growing new muscle cells/breathing without ventilator

[Guest guest]

March 15, 2004 L.A. Times Headlines

IN THE LAB Big idea in mini-robotics

Tiny devices propelled by living tissue are a first step in creating

half-artificial, half-human miniature robots.

By Marsa, Special to The Times

Scientists have long sought ways to miniaturize medical devices so they

can be permanently implanted in the body. A key stumbling block,

however, is finding a way of shrinking the power source for these tiny

devices.

Even today's compact cardiac defibrillators or pacemakers, for example,

must be powered by relatively large batteries.

The newly minted machines in Carlo Montemagno's UCLA lab may overcome

this formidable hurdle.

Smaller than a pencil dot, made of silicon and powered by " legs " of

living muscle tissue, the devices are a critical first step in the

creation of part-human, part-artificial miniature robots. Such machines

would be an entirely new class of autonomous devices, ones fueled by

glucose, the same energy source as our bodies.

" This is a very important technological advance because it shows that

you can fuse a living cell with a synthetic material and make a

mechanical device that functions, " says G. Dennis, a biomedical

engineer at the University of Michigan in Ann Arbor.

Dennis proved in an earlier study that, under the right conditions,

muscle cells automatically transform into functional tissue. UCLA

researchers have taken his work further, creating miniature robots

powered by heart-muscle tissue. (Unlike other muscle tissue, which must

be electrically stimulated, cardiac tissue expands and contracts on its

own.)

Ultimately, the technology could be used to power tiny nerve-stimulators

that prompt the diaphragm to expand and contract, making it possible for

paralyzed patients to breathe without a ventilator. It could also lead

to the development of a compact power source for internal sensors,

helping physicians diagnose or treat disease. The technology could even

drive pacemakers and other implanted devices.

Instead of being driven by micromotors attached to bulky batteries or

wires, the resulting devices could be fueled by glucose in the

bloodstream. The muscle tissue converts glucose into mechanical energy;

the expansion and contraction of the muscle then generates the

electrical energy that propels these miniature machines.

" You could make a device smaller than a postage stamp that was fully

integrated, " says Montemagno, chairman of the university's

bioengineering department. " You can put it in and forget about it — no

more need to replace batteries, or worry about infections from the

external wiring. "

Still, some formidable technical problems need to be solved before these

micro-robots will become part of standard medical practice. The tiny

implants, which would combine muscle tissue and electronics into a

single system, must be made durable, with packaging that protects the

electronic parts yet allows them to work inside the body.

Simply creating these first tiny robots was a daunting technological

challenge. Researchers had to get the muscle cells to bind to a

synthetic material. And once the cells had attached themselves to the

material, they had to be able to contract and relax to produce the

robot's crawling motion.

" You can't grow cells and muscles in thin air, " says Montemagno. " They

have to be supported in some way, yet still are free to move. "

Researchers finally hit upon a bit of chemical legerdemain that enabled

them to solve these problems. The key was using a special polymer that

hardens when heated and liquefies when cooled, says Montemagno.

First they created an arch-shaped mold from silicon and coated it with a

layer of this special polymer. Then they painted the underside of the

arch with a gold film that sticks to the muscle cells. Finally, the team

added cardiac muscle cells from rats to the structure and cooked the

whole thing in an incubator.

After three days, the muscle cells had adhered to the silicon and

transformed themselves into muscle fibers that grew along the length of

the arch. When the structure was removed from the incubator, the polymer

cooled, turned into a liquid and was easily washed off.

" This freed up the muscles, which started to move immediately, " says

Montemagno.

" Now that we've established the basic technology, " he adds, " with enough

resources, we could have prototype devices within five years. "

Aid in breathing on their own

Miniature robots offer but one potential way to help paralyzed patients

breathe without a ventilator. Another option may be an experimental

procedure in which electrodes are implanted near the diaphragm.

The electrodes, inserted through three dime-sized incisions, deliver

jolts of electricity 12 times a minute to motor points in the body that

stimulate the phrenic nerve. Such stimulation prompts the diaphragm to

expand and contract.

As a minimally invasive procedure, it is less dangerous than

conventional surgery. That type of operation requires opening the chest,

which can cause infection. It can also permanently damage the phrenic

nerve because implanted electrodes stimulate the nerve directly — the

new technique taps points near the nerve, not right on it.

At a scientific meeting this month, researchers revealed that three of

the six people who have undergone the procedure are completely free of

the ventilator, and two others are increasing their time off the

ventilator. (Actor Reeve is one who is gradually weaning

himself from the assisted-breathing device.) In one patient, the implant

system failed to stimulate the diaphragm.