Artificial Vascular Grafts Research Articles

Polycaprolactone vascular graft with epigallocatechin gallate embedded sandwiched layer-by-layer functionalization for enhanced antithrombogenicity and anti-inflammation

Small-diameter artificial vascular grafts modified with layer-by-layer (LBL) coating show promise in reducing the failure caused by thrombosis and inflammation, but undesirable stability and bioactivity issues of the coating and payload usually limits their long-term efficacy. Herein, inspired by catechol/gallol surface chemistry, a sandwiched layer-by-layer coating constructed by polyethyleneimine (PEI) and heparin with the embedding of epigallocatechin gallate (EGCG)-dexamethasone combination was used to modify the electrospun polycaprolactone (PCL) vascular grafts. Polyphenol embedding endowed the coating with abundant intermolecular interactions between each coating components, mainly contributed by the π-π stacking, weak intermolecular cross-linking and enriched hydrogen bonding, which further enhanced the coating stability and also supported the sustained release of the payloads, like polyelectrolytes and drugs. Compared with the conventional LBL coating, the loading amounts of heparin and dexamethasone in the EGCG embedded LBL coatings doubled and the drug release could be significantly prolonged without serious initial burst. The in vitro and ex vivo assays indicated that the modified PCL vascular grafts would address impressive prolonged anti-platelet adhesion/activation and anti-fibrinogen denaturation ability. Meanwhile, the dexamethasone loading entrusted the sandwiched LBL coating with mild tissue response, in terms of inhibiting the macrophage activation. These results strongly demonstrated that the sandwiched LBL coating with EGCG embedding was an effective method to improve the patency rates of PCL small artificial vascular grafts, which could also be extended to other blood-contacting materials.

In Vivo Tissue-Engineered Allogenic “Biotube” Vascular Grafts Could Grow in a Growing Canine Model

Introduction - In pediatric surgery, size mismatch inducing between artificial vascular grafts and growing recipients vessels remains a serious problem to be solved. Biotubes are connective tissue tubes, formed by in body tissue architecture technology (IBTA), which is a novel and practical approach of regenerative medicine. Recently, we developed type C Biotubes with thick wall thickness. This study aimed to evaluate the growth potential of type C Biotubes by examining their caliber and length adaptation to growing native arteries after implantation.

A Long “Biotube” Vascular Graft for Hemodialysis Access: Evaluation in an Animal Model

Introduction - In patients receiving hemodialysis, autologous arteriovenous fistula (AVF) is first choice for vascular access. On the other hand, artificial vascular grafts are needed in an underlying disease or second surgery. However, they had any risk such as infectivity or low patency. In-body tissue architecture (iBTA) can prepare collagenous tubes, called Biotubes, by using a patient's body as a bioreactor. Previously, autologous Biotubes grown in patient’s subcutaneous pouches were successfully bypassed the venous stenosis region as the first-in-human study. In this study, long Biotubes were implanted as canine or goat AV hemodialysis access. Methods - Disk-like molds (1 in photos) having spiral cylinder were embedded in beagles or goats subcutaneously for 2 months. Biotubes with diameter of 4 or 5 mm and wall thickness of 1.5 mm were obtained after removing the mold harvested (2 in photos). The Biotubes were stored in an alcoholic solution at room temperature. Immediately before implantation Biotubes were immersed in a 0.6% glutaraldehyde solution for 2 min. AV shunts were prepared with allogenic Biotubes (straight shape, length 10 cm for beagles, U-shape, 50 cm for goats) between the carotid artery and jugular vein. Follow up was performed with Doppler echo and angiography. Results - Following placement of all Biotubes, continuous thrill was felt by palpation and Doppler echo showed turbulent blood flow. Angiography revealed that all three straight beagle Biotubes were patent for 6 months without any abnormal deformation in vascular shape (3 in photos). Percutaneous punctures and compression hemostasis within several minutes at every other day were possible after 1 month of implantation. All two U-shaped goat Biotubes were also patent up to 3 months until now even with the length of 50 cm (4 in photos). Conclusion - Long Biotubes successfully created an AV shunt that maintained steady blood flow, suggesting that Biotubes can have high potential clinical use as vascular access for hemodialysis.

