Biomedical Engineering Reference
In-Depth Information
In order to achieve these studies, it is necessary to develop a biochemical
sensor that allows in vivo and on-line measurement of humoral factors with
both a very high sensitivity and specificity, or a multi-channel neural inter-
face that is able both to record signals from each nerve fiber (or nerve cell)
individually and also to stimulate them individually.
Recent striking advances in micro-electromechanical systems, tissue en-
gineering, biotechnology, biomaterials, and electrochemical techniques are
making it possible to realize these sensors or neural interfaces, and the deve-
lopment of these devices will surely mean that the next generation of artificial
organs or bionic human systems will make notable progress.
4.2
The Electrochemical DNA Chip Sensor
4.2.1 Introduction
The detection of sequence-specific DNA is of great significance in biomedical,
environmental, and food analyses. Recent progress in fabrication on chip, the
DNA microarray, using photolithography or arrayer methods, has opened up
a new window to nucleic acid analysis applications. This includes sequence
analysis, genotyping, and gene expression monitoring. Electrochemical detec-
tion has many advantages, such as reducing the size of the total detection
system, compared to a current fluorescence DNA chip system. Therefore,
portability and point-of-care testing will be realized. Sensor chips can be fa-
bricated by a mass production system based on lithography and microarray
technology, and it is possible to an produce inexpensive sensor. By combina-
tion with mTAS, which is a micro total analysis system based on micromachi-
ned technology, more intelligent chip design can be possible for automated
flow analyses. Table 4.1 indicates examples of previously reported electro-
chemical DNA sensors, especially focused on the intercalator type DNA sen-
sor. Metal complexes such as [Co(bpy)
3
]
3+
, [Co(Phen)
3
]
3+
, and [Os(bpy)
3
]
2+
function as cationic redox mediators, because DNA polymer has much ne-
gatively charged phosphate and interact easily with cationic compounds. On
the other hand, the antibiotic Daunomycin or the dye Hoechst 33258 have
different kinds of anity; for example, Hoechst is considered to bind with the
minor groove of duplexed DNA. Ishiimori first reported a DNA sensor using
Hoechst dye [5]. The ferrocenyl naphtalene diimide developed by Takenaka
was a different type of intercalator that was a unique and specific bind with
duplex DNA [6]. In this study, we used Hoechst intercalator and designed
andpreparedanintegratedDNAchipsensor.
In this section, we report the electrochemical detection of DNA and PCR
by microfabricated electrodes and microfluidic chips, respectively.
4.2.2 The Multiplexed Electrochemical DNA Sensor
The principle and preparation of our electrochemical DNA sensor is shown
in Fig. 4.5.
