Optical organophosphorus biosensor consisting of acetyleholinesterase/viologen hetero Langmuir- Blodgett film

The fiber-optic biosensor consisting of an acetyleholinesterase (AChE)-immo bilized Langmuir-Blodegtt (LB) film was developed to detect organophosphoru s compounds in contaminated water. The sensing scheme was based on the decr ease of yellow product, o-nitrophenol, from a colorless substrate, o-nitrop henyl acetate, due to the inhibition by organophosphorus compounds on AChE. Absorbance change of the product as the output of enzyme reaction was dete cted and the light was guided through the optical fibers. The enzyme portio n of the sensor system was fabricated by the LB technique for formation of the enzyme film. AChE-immobilized LB film was formed by adsorbing the enzym e molecules onto a viologen monolayer using the electrostatic force. The pr oposed kinetics for irreversible inhibition of organophosphorus compounds o n AChE agreed well with the experimental data. The surface topography of AC hE-immobilized LB film was investigated by atomic force microscope (AFM). T he immobilized AChE had the maximum activity at pH 7. The proposed biosenso r could successfully detect the organophosphorus compounds upto 2 ppm and t he response time to steady signal of the sensor was about 10 min. (C) 2001 Elsevier Science B.V. All rights reserved.