Additive manufacturing of the core template for the fabrication of an artificial blood vessel: the relationship between the extruded deposition diameter and the filament/nozzle transition ratio

Preparation and Evaluation of RGD-Conjugated Crosslinked PVA Tissue Engineered Vascular Scaffold with Endothelial Differentiation and Its Impact on Vascular Regeneration In Vivo

PVA has emerged as a prevalent material for the construction of vascular tissue engineering scaffolds. Nonetheless, the integration of 3D crosslinked polyvinyl alcohol (PVA) scaffolds featuring arginine-glycine-aspartate (RGD) binding remains a rarity in tissue engineering. In the present study, a PVA-4-azidobenzoic acid (AZ)-RGD scaffold is prepared based on cross-linking of two distinct PVA derivatives: one featuring photoreactive azides for ultraviolet (UV)-crosslinking and the other incorporating RGD peptides. The results show that the PVA-AZ-RGD scaffold has good blood compatibility and biomechanical properties, with hydrophilic properties, and a hydrolysis rate of 27.31% at 12 weeks. Notably, the incorporation of RGD peptides significantly bolsters the attachment and proliferation of mesenchymal stem cells (MSCs) on the scaffolds, compared to non-RGD-conjugated controls. Furthermore, RGD conjugation markedly accelerates endothelialization of MSCs following 15 days of endothelial culture. Post-transplantation, the PVA-AZ-RGD scaffold exhibits favorable blood flow patency, minimal immune rejection, promotes endothelialization and smooth muscle cell proliferation, and facilitates the development of extracellular matrix, ultimately contributing to the formation of regenerative artificial blood vessels. These comprehensive findings underscore the promising potential of RGD-integrated, crosslinked PVA scaffolds for applications in vascular tissue engineering.

Three-dimensional customized artificial grafts functionalized with biomimetic softness and anticoagulant heparin-dopamine surface modification: Preclinical study for practical applications

Artificial vascular grafts, as blood vessel substitutes, are a prime challenge in tissue engineering and biomaterial research. An ideal artificial graft must have physiological and mechanical properties similar to those of a natural blood vessel, and hemocompatibility on its surface. We designed and fabricated artificial grafts by applying 3D printing and templated technology, which is endowed with morphologically patient-specific vascular reconstruction. To optimize mechanical properties, the graft wall was engineered with a controllable hybrid porous structure through a multilayer combination of porous and nonporous coatings, thereby achieving biomimetic mechanical flexibility with reduced stiffness. Further, we successfully synthesized dopamine-conjugated heparin (Hep-DA) utilizing carbodiimide chemistry, and coated it on a 3D porous graft to improve both surface adhesion and anticoagulant ability. The Hep-DA-coated 3D graft did not show significant cytotoxic effects with a long-term sustained heparin release. We performed a preclinical study in swine using the developed graft along with commercially available graft ePTFE and Dacron as a reference. They were implanted in the swine aorta for 28 days and the implanted grafts were harvested for further analysis. Histopathology study results showed the feasibility of the developed artificial vascular grafts that have less calcification, fibrosis, and collagen deposition than commercially available grafts.

New Method for Preparing Small-Caliber Artificial Blood Vessel with Controllable Microstructure on the Inner Wall Based on Additive Material Composite Molding

The diameter of most blood vessels in cardiovascular and peripheral vascular system is less than 6 mm. Because the inner diameter of such vessels is small, a built-in stent often leads to thrombosis and other problems. It is an important goal to replace it directly with artificial vessels. This paper creatively proposed a preparation method of a small-diameter artificial vascular graft which can form a controllable microstructure on the inner wall and realize a multi-material composite. On the one hand, the inner wall of blood vessels containing direct writing structure is constructed by electrostatic direct writing and micro-imprinting technology to regulate cell behavior and promote endothelialization; on the other hand, the outer wall of blood vessels was prepared by electrospinning PCL to ensure the stability of mechanical properties of composite grafts. By optimizing the key parameters of the graft, a small-diameter artificial blood vessel with controllable microstructure on the inner wall is finally prepared. The corresponding performance characterization experimental results show that it has advantages in structure, mechanical properties, and promoting endothelialization.

Freeform 3D printing of vascularized tissues: Challenges and strategies

In recent years, freeform three-dimensional (3D) printing has led to significant advances in the fabrication of artificial tissues with vascularized structures. This technique utilizes a supporting matrix that holds the extruded printing ink and ensures shape maintenance of the printed 3D constructs within the prescribed spatial precision. Since the printing nozzle can be translated omnidirectionally within the supporting matrix, freeform 3D printing is potentially applicable for the fabrication of complex 3D objects, incorporating curved, and irregular shaped vascular networks. To optimize freeform 3D printing quality and performance, the rheological properties of the printing ink and supporting matrix, and the material matching between them are of paramount importance. In this review, we shall compare conventional 3D printing and freeform 3D printing technologies for the fabrication of vascular constructs, and critically discuss their working principles and their advantages and disadvantages. We also provide the detailed material information of emerging printing inks and supporting matrices in recent freeform 3D printing studies. The accompanying challenges are further discussed, aiming to guide freeform 3D printing by the effective design and selection of the most appropriate materials/processes for the development of full-scale functional vascularized artificial tissues.