Biobar-coded gold nanoparticles and DNAzyme-based dual signal amplification strategy for ultrasensitive detection of protein by electrochemiluminescence.

A dual signal amplification strategy for electrochemiluminescence (ECL) aptasensor was designed based on biobar-coded gold nanoparticles (Au NPs) and DNAzyme. CdSeTe@ZnS quantum dots (QDs) were chosen as the ECL signal probes. To verify the proposed ultrasensitive ECL aptasensor for biomolecules, we detected thrombin (Tb) as a proof-of-principle analyte. The hairpin DNA designed for the recognition of protein consists of two parts: the sequences of catalytical 8-17 DNAzyme and thrombin aptamer. Only in the presence of thrombin could the hairpin DNA be opened, followed by a recycling cleavage of excess substrates by catalytic core of the DNAzyme to induce the first-step amplification. One part of the fragments was captured to open the capture DNA modified on the Au electrode, which further connected with the prepared biobar-coded Au NPs-CdSeTe@ZnS QDs to get the final dual-amplified ECL signal. The limit of detection for Tb was 0.28 fM with excellent selectivity, and this proposed method possessed good performance in real sample analysis. This design introduces the new concept of dual-signal amplification by a biobar-coded system and DNAzyme recycling into ECL determination, and it is promising to be extended to provide a highly sensitive platform for various target biomolecules.