杏吧原创

SURGEONS about to perform delicate operations on the heart or major blood vessels need the clearest pictures they can get. Magnetic nanoparticles injected into the bloodstream will help reveal fine details on MRI (magnetic resonance imaging) scans 鈥� but there鈥檚 a snag. The particles quickly accumulate in the liver, which then removes them from the body.

Now Mauro Magnani of the University of Urbino in Italy and his team have found a way to get the tiny particles to spend longer in the bloodstream, by hiding them inside living red blood cells.

To do this, the team first immerse the blood cells in a watery solution, which causes them to swell. This opens pores in their membranes, allowing nanoparticles to drift into the cells. They become trapped when the cells are returned to a solution more like blood and the pores close up again (Journal of Nanoscience and Nanotechnology, ).

When the treated cells are injected back into the bloodstream, they remain there until they are destroyed naturally, which normally takes about four months. During this time, the nanoparticle payload can be used to help visualise the circulatory system.

Magnani has already used magnetic blood cells to image the hearts of mice. 鈥淲e can see the circulatory system, the heart and the heart cavities,鈥� he says. He is now working with Philips Research in the Netherlands to establish whether a similar procedure can safely be used in humans. The nanoparticles are already approved for direct injection into patients鈥� bloodstreams, and red blood cells have been used as drug delivery vehicles in several thousand people with no serious side effects so far. If the procedure is used, only a small fraction of a person鈥檚 red blood cells will carry the particles, Magnani points out.

Mohammed Hamady, a consultant radiologist at Imperial NHS Trust in London, says the technique could be particularly useful for monitoring patients after treatment to patch up an aortic aneurysm, a swelling in the wall of the largest artery in the body. Blood sometimes leaks out from the repair, and this can be difficult to detect. 鈥淭his technique could help us to follow the flow of the blood,鈥� he says.

In a separate study, Magnani added fluorescent particles to red blood cells which make them glow when exposed to infrared light. This allowed him to image the movement of individual blood cells through capillaries at the back of the eye in monkeys and rabbits (Investigative Ophthalmology and Visual Science, ). Measuring the speed at which blood flows through these capillaries could help diagnose conditions such as diabetic retinopathy and age-related macular degeneration, which can lead to blindness.

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