Synthetic vascular grafts suitable for small-diameter arteries (<6 mm) are in great need. However, there are still no commercially available small-diameter vascular grafts (SDVGs) in clinical practice due to thrombosis and stenosis after in vivo implantation. When designing SDVGs, many studies emphasized reendothelization but ignored the importance of reconstruction of the smooth muscle layer (SML). To facilitate rapid SML regeneration, a high-resolution 3D printing method was used to create a novel bilayer SDVG with structures and mechanical properties mimicking natural arteries. Bioinspired by the collagen alignment of SML, the inner layer of the grafts had larger pore sizes and high porosity to accelerate the infiltration of cells and their circumferential alignment, which could facilitate SML reconstruction for compliance restoration and spontaneous endothelialization. The outer layer was designed to induce fibroblast recruitment by low porosity and minor pore size and provide SDVG with sufficient mechanical strength. One month after implantation, the arteries regenerated by 3D-printed grafts exhibited better pulsatility than electrospun grafts, with a compliance (8.9%) approaching that of natural arteries (11.36%) and significantly higher than that of electrospun ones (1.9%). The 3D-printed vascular demonstrated a three-layer structure more closely resembling natural arteries while electrospun grafts showed incomplete endothelium and immature SML. Our study shows the importance of SML reconstruction during vascular graft regeneration and provides an effective strategy to reconstruct blood vessels through 3D-printed structures rapidly.

Lung diseases associated with alveoli, such as acute respiratory distress syndrome, have posed a long-term threat to human health. However, an in vitro model capable of simulating different deformations of the alveoli and a suitable material for mimicking basement membrane are currently lacking. Here, we present an innovative biomimetic controllable strain membrane (BCSM) at an air–liquid interface (ALI) to reconstruct alveolar respiration. The BCSM consists of a high-precision three-dimensional printing melt-electrowritten polycaprolactone (PCL) mesh, coated with a hydrogel substrate—to simulate the important functions (such as stiffness, porosity, wettability, and ALI) of alveolar microenvironments, and seeded pulmonary epithelial cells and vascular endothelial cells on either side, respectively. Inspired by papercutting, the BCSM was fabricated in the plane while it operated in three dimensions. A series of the topological structure of the BCSM was designed to control various local-area strain, mimicking alveolar varied deformation. Lopinavir/ritonavir could reduce Lamin A expression under over-stretch condition, which might be effective in preventing ventilator-induced lung injury. The biomimetic lung-unit model with BCSM has broader application prospects in alveoli-related research in the future, such as in drug toxicology and metabolism.

Because of the complex nerve anatomy and limited regeneration ability of natural tissue, the current treatment effect for long-distance peripheral nerve regeneration and spinal cord injury (SCI) repair is not satisfactory. As an alternative method, tissue engineering is a promising method to regenerate peripheral nerve and spinal cord, and can provide structures and functions similar to natural tissues through scaffold materials and seed cells. Recently, the rapid development of 3D printing technology enables researchers to create novel 3D constructs with sophisticated structures and diverse functions to achieve high bionics of structures and functions. In this review, we first outlined the anatomy of peripheral nerve and spinal cord, as well as the current treatment strategies for the peripheral nerve injury and SCI in clinical. After that, the design considerations of peripheral nerve and spinal cord tissue engineering were discussed, and various 3D printing technologies applicable to neural tissue engineering were elaborated, including inkjet, extrusion-based, stereolithography, projection-based, and emerging printing technologies. Finally, we focused on the application of 3D printing technology in peripheral nerve regeneration and spinal cord repair, as well as the challenges and prospects in this research field.

Inspired by natural porous architectures, numerous attempts have been made to generate porous structures. Owing to the smooth surfaces, highly interconnected porous architectures, and mathematical controllable geometry features, triply periodic minimal surface (TPMS) is emerging as an outstanding solution to constructing porous structures in recent years. However, many advantages of TPMS are not fully utilized in current research. Critical problems of the process from design, manufacturing to applications need further systematic and integrated discussions. In this work, a comprehensive overview of TPMS porous structures is provided. In order to generate the digital models of TPMS, the geometry design algorithms and performance control strategies are introduced according to diverse requirements. Based on that, precise additive manufacturing methods are summarized for fabricating physical TPMS products. Furthermore, actual multidisciplinary applications are presented to clarify the advantages and further potential of TPMS porous structures. Eventually, the existing problems and further research outlooks are discussed.