'Nanoworms' could be the next generation of bio-devices to locate and destroy tumours too small to detect by conventional methods.

This smart 'anti-cancer missile' system will deliver toxic anti-cancer drugs to tumours in high concentrations, without any side effects.

Nanoworms have another advantage. They can stay in the bloodstream for hours, unlike single particles of similar size that are identified and removed by the immune system within minutes, said Michael Sailor of University of California (U-C), who led the research.

"The longer these nanoworms stay in the bloodstream, the more chances they have to hit their targets, the tumours," said Ji-Ho Park, working in Sailor's lab.

Park was the motivating force behind the discovery when he accidentally found that gummy worm aggregates of nanoparticles stayed for hours in the bloodstream despite their relatively large size.

When attached to drugs, these nanoworms would help increase their potency by delivering them directly to the tumours," said Sangeeta Bhatia, physician and bioengineer of Massachusetts Institute of Technology and member of the team.

"They could decrease the side effects of toxic anti-cancer drugs by limiting their exposure of normal tissues and provide a better diagnosis of tumours and abnormal lymph nodes," she added.

The scientists constructed nanoworms from spherical iron oxide nanoparticles that join like segments of an earthworm, to produce structures about three million times smaller than an earthworm.

Their iron-oxide composition allows the nanoworms to show up brightly in diagnostic devices, specifically the MRI, or magnetic resonance imaging, machines that are used to find tumours.

"We are now using nanoworms to construct the next generation of smart tumour-targeting nanodevices," said Erkki Ruoslahti of U-C. We hope that these devices will improve the diagnostic imaging of cancer and allow pinpoint targeting of treatments into cancerous tumours."