title: Optical detection of paraoxon using single-walled carbon nanotube films with attached organophosphorus hydrolase-expressed Escherichia coli.
abstract: In whole-cell based biosensors, spectrophotometry is one of the most commonly used methods for detecting organophosphates due to its simplicity and reliability. The sensor performance is directly affected by the cell immobilization method because it determines the amount of cells, the mass transfer rate, and the stability. In this study, we demonstrated that our previously-reported microbe immobilization method, a microbe-attached single-walled carbon nanotube film, can be applied to whole-cell-based organophosphate sensors. This method has many advantages over other whole-cell organophosphate sensors, including high specific activity, quick cell immobilization, and excellent stability. A device with circular electrodes was fabricated for an enlarged cell-immobilization area. Escherichia coli expressing organophosphorus hydrolase in the periplasmic space and single-walled carbon nanotubes were attached to the device by our method. Paraoxon was hydrolyzed using this device, and detected by measuring the concentration of the enzymatic reaction product, p-nitrophenol. The specific activity of our device was calculated, and was shown to be over 2.5 times that reported previously for other whole-cell organophosphate sensors. Thus, this method for generation of whole-cell-based OP biosensors might be optimal, as it overcomes many of the caveats that prevent the widespread use of other such devices.
authors.affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 790-784, Korea. one@postech.ac.kr.
authors.forename: Intae
authors.initials: I
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 790-784, Korea. q16164545@postech.ac.kr.
authors.forename: Geon Hwee
authors.initials: GH
authors.lastname: Kim
authors.affiliation: School of Biotechnology and Graduate School of Biochemistry, Yeungnam Univerisity, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 712-749, Korea. cskim1409@ynu.ac.kr.
authors.forename: Chang Sup
authors.initials: CS
authors.lastname: Kim
authors.affiliation: Department of Chemical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 790-784, Korea. hjcha@postech.ac.kr.
authors.forename: Hyung Joon
authors.initials: HJ
authors.lastname: Cha
authors.affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology, 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk 790-784, Korea. limmems@postech.ac.kr.
authors.forename: Geunbae
authors.initials: G
authors.lastname: Lim
mesh_terms: D043303:Aryldialkylphosphatase / Q000737:chemistry / Q000378:metabolism*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D018914:Cells, Immobilized / Q000737:chemistry / Q000201:enzymology*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010261:Paraoxon / Q000032:analysis* / Q000378:metabolism
chemical_list: D037742:Nanotubes, Carbon; D043303:Aryldialkylphosphatase; D010261:Paraoxon
keywords: biosensor; carbon nanotube; microbial immobilization; organophosphates