Biomedical Engineering Reference
In-Depth Information
Urea
2NH
3
+CO
2
Glass fiber
filter
Urease
Copper wire
Figure 1.9
Schematic image of the urea biosensor. (Reprinted with permission from [48];
Copyright © 2012 Wiley).
common interferents such as ascorbic acid, glucose and urea and a half-life
at around 3 months.
A miniaturized potentiometric urea lipid i lm-based biosensor based on
GSs successfully exfoliated onto a thin copper wire has been developed by
Nikoleli
et al.
[48] (Figure 1.9). h e reported potentiometric urea biosen-
sor exhibited good reproducibility, an excellent output stability, reusability,
selectivity, rapid response times ( 4 s), long shelf life and high sensitivity of
ca. 70 mV decade
-1
over a wide logarithmic range of urea concentrations,
from 1×10
-6
M to 1×10
-3
M.
h e Nikolelis Research Group has also developed a novel and simply
fabricated potentiometric uric acid biosensor by immobilization of uri-
case into stabilized lipid i lms using ZnONWs as measuring electrode
[41]. Uricase was incorporated into the lipid i lm prior to polymerization
on the surface of well-aligned ZnONWs, resulting in a sensitive, selec-
tive, stable, reproducible and fast responding UA biosensor. h e novelty
of the presented work was also that the use of the positively charged lipid
increased the concentration of UA at the electrode surface, thus providing
a slope two times larger. In addition, the use of the lipid i lm retained the
activity of the enzyme for a longer period of time. h e sensor response
had negligible interferences by normal concentrations of ascorbic acid,
glucose, urea, proteins and lipids. h e biosensor was applied using a l ow
injection analysis (FIA) system, either in continuous or in stopped-l ow
modes. Since the sensor is low-cost with appreciable reproducibility, it
may of er an easy extension to on-spot clinical diagnosis. It is also con-
venient to assemble into portable chip-based sensing devices suitable for
unskilled users.
