Low-Cost and Highly Sensitive lmmunosensing Platform for Aflatoxins Using One-Step Competitive Displacement Reaction Mode and Portable Glucometer-Based Detection

Aflatoxins are highly toxic secondary metabolites produced by a number of different fungi and present in a wide, range of food and feed commodities. Herein, we designed a, simple and low-cost immunosensing platform for highly sensitive detection of mycotoxins (aflatoxm B-1, AFB(1), used as a model) on polyethylenimine (PEI) coated mesoporous silica nano containers (PEI-MSN). The assay was carried out by using a portable personal glucometer (PGM) as the readout based on a competitive displacement reaction mode between target AFB, and its pseudo-hapten (PEI-MSN) for monoclonal anti-AFB, antibody (mAb'). To construct such an assay protocol, two nanostructures including mAb-labeled gold nanoparticle (mAb-AuNP) and PEI-MSN were initially synthesized, and then numerous glucose molecules were gated into the pores based on the interaction between negatively charged inAb-AuNP and positively charged PEI-MSN. In the presence of target AFB(1), a competitive type displacement reaction was implemented between inAb-AtiNP and PEI-MSN by target AFB(1) through the specific antigen antibody reaction. Accompanying the reaction, target AFB, could displace the inAb-AuNP from the surface of PEI-MSN, resulting in the release of the loading glucose from the pores due to the gate opened. The released glucose molecules could be quantitatively determined by using a portable PGM. Under optimal conditions, the PGM signal increased with the increment of AFB, concentration in the range from 0.01 to 15 mu g/kg (ppb) with a detection limit (LOD) of 5 ng/kg (5 ppt) at the 3s(blanck) criterion. The selectivity and precision were acceptable. Importantly, the methodology was further validated for assaying naturally contaminated or spiked blank peanut samples, and consistent results between the PGM-based immunoassay and the referenced enzyme linked immunosorbent assay (ELISA) were obtained. Therefore, the developed immunoassay provides a promising approach for rapid screening of organic pollutants because it is simple, low-cost, sensitive, specific, and without the need of multiple separation and washing steps.