Biomedical Engineering Reference
In-Depth Information
In a study involving rabbits with malignant kidney tumors, SPIONs using
CT guided placement were implanted
218
which were later exposed to an alter-
nating electromagnetic field (0.32 kA/m) for 15 min. The tumor necrosis was
verified with CT perfusion imaging and histological evaluation. They also stud-
ied the effect of a single injection of SPIONs (8-10 nm) compared with con-
tinuous infusion during exposure to the magnetic field.
220
They showed that
continuous infusion of SPIONs resulted in a larger zone of necrosis compared
with the single injection, but, non-uniform ferrofluid distribution led to highly
variable size coagulation necrosis.
220
Studies involving AuNPs and nanoshells that can be remotely activated by
near infrared light (NIR, 650-950 nm) are very interesting because they are
generally biocompatible and biologically non-toxic.
221,222
The application of
molecular targeting using AuNOs to cancer cells to create RF induced hyper-
thermic cytotoxicity has several advantages that include 1) low cost and ease
of production; 2) optical absorption for characterization; 3) active manipula-
tion of surface chemistry with respect to charge and shape; 4) straight forward
attachment of targeting molecules, such as antibodies, nucleotides, peptides, or
pharmacologic agents; and 5) small size (5-10 nm diameter) diameter can effec-
tively penetrate through pores and fenestrations in the neovasculature of solid
tumors.
223
Having these properties, targeted AuNPs easily access the surface of
cancer cells and bind to target receptors. This is followed by internalization into
the cytoplasm of the cells
224
and activation by remote RF energy to release suf-
ficient heat to produce thermal cytotoxicity in the cancer cells.
3
AuNPs present
the added advantage of current clinical use to treat some patients with severe
rheumatoid arthritis and is known to have a low toxicity profile. Gold coated
nanoshells with silica core offer versatility in that they can absorb in the NIR
region for selective ablation
225,226
causing 100% regression of tumors after pho-
tothermal treatment. With the use of the non-targeted nanoshells, these are pas-
sively localized in the tumor based on EPR mechanism.
3
Tissue thermal ablation using NMs that are functionalized to serve as specific
thermal agents, offer great potential for the treatment of unresectable tumors
with which can be personalized based on the recognition molecule attached to
the particle surface. After intravenous administration the targeted NMs, in an
ideal situation, they will be capable of navigating into the vasculature to reach
the desired site at full concentration and to selectively kill the cancer cells with
energy that is applied from a remote source. These kinds of pharmacological
agents are much needed to improve cancer therapeutics. Enormous research are
currently making progress toward partially achieving this goal in the very near
future.
7.5.2 Thermal Ablation and NMs Combination Therapeutics
The limitations of thermal ablation discussed in the previous section, com-
bined with the development and availability of chemotherapeutic drugs that
