An alternative microbiosensor for hydrogen peroxide based on an enzyme field effect transistor with a fast response
✍ Scribed by Alexandre A. Shul'ga; Timothy D. Gibson
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 612 KB
- Volume
- 296
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
The biosensor for hydrogen peroxide discussed in this article comprises horseradish peroxidase (EC 1 .11 .1 .7) immobilised onto the gate area of a probe-type pH-sensitive field effect transistor (ISFET) by cross-linking in glutaraldehyde vapour . The measurements are performed in a buffer solution containing potassium iodide or potassium hexacyanoferrate(II) as reducing substrates . The recycling of the redox state of the active centre of peroxidase by successive action of hydrogen peroxide and the reducing substrate results in a depletion of H+ ions inside the enzymatic layer that is detected by the ISFET . The biosensor response time is less than 2 s and the detection limit is 0.5 and 5 µM H 202 in 1 and 10 mM sodium phosphate buffer at pH 6 .0, respectively. The upper limit of the biosensor dynamic range may be extended up to several mM hydrogen peroxide by the increase of the reducing substrate concentration . At acidic pH the biosensor has higher sensitivity and wider dynamic range, while at pH > 6 the enzyme is subjected to a strong reversible inactivation . However, in the case of KI as a reducing substrate at pH < 5 stability of the immobilised enzyme is severely impaired resulting in a fast irreversible inactivation of peroxidase. The operational stability of the biosensor at pH 6 to 7 allows to make more than 1000 measurement cycles with less then 10% final attenuation of the response . The shelf-life of the biosensor constitutes at least several weeks when it is preserved in a dry state at + 4°C .