Biomedical Engineering Reference
In-Depth Information
One of the most important challenges in the medical applications of NMs
is surface modification that allows for biocompatibility and functionaliza-
tion.
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Effec-
tive surface modifications as well as highly controlled surface conjugation
strategies are needed to incorporate specific biomolecules on the surface or inside
the NMs.
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How-
ever, success in functionalization depends on many factors that include NMs size,
shape, charge, chemistry, and surface modification. These factors are often dif-
ficult to vary independently, so the contribution of each is difficult to generalize.
The nanoscale sizes of NMs that approach the atomic level, more often than not,
defy the governing rules at the macroscopic level. Quantum mechanical effects
begin to emerge at the nanoscale dimensions leading to varied and unexpected
physicochemical properties.
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Theoretical calculations, molecular modeling, and indirect methods are fre-
quently employed to investigate the intricate interactions and properties of the
materials at the nanoscale. These novel and unique properties enable nanotech-
nology to provide powerful solutions and alternative to various medical con-
cerns and problems.
The QDs are among the most fascinating NMs that have ever been devel-
oped.
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The core QDs are usually prepared in high-temperature
solvents that involves a mixture of organic chemicals (trioctyl phosphine
and trioctyl phosphine oxide (TOP/TOPO)), followed by a layer of wide-
bandgap semiconductor materials that is coated on the surface of the QD
core creating the shell.
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These QDs
are either used as hydrophobic nanocrystals or are made water-soluble by
ligand exchange or by adsorption of heterofunctional organic coating on the
QD surface that give functionality to the QD surface. These coating materi-
als include thiols, silanes/silanols, bidentate thiols, amine box dendrimers,
oligomeric phosphines, phosphatidyl compounds, amphiphilic saccha-
rides, proteins and peptides, etc.
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In the same man-
ner, other NMs including iron oxide magnetic nanoparticles (IOMNPs) and
other magnetic nanoparticles can be modified like the QDs to make them
biocompatible.
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In addition to the recognition moiety, NMs can be equipped with a coating
that allows membrane transport or easy cell-internalization, and/or an enzymatic
function.
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Peptide or protein coating or amphiphilic
polymer coating produce biocompatible NMs that can penetrate membrane sur-
faces without damaging the cells.
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9.5 NANOBIOSENSORS
NMs have also now been used for biosensors development.
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Biosensors
challenges in medicine include rapid and accurate measurement of molecular
entities such as protein biomarkers, genes, cells, and pathogens in biological
