Another research team has found a way to use nanotechnology to deliver drugs. As you may know, polymeric nanoparticles are excellent carriers for delivering drugs. But as they are quickly removed from the blood, they are somewhat ineffective for the task. Now, researchers from the University of California at Santa Barbara (UCSB) have found that 'nanoparticles can be forced to remain in the circulation when attached to red blood cells.' In other words, these nanoparticles hitchhike on red blood cells. Apparently, these nanoparticles could stay with their hosts for their life time -- about 120 days. So this could lead to new treatments for cancer or heart disease. But stay tuned, because this technique only works in the lab right now.
You can see above some of these polymer nanoparticles attached to red blood cells. These one will remain in circulation for a long time. Unattached nanoparticles are rapidly cleared by the body's immune system, sometimes in minutes. (Credits: Peter Allen, UCSB; Society for Experimental Biology and Medicine) Here is a link to a larger version of this picture.
The UCSB team was led by led by Samir Mitragotri and his research group, including Elizabeth Chambers, a recent doctoral graduate who works on the targeted delivery of nanoparticles. Here is a quote from Mitragotri about this discovery.
"Attachment of polymeric nanoparticles to red blood cells combines the advantages of the long circulating lifetime of the red blood cell, and their abundance, with the robustness of polymeric nanoparticles," said Mitragotri. "Using red blood cells to extend the circulation time of the particles avoids the need to modify the surface chemistry of the entire particle, which offers the potential to attach chemicals to the exposed surface for targeting applications."
But how long these nanoparticles will remain in the patient's blood? "The researchers say that it may be possible to keep the nanoparticles in circulation for a relatively long time, theoretically up to the circulation lifetime of a red blood cell – which is 120 days – if the binding between particles and the red blood cells is strengthened. The methodology is applicable to drugs that are effective while still attached to a red blood cell, although the researchers say that slow release from the red blood cell surface is also feasible."
As I mentioned above, this method has only been proven in a lab. But the researchers think that this process might be used in the future in a variety of applications. Mitragotri says "this mode of prolonging particle circulation has significant implications in drug delivery, potentially leading to new treatments for a broad variety of conditions such as cancer, blood clots and heart disease."
For more information, this research work will be published in the next issue of the Experimental Biology and Medicine journal published by the Society for Experimental Biology and Medicine. The title of the article will be "Long Circulating Nanoparticles via Adhesion on Red Blood Cells: Mechanism and Extended Circulation" and will appear in the July 1, 2007 issue of the journal (Volume 232, Number 7).
Sources: Society for Experimental Biology and Medicine news release, June 27, 2007; and various websites
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