Polytetrafluoroethylene Vascular Grafts Research Articles

Anti-thrombotic poly(AAm-co-NaAMPS)-xanthan hydrogel-expanded polytetrafluoroethylene (ePTFE) vascular grafts with enhanced endothelialization and hemocompatibility properties

Cardiovascular diseases (CVDs) are the leading cause of death among all non-communicable diseases globally. Although expanded polytetrafluoroethylene (ePTFE) has been widely used for larger-diameter vascular graft transplantation, the persistent thrombus formation and intimal hyperplasia of small-diameter vascular grafts (SDVGs) made of ePTFE to treat severe CVDs remain the biggest challenges due to lack of biocompatibility and endothelium. In this study, bi-layered poly(acrylamide-co-2-Acrylamido-2-methyl-1-propanesulfonic acid sodium)-xanthan hydrogel-ePTFE (poly(AAm-co-NaAMPS)-xanthan hydrogel-ePTFE) vascular grafts capable of promoting endothelialization and prohibiting thrombosis were synthesized and fabricated. While the external ePTFE layer of the vascular grafts provided the mechanical stability, the inner hydrogel layer offered much-needed cytocompatibility, hemocompatibility, and endothelialization functions. The interface morphology between the inner hydrogel layer and the outer ePTFE layer was observed by scanning electron microscope (SEM), which revealed that the hydrogel was well attached to the porous ePTFE through mechanical interlocking. Among all the hydrogel compositions tested with cell culture using human umbilical vein endothelial cells (HUVECs), the hydrogel with the molar ratio of 40:60 (NaAMPS/AAm) composition (i.e., Hydrogel 40:60) exhibited the best endothelialization function, as it produced the largest endothelialization area that was three times more than of that of plain ePTFE on day 14, maintained the highest average cell viability, and had the best cell morphology. Hydrogel 40:60 also showed excellent hemocompatibility, prolonged activated partial thromboplastin time (aPTT), and good mechanical properties. Overall, bi-layered poly(AAm-co-NaAMPS)-xanthan hydrogel-ePTFE vascular grafts with the Hydrogel 40:60 composition could potentially solve the critical challenge of thrombus formation in vascular graft transplantation applications.

Small diameter expanded polytetrafluoroethylene vascular graft with differentiated inner and outer biomacromolecules for collaborative endothelialization, anti-thrombogenicity and anti-inflammation

Without differentiated inner and outer biological function, expanded polytetrafluoroethylene (ePTFE) small-diameter (<6 mm) artificial blood vessels would fail in vivo due to foreign body rejection, thrombosis, and hyperplasia. In order to synergistically promote endothelialization, anti-thrombogenicity, and anti-inflammatory function, we modified the inner and outer surface of ePTFE, respectively, by grafting functional biomolecules, such as heparin and epigallocatechin gallate (EGCG), into the inner surface and polyethyleneimine and rapamycin into the outer surface via layer-by-layer self-assembly. Fourier-transform infrared spectroscopy showed the successful incorporation of EGCG, heparin, and rapamycin. The collaborative release profile of heparin and rapamycin lasted for 42 days, respectively. The inner surface promoted human umbilical vein endothelial cells (HUVECs) adhesion and growth and that the outer surface inhibited smooth muscle cells growth and proliferation. The modified ePTFE effectively regulated the differentiation behavior of RAW264.7, inhibited the expression of proinflammatory mediator TNF-α, and up-regulated the expression of anti-inflammatory genes Arg1 and Tgfb-1. The ex vivo circulation results indicated that the occlusions and total thrombus weight of modified ePTFE was much lower than that of the thrombus formed on the ePTFE, presenting good anti-thrombogenic properties. Hence, the straightforward yet efficient synergistic surface functionalization approach presented a potential resolution for the prospective clinical application of small-diameter ePTFE blood vessel grafts.

