Materials Science

Grow with the Flow

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Science  25 Feb 2011:
Vol. 331, Issue 6020, pp. 989
DOI: 10.1126/science.331.6020.989-c

Formation of the mineral component of bone occurs through an amorphous precursor, which is stabilized by a number of proteins. Maas et al. show that they can form collagen fibrils that incorporate calcium phosphate directly. They flowed an acidic feed solution containing calcium cations and monomolecular tropocollagen through a polycarbonate track-etched membrane into a basic solution containing phosphate anions. The change in acidity caused the tropocollagen to self-assemble into triple helix collagen fibrils. At the same time, the combination of the calcium and phosphate ions led to the formation of amorphous CaP, which was incorporated into the inside of the fibrils and could form overgrowths on the outside of the fibrils at higher concentrations. The authors seeded the mineralized fibrils with human adipose–derived stem cells and found that the inclusion of calcium phosphate enhanced cell proliferation. These cells also showed an increase in alkaline phosphatase activity, which is an early indicator of bone cell differentiation, suggesting that this mineralized collagen could be used for in situ bone healing.

Nano Lett. 11, 10.1021/nl200116d (2011).

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