Living cells can now be tracked using magnetic beacons

June 27, 2003

if you do not read the newscientist , ya' may want to think about what these guys are saying!! I only sent this here, spread it around, this stuff makes me kringe!!

karl

Follow that cell

New Scientist vol 166 issue 2234 - 15 April 2000, page 11

Living cells can now be tracked using magnetic beacons

A FRAGMENT of HIV has been used to create minuscule magnetic beacons for tracking living cells as they move through the body. The technique could be a crucial tool for developing and improving stem cell therapies.

The cores of the beacons are specks of easily magnetised iron oxide just 45 nanometres across. These are coated with a glucose polymer called dextran to make them compatible with living tissue. There have been attempts to use such nanoparticles to track cells before, but researchers found them ineffective because most cells would not take them up.

But this month, scientists led by Ralph Weissleder at a Harvard Medical School hospital in Charlestown, Massachusetts, revealed a solution. The group adds a snippet of a HIV protein known as "Tat" to the particles. Tat helps to get HIV into cells unnoticed and confers the same ability on the nanoparticles, allowing them to invade a cell so that it can be tracked.

Using the nanoparticles, the researchers have already tracked cells in mice and rats. They tag cells by placing them in a solution of the nanoparticles, many of which end up in each cell. "They act like one big magnet," says Weissleder.

These magnets can be tracked using magnetic resonance imaging. In the first experiments, the particles could only be followed for about seven days before they disintegrated. But recent improvements in the coating have bumped up their lifespan to three weeks, says Weissleder.

The team has tagged both haematopoietic progenitor cells, which form blood cells, and neural progenitor cells. Progenitor cells are descended from stem cells—which have the potential to develop into any tissue—and are the earliest level of specialisation.

Blood stem cells are already given to patients with damaged immune systems. They lodge in bone marrow and produce new blood and immune cells (New Scientist, 14 August 1999, p 6). Exactly how the cells home in on bone marrow is not yet understood, but researchers know that only a small percentage make it.

The new beacons offer the first chance to follow the homing of haematopoietic cells in a living animal and gauge how many cells make it to the marrow. "That would be quite useful to be able to follow what happens," says Loren Field, a biologist at Indiana University in Indianapolis, who works with stem cells.

Because the beacons are magnetic, researchers can retrieve the cells after an experiment. That will give them the chance to analyse cells that do make it to bone marrow and find ways to increase the number that reach the target. Researchers also hope to find better ways of getting neural and other stem cells to damaged areas, where they can generate new cells.

Weissleder says the group is aiming to carry out trials in humans within the next three years.

Mark Schrope karl theis jrvideo field reporterwww.RealityExpander.com Ch.10 TimeWarnerAustin,Texas cell 512 297-9875e-mail: theis888 www.exposureofthetruth.isfamous.com

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