Ultrasensitive Eletrogenerated Chemiluminescence Immunoassay by Magnetic Nanobead Amplification

An ultrasensitive electrogenerated chemiluminescence (ECL) immunoassay was proposed by using magnetic nanobeads (MNBs) as the carrier of ECL labels for ECL emission amplification. Carcinoembryonic antigen (CEA) and MNBs were initially immobilized on a platform in 1:1 molar ratio via sandwich immunoreaction. Subsequently, the MNBs were released from the platform and labeled with Ru(bpy)(3)(2+) species. After the MNBs with Ru(bpy)(3)(2+) were immobilized oil an Au electrode, ECL of the Ru(bpy)(3)(2+) was measured for CEA determination. A linear relation between the ECL intensity and CEA concentration was obtained in a range of 1x10(-14) to 3x10(-13) mol/L (2.0 to 60 pg/mL) with a limit of detection of 8.0x10(-15) mol/L (1.6 pg/mL).