Tailor-Made Immunochromatographic Test for the Detection of Multiple 17α-Methylated Anabolics in Dietary Supplements

In recent years, the undeclared presence of various anabolic androgenic steroids (AAS) in commercial supplements has been confirmed. This fact can be a potential threat to all athletes using these supplements, and therefore, there is of increased interest in the implementation of rapid methods for the detection of AAS. The presented study describes the development of an immunostrip test for the detection of multiple 17α-methylated AAS based on direct and indirect competitive principle using gold nanoparticles as a label. As a capture reagent on test lines conjugated stanazolol to rabbit serum albumin (RSA/ST-3) was used, the intensity of color formed in the test line of the AAS-positive sample was visually distinguishable from that of negative sample within 10 min. The optimized closed direct and indirect format of the test provided a similar visual detection limit (0.7 and 0.9 ng/mL, respectively). The most commonly orally abused AAS (17α-methyltestosterone, methandienone, methyldihydrotestosterone, oxandrolone and oxymetholone) showed a strong cross-reaction. Developed immunostrips were successfully applied to analysis of artificially contaminated dietary supplements with 17α-methylated AASs. The developed immunostrips offer potential as a useful user-friendly method for capturing suspicious dietary supplement samples with different contents of AAS at levels far below the usually used concentrations of AAS

Development of a rapid, simple paddle-style dipstick dye immunoassay specific for Listeria monocytogenes

We have developed two types of new paddle-style dipstick dye immunoassays. The first is genus Listeria specific and the second is specific to Listeria monocytogenes. They are based respectively, on antisera raised against heat-killed L. monocytogenes cells and against internalin B crude extract, a virulence protein found only in the pathogenic L. monocytogenes. The minimum detectable level for L. monocytogenes is 2x10(7) CFU ml(-1) for strain number 88/049 in pure culture. Detection is unaffected by the presence of high numbers (approximately log 8.0 CFU/ml) of the other microorganisms tested. When the dipsticks were applied to milk samples inoculated with L. monocytogenes reference material (ALM92), there was a strong response to the enrichment cultures. The new assay may prove useful in detection of L. monocytogenes in enrichment cultures of milk and ice cream food samples

Sensitive enzyme immunoassay for screening methandienone in dietary supplements

<p>Methandienone is a synthetic exogenous steroid which, like other anabolic steroids, is strictly regulated in many countries. In recent years, increasing numbers have been detected of illegal additions into dietary supplements of methandienone and other anabolic androgenic steroids (AAS). In this work, a competitive indirect enzyme-linked immunosorbent assay (ELISA) has been constructed for the detection of methandienone using an antiserum against methandienone. Under optimal experimental conditions, the ELISA achieved a limit of detection of 0.04 ± 0.01 µg.g⁻¹. The obtained intra- and inter-day coefficients of variation were less than 8%. The developed ELISA was applied in the analysis of real dietary supplement samples. To minimise the effect of the sample matrix, the sample extracts were simply diluted before addition into the immunoassay. The achieved recovery values were around 100%. Results obtained from the ELISA correlated well, both in terms of accuracy and precision, with those obtained by UHPLC-MS/MS (reference method). The presented ELISA could be successfully applied for the simple screening of dietary supplements.</p