Amperometric method for rapid detection of Escherichia coli by flow injection analysis using a bismuth nano-film modified glassy carbon electrode

A new method for rapid detection of Escherichia coli (E. coli) was developed by flow injection analysis (FIA) using bismuth nanofilm modified glassy carbon electrode (BiNFE) in this paper. The method depended on a good marker P-D-glucuronidase which is found in E. coli strains. P-D-Glucuronidase was produced by the induction of methyl-beta-D-glucuronide sodium (MetGlu), then released from E. coli cells through the permeabilization of cell membrane caused by polymyxin B nonapeptide and lysozyme. The released beta-D-glucuronidase could catalyze the hydrolysis of the substrate 4-nitrophenyl beta-D-glueuronide (PNPG) in the culture medium to produce 4-nitrophenol. Since 4-nitrophenol is electroactive and its quantity is proportional to the concentration of E. coli, E. coli could be determined by electroanalysis of 4-nitrophenol. The BiNFE was fabricated by an electrodeposition of metallic bismuth onto a glassy carbon electrode, which showed a high sensitivity in determination of 4-nitrophenol when used in conjunction with FIA system. Experimental results showed that the amplified response current of 4-nitrophenol obtained at the BiNFE was linear with the concentration of E. coli ranging from 1.5 x 10(2) to 1.0 X 10(6) cfu/ml, the detection limit of this method for E. coli is 100 cfu/ml, and the complete assay was performed in 3 h. (c) 2006 Elsevier B.V. All rights reserved.