Ice-templating of anisotropic structures with high permeability

- Anisotropic scaffolds were made from a recombinant peptide based on collagen.
- Ice-templated scaffold pore size was a function of the ice growth velocity.
- Scaffold permeability was related to pore size via a power law.
- Cell migration through scaffolds scales with the scaffold permeability.

Nutrient diffusion and cellular infiltration are important factors for tissue engineering scaffolds. Maximizing both, by optimizing permeability and scaffold architecture, is important to achieve functional recovery. The relationship between scaffold permeability and structure was explored in anisotropic scaffolds from a human collagen I based recombinant peptide (RCP). Using ice-templating, scaffold pore size was controlled (80-600 μm) via the freezing protocol and solution composition. The transverse pore size, at each location in the scaffold, was related to the freezing front velocity, via a power law, independent of the freezing protocol. Additives which interact with ice growth, in this case 1 wt% ethanol, altered ice crystallization and increased the pore size. Variations in composition which did not affect the freezing, such as 40 wt% hydroxyapatite (HA), did not change the scaffold structure, demonstrating the versatility of the technique. By controlling the pore size, scaffold permeability could be tuned from 0.17 × 10− 8 to 7.1 × 10− 8 m2, parallel to the aligned pores; this is several orders of magnitude greater than literature values for isotropic scaffolds: 10− 9-10− 12 m2. In addition, permeability was shown to affect the migration of osteoblast-like cells, suggesting that by making permeability a design parameter, tissue engineering scaffolds can promote better tissue integration.

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