Effects of Diamond-like-carbon Coating for ePTFE Artificial Vascular Graft as Arteriovenous Graft

Effects of Diamond-like-carbon Coating for ePTFE Artificial Vascular Graft as Arteriovenous Graft

Orally Administered Aspirin Reduces the Endothelial Cell Damage Caused by Ischemia-reperfusion Injury of Arterial Vascular Grafts in A Rodent Model of Arterial Revascularisation

Orally Administered Aspirin Reduces the Endothelial Cell Damage Caused by Ischemia-reperfusion Injury of Arterial Vascular Grafts in A Rodent Model of Arterial Revascularisation

Enhanced endothelial cell activity induced by incorporation of nano-thick tantalum layer in artificial vascular grafts

Expanded polytetrafluoroethylene (ePTFE) has been successfully used as an artificial vascular graft material owing to its unique merits of fibrous structure, chemical stability, physical robustness, and nontoxicity. However, its insufficient endothelial cell affinity arising from its highly hydrophobic surface nature induces early thrombus formation and development of neointimal hyperplasia, leading to poor long-term patency rates. In this study, we demonstrate a novel rapid surface modification technique, termed as sputtering-based plasma immersion ion implantation (S-PIII), to elicit favorable vascular responses on the ePTFE surface. This technique enables rapid ion implantation of biologically compatible tantalum (Ta) into ePTFE surfaces, generating a nano-thick Ta-rich surface layer (<30 at.%) without any structural defects or loss of ePTFE’s fibrous morphology. Surface properties of ePTFE, such as its biologically inert chemical structure and strong hydrophobicity, are ameliorated considerably after the S-PIII treatment, which is more favorable for endothelial cell (EC) adherence, spreading, and proliferation. In particular, compared to a bare ePTFE surface, Ta-implanted ePTFE possesses an antithrombogenic property, suppressing platelet adhesion and activation on its surface. From an in vivo pilot study with a canine aortic bypass model, Ta-implanted ePTFE demonstrates substantially suppressed early thrombosis with rapid formation of EC monolayers covering the luminal surface.

The effect of Substance P/Heparin conjugated PLCL polymer coating of bioinert ePTFE vascular grafts on the recruitment of both ECs and SMCs for accelerated regeneration

Artificial vascular grafts consisting of ePTFE have been mainly used in clinics for the treatment of cardiovascular disease. However, artificial grafts can become clogged after a long time due to thrombosis, as graft maturation by endothelialization is limited. The strategy introduced in this study is to induce graft remodeling through interaction between the bioinert graft and the body. The Substance P (SP) and heparin were covalently conjugated with PLCL, an elastic biocompatible copolymer and the Substance P-conjugated PLCL (SP-PLCL) and/or heparin-conjugated PLCL (Hep-PLCL) were vacuum-coated onto ePTFE vascular grafts. To assess the effectiveness of the coating, coated samples were evaluated by implanting them subcutaneously into SD-Rats. Coatings allow grafts to be remodeled by creating a microenvironment where cells can grow by infiltrating into the grafts while also greatly enhancing angiogenesis. In particular, a double coating of Hep-PLCL and SP-PLCL (Hep/SP-PLCL) at four weeks showed markedly improved vascular remodeling through the recruitment of mesenchymal stem cells (MSCs), vascular cells (ECs, SMCs) and M2 macrophages. Based on these results, it is expected that when the Hep/SP-PLCL-coated ePTFE vascular grafts are implanted in situ, long-term patency will be assured due to the appropriate formation of an endothelial layer and smooth muscle cells in the grafts like native vessels.

Development of Small-diameter Polyester Vascular Grafts Coated with Silk Fibroin Sponge

ABSTRACTIn recent years, the demand for functional small-diameter (< 6 mm) artificial vascular grafts has greatly increased due to an increase in the number of patients with vascular heart disease. However, currently, there are no available commercial small-diameter grafts. The objective of this research was to develop a porous silk fibroin (SF)-coated poly(ethylene terephthalate) (PET) graft with a diameter < 6 mm. The graft was compared with a gelatin-coated PET graft because the latter PET graft with a diameter ~ 6 mm was widely used as a commercial vascular graft. Initially, porous SF was prepared using Glyc as the porogen [termed SF(Glyc)] and the PET grafts were prepared through the double-Raschel knitting method. Subsequently, the degradation of the SF coating was monitored using protease XIV in vitro and was compared with that observed in gelatin-coated PET grafts. Finally, these grafts were also implanted into rats for an in vivo comparison. In degradation experiments, after 7 days, the SF was clearly digested by protease XIV, but the gelatin on the graft was still remained at the outer surface. In implantation experiments in rats, the SF(Glyc)-coated PET graft was rapidly degraded in vivo and remodeling to self-tissues was promoted compared with the gelatin-coated PET graft. Thrombus formation and intimal hyperplasia were observed in the gelatin-coated PET graft; however, such side reactions were not observed in the SF(Glyc)-coated PET graft. Thus, the porous SF(Glyc)-coated PET graft with a small diameter < 6 mm may be useful as a commercial vascular graft.

