Researchers in China appear to have uncovered how nanoparticles which are used in medicine for diagnosis and delivering drugs may cause lung damage.

Nanotechnology, or the science of the extremely tiny, is an important industry. One nanometer is one-billionth of a meter.

Apart from medicine, it is used in products like sporting goods, cosmetics, tires and electronics and has a projected annual market of around US$1 trillion by 2015.

However, concerns are growing that it may have toxic effects, particularly to the lungs. But it has never been clear how the damage is caused.

In an article published in the Journal of Molecular Cell Biology, the Chinese experts said a class of nanoparticles used in medicine, ployamidoamine dendrimers (PAMAMs), may cause lung damage by triggering a type of programed cell death known as autophagic cell death.

In experiments, they observed how several types of PAMAMs killed human lung cells but found no evidence that the cells were dying by apoptosis, a natural and common type of cell death.

In a subsequent experiment in mice, they injected an autophagy inhibitor in mice and later exposed the rodents to nanoparticles and found that it "significantly ameliorated the lung damage and improved survival rates."

"This provides us with a promising lead for developing strategies to prevent lung damage caused by nanoparticles," said the leader of the team, Chengyu Jiang, a molecular biologist at the Chinese Academy of Medical Sciences in Beijing.

Scientists hope nanoparticles will be able to improve the effectiveness of drugs and gene therapy by carrying them to the right place in the body and by targeting specific tissues, regulating the release of drugs and reducing damage to healthy tissues.