Sensitive ratiometric electrochemical detection of microRNA-21 based on dual signal amplification of AuNPs@Fc@MgAl-LDH coupled with MB-cDNA@AuNPs.

Non-coding RNAs are critical tumor biomarkers, rendering innovations in their detection technologies highly significant. To overcome the limitations of conventional single-signal electrochemical biosensors (susceptibility to interference, insufficient stability), this study developed a novel ratiometric electrochemical DNA biosensor with dual-signal amplification. Its core novelty is the rational integration of two synergistic nanomaterials: Ferrocene-functionalized MgAl-layered double hydroxide (Fc@MgAl-LDH, as stable immobilization matrix and internal reference signal source) and AuNPs@Fc@MgAl-LDH coupled with MB-cDNA@AuNPs, which construct a cascaded signal amplification pathway. The sensing mechanism involves two-stage amplification: Primary by high-loading-capacity AuNPs@Fc@MgAl-LDH, secondary by MB-cDNA@AuNPs hybridizing with electrode-immobilized microRNA-21 (miRNA-21). The ratiometric signal (IMB/IFc) enables built-in correction, boosting detection accuracy and reproducibility. After systematic optimization, the sensor has a wide linear range (1.0 fM-0.1 nM) and an ultra-low LOD of 0.757 fM, eliminating RNA extraction/enzymatic amplification to simplify operation. Serum validation shows high accuracy (95.3%-101.4% recovery), indicating strong clinical diagnostic application potential.