the most commonly used toxic substance in pesticides, can lead to cholinergic dysfunction, which affects the health of both humans and animals. Rapid, sensitive and cost-effective detection of OP neurotoxins is important for protecting water resources and food supplies, in the defense against terrorist activity, and for monitoring detoxification processes. Traditional laboratory-based analytical techniques for detecting OPs include chromatography and mass spectrometry which are rather time-consuming and expensive (Sherma, 1993). Enzyme-based biosensors using carbon nanotubes as the transducer have been used for highly selective and rapid detection of pesticides. These enzymatic biosensors can either be used for direct detection based on the catalytic activity of organophosphorus hydrolase (OPH) (Mulchandani et al., 2001) or based on the inhibition of activity of several enzymes present in pesticides like acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and tyrosinase (Tyr) (Andreescu and Marty, 2006 and Tanimoto de Albuquerque and Ferreira, 2007).