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Magnetic nanotags detect cancer much earlier than current methods

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October 19, 2009

Stanford Professor Shan Wang and graduate student Richard Gaster, left, have developed an ...

Stanford Professor Shan Wang and graduate student Richard Gaster, left, have developed an early-warning system for cancer (Images: L. A. Cicero)

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Extremely sensitive nanosensor chips are being developed by Stanford University researchers in an attempt to detect the early signs of cancer, called biomarkers, in humans. The researchers say their sensor is around 1,000 times more sensitive than current technology and is accurate regardless of which bodily fluid is being analyzed. It can also detect biomarker proteins over a range of concentrations three times broader than any existing method. It is forecast that earlier detection of cancer biomarkers will lead to improved survival rates among cancer sufferers.

Already shown to be effective in the early detection of tumors in mice, the nanosensor chip can search for up to 64 different proteins and may be helpful in providing radically earlier detection of even the most elusive cancers in humans. Researchers are hopeful that the sensor will detect markers of other diseases, too.

"In the early stage [of a cancer], the protein biomarker level in blood is very, very low, so you need ultra-sensitive technology to detect it," said Shan Wang, professor of materials science and engineering and of electrical engineering, and senior author of a paper describing the sensor. "If you can detect it early, you can have early intervention and you have a much better chance to cure that person." The professor’s findings were published online on Nature Medicine's website during October.

To add to the promising news, Wang said the nanosensor technology could also allow doctors to rapidly determine whether a patient was responding to a particular course of chemotherapy. "We can know on day two or day three of treatment whether it is working or not, instead of a month or two later," he said.

The sensor uses magnetic detection nanotechnology Wang and his associates had developed previously. It can detect a given cancer-associated protein biomarker at a concentration as low as one part out of a hundred billion (or 30 molecules in a cubic millimeter of blood).

Early detection of tumors in mice

The most impressive performance gain detailed in the Nature Medicine paper is that the magnetic-nano sensor can successfully detect cancerous tumors in mice when levels of cancer-associated proteins are still well below concentrations detectable using the current standard methodology, known by the acronym ELISA.

"That is a critical finding for us because it says that in a realistic biological application – that of tumor growth in mice – we can actually see tumors before anything else could have detected them," said Sam Gambhir, professor of radiology at Stanford.

"It is one thing to have the technology show that it can work in principle; it is quite another to actually utilize it with real mouse blood samples from a real mouse growing a real tumor."

Humans next?

Wang said one of the next steps in the research would be to test the magnetic-nanosensors on human blood samples taken from a long-term study in which researchers drew blood samples from subjects prior to any of them being diagnosed with cancer.

"We can actually use our technology to study all these samples and we may be able to tell a year before or half a year before or three months before the diagnosis," Wang said. "That work will be extremely interesting."

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