Proximity hybridization induced bipedal DNA walker and rolling circle amplification for label-free electrochemical detection of apolipoprotein A4

Apolipoprotein A4 (Apo-A4) is considered as a prospective molecular biomarker for diagnosis of depression due to its neurosynaptic toxicity. We develop a proximity hybridization-induced DNAzyme-driven bipedal DNA walker strategy for Apo-A4 quantification based on rolling circle amplification (RCA) triggered by poly adenine binding to Ag nanoparticles (AgNPs). With the help of DNAzyme, the free-running bipedal DNA walker can quickly and sequentially shear a molecular beacon that acts as a primer to initiate the RCA process, producing a large number of long DNA strands containing numerous adenines. The long repetitive adenine strands then absorb large amounts of AgNPs on the electrode interface, which is then electrochemically stripped of the AgNPs. The method has a linear detection range of 0.001 similar to 100 ng mL(-1) and a detection limit of 0.46 pg mL(-1). The presented detection strategy is label-free, which allows high sensitivity and selectivity for detection of a wide range of protein targets by corresponding DNA-based affinity probes, which have potential applications in bioanalysis.

Automated summary

A label-free detection strategy for quantification of Apolipoprotein A4 (Apo-A4) has been developed based on rolling circle amplification (RCA) and proximity hybridization-induced DNAzyme-driven bipedal DNA walker. This method shows high sensitivity and selectivity for a wide range of protein targets.