Biomedical Engineering Reference
In-Depth Information
(e.g., quantum-size effect, small-size effect, surface effect) resulted in unique
optical, electronic, magnetic, and catalytic properties of nanomaterials, together
with various approaches available for the preparation and functionalization of
nanoparticles of controlled morphology and surface chemistry, making them ideal
building blocks for signal generation and transduction in sensing [
4
,
5
]. Generally,
two components, target recognition and signal transduction, are major components
for designing any sensor. The target recognition element should have strong affinity,
high specificity, and fast response time for binding a broad range of analytes, while
signal transduction elements are responsible for converting molecular recognition
events into physically or chemically detectable signals [
6
]. Considering the unique
properties of nanomaterials, the integration of natural recognition and biocatalytic
functions of biomolecules with these nano-objects would generate various sensing
systems.
As one of the most important classes of biopolymers, DNA was known only
as a carrier of genetic information for a long time [
7
]. Since the early 1990s,
however, functional DNA molecules (including aptamers and DNAzymes) that
showed binding to a diverse range of analytes with high affinity and speci-
ficity were isolated via a combinatorial biology technique known as in vitro
selection or systematic evolution of ligands by exponential enrichment (SELEX)
[
8
-
14
]. DNAzymes (also called catalytic DNA or deoxyribozymes) are nucleic
acid molecules that can catalyze many chemical and biological reactions in the
presence of specific molecules, mostly metal ions as cofactors. Aptamers, on the
other hand, are DNA molecules that can be considered as nucleic acid analogues
of antibodies; they can specifically bind to a broad range of chemical or biological
molecules, such as small molecules, proteins, viruses, or even cells. In addition to
their ability to specifically bind a broad range of targets, functional DNA offers
a number of advantages over other molecules such as antibodies [
15
,
16
]. For
example, functional DNA molecules are easier to prepare and to modify with
different functional groups, allowing them to be immobilized to different materials.
They are also considered to be nonimmunogenic and stable against denaturation
and biodegradation in clinical applications. Therefore, once functional DNA is
integrated with nanomaterials properly, they can provide new hybrid systems that
combine the specific target recognition properties of functional DNA molecules
with the diverse and strong signal transduction of nanomaterials, making them
ideal candidates as sensors for selective and sensitive detection of a wide range
of analytes [
6
,
17
-
22
]. In this chapter, we will discuss the biosensing applications
of functional DNA based on their combination with different nanomaterials in-
cluding gold nanoparticles, fluorescent nanoparticles, magnetic nanoparticles, and
graphene.
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