Impedimetric detection of bacteria by using a microfluidic chip and silver nanoparticle based signal enhancement

Renjie Wang, Yi Xu, Thomas Sors, Joseph Irudayaraj, Wen Ren, Rong Wang

Research output: Contribution to journalArticlepeer-review


The authors describe a method that can significantly improve the performance of impedimetric detection of bacteria. A multifunctional microfluidic chip was designed consisting of interdigitated microelectrodes and a micro-mixing zone with a Tesla structure. This maximizes the coating of bacterial surfaces with nanoparticles and results in improved impedimetric detection. The method was applied to the detection of Escherichia coli O157:H7 (E. coli). Silver enhancement was accomplished by coating E.coli with the cationic polymer diallyldimethylammonium chloride (PDDA) to form positively charged E. coli/PDDA complexes. Then, gold nanoparticles (AuNPs) were added, and the resulting E. coli/PDDA/AuNPs complexes were collected at interdigitated electrodes via positive dielectrophoresis (pDEP). A silver adduct was then formed on the E. coli/PDDA/AuNP complexes by using silver enhancement solutions and by using the AuNPs as catalysts. The combination of pDEP based capture and of using silver adducts reduces impedance by increasing the conductivity of the solution and the double layer capacitance around the microelectrodes. Impedance decreases linearly in the 2 × 103–2 × 105 cfu·mL−1E. coli concentration range, with a 500 cfu·mL−1 detection limit. Egg shell wash samples and tap water spiked with E. coli were successfully used for validation, and this demonstrates the practical application of this method. [Figure not available: see fulltext.].

Original languageEnglish (US)
Article number184
JournalMicrochimica Acta
Issue number3
StatePublished - Mar 1 2018
Externally publishedYes


  • Bacterial detection
  • Electrochemical impedance spectroscopy
  • Escherichia coli O157:H7
  • Gold nanoparticles
  • Interdigitated microelectrodes
  • Positive dielectrophoresis
  • Silver enhancement
  • Tesla structure

ASJC Scopus subject areas

  • Analytical Chemistry

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