Posted: August 28, 2009 |
Nanoparticles detect and profile cancer cells rapidly |
(Nanowerk News) Using a new type of paramagnetic nanoparticle and a nuclear magnetic resonance (NMR) system built into a microfluidic device, a team of investigators at the Massachusetts General Hospital and Harvard Medical School has created an assay system capable of detecting as few as two cancer cells in 1 microliter of biological fluid. In addition, the new assay requires little sample processing and produces results in less than 15 minutes.
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Reporting its work in the Proceedings of the National Academy of Sciences of the United States of America (Rapid detection and profiling of cancer cells in fine-needle aspirates), a research team led by Ralph Weissleder, M.D., Ph.D., co-principal investigator of the MIT-Harvard Center of Cancer Nanotechnology Excellence, describes the methods it developed to create a small but highly magnetic nanoparticle. The new nanoparticle is built around an iron-manganese core and is coated with a small, biocompatible organic molecule to render it soluble in water. This coating also provides attachment points to which the investigators added one of three different monoclonal antibodies, each of which recognizes a specific cancer biomarker.
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The investigators also detailed their construction of a microfluidic NMR probe that dramatically improves on the signal-to-noise performance of an earlier probe they had developed. By improving the signal-to-noise properties of their detector, the investigators were able to reduce the sample volume needed for analysis to 1 microliter and increase mass-detection sensitivity by tenfold.
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To test their device, the researchers used fine-needle aspirates from human tumors growing in mice as the biosample. Upon obtaining the biosample, the investigators added antibody-labeled magnetic nanoparticles, let them incubate for 5 minutes, washed the aspirates to remove excess nanoparticles, and then injected them into the microfluidic device. Using one antibody-labeled probe, the results were far from optimal, missing as many as 72% of the cancer cells in the sample. However, adding a second antibody-labeled nanoparticle reduced the false-negative rate to 28%, and adding the third antibody-labeled nanoparticle dropped the false-negative rate to almost zero.
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