An immunoassay using an electro-microchip, nanogold probe and silver enhancement

Kuei Ling Su, Hao Hsuan Huang, Tsung Chain Chang, Hong Ping Lin, Yu Cheng Lin, Wei Ting Chen

Research output: Contribution to journalArticle

9 Citations (Scopus)


This paper presents a novel immunoassay using an electro-microchip to detect the immuno-reaction signal, gold nanoparticles (ANPs) as a label of antigen or antibody and as a catalyst for silver precipitation, and the silver enhancement reaction to magnify the detection signal. This study is based on the direct immunoassay (two-layer format) and the sandwich immunoassay (three-layer format). The ANPs are introduced to the electro-microchip by the specific binding of the antibodies - ANPs conjugates and then coupled with silver enhancement to produce black spots of silver metal. The silver precipitation constructs a "bridge" between two electrodes of the electro-microchip allowing the electrons to pass, and the variation of the impedance can be easily measured with a commercial LCR meter. Different gap sizes (20, 50, 100, and 200 μm) of the electrodes of electro-microchips were designed for the sensitivity study. The experimental data show that a chip with a 200 μm gap has the highest sensitivity. There is a significant difference in impedance between the experiment and the negative control after 10 min reaction time. The proposed method requires less time and fewer steps than the conventional enzyme-linked immunosorbent assay. In addition, it shows a high detection sensitivity [10 μg/mL of 1st antibody (IgG) immobilized on slides and 10 ng/mL of antigen (protein A)], and there is a clear distinction between the signal intensity and the logarithm of the sample concentration. This new immunoassay has potential applications in proteomics research and clinical diagnosis.

Original languageEnglish
Pages (from-to)93-98
Number of pages6
JournalMicrofluidics and Nanofluidics
Issue number1
Publication statusPublished - 2009

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Materials Chemistry

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