Biomedical Engineering Reference
In-Depth Information
nanomaterial characterization were discussed. The instruments include, TEM,
DLS, ATR-FTIR, XPS, Time of Flight SIMS, Colorimetry, AFM, and the Zeta
sizer. 8,9,38,39,46-48,77,83,108,113,115-127 The introduction of the scanning tunneling
microscopy (STM) in the early 1980s allowed the manipulation of individual
atoms, that significantly contributed in the rapid discovery and development of
fullerenes (carbon 60 molecules), CNTs, and semiconductor QDs. 2,10-13,16,18,21-
27,29,31,32,36,37,43,47,75,88,118,119,128-146 At the current status of NMs characterization,
novel high-resolution imaging and analytical tools that will allow easy sample
preparation and in situ monitoring are still needed for a better understanding of
NMs and their interactions with biological systems for medical applications.
9.4 NM s SURFACE MODIFICATION AND
FUNCTIONALIZATION
In Chapter 3, the focus was on the modification and functionalization of NMs.
Most of the commercially available NMs are synthesized in organic sol-
vent. 38,143,147-153 As a result, the products are hydrophobic and are not compat-
ible with biological molecules. In order that the physical, electronic, chemical,
and optical properties of NMs can be exploited to benefit medicine the hydro-
phobic nature has to be converted to hydrophilic state. 2,13,114,131,143,145,154-156
However, at the nanometer scale, the quantum mechanical effects that emerge
leading to various and unexpected physicochemical properties that make them
useful for medical applications may be disrupted during conversion from
hydrophobic to hydrophilic status. In order to harness the novel and unique
properties that can provide promising solutions for nanomedicine, much
care has to be taken in the conversion of organic soluble to water-soluble
NMs. 2,14,17,20,21,26-28,44,69,77,88,124,129,137,145,156-161 Chapter 3 is mainly focused
on the various techniques such as ligand exchange, encapsulation, and poly-
mer coating for the preparation of water-soluble NMs. The water-soluble
NMs that are commercially available contain functional groups making them
easy to manipulate and functionalize with various biomolecules including low
molecular weight drugs for various medical applications. The thiols and other
functional groups that are introduced during conversion into the water-soluble
form and are anchored on the surface of the NMs provide reactive sites for
subsequent bioconjugation reactions. NMs with various functional groups
such as sulfhydryl -SH, carboxyl -COOH, amine -NH 2 , hydroxyl -OH and
others that allows attachment of biomolecules through various bioconjugation
or crosslinking chemistry are now commercially available. Linkers for the
water-soluble NMs are carbodiimide, succinimide, maleidiimide and bifunc-
tional crosslinkers; through direct attachment (hydrophobic or electrostatic
interactions) and sometimes, through the use of the strong biotin-avidin sys-
tem. 114,155,161-166 These various methods of conjugating biomolecules or drugs
to NMs have unique qualities and properties that serve various needs for dif-
ferent applications. 114,155,161-166
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