Sea Urchin Skeletons Help Researchers Bone Up on Biomaterials


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By examining the processes in a sea urchin's early skeletal formation, a UC Berkeley researcher, along with scientists from other institutions, may have shed light on how biomaterials are naturally formed.

The study, which was spearheaded by scientists from the University of Wisconsin-Madison and the Weizmann Institute of Science in Israel, discovered a new transitional phase in urchin development.

The report, which was published on Oct. 27 in the Proceedings of the National Academy of Sciences journal, found that urchin larvae transform calcium carbonate in its amorphous form into the more regular, crystalline structure of calcite.

The urchin may now help scientists understand more about how biomaterials form in order to reproduce the process to create new biomaterials.

Researchers looked at California purple sea urchin larvae spicules-tiny skeletal structures 5 microns in diameter and 50 to 100 microns long.

"What we did was to extract and purify these little tiny spicules. They are very small ... like little needles," said Fred Wilt, UC Berkeley professor of molecular and cell biology and author of the study. "(Its structure) is arranged like tent poles inside the larvae."

The scientists were then able to see the changes the bone structure underwent by analyzing the bone's absorption spectrum, which allowed them to determine the chemical makeup of the spicule.

"When amorphous, the shape of the spectrum is different compared to that of calcite and we've also been able to analyze the exact same spicule 10 months later and saw the spicule that were amorphous became crystalline," said Pupa Gilbert, physics professor at University of Wisconsin-Madison and lead researcher of the study. "It's completely disordered when it's amorphous and then it becomes crystalline with all the atoms in regular lattice, in a crystalline state."

Contrary to what researchers had expected, they discovered that the transformative state from calcium carbonate to calcite was not uniform.

"Instead of having a massive propagation arm, it sort of propagates like thunder through air or a liquid through a porous medium," Gilbert said. "It follows a random walk for a fractal network."

Rather, the transitional state was a mixture between the amorphous and crystalline states.

"One of the other things pointed out here is the amorphous form and transition form and pure crystalline form are all mixed up into each other. It is a mystery of how one thing is converted into another, so it brings up another set up of questions about how they are converted," Wilt said.

This new discovery of a transient phase between amorphous and crystalline states lends scientists clues about how to create hard biomaterials like bones or teeth.

"I think there are going to be future applications, but a lot of this is trying to get an understanding of how organisms make hard materials. How do organisms make hard things-bones, teeth, spicules in this case," Wilt said. "They are not able to duplicate these materials so there is a lot of interest in understanding more about the fundamentals of how this is done. This study shows a transition that was unexpected and will figure into how applications into biology of how these materials are made."


Contact Christine Chen at [email protected]

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