Porous silicon-modified electrode for electrochemical pesticide biosensor

An electrochemical biosensor for organophosphorus pesticides detection has been developed by immobilizing acetylcholinesterase (AChE) enzyme, through a multi-step functionalization process, on porous silicon (PSi) surface. The PSi surface was functionalized using thermal hydrosilylation creating acidic chains to stabilize the surface. The AChE was covalently attached on the PSi surface and exhibited a good enzyme activity in the presence of its substrate acetylthiocholine iodide (ATI) by forming thiocholine. The response of the device shows a linear evolution over a wide concentration range of ATI from 0.15 to 0.65 mM with a good correlation coefficient. Furthermore, AChE revealed high affinity to its substrate ATI from calculated Michaelis-Menten constant (K-m), which is about 0.249 mM. The effect of the organophosphorus pesticide malathion was monitored by measuring the current oxidation in ATI solution. After incubation, it shows a drastic decrease in the electrochemical response in the presence of the pesticide at different concentrations (2-8 nM).