Development of a monoclonal antibody-based enzyme-linked immunosorbent assay for the analysis of 6-benzylaminopurine and its ribose adduct in bean sprouts.

6-Benzylaminopurine (6-BA), a cytokinin plant growth regulator, has been banned for use in bean sprout production in China. An indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed with a specific monoclonal antibody (mAb 3E5). The assay showed a half-maximum inhibition concentration (IC 50 ) and detection range of 18.9 ng/mL and 3.6–106 ng/mL, respectively. Recoveries of 6-BA spiked in home cultured bean sprout samples averaged from 75% to 89% with a correlation coefficient (R 2 ) of 0.998 between the results determined by icELISA and those by liquid chromatography–electrospray ionization quadrupole Orbitrap mass spectrometry (LC–ESI-MS). LC–ESI-MS showed that 6-BA had been partially metabolized to 6-benzylaminopurine riboside (6-BAR) in the positive samples. The content of 6-BA determined by icELISA was about 5–70 times higher than that of LC–ESI-MS because mAb 3E5 had 315% cross-reactivity with 6-BAR. Such icELISA being ultra-sensitive to 6-BAR would allow quick monitoring of 6-BA by detecting 6-BAR as a potential biomarker. [ABSTRACT FROM AUTHOR]