title: Evaluation of a fiber optic immunosensor for quantitating cocaine in coca leaf extracts.
abstract: A fiber optic evanescent fluoroimmunosensor was used to rapidly detect and quantitate coca alkaloids as cocaine equivalents in leaf extracts of five Erythroxylum species. A monoclonal antibody (mAb) made against benzoylecgonine (BE), a major metabolite of cocaine, was immobilized covalently on quartz fibers and used as the biological sensing element in the portable fluorometer. Benzoylecgonine-fluorescein (BE-FL) was used as the optical signal generator when it bound to the fiber. If present, cocaine competed for the mAb and interfered with the binding of BE-FL, thereby reducing the fluorescence transmitted by the fiber. Calibration curves were prepared by measuring (over 30 s) the rates of fluorescence increase in the absence, or presence of cocaine. Ethanol or acid extracts of dry coca leaves were assayed by this fiber optic biosensor, gas chromatography and a fluorescent polarization immune assay. Biosensor values of cocaine content of leaves from five Erythroxylum species were not significantly different from gas chromatography values, but had higher variance. The biosensor assay was rapid and did not require cleanup of the crude leaf extracts. Cocaine in acid extracts was reduced significantly after 4 weeks at 23 degrees C and after 3 weeks at 37 degrees C. Fibers (mAb-coated), stored at 37 degrees C in phosphate-buffered solution (0.02% NaN3), gave stable responses for 14 days.
authors.affiliation: Department of Pharmacology and Experimental Therapeutics, School of Medicine, University of Maryland at Baltimore 21201, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Toppozada
authors.forename: J
authors.initials: J
authors.lastname: Wright
authors.forename: A T
authors.initials: AT
authors.lastname: Eldefrawi
authors.forename: M E
authors.initials: ME
authors.lastname: Eldefrawi
authors.forename: E L
authors.initials: EL
authors.lastname: Johnson
authors.forename: S D
authors.initials: SD
authors.lastname: Emche
authors.forename: C S
authors.initials: CS
authors.lastname: Helling
mesh_terms: D015374:Biosensing Techniques; D002138:Calibration; D003041:Coca / Q000737:chemistry*; D003042:Cocaine / Q000032:analysis*; D005336:Fiber Optic Technology; D007118:Immunoassay; D055100:Optical Fibers; D010936:Plant Extracts / Q000032:analysis; D010946:Plants, Medicinal
chemical_list: D010936:Plant Extracts; D003042:Cocaine