Disposable Electrochemical Biosensor Based on Cholinesterase Inhibition with Improved Shelf-Life and Working Stability for Nerve Agent Detection

Organophosphonate compounds such as Sarin are potent toxic nerve agents. The development of fast, simple and miniaturisable analytical systems for the detection of these compounds is an important goal in analytical ­chemistry. In this chapter we present the results obtained in the developing cholinesterase biosensor for nerve agent detection characterised by high shelf and operational stability. Different types of immobilisation were tested immobilizing in different ways the acetylcholinesterase from electric eel and butyrylcholinesterase from horse serum on the screen printed electrodes chemically modified with the electrochemical mediator Prussian Blue (PB-SPEs). The enzymatic activity of the immobilized enzymes was thus measured in amperometric mode at +200 mV vs Ag/AgCl using as substrate the acetylthiocholine and butyrylthiocholine, respectively, quantifying the enzymatic product thiocholine by means of PB-SPEs. The biosensor with butyrylcholinesterase immobilized using glutaraldehyde, bovine serum albumin and Nafion® has demonstrated a shelf life higher than 6 months at RT in dry condition and an operational stability up to 10 h. The biosensor was challenged with Sarin gas. The enzymatic measurements were carried out also measuring the rate of enzymatic activity in the first 30 s by means of a new version of Palm Sens® instrument software. In this way, the time of analysis was lower than 2 min. Keeping in mind that the IDLH (Immediately Dangerous to Life or Health) is 0.1 mg/m3, this biosensor with kinetic measurements supported by the Palm Sens® software allows to detect 0.1 mg/m3 in 90 s, demonstrating that is an useful analytical system for environmental security.