Bioactive and mechanically stable hydroxyapatite patterning for rapid endothelialization of artificial vascular graft

Polymeric vascular grafts have been widely used in the vascular regeneration field because of their ease of application. However, synthetic polymer grafts have the severe problem of low biocompatibility, which may cause delayed endothelialization and hyperplasia. In this study, we fabricated a linear hydroxyapatite (HA) pattern on a silicon wafer and then transferred the pattern to a poly(L-lactic)-acid (PLLA) film for use as a tubular vascular graft. The HA pattern with its characteristic needle-like shape was successfully embedded into the PLLA. The HA-patterned PLLA film exhibited superior mechanical stability compared with that of a HA-coated PLLA film under bending, elongation, and in vitro circulation conditions, suggesting its suitability for use as a tubular vascular graft. In addition, the HA pattern guided rapid endothelialization by promoting proliferation of endothelial cells and their migration along the pattern. The hemocompatibility of the HA-patterned PLLA was also confirmed, with substantially fewer platelets adhered on its surface. Overall, in addition to good mechanical stability, the HA-patterned PLLA exhibited enhanced biocompatibility and hemocompatibility compared with pure PLLA.

Analysis of Risk Factors Affecting the Development of Infection in Artificial Vascular Grafts Used for Reconstruction of Middle Hepatic Vein Tributaries in Living Donor Liver Transplantation.

To analyze the risk factors affecting the development of infection in artificial vascular grafts (AVGs) used for reconstruction of middle hepatic vein (MHV) tributaries in living donor liver transplantation (LDLT). Between January 2009 and January 2018, 1253 right lobe LDLTs were performed at our Transplant Institute, and MHV tributaries of the 640 right lobe liver grafts were reconstructed with AVG. Reconstructed MHV tributaries were removed due to AVG infection in 25 of these patients (case group; n = 25). To determine risk factors for AVG infection, right lobe LDLT patients without AVG infections were selected as control group (n = 615). Both groups were compared about demographic parameter, transcystic catheter usage, bile leakage, type of biliary anastomosis (duct-to-duct, telescopic duct-to-duct), number of graft biliary duct (=1 versus >1), number of biliary anastomosis (=1 versus >1), AVG thrombosis, AVG types (Dacron versus polytetrafluoroethylene). Univariate analyses were used for comparison of different variables, and variables with P ≤ 0.20 were taken into logistic regression model. Univariate analysis shows that statistically significant differences were found between groups regarding bile leakage (P < 0.001), graft thrombosis (P = 0.002), transcystic catheter (P = 0.049), and AVG types (P = 0.013). Variables with P ≤ 0.20 were taken into logistic regression model. Multivariate analysis shows that bile leakage (odds ratio, 13.3) and AVG thrombosis (odds ratio, 9.8) were determined as independent and strong risk factors for development of AVG infection. This study revealed that bile leakage and graft thrombosis are independent and strong risk factors for infections of AVGs used for anterior sector drainage reconstruction.

The cell source in tissue regeneration of vascular grafts

The development of small-diameter artificial vascular grafts has become a research hotspot in recent years. To achieve long-term patency, an ideal vascular graft should have the capacity to recruit host cells to participate in vascular tissue regeneration. Based on previous research, we provide detailed descriptions of the cell sources and cell types involved in vascular graft regeneration. Methodology to determine host cell infiltration and the limitations of current techniques are also discussed.

3D Printing of Amino Resin-based Photosensitive Materials on Multi-parameter Optimization Design for Vascular Engineering Applications.

