Detection of methamphetamine group drugs
The present invention provides immunoassays which are highly specific for detection in biological samples of methamphetamine and other drugs of abuse of the methamphetamine group such as ecstasy and other ecstasy class drugs. More particularly, competitive assays are provided comprising: (a) contacting said sample with (i) a pseudoephedrine/carrier conjugate in which pseudoephedrine is linked via its hydroxyl group to the carrier and (ii) an antibody which is capable of binding both one or more drugs of the methamphetamine group and said conjugate; and (b) determining whether the binding of said antibody to said conjugate is reduced by the presence of said sample, a reduction in binding being indicative that the sample contains a methamphetamine group drug.
1. A method for detecting whether a liquid sample contains one or more drugs of the methamphetamine group comprising:
(a) contacting said sample with (i) a pseudoephedrine/carrier conjugate in which pseudoephedrine is linked via its hydroxyl group to the carrier and (ii) an antibody which is capable of binding both one or more drugs of the methamphetamine group and said conjugate; and
(b) determining whether the binding of said antibody to said conjugate is reduced by the presence of said sample, a reduction in binding being indicative that the sample contains a methamphetamine group drug.
2. The method according to claim 1 wherein said antibody is capable of specifically binding to the group of drugs consisting of methamphetamine, ecstasy (3,4-methylenedioxymethamphetamine, MDMA), (+/−)-N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB) and (+/−)-3,4-methylenedioxyethylamphetamine (MDEA).
3. The method as claimed in claim 2 wherein at least methamphetamine, ecstasy (3,4-methylenedioxymethamphetamine, MDMA) and (+/−)-N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB) are capable of detection at at least 15 ng/ml.
4. The method according to claim 1 wherein said antibody has less than 0.4% cross-reactivity with all of (+)-ephedrine, (−)-ephedrine, (+)-pseudoephedrine, (−)-pseudoephedrine, phenylpropanolamine, phentermine, tyramine, amphetamine, beta-phenylethylamine and MDA at a concentration of 10,000 ng/ml.
5. The method as claimed in claim 4 wherein said antibody has less than 0.1% cross-reactivity with all of (+)-ephedrine, (−)-ephedrine, (+)-pseudoephedrine, (−)-pseudoephedrine, phenylpropanolamine, phentermine and tyramine at a concentration of 10,000 ng/ml.
6. The method according to claim 1 wherein said carrier is a protein.
7. The method according to claim 6 wherein said protein is selected from bovine serum albumin, horseradish peroxidase, ovalbumin, a gamma globulin and thyroglobulin.
8. The method according to claim 1 wherein said carrier is a homo- or hetero-amino acid polymer.
9. The method according to claim 1 wherein said antibody is labeled directly or indirectly.
10. The method according to claim 1 wherein said pseudoephedrine conjugate is labeled directly or indirectly or the carrier of said conjugate also serves as a detectable label.
11. The method according to claim 1 wherein said conjugate is a conjugate obtained by coupling pseuodephedrine via its hydroxyl group to said carrier using dimethyl aminopyridine/disuccinimidyl carbonate, formaldehyde or vinyl sulfone.
12. The method according to claim 1 wherein the pseudoephedrine is coupled to said carrier via a spacer molecule.
13. The method according to claim 1 wherein one of said antibody and said pseudoephedrine/carrier conjugate is immobilised on a solid support.
14. The method according to claim 13 wherein the pseudoephedrine/carrier conjugate is immobilized on a solid support and said antibody is labeled with a detectable label.
15. The method as claimed in claim 13 which is conducted using a lateral flow immunochromatography assay device.
16. The method as claimed in claim 1 wherein said sample consists of, or is derived from, urine, blood, sweat, oral fluid or hair.
17. The method as claimed in claim 1 wherein said sample is a sample obtained by dissolving a powder to be tested in a buffer solution.
18. A test strip or sheet for use in a lateral flow analytical device for carrying out a lateral flow immunochromatography assay according to claim 15 , said test strip or sheet comprising:
(i) a strip or sheet comprising a dry porous material having immobilised thereon in an analyte detection zone said pseudoephedrine/carrier conjugate or said antibody and
(ii) joined to, or integral to, said strip or sheet providing said analyte detection zone a separate label release zone which is capable of releasing into liquid drawn into the zone either said antibody in labeled form, if said analyte detection zone presents immobilised pseudoephedrine conjugate, or, if said analyte detection zone presents immobilised antibody, detectable pseudoephedrine conjugate, wherein the pseudoephedrine conjugate is labeled directly or indirectly or the carrier of said conjugate also serves as a detectable label.
19. The test strip or sheet according to claim 18 wherein said dry porous material is nitrocellulose.
20. The test strip or sheet according to claim 18 wherein pseudoephedrine/carrier conjugate is immobilised in an analyte detection zone.
21. The test strip or sheet according to claim 18 which further comprises a control zone which is located distal to said analyte detection zone in the direction of intended liquid flow, wherein said control zone comprises an immobilized reagent that binds to either labeled antibody or detectable pseudoephedrine conjugate.
22. The test strip or sheet according to claim 18 which further comprises a sample receiving member or pad proximal to said label release zone having regard to the intended direction of liquid flow.
23. The test strip or sheet as claimed in claim 18 , wherein said test strip or sheet is disposed in a housing.
24. The test strip or sheet according to claim 18 , wherein said test strip or sheet is disposed in a lateral flow device.
25. A kit for carrying out a method according to claim 1 which comprises said pseudoephedrine/carrier conjugate and said antibody.
26. The kit as claimed in claim 25 wherein said antibody is directly labeled or secondary labeled antibody is provided for labeling of said antibody.
27. The kit as claimed in claim 25 wherein said conjugate is a detectable conjugate.
28. The kit as claimed in claim 25 wherein said antibody or said conjugate is immobilised on a solid support.
29. The kit as claimed in claim 28 which comprises a test strip or sheet, wherein said test strip or sheet comprises:
(i) a strip or sheet comprising a dry porous material having immobilised thereon in an analyte detection zone said pseudoephedrine/carrier conjugate or said antibody and
(ii) joined to, or integral to, said strip or sheet providing said analyte detection zone a separate label release zone which is capable of releasing into liquid drawn into the zone either said antibody in labeled form, if said analyte detection zone presents immobilised pseudoephedrine conjugate, or, if said analyte detection zone presents immobilised antibody, detectable pseudoephedrine conjugate, wherein the pseudoephedrine conjugate is labeled directly or indirectly or the carrier of said conjugate also serves as a detectable label.
30. The test strip or sheet according to claim 18 which further comprises an absorbent waste pad distal to said analyte detection zone in the direction of intended liquid flow.