Plasmonic ELISA Based on Nanospherical Brush-Induced Signal Amplification for the Ultrasensitive Naked-Eye Simultaneous Detection of the Typical Tetrabromobisphenol A Derivative and Byproduct

Indirect competitive-structured electrochemical immunosensor for tetrabromobisphenol A sensing using CTAB-MnO2 nanosheet hybrid as a label for signal amplification

Tetrabromobisphenol A (TBBPA) is a kind of brominated flame retardant that is usually added to products to reduce their flame retardancy. However, its extensive use has resulted in their residues being found in the environment, which is very harmful. Herein, an indirect competitive immunosensor has been established for TBBPA detection based on the signal amplification system. Pd nanospheres in situ reduced on the surface of MnO₂ nanosheet hybrid (MnO₂/Pd) was used as the label for the secondary antibody through the Pd-N bond, and gold-toluidine blue composite was loaded onto MWCNTs (MWCNTs/Au-TB), which functioned as the platform for the immunosensor. The spherical structure of Pd had abundant catalytic active sites, which enhanced the catalytic activity of MnO₂/Pd as the label, hence amplifying the signal response. Besides, MWCNTs/Au-TB improved electron transfer and produced a strong signaling pathway for immobilizing antigens through the Au-NH₂ bond, which can specifically recognize primary antibodies to improve sensitivity. The immunosensor had a linear concentration range of 0-81 ng/mL, a low detection limit of 0.17 ng/mL (S/N = 3), with good stability, selectivity, and reproducibility based on the above advantages. Additionally, the acceptable accuracy and recoveries (recoveries, 92-124%; CV, 3.3-8.8%) in the real water sample analysis indicated that this strategy is promising for emerging pollutant analysis.

High-throughput chemiluminescence immunoassay based on Co2+/hemin synergistic catalysis for sensitive detection tetrabromobisphenol A bis(2-hydroxyethyl) ether in the environments

Here, a novel chemiluminescence (CL) immunoassay was fabricated for sensitive determination of tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE), one of typical tetrabromobisphenol A derivatives. At the indirectly competitive method, the synthesized PS@hemin@Co²⁺ was labelled by secondary antibody (Ab₂) instead of common natural enzymes, which showed excellent catalysis towards the decomposition of luminol-H₂O₂ for producing CL signal. Furthermore, the CL signal was greatly amplified owing to the synergistic catalysis of hemin and Co²⁺ in the detection system. Under the optimized conditions, the established method offered (i) low detection limit (LOD, 0.9 μg/L), which was almost 5 times lower than that using a conventional ELISA with the same antibody; (ii) a good linearity (1.6-14.3 μg/L); (iii) satisfactory accuracy and precision (recoveries, 89.67-125.33%; CV, 2.75-8.37%). The proposed CL immunoassay was applied for analysis of environmental samples from various sources collected from Jiangsu and Zhejiang province, China. And the detected concentrations were ranged in 2.4-3.7 μg/L in environmental waters and 1.8-2.4 ng/g (dry weight, dw) in soil samples, indicating great potential for trace TBBPA-DHEE detection from environmental samples.

A semiconductor quantum dot-based ratiometric electrochemical aptasensor for the selective and reliable determination of aflatoxin B1

In recent years, a ratiometric electrochemical method has been investigated due to its ability to effectively reduce the background electrical signals via the introduction of an internal calibration mechanism, which has great practical significance in the detection of mycotoxins in foods. Herein, we report a ratiometric electrochemical aptasensor based on two semiconductor quantum dots (i.e. CdTe and PbS QDs) for the detection of aflatoxin B1 (AFB1). The aptasensor was fabricated by immobilizing PbS QD-coated silica hybrid spheres (SiO2@PbS) onto CdTe QD-modified Fe3O4@SiO2 (Fe3O4@SiO2/CdTe) surface through biorecognition between the aptamer and complementary DNAs, where PbS QDs acted as external signal labels and CdTe QDs acted as internal reference labels. In the presence of AFB1, the aptamer connected to SiO2@PbS preferred to form an aptamer/AFB1 complex, which brought about the separation of SiO2@PbS linked with the CdTe QDs; with the addition of more AFB1 to the solution, the amount of SiO2@PbS present on the Fe3O4@SiO2/CdTe surface reduced. After several steps of endonuclease cleavage, magnetic separation, and dissolution with acid, the square wave voltammetry signals of Pb2+ and Cd2+ maintained an inverse relationship with the target content based on the SWV stripping measurements; the proposed method had the wide linear range of 5 pg mL-1-50 ng mL-1 and the determination limit of 4.5 pg mL-1 (S/N = 3) and was applied for the detection of AFB1 in peanuts. The proposed aptasensor has an important practical significance for the development of food safety.