MIT: Nanotech targets and kills cancerous tumors

Sharon Gaudin
07.05.2009 kl 18:45 | IDG News Service

Scientists have long known that heat is an effective weapon against cancerous tumors. The problem, though, has been how to heat the tumors to the point that it kills them without damaging surrounding tissue.

Scientists have long known that heat is an effective weapon against cancerous tumors. The problem, though, has been how to heat the tumors to the point that it kills them without damaging surrounding tissue.

Now researchers MIT think they have the answer: nanotechnology.

The school announced this week that the researchers have developed gold nanoparticles that can target tumors and heat them with minimal side effects to nearby healthy cells. While the gold nanorods were used in the study to find and hone in on tumors, they also might be able to diagnose cancer, according to MIT graduate student Geoffrey von Maltzahn, who worked with Sangeeta Bhatia, a professor in the Harvard-MIT Division of Health Sciences and Technology, to develop the nanoparticles.

The researchers said that tumors in mice that received the nanorod treatment disappeared within 15 days. The cancer did not reoccur for the duration of the three-month study.

This news comes just months after MIT announced that a group of scientists there had developed nanotechnology that can be placed inside living cells to determine whether chemotherapy drugs used to treat cancer are reaching their targets or attacking healthy cells. Researchers use carbon nanotubes wrapped in DNA so they can be safely injected into living tissue.

And last August, scientists at Stanford University reported that they had found a way to use nanotechnology to have chemotherapy drugs target only cancer cells, keeping healthy tissue safe from the treatment's toxic effects.

And that news came on the heels of a report out last July noting that researchers at the University of California, San Diego, had discovered a way to use nanotechnology-based "smart bombs" to send lower doses of chemotherapy to cancerous tumors, thus cutting down the cancer's ability to spread throughout the body.

Cancer researchers have long been trying to figure out a way to better attack cancer cells without harming surrounding cells as well. That has been one of the major drawbacks of chemotheraphy and radiation therapy, which often have debilitating side effects because of the difficulty in targeting just the cancerous tissue.

According to MIT, cancer affects about 7 million people a year worldwide, and that number is projected to jump to 15 million by 2020. Most of those patients are treated with chemotherapy and/or radiation and 99% of those drugs typically don't reach the tumor, said von Maltzahn.

He added that their work with the gold nanorods is the "most efficient method" in targeting tumors yet developed.

The nanoparticles work in this cancer treatment by absorbing light at near-infrared frequency. The light heats the rods but passes harmlessly through human tissue, said von Maltzahn. The nanoparticles accumulate in the tumors, and within three days, the liver and spleen clear any that don't reach the tumor.

The mice that were treated in the MIT study received an injection of the gold nanorods along with near-infrared laser treatment. With this combination therapy, the tumors disappeared and did not return in the duration of the scientists' research.

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Hollow gold nanospheres show promise for biomedical and other applications

Public release date: 22-Mar-2009

Contact: Tim Stephens
stephens@ucsc.edu
831-459-2495
University of California - Santa Cruz

SALT LAKE CITY, UT--A new metal nanostructure developed by researchers at the University of California, Santa Cruz, has already shown promise in cancer therapy studies and could be used for chemical and biological sensors and other applications as well.

The hollow gold nanospheres developed in the laboratory of Jin Zhang, a professor of chemistry and biochemistry at UCSC, have a unique set of properties, including strong, narrow, and tunable absorption of light. Zhang is collaborating with researchers at the University of Texas M. D. Anderson Cancer Center, who have used the new nanostructures to target tumors for photothermal cancer therapy. They reported good results from preclinical studies earlier this year (Clinical Cancer Research, February 1, 2009).

Zhang will describe his lab's work on the hollow gold nanospheres in a talk on Sunday, March 22, at the annual meeting of the American Chemical Society in Salt Lake City.

"What makes this structure special is the combination of the spherical shape, the small size, and the strong absorption in visible and near infrared light," Zhang said. "The absorption is not only strong, it is also narrow and tunable. All of these properties are important for cancer treatment."

Zhang's lab is able to control the synthesis of the hollow gold nanospheres to produce particles with consistent size and optical properties. The hollow particles can be made in sizes ranging from 20 to 70 nanometers in diameter, which is an ideal range for biological applications that require particles to be incorporated into living cells. The optical properties can be tuned by varying the particle size and wall thickness.

In the cancer studies, led by Chun Li of the M. D. Anderson Cancer Center, researchers attached a short peptide to the nanospheres that enabled the particles to bind to tumor cells. After injecting the nanospheres into mice with melanoma, the researchers irradiated the animals' tumors with near-infrared light from a laser, heating the gold nanospheres and selectively killing the cancer cells to which the particles were bound.

Cancer therapy was not the goal, however, when Zhang's lab began working several years ago on the synthesis and characterization of hollow gold nanospheres. Zhang has studied a wide range of metal nanostructures to optimize their properties for surface-enhanced Raman scattering (SERS). SERS is a powerful optical technique that can be used for sensitive detection of biological molecules and other applications.

Adam Schwartzberg, then a graduate student in Zhang's lab at UCSC, initially set out to reproduce work reported by Chinese researchers in 2005. In the process, he perfected the synthesis of the hollow gold nanospheres, then demonstrated and characterized their SERS activity.

"This process is able to produce SERS-active nanoparticles that are significantly smaller than traditional nanoparticle structures used for SERS, providing a sensor element that can be more easily incorporated into cells for localized intracellular measurements," Schwartzberg, now at UC Berkeley, reported in a 2006 paper published in Analytical Chemistry.

The collaboration with Li began when Zhang heard him speak at a conference about using solid nanoparticles for photothermal cancer therapy. Zhang immediately saw the advantages of the hollow gold nanospheres for this technique. Li uses near-infrared light in the procedure because it provides good tissue penetration. But the solid gold nanoparticles he was using do not absorb near-infrared light efficiently. Zhang told Li he could synthesize hollow gold nanospheres that absorb light most efficiently at precisely the wavelength (800 nanometers) emitted by Li's near-infrared laser.

"The heat that kills the cancer cells depends on light absorption by the metal nanoparticles, so more efficient absorption of the light is better," Zhang said. "The hollow gold nanospheres were 50 times more effective than solid gold nanoparticles for light absorption in the near-infrared."

Zhang's group has been exploring other nanostructures that can be synthesized using the same techniques. For example, graduate student Tammy Olson has designed hollow double-nanoshell structures of gold and silver, which show enhanced SERS activities compared to the hollow gold nanospheres.

The ability to tune the optical properties of the hollow nanospheres makes them highly versatile, Zhang said. "It is a unique structure that offers true advantages over other nanostructures, so it has a lot of potential," he said.

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