Israeli Physicist Uses Gold to Help Detect Cancer Early

Nanotech-based method, which recently proved itself during its first tests on humans, aims to enable cancer diagnosis.

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Illustration: Gold
Illustration: GoldCredit: Bloomberg

Israel’s conflict with Hamas was not the ideal backdrop for a lecture by an Israeli scientist outside Israel, but the British House of Lords did not consider canceling a lecture by Professor Dror Fixler of Bar-Ilan University. Still, the military operation wasn’t completely absent from the scene: One of the members queried British Prime Minister David Cameron about what was going on in the Gaza Strip. “Cameron was not present, but his representative, who was present, faithfully expressed Israel’s position and defined Hamas as a terrorist organization,” Fixler said.

Fixler wasn’t asked to speak on the topic; he was there for a completely different reason. A project he heads offers a new cancer-diagnosis method that has aroused interest in the scientific community, particularly in the U.K. Last June, the Academy of Medical Sciences in London awarded Fixler a Lord Turnberg Fellowship, and over the next year he’ll be continuing his research with other scientists at King’s College in London.

Quite a bit of current cancer research concerns effective and rapid diagnosis of various types of cancer based on the belief that early diagnosis increases a patient’s chances of survival.

The method Fixler developed can be described simply: A person goes to the doctor with pain and other symptoms in his oral cavity. One of the less pleasant possibilities is that the patient is suffering from cancer of the mouth, tongue or larynx. The physician asks the patient to gargle using a special mixture, and within minutes the doctor can confirm or rule out a diagnosis of cancer. The method has been tested successfully on animals and recently proved itself during its first tests on humans.

Fixler leads a group of scientists at the Institute of Nanotechnology and Advanced Materials at Bar-Ilan University. The development they have been working on for five years has provided further proof of the importance of nanotechnology and materials-engineering departments, where researchers in biology, chemistry and physics join forces in research institutes in Israel and worldwide.

With his colleagues, Fixler has developed an optical system that is non-invasive and involves no exposure to radiation. It has been used to detect cancer of the head, neck and oral cavities in animals. It can be used to detect cancerous growths on the tongue, throat and larynx.

From the patients’ perspective, the test is simple. They gargle for several minutes using a mixture that includes nanoparticles of gold. The particles effectively paint the cancer cells. The area is then scanned with a specially developed tool and the physician views the results on a computer screen.

In current clinical trials, the method has successfully detected cancer on the tongues and larynxes of humans. The trials for diagnosing cancer of the larynx based on this method are being conducted at the Department of Otolaryngology at Sheba Medical Center, Tel Hashomer, under the direction of Prof. Michael Wolf. A trial to diagnose cancer of the tongue using this method was conducted at the clinic of Professor Avraham Hirshberg of the School of Dental Medicine at Tel Aviv University.

“It’s not considered a scientific or medical gold standard yet because we compare the results that we receive with the results of the patient’s biopsy, but we’ve had a success rate of more than 90 percent,” Fixler says.

Fixler, 44, a physicist born in Tel Aviv, is the head of the Advanced Light Microscopy Laboratory at Bar-Ilan University. He earned his bachelor’s degree and Ph.D. in physics at Bar-Ilan University and his master’s at the Weizmann Institute of Science. He did his post-doctoral work at the University of Valencia’s School of Engineering and at the laser institute at South China Normal University in Guangzhou, China, where he serves as visiting professor. He also studied at Yeshivat Nehalim and Yeshivat Birkat Moshe in Ma’aleh Adumim, and he’s active in the Tzohar rabbinic organization.

Two techniques combined

The method Fixler developed combines two techniques that never reached their full potential from a medical perspective. One of them, physical diffusion, which was developed in the late 1970s, is based on an idea that the reflection of light beamed at body tissue could help detect tumors. Each type of body tissue reflects light differently. Analysis of the diffusion of light that strikes the tissue can show which parts of the tissue absorb or scatter the light and detect cancerous growths.

“Researchers tried for a long time to construct models to find out what was happening in the tissues on the basis of light reflection,” Fixler said.

“Research in this field was stopped at a certain point because the model could not show for certain whether a tumor had been detected or whether the source of the diffusion came from different components in the body. It was fascinating as a basic study, but it turned out to have no clinical value.” He explained that a theoretical model known as diffuse reflection has been dominant since the 1980s. According to this model, one cannot rely solely on the reflection of light from tissue. “To determine whether there are cancerous growths, we need substances or particles that will allow us to create a better picture of the tissues. But this method did not lead to the manufacture of a clinical tool either because it does not allow us to find only what we are looking for. It does not provide univalent results.”

Efforts to develop a new method of tumor detection continued. “A new idea known as molecular agent came into being about 12 years ago,” he says. “Unlike the previous idea, which sought to get a general picture, the new idea was about obtaining findings at the level of the individual molecule. Based on that idea, a method called contrast imaging was developed over the past decade. In this method, a kind of secret agent is injected into the body. This agent sticks to the place where you’re looking for growths and can be used to get the picture you want. Those secret agents are the nanoparticles.”

The use of gold nanoparticles is widespread since gold is not toxic and integrates well with the biology of the human body. “The nanoparticles are actually tiny robots that run in our bloodstream,” Fixler says. “When I look at them in a molecular of a cancer antibody, they are sticking to the cancer cells and I can identify them from outside the body without any need for an MRI or CT.” Because of certain quantum characteristics, gold nanoparticles create a very strong reflection of light at a certain wavelength.

Over the past few years, an imaging field using gold nanoparticles has developed, and based on that idea, machines that detect and cure diseases have been built. But these machines have a substantial problem — the amount of gold that is necessary to create a significant effect and a large, high-quality image.

The solution that Fixler and his colleagues developed required a change in approach. “It’s like looking for tunnels,” he says. “There’s no chance of finding a tunnel just by examining the environment. Sometimes you have to wait for somebody to come out of it. Using that idea, we took a similar approach: we would rely not only on the light that was reflected from the particles, but also on the effect created by the diffusion of the light in the tissue.”

To improve the method, the researchers made gold nanoparticles shaped like rods rather than the conventional spheres. The rod shape changed the length of the wave that the particles reflected and enabled the particles to penetrate more deeply into the tissue. A more dramatic step was the development of a mathematical algorithm that translated the information coming from the nanoparticles into an actual image.

“Once the particles penetrate the tissue, we do not look at the reflection,” Fixler says. “Instead, we look at their effect on light diffusion within the tissue. Finally, the light that is reflected from the tissue is a calculable mathematical function that is based on the amount of photons coming from the tissue, depending on the distance from the point where the light entered.”

Fixler’s method is not limited to detecting cancer: He’s conducting a trial in the Interventional Cardiology Department at Beilinson Hospital to develop a diagnostic method for multiple sclerosis. “I believe that the more progress we make in the trials, the more we will be able to use the method to diagnose more diseases,” Fixler says.

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