Dual-signal switching biosensor for acetamiprid: A target-responsive aptamer platform liberating bifunctional Mn-doped carbon dots

Acetamiprid (ACE), a typical neonicotinoid pesticide, has raised significant environmental and food safety concerns due to its persistent residues. Herein, we developed a fluorescent/colorimetric dual-mode sensor based on bifunctional Mn-doped carbon dots (Mn-CDs). The Mn doping strategy generates abundant catalytically active sites, not only endowing oxidase-like activity, which can catalyze colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue products, while simultaneously retaining the intrinsic fluorescence property. Magnetic beads (MBs) conjugated with ACE aptamer (Apt) (MBs@Apt) and Mn-CDs conjugated with DNA1 (Mn-CDs@DNA1) were engineered for hybridization. Upon ACE addition, it will trigger competitive displacement of Mn-CDs@DNA1 from MBs, inducing simultaneous colorimetric and fluorescent signal changes. This displacement mechanism enables dual-mode ACE quantification with high sensitivity (LOD = 15.36 fg/mL for fluorescence mode and 57.54 fg/mL for colorimetric mode) and selectivity. The sensor achieves reliable detection in complex matrices, providing a rapid, high-performance solution for pesticide monitoring.