Scientists at Northwestern University in the US say they have recreated the structure of bone at a microscopic level.

The molecules that form this structure - created by the team - "mimic" the appearance of tiny collagen fibres, which are key to strong bone growth.

They can be coaxed into assembling themselves into structures that are almost identical to those found at a microscopic level in the body itself.

The close match makes it far easier for natural bone cells to form layers around the structure.

If these "nanostructures" were incorporated into a gel, they could be placed into the gaps between bone fractures, and perhaps improve healing.

Their microscopic fibres, resembling the collagen fibrils in real bone, were each 10,000 times smaller than the width of a human hair.

However, when exposed to calcium and phosphate ions - the building materials for bone growth - the fibres were covered with crystalline deposits forming in exactly the same way as in the body.

The deposits grew on the fibres in the same direction - parallel to the length of the fibre - just as in the human body.

'Big frontier'

Professor Samuel Stupp, who led the study, said: "Regenerative medicine is a big frontier.

"Ideally we want the body to heal itself, in this case to repair bone by encouraging mineralised material to grow on a fibrous scaffold that the body would interpret as natural.

"Nature uses organic and inorganic materials to build systems with certain properties - such as strong bones.

"Our system of self-assembly is modelled on nature. These fibres are cell-friendly - cells like to grow on them."

Wide benefits

It is not simply those with broken bones who could benefit if the process is developed into a treatment.

Many other patients, such as those with bone cancer, or those having hip replacements, need to heal gaps in their bone structure - and these molecules could form a more effective building block.

In addition, it may be possible to develop structures that attract other cells - not just bone cells.

In theory, altering the formulation could bring other cells, such as nerve, cartilage, liver and pancreas - which provides potential for ways to regenerate other damaged tissues in the body.

Professor Lia Addadi, an expert in structural biology at the Weizmann Institute of Science in Israel, acclaimed it as a "major achievement".

"The unique quality of Professor Stupp and his group is the ability to fabricate novel and imaginative macromolecules that self-assemble into new materials."

A British Expert, Professor Steve Howdle from the University of Nottingham, said that it was "impressive research".

He told BBC News Online: "The problem at the moment is that people are trying to create artificial materials that match the strength of bone.

"The best they've come up with so far is stainless steel - which obviously isn't ideal for a number of reasons.

"It's possible that a new material may come out of this approach."