An endothelial cell (EC) monolayer aligned along the direction of blood flow in vivo shows excellent capacity for anti-inflammation and anti-thrombosis. Therefore, aligned electrospun fibers have been much studied in the field of vascular implants since they are considered to facilitate the formation of an aligned EC monolayer, yet few research studies have been comprehensively reported concerning the effects of diameter scales of aligned fibers. In the present work, a series of aligned polycaprolactone (PCL) electrospun fibers with varying diameters ranging from dozens of nanometers to several micrometers were developed, and the effects of the fiber scales on EC behaviors, hemocompatibility as well as inflammatory cell behaviors were investigated, to evaluate their potential performance in the field of vascular implants. Our results showed that platelets exhibited small attachment forces on all fibers, and the anticoagulation property improved with the decrease of the fiber diameters. The impact of fiber diameters on human umbilical vein endothelial cell (HUVEC) adhesion and NO release was limited, while significant on HUVEC proliferation. With the increase of the fiber diameters, the elongation of HUVECs on our samples increased first then decreased, and exhibited maximum elongation degrees on 2738 nm and 2036 nm due to the strong contact guidance effect on these graphical cues; too thick or too fine fibers would weaken the contact guidance effect. Furthermore, we hypothesized that HUVECs cultured on 2036 nm had the smallest spreading area because of their elongation, but 2738 nm restricted HUVECs spreading limitedly. Similarly, NO production of HUVECs showed a similar change trend as their elongation degrees on different fibers. Except for 2036 nm, it exhibited the second highest NO production. For RAW 264.7 cells, poorer cell adhesion and lower TNF-α concentration of 1456 nm indicated its superior anti-inflammation property, while 73 nm showed a contrasting performance. Overall, these findings partly revealed the relationship between different topographies and cell behaviors, providing basic insight into vascular implant design.

Acute thrombosis remains the main limitation of small-diameter vascular grafts (inner diameter <6 mm) for bridging and bypassing of small arteries defects and occlusion. The use of hydrogel tubes represents a promising strategy. However, their low mechanical strength and high swelling tendency may limit their further application. In the present study, a hydrogel vascular graft of Ca alginate/polyacrylamide reinforced with a braided fiber strut was designed and fabricated with the assistance of a customized casting mold. Morphology, structure, swellability, mechanical properties, cyto- and hemocompatibility of the reinforced graft were characterized. The results showed that the reinforced graft was transparent and robust, with a smooth surface. Scanning electron microscopic examination confirmed a uniform porous structure throughout the hydrogel. The swelling of the reinforced grafts could be controlled to 100%, obtaining clinically satisfactory mechanical properties. In particular, the dynamic circumferential compliance reached (1.7 ± 0.1)%/100 mmHg for 50–90 mmHg, a value significantly higher than that of expanded polytetrafluoroethylene (ePTFE) vascular grafts. Biological tests revealed that the reinforced graft was non-cytotoxic and had a low hemolysis percentage (HP) corresponding to (0.9 ± 0.2)%. In summary, the braided fiber-reinforced hydrogel vascular grafts demonstrated both physical and biological superiority, suggesting their suitability for vascular grafts.

A PVA/PAAm (polyvinyl alcohol/polyacrylamide) hydrogel vascular graft reinforced by a braided fiber stent was prepared in the present work, and a series of characterizations were carried out for evaluating the comprehensive performance of the reinforced hydrogel vascular graft (RHVG), including the morphology, the mechanical properties and the biocompatibility. The results show that hydrogel with a mass ratio of 5:8 (PVA:PAAm) is the best candidate for developing an implantation-oriented vascular graft, whose overall performance is the closest to the requirements of clinical applications. The surface of the PVA/PAAm hydrogel is smooth, and the porous structure is uniform and stable. When the longitudinal strain of the RHVG was 50%, the tensile strength reached 905.6 ± 63.1 kPa, much higher than that of a swine common carotid artery (185 kPa). Moreover, the circumferential tensile strength was significantly enhanced by the integration of the stent, and the circumferential compression recovery reached 93.4 ± 6.7%, showing satisfactory structural stability. Furthermore, the suture retention force approached (9.89 ± 0.64 N), higher than that of a canine femoral artery (7.90 ± 0.36 N). More importantly, the radial dynamic compliance reached 3.11 ± 0.09% under testing pressure of 80–120 mmHg, which is 6.9 times that of a commercial expanded polytetrafluoroethylene vascular graft. Lastly, the RHVG has satisfying cytocompatibility and a low hemolysis rate. In summary, the present work may pave the way for developing a novel small-diameter vascular graft for clinical implantation.

Water permeability of textile vascular grafts has been considered as a key indicator for predicting blood permeability after implantation. However, a correlation between water and blood permeability has not been established yet. Therefore, even though the water permeability of a vascular graft can be tested according to the standard ISO 7198, the results fail to guide a manufacturer or a surgeon to judge whether this vascular graft needs pre-clotting or not prior to implantation. As a result, all commercial graft products show almost zero water permeability, which leads to the loss of advantages that textile vascular grafts have the pore size-controlled porous wall. To solve this problem, four types of woven vascular grafts were designed and manufactured in the present work. Then their permeability to water, simulated plasma, and anticoagulated whole blood were measured at graded pressures from 8 to 16 kPa. Moreover, the correlations among the water permeability, the simulated plasma permeability, and the anticoagulated whole blood permeability were established. The results suggest that relatively steady correlations exist between the water permeability and the anticoagulated whole blood permeability, and that the evaluation of the blood permeability using the water permeability is feasible and objective. The present work provides a quantitative method for evaluating the blood permeability using the water permeability, and the latter is thus endowed with practical significance for guiding designs and clinical pre-clotting operations of textiles vascular grafts.