Cardiovascular diseases are currently the most common cause of death globally and of which, the golden treatment method for severe cardiovascular diseases or coronary artery diseases are implantations of synthetic vascular grafts. However, such grafts often come with rejections and hypersensitivity reactions. With the emergence of regenerative medicine, researchers are now trying to explore alternative ways to produce grafts that are less likely to induce immunological reactions in patients. The main goal of such studies is to produce biocompatible artificial vascular grafts with the capability of allowing cellular adhesion and cellular proliferation for tissues regeneration. The Design of Experimental concepts is employed into the manufacturing process of digital light processing (DLP) 3D printing technology to explore near-optimal processing parameters to produce artificial vascular grafts with vascular characteristics that are close to native vessels by assessing for the cause and effect relationships between different ratios of amino resin (AR), 2-hydroxyethyl methacrylate (HEMA), dopamine, and curing durations. We found that with proper optimization of fabrication procedures and ratios of materials, we are able to successfully fabricate vascular grafts with good printing resolutions. These had similar physical properties to native vessels and were able to support cellular adhesion and proliferation. This study could support future studies in exploring near-optimal processes for fabrication of artificial vascular grafts that could be adapted into clinical applications.

Co-immobilization of ACH11 antithrombotic peptide and CAG cell-adhesive peptide onto vascular grafts for improved hemocompatibility and endothelialization

Surface modification by conjugating biomolecules has been widely proved to enhance biocompatibility of small-caliber artificial vascular grafts. In this study, we aimed at developing a multifunctional vascular graft that provides not only good hemocompatibility but also in situ rapid endothelialization. Herein, a vascular graft (inner diameter ∼2 mm) was fabricated by electrospinning with poly(lactic acid-co-caprolactone) and gelatin, and then biofunctionalized with antithrombotic peptide with sequence LTFPRIVFVLG (ACH11) and cell adhesion peptide with sequence CAG through adhesive poly(dopamine) coating. We developed this graft with the synergistic properties of low thrombogenicity and rapid endothelialization. The successful grafting of both CAG and ACH11 peptides was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface micromorphology of the modified surfaces was observed by field emission scanning electron microscopy. Our results demonstrated that the multifunctional surface suppressed the denaturation of absorbed fibrinogen, hindered coagulation factor Xa activation, and inhibited platelet adhesion and aggregation. Importantly, this modified surface could selectively enhance endothelial cells adhesion, proliferation and release of nitric oxide. Upon in vivo implantation of 6 weeks, the multifunctional vascular graft showed improved patency and superior vascular endothelialization. Overall, the results effectively demonstrated that the co-immobilization of ACH11 and CAG provided a promising method for the improvement of hemocompatibility and endothelialization of vascular grafts. Statement of SignificanceElectrospun small-caliber vascular grafts are increasingly used to treat cardiovascular diseases. Despite their success related to their good biodegradation and mechanical strength, they have some drawbacks, such as low hemocompatibility and endothelialization. The single-function ligands are insufficient to modify surface with both good hemocompatibility and rapid endothelialization simultaneously. Therefore, we functionalized electrospun vascular graft by novel antithrombotic peptide and cell-adhesive peptide to construct superior anticoagulation and ECs-selective adhesion surface in present study. The multifunctional vascular grafts benefit for high long-term patency and rapid endothelialization.

High-strength ceramics as innovative candidates for cardiovascular implants.

Cytocompatibility and hemocompatibility are essential features for tissue- and blood-contacting implants such as artificial heart valves, vascular grafts and stents. Platelet activation as the main trigger of thrombosis results in implant failures. The purpose of this study results from the demands on anti-coagulant and non-corrosive innovative biomaterials for cardiovascular implants. Therefore, hemocompatibility and cytocompatibility of various high-strength ceramics, such as alumina, zirconia, silicon nitride and silicon carbide, were examined to identify the most appropriate ceramic for cardiovascular implants. In addition to the material species, different crystallographic structures (single- and poly-crystalline) and surface terminations (Si and C faces) of silicon carbide were used in order to reveal the interactions between blood and material surface. Three cell types, i.e. human umbilical vein endothelial cells, mesenchymal stem cells and blood cells, were cultured on the substrates and their interactions with material surfaces were analyzed. Cytotoxicity of the materials was tested by live/dead staining. Hemocompatibility in terms of platelet and white blood cell activation was examined via scanning electron microscopy and indirect ELISA. To mimic physiological conditions in vitro, the hemocompatibility of the materials was additionally analyzed in a bioreactor under dynamic flow conditions in comparison to static incubation. All ceramics were found to be cytocompatible for mesenchymal stem cells, human umbilical vein endothelial cells and blood cells. The highest number of resting, non-activated platelets was observed on the monocrystalline silicon carbide demonstrating that this material triggers the platelet activation less compared to the other materials. It is found to be the most appropriate ceramic for blood-contacting implants in terms of cell adhesion, cell viability, and hemocompatibility.

