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�Using this system, drugs could be released slowly and under control
for weeks or longer,� said Cheng, a professor of microbiology,
immunology and molecular genetics. �A drug that is given orally or
through the bloodstream travels throughout the system and dissipates
from the body much more quickly. Using a more localized and controlled
approach could limit side effects, particularly with chemotherapy
drugs.�
Researchers coated tiny chips with layers of the nanoscale polymer
films, which are inert and helped provide a Harry Potter-like
invisibility cloak for the chips, hiding them from the body�s natural
defenses. They then added Dexamethasone, an anti-inflammatory drug,
between the layers. The chips were implanted in mice, and researchers
found that the Dexamethasone-coated films suppressed the expression of
cytokines, proteins released by the cells of the immune system to
initiate a response to a foreign invader. Mice without implants and
those with uncoated implants were studied to compare immune response.
The uncoated implants generated an inflammatory response from the
surrounding tissue, which ultimately would have led to the body�s
rejection of the implant and the breakdown of its functionality.
However, tissue from the mice without implants and the mice with the
nano-cloaked implants were virtually identical, proving that the
film-coated implants were effectively shielded from the body�s defense
system, said Edward Chow, a former UCLA graduate student who
participated in the study and is one of its authors.
�The polymer films provided a cloak of invisibility for the implants,
keeping the immune system from attacking,� Chow said.
The nanomaterial technology serves as a non-invasive and biocompatible
platform for the delivery of a broad range of therapeutics, said Dean
Ho, an assistant professor of biomedical and mechanical engineering
with the McCormick School of Engineering and Applied Science, a member
of the Robert H. Lurie Comprehensive Cancer Center of Northwestern
University and the study�s senior author.
The technology also may prove to be an effective approach for
delivering multiple drugs, controlling the sequence of multi-drug
delivery strategies and enhancing the life spans of commonly implanted
devises such as cardiac stents, pacemakers and continuous glucose
monitors.
�For chemotherapy, this system could enhance treatment efficacy while
preventing uncontrolled delivery and the resultant patient side
effects,� Ho said. �Furthermore, as implantable devices continue to
find widespread application in cardiovascular medicine, neural
disorders and diabetes, the nano-cloaking capabilities can serve as a
widely applicable approach to enhance the lifetime of these devices.
This would eliminate unnecessary surgeries and enhance the efficiency
of patient care.�
Many cancer drugs, chemotherapies for example, are delivered
systemically through the blood stream. The drugs attack cancer cells,
but also other fast growing cells causing side effects such as anemia,
nausea and hair loss. If the chemotherapy could be delivered by
implant directly to the tumor site, such side effects would be limited,
said Cheng, who also is a member of the Center for Cell Control at the
UCLA Henry Samueli School of Engineering and Applied Sciences.
�Say you have a localized cancer such as breast cancer, the drugs we
give are not directly targeted to the breast,� Cheng said. �If we
could apply the treatment locally and control the release of the drugs,
the therapy might be more effective in treating the cancer.�
Chemotherapy drugs could potentially be placed in high concentration
between the polymer films and an implant placed at the tumor site. The
drugs would be released slowly, over time, delivering more of the
toxic chemicals directly to the cancer cells.
This study provided the proof of principle that implants in animal
models could be coated with materials that made them invisible to the
immune system. Cheng and Ho are now testing in animal models whether
cancer therapies can be effectively and safely administered and
locally delivered using the nanomaterials.
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