Gold nanoparticles enhanced electrochemiluminescence of graphite-like carbon nitride for the detection of Nuclear Matrix Protein 22

A novel label-free electrochemiluminescence (ECL) immunosensor was developed for the detection of Nuclear Matrix Protein 22 (NMP 22) based on the graphite-like carbon nitride (g-C3N4) and gold nanoparticles (AuNPs). Graphite-like carbon nitride was firstly combined with AuNPs, which promoted the electrons transfer and enhanced the ECL intensity of g-C3N4 largely. Then, anti-NMP 22 was immobilized onto the electrode through Au–NH2 without the usage of crosslinking agents. The connection between AuNPs and antibody influenced the conductive performance of AuNPs, leading to some decrease of ECL intensity. Then, bovine serum albumin (BSA) solution was dropped on the surface to block nonspecific binding sites. Finally, after the specific immunoreaction between NMP 22 and anti-NMP 22, the ECL intensity decreased further, because the protein on the electrode hindered the diffusion of luminescent reagents and electrons toward the electrode surface. Therefore, a linear relation between ECL intensity and the logarithm of NMP 22 concentration was obtained from 50.0 pg mL−1 to 2.0 ng/mL (R2 = 0.988) with the detection limit of 10.0 pg mL−1. The proposed ECL immunosensor provides a rapid, simple, and sensitive immunoassay strategy for protein detection, which might be promising for clinical application.