A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS-decorated graphene nanocomposite.
ABSTRACT This work reports a rapid and sensitive organophosphates (OPs) amperometric biosensor based on acetylcholinesterase (AChE) immobilized on CdS-decorated graphene (CdS-G) nanocomposite. The as-prepared biosensor shows high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.24 mM. A rapid inhibition time (2 min) is obtained due to the integration of the CdS-G nanocomposite. Based on the inhibition of OPs on the enzymatic activity of the immobilized AChE, and used carbaryl as the model compound, the resulting biosensor exhibits excellent performance for OPs detection including good reproducibility, acceptable stability, and a reliable linear relationship between the inhibition and log[carbaryl] from 2 ng mL⁻¹ up to 2 μg mL⁻¹ with a detection limit of 0.7 ng mL⁻¹,which provides a new promising tool for analysis of enzyme inhibitors.
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ABSTRACT: 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.Analytical Chemistry 11/1998; 70(19):4140-5. · 5.70 Impact Factor
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ABSTRACT: Based on their size and unique electrical properties, carbon nanotubes offer the exciting possibility of developing ultrasensitive, electrochemical biosensors. In this study, we describe the construction of amperometric biosensors based on the incorporation of single-walled carbon nanotubes modified with enzyme into redox polymer hydrogels. The composite films were constructed by first incubating an enzyme in a single-walled carbon nanotube (SWNTs) solution and then cross-linking within a poly[(vinylpyridine)Os(bipyridyl)(2)Cl(2+/3+)] polymer film. Incorporation of SWNTs, modified with glucose oxidase, into the redox polymer films resulted in a 2-10-fold increase in the oxidation and reduction peak currents during cyclic voltammetry, while the glucose electrooxidation current was increased 3-fold to approximately 1 mA/cm(2) for glucose sensors. Similar effects were also observed when SWNTs were modified with horseradish peroxidase prior to incorporation into redox hydrogels.Analytical Chemistry 06/2005; 77(10):3183-8. · 5.70 Impact Factor