Acetylcholinesterase Immobilized on Au Surfaces for the Detection of Organophosphate Pesticides: A Model for Enzyme-Based Biosensors.

Immobilized enzymes offer several advantages for biosensing, including high specificity and reusability, but their practical implementation is often hindered by a significant loss in substrate binding or other catalytic activity upon immobilization. In this work, we have demonstrated a simple and robust method for the detection of organophosphate pesticides (OPs) using acetylcholinesterase (AChE) directly adsorbed on bare Au surfaces. Our sensor exhibits a remarkably low limit of detection (149 pM) for paraoxon (POx), a model organophosphate, retains ∼70% of its activity after multiple cycles of inhibition and reactivation, and maintains functionality in complex matrices such as orange juice and soil runoff. This work represents a significant advance in immobilized enzyme-based sensing and establishes a model for the development of biosensors using similar immobilization strategies for other enzymes.