Direct detection of the biological toxin in acidic environment by electrochemical impedimetric immunosensor

Changhoon Chai, Jooyoung Lee, Paul Takhistov

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


This study describes the direct detection of the biological toxin (Ricin) in acidic environment without pH adjustment by hydrophobically modified electrochemical impedance immunosensor (EII). The nano-porous aluminum substrate for EII was hydrophobically modified via self-assembled monolayer (SAM) of APTES. Biosensor for the detection of the Ricin was fabricated by the covalent cross-linking of antibody (Ab) with APTES-SAM. The immunoreactions between the immobilized Ab and the biological toxin in several diagnostic solutions were monitored by the electrochemical impedance spectroscopy (EIS) under the polarization of EII versus reference electrode. EII could detect the presence of the biological toxin in acidic foods in 20 mins without pH adjustment. The negatively charged ions including hydroxides would be adsorbed on the hydrophobic body of APTES-SAMs by the polarization during EIS analysis, and offset the effect of acids on the immunological activity of the immobilized Ab. It suggested that the adsorption of negatively charged ions helped to keep the immunological activities of the immobilized Ab on EII in acidic environment. Proposed mechanism of the localized pH adjustment that makes possible immunoreaction occurrence in low pH sample matrix is briefly discussed.

Original languageEnglish (US)
Pages (from-to)11414-11427
Number of pages14
JournalSensors (Switzerland)
Issue number12
StatePublished - Dec 2010

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Biochemistry
  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electrical and Electronic Engineering


  • Acidic foods
  • Antibody immobilization
  • Biological toxin
  • Direct detection
  • Electrochemical impedance
  • Hydrophobic surface modification
  • Immunosensor
  • Nano-porous aluminum
  • Ricin


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