Page 408 - Organic Electronics in Sensors and Biotechnology

Electrophoretically Deposited Polymers for Organic Electronics 385

10.3.4 Biosensors
As mentioned, the electrophoretic technique is known to yield uni-
9
form, dense, and porous conducting polymer films. In this context,
EPD from a colloidal suspension of a conducting polymer has been
shown to result in nanostructured conjugated polymer films. 10–12
Nanostructured polymer matrices have been found to provide
99
increased surface area for high enzyme loading. Furthermore, the
high surface free energy of a nanostructured film strengthens binding
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and stabilizes the desired enzyme. These unique properties of
nanostructured conducting polymers offer excellent prospects for
interfacing biological recognition events with electronic signal trans-
duction and for designing new bioelectronic devices. Dhand et al. 9
have studied electrophoretically deposited nanostructured PANI film
for application to a cholesterol biosensor. These nanostructured PANI
derived bioelectrodes (ChOx/PANI/ITO) exhibit linearity up to
400 mg/dL of cholesterol (Fig. 10.8), sensitivity of 7.76 × 10 Abs ×
−5
(mg/dL) with negligible (0.1%) interference. Besides this, the value
−1
of the apparent Michaelis-Menten constant K app indicative of
m
enzyme-substrate interactions, has been found to be 0.62 mM. This
low value K app for ChOx/PANI/ITO bioelectrode reveals increased
m
enzyme (cholesterol oxidase)-substrate (cholesterol) interactions,
indicating distinct advantage of this matrix over other matrices used
for cholesterol biosensor fabrication.
Dhand et al. have also reported the preparation of a nanostructured
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composite film comprising emeraldine salt (ES) and carboxyl group

7.5
7.0
6.5

6.0
× 10 –2 5.5
Abs 5.0

4.5
4.0
3.5
3.0
0 100 200 300 400 500
Conc. (mg/dL)
FIGURE 10.8 The calibration plot of ChOx/PANI/ITO bioelectrode: absorbance
as a function of cholesterol concentration.