In its tomorrow issue, New Scientist reports that researchers at the University of New Mexico (UNM) had a brilliant idea to make bone-marrow biopsies more efficient for patients affected by leukemia. In "Nanoparticles that cancer cells can't resist," the magazine writes that the basic idea is to use magnetic iron oxide nanoparticles encased in a biocompatible material. When these nanoparticles are injected in the body, they gather around cancer cells, turning them into minuscule magnets that are easily captured by other magnets encased in the tips of biopsy needles. The researchers want now to start clinical trials and think that a commercial clinical device will be available in five years.
You can see above a "photo of the tip of a magnetic needle, left, showing the two 2 mm long, 1 mm diameter cylindrical magnets separated by a nonmagnetic steel spacer 2 mm long. A nonmagnetic stainless-steel stiffening rod 17 cm long abuts the lower magnet and the ensemble is encased in a polyimide tube. On the right is a 5 cm long polyimide sheath that slips over the tip of the needle." (Credit: UNM)
Here is how New Scientist summarizes the concept. "The idea is to use magnetic iron oxide nanoparticles encased in a biocompatible material. These in turn can be coated with antibodies that bind to chemicals found only in cancerous cells. When injected into the body, thousands of the particles stick to cancer cells, turning them into miniature magnets. The cells can then be drawn towards magnets encased in the tip of a biopsy needle."
But will it work? "A mathematical model of the system confirmed that significant numbers of cancer cells, laden with nanoparticles, could be attracted to a needle within two or three minutes. In the lab, the researchers showed that a magnetised needle could attract leukaemia cells surrounded by nanoparticles and suspended in blood or other synthetic materials designed to mimic bodily fluids. Nanoparticles have been used before to destroy diseased cells but this is the first time they have actually retrieved cells."
In "'Magnetic biopsies' better by design," nanotechweb.org provides additional details (Free registration needed).
"The result is that the physician doesn't have to look under the microscope at lots and lots of cells, and look for the rare ones. We will only be collecting those cells that physicians are interested in," said Ed Flynn, adjunct professor of physics at UNM.
The system's likely behaviour has been modelled in considerable detail, Flynn told medicalphysicsweb. Researchers first mapped the field pattern around the magnetic needle, and evaluated the forces that the applied field would exert on magnetically labelled cells. They then studied how the viscosity of the fluid that cells were suspended in would affect the cells' motion. Taken together, this information was used to calculate the time it would take for tagged cells to collect at the needle.
While searching for a commercial partner and starting clinical trials, the scientists are already working on the next step. They think that their device might successfully target "cells from from breast, prostate, and ovarian cancers that have spread to other parts of the body in amounts too tiny to sample with an ordinary needle," as writes New Scientist.
This research work has been published in the specialized journal Physics in Medicine and Biology under the name "Magnetic needles and superparamagnetic cells" (Volume 52, Number 14, Pages 4009-4025, July 21, 2007). Here is a link to the abstract which starts like this. "Superparamagnetic nanoparticles can be attached in great numbers to pathogenic cells using specific antibodies so that the magnetically-labeled cells themselves become superparamagnets. The cells can then be manipulated and drawn out of biological fluids, as in a biopsy, very selectively using a magnetic needle."
For more information, you also can read the full paper available from the above link (PDF format, 17 pages, 1.36 MB) (Free registration needed). The above illustration has been extracted from this technical article.
Sources: New Scientist Magazine, July 14, 2007 issue, via EurekAlert!; Paula Gould, nanotechweb.org, July 10, 2007; and various websites
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