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Electron Microscope Captures 3-Dimensional Image of Nanoparticles at Onset of Biomineralisation

Published on May 14, 2009 at 10:32 AM

Researchers at Eindhoven University of Technology (TU/e) for the first time have shown the earliest stages in biomineralisation, the process that leads to the formation of bones, teeth and sea shells. They used the world's most modern electron microscope to capture a three-dimensional image of the nanoparticles that form the basis for this process. The results provide a greater understanding of the formation of bones, teeth and shells. This creates a prospect of better materials and processes for industry, based on nature. The findings featured as the cover story for the scientific journal Science on Friday 13 March.

The researchers, led by Vidi laureate Dr Nico Sommerdijk, managed to image small clusters, with a diameter of 0.7 nanometers, in a solution of calcium carbonate, (the basic material of shells, for example). They were the first to show that these clusters, containing no more than about ten ions, were the start of the growth process from which the crystalline biomineral is ultimately formed.

To do this, they used the extremely high resolution of a special electron microscope, the FEI Company's cryoTitan. The equipment was acquired with the assistance of a NWO Large Investment grant for the TU/e and Maastricht University. It allowed them to be the first in their field to see how the clusters nucleated into larger, unstructured nanoparticles with an average diameter of about 30 nanometers.

Three-dimensional imaging revealed that an organic surface introduced by the researchers allowed these nanoparticles to grow into larger particles, in which crystalline areas could be formed later, through structuring of the ions. The TU/e researchers demonstrated a second role for the organic layer: it directed quite precisely the direction in which the mineral could grow into a mature biomineral. In the near future they hope to show that the mechanism they have discovered also applies to the formation of other crystalline biominerals, and perhaps even to other inorganic materials.

This is important for research into the growth of bones and substitute bone material. The work might also be used in nanotechnology, to direct the growth of nanoparticles in the same way as appears to happen in nature: through a subtle interplay of organic and inorganic materials.

About biomineralisation

Biomineralisation is the formation of inorganic materials in a biological environment, familiar from bones, teeth and shells. The formation of the mineral is quite precisely directed here by specialised organic biomolecules, such as sugars and proteins. While the underlying mechanisms have long been a subject of study, there are still many mysteries in the details of this process.

One commonly followed strategy is to use 'biomimetic' studies, where the biomineralisation process is mimicked with a simplified system in the laboratory. This allows individual parts of the mineralisation process to be studied.

Using this approach, as well as the electron microscope mentioned above, Sommerdijk's research group at the TU/e Faculty of Chemical Technology managed to capture images of the earliest stages of this type of biomimetically led mineralisation reaction. Nico Sommerdijk undertook this work with a Vidi grant from NWO The cryoTEM equipment was partly financed with a NWO Large Investment grant.

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