Biomedical Engineering Reference
In-Depth Information
for drug release and micromachined hollow needles and two-dimensional
needle arrays from single crystal silicon); sensors and laboratory diag-
nostics. h e delivery and targeting of pharmaceutical, therapeutic, and
diagnostic agents via intravenous and interstitial routes of administration
with nanosized particles in nanomedicine are very immense, including
the advantage of the nanometer scale size range, biological behavior, and
safety proi le. Nanoparticles have a much larger surface area per unit mass
as compared with larger particles. h e increase in the surface-to-volume
ratio results in an increase of the particle surface energy (due to quan-
tum ef ect), and becomes more reactive in the behavior shown in the anti-
oxidant activity, carrier capacity for therapeutics, penetration of cellular
barriers for drug delivery, toxicity, induction of oxidative stress or of cel-
lular dysfunction, or a mix of both. Nanoparticles of silver and gold dis-
play antimicrobial properties which help to prevent infection and wound
healing. Nanocrystal silver burn cream, and nanocrystal shoes and athletic
equipment are becoming popular. Sunscreens containing nanoparticles of
zinc oxide or titanium dioxide are currently in use. Colloidal gold/Ag/Cu,
zinc oxide, iron oxide crystals, and semiconductor quantum dots (QDs) or
nanocrystals in the size range of 1-20 nm have diagnostic applications in
biology and medicine. Gold nanoparticles have application as quenchers
in l uorescence resonance energy transfer measurement studies. For exam-
ple, the distance-dependent optical property of gold nanoparticles has
provided opportunities for evaluation of the binding of DNA-conjugated
gold nanoparticles to a complementary RNA sequence. Iron oxide nano-
crystals with superparamagnetic properties are used as contrast agents in
magnetic resonance imaging (MRI), as they cause changes in the spin-spin
relaxation times of neighboring water molecules, to monitor gene expres-
sion or detect pathologies such as cancer, brain inl ammation, arthritis, or
atherosclerotic plaques. h e QDs can label biological systems for detec-
tion by optical or electrical means
in vitro
and to some extent
in vivo
. h e
l uorescence emission wavelength (from the UV to the near-IR) of QDs
can be tuned by altering the particle size, thus these nanosystems have
the potential to revolutionize cell, receptor, antigen, and enzyme imag-
ing. h eir large surface-area-to-volume ratio of ers potential for designing
multifunctional nanosystems.
Nanoparticle forms the core of nanobiomaterial, nanovesicle surrounded
by a membrane or a layer. h e shape is more ot en spherical but cylindri-
cal, plate-like and other shapes are possible. h e size and size distribution
might be important in some cases, for example, if penetration through a
pore structure of a cellular membrane is required. h e size and size distri-
bution become extremely critical when quantum-sized ef ects are used to
