On the determination of Darcy permeability coefficients for a microporous tissue scaffold

Structural characterization of porous tissue scaffolds is challenging due to their complexity. Most investigators report the porosity of the material together with an estimate of the mean pore size and the pore size distribution. The usefulness of these measures is limited, especially in predicting the time-dependent permeation characteristics of a biodegradable, cell-seeded scaffold. A potential solution to this problem is to measure the permeability of the matrix and determine the Darcy permeability coefficient. Darcy permeability coefficients of 3.1 x 10(-14) and 6.3 x 10(-14) m(2) were measured for air and water, respectively, in microporous polycaprolactone scaffolds by monitoring fluid flow in response to a range of pressure differentials. Permeability coefficients for phosphate-buffered saline (5.3 x 10(-14) m(2)), glucose (5.7 x 10(-14) m(2)), and bovine serum albumin (1.8 x 10(-14) m(2)) were obtained by monitoring the change in concentration of molecular probes. This approach revealed the efficiency of transport of glucose molecules through the porous material and the existence of protein-scaffold interactions that resulted in protein retention and a reduction in fluid permeation rate. Darcy permeability measurements can provide valuable insights concerning the transport properties of nutrients, metabolites, and polypeptide growth factors in porous tissue engineering scaffolds and a method of quality assurance in scaffold processing.