Optimization of sol-gel based fibre-optic cholinesterase biosensor for thedetermination of organophosphorus pesticides

A sol-gel based fiber-optic biosensor with acetylcholinasterase as the bior ecognition element has been developed for the rapid determination of organo phosphorus pesticides. Nine fluorescent indicators, acridine, acridine oran ge, neutral red, DAPI, rhodamine B, fluorescein, umbelliferone, FITC on cel ite and FITC-dextran, have been examined to optimize the fiber-optic system . Results showed that acridine and FITCs ware sensitive to the change of pH value caused by the enzyme-substrate catalysis reaction. However, the sens itivity of acridine was 260 times lower than that of FITCs. Higher toxicity of acridine to acetylcholinesterase than FITC was also observed. Moreover, the high-molecular-weight FITC-dextran showed low leakage rate when immobi lizing using sol-gel technology, showing that the FITC-dextran was a suitab le pH sensitive fluorescent indicator for the OPPs biosensor. The response of the fiber-optic biosensor to the substrate, acetylcholine, was highly re producible (RSD=3.5%). A good linearity of acetylcholina in the range from 0.5 to 20 mM was also obtained (R-2=0.98). Furthermore, a 30% inhibition ca n be achieved in 30min when 152 ppb paraoxon was added into the system. The results show the possibility for real-time determination of organophosphor us pesticides by using the biosensor developed in this study.