Sensitive and high-fidelity electrochemical immunoassay using carbon nanotubes coated with enzymes and magnetic nanoparticles

Yunxian Piao, Zongwen Jin, Dohoon Lee, Hye Jin Lee, Hyon Bin Na, Taeghwan Hyeon, Min Kyu Oh, Jungbae Kim, Hak Sung Kim

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)


We demonstrate a highly sensitive electrochemical immunosensor based on the combined use of substrate recycling and carbon nanotubes (CNTs) coated with tyrosinase (TYR) and magnetic nanoparticles (MNP). Both TYR and MNP were immobilized on the surface of CNTs by covalent attachment, followed by additional cross-linking via glutaraldehyde treatment to construct multi-layered cross-linked TYR-MNP aggregates (M-EC-CNT). Magnetically capturable, highly active and stable M-EC-CNT were further conjugated with primary antibody against a target analyte of hIgG, and used for a sandwich-type immunoassay with a secondary antibody conjugated with alkaline phosphatase (ALP). In the presence of a target analyte, a sensing assembly of M-EC-CNT and ALP-conjugated antibody was attracted onto a gold electrode using a magnet. On an electrode, ALP-catalyzed hydrolysis of phenyl phosphate generated phenol, and successive TYR-catalyzed oxidation of phenol produced electrochemically measurable o-quinone that was converted to catechol in a scheme of substrate recycling. Combination of highly active M-EC-CNT and substrate recycling for the detection of hIgG resulted in a sensitivity of 27.6nAng-1mL-1 and a detection limit of 0.19ngmL-1 (1.2pM), respectively, representing better performance than any other electrochemical immunosensors relying on the substrate recycling with the TYR-ALP combination. The present immunosensing system also displayed a long-term stability by showing a negligible loss of electrochemical detection signal even after reagents were stored in an aqueous buffer at 4°C for more than 6 months.

Original languageEnglish
Pages (from-to)3192-3199
Number of pages8
JournalBiosensors and Bioelectronics
Issue number7
Publication statusPublished - 2011 Mar 15


  • Carbon nanotube
  • Electrochemical immunoassay
  • Enzyme coating
  • Substrate recycling
  • Tyrosinase

ASJC Scopus subject areas

  • Biotechnology
  • Biophysics
  • Biomedical Engineering
  • Electrochemistry


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