From Printability to Biofunctionality: 3D-Printed Hydrogel Scaffolds for Multi-Tissue Engineering.

3D-printed hydrogel scaffolds have emerged as important platforms in tissue engineering and regenerative medicine owing to their extracellular matrix-like three-dimensional hydrated networks, tunable physicochemical properties, and ability to spatially organize cells, bioactive factors, and scaffold architectures. Early studies mainly focused on the printability, shape fidelity, and biocompatibility of hydrogel inks, whereas current research has gradually shifted toward the construction of bioactive scaffolds with tissue-specific functions. Because different tissues exhibit distinct requirements in terms of mechanical properties, cellular microenvironment, vascularization, innervation, degradation behavior, and functional maturation, the design of 3D-printed hydrogel scaffolds should comprehensively consider material composition, printing strategy, biofactor delivery, and tissue-specific functional demands. In this review, we focus on the transition from printability to biofunctionality and systematically summarize recent advances in 3D-printed hydrogel scaffolds for multi-tissue engineering. Particular emphasis is placed on regenerative applications of 3D-printed hydrogel scaffolds in bone, cartilage, vascular, neural, and skin tissue engineering. Finally, we discuss the major challenges associated with 3D-printed hydrogel scaffolds and further highlight future directions. This review aims to provide a systematic reference for the functional design and application of 3D-printed hydrogel scaffolds in multi-tissue engineering.