Materials Science

Preparing Pores

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Science  11 Jun 2010:
Vol. 328, Issue 5984, pp. 1329
DOI: 10.1126/science.328.5984.1329-c

A challenge in making three-dimensional biomaterials or tissue scaffolds is the inclusion of a connected network of pores and channels to allow for fluid flow, cell migration, and the diffusion of gases, nutrients, and growth factors. Zawko and Schmidt have developed a simple procedure involving the crystallization of a small molecule within a polymeric gel. Once the crystal network has formed, the polymer is solidified via cross-linking and the crystals can be washed away. The authors focused on hyaluronic acid (HA), a biopolymer found in all tissues, and urea for the crystal network. Crystallization of the urea could be initiated at a single point, multiple points, or along a line. At low urea supersaturation a dendritic network formed, whereas for higher concentrations the crystals were more needle-like. When the density of the crystal branches was high, the HA polymerized into a fibrillar microstructure similar to the protein fibers found in extracellular matrix and basement membranes. The authors found that for a given polymer-crystal pair, the crystal template varied with molecular structure, solubility, degree of supersaturation, viscosity, and temperature, so that it should be possible to use this method for a wide range of cross-linkable gel materials.

Acta Biomater. 6, 2415 (2010).

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