Indirect competitive-structured electrochemical immunosensor for tetrabromobisphenol A sensing using CTAB-MnO 2 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 MnO 2 nanosheet hybrid (MnO 2 /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 MnO 2 /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-NH 2 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. Graphical abstract