Glass, Ceramic, Polymeric, and Composite Scaffolds with Multiscale Porosity for Bone Tissue Engineering

Porosity affects performance of scaffolds for bone tissue engineering both in vitro and in vivo. Macropores (i.e., pores with a diameter >100 μm) are essential for cellular infiltration; micropores (i.e., pores with a diameter of 1–10 μm) promote cell adhesion and facilitate nutrient absorption. Scaffolds containing both macropores and micropores exploit the advantages of both pore sizes and have excellent osteogenic properties. Nanopores (i.e., pores with a diameter of 1–50 nm) can be included as well, to improve cell–material interactions by further enhancing the surface area of the scaffold. This article reviews fabrication techniques and properties of scaffolds with multiscale porosity, focusing on glass, ceramic, polymeric, and composite scaffolds. After discussing the structure of bone and how it inspired scaffolds for bone tissue engineering, pore nomenclature is introduced. Then, the techniques used to induce multiscale porosity, the nature of the pores created, and the effects of scaffold porosity on mechanical properties and biological activity of the scaffolds are discussed. The review concludes by providing an outlook for this field, including advancements that are made possible by computational modeling and artificial intelligence.