An ultrasensitive competitive immunosensor using silica nanoparticles as an enzyme carrier for simultaneous impedimetric detection of tetrabromobisphenol A bis(2-hydroxyethyl) ether and tetrabromobisphenol A mono(hydroxyethyl) ether

Based on our produced polyclonal antibody capable of recognizing tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) and tetrabromobisphenol A mono(hydroxyethyl) ether (TBBPA-MHEE) (cross-reactivity, 100% for TBBPA DHEE; 98.7% for TBBPA MHEE), an important derivative and byproduct of tetrabromobisphenol A (TBBPA), respectively, a novel ultrasensitive competitive immunosensor was established using an electrochemical impedimetric strategy for the simultaneous detection of both chemicals. A significantly amplified electrochemical impedance spectroscopy (EIS) for quantitative target analysis was obtained through (i) the biocatalytic precipitation of 4-chloro-1-naphthol (CN) on the electrode surface triggered by horseradish peroxidase (HRP) and (ii) increased amounts of the enzyme with HRP-loaded silica nanoparticles carrying poly-brushes (SiO2@PAA) as labels, achieving a remarkable improvement in catalytic performance. Under the optimized conditions, the immunosensor showed satisfactory accuracy (recovery, 84.6-118%) and a good linear range (0.21- 111.31 ng/mL) with a limit of detection (LOD) of 0.08 ng/mL (S/N = 3) for TBBPA DHEE and TBBPA MHEE. In addition, the proposed approach was used to analyse real environmental water samples, and our results indicated that this immunosensor had great potential for the determination of the trace pollutants in aquatic environments.