Factors affecting the structure and properties of bioactive foam scaffolds for tissue engineering

Resorbable 3D macroporous bioactive scaffolds have been produced for tissue-engineering applications by foaming sol-gel-derived bioactive glasses of the 58S (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) composition with the aid of a surfactant. Bioactive glasses are known to have the ability to regenerate bone, and to release ionic biological stimuli that promote bone-cell proliferation by gene activation. The foams exhibit a hierarchical structure, with interconnected macropores (10-500 microm), which provide the potential for tissue ingrowth and mesopores (2-50 nm), which enhance bioactivity and release of ionic products. Many factors in the sol-gel and foaming processes can be used to control these pore sizes and distributions. This work concentrates on the effect of the processing temperature, gelling agent concentration, and the amount of water used for the foam generation on the structure, pore morphology, and the properties of the foam scaffold. The simplest and most reproducible method for controlling the modal pore diameter was by the amount of water added during the foaming process. The in vitro dissolution and bioactivity of the bioactive foams were compared to that of unfoamed monoliths and powders (< 20 microm in diameter) of the same composition.