Nanobody-Based Electrochemical Immunoassay for Sensitive Detection of Peanut Allergen Ara h 1

Peanut is widely used for food supplementation with potential allergic reactions in infants and adults, which prompted the development of reliable and accurate detection of peanut allergens with emphasis on Ara h 1. In this study, a nanobody (Nb)-based micro-total electrochemical immunoassay (Nb-μTEI) was proposed to be generated. Generally, an alpaca was immunized with Ara h 1 to yield a Nb reservoir for selection of four specific Nbs. Nb-mediated immunocapturing allowed the identification of the target as Ara h 1. The Nb-based electrochemical immunoassay was developed by constructing a capturing electrode with cycles of signal enhancement. After construction of the capturing electrode, Nb152 with HA-tag was directly applied to connect immobilized anti-HA IgG for the capture of different concentrations of Ara h 1, which was labeled by biotinylated Nb152 to facilitate signal development with alkaline phosphatase conjugated streptavidin (SA-ALP). A linear range from 4.5 to 55 ng/mL was acquired with LOD and LOQ of 0.86 and 2.10 ng/mL, respectively, with an 11-fold increase of the sensitivity compared with the established sandwich ELISA. The dedicated immunoassay was verified by detecting the antigen spiked in food samples and demonstrated the successful conjugation of Nb with advanced detecting techniques.