(n)certainties – Die Angewandte – Fall 2008

Biomineralisation is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. These minerals often form structural features such as sea shells and the bone in mammals and birds.

The aim is to manage a chemical synthesis to create a biomineral. The technique took its cue from the sea sponges silica formation process.

keywords: biomineralization/demineralization; biosilicification; crystal engineering; molecular self-assembly; collagen; sponges-silica formation.

article: “Silicon and Sun” by Kevin Bullis, Technology Review – MIT press, november 01, 2006

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The sponge’s method is particularly elegant. Sitting on the seabed thousands of meters below the surface of the western Pacific, the sponge extracts silicic acid from the surrounding seawater. It converts the acid into silicon dioxide–silica–which, in a remarkable feat of biological engineering, it then assembles into a precise, three-dimensional structure that is reproduced in exact detail by every member of its species.
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So Morse and his colleagues began by isolating the genetic code for one of the proteins–which as a family they came to call “silicateins”–and ran their results through a huge database of known proteins. They weren’t expecting a match, but they found one–immediately. The protein was similar to a protease, an enzyme found in the human intestine that is involved in the breakdown and digestion of food.
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It actively produces building materials such as silicon oxide–in a sense, by digesting compounds in the seawater–and then causes the materials to line up along its length to form the needle-shaped glass of the sponge skeleton.
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The sponge’s secret, they discovered, was that amine and hydroxyl chemical groups in the enzyme produce the silicon oxide and assemble it in the required way. That meant that all the chemicals a new synthesis technique would require could be found in ammonia and water. The researchers found that by mixing molecules containing the metal oxides’ precursors into water, and then exposing the mixture to ammonia gas, they could create thin films of highly crystalline semiconductors–materials…

he is also interested in creating laminated fibers for ultrastrong building materials.