Microalgae in 3D bioprinting and bone regeneration: Trends, applications, and future perspectives.

3D bioprinting has emerged as a powerful technology for bone tissue engineering, enabling the fabrication of complex, cell-laden structures with spatial precision. In recent years, microalgae have attracted growing attention in this field due to their unique photosynthetic ability, oxygen-generating capacity, and inherent bioactivities, which can enhance tissue regeneration and angiogenesis. This review systematically outlines the types of microalgae used in bone-related 3D bioprinting, their integration into bioinks and scaffolds, and the mechanisms through which they contribute to bone healing. Compared with previous literature, this review highlights underexplored dimensions such as the immunoregulatory properties of algal-derived scaffolds, the strategies to overcome their limited mechanical strength and immunogenicity, and the potential of genetic and material engineering to enhance clinical applicability. Furthermore, we discuss recent advancements in algal-laden scaffold sterilization methods-a critical but often overlooked aspect for clinical translation. A phenotypic-mechanistic integration framework and visual workflow diagrams are provided to aid material selection and design. Finally, we identify current limitations, research gaps, and future directions for utilizing microalgae as functional components in next-generation bioinks. These insights aim to promote the rational design of photosynthetically active and regenerative scaffolds for bone and soft tissue repair.