(Ivanhoe Newswire) -- Researchers have developed targeted nanoparticles
that can cling to artery walls and slowly release medicine, an advance that
could provide an alternative to drug-releasing stents in some patients with
cardiovascular disease.
The particles, dubbed "nanoburrs," are coated with tiny protein fragments that
enable them to stick to target proteins and release their drug payload over
several days. Omid Farokhzad, associate professor at Harvard Medical School, is
quoted as saying that the nanoburr is one of the first such particles that can
precisely hone in on damaged vascular tissue. Farokhzad and MIT Institute
Professor Robert Langer, co-authors of the paper, have previously developed
nanoparticles that seek out and destroy tumors.
The nanoburrs are targeted to a specific structure known as the basement
membrane, which lines the arterial walls and is only exposed when the walls are
damaged. The nanoburrs could deliver drugs to treat atherosclerosis and other
inflammatory cardiovascular diseases.
In the current study, the team used paclitaxel, a drug that inhibits cell
division and helps prevent the growth of scar tissue that can clog arteries.
"This is a very exciting example of nanotechnology and cell targeting in action
that I hope will have broad ramifications," Langer was quoted as saying.
The researchers hope the particles will become a complementary approach that can
be used with vascular stents, which are the standard of care for most cases of
clogged and damaged arteries, or in lieu of stents in areas not well suited to
them, such as near a fork in the artery.
The particles, which are spheres 60 nanometers in diameter, consist of three
layers -- an inner core containing a complex of the drug and a polymer chain
called PLA, a middle layer of soybean lecithin, a fatty material, and an outer
coating of a polymer called PEG, which protects the particle as it travels
through the bloodstream.
The drug is released only when it detaches from the PLA polymer chain, which
occurs gradually by a reaction called ester hydrolysis. The longer the polymer
chain, the longer this process takes, so the researchers can control the timing
of the drug's release by altering the chain length. So far, they have achieved
drug release over 12 days in tests in cultured cells.
In tests in rats, the researchers showed that the nanoburrs can be injected
intravenously into the tail and still reach their intended target — damaged
walls of the left carotid artery. The nanoburrs bound to the damaged walls at
twice the rate of non-targeted nanoparticles.
Because the particles can deliver drugs over a longer period of time and can be
injected intravenously, patients would not have to endure repeated and
surgically invasive injections directly into the area that requires treatment,
lead author Juliana Chan was quoted as saying.
The nanoburrs may also prove useful in delivering drugs to tumors.
"This technology could have broad applications across other important diseases,"
said Farokhzad, "including cancer and inflammatory diseases where vascular
permeability or vascular damage is commonly observed."
SOURCE: Proceedings of the National Academy of Sciences, January 18, 2010
