Ca 2+ ion transport through channels formed by α-hemolysin analyzed using a microwell array on a Si substrate

Koji Sumitomo, Arianna McAllister, Yukihiro Tamba, Yoshiaki Kashimura, Aya Tanaka, Youichi Shinozaki, Keiichi Torimitsu

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


For the functional analysis of ion channel activity, an artificial lipid bilayer suspended over microwells was formed that ruptured giant unilamellar vesicles on a Si substrate. Ca 2+ ion indicators (fluo-4) were confined in the microwells by sealing the microwells with a lipid bilayer. An overhang formed at the microwells prevented the lipid membrane from falling into them and allowed the stable confinement of the fluorescent probes. The transport of Ca 2+ ions through the channels formed by α-hemolysin inserted in a lipid membrane was analyzed by employing the fluorescence intensity change of fluo-4 in the microwells. The microwell volume was very small (1-100fl), so a highly sensitive monitor could be realized. The detection limit is several tens of ions/s/μm 2, and this is much smaller than the ion current in a standard electrophysiological measurement. Smaller microwells will make it possible to mimic a local ion concentration change in the cells, although the signal to noise ratio must be further improved for the functional analysis of a single channel. We demonstrated that a microwell array with confined fluorescent probes sealed by a lipid bilayer could constitute a basic component of a highly sensitive biosensor array that works with functional membrane proteins. This array will allow us to realize high throughput and parallel testing devices.

Original languageEnglish
Pages (from-to)445-450
Number of pages6
JournalBiosensors and Bioelectronics
Issue number1
Publication statusPublished - 2012 Jan 15


  • Artificial lipid bilayer
  • Ion channels
  • Microwell array
  • Nano-biodevices
  • Suspended lipid bilayer


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