Page last updated at 18:54 GMT, Tuesday, 11 November 2008

Cells made to haul custom payload

Cell with rucksack (MIT)
The cells' custom cargo could deliver drugs or vaccines more precisely

Scientists have fitted individual cells with polymer "rucksacks" that could carry drugs or imaging agents to specific parts of the body.

Because the cells are only partially covered by the polymer packets, their normal function can be maintained.

Filling the rucksacks with magnetic nanoparticles allowed them to be manipulated with magnets, the team reports in Nano Letters.

The approach could also be used to direct cells for tissue engineering.

By using live cells, the approach can make use of the cells' natural functions while taking along a custom payload.

"We're trying to utilise what nature has already perfected," says co-author Albert Swiston, from the Massachusetts Institute of Technology (MIT) in Cambridge, US.

The team started by building up the rucksacks using what is known as polymer multi-layer technology.

The process starts with a patterned surface that allows polymer layers to be built up only in specific areas. Three layers are then deposited onto the surface: one that sticks to cell walls, one containing the rucksack's payload and one that encapsulates it.

A liquid mixture containing live cells is then poured over the array of prepared rucksacks, which then bond to the cells.

By raising the temperature of the mixture, the rucksacks are made to disconnect from the surface, leaving the cells floating around with their new cargo.

We haven't even thought of all the applications yet
Albert Swiston, MIT

Directed therapy

For the latest research, the team loaded the rucksacks with magnetic nanoparticles, and then demonstrated that the cells could be manipulated with the field from a simple magnet.

That approach could be very useful for directing cells to particular sites in the body. Magnetic nanoparticles are already used to increase the image quality in magnetic resonance imaging, so the findings could be used for even better imaging in the body.

The cells that carried the rucksacks were lymphocytes, a cell type involved in the immune system. That makes for another avenue towards more directed therapy.

"Immune system cells can be primed to go to specific places in the body," says Mr Swiston. "We could load them with drugs or chemotherapy agents, and immune cells love to travel to tumours or sites of inflammation or trauma."

Besides drug delivery, the approach could be used to more accurately target vaccines into the lymph system, rather than flooding them throughout the whole body.

And if cells can be loaded with specifically-designed rucksacks and concentrated in certain areas, they could be made to self-assemble into a natural scaffolding for tissue engineering, though Mr Swiston admits this is a significantly longer-term goal.

While the research is still in its early stages, it holds much potential for these and other uses within the body.

"We haven't even thought of all the applications yet," says Mr Swiston, "and I think there's a whole lot more out there".

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The light-coloured cells, with "rucksacks", move faster in a magnetic field



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