Extrusion-based bioprinting for functional tissue reconstruction: design strategies and applications

Extrusion-based bioprinting has become a widely used biofabrication strategy for tissue engineering because it enables controlled deposition of cell-laden bioinks, biomaterials, and bioactive factors into spatially organized constructs. In this review, we summarize the principles of extrusion-based bioprinting, including major printing configurations, emerging variants, bioink classifications, and key design criteria related to printability, rheology, crosslinking, and post-printing stability. We then discuss recent applications through a function-oriented framework, covering load-bearing structural tissues, barrier and soft connective tissues, contractile tissues, metabolically active parenchymal tissues, vascularized constructs, and neural tissue regeneration. This framework emphasizes that successful bioprinting requires not only anatomical shape reproduction, but also reconstruction of tissue-specific functions, including mechanical support, barrier restoration, vascular perfusion, contractility, metabolic activity, and neural connectivity. We further analyze major challenges, including the trade-off between bioink processability and biological performance, cell viability and structural fidelity, limited multiscale resolution, functional maturation, host integration, and regulatory standardization. Finally, we outline future directions involving dynamic bioinks, AI-assisted process control, hybrid multiscale fabrication, bioreactor-based maturation, and clinically compatible manufacturing workflows.