Biomedical Engineering Reference
In-Depth Information
Fig. 6.12
Crown
ether-modified gate transistor
for K
C
detection
and rinsed. Finally, the chemical structure shown in Fig.
6.12
was synthesized. This
monolayer does not contain plasticizer, and ionophore is chemically incorporated to
the gate insulator, so there is no expected cytotoxicity.
In order to investigate the electrical characteristics of FET, a semiconductor
parameter analyzer was used. Measurement was performed in 2[4-(2-hydroxyethyl)-
1-piperazinyl] ethanesulfonic acid (HEPES) buffer solution, and pH of the sample
solution was adjusted to 7.4 with Ca.
OH
/
2
.Œ
Ca
.
OH
/
2
1:7 mM/.AndK
C
con-
centration was adjusted to 10
4
, 10
3
, 10
2
,and10
1
M with KCl. The prepared
FET was immersed in the sample solution, and then the V
T
change was measured.
The effect of K
C
concentration on the electrical signal of prepared FET was
investigated. The electrical response of prepared FET to K
C
concentration was
4.2 mV/decade. The slope was relatively small compared to that of the Nernstian
response. This could be because the density of ionophore immobilized onto the
FET gate surface is low. Further investigation toward improved sensitivity and
selectivity to K
C
is currently underway. The surface potential shift to negative
direction indicates the increase of K
C
with positive charge on the crown ether-
modified gate insulator. Thus, the variation of K
C
concentration was successfully
detected using the prepared FET. The prepared device showed the electrical signals
of potassium ion release through cell membrane caused by programmed cell death
“apoptosis.” Also, measurement of DNA molecular recognition or antigen-antibody
reaction requires chemical immobilization of probe molecules for target ones using
spacer molecules of monolayer or polymer membrane.
D
6.3.3
Biologically Induced Interface
Figure
6.13
shows a schematic illustration of biologically induced interface. A cell A
is composed as an interface functional cell and induce a signal based on a target cell
B to a semiconductor device as if an interface material plays its role. A cultured cell
