Detection of bisphenol-A using electrochemical immunosensor: Comparison between competition and displacement format assay

Antibodies against bisphenol-A (Ab ∝ BPA) and BPA-butyric-horseradish peroxidase (HRP) were generated and utilised to fabricate a gold-nanoparticles (AuNPs)-based electrochemical biosensor for the detection of BPA. The glassy carbon electrode surface was modified with AuNPs via chronoamperometry (CA) to increase the surface-to-volume ratio and provide a robust sensing surface. The Abs ∝ BPA were generated and immobilized on the AuNP-modified electrode using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) method with thioctic acid as linker. The assay was conducted using competition and displacement formats. Then, the working electrode, counter electrode and reference electrode were placed in a phosphate-buffered saline (PBS) containing ferrocenemethanol (FcOH) and H2O2. Sensitivity data were interpreted using the same sensor surface, enabling a direct comparison between the reduction currents of the oxidized form of ferrocenemethanol in the two assay formats which indicated the concentration of BPA bound to Ab ∝ BPA. Starting from a pre-blocked sensor surface, the competition assay was completed in 1 h and the displacement assay took 2 h. The limit of detection (LOD) in competition assay and displacement assay were 12.35 μg L− 1 and 4.11 μg L− 1, respectively.