Biomedical Engineering Reference
In-Depth Information
for the detection and differentiation of three different virus RNAs (such as
adenovirus, rhinovirus, and HIV RNA).
127
OAD has been used to fabricate a
microwell-arrayed SERS chip on glass
252
that provided a uniform Raman signal
enhancement from well to well with a detection limit of 10
−8
M for the Raman
active molecule—1,2-di(4-pyridyl)ethylene solution. This system has been
used for biosensor development using avian influenza virus as model ananlyte.
A similar method called oblique angle polymerization was used for the prepara-
tion of SERS substrates.
253
Nanostructured poly(chloro-
p
-xylelene) was used
as template for the electroless deposition of Ag or Au that led to reproducible
SERS signal for the detection of RSV.
Aside from containing a recognition moiety, NMs can be equipped with a
coating that allows membrane transport or cell-internalization capability, and/or
an enzymatic function. The natural peptide coating or the amphiphilic coating
approach produces biocompatible NMs that can penetrate membrane surfaces
without damaging the cells.
3.5 CONCLUSIONS
The physical, electronic, chemical, and optical properties of NMs are being
exploited to benefit biomolecules that are useful in medicine. At the nanometer
scale, quantum mechanical effects emerge leading to varied and unexpected
physicochemical properties that make them useful for biosensor applications
that provide solutions to the problems of existing methods. The novel and
unique properties enable nanotechnology to provide promising solutions for
nanomedicine.
The NMs that have been exploited in medicine are usually produced in
organic solvents making them hydrophobic and incompatible to biological
molecules. Alongside the organic synthesis of NMs, conversion methods into
the water-soluble form to make them biocompatible have also emerged. Vari-
ous techniques such as ligand exchange, encapsulation, and polymer coating
have been developed and used in the preparation of water-soluble NMs. The
water-soluble NMs that are now currently commercially available contain
functional groups on their surfaces making them easy to manipulate for vari-
ous medical applications. Functional groups anchored to the surface of NMs
during synthesis or modification into their water-soluble forms provide reactive
sites for subsequent bioconjugation reactions. These functional groups often
involve sulfhydryl -SH, carboxyl -COOH, amine -NH
2
, hydroxyl -OH, and
others that allow attachment of biomolecules through various bioconjugation or
cross-linking chemistry. Linkers for these NMs are carbodiimide, succinimide,
maleimide, and bifunctional cross-linkers through direct attachment (hydropho-
bic or electrostatic interactions) and sometimes, through biodin-avidin system.
These various methods have their unique qualities and applications along with
inherent disadvantages such as possible low yield and loss of functionality after
conjugation which researchers are actively studying to solve and improve.
