ABSTRACT
In this work, a novel and credible electrochemiluminescence immunoassay (ECLIA) was constructed for the ultrasensitive and highly selective detection of aflatoxin B1 (AFB1). Amino-functionalized 3D graphene hydrogel (NGH) served as the ECL platform with the self-enhanced ECL of luminol-palladium-graphene oxide (lum-Pd-GO) acting as a marker for the antibodies against AFB1. Pd-GO was synthesized by a self-redox method; it promotes the formation of reactive oxygen species, which are important to the ECL of luminol, from dissolved oxygen. The π-π conjunction between luminol and GO shortens their electron transfer distance, resulting in an amplified ECL signal (â¼8.5 times larger than conventional luminol ECL). Moreover, 3D NGH, with its good conductivity, large surface area, and sufficient amino groups, was used to anchor gold nanoparticles (AuNPs), which subsequently immobilized bovine serum albumin (BSA)-AFB1 through Au-S bonds. The resultant, competitive ECLIA gave a relative low detection limit of 5 × 10-3 µg kg-1 and exhibited a broad linear relationship over the range of 0.05-50 µg kg-1. Finally, the proposed ECLIA was successfully used to analyze AFB1 contents in food samples. ECLIA: electrochemiluminescence immunoassay; AFs: Aflatoxins; HPLC: high-performance liquid chromatography.
Subject(s)
Biosensing Techniques , Graphite , Luminescent Agents , Metal Nanoparticles , Aflatoxin B1 , Biosensing Techniques/methods , Electrochemical Techniques/methods , Gold/chemistry , Graphite/chemistry , Limit of Detection , Luminescent Agents/chemistry , Luminescent Measurements/methods , Luminol/chemistry , Metal Nanoparticles/chemistry , Palladium/chemistryABSTRACT
Based on an "assembling-fission" principle, stable sulfur quantum dots (SQDs) were synthesized using sublimed sulfur as a precursor and PEG-400 as a passivator. The fluorescence intensities (FIs) of SQDs were efficiently quenched by Cr(vi) due to formation of SQD/Cr(vi) complexes through the inner-filter effect. When ascorbic acid (AA) was introduced into the SQD/Cr(vi) system, SQD fluorescence was restored due to AA-induced reduction of Cr(vi) to Cr(iii). Consequently, a SQD-based "ON-OFF-ON" platform was constructed for sequential detection of Cr(vi) and AA. Under optimized conditions, the FIs of SQDs were linearly dependent on the concentrations of Cr(vi) and AA, yielding linear ranges of 0.005-1.5 and 0.01-5.5 mM with detection limits of 1.5 and 3 µM, respectively, in waters, serum and tablet samples. After a 24 h incubation, the SQDs displayed strong, quenched and recovered blue fluorescence, respectively, in the SQD, SQD/AAO/Cr(vi) and SQD/Cr(vi) systems in live HeLa cells and zebrafish embryos/larvae. A blue fluorescence was displayed in the yolk of zebrafish embryos, and yolk and head of larvae. This study demonstrates the efficacy of SQD systems for environmental and biological applications in complex matrices, and for direct observation of Cr bioaccumulation in organisms by bioimaging.
