting platelet-derived growth factor BB protein biomarkers via a target-triggered autonomous multi-branch rolling circle amplification (mbRCA) strategy. The target molecules specifically bind the aptamer sequences in the ternary probes and causes the configuration transition of the primers to trigger mbRCA generation of numerous of G-quadruplex sequences with the presence of the assistance hairpin. Hemin further associates with these G-quadruplexes to yield many hemin/G-quadruplex DNAzymes with the horseradish peroxidase-mimicking function, which catalyze the substrate solution to induce intense color transition for ultrasensitive and label-free colorimetric determination of the target molecules with a 0.055 pg mL−1 of detection limit in the range of 0.1–1000 pg mL−1. This aptamer-based sensing method exhibits high selectivity and can achieve the detection of low levels of protein biomarkers in diluted serum samples, which offers the developed approach new opportunities for detecting other trace protein biomarkers for the purpose of early disease diagnosis.