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

On the basis of H2 O2 -mediated growth of gold nanoparticle (AuNPs), a novel plasmonic enzyme-linked immunosorbent assay (pELISA) was developed with a polyclonal antibody for the ultrasensitive simultaneous naked-eye detection of tetrabromobisphenol A bis(2-hydroxyetyl) ether (TBBPA DHEE) and tetrabromobisphenol A mono(hydroxyethyl) ether (TBBPA MHEE), one of the major derivatives and byproducts of tetrabromobisphenol A (TBBPA), respectively. In this modified indirect competitive pELISA, glucose oxidase (GOx) played an important role leading to the growth of AuNPs through a reaction between GOx and glucose to produce hydrogen peroxide (H2 O2 ). In addition, further signal amplification was achieved via a large number of GOx molecules, which were immobilized on silica nanoparticles carrying poly brushes (SiO2 @PAA) to increase the enzyme load, and the whole complex was conjugated on the second antibody. Under the optimized conditions, 10-3 μg/L TBBPA DHEE can be distinguished via the observation of a colored solution, and the limit of detection (LOD) of the method using a microplate reader reaches 3.3 × 10-4 μg/L. In contrast, the sensitivity of the method was 3 orders of magnitude higher than that using conventional colorimetric ELISA with the same antibody. Furthermore, the proposed approach showed good repeatability and reliability after a recovery test fortified with a variety of targets was performed (recoveries, 78.00-102.79%; coefficient of variation (CV), 4.38-9.87%). To our knowledge, this is the first case in which pELISA was applied for the detection of small molecules via the production of H2 O2 from GOx and glucose. The method will be widely used for the investigation of TBBPA DHEE and TBBPA MHEE in real environments.