Hybridization chain reaction (HCR) for amplifying nanopore signals.

Circulating tumor DNA (ctDNA) in the blood is an important biomarker for noninvasive diagnosis, assessment, prediction and treatment of cancer. However, sensing performance of solid nanopore is limited by the fast kinetics of small DNA targets and unmatched dimensions. Here, we combines hybridization chain reaction (HCR) with nanopore detection to translate the presence of a small DNA target to characteristic nanopore signals of a long nicked DNA polymer. The amplification of nanopore signals obtained by HCR not only overcomes the functional limitation of solid nanopore, but also significantly elevates both selectivity and signal-to-noise ratio, which allows to detect ctDNA at a detection limit of 2.8 fM (S/N = 3) and the single-base resolution. Furthermore, the proposed method can apply in detection of ctDNA of KRAS G12DM in serum sample.