Osaka Prefecture University

Electrochemical Detection of Viable Bacterial Cells Using a Tetrazolium Salt: a Novel Technique Achieving up to 10,000-fold Higher in Sensitivity Than the Limit of Detection!

LastUpDate: September 26, 2018

Kengo Ishiki, Graduate Student, Dr. Dung Q. Nguyen, Dr. Hiroshi Shiigi and other members of their research group in Department of Applied Chemistry, Osaka Prefecture University, developed a new technique for electrochemical detection of viable bacterial cells using Tetrazolium salt(*1).

This technique enabled electrochemical detection of bacterial cells in less incubation time and achieving up to a 10 000-fold increase in sensitivity over the limit of detection for MTT colorimetric assays(*2). As this in situ lysis-adsorption technique can be applied to any microbial cells adsorbed to the electrode surface, it would be useful for determining the number of microorganisms to prevent infectious diseases, food poisoning and control quality of foods while contributing to bioelectricity and developing biosensors.

The research findings were published in an online journal of Analytical Chemistry and the images in the paper have been selected as cover art.

Article title: Electrochemical Detection of Viable Bacterial Cells Using a Tetrazolium Salt

Main point of research

Dark field images of sphere-like FORMH crystals generated around bacterial surface, image

Dark field images of sphere-like FORMH crystals generated around bacterial surface

  • Fast, simple, and sensitive bacterial detection using Tetrazolium salt has been developed.
  • The viability of various bacterial species can be detected.
  • Quantitative assays can be possible for the variety of cell metabolism.


*1 Tetrazolium salt

Tetrazolium salt is a color indicator used for assessing cellular metabolic activity. It is reduced by enzymes in cells and electron carriers, and produces formazan. Enzyme activity and respiration activity can be assessed by colorimetric results of the purple or red color of formazan.

*2 MTT Assay

The MTT assay is a colorimetric assay for assessing cell metabolic activity. NAD (P) H-dependent cellular oxidoreductase enzymes may reflect the number of viable cells present. These enzymes are capable of reducing the tetrazolium dye MTT 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide to its insoluble formazan, which has a purple color. Tetrazolium dye assays can be used to measure cytotoxicity or cytostatic activity of potential medicinal agents and toxic materials.

Research Grant

This work was financially supported by the Ministry of Agriculture, Forestry, and Fisheries through a Science and Technology Research Promotion Program for the agriculture, forestry, fisheries, and food industries (25020A), and by Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid for Scientific Research (B) (KAKENHI 25288039, 16H04137)


Graduate School of Engineering
Dr. Hiroshi Shiigi

E-mail shii [at] *Please change [at] to @.