Stable hierarchical PILs-encapsulated SERS biosensor: Ultrasensitive detection of trace organophosphorus pesticides via enzymatic signal modulation

An exceptionally stable biosensor for pesticide monitoring was engineered through the assembly of a multilayered core-shell nanostructure incorporating polymeric ionic liquid (PIL)-encased acetylcholinesterase (AChE). In this design, AChE is encapsulated within PILs to form the inner core, PILs serve as the intermediate layer, and silver nanoparticles (Ag NPs) are uniformly assembled on the outer layer to provide surface enhancement effects. The PILs microspheres provide a biocompatible microenvironment to stabilize AChE activity while enabling tunable charge density and ordered structural frameworks to guide the uniform assembly of Ag NPs into nanoscale arrays. This precise arrangement of Ag NPs amplifies localized electromagnetic coupling, significantly enhancing surface-enhanced Raman scattering (SERS) signals. The composite was further modified with 2-(pyridyldithio)ethylamine (PDEA), which functions as a SERS reporter through its pyridine ring vibrations. The detection mechanism involves two critical steps: (1) AChE hydrolyzes acetylthiocholine (ATCl) to generate thiocholine (TCl), which cleaves PDEA's disulfide bonds, releasing pyridine rings and attenuating SERS signals; (2) Organophosphate pesticides inhibit AChE activity, thereby reducing TCl production and preserving PDEA's signal intensity for indirect quantification. Owing to the synergistic integration of hierarchical stability, electromagnetic enhancement, and molecular recognition capabilities, the multilayer core-shell structure (denoted as AChE@PILs@Ag NPs-PDEA) achieves ultrasensitive detection across a wide linear range from 3.8 × 10 −7 to 3.8 × 10 −12  M, reaching an exceptional detection limit of 1.38 × 10 −13  M. The biosensor demonstrates robust thermal stability, long-term storage reliability, and reliable matrix interference resistance in food/environmental matrices (tomato homogenates, tap water), validating its practicality for on-site pesticide monitoring in agricultural products under variable environmental conditions.