The effect of processing variables on morphological and mechanical properties of supercritical CO2 foamed scaffolds for tissue engineering

The porous structure of a scaffold determines the ability of bone to regenerate within this environment. In situations where the scaffold is required to provide mechanical function, balance must be achieved between optimizing porosity and maximizing mechanical strength. Supercritical CO₂ foaming can produce open-cell, interconnected structures in a low-temperature, solvent-free process. In this work, we report on foams of varying structural and mechanical properties fabricated from different molecular weights of poly(dl-lactic acid) P_dlLA (57, 25 and 15 kDa) and by varying the depressurization rate. Rapid depressurization rates produced scaffolds with homogeneous pore distributions and some closed pores. Decreasing the depressurization rate produced scaffolds with wider pore size distributions and larger, more interconnected pores. In compressive testing, scaffolds produced from 57 kDa P_dlLA exhibited typical stress-strain curves for elastomeric open-cell foams whereas scaffolds fabricated from 25 and 15 kDa P_dlLA behaved as brittle foams. The structural and mechanical properties of scaffolds produced from 57 kDa P_dlLA by scCO₂ ensure that these scaffolds are suitable for potential applications in bone tissue engineering.