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Bizarre nanoparticles found in kidney

ABC Science Online

Friday, 22 December 2006

DNA
Researchers have found DNA associated with nanoparticles from kidney stones. Could these strange particles be nanobacteria? (Image: iStockphoto)
Researchers who've found strange nanoparticles in a handful of kidney stones say these self-replicating specks may play a role in disease.

The US researchers are not sure whether these tiny particles, 50 to 100 nanometres across, are living nanobacteria or just some strange non-living self-assembling ball of chemicals.

"We have some evidence that would support either possibility," says kidney specialist Dr John Lieske of the Mayo Clinic College of Medicine.

He and colleagues report their findings in the December issue of the Journal of Investigative Medicine.

At some point in their life about 10% of people will get kidney stones, a painful condition in which calcium deposits clog the kidneys.

Scientists aren't sure what causes these deposits. But one theory that Lieske and colleagues are investigating is that tiny calcium-covered particles are partly to blame.

Previous research has found such particles in human serum, urine, renal cysts from patients with kidney disease, as well as in kidney stones.

Lieske says some researchers dub the particles nanobacteria, and propose they are a new disease-causing agent.

But Lieske says there is not yet enough evidence these particles are alive.

Nanoparticle investigation

Lieske's team isolated the nanoparticles, which have a protein-lipid core surrounded by a calcium phosphate shell, from kidney stones.

The researchers grew the nanoparticles in culture over a period of four to eight weeks.

They found that antibiotics and metabolic inhibitors slowed the particles' growth.

Then the researchers grew a large batch of nanoparticles, dissolved the calcium shells and extracted proteins and DNA.

Does all this mean that the nanoparticles are nanobacteria after all?

Lieske says it's still too early to say.

"There definitely is DNA associated with [the nanoparticles]," he says. "But is that a contaminant?"

He says some fragments of the protein and DNA appear to match known bacteria.

His team now plans to grow more nanoparticles and see if they can find a unique genetic signature that would prove the nanoparticles are indeed nanobacteria.

Scepticism

Geologists and astrobiologists have also considered the possibility of nanobacteria over the years. For instance, understanding the full range of life forms is important in our search for extraterrestrial life.

Professor Malcolm Walter of the Australian Centre for Astrobiology in Sydney, says there has been much scepticism about nanobacteria.

Martian meteorite
This Martian meteorite contains structures that some people think are nanobacteria (Image: NASA)
For instance, he says there is still some debate about whether calcium carbonate nanoparticles found in a Martian meteorite are nanobacteria.

"[The particles are] so small nobody could understand how any known biochemical machinery could fit into them," he says.

Walter says the US National Academy of Sciences convened a study to explore how small a living organism could be.

They concluded, he says, that anything smaller than 100 nanometres could be capable of independent life.

"This latest report is interesting but I notice how cautious [the authors] are in what they say," says Walter.

Chemical self-assembly

Whether they are alive or not, understanding the role of nanoparticles in kidney stones will be useful in developing treatments, says Lieske.

The particles could still be infectious disease-causing agents whose chemistry allows them to self-assemble.

"That could be a very interesting pathogenic process that might be something like prion proteins where it is disease causing but it's not necessarily an organism like we think of traditionally," says Lieske.

Either way, Lieske and team are containing the nanoparticle experiments so the particles don't accidentally give anyone a disease.



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