Clinical Outcomes After Tracheobronchoplasty With Ringed Polytetrafluoroethylene Vascular Graft

BackgroundThis report describes the surgical technique and outcomes of tracheobronchoplasty (TBP) with ringed polytetrafluoroethylene (PTFE) vascular graft. MethodsWe identified all patients who underwent PTFE-TBP for severe expiratory central airway collapse from January 1, 2018 to August 2021 at Mayo Clinic, Florida. Preoperative and postoperative St George’s Respiratory Questionnaire (SGRQ), Cough-Specific Quality of Life Questionnaire (CSQLQ), pulmonary function testing, 6-minute walk test, and blinded dynamic bronchoscopy videos at 3-month follow-up were used to assess outcomes. ResultsFourteen patients (median age, 62.5 years; 64.3% female) underwent PTFE-TBP. The median operative time was 355 minutes, median hospital length of stay was 5 days, and median intensive care unit stay was 1 day. One patient had a Clavien-Dindo grade ≥3 complication. Comparison of preoperative and postoperative questionnaire scores demonstrated improvement in median SGRQ score by 14.79 (P = .013) and CSQLQ score by 22 (P = .005). Preoperative and postoperative pulmonary function and 6-minute walk test results showed no significant difference. Postoperative bronchoscopy demonstrated improvement in median collapsibility of mid trachea by 39.6% (P < .001), distal trachea by 50% (P < .001), left main bronchus by 38.2% (P < .001), right main bronchus by 37.9% (P < .001), and bronchus intermedius by 30.7% (P < .001). ConclusionsPTFE-TBP provides significant improvement in patients' symptoms and expiratory central airway collapse as judged by preoperative and postoperative quality of life questionnaires and bronchoscopy.

Dynamic digital radiography: a novel quantitative modality to assess the pulmonary blood flow.

A 17-year-old girl with congenital unilateral absence of the pulmonary artery underwent surgical reconstruction of the right pulmonary artery (RPA) with a 6 mm polytetrafluoroethylene vascular graft 15 years ago. She had received stent implantation (S.M.A.R.T® 7.0 × 60 mm) to control the graft stenosis at 10-years-old. Nevertheless, regular hemodynamic assessment with balloon angioplasty was required because of the recurrence of graft stenosis. The current cardiac catheterization demonstrated RPA graft stenosis with a pressure gradient of 34 mmHg (Panel A). Tecnethium-99m-macroaggregated albumin lung perfusion scintigraphy showed decreased perfusion in the right lung (right/left: 20.1%/79.9%) (Panel B). A similar result was achieved in dynamic digital radiography (DDR) captured by a flat panel detector (Aero DR fine®, KONICAMINOLTA, Japan) and a conventional X-ray system (RAD speed Pro®, SHIMADZU, Japan), using a prototype workstation (KONICAMINOLTA, Japan) (right/left: 17.4%/82.6%). (Panel C, and Supplementary data online, Video) Lung perfusion scintigraphy has been a golden standard modality for the quantitative assessment of pulmonary blood flow laterality and is inevitably accompanied by radiation exposure. DDR is a new imaging to visualize small changes in pixel value representing the pulmonary circulation without contrast media.1,2 This imaging system can facilitate both qualitative and quantitative evaluations of the dynamic pulmonary circulation with a low cost, short examination time, and reduced radiation exposure. This convenient and non-invasive method will be an effective and alternative approach to assessing lung perfusion in patients with pulmonary artery stenosis.

Bad aortoiliac vessels: Not a contraindication for renal transplantation

Studies on aortoiliac reconstruction for diseased vessels and renal transplantation are limited. We report a rare experience in reconstruction of aortobifemoral bypass using polytetrafluoroethylene (PTFE) vascular graft, along with a side limb graft for the donor artery in living kidney transplantation. A 44-year-old male, with autosomal dominant polycystic kidney disease on dialysis, needing transplantation, was found to have diseased aortoiliac vessels with tight stenosis at the aortic bifurcation during workup for renal transplantation. The anastomosis of the donor renal artery to the native iliac vessel was a surgical challenge with risk of hypoperfusion to renal graft as well as subsequent lower-limb ischemia. Hence, we went ahead with aortobifemoral bypass using PTFE vascular graft and anastomosis of the donor renal artery to a side limb graft from the main graft. Posttransplantation, he had stable normal renal allograft function at 1-year follow-up.

