A dual-mode sensor based on an intramolecular catalytic hairpin assembly strategy for detecting survivin mRNA

A dual-mode sensor based on intramolecular catalytic hairpin assembly strategy (intra-CHA) is proposed for Survivin mRNA detection. Intra-CHA, a triplex complex of tetraferrocene-labeled H1/H2, shortens H1-H2 distance and increases their local concentrations, accelerating reaction by 2.8-fold vs. free-CHA. Ruthenium-based covalent organic frameworks (RuCOFs) with Ru(dcbpy)₃²⁺ as luminophore has dual fluorescence-electrochemiluminescence (FL-ECL) properties. EDTA-incorporated RuCOFs@EDTA expands active sites, enhancing ECL efficiency 8-fold. Intra-CHA system is covalently conjugated to RuCOFs@EDTA through amide bond linkages. Target mRNA-triggered strand displacement reactions induce structural reconfiguration of the intra-CHA probes, resulting in controlled spatial segregation of tetraferrocene from the RuCOFs@EDTA interface. This results in the recovery of FL and ECL signals, enabling rapid and highly sensitive detection of Survivin mRNA. Experimental results show that the detection limits reach 0.04 fM (in the FL mode) and 0.009 fM (in the ECL mode) respectively, with excellent selectivity, stability, and reproducibility. The system has been successfully applied to detect Survivin mRNA in actual serum samples, providing a novel strategy for Survivin mRNA detection and paving the way for developing future diagnostic strategies for early cancer screening.