Selectivity Enhancement of Pesticide Biosensors via Polymer Coating

This work investigated the effects of polymer films [chitosan (CS), Nafion (NF), and polyvinyl alcohol (PVA)] on the performances of acetylcholinesterase (AChE) biosensors for the selectivity of pesticide types and their concentration levels using principal component analysis (PCA). AChE was immobilized on montmorillonite/gold nanoparticles (Mt/AuNPs). The surface charge of the polymer films significantly influenced sensor performance: NF and PVA films, with negative charges, enhanced the preconcentration of positively charged acetylthiocholine chloride (ATCh), resulting in increased electroactive surface area and current response. In contrast, the positively charged CS film impeded mass diffusion of ATCh, reducing electroactive surface area and current response. Sensor/PVA showed the lowest limit of detection (LOD) for chlorpyrifos and pirimiphos-methyl, while Sensor/CS showed the lowest LOD for carbaryl. The unique response from three different biosensors demonstrated the successful discrimination of the pesticide group and their concentration levels by PCA. The total contribution variance was 99.8%. PC1 suggested the concentration levels, while PC2 was explicitly realized for organophosphate pesticides (negative PC2) and carbaryl (positive PC2). These findings demonstrate that the simple application of polymer coatings, combined with PCA, can significantly improve the selectivity and storage stability of AChE-based biosensors.