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Optical detection of paraoxon using single-walled carbon nanotube films with attached organophosphorus hydrolase-expressed Escherichia coli.

Kim I, Kim GH, Kim CS, Cha HJ, Lim G - Sensors (Basel) (2015)

Bottom Line: A device with circular electrodes was fabricated for an enlarged cell-immobilization area.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.

View Article: PubMed Central - PubMed

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.

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.

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Related in: MedlinePlus

Device Imaging. Optical image of (a) the entire device (scale bar: 2 mm) and (b) a magnified view of the circular comb drive-shaped electrodes (scale bar: 50 µm). (c) SEM image of E. coli-attached SWNT film (scale bar: 5 µm). The red square in (a) indicates the image area of (b), and the red square in (b) indicates the image area of (c).
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sensors-15-12513-f003: Device Imaging. Optical image of (a) the entire device (scale bar: 2 mm) and (b) a magnified view of the circular comb drive-shaped electrodes (scale bar: 50 µm). (c) SEM image of E. coli-attached SWNT film (scale bar: 5 µm). The red square in (a) indicates the image area of (b), and the red square in (b) indicates the image area of (c).

Mentions: To fabricate an E. coli-attached SWNT film on the device, an AC voltage with an amplitude of 7 VPP and a frequency of 1 MHz was applied between the two electrodes, across the mixed SWNT/E. coli suspension, for 10 s. This process was repeated in sequence from the innermost electrodes to the outermost electrodes to fabricate E. coli-attached SWNT film in every gap between the electrodes. Figure 3c shows a scanning electron microscopy (SEM) image of E. coli-attached SWNT film. Two cantilever electrodes are connected with SWNTs, and cells are attached to the SWNTs. Because the SWNTs are a one-dimensional structure, the attachment area of cells is minimized, while the reaction area of cells is maximized. In addition, E. coli-attached SWNT film is floated from the bottom of the substrate and contains spaces between cells that can pass substances. Therefore, mass transfer of the floated film is enhanced compared to the film attached to the floor of the substrate.


Optical detection of paraoxon using single-walled carbon nanotube films with attached organophosphorus hydrolase-expressed Escherichia coli.

Kim I, Kim GH, Kim CS, Cha HJ, Lim G - Sensors (Basel) (2015)

Device Imaging. Optical image of (a) the entire device (scale bar: 2 mm) and (b) a magnified view of the circular comb drive-shaped electrodes (scale bar: 50 µm). (c) SEM image of E. coli-attached SWNT film (scale bar: 5 µm). The red square in (a) indicates the image area of (b), and the red square in (b) indicates the image area of (c).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507580&req=5

sensors-15-12513-f003: Device Imaging. Optical image of (a) the entire device (scale bar: 2 mm) and (b) a magnified view of the circular comb drive-shaped electrodes (scale bar: 50 µm). (c) SEM image of E. coli-attached SWNT film (scale bar: 5 µm). The red square in (a) indicates the image area of (b), and the red square in (b) indicates the image area of (c).
Mentions: To fabricate an E. coli-attached SWNT film on the device, an AC voltage with an amplitude of 7 VPP and a frequency of 1 MHz was applied between the two electrodes, across the mixed SWNT/E. coli suspension, for 10 s. This process was repeated in sequence from the innermost electrodes to the outermost electrodes to fabricate E. coli-attached SWNT film in every gap between the electrodes. Figure 3c shows a scanning electron microscopy (SEM) image of E. coli-attached SWNT film. Two cantilever electrodes are connected with SWNTs, and cells are attached to the SWNTs. Because the SWNTs are a one-dimensional structure, the attachment area of cells is minimized, while the reaction area of cells is maximized. In addition, E. coli-attached SWNT film is floated from the bottom of the substrate and contains spaces between cells that can pass substances. Therefore, mass transfer of the floated film is enhanced compared to the film attached to the floor of the substrate.

Bottom Line: A device with circular electrodes was fabricated for an enlarged cell-immobilization area.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.

View Article: PubMed Central - PubMed

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.

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.

Show MeSH
Related in: MedlinePlus