Rapid Detection of Dextromethorphan in Saliva and E-Juice Based on Highly Selective Aptamers

Abstract Dextromethorphan (DXM) is a widely used cough suppressant, and its escalating abuse is a pressing global health concern that necessitates rapid screening tools. However, rapid methods for detecting DXM in complex matrices remain highly limited. Here, we report the first isolation and engineering of DNA aptamers specifically targeting DXM. Using library-immobilized SELEX, we identified high-affinity aptamers (KD ∼ 1–2 μM) with exceptional specificity against various interferents. The lead candidate was rationally truncated into a minimal 27-nucleotide core (DM1–27) that retains full function. Systematic mutagenesis and molecular modeling further delineated the structure–activity relationship governing target recognition. Utilizing this engineered aptamer, we developed two distinct fluorescent platforms: a label-free thioflavin T displacement assay and a fluorophore-quencher labeled hybrid beacon. Both sensors enabled robust DXM quantification within 10 min in human saliva and e-cigarette juice (EJ), achieving limits of detection at low ng/mL-level. Notably, the hybrid beacon significantly improved matrix tolerance by bypassing short-wavelength background interference. This work provides a versatile molecular recognition tool and establishes practical, field-deployable sensing strategies for DXM monitoring.