Target-Driven Annular DNA Walker Coupled with Electrochemiluminescent Silicon Quantum Dots for APE1 Bioanalysis

Functional DNA walkers with substantial nanostructures have been extensively investigated; however, their stability still faces challenges when exposed to diverse nuclease in clinical biological samples, resulting in the unreliability of actual assessment. This work proposed a target-driven annular DNA walker with enhanced stability enabling the sensitive and reliable response to different concentrations of apurinic/apyrimidinic endonuclease 1 (APE1), by preparing silicon quantum dots (SiQDs) as electrochemiluminescence (ECL) emitters. Specifically, the SiQDs showed significant strong and stable ECL signals by purifying the microenvironment of SiQDs through the dialysis removal of the gel-like layers surrounding the SiQDs. The relative standard deviation (RSD) of their ECL signal had been improved 16.59 times under consecutive scanning compared to that of SiQDs without dialysis, demonstrating a significant improvement in ECL stability. Subsequently, in the presence of APE1, the designed annular DNA walker was activated to move along the numerous quenching probes within the continuous cross-based DNA orbits, which were immobilized to the SiQD-modified electrode, providing ECL readout signals. The linear range of this ECL biosensor was 1.0 × 10^-13 U·μL^-1 to 1.0 × 10^-7 U·μL^-1, and the limit of detection (LOD) was as low as 1.766 × 10^-14 U·μL^-1. This work provides a novel structure of a DNA walker with nuclease resistance for clinical sample detection and designs a new strategy for synthesizing SiQDs with favorable ECL performance, tremendously expanding the ECL application of SiQDs.