4‑Amino-1-(3-mercapto-propyl)-pyridine Hexafluorophosphate Ionic Liquid Functionalized Gold Nanoparticles for IgG Immunosensing Enhancement

A novel ionic liquid, 4-amino-1-(3-mercapto-propyl)-pyridine hexafluorophosphate (AMPPH), was successfully synthesized and characterized. Subsequently, AMPPH was used as a functional monomer to fabricate AMPPH-modified gold nanoparticles (AMPPH–AuNPs) via a one-pot synthesis method. The as-prepared AMPPH–AuNPs were confirmed with transmission electron microscopy and X-ray photoelectron spectroscopy. AMPPH–AuNPs were used to construct a biocompatible interface to immobilize rabbit anti-human IgG (anti-HIgG) onto a glassy carbon electrode (GCE) surface, followed by a cross-linking step with glutaraldehyde to fabricate an anti-HIgG–AMPPH–AuNPs/GCE. The nonspecific binding sites were enclosed with bovine serum albumin (BSA) to develop an immunosensor for human IgG. Electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical properties of the developed immunosensor. The results indicate that AMPPH–AuNPs can improve the immunosensing performance. The current response of the immunosensor was found linearly related to human IgG concentration in the range of 0.1–5.0 ng mL^–1 and 5.0–100.0 ng mL^–1. The detection limit is estimated to be 0.08 ng mL^–1 (<i>S</i>/<i>N</i> = 3). The obtained immunosensor was successfully applied to the analysis human IgG immunoglobulin in human serum, and the results were well consistent with ELISA method