A Rapid Reusable Fiber Optic Biosensor for Detecting Cocaine Metabolites in Urine

Published: Journal of Analytical Toxicology, Volume 23, Number 6, October 1999, pp.460-467

A Rapid Reusable Fiber Optic Biosensor for Detecting Cocaine Metabolites in Urine
Nidhi Nath, Mohyee Eldefrawi, Jeremy Wright, David Darwin and Marilyn Huestis

Analyte 2000, a four-channel fiber optic biosensor (FOB), was used for analysis of cocaine and its metabolites (COC) in human urine using a competitive fluorescence immunoassay. Binding of antibenzoylecgonine monoclonal antibody (mAb) to the casein-benzoylecgonine Ag-coated, tapered optical fibers was inhibited by COC. Bound mAb, which inversely correlated with COC concentration, was quantitated by fluorescence produced by evanescent excitation of bound cyanine dye-tagged antimouse antibody (CY5-Ab). The effective concentration range of benzoylecgonine (BE) for inhibiting the fluorescent signals was 0.75–50 ng/mL, with IC50 of 9.0 ng/mL. This FOB had similar affinities for BE, cocaine, and cocaethylene, but very low affinities for ecgonine and ecgonine methyl ester. A sensitivity of 100% and a specificity of 96% were achieved when 54 human urine specimens were analyzed by FOB (cutoff, 300 ng/mL COC) and GC–MS (cutoff, 150 ng/mL BE). All results were in agreement except for one positive FOB result with a GC–MS BE concentration of 148 ng/mL. In addition, regeneration and reuse of the fiber for multiple analyses were performed successfully with no carryover from specimens containing high COC concentrations to specimens containing low COC concentrations.

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