Researchers say a pill could soon send radio signals from inside your stomach to help doctors recognize signs of disease.

Scientists have developed a small pill for patients to swallow. It mixes synthetic biology and electronics to find bleeding in the stomach and other parts of the digestive tract.

The system can be changed for many medical, environmental and other uses, the researchers said.

The biological part of the pill uses bacteria engineered to light up when it comes in contact with heme, the iron-containing molecule in blood.

The electronic side includes a small light detector, computer and computer chip. It also has a battery to provide power and a transmitter that sends information to a cellphone or computer.

"A major challenge for sensing in the GI (gastrointestinal) tract is, the space available for a device is very limited," said electrical engineer Phillip Nadeau. He is with the Massachusetts Institute of Technology in Boston, Massachusetts.

Using very low-power electronics, Nadeau and other engineers put all the parts in a pill. It measures about 3 centimeters long by 1 centimeter wide.

The pill is still a little too big to swallow, but Nadeau says it likely can be engineered to a third that size.

The engineered bacteria are in areas covered by a membrane. This thin, soft material lets small molecules in, but does not let the organisms out.

The researchers say the bacteria can be engineered to die if they accidentally leak from the pill. Future models may just use the most important enzymes instead of whole bacteria.

In laboratory tests, the pill successfully identified pigs fed small amounts of blood from those not given blood. The pill has not been tested on human beings, but the team hopes to do so in the next year or two.

Since the parts cost little to manufacture, researchers believe that, once ready, the final product would sell for tens to hundreds of dollars. And they say the same method could be used to identify markers for disease or to find chemicals in the environment.

"It's really exciting, and I think it's got a lot of legs," said Rice University bioengineer Jeff Tabor. He was not part of the research team.

But Tabor notes that the sensors may need to be much more sensitive than what was used in the pig tests. He says there may be much less blood in the stomachs of real human patients than what the pigs were given. Other conditions may have the same limitations.

"For many actual diseases, you might have far less of the molecule you need to sense available to you," he added.

A report on the study was published in the journal Science.

I'm Susan Shand.

This story was reported by VOA's Steve Baragona. It was adapted by Susan Shand and edited by George Grow.

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pill – n. a small, rounded object that you swallow and that contains medicine

stomach – n. the organ in your body where food goes and begins to break down after you swallow it

synthetic – adj. made by combining different substances; man-made, not natural

digestive tract – n. a series of organs in the body, including the stomach and the intestines

detector – n. a device for identifying or measuring the presence of something

challenge – n. a problem; an invitation to compete

transmitter – n. a device that sends out signals