Proximity hybridization-regulated electrogenerated chemiluminescence bioassay of α-fetoprotein via target-induced quenching mechanism

A proximity hybridization-regulated electrogenerated chemiluminescence (PLA-ECL) bioassay was developed for the detection of alpha-fetoprotein (AFP) on basis of the sensitization of gold nanoparticles (AuNPs) and target induced quenching mechanism. Ru(bpy)(3)(2+) was used as ECL signal while ferrocene (Fc) was used as ECL quencher. Ru(bpy)(3)(2+) was electrostatically adsorbed into the AuNPs/Nafion film prepared by casting the mixture of Nafion and AuNP5 onto the surface of glassy carbon electrode (GCE) to form an ECL platform (Ru(bpy)(3)(2+)/AuNPs/Nafion/GCE), which displayed strong ECL emissions. A recognition platform was fabricated by self-assembling a capture DNA via thiol-gold bond on the surface of Ru(bpy)(3)(2+)/AuNPs/Nafion/GCE. After sandwich immunoassay and proximity hybridization assay among capture DNA, AFP, a pair of antibody-oligonucleotide conjugates and a signal probe (DNA-Fc), Fc in DNA-Fc was brought close to the surface of electrode in conjunction with target induced ECL quenching. The ECL intensity decreased with the increasing concentration of the AFP and AFP was monitored with a linear range of 0.05-50 ng/mL along with a detection limit of 0.04 ng/mL. The ECL bioassay is successfully applied to the detection of AFP in serum samples with one-step recognition, short operating time and good accuracy. This method displays great potential for point-of-care testing and commercial application.