A novel
ultrasensitive nanobody-based electrochemical immunoassay
was prepared for assessing human exposure to pyrethroid insecticides.
3-Phenoxybenzoic acid (3-PBA) is a common human urinary metabolite
for numerous pyrethroids, which broadly served as a biomarker for
following the human exposure to this pesticide group. The 3-PBA detection
was via a direct competition for binding to alkaline phosphatase-embedded
nanobodies between free 3-PBA and a 3-PBA-bovine serum albumin conjugate
covalently immobilized onto citric acid-decorated nylon nanofibers,
which were incorporated on a screen-printed electrode (SPE). Electrochemical
impedance spectroscopy (EIS) was utilized to support the advantage
of the employment of nanofibrous membranes and the success of the
immunosensor assembly. The coupling between the nanofiber and nanobody
technologies provided an ultrasensitive and selective immunosensor
for 3-PBA detection in the range of 0.8 to 1000 pg mL–1 with a detection limit of 0.64 pg mL–1. Moreover,
when the test for 3-PBA was applied to real samples, the established
immunosensor proved to be a viable alternative to the conventional
methods for 3-PBA detection in human urine even without sample cleanup.
It showed excellent properties and stability over time.
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