Biomedical Engineering Reference
In-Depth Information
specific functional groups and are, therefore, not useful for simple conjugation
techniques, such as avidin-biotin binding. Additional studies were reported
24,97
on the design and synthesis of ligands functionalized with a biotin end group.
These ligands had a central TEG segment, a dithiol terminal group for anchor-
ing on the QD surface, and a lateral biotin. The presence of biotin at one end
was expected to allow avidin-biotin binding motif to conjugate QDs to pro-
teins and other biomolecules via the avidin surface. Their cap exchange reac-
tions involved mixed ligands that resulted in binding assays of the biotin-coated
water-soluble QDs to NeutrAvidin-functionalized substrates that exhibited spe-
cific capture of the QDs through avidin-biotin interactions.
The nanoscale dimensions of NMs bring optical, electronic, magnetic, cata-
lytic, and other properties that are distinct from those of atoms/molecules or
bulk materials. In order to exploit the special properties that arise due to the
nanoscale dimensions of NMs, researchers must control and manipulate the
size, shape, and surface functional groups and structure them into periodi-
cally ordered assemblies to create new products, devices, and technologies or
improve existing ones.
112-119
The art of controlling/manipulating the properties
and utilizing these NMs for the purpose of building microscopic machinery
can be done using the “top-down” or “bottom-up” approach. In the “top-down”
approach, large chunks of materials are broken down into nanostructures by
lithography or any other outside force that imposes order on NMs.
120
The
“bottom-up” approach follows nature's lead in making extraordinary materials
and molecular machines by building nanostructures from atoms or molecules
or any stable building blocks through the understanding and exploitation of
order-inducing factors that are inherent in the system.
121
The mechanism of for-
mation/fabrication of novel nanostructures from self-assembly of peptides, pro-
teins, and lipids has been elucidated as described in a review article by Zhang
121
providing an understanding of the factors that govern growth and ordering of
NMs that has led to a number of novel structures and functionalities. These
nanostructures include nanofibers, bionanotubes, amphiphilic protein scaffolds,
and nanowires that have potential applications in the electronic industry, bio-
medical field, computer information technology, etc.
The application of NMs in medicine is rapidly gaining ground in the field
of medical diagnostics.
122
Driskell and Tripp
103
and Kaittanis et al.
123
discussed
the different strategies for different disease diagnostics and how nanotechnol-
ogy can revolutionize these strategies. Lee et al.
124
reviewed recent advances in
nano/microfluidic technologies for clinical point-of-care (POC) applications at
resource-limited settings in developing countries. Hauck et al.
125
described the use
of NMs as labels or barcodes in conjunction with microfluidic systems for auto-
mated sample preparation and sample assays for infectious diseases diagnostics.
One of the applications of NMs that rely almost completely on the function-
alization of the NM is a biosensor. A biosensor is composed of a biorecogni-
tion element that interacts with the target molecules and a transducer and detects
the interaction and converts the binding event to a measurable analytical signal.
