Waste-to-healthcare: eggshell-derived 4D-printed biphasic scaffolds for precision bone regeneration

Abstract Conventional bone tissue scaffolds are constrained by the issues of limited mechanical adaptability and inadequate bioactivity. Here, inspired by the natural bone tissue structure and combined with architectural design concepts, a multifunctional biphasic bone scaffold with a ‘steel-cement’ structure was constructed. This biphasic system was composed of a 4D printed rigid lattice metamaterial scaffold (‘biosteel’) and a flexible hydrogel (‘biocement’) loaded with composite particles (Cu-PDA-ES@Dex). Eggshell (ES) was innovatively used as a carrier to design composite particles with sequential drug release capabilities, which were embedded in the hydrogel phase to achieve synergistic anti-infective and osteogenic functions. By precisely regulating the geometric parameters of the lattice metamaterials, the mechanical properties and porosity of the scaffolds were controllably adjusted, thereby meeting the regeneration requirements of bone defects in different parts. The combination of radiopaque intelligent materials and 4D printing technology endowed the scaffolds with dynamic shape memory and radiopaque characteristics, facilitating minimally invasive implantation, adaptive filling, and precise localization. The ‘steel-cement’ multifunctional biphasic scaffold established an innovative platform for intelligent bone regeneration with its antibacterial, osteogenic, and mechanical adaptability. This not only promoted the development of bone regeneration toward intelligence and precision, but also provided new insights into the high-value utilization of waste biological resources.