Biomedical Engineering Reference
In-Depth Information
there is no need to amplify the sensing signals using an external amplifier; use is made of the
charge accumulation cycles. Their penicillin biosensor exhibits excellent performance cha-
racteristics: a high sensitivity (47.9 mV/mm), a high signal-to-noise ratio, a large span
(1445 mV), a wide linear range (0-25 mM), and a quick response time (less than 3 s).
Besides, their biosensor demonstrates good reproducibility. In addition, 0.01 mM was the
lower detection limit exhibited by their biosensor. Finally, they assert that their biosensor
clearly exhibits a better performance than the presently widely used ISFET penicillin biosen-
sor. For example, their biosensor is about eight times more sensitive than the present ISFET
biosensor. The authors have used their biosensor to measure penicillin concentrations in pen-
icillin fermentation broths.
Lee et al. (2009)
indicate that their CTTPS is constructed by immobilizing penicillinase onto
the ion-sensitive membrane Si
3
N
4
of a pH-CCD (pH sensor based on charge-coupled device).
Their CTTPS device is able to detect variations in the hydrogen ion (H
รพ
) concentration due
to the catalyzed hydrolysis of penicillin by the enzymatic reaction. The authors indicate that
charges corresponding to the penicillin concentration are repeatedly transferred from a sens-
ing part to the floating diffusion region. The signal charges are accumulated here. The
authors assert that their biosensor is stable, and could be a new device that may be used in
the health care field.
3.2.19 Fabrication of Biosensors Using Platinum Nanowire Nanoelectrode Array
(
Yang et al., 2006
)
Yang et al. (2006)
have developed a glucose biosensor using a platinum nanowire
nanoelectrode array (NEA). These authors used the platinum nanowires to fabricate a biosen-
sor array. They indicate that platinum nanowire arrays can be grown by electrodeposition in a
polycarbonate membrane. They report that the nanowire array so prepared may be considered
as a NEA, which improves the signal-to-noise ratio and decreases the detection limit. They fur-
ther assert that the high surface area of the platinum electrode helps minimize the problems
associated with conventional platinum electrodes because of the limited electroactive sites.
The sensitivity of their NEA for hydrogen peroxide is fifty times larger than that observed with
conventional platinum electrodes. Their biosensor was able to determine glucose concentration
in the 10
6
to 3
10
2
M range, interference free. They assert that their biosensor has a high
efficiency of signal transduction, and is able to determine glucose concentrations in real blood
samples. The authors report that their nanostructuring process not only increases surface area
and the number of electroactive sites, but also expands the upper detection limit. They point
out that their glucose oxidase is stable when adsorbed onto the electrode surface. Finally, their
biosensor fabrication method should be readily applicable to other biosensor applications
where other oxidases are used, for example, for the detection of choline, cholesterol, and alco-
hol. Thus, their biosensor fabrication method is perhaps generic in nature.
