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Analytica chimica acta

Novel quartz crystal microbalance immunodetection of aflatoxin B1 coupling cargo-encapsulated liposome with indicator-triggered displacement assay.


PMID 30119735

Abstract

A simple and sensitive quartz crystal microbalance (QCM) immunosensing platform was designed for the high-efficient detection of aflatoxin B1 (AFB1) in foodstuff. Initially, phenoxy-derived dextran molecule was immobilized on the surface of QCM gold substrate by using thiolated β-cyclodextrin based on the supramolecular host-guest chemistry between phenoxy group and cyclodextrin. Then, AFB1-bovine serum albumin (AFB1-BSA)-conjugated concanavalin A (Con A) was assembled onto the QCM probe through the dextran-Con A interaction. Glucose-loaded nanoliposome, labeled with monocolonal anti-AFB1 antibody, was used for the amplification of QCM signal. Upon target AFB1 introduction, the analyte competed with the immobilized AFB1-BSA on the probe for the labeled anti-AFB1 antibody on the nanoliposome. Based on specific antigen-antibody reaction, the amount of the conjugated nanoliposomes on the QCM probe gradually decreased with the increment of target AFB1 in the sample. Upon injection of Triton X-100 in the detection cell, the carried nanoliposome was lysed to release the encapsulated glucose molecules. Thanks to the stronger affinity of Con A toward glucose than that of dextran, AFB1-BSA-labeled Con A was displaced from the QCM probe, resulting in the change of the local frequency. Under the optimum conditions, the shift of the functionalized QCM immunosensing interface in the frequency shift was proportional to the concentration of target AFB1 within a dynamic range from 1.0 ng kg-1 to 10 μg kg-1 at a low detection limit of 0.83 ng kg-1. In addition, the acceptable assayed results on precision, reproducibility, specificity and method accuracy for the analysis of real samples were also acquired. Importantly, our strategy can provide a signal-on competitive immunoassay for the detection of small molecules, e.g., mycotoxins and biotoxins, thereby representing a versatile sensing schemes by controlling the corresponding antibody or hapten in the analysis of food safety.