Biomedical Engineering Reference
In-Depth Information
Fig. 6.20
I
D
characteristic of OS-FET
V
G
a
before open
sandwich
710
after open
sandwich
705
13.1 mV
700
695
69
0.03
0.04
0.05
0.06
0.07
0.08
b
710
before treatment
after treatment
705
4.5 mV
700
695
69
0.03
0.04
0.05
0.06
0.07
0.08
Gate voltage, V
The above results demonstrate that the reassociation of MBP V
L
and V
H
chains
with a small antigen can be directly transduced into electrical signal using the FETs
and that the OS-IA can be realized essentially on the basis of intrinsic molecular
charges without any labels. From the point of view of practical application, it
is required to detect BPA at the possible lowest adverse effect concentration.
According to a report of the National Toxicology Program in 2008 (
http://ntp.
niehs.nih.gov/
)
, the lowest, but controversial, dose levels that can induce a variety
of adverse effects are 0:0024
0:01g=kg=day. Assuming that the amounts of
BPA are taken from beverages, the concentration is estimated to be 10-60 ng/ml
(43-260 nM), which is completely within the working range of OS-FET.
It is possible to integrate multiple FETs and signal processing circuits in a single
chip using advanced semiconductor technology. Simultaneous analyses of various
small antigens in the environment or in our body can be realized on the basis
of the FETs. Since the output of the FET is an electrical signal, standardization
of the results obtained is easier than those with the chemiluminescence-based
analyses. Therefore, the platform based on the FETs is suitable for a label-free,
highly sensitive, and quantitative detection system for small antigen analysis in
environmental, food, and clinical research.
