Submitted to: Biosensors and Bioelectronics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/1996
Publication Date: N/A
Citation: Interpretive Summary: Rapid, simple quantitative analysis of cocaine is needed in the field to estimate potential drug yield in coca plants. Existing methods, however, require extensive extraction, cleanup, and sophisticated instrumentation. To achieve a satisfactory field method, new breakthroughs in immunoassay science were used to develop a reusable quartz fiber optic biosensor that is sensitive for cocaine in macerated coca leaves. The accuracy of cocaine content measured by the fiber optic method was comparable to that of gas chromatography, a standard laboratory method. This technique should be useful to researchers and drug regulatory officials for analyzing cocaine or other coca alkaloids in coca leaves, and may have forensic and clinical applicability to drug analyses of human body fluids.
Technical 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 absence, or in 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 stable for 4 weeks at 4 deg C and for 1 week at 37 deg C. Fibers (mAb-coated), stored at 37 deg in phosphate-buffered solution (0.02% NaN3), gave stable responses for 14 days.