Development of an immunodeficient pig model allowing long-term accommodation of artificial human vascular tubes

Before they are used in the clinical setting, the effectiveness of artificially produced human-derived tissue-engineered medical products should be verified in an immunodeficient animal model, such as severe combined immunodeficient mice. However, small animal models are not sufficient to evaluate large-sized products for human use. Thus, an immunodeficient large animal model is necessary in order to properly evaluate the clinical efficacy of human-derived tissue-engineered products, such as artificial grafts. Here we report the development of an immunodeficient pig model, the operational immunodeficient pig (OIDP), by surgically removing the thymus and spleen, and creating a controlled immunosuppressive protocol using a combination of drugs commonly used in the clinical setting. We find that this model allows the long-term accommodation of artificial human vascular grafts. The development of the OIDP is an essential step towards a comprehensive and clinically relevant evaluation of human cell regeneration strategies at the preclinical stage.

Engineering small-caliber vascular grafts from collagen filaments and nanofibers with comparable mechanical properties to native vessels

At the present time, there is no successful synthetic, off-the-shelf small-caliber vascular graft (<6 mm) for the repair or bypass of the coronary or carotid arteries. This stimulates on-going investigations to fabricate an artificial vascular graft that has both sufficient mechanical properties as well as superior biological performance. Collagen has long been considered as a viable material to encourage cell recruitment, tissue regeneration, and revascularization, but its use has been limited by its inferior mechanical properties. In this study, novel electrochemically aligned collagen filaments were used to engineer a bilayer small-caliber vascular graft, by circular knitting the collagen filaments and electrospinning collagen nanofibers. The collagen prototype grafts showed significantly greater bursting strength under dry and hydrated conditions to that of autografts such as the human internal mammary artery and the saphenous vein (SV). The suture retention strength was sufficient under dry condition, but that under hydrated condition needs to be further improved. The radial dynamic compliance of the collagen grafts was similar to that of the human SV. During in vitro cell culture assays with human umbilical vein endothelial cells, the prototype collagen grafts also encouraged cell adhesion and promoted cell proliferation compared to the synthetic poly(lactic acid) grafts. In conclusion, this study demonstrated the feasibility of the use of novel collagen filaments for fabricating small caliber tissue-engineered vascular grafts that provide both sufficient mechanical properties and superior biological performance.

Nano- and Micropatterned Polycaprolactone Cellulose Composite Surfaces with Tunable Protein Adsorption, Fibrin Clot Formation, and Endothelial Cellular Response.

This work describes the interaction of the human blood plasma proteins albumin, fibrinogen, and γ-globulins with micro- and nanopatterned polymer interfaces. Protein adsorption studies were correlated with the fibrin clotting time of human blood plasma and with the growth of primary human pulmonary artery endothelial cells (hECs) on these patterns. It was observed that blends of polycaprolactone (PCL) and trimethylsilyl-protected cellulose form various thin-film patterns during spin coating, depending on the mass ratio of the polymers in the spinning solutions. Vapor-phase acid-catalyzed deprotection preserves these patterns but yields interfaces that are composed of hydrophilic cellulose domains enclosed by hydrophobic PCL. The blood plasma proteins are repelled by the cellulose domains, allowing for a suggested selective protein deposition on the PCL domains. An inverse proportional correlation is observed between the amount of cellulose present in the films and the mass of irreversibly adsorbed proteins. This results in significantly increased fibrin clotting times and lower masses of deposited clots on cellulose-containing films as revealed by quartz crystal microbalance with dissipation measurements. Cell viability of hECs grown on these surfaces was directly correlated with higher protein adsorption and faster clot formation. The results show that presented patterned polymer composite surfaces allow for a controllable blood plasma protein coagulation and a significant biological response from hECs. It is proposed that this knowledge can be utilized in regenerative medicine, cell cultures, and artificial vascular grafts by a careful choice of polymers and patterns.

