CHICAGO, USA: U.S. scientists have developed a tiny sensor that can detect small amounts of cancer-causing toxins or trace the effectiveness of cancer drugs inside living cells.

The finding, reported on Sunday in the journal Nature Nanotechnology, offers a new tool for tracking specific chemicals in the body.

"We made a very small nanosensor that can detect cancer-causing molecules or important therapeutic drugs inside of a single living cell," said Michael Strano of Massachusetts Institute of Technology in Cambridge, who worked on the study.

"It's much smaller than a living cell in your body," Strano said in a telephone interview. "It's so small it can be placed into environments that aren't accessible with larger sensors." Strano said the sensors are made up of thin filaments of carbon molecules known as carbon nanotubes.

Several teams are using nanomaterials -- thousands of times smaller than the width of a human hair -- to develop new ways to deliver drugs in the body or improve diagnosis of disease.For its sensors, Strano's team wrapped carefully shaped carbon nanotubes with DNA, which offers a binding site for DNA-damaging agents inside cells.

The sensors give off a fluorescent light that can be detected in the near-infrared light spectrum.

Because human tissues do not light up in this spectrum, the nanotubes stand out.Strano said the light signal changes when the sensors interact with DNA inside cells.

These changes can help them identify specific molecules.

"It's a way of fingerprinting chemistry," Strano said.Because the sensors are coated in DNA, Strano said they can be safely injected into living cells.

"Eventually the cell eats the protein off the coating and it essentially spits it out," he said.

He said the most immediate use of the technology would be as a very powerful tool for scientists to study the effects of very small amounts of a chemical.

But it could eventually be used as a new way to image the human body.  “It’s a new tool. There is nothing else like it.”