DNA-Antibody Conjugation Clamp-Mediated Coordination Quenching for the Ratiometric Detection of CA242

In ratiometric sensors, a conventional strategy for target detection is to modulate one signal via resonance energy transfer (RET), while keeping the other signal constant despite fluctuations in the target concentration. To avoid the drawback of low quenching efficiency caused by long-distance interaction in RET, the selection of functional material can eliminate the adverse effects of long distance through direct contact with the luminophore, thus improving the quenching efficiency. In this work, a U-shaped chain conjugated to the second antibodies (Ab₂) at both terminals was hybridized with ethylenediaminetetraacetic acid (EDTA)-modified signal probe chain capable of inducing signal variation to assemble an antigen-responsive DNA clamp, which responded to the target concentration. When Ab₂ on an antigen-responsive DNA clamp specifically recognized the target antigen, the signal probe chain was released, thereby enabling the coordination of Cu²⁺ on the surface of CdTe: Cu⁺ quantum dots (QDs) with EDTA. Since Cu²⁺ acted as a coreaction accelerator to enhance the response of CdTe: Cu⁺ QDs, the coordination compound locked Cu²⁺, thereby precluding valence state conversions of Cu⁺/Cu²⁺. With the reference signal of CeEu-MOF, the signal of the CdTe: Cu⁺ QDs decreased with an increase in target concentration. The ratiometric sensor constructed on this basis exhibited a wide detection range of 10^-4 - 10³ U/mL and a low limit of detection of 3.21 × 10^-5 U/mL (IUPAC standard), enabling the sensitive and accurate detection and providing a positive reference for the clinical diagnosis of pancreatic cancer.