Metallo-base pair-mediated DNA probe for label-free, amplified and catalytic electrochemical detection of metallothionein

Abstract

Metallothionein (MT) is an important biomarker for the early diagnosis of heavy metal toxicity and malignancy and the detection and quantification of MT therefore has important biomedical significances. In this work, we present a new metallo-base pair-mediated DNA probes for label-free and sensitive electrochemical assay of MT via hybridization chain reaction (HCR) and catalytic redox recycling signal amplifications. The DNA probe is immobilized on the gold electrode to prepare the sensor. Due to the strong binding capability between MT and the metal ions in the DNA probes, the presence of the MT target molecules leads to both disruption of the duplex structure of the DNA probes and the release of ssDNA strands, which trigger subsequent HCR formation of long dsDNA polymers on the electrode from two hairpins. Large amounts of [Ru(NH3)6]Cl3 can then be captured onto the dsDNA polymers to show substantially enhanced catalytic currents with co-existence of K3[Fe(CN)6] for highly sensitive assay of MT down to 0.15 nM in the range of 0.5–500 nM. The sensor also shows the capability for monitoring MT in diluted human serum samples, indicating its great potential for detecting various metal ion binding proteins and small molecules for different application purposes.