Coaxial Bioprinting in Regenerative Medicine: Advances and Emerging Applications.

Coaxial extrusion-based bioprinting (EBB) is an emerging technology that enables the fabrication of biomimetic tissues with precise structural and biological complexities. This three-dimensional bioprinting technique utilizes specialized concentric nozzles to facilitate the simultaneous extrusion of distinct biomaterials, enabling the fabrication of layered constructs that closely resemble native tissues. Unlike traditional extrusion-based methods, coaxial printing allows for independent control over core and shell materials. This enables multimaterial integration, and tailored microenvironments that conventional extrusion methods cannot achieve. Recent technical innovations in coaxial EBB also include improved nozzle designs and bioink formulations, which have contributed to enhanced functional mimicry of native tissues and mechanical integrity of printed constructs. Coaxial EBB has demonstrated potential in spinal cord injury repair, perfusable small-diameter vessel engineering, accurate tumor microenvironment replication for oncology research, and complex organoid systems for personalized medicine. Despite these advancements, persistent challenges in coaxial EBB include maintaining cell viability under shear stress, optimizing bioink rheology, preventing nozzle clogging, and managing regulatory considerations. Future research directions involve the development of predictive computational models and the incorporation of innovative biomaterials for dynamic functionality. Addressing these challenges would allow the full therapeutic and clinical potential of coaxial bioprinting in regenerative medicine to be achieved. This review discusses and summarizes these advancements and limitations in coaxial EBB over the last decade, with an emphasis on applications in regenerative medicine.