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Posted: June 19, 2006

Imaging live cells with a fluorescent magnetic nanoparticle

(Nanowerk News) Investigators at the UniversitÚ Pierre et Marie Curie in Paris, France, have developed a versatile new method for creating nanoparticles that are both magnetic and fluorescent. They then used the nanoparticles created with this method to label and image live cells. The researchers note that these particles could be used to track cell movements within the body and to help separate different cell types in basic research and diagnostic applications.
Reporting its work in the journal Langmuir, a research team headed by ValÚrie Cabuil, Ph.D., described its use of a sulfur-containing molecule known as m-2,3-dimercaptosuccinic acid, or DMSA, that interacts strongly with the surface of iron oxide nanoparticles. In addition to its ability to thoroughly and uniformly coat the nanoparticle surface, this molecule has two other useful properties. First, it contains a reactive chemical group to which a wide variety of other molecules, including many fluorescent dyes, can be attached. Second, it forms a coating that is negatively charged, which keeps individual coated particles from aggregating with one another.
When the researchers added nanoparticles labeled with the fluorescent dye rhodamine to cancer cells growing in culture, they were able to observe that the nanoparticles attached themselves to the outer cell membrane. While viewing the now-labeled cells using a fluorescent microscope, the investigators were able to follow the nanoparticles as the cells transported them through the cell membrane and into internalized compartments known as endosomes. Once the nanoparticles were inside the cells, the researchers applied a magnetic field to the culture dish, turning the nanoparticle-filled endosomes into internal magnets. Like any set of magnets, the endosomes were attracted to one another, forming small chains in the cell cytoplasm.
This work is detailed in a paper titled, "Fluorescence-modified superparamagnetic nanoparticles: intracellular uptake and use in cellular imaging" in the journal Langmuir.
Source: National Cancer Institute
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