Biology Reference
In-Depth Information
synthetic DNA analogues such as peptide nucleic acids (PNA) are
also discussed. Finally, protein and enzyme mediated biosensors,
nanoparticlebasedsensors,metalionamplifiedsensorsandarange
of miscellaneousmethods is discussed.
7.1 Introduction
Thedeterminationofnucleicacidsequencesforanalyticalpurposes
has remained a strong research focus for years. Effective and
e
cient high-throughput technologies are needed to screen for
genetic defects, identify organisms, and forensic applications. At
present, fluorescence-based techniques are the most commonly
employed. However, wide spread applications of such methods
is limited by low speed, high cost, size, number of incubations
steps, and the need to chemically label the DNA target. In addition,
such systems are far from being foolproof and in some cases false
positives or negatives are observed, making the data interpretation
di
cult. Also, integration of the entire optical system into single
portable device is not simple and requires sophisticated fabrica-
tion processes. In contrast, an electrochemistry-based approach
is promising for point-of-care applications and on-site testing
using portable analyzers. What makes such approach attractive
are its inherent advantages of high speed, low cost, simple
instrumentation, and ease of miniaturization of the biosensing
components.
In recent years, numerous electrochemical DNA detection and
sensing methods have been described in the literature. Most
electrochemical detection schemes involve the immobilization of
an oligonucleotide (ODN) onto a transducer surface. Upon the
hybridization of the complementary target sequence to the capture
strand, the binding event is detected in form of an electrochemical
signal. Methods making use of ODN labeling and label-free methods
have been reported. Labels include the use of redox-modified
oligonucleotides, electroactive DNA intercalators, enzymes, metal
complexes and nanoparticles. On the other hand, label-free
approaches are reported that exploit the intrinsic electroactivity of
the DNA bases (guanine and adenine) or monitor changes in the
interfacial properties of the sensing surface, such as changes in the
