The engineering of tissue interfaces presents a formidable challenge due to their intricate gradient structures marked by the gradual shift of biochemical and mechanical characteristics at the microscopic level, facilitating smooth interaction and synchronized operation between neighbouring yet distinct tissues. Examples of such interfaces include tendon/ligament-bone, muscle-tendon, and cartilage-bone. This review examines the heterogeneous and anisotropic architecture of anatomical tissues, highlighting the challenges associated with replicating these intricate structures. Additionally, it explores recent advancements in 3D bioprinting techniques aimed at fabricating complex, biomimetic scaffolds that enhance tissue regeneration and functional integration. 3D bioprinting has demonstrated the ability to accurately arrange chemical, biological, and mechanical signals within an integrated structure, effectively replicating these native tissue junctions. Major bioprinting approaches, such as inkjet, extrusion, laser-assisted, and stereolithography-based methods, are detailed in terms of their mechanisms, advantages, and limitations. Notable innovations, such as the use of advanced bioinks containing novel biomaterials such as decellularized extracellular matrix for various tissues, to enhance biomimicry and functionality, and the development of gradient scaffolds interfaces, are discussed. Furthermore, the review identifies current translational challenges and future directions, including the need for high-resolution bioprinters, the development of multiphasic scaffolds, and the incorporation of multiscale vascular networks into bioprinted tissues to ensure their viability and functionality post-transplantation. Overall, this review underscores the revolutionary impact of 3D bioprinting in the fabrication of functional, heterogeneous tissue constructs, emphasizing its role in driving advancements in tissue engineering and regenerative medicine.
