Assessment of Acetylcholinesterase Activity Using the Gold Nanocluster–MnO₂ Nanosheet Pair for Detection of Paraoxon

The atomically precise gold nanoclusters (AuNCs) and MnO2 nanosheets (MnO2 NSs) were synthesized and characterized as donor and acceptor pairs, respectively. A Förster resonance energy transfer (FRET)-based highly sensitive "turn on–off" fluorescence (FL) response was achieved owing to the strong spectral overlapping between highly bright luminescence of as-synthesized vitamin B1-stabilized gold nanoclusters (VB1–AuNCs) and absorption spectra of manganese oxide nanosheet (MnO2 NS)-based 2D material. The AuNC–MnO2 NSs pair was used as a probe for the assessment of enzymatic activity of acetylcholinesterase (AChE) as an effective alternative to Ellman's reagent. Our work predicts that an abundantly hydrophilic nano gold cluster surface would be a promising material to improve the sensitivity and hydrolytic rate (kcat) of AChE enzymes. The reconciliation and inhibition of AChE for the hydrolysis of acetylthiocholine furnish quantitative turn "on–off" FL signals in the linear range of 0.53–1.6 × 10–8 M of paraoxon. The excellence of this sensor is demonstrated by its exceptionally low limit of detection (LOD) of 1.6 nM and limit of quantification (LOQ) of 4.9 nM values for detection of paraoxon. The applicability of the proposed sensing system was verified using environmental (farm water) and fruit matrixes like tomato, grapes, and apple samples.