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Abstract:
Using a nano-enhanced version of a device capable of detecting the smallest viruses in solution, researchers at the Polytechnic Institute of New York University (NYU-Poly) have demonstrated that they can detect a single cancer marker protein without the use of fluorescent labels. Stephen Arnold and his collaborators describe their new device in the journal Nano Letters.

Single Molecule Detection of a Cancer Biomarker

Bethesda , MD | Posted on September 6th, 2013

In 2012, Dr. Arnold and his team were able to detect in solution the smallest known RNA virus, MS2, with a mass of 6 attograms. Now, the NYU-Poly team has detected: a human cancer marker protein called thyroglobulin, with a mass of just 1 attogram, and the bovine form of a common plasma protein, serum albumin, with a far smaller mass of 0.11 attogram. An attogram is 10-18 grams, or a millionth of a millionth of a millionth of a gram.

This latest milestone builds on a technique pioneered by Arnold and collaborators from NYU-Poly and Fordham University. In 2012, the researchers set a sizing record by treating a novel biosensor with plasmonic gold nano-receptors, enhancing the electric field of the sensor and allowing even the smallest shifts in resonant frequency to be detected. Their plan was to design a medical diagnostic device capable of identifying a single virus particle in a point-of-care setting, without the use of special assay preparations.

To the surprise of the researchers, examination of their nanoreceptor under a transmission electron microscope revealed that its gold shell surface was covered with random bumps roughly the size of a protein. Computer mapping and simulations created by Stephen Holler, once a student in the Arnold laboratory and now at Fordham University, showed that these irregularities generate their own highly reactive local sensitivity field extending out several nanometers, amplifying the capabilities of the sensor far beyond original predictions.

Dr. Arnold and his collaborators named the novel method of label-free detection "whispering gallery-mode biosensing" because light waves in the system reminded him of the way that voices bounce around the whispering gallery under the dome of St. Paul's Cathedral in London. A laser sends light through a glass fiber to a detector. When a microsphere is placed against the fiber, certain wavelengths of light detour into the sphere and bounce around inside, creating a dip in the light that the detector receives. When a molecule such as a cancer marker clings to a gold nanoshell attached to the microsphere, the microsphere's resonant frequency shifts by a measureable amount.

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About National Cancer Institute (NCI)
To help meet the goal of reducing the burden of cancer, the National Cancer Institute (NCI), part of the National Institutes of Health, is engaged in efforts to harness the power of nanotechnology to radically change the way we diagnose, treat and prevent cancer.

The NCI Alliance for Nanotechnology in Cancer is a comprehensive, systematized initiative encompassing the public and private sectors, designed to accelerate the application of the best capabilities of nanotechnology to cancer.

Currently, scientists are limited in their ability to turn promising molecular discoveries into benefits for cancer patients. Nanotechnology can provide the technical power and tools that will enable those developing new diagnostics, therapeutics, and preventives to keep pace with today’s explosion in knowledge.

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Contacts:
National Cancer Institute
Office of Technology & Industrial Relations
ATTN: NCI Alliance for Nanotechnology in Cancer
Building 31, Room 10A49
31 Center Drive , MSC 2580
Bethesda , MD 20892-2580

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