A new changeable bioreactor for detection of organophosphate in a flow-through system

A flow-through biosensor consisting of a fixed bed bioreactor was employed to detect the insecticide paraoxon. Based on the inhibition of organophosphorous insecticide to the enzymatic activity of acetylcholinesterase (AChE), using paraoxon as a model compound, the condition for detection of the insecticide were optimized. The influence of enzyme loading on the packing surface was studied and AChE loading was set at 0.36 U/cm2 for subsequent studies. Maximum value of absorbance response occurred at the residence time in bioreactor of 5 min, that was chosen as the optimal residence time. This flow-through system gave a linear response (R2 = 0.9869) to acetylthiocholine iodide (ATChI) at concentrations of 0.050 to 1 mM. Under appropriate conditions, the inhibition of paraoxon was proportional to its concentration in two ranges, from 0.25 to 25 mg/l and 25 to 60 mg/l and the detection limit for paraoxon was 7.3×10-8 M. The incubation time was 14 min. These results demonstrate that silicate-multiwall carbon nanotube (MWCNT) sol film is very efficient for retaining the activity of AChE with a good long-term stability.