Portable visual quantitative detection of aflatoxin B1 using a target-responsive hydrogel and a distance-readout microfluidic chip

Abstract

Aflatoxin B₁ (AFB₁), as the secondary metabolite of molds, is the most predominant and toxic mycotoxin that seriously threatens the health of humans and animals. In this work, an AFB₁-responsive hydrogel was synthesized for highly sensitive and portable detection of AFB₁. The AFB₁-responsive hydrogel was prepared using an AFB₁ aptamer and its two short complementary DNA strands as cross-linkers. For visual detection of AFB₁, the hydrogel is preloaded with gold nanoparticles (AuNPs). Upon introduction of AFB₁, the AFB₁ aptamer binds with AFB₁, leading to the disruption of the hydrogel and release of the AuNPs with a distinct color change of the supernatant from colorless to red. In order to lower the detection limit and extend the method to quantitative analysis, a distance-readout volumetric bar chart chip (V-chip) was combined with an AFB₁-responsive hydrogel preloaded with platinum nanoparticles (PtNPs). In the presence of AFB₁, the hydrogel collapses and releases PtNPs which can catalyze the decomposition of H₂O₂ to generate O₂. The increasing gas pressure moves a red ink bar in the V-chip and provides a quantitative relationship between the distance and the concentration of AFB₁. The method was applied for detection of AFB₁ in beer, with a detection limit of 1.77 nM (0.55 ppb) where an immunoaffinity column (IAC) of AFB₁ was used to cleanup and pre-concentrate the sample, which satisfies the testing requirement of 2.0 ppb set by the European Union. The combination of an AFB₁-responsive hydrogel with a distance-based readout V-chip offers a user-friendly POCT device, which has great potential for rapid, portable, selective, and quantitative detection of AFB₁ in real samples to ensure food safety and avoid subsequent economic losses.