Nanocrystals Show How Bones Grow

How tiny atoms group together and solidify into bone, the tough but lightweight tissue that makes up our skeletons and protects our vital organs, has long eluded scientists.

Now the world's most advanced electron microscope has revealed that the formation of biominerals, like bone and teeth shells, begins with a small cluster of about ten ions, or charged particles smaller than a nanometer (a billionth of a meter).

Researchers prepared a solution of inorganic calcium carbonate in the lab, these clusters assembled in solution to form disorganized groups of ions about 30 nanometers wide formed.

When this random ensemble rose to an organic "surface" provided by the scientists, the clusters began to crystallize and grow into minerals.

Eventually one big crystal about a hundred nanometers wide emerged (pictured, a false-color image of the cluster at several micrometers wide).

"The finding is, it's not ions, but these clusters, that makes a difference in how organic and inorganic materials interact," said study lead author Nico Sommerdijk of the Eindhoven University of Technology in the Netherlands.

The experiment simulated the creation of a shell rather than a human bone, which is made of calcium phosphate, not carbonate. But Sommerdijk said both processes should work "roughly the same way."

Understanding bone genesis can help scientists mimic the "beautiful strategies that nature uses to make strong and precise materials," said Sommerdijk, whose study appeared in a recent issue of the journal Science.

For instance, synthetic, bonelike materials grown in a lab could be used for bone replacements in people. Construction materials, such as heavy concrete, could also be made from bone-inspired products.

"If we could make something that would be a third of the weight but the same properties mechanically, that would be a really big advancement," Sommerdijk said.