Remotely controlled nanoparticles fight tumors

Many researchers around the world have tried to use nanoparticles to battle cancer. Now, researchers from the MIT have gone a step further. They found a way to 'talk' with the nanoparticles. In other words, they can control the nanoparticles and tell them to deliver drugs directly into tumors. Strands of DNA containing drugs were used at tethers to some superparamagnetic nanoparticles. When exposing the particles to a low-frequency electromagnetic field, the particles generate heat that, in turn, melts the tethers and releases the drugs. Bright idea!

Many researchers around the world have tried to use nanoparticles to battle cancer. Now, researchers from the MIT have gone a step further. They found a way to 'talk' with the nanoparticles. In other words, they can control the nanoparticles and ask them to deliver drugs directly into tumors. Strands of DNA containing drugs were used at tethers to some superparamagnetic nanoparticles. When exposing the particles to a low-frequency electromagnetic field, the particles generate heat that, in turn, melts the tethers and releases the drugs. Bright idea!

Remotely controlled nanoparticles

The image above shows these remotely controlled nanoparticles. You can skip the 'enigmatic' original caption if you wish. "Polymer-coated, superparamagnetic nanoparticles (NPs) were modified to polyvalently display either a tyrosine-containing kinase substrate or an SH2 domain. NPs remain dispersed until kinases phosphorylate substrate NPs, triggering NP assembly via phosphopepetide-SH2 binding. Kinase-directed assembly amplifies the T2 relaxation in MRI and is fully reversible by phosphatise."

The research team has been led by Sangeeta Bhatia, an associate professor in the Harvard-MIT Division of Health Sciences and Technology (HST) and in MIT's Department of Electrical Engineering and Computer Science. She worked closely with Geoffrey von Maltzahn, a graduate student and a member of Bhatia's Laboratory for Multiscale Regenerative Technologies.

How does this really work -- in plain English? "The system that makes it possible consists of tiny particles (billionths of a meter in size) that are superparamagnetic, a property that causes them to give off heat when they are exposed to a magnetic field. Tethered to these particles are active molecules, such as therapeutic drugs."

And how these therapeutic drugs are delivered? "Exposing the particles to a low-frequency electromagnetic field causes the particles to radiate heat that, in turn, melts the tethers and releases the drugs. The waves in this magnetic field have frequencies between 350 and 400 kilohertz -- the same range as radio waves. These waves pass harmlessly through the body and heat only the nanoparticles."

But why did the researchers used strands of DNA for their tethers? "Two strands of DNA link together through hydrogen bonds that break when heated. In the presence of the magnetic field, heat generated by the nanoparticles breaks these, leaving one strand attached to the particle and allowing the other to float away with its cargo."

Obviously, this experiment is just what is, an experiment. And there are still lots of work to do before such therapies arrive to hospitals.

For more information, this research work has been recently been published in Advanced Materials under the title "Nanoparticle self-assembly directed by antagonistic kinase and phosphatase activities" (Volume 19, Issue 21, Pages 3579-3583, November 2007). Here are two links to the references and to the full paper (PDF format, 5 pages, 377 KB). The above image has been extracted from this article.

Sources: Elizabeth Dougherty, Harvard-MIT Division of Health Sciences and Technology, November 16, 2007; and various websites

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