Portable visual quantitative detection of aflatoxin B₁using 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.

DNA hydrogel-empowered biosensing

“…Subsequently red ink was pushed upwards into the top channel by the O 2 bubbles that the migrated distance of the ink was in proportion with the target concentration. Using this method, cocaine could be detected at a concentration lower than 1 μM [76] and was additionally used for the detection of other targets such as ochratoxin A [77] and Aflatoxin B1 in beer, with a limit of detection of 1.77 nm [78]. Furthermore, in other similar work, the detection of uranium and lead were reported by utilizing a DNAzyme-substrate complex instead of the aptamer structure [79,80].…”

Microfluidic Technology for Nucleic Acid Aptamer Evolution and Application

“…Moreover, cocaine, various food contaminant toxin targets such as aflatoxin, botulinum toxin, and ochratoxin A have all gained the attention from aptamer‐based microfluidic researchers . Pavesi's group developed a microring resonator to detect aflatoxin in the nanomolar range 93b. Surface enhanced Raman spectrometry (SERS) was also introduced in a microfluidic system for the detection of ochratoxin A and polychlorinated biphenyls .…”

Transfer rates of aflatoxins from herbal medicines to decoctions determined by an optimized high-performance liquid chromatography with fluorescence detection method

“…However, for high‐performance extraction and sensitive determination of trace aflatoxins in complex herbal medicines, necessary sample pretreatment including clean‐up and enrichment steps must be introduced. As is well‐known, immunoaffinity column (IAC) is highly specific and selective towards selected mycotoxins to achieve the purification and clean‐up of complex matrix . In addition, taking the fluorescence quenching property of AFB 1 and AFG 1 in water solution into consideration, high‐performance liquid chromatography with fluorescence detection after post‐column photochemical derivatization (HPLC‐PCD‐FLD) is always the preferred alternative for rapid and sensitive detection of aflatoxins (AFs) in many complex matrices including herbal medicines and their decoctions.…”