Nanoparticle-based immunochromatographic test strip with fluorescent detector for quantification of phosphorylated acetylcholinesterase: an exposure biomarker of organophosphorus agents.

A nanoparticle-based fluorescence immunochromatographic test strip (FITS) coupled with a hand-held detector for highly selective and sensitive detection of phosphorylated acetylcholinesterase (AChE), an exposure biomarker of organophosphate (OP) pesticides and nerve agents, is reported. In this approach, OP-AChE adducts were selectively captured by quantum dot-tagged anti-AChE antibodies (Qdot-anti-AChE) and zirconia nanoparticles (ZrO2 NPs). The sandwich-like immunoreactions were performed among the Qdot-anti-AChE, OP-AChE and ZrO2 NPs to form a Qdot-anti-AChE-OP-AChE-ZrO2 complex, which was detected by recording the fluorescence intensity of Qdots captured during the test line. Paraoxon was used as the model OP pesticide. Under optimal conditions, this portable FITS immunosensor demonstrates a highly linear absorption response over the range of 0.01 nM to 10 nM OP-AChE, with a detection limit of 4 pM, coupled with good reproducibility. Moreover, the FITS immunosensor has been validated with OP-AChE spiked human plasma samples. This is the first report on the development of ZrO2 NP-based FITS for the detection of the OP-AChE adduct. The FITS immunosensor provides a sensitive and low-cost sensing platform for on-site screening/evaluating OP pesticides and nerve agents poisoning.