Mulchandani A, Mulchandani P, Kaneva I, Chen W
Department of Chemical and Environmental Engineering, University of California, Riverside 92521, USA.
Anal Chem. 1998 Oct 1;70(19):4140-5. doi: 10.1021/ac9805201.
A potentiometric microbial biosensor for the direct measurement of organophosphate (OP) nerve agents was developed by modifying a pH electrode with an immobilized layer of Escherichia coli cells expressing organophosphorus hydrolase (OPH) on the cell surface. OPH catalyzes the hydrolysis of organophosporus pesticides to release protons, the concentration of which is proportional to the amount of hydrolyzed substrate. The sensor signal and response time were optimized with respect to the buffer pH, ionic concentration of buffer, temperature, and weight of cells immobilized using paraoxon as substrate. The best sensitivity and response time were obtained using a sensor constructed with 2.5 mg of cells and operating in pH 8.5, 1 mM HEPES buffer. Using these conditions, the biosensor was used to measure as low as 2 microM of paraoxon, methyl parathion, and diazinon. The biosensor had very good storage and multiple use stability. The use of cells with the metabolic enzyme expressed on cell surface as a biological transducer provides advantages of no resistances to mass transport of the analyte and product across the cell membrane and low cost due to elimination of enzyme purification, over the conventional microbial biosensors based on cells expressing enzyme intracellularly and enzyme-based sensors, respectively.
通过用在细胞表面表达有机磷水解酶（OPH）的大肠杆菌细胞固定层修饰pH电极，开发了一种用于直接测量有机磷（OP）神经毒剂的电位型微生物生物传感器。OPH催化有机磷农药水解以释放质子，质子浓度与水解底物的量成正比。以对氧磷为底物，针对缓冲液pH、缓冲液离子浓度、温度和固定化细胞重量对传感器信号和响应时间进行了优化。使用由2.5 mg细胞构建并在pH 8.5、1 mM HEPES缓冲液中运行的传感器获得了最佳灵敏度和响应时间。在这些条件下，该生物传感器用于测量低至2 microM的对氧磷、甲基对硫磷和二嗪农。该生物传感器具有非常好的储存稳定性和多次使用稳定性。与分别基于细胞内表达酶的传统微生物生物传感器和基于酶的传感器相比，使用在细胞表面表达代谢酶的细胞作为生物换能器具有分析物和产物跨细胞膜传质无阻力以及由于无需酶纯化而成本低的优点。
