A Multi‐electrochemical Competitive Immunosensor for Sensitive Cocaine Determination in Biological Samples

Abstract

[a] 1Introduction Cocaine (COC) is ap owerfully addictive alkaloidp resent on the leaves of the coca plant (erythroxylum coca, erythroxylumn ovogranatense)a nd is one of the most worldwide used illicit drugs [1].I ti sastrong centraln ervous system stimulantt hat increases the levels of the neurotransmitter dopamine by blocking reuptakes at nerve synapses,t hereby prolonging its action.Following administration, COC is rapidly metabolized by enzymatic hydrolysis into two majorm etabolites benzoylecgonine( BZE) and ecgonine methyl-ester (EME) [2].C OC concentrations in plasma depend from the routes of intake, and maximum values vary in ar ange 50-2000 ng mL À1 ,i natime of about 30-120 min. or greater depending on the route [3].N evertheless,m etabolites may be identified up to 144 h. Metabolite:cocaine ratios increase after COC administration, and might prove useful for interpreting times of last use in pharmacological and pharmacokineticss tudies [4].C OC is eliminated unchanged in the urine in 1-9 %p ercentage,w ith ah igher proportion in acid urine [2,3].T he duration of unmetabolized cocaine in urine can be up to 6-8 hours,so that the pharmacologicald etection of COC also reports av ery recent COC use [3].T he initial screening cutoff levels of COC in serum and urine are usually considered 300 ng mL À1 for cocaine and its metabolites [2,3]. Fort he samei ndividual, COC concentration in saliva is approximately three-fold of that foundi np lasma and over five-fold in urine.I na ddition, COC elimination halflife is lower in saliva than in urine or blood, which makes oral fluid analysis suitable for determination of very recent use providing unequivocal screen results within minutes [4].T he cutoff level on saliva drug tests for cocaine is normally 20 ng mLTheb iological detection of drugu se involvesascreening test, which if positive,i sf ollowed by ac onfirmatory test. Screeninga nalysis of COC in av ariety of samples (e.g. urine,b lood,p lasma, hair, saliva, sweat, meconium, cocaine powder or waste water) use commonly enzyme immunoassays (EIA), e.g. ELISA (enzyme-linked immunosorbent analysis) [5][6][7],w hile liquid chromatography-(tandem) masss pectrometry( LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) are the usual methods of choice for confirmation of presumptive positive results from the initial screeninga nalysis [8].T ypically,C OC is extracted in an organic solventf or chromatographic analysis,f ollowed by af orm of sample clean-up (e.g. centrifugation or filtration), preconcentration, and purification of the extractedt arget due to matrix effects [8].G C-MS also require complicated chemical derivatization procedures of the COC molecules [5,8].S uch timeexpensives amplep retreatment procedures can be avoided with immunochemical analysis simply by diluting the biological sample in an aqueous buffer beforethe analysis [5].T he reported limits of detection (LODs) of the GC-MS and LC-MS/MS methods are in the range1 .2 to Abstract:Am ulti-electrochemical competitive immunosensor for the rapi...

A rapid magnetic particle-based enzyme immunoassay for human cytomegalovirus glycoprotein B quantification

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Magnetic Particles Coupled to Disposable Screen Printed Transducers for Electrochemical Biosensing

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