Ultrasensitive electrochemical detection of miRNA-21 by using an iridium(III) complex as catalyst

Xiangmin Miao, Wanhe Wang, Tianshu Kang, Jinbiao Liu, Kwok Keung Shiu, Chung Hang Leung, Edmond Dik Lung Ma*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

76 Citations (Scopus)


The ultrasensitive electrochemical detection of miRNA-21 was realized by using a novel redox and catalytic “all-in-one” mechanism with an iridium(III) complex as a catalyst. To construct such a sensor, a capture probe (CP) was firstly immobilized onto the gold electrode surface. In the presence of miRNA-21, a sandwiched DNA complex could form between CP and a methylene blue (MB) labeled G-rich detection probe modified onto a gold nanoparticle (AuNP) surface (DP-AuNPs). Upon addition of K+, the structure of DP changed to a G-quadruplex. Then, the iridium(III) complex could selectively interact with the G-quadruplex, catalyzing the reduction of H2O2, which was accompanied by an electrochemical signal change using MB as an electron mediator. Under optimal conditions, the electrochemical signal of MB reduction peak was proportional to miRNA concentration in the range from 5.0 fM to 1.0 pM, with a detection limit of 1.6 fM. In addition, satisfactory results were obtained for miRNA-21 detection in human serum samples, indicating a potential application of the sensor for bioanalysis.

Original languageEnglish
Pages (from-to)454-458
Number of pages5
JournalBiosensors and Bioelectronics
Publication statusPublished - 15 Dec 2016

Scopus Subject Areas

  • Biotechnology
  • Biophysics
  • Biomedical Engineering
  • Electrochemistry

User-Defined Keywords

  • Electrochemical biosensor
  • Iridium(III) complex
  • miRNA-21


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