Macroporous biphasic calcium phosphate scaffold with high permeability/porosity ratio

Macroporous biphasic calcium phosphate (BCP) with channel-shaped pores was produced by a novel dual-phase mixing method. The processing route includes mixing water-based BCP slurry and polymethylmethacrylate resin; shaping in a mold; and polymerization, drying, pyrolyzing, and sintering. After comparison with two other commercial macroporous BCP materials, which were produced along different routes, it was found that conventional parameters such as porosity and pore size cannot describe a macroporous structure precisely enough for the application as tissue-engineering scaffold. Instead, permeability can be seen as an intrinsic and quantitative parameter to describe the macroporous structure of various scaffolds, because it is independent of sample size and fluid used in the test. Another parameter, the permeability/porosity ratio, provides an indication of the percolative efficiency per unit porous volume of a scaffold. Structural characterizations and permeability studies of other macroporous scaffold materials were also performed, and it was found that permeability could reflect a combination of five important parameters for scaffold: (1) porosity, (2) pore size and distribution, (3) interconnectivity, (4) fenestration size and distribution, and (5) orientation of pores. Finally, the implications of relating permeability with biological performances are also discussed.