Nanobody@Biomimetic mineralized MOF as a sensing immunoprobe in detection of aflatoxin B.

Nanobody(Nb) is too small to carry more signal reporters, which often leads to low sensitivity in immunoassay. Herein, we proposed a novel immunoprobe integration of Nb and biomimetic mineralized metal-organic frameworks(MOF), in which plenty of succinylated horseradish peroxidase(sHRP) were encapsulated within a single MOF and the Nb was assembled on the biomimetic mineralized MOF. It overcomes the dilemma that the Nb is difficult to carry more signal reporters. Meanwhile, the mineralized MOF can protect the sHRP from denaturation and facilitate the transport of substrates to the active sites of sHRP. Electrosensing of aflatoxin B(AFB) was realized with a competitive format in which the target AFB and immobilized artificial antigen were competing for binding with the immunoprobe. Additionally, the detection signal was enlarged by the catalysis of this immunoprobe to 4-chloro-1-naphthol for producing precipitations, which blocked the channels of the immunoprobe and the redox probes of Fe(CN) was difficult to reach the electrode surface through the channels. Hence, the as-prepared immunosensor exhibited good voltammetry responses towards the determined AFB in a linear range of 50.0 fg/mL - 20.0 ng/mL with a detection limit of 20.0 fg/mL. The specificity, stability, and reproducibility of this immunosensor were satisfactory. This work may provide an alternative idea for the application of Nb in immunoassay, and the idea may also be applicable to other bio-recognition elements for immunoassay.