Sensitive sandwich immunoassay based on single particle mode inductively coupled plasma mass spectrometry detection

A sensitive sandwich type immunoassay has been proposed with the detection by inductively coupled plasma mass spectrometry (ICP-MS) in a single particle mode (time resolved analysis) The signal induced by the flash of ions (Au-197(+)) due to the ionization of single Au-nanoparticle (Au-NP) label in the plasma torch can be measured by the mass spectrometer The frequency of the transient signals is proportional to the concentration of Au-NPs labels Characteristics of the signals obtained from Au-NPs of 20 45 and 80 nm in diameters were discussed The analytical figures for the determination of Au-labeled IgG using ICP-MS in conventional integral mode and single particle mode were compared in detail Rabbit-anti-human IgG was used as a model analyte in the sandwich immunoassay A detection limit (3 sigma) of 01 ng mL(-1) was obtained for rabbit-anti-human IgG after immunoreactions with a linear range of 0 3-10 ng mL(-1) and a RSD of 8 1% (2 0 ng mL(-1)) Finally the proposed method was successfully applied to spiked rabbit-anti-human IgG samples and rabbit-anti-human serum samples The method resulted to be a highly sensitive ICP-MS based sandwich type immunoassay (C) 2010 Elsevier B V All rights reserved