Biomedical Engineering Reference
In-Depth Information
Another productive approach is the hybridization of proteins onto organic thin fi lms. For example,
immobilization of proteins as molecular thin fi lms using LB technique is attractive, but proteins
sometimes suffer denaturation by high surface tension on the water surface. In order to overcome
this disadvantage, Okahata and coworkers prepared LB fi lms of lipid-coated enzyme (Figure 12.18A)
that could be obtained as a precipitate by mixing aqueous solutions of the enzyme (glucose oxidase
[GOD] in this case) [115]. Covering GOD with lipids successfully prevented the denaturation of the
proteins, even at the air-water interface. The lipid-coated enzymes were obtained as precipitates
by mixing aqueous solutions of the enzyme and the lipid, and the resulting lipid-coated enzymes
are soluble only in organic solvent. Therefore, the monolayer of the lipid-coated enzymes can be
prepared by spreading organic solution of the complex. The formed monolayer can be transferred
onto a solid support by the conventional LB technique. Glucose sensoring by a Pt electrode modifi ed
by the LB fi lms of lipid-coated GOD was demonstrated (Figure 12.18B) [116,117]. This method has
an advantage in economizing on the amount of protein. However, the disadvantage of the LB fi lm can
Electrode
(A)
Air
Lipid-coated
enzyme (GOD)
Water
(B)
O
2
Glucose
D
-Glucono-
δ
-lactone
H
2
O
2
e
−
O
2
+ H
+
Working electrode
(+0.60 V vs. Ag/AgCl)
Ag/AgCl
(reference and
counter electrodes)
FIGURE 12.18
(A) Transfer of monolayer of lipid-coated glucose oxidase (GOD) onto an electrode by
Langmuir-Blodgett (LB) technique. (B) Glucose sensor using the electrode modifi ed with lipid-coated GOD
fi lms.
