Researchers use nanotech to target chemo cancer treatment

Nanotubes work way into tumor walls to drop off drugs, cutting chemo's affect on healthy cells

University researchers have found a way to use nanotechnology to have chemotherapy drugs target only cancer cells, keeping healthy tissue safe from the treatment's toxic effects.

Cancer researchers have been trying to figure out a way to better deliver drugs, like chemotherapy, to cancer cells without blasting surrounding cells as well. Last week, scientists at Stanford University in Palo Alto, Calif., devised a way to use single-walled carbon nanotubes as targeted medicinal delivery vehicles.

By better targeting the chemo, less of the drug needs to be injected into the patient for treatment of cancer. And that would reduce the side effects of chemotherapy treatment, such as nausea, hair loss, weight loss and fatigue.

"That means you will also have less drug reaching the normal tissue," said Stanford chemistry professor Hongjie Dai, in a statement.

The Stanford effort is just one of many projects under way aiming to better target toxic chemotherapy drugs.

Last month, researchers at the University of California, San Diego, announced the discovery of a way to use nanotechnology-based "smart bombs" to send lower doses of chemotherapy to cancerous tumors, cutting down on the cancer's ability to spread throughout the body.

The new UCSD treatment strategy focuses on halting the ability of pancreatic and kidney cancers to metastasize. The treatment also appears to cause less damage to surrounding tissue than traditional chemotherapy, according to the university.

The university's treatment plan uses a nanoparticle, carrying a payload of chemotherapy, to target a protein marker found on the surface of certain blood vessels associated with malignant tumor growth. Metastasis is more reliant on new blood vessel growth than established tumors are. While the treatment didn't have a dramatic effect on the primary tumor, studies using mice showed it did stop pancreatic and kidney cancers from metastasizing.

The Stanford University researchers noted that the nanotubes let them get up to 10 times as much medication into the tumor cells. Scientists reported that after 22 days of treatment, tumors in mice treated with the nanotubes were, on average, less than half the size of the mice that were treated traditionally.

The Stanford researchers noted that the nanotubes were coated with polyethylene glycol (PEG), a common ingredient in cosmetics. The PEG compound has three little branches sprouting from a central trunk. They squeezed the trunks into the nanotubes so the branches still stuck out. Researchers attached the chemotherapy drug to the tips of those branches.

According to a paper published by the Stanford group, the size and surface structure of the nanotubes are critical factors in how well they interact with blood vessel walls. Researchers noted that blood vessels in tumors have relatively leaky walls, which offer openings for the nanotubes to slip through. Scientists said they could adjust the length and size of the nanotubes so they are too large to get through holes in the walls of normal blood vessels, but small enough to make their way through the larger holes in the tumor tissue.

"That enabled the nanotubes to deliver their medicinal payload with tremendous efficiency, throwing a therapeutic wrench into the cellular means of reproduction and thus squelching the hitherto unrestrained proliferation of the tumor cells," the university noted in the report.

Dai said they are working on a more active targeting system, which would include attaching a peptide or antibody to the drug in the nanotube. That peptide or antibody would specifically bind itself to the tumor.

The university did not give a time frame on when the treatment might become available.

Copyright © 2008 IDG Communications, Inc.

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