Sandwich-type conductometric immunoassay of alpha-fetoprotein in human serum using carbon nanoparticles as labels

A simple and sensitive conductometric irnmunosensor for detection of alpha-fetoprotein (AFP) was designed using carbon nanoparticles as labels. The immunosensing probe was fabricated by means of the immobilization of monoclonal anti-AFP primary antibodies on an interdigitated conductometric transducer, while the detection antibodies were prepared using nanocarbon-conjugated horseradish peroxidase-labeled anti-AFP (CNP-HRP-anti-AFP). With a sandwich-type immunoassay format, the conjugated CNP-HRP-anti-AFP on the transducer was increased with the increase of AFP in the sample, and the conductivity of the immunosensor was decreased in the H2O2-KI system. Under optimal conditions, the immunosensor exhibited a wide dynamic range of 0.1-500 ng/mL with a detection limit of 50 pg/mL AFP at 3 sigma. The reproducibility and recovery were <10% and 83.9-112.3%, respectively. Interestingly, 45 clinical serum specimens were assayed using the conductometric immunosensor, and the results were in accordance with those obtained from our Clinical Laboratory using Roche 2010 Electrochemiluminescent Automatic Analyzer. (C) 2010 Elsevier B.V. All rights reserved.