Applications and progress of 3D printed bioceramic scaffolds in bone tissue repair and immune regulation

The objective of bone tissue engineering is to develop materials and techniques that can repair large segmental bone defects by locally adding bioactive materials in precise configurations. This field has advanced significantly since the introduction of scaffold materials, requiring breakthroughs in materials science, biomechanics, biomedical engineering, and regenerative medicine. 3D printing technology, due to its precision and customization capabilities, has gained prominence in creating personalized scaffolds that enhance bone healing and modulate immune responses. The review delves into the mechanisms of bone injury healing, highlighting the crucial role of the immune system and macrophage polarization in the healing process. It covers various 3D printing techniques, including extrusion-based 3D printing (EP), fused deposition modeling (FDM), and light curing 3d printing, discussing their suitability for fabricating complex scaffold structures. The materials discussed include calcium phosphate ceramics, silicate ceramics, and ceramic/polymer and ceramic/metal composites. Key factors influencing the immune regulatory functions of these scaffolds, such as surface nano-structures, pore size and porosity, surface charge, and the release of metal ions, are examined. Despite significant advancements, challenges remain in clinical applications, including issues with raw materials, high-temperature shrinkage, printing precision, structural stability, and immune regulation. Future research directions involve improving material selection, optimizing scaffold design, and leveraging advanced 3D printing technologies to enhance the biocompatibility, bioactivity, and mechanical properties of bioceramic scaffolds. This review provides a comprehensive understanding of current progress and future prospects in the field of 3D printed bioceramic scaffolds for bone tissue repair and immune regulation.