Biomedical Engineering Reference
In-Depth Information
4.1 Introduction
h e detection of DNA sequences has gained important attention in recent
years, as their quick identii cation is important in a number of dif erent
i elds. h e determination of nucleic acid sequences from humans, animals,
bacteria and viruses is a departure point to solve dif erent kinds of prob-
lems, such as the investigation about infection or food and water contami-
nation caused by microorganisms, the detection of fraud in appreciated
food variants, the identii cation of genetic disorders and genetic diseases,
the studies on tissue matching and breeding origin, and the application
to forensic issues. In medical application, DNA analysis may be of great
help for a better diagnosis, or in the prevention and treatment of many
human diseases. Apart from this, in relation to the health i eld, pharma-
cological studies on modii cation of expression of certain genes by certain
active principles are one of the promising alternatives to minimize animal
experimentation. In diagnostic medicine two important applications can
be derived: 1) identifying infectious microorganisms, such as viruses or
bacteria responsible for disease, or 2) forecasting or coni rming a geneti-
cally inherited disease, and thus initiating prognosis treatment, even prior
to onset of the disease. With these assumptions, DNA biosensor technolo-
gies are rapidly developing as an alternative to the classical gene assays, due
to certain advantages they present such as low cost, rapid analysis, simple
equipment, possibility of miniaturization and analysis
in situ
[1, 2]. h e
biosensor technologies are those promising a simpler integration of high
technology diagnostic tools for faster response in the point-of-care.
Electrochemical impedance spectroscopy (EIS) is a powerful tech-
nique to characterize the electrical properties of a system, being sensitive
to surface phenomena and changes of bulk properties. Due to its ef ec-
tiveness to directly probe the interfacial properties (capacitance, electron
transfer resistance) of modii ed electrodes, EIS is becoming an attractive
electrochemical tool for numerous applications such as immuno- and
genosensing, enzyme activity determination, studies of corrosion and
characterization of surface phenomena [3]. h anks to these properties, this
electrochemical technique is rapidly being adopted for monitoring ai nity
interaction of biomolecules [4]. In more recent years, EIS has been widely
used for the detection of DNA hybridization occurring at the surface of a
sensing electrode.
On the other hand, the use of nanoscale materials for electrochemical
biosensing has seen an explosive growth during the last decade [5]. h ehuge
interest in nanomaterials is due to the ability to tailor their size and structure
to the biosensing function and to the exceptional properties they present
compared to the bulk material. h e exceptional electrochemical properties
