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Crossing the Blood-Brain Barrier for Improved Visualisation

When it comes to using chemical or radioactive markers to make parts of the brain easier to see, and more finely detailed with a magnetic resonance scan, your options are limited.

Worse, if you are looking to bind to areas that should not be there, such as tumours, your options are precisely nil. At least, they used to be. Until now, no nanoparticle used for imaging has been able to cross the blood-brain barrier and specifically bind to brain-tumour cells. With current techniques doctors inject dyes into the body and use drugs to temporarily open the blood-brain barrier, risking infection of the brain.

However, a new brain tumour imaging agent has been developed which offers hope of far more useful MRIs of the brain, without any risk of infection to that precious tissue. Researchers at the University of Washington have developed fluorescent nanoparticles that cross the barrier safely. Even better, their fluorescent aspect improves contrast in both MRI and optical scans of brain tissue, both tumours and healthy tissue.

A mouse brain tumor imaged using nanoparticles or conventional techniques combined with optical imaging and MRI. The nanoparticles give a far clearer and cleaner picture, with tissue destinctions obvious, even to the naked eye.

What this means, is the new nanoparticles are also a candidate to aid research based imaging of the brain - working out what areas do what, when we are thinking, or sensing the environment around us. The added contrast allows a finer grain of detail than we have been able to differentiate before, and that translates directly into greater accuracy for neuroprosthetics.

Because crossing the blood-brain barrier depends on the size of the particle, its lipid, or fat, content, and the electric charge on the particle, the solution was to develop a particle which stays small when wet, soaked into the blood, and bypassing detection. The new nanoparticles are about 33 nanometers in diameter when fully immersed in the blood - about the size of a single silicon transistor each.


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