Biomedical Engineering Reference
In-Depth Information
conjugated to Fe
3
O
4
nanoparticles [69]. These nuclear localization peptide-coated
nanoparticles were introduced into the cell cytoplasm and nuclei, where they
remained monodispersed and nonaggregated.
7.4.2.3
Folic Acid
Folate - conjugated superparamagnetic maghemite nanoparticles have been synthe-
sized for treating solid tumors with intracellular hyperthermia [111]. These ultra-
dispersed nanosystems have been characterized for their physico- chemical
properties and tumor cell-targeting ability, which is facilitated by their surface
modifi cation with folic acid. Preliminary experiments which involved heating
these nanoparticles using an alternating magnetic fi eld at 108 kHz have also been
performed. The nanoparticles' size, surface charge, and colloidal stability have
been assessed for different ionic strengths and varying pH. The ability of the
folate-conjugated maghemite nanoparticles to recognize the folate receptor has
been investigated, both by SPR and in folate receptor-expressing cell lines using
radiolabeled folic acid in competitive binding experiments. The specifi city of
nanoparticle cellular uptake has been further investigated using TEM, after incu-
bation of these nanoparticles in the presence of three cell lines with different folate
receptor expression levels. Both, qualitative and quantitative determinations of
folate nanoparticles and nontargeted control nanoparticles have demonstrated a
specifi c cell internalization of the folate superparamagnetic nanoparticles [111].
7.4.3
Laser - Induced Hyperthermia/Thermal Ablation Therapy
Another method of site-specifi c cancer cell destruction is that of laser-induced
hyperthermia or “ablation therapy”, which utilizes the absorption of nanoparticles
in the NIR region. When light is absorbed, it is converted by the nanoparticles
into heat, which in turn destroys the cancer cells. Because of its weak absorption
by tissues, NIR light can penetrate more deeply into the skin, but without causing
much damage to normal tissues; thus, it can be used in conjunction with nano-
materials to target specifi c cell types.
Recently, details of the synthesis and characterization of an SPIO@Au nanoshell
for NIR laser-induced photothermal ablation therapy were published [46, 116]
(details of this synthesis are provided in Section 7.2.2.2.3). The SPIO@Au
nanoshells have a strong absorption at 700-800 nm, and laser-induced hyperther-
mia experiments in solution have resulted in an increase in temperature of 16 ° C
at a particle concentration of 7.5
1 0
12
m l
− 1
when irradiated with an 810 nm con-
tinuous-wave diode laser at 1 W for 15 min. This increase in temperature was also
seen to be concentration-dependent [46]. Moreover, because the SPIO@Au
nanoshells exhibited a high transverse relaxivity,
r
2
, and a large
r
2
/
r
1
ratio, they
could be imaged using MRI to obtain T
2
-weighted images. Experiments on the
heat-generating capacity of SPIO@Au nanoshells under an alternating magnetic
fi eld could be used with these nanoparticles to mediate thermal ablation, which
makes it possible to treat both deep and superfi cial cancer lesions. Given their
×