Reconstruction of Middle Hepatic Vein Tributaries With Artificial Vascular Grafts in Living Donor Liver Transplant Using Right Lobe Grafts: A Case Series

BackgroundCongestion of the anterior section of the grafted liver might be a problem when performing living donor liver transplant using a right lobe graft without middle hepatic vein (MHV). This can be prevented by MHV tributary reconstruction. We report our procedure and results of reconstructing MHV tributaries using artificial vascular grafts (AVGs). MethodsWe consider venous reconstruction when the estimated territory of each MHV tributary of the transplanted liver is more than 100 mL. For tributaries distant from the stump of the right hepatic vein of the graft, we use heparin-bonded AVGs made of expanded polytetrafluoroethylene with circular rings as the interposition graft between the MHV tributary and the inferior vena cava. During donor surgery, the suturing margin of the MHV tributary is secured before cutting, and it is anastomosed to the AVG during back-bench surgery. After restoration of portal flow in the recipient, we anastomose the AVG at a new position on the inferior vena cava. ResultsThe above procedure was performed for 4 cases. The estimated drainage territory of the vein that was reconstructed using the AVG ranged from 104 to 180 mL. The AVG patency was achieved for about 2 months in all cases. In terms of morbidity, biloma and pancreatic fistula were observed in 2 cases, although removal of the AVG was not required postoperatively in any of the cases. ConclusionThe heparin-bonded expanded polytetrafluoroethylene AVG with circular rings is a feasible option for MHV tributary reconstruction in living donor liver transplant using right liver lobe grafts without MHVs.

Evaluation of a hybrid small caliber vascular graft in a rabbit model

ObjectiveA hybrid small-caliber artificial vascular graft based on bilayer porcine small intestinal submucosa (SIS) with curdlan and dipyridamole mixture film serving as the so-called sandwich filler was developed for biological performance evaluation. We evaluated the performance of the graft and filler. MethodsSIS was coated with heparin by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. Curdlan acted as the carrier of dipyridamole. Three types of graft tubes (2 mm internal diameter and 20 mm in length) were manufactured: bilayer SIS with 10% curdlan + 10% dipyridamole mixture film (SCD), bilayer SIS with 10% curdlan film (SC), and monolayer SIS (S). The remodeling characteristics of the grafts were evaluated by implanting them as bypass in rabbit carotid arteries for 2 and 3 months. Each group contained 16 rabbits, and 16 nonsurgical rabbits served as the control group. ResultsEight rabbits of each group, including the graft occluded group, were killed at 2 months and the others were killed at 3 months. Follow-up showed that all 8 grafts in SCD group were patent at 2 months. Six of 16 grafts in the SC group and 5 of 16 grafts in the S group were occluded at 2 months. One of 8 SCD grafts were occluded at 3 months and the patent showed a confluent endothelium without intimal hyperplasia. The neointima layer was composed of circumferentially aligned vascular smooth muscle cells. At 3 months, SC and S group grafts showed incomplete endothelialization and varying degrees of mural thrombus, accompanied by occlusion in the SC group (3 of 8) and S group (2 of 8). ConclusionsThe novel hybrid small caliber artificial vascular graft exhibited an improvement in revascularization resulting in high patency rate.

Advanced Silk Fibroin Biomaterials and Application to Small-Diameter Silk Vascular Grafts.

As the incidences of cardiovascular diseases have been on the rise in recent years, the need for small-diameter artificial vascular grafts is increasing globally. Although synthetic polymers such as expanded polytetrafluoroethylene or poly(ethylene terephthalate) have been successfully used for artificial vascular grafts ≥6 mm in diameter, they fail at smaller diameters (<6 mm) due to thrombus formation and intimal hyperplasia. Thus, development of vascular grafts for small diameter vessel replacement that are <6 mm in diameter remains a major clinical challenge. Silk fibroin (SF) from Bombyx mori silkworm is well-known as an excellent textile and also has been used as suture material in surgery for more than 2000 years. Many attempts to develop small-diameter SF vascular grafts with <6 mm in diameter have been reported. Here, research and development in small-diameter vascular grafts with SF are reviewed as follows: (1) the heterogeneous structure of SF fiber (Silk II), including the packing arrangements and type II β-turn structure of SF (Silk I*) before spinning; (2) SF modified by transgenic silkworm, which is more suitable for vascular grafts; (3) preparation of small-diameter SF vascular grafts; (4) characterization of SF in the hydrated state, including dynamics of water molecules by nuclear magnetic resonance; and (5) evaluation of the SF grafts by in vivo implantation experiment. According to the findings, SF is a promising material for small-diameter vascular graft development.