Assembly of Multifunctionalized Gold Nanoparticles with Chemiluminescent, Catalytic, and Immune Activity for Label-Free Immunoassays

In this study, we report a universal label-free immunoassay to detect antigen based on multifunctionalized gold nanoparticles (MF-GNPs), which were obtained by successive assembly of N-aminobutyl-N-ethylisoluminol functionalized gold nanoparticles (ABEI-GNPs) with antibody, bovine serum albumin (BSA) and Co2+. MF-GNPs exhibited excellent chemiluminescent (CL), catalytic and immune activity. It was demonstrated that the CL signal of MF-GNPs decreased in the presence of antigens via antigen–antibody specific binding using human immunoglobulin G (hIgG) and corresponding antibody goat anti-human IgG (anti-hIgG) as a model system, due to that immunoreaction led to the aggregation of GNPs. According to the decreased CL intensity, hIgG could be determined in the range of 1.0 fM to 1.0 nM with a low detection limit of 0.13 fM. Furthermore, this CL strategy was also confirmed to be a general one by replacing hIgG with heart-type fatty acid-binding protein (H-FABP), which is a biomarker of early acute myocardial infarction (AMI). The CL strategy could be employed to detect H-FABP ranging from 10.0 fM to 10.0 nM, and the detection limit is 7.8 fM. The CL strategy also showed good selectivity. It might be extended to detect other antigens if their corresponding antibodies are available.