Preparation of a novel immunosensor for tumor biomarker detection based on ATRP technique

A novel electrochemical immunosensor for sensitive detection of a tumor marker is reported. This protocol involves the surface-initiated atom transfer radical polymerization (SI-ATRP) of poly(ethylene glycol) monomethacrylate (PEGMA) on an indium tin oxide (ITO) electrode. Using carcinoembryonic antigen (CEA) as a model analyte, capture anti-CEA (Ab₁) was conjugated to poly(poly(ethylene glycol) monomethacrylate) (P(PEGMA)) brushes, via activation of hydroxyl groups by succinic anhydride and N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and N-hydroxysulfosuccinimide sodium salt (NHS/EDC). After the sandwich immunoreaction, the horseradish peroxidase-labeled signal anti-CEA antibodies were used to conjugate gold nanoparticles (HRP-Ab₂-AuNPs bioconjugates). Under optimized conditions, the proposed immunosensor showed a high sensitivity and a linear range from 5 × 10^-2 to 20 ng mL^-1 with a low detection limit of 1.09 × 10^-3 ng mL^-1. The assay results of clinical serum samples were in acceptable agreement with the reference values. The designed immunoassay system with ultrahigh sensitivity and being efficient and economical, might have potentially broad applications in protein diagnostics and bioassay.