A Fiber-Optic Cocaine Biosensor

✍ Scribed by P.J. Devine; N.A. Anis; J. Wright; S. Kim; A.T. Eldefrawi; M.E. Eldefrawi

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 763 KB
• Volume: 227
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.1995.1273

✦ Synopsis

A fiber-optic biosensor was developed for detection of cocaine, its metabolites, and other coca alkaloids, using a monoclonal antibody ( (\mathrm{mAb})) against a derivatized benzoylecgonine (BE). The mAb was immobilized noncovalently on quartz fibers and a flow fluorometer was used to detect changes in evanescent wave fluorescence. A fluorescein (FL) conjugate of BE bound to the (\mathrm{mAb}) specifically in a saturable manner and with high affinity (\left(K_{d}=7.6 \mathrm{~nm}\right)). Cocaine or other test compounds competed with FL-BE for binding to the mAb in a concentration-dependent manner, thereby reducing the initial rate or steady-state fluorescence. Addition of cocaine to the flow buffer after reaching steady-state fluorescence enhanced the dissociation of bound FL-BE, and cocaine removal allowed fiber regeneration for multiple measurements. The detection limits for cocaine, cocaethylene, norcocaine, and BE were (5,5,29), and (30 \mathrm{ng} / \mathrm{ml}), respectively, but for ecgonine it was (4600 \mathrm{ng} / \mathrm{ml}) and for methylecgonine it was (2000 \mathrm{ng} / \mathrm{ml}). Tropacocaine was detected at (10 \mathrm{ng} / \mathrm{ml}), but atropine was detected at 2900 (\mathrm{ng} / \mathrm{ml}). The biosensor discriminated by 833 -fold between cocaine and its stereoisomer pseudococaine. Structural features necessary for high-affinity recognition by this mAb are benzoate and (3 \beta) configuration, both of which are found in BE, cocaine, norcocaine, and cocaethylene. 1995 Academic Press, Inc.