Coaxial 3D printing of SA/PVA/gelatin composite small-diameter vascular grafts: Mechanical reinforcement and fluid-structure interaction analysis

The high prevalence of cardiovascular diseases has generated a pressing clinical need for small-diameter vascular grafts (<6 mm). However, their clinical translation remains constrained by several challenges, such as suboptimal mechanical properties, thrombotic risks, and limited long-term patency. Moreover, conventional experimental approaches often fail to fully capture the mechanical behavior of grafts under physiologically dynamic blood flow. In this study, artificial vascular grafts with an inner diameter of approximately 2.8 mm were fabricated using coaxial 3D printing technology. We report, for the first time, the integration of gelatin into a sodium alginate (SA)/polyvinyl alcohol (PVA) composite bioink to overcome the inherently poor cell adhesion of conventional SA/PVA scaffolds. The incorporation of gelatin not only significantly enhanced the grafts' hydrophilicity and mechanical properties (including tensile strength and elastic modulus) but also provided intrinsic RGD sequences that actively promote the adhesion and proliferation of endothelial cells. The mechanical performance of the grafts was further improved through cyclic freeze-thaw treatment. Fluid–structure interaction (FSI) finite element simulations were conducted to simulate the hemodynamic environment, analyzing stress–strain distribution and structural stability under flow conditions. Experimental results indicated that the addition of gelatin improved tensile strength and elastic modulus, rendered the material superhydrophilic, and enhanced cell adhesion. Simulations demonstrated that under physiological flow velocities, the maximum wall stress and overall deformation rate of the graft complied with clinical standards. In vitro assays confirmed the material’s excellent hemocompatibility and its capacity to promote endothelial cell proliferation. Download: Download high-res image (267KB) Download: Download full-size image Preparation of the bioink and crosslinking agent; b: Setup and process of coaxial 3D printing; c: Schematic of the cell adhesion mechanism (left and right panels represent gelatin-incorporated and gelatin-free vascular graft materials, respectively).