title: An organophosphorus hydrolase-based biosensor for direct detection of paraoxon using silica-coated magnetic nanoparticles.
abstract: Rapid detection of organophosphorous (OP) compounds such as paraoxon would allow taking immediate decision on efficient decontamination procedures and could prevent further damage and potential casualties. In the present study, a biosensor based on nanomagnet-silica core-shell conjugated to organophosphorous hydrolase (OPH) enzyme was designed for detection of paraoxon. Coumarin1, a competitive inhibitor of the OPH enzyme, was used as a fluorescence-generating molecule. Upon excitation of cumarin1 located at the active site of the enzyme, i.e., OPH, the emitted radiations were intensified due to the mirroring effect of the nanomagnet-silica core-shell conjugated to the enzyme. In presence of paraoxon and consequent competition with the fluorophore in occupying enzyme's active site, a significant reduction in emitted radiations was observed. This reduction was proportional to paraoxon concentration in the sample. The method worked in the 10- to 250-nM concentration range had a low standard deviation (with a coefficient of variation (CV) of 6-10%), and the detection limit was as low as 5 × 10(-6) μM.
authors.affiliation: Department of Toxicology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Khaksarinejad
authors.forename: Afshin
authors.initials: A
authors.lastname: Mohsenifar
authors.forename: Tavoos
authors.initials: T
authors.lastname: Rahmani-Cherati
authors.forename: Rezvan
authors.initials: R
authors.lastname: Karami
authors.forename: Meisam
authors.initials: M
authors.lastname: Tabatabaei
mesh_terms: D043303:Aryldialkylphosphatase / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods*; D003374:Coumarins / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010261:Paraoxon / Q000032:analysis*; D011549:Pseudomonas / Q000201:enzymology*; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D003374:Coumarins; D058185:Magnetite Nanoparticles; D012822:Silicon Dioxide; C030123:coumarin; D043303:Aryldialkylphosphatase; D010261:Paraoxon