Biomedical Engineering Reference
In-Depth Information
receptors (EGFR) using Quantum dot (Qdot) luminescence and confocal microscopy showed that
SWNT-Qdot-EGF bioconjugates internalized rapidly into the cancer cells. Limited uptake occurred
for control cells without EGF. Intravital video imaging
in vivo
showed that SWNT-Qdot-EGF
injected into live mice was selectively taken up by HNSCC tumors, but SWNT-Qdot controls with no
EGF were cleared from the tumor region in
20 min. The HNSCC cells treated with SWNT-cispla-
tin-EGF were also killed selectively, while control systems that did not feature EGF-EGFR binding
did not influence cell proliferation. Most significantly, regression of tumor growth was rapid in mice
treated with targeted SWNT-cisplatin-EGF relative to nontargeted SWNT-cisplatin.
Photodynamic therapy is a type of cancer treatment that uses a drug called a photosensitizer or
photosensitizing agent. Photosensitizer is activated by light of a specific wavelength. When photosen-
sitizers are exposed to this specific wavelength, they produce singlet oxygen, which destroys cancer
cells. Photothermal cancer therapy is based on generating local hyperthermia by infrared (IR) laser to
destroy tumor cells. SWNTs with strong optical absorption in the broad visible and NIR offer unique
advantages for photothermal cancer therapy. A broad range of wavelengths can be used for the treat-
ment with SWNTs, whereas conventional photothermal therapeutic agent is designed to absorb light
only near one selected wavelength. In a recent study
[66]
, SWNTs were injected into the tumor tissue
and it was evaluated whether local hyperthermia could destroy tumor cells. SCC tumor in mice was
exposed to 785-nm laser after intratumoral injection of SWNTs with different light and SWNTs-dose
combinations. The temperatures of the tumor with laser irradiation were monitored.
In vivo
and
ex
vivo
Raman spectra in different organs were obtained with a rapid Raman system. Tumor responses
(tumor volume and mouse survival) were documented daily after treatment up to day 45 to assess the
effectiveness of the treatment. The temperature within the tumors increased in a light- and SWNTs-
dose dependent manner. The study concluded that SCCs can be eradicated at a moderate light irra-
diance and fluence (200 mW cm
2
and 120 J cm
2
). This light dose is also comparable to those
used with photodynamic therapy. Tissue Raman spectroscopy measurements revealed that SWNTs
remained localized in the tumor even 3 months after injection but was not found in other organs. The
result of this study represents a significant step forward toward the goal of advancing SWNTs-based
photothermal cancer therapy into clinical applications for treatment of oral cancer and other tumors.
20.5
CONCLUSIONS
CNTs are potentially promising needle-like carriers of small drug molecules as well as macromolecules
such as gene and protein. CNTs can be functionalized so that certain molecules are attached to their
surfaces via covalent or noncovalent bonding. The needle-like shape of the CNTs enables them to per-
forate cellular membranes and transport the carried therapeutic molecules to the cellular components.
This process is thought to take place via endocytosis. CNTs have exclusive properties that would make
them appropriate in the medical field such as their ability to adsorb pathogenic microorganisms and con-
duct heat. It is interesting that huge amount of medical research of CNTs has taken place in the area of
anticancer therapy at the expense of other areas. From the perspective of the authors of this review, this
might be due to the potential toxicity of CNTs as well as the established safety of the vesicle nanocarri-
ers (e.g., liposomes) which was out of the scope of discussion of this paper. CNTs have been introduced
to drug delivery research for a limited number of years and therefore extensive amounts of research is
expected to be produced in the forthcoming years in order to explore their potential.
