Physics And Chemistry Basis Of Biotechnology - De Cuyper - tiera.ru

Elisabeth Csöregi et al
addition of free-diffusing mediators, co-factors, etc. Most of these electrode designs
make use of a mediated electron-transfer mechanism (as shown in scheme 2), the
mediating molecules being covalently immobilised either on conducting (e.g.
polypyrrole) or non-conducting (e.g. poly vinyl imidazole) polymeric backbones (see
figure 4).
Figure 4. Mediated electron-transfer pathway with both the enzyme and the redox
mediator (stars) immobilised either on conducting or non-conducting polymeric chains.
These constructions offer an efficient electron transfer and improved stability, mainly
due to the lack of any free-diffusing components. One of the most promising
approaches makes use of enzymes entrapped in redox polymers (non-conducting
polymers modified with highly efficient Os- or Ru-complexes as mediators, often
called “wires”). The redox polymer integrated enzymes result in highly permeable,
efficient, and stable redox hydrogels [28, 29]. In this design, the mediator is retained in
the close proximity of the enzyme’s redox centre and electrons are rapidly exchanged
(via electron hopping between the relaying redox centres along the wire and/or
occasionally crossing between undulating segments of the wires) assuring an efficient
electron-transfer pathway.
Practical examples of this type of biosensor (developed in our laboratories) with
potential application in food and/or beverage industry are presented in the following
section. Detection of hydrogen peroxide (as above mentioned) constitutes the base of
sensing many other analytes, therefore one of the hereby presented examples is
considering development of hydrogen peroxide sensors based on different, newly
isolated, purified, and characterised plant peroxidases (4.1) [21]. The other two
examples focus on the detection of biomarkers (biogenic amines) using amine oxidase
entrapped in redox hydrogels (4.2) [30-32] and monitoring of alcohol using a newly
isolated and characterised PQQ-dependent (oxygen independent) alcohol
dehydrogenase (4.3) [33] (adsorbed on graphite, glassy carbon or platinum electrodes
and entrapped in conducting or redox polymers, respectively).
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