The tiniest of carriers, called nanoparticles, can make a beeline to cancer cells, taking medicine with them.
From nanocrystal TV screens that offer brighter, sharper pictures to nanosilver antibacterial coatings that keep your socks from smelling, science is continually finding new ways to work with materials at the miniscule level.
In cancer treatment, a big stumbling block has been finding ways to transport chemotherapy drugs to cancer cells while sparing the rest of the body. Nanoparticles could be the answer here, too.
“Most drugs can’t differentiate between cancer and normal cells, so the drug goes everywhere and kills other healthy cells,” says Greg Troiano, who works with nanomedicine product development at Pfizer's Pearl River, New York site. “We’re trying to get more drug to the disease, its tissue and cells, and less drug everywhere else.”
Nanoparticles — so tiny that you can fit about one million of them in a single cell — can act as drug carriers that can seek out and bind to disease cells and release medicines directly into them at a controlled rate. Troiano and his colleagues are studying the potential for biodegradable plastic nanoparticles to deliver drugs for a variety of conditions from cancer to inflammatory diseases. Other researchers around the globe are looking at different materials for nanoparticle drug delivery, such as gold.
These tiny particles, with maximized surface area for more binding, can do tasks in the body that larger particles can’t. Larger particles are quickly captured and eliminated by the body’s immune system. But these tiny carriers can slip past the body’s immune security and make their way into the capillaries and pores of diseased tissue, such as tumors. If they evade the immune system, so does the medicine they are carrying with them.
Honing in on its Target
Nanoparticles are drug carriers on a mission. The surface of each nanoparticle is affixed with special molecules that recognize diseased cells like a key in a lock, and then help it stick there as the medicine is slowly released. Some of these surface molecules will actually guide the nanoparticle into the rogue cells.
Made from a biodegradable polyester polymer, the same material used in dissolving stitches, these nanoparticles also have the unique ability to hold a relatively massive amount of medicine — up to 10,000 molecules per particle — which increases its disease-fighting abilities, while limiting the total number of nanoparticles needed. “Our particle can be used across a wide range of drugs, and be used with very different quantities of drugs,” said Young-Ho Song, a Pfizer researcher in Pearl River, who specializes in studying how to formulate nanoparticles with drugs.
A “Salad Dressing” Mixture
Their nanoparticles are made by dissolving the polyester material, the drug and some other key ingredients in an oil and shaking it up like a salad dressing or an emulsion — a mixture of ingredients that normally wouldn’t combine, according to Song. That mixture is then put under thousands of pounds of pressure, which breaks downs into nano-sized droplets. After removing the dissolving liquids, each droplet is hardened into a microscopic plastic polymer shell, encasing a medicine core. A single dose of medicine contains about a quadrillion (1015) nanoparticles!
The nanoparticles are delivered intravenously, stay in the body for a few weeks, and the broken-down components are eliminated through urination. Nanoparticles typically release their medicines over a few days.
So far this polyester polymer technology has been studied in cancer, cardiovascular, anti-inflammatory, and anti-infective applications, said Troiano. The challenge going forward is finding the right drug to pair with this nanotechnology to be tested in clinical studies. But scientists so far don’t see a limit for how far these particles could go.