A novel DNA-quantum dot nanostructure electrochemiluminescence aptamer sensor by chain reaction amplification for rapid detection of trace Cd2+

Abstract

This work proposes a new enzyme-free electrochemiluminescence (ECL) sensing platform based on a novel DNA-quantum dot (QD) nanostructure and hybridization chain reaction (HCR) amplification for the trace detection of Cd²⁺. First, the Cd²⁺ aptamer triggers the HCR amplification circuit, so abundant biotin-labeled DNAs are introduced to the electrode, and then biotin as a linker specifically captures a large number of streptavidin (SA)-CdS QD complexes, showing very high ECL signals. After the present Cd²⁺ binds to its aptamer on the electrode, it causes the linear DNA structure loaded with a large number of QDs to break away from the electrode, resulting in a significantly decreased ECL response. This method combines the HCR-amplified DNA structure-QD signal with the specificity of the biotin–avidin reaction, enabling the rapid detection of Cd²⁺ in complex water. Therefore, this sensor provides a novel and competitive strategy for detecting heavy metal ions in actual samples, which extends its application to practical settings, such as environmental monitoring and biomedical diagnostics.