Lowering the detection limit of the acetylcholinesterase biosensor using a nanoporous carbon matrix

Nanostructured carbon matrix has been used for the immobilization and stabilization of the enzyme Eel. AChE. The use of this activated carbon matrix is shown to provide both, significant enzyme stabilization, as well as the means for lowering the detection limit of the biosensor. The enzyme is immobilized by adsorption into the nanostructured conductive carbon, which also acts as the working electrode. The proposed biosensor showed very good stability under continuous operation conditions (L-50 > 60 days), allowing its further use in inhibition mode. Using this biosensor, the monitoring of the organophosphorus pesticide dichlorvos at picomolar levels (1000 times lower than other systems reported so far) was achieved. The linear range of detection in flow injection system was six orders of magnitude (10(-12) to 10(-6) M). It is suggested that the ability of activated carbon to selectively concentrate the pesticide, as well as the enzyme hyperactivity within the nanopores is the reason for the decrease in the detection limit of the biosensor. (C) 2004 Elsevier B.V. All rights reserved.