Washington, D.C.August 31, 2005 --- Stealth nano particles may some day
target tumor cells and deliver medication to specific body locations,
according to Penn State chemical engineers.
"Mainly we have focused on chemotherapy drugs," says Dr. Michael Pishko, professor
of chemical engineering and materials science and engineering. "But others are
considering using this delivery system to deliver genes in gene therapy."
The researchers first produce nano-sized powders of the drug they wish to deliver
and encapsulate them in a polymer nanoshell. The drug used for this project
was paclitaxel - an anti breast cancer drug and dexamethasone - a
steroid frequently used to treat eye inflammation. This shell allows the drug
to travel in stealth mode through the bloodstream.
"A layer-by-layer self-assembly technique was used to encapsulate core charged
drug nanoparticles in a polymeric nanoshell," the researchers told attendees
today (Aug. 31) at the 230th American Chemical Society Meeting, Washington, D.C.
Normally, drugs, especially the toxic drugs used for chemotherapy, trigger
the human immune system into action, but, with the polymer shell for protection,
these drugs can circulate longer without being removed.
"If the drugs do not trigger an immune response, then lower levels of drug can
be used than currently are necessary in chemotherapy," says Pishko.
The researchers, who include Pishko, Alisar Zahr and Cheryl A. Rumbarger, graduate
students in chemical engineering, tested their nanoshell in cell culture and
found that it had less phagocytosis removal of the drug during
a 24-hour period than the unencapsulated drug.
Combined with longer retention in the body, the researchers engineered the
nanoparticle shells to target specific cells by attaching a functionalized
polymer to the shell. They designed this tentacle-like projection to target
a receptor on a tumor cell, or a specific location in the eye, for example.
Once the drug arrives via the blood to the tumor or eye, it attaches and slowly
releases its contents.
This type of drug delivery system works especially well in such highly vascularized
areas such as tumors and the eye, because the drug can travel right up to the
target area. Delivery to areas in the brain would not be feasible because of
the blood brain barrier that prevents foreign substances from moving from the
blood into the cells of the brain.
"For targeting, we could exploit the fact that cancer tumors have a lot more
folic acid receptors and target those," says Pishko. "We could also use specific
monoclonal antibodies to target specific tumors."
The researchers also considered delivery of drugs to specific type cells, like
those in the eye. This type of stealth targeting drug delivery system could
also deliver genes or gene fragments in gene therapy.
The National Science Foundation funded this research.
A'ndrea Elyse Messer
Science & Research Information Officer Penn State