Development of an immunoassay based on impedance measurements utilizing an antibody-nanosilver probe, silver enhancement, and electro-microchip

Chia Hsien Yeh, Wei Ting Chen, Hong Ping Lin, Tsung Chain Chang, Yu Cheng Lin

Research output: Contribution to journalArticle

21 Citations (Scopus)


This study reports a new, simple and sensitive immunoassay that uses the impedance variation caused by silver nanoparticles (AgNPs) coated with an antibody. In this method, an electro-microchip is used to detect the immuno-reaction signal of antibody-antigen recognition, AgNPs as a label of antibody and a catalyst for silver precipitation, and the silver enhancement reaction is used to magnify the detection signal. Our model format is based on the sandwich immunoassay (three-layer format). The AgNPs were introduced into the electro-microchip by the specific binding of the antibodies and then coupled with silver enhancement solution to reduce silver ions to silver metal. The silver precipitation constructs a "bridge" between two electrodes of the electro-microchip allowing the electrons to pass. There was a significant difference in impedance between the experimental sample and the negative control after 10 min of reaction time. The proposed method requires less time and fewer steps than enzyme-linked immunosorbent assay (ELISA). It also has a high detection sensitivity (10 μg/mL of 1st antibody (IgG) immobilized on slides and 0.1 ng/mL of antigen (protein A)). Therefore, a new immunoassay is constructed using an electro-microchip, antibody-AgNPs conjugates, and a silver enhancement reaction.

Original languageEnglish
Pages (from-to)387-393
Number of pages7
JournalSensors and Actuators, B: Chemical
Issue number2
Publication statusPublished - 2009 Jun 4


All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry

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