The effect of pore size on permeability and cell attachment in collagen scaffolds for tissue engineering

TLDR

Scaffold permeability governs nutrient and waste diffusion and internal pressure fields in tissue engineering constructs. This study aimed to quantify how pore size and compressive strain affect the permeability of collagen‑GAG scaffolds using experimental measurements and mathematical modeling. Four scaffold variants with mean pore sizes of 151, 121, 110, and 96 µm were freeze‑dried, and an in‑house device measured their permeability at 0, 14, 29, and 40 % strain while a low‑density open‑cell foam model with a tetrakaidecahedral unit cell simulated permeability across all strains. Permeability increased with pore size and decreased with strain, and the close match between measured and predicted values demonstrates that cellular‑solids modeling can reliably predict scaffold permeability under physiological loading and for future designs.

Abstract

The permeability of scaffolds and other three-dimensional constructs used for tissue engineering applications is important as it controls the diffusion of nutrients in and waste out of the scaffold as well as influencing the pressure fields within the construct. The objective of this study was to characterize the permeability/fluid mobility of collagen-GAG scaffolds as a function of pore size and compressive strain using both experimental and mathematical modeling techniques. Scaffolds containing four distinct mean pore sizes (151, 121, 110, 96 microns) were fabricated using a freeze-drying process. An experimental device was constructed to measure the permeability of the scaffold variants at different levels of compressive strain (0, 14, 29 and 40% while a low-density open-cell foam cellular solids model utilizing a tetrakaidecahedral unit cell was used to accurately model the permeability of each scaffold variant at all level of applied strain. The results of both the experimental and the mathematical analysis revealed that scaffold permeability increases with increasing pore size and decreases with increasing compressive strain. The excellent comparison between experimentally measured and predicted scaffold permeability suggests that cellular solids modelling techniques can be utilized to predict scaffold permeability under a variety of physiological loading conditions as well as to predict the permeability of future scaffolds with a wide variety of pore microstructures.