3D Printing-Assisted Interpenetrating-Phase Composite Implant Materials Integrating Structural-Functional Properties

Implant materials play a pivotal role in bone repair; however, existing materials face considerable challenges in simultaneously achieving adequate mechanical properties and biological functions. In this perspective, drawing inspiration from nature and leveraging 3D printing technologies, we propose a new strategy to achieve structural-functional integration through the development of bicontinuous interpenetrating-phase composite implant materials. These materials are fabricated by infiltrating one constituent into 3D-printed porous scaffolds of another, and demonstrate two potential degradation pathways after implantation - selectively partial degradation and sequentially complete degradation - depending on the types of constituents and their combinations. We elucidate the associated degradation behaviors, regulatory strategies, and the resulting biological functions, and analyze their underlying cellular and molecular mechanisms. Moreover, targeted functional integration and delivery can be realized by infiltrating hydrogels loaded with functional agents into 3D-printed scaffolds. The mechanical and functional properties of these materials can be deliberately modulated by selecting appropriate constituents and by designing and regulating the interpenetrating-phase structures. We further examine the challenges faced by these materials and outline prospective directions for future research. Distinct from conventional single-component materials, 3D printing-assisted composite implant materials hold significant promise for achieving structural-functional integration, thereby offering new opportunities to enhance bone repair efficacy.