Clampless 2 Device: Experimental Study of a Lateral Aorto-Prosthetic Anastomosic Device Without Clamping or Suturing

To offer an alternative to conventional techniques of lateral prosthetic anastomosis on arteries which require a long training, and impose an extensive open surgery, we are proposing the clampless 2 device (C2D) implanted by a simple arterial puncture and allows a lateral implantation of a polytetrafluoroethylene (PTFE) vascular graft in an artery, without arterial clamping or suture. C2D is a "T" shaped 25-mm long and 8-mm diameter Nitinol stent with a 6-mm PTFE graft prosthesis mounted laterally on the stent, and implanted in an artery, via a 21-French sheath, and a compliant balloon inflation. Invitro testing of the C2D was first performed on a bench including a segment of a 7-mm internal diameter pig abdominal aorta. A series of 5 consecutive C2D implantation was analyzed with evaluation of the implantation time and the fluid losses at a fluid pressure of 80 and 150mm Hg. The C2D implantation was finally controlled by angioscopy. An aorto-iliac bypass was then secondly performed on 8 living sows, with a side-to-end C2D implantation in the infrarenal abdominal aorta, followed by a conventional end-to-end prosthetic left iliac trunk anastomosis. The C2D and distal conventional anastomotic times were evaluated, as well as the total operative time and blood loss. A postoperative angiogram was systematically performed. The C2D was successfully implanted in all 5 invitro tests, with an average implantation time of 2'58 (range: 2'25-3'22). The mean value of fluid losses was 84ml (range: 67-94ml), with no fluid leakage occurring at 80- and 150-mm Hg pressure. All anastomoses were patent after macroscopic study by angioscopy with a perfect application of the stent in the aortic wall. In 8 living sows (mean weight: 42kg, 37-50kg), an aorto-left iliac bypass was successfully implanted in all cases, with a total mean procedure time of 101min (range: 90-130min), and an average fluid loss of 77ml (range:20-120ml). The mean implantation time was 4'39 (range 3'29-5'52) for C2D and 16min (range 12-17min) to perform the conventional distal prosthetic-iliac anastomosis. Systematic arteriographic and angioscopy control showed perfect patency of the C2D implantations. Preliminary invitro and acute invivo testing of C2D implantation show good early results, allowing further long-lasting pig experiments on the way to human homologation.

The use of antimicrobial biomaterials as a savior from post-operative vascular graft-related infections: A review

Cardiovascular diseases rank first in mortality and morbidity. There are various treatments for replacing a blood vessel artificially, such as autologous graft implantation, bio-engineered vascular graft implantation, etc. Due to the external medical intervention or immunocompromised state in the patients, there are high chances of septic infection at the site of implantation. This increases the risk of blood-related infections in these patients. Thus, it is imperative to avoid the spread of infection and to destroy the infection-causing microorganisms by incorporating an antimicrobial agent in the implantable biomaterial. For instance, use combination of minocycline, chlorhexidine, and rifampin was impregnated on Dacron, and PTFE (polytetrafluoroethylene) vascular grafts showed a 100% patency rate and increased antibiotic activity than the counterparts. This review summarises various methods of incorporating antimicrobial agents in the biomaterial for developing an antimicrobial vascular graft.

A Vascular Graft On‐a‐Chip Platform for Assessing the Thrombogenicity of Vascular Prosthesis and Coatings with Tuneable Flow and Surface Conditions

AbstractVascular grafts are essential for the management of cardiovascular disease. However, the lifesaving potential of these devices is undermined by thrombosis arising from material and flow interactions on the blood contacting surface. To combat this issue, antithrombogenic coatings have emerged as a promising strategy for modulating blood and graft interaction in vivo. Although an important determinant of graft performance, hemodynamics are frequently overlooked for in vitro testing of coatings and their translatability remains poorly understood. Herein, this limitation is addressed with a microscale graft on‐a‐chip platform incorporating vascular prosthesis and coatings with tuneable flow and surface conditions in vitro. As a proof of concept, the platform is used to test the thrombogenicity of a novel class of lubricant‐infused surface (LIS) and antibody lubricant‐infused (anti‐CD34 LIS) coated expanded polytetrafluoroethylene (ePTFE) vascular grafts in the presence of arterial wall shear stress with and without endothelial cells. The findings suggest LIS ePTFE is thromboresistant under flow with significantly reduced fibrin(ogen) deposition, thrombin activity, and blood cell adhesion compared to uncoated controls. It is moreover apparent that the microscale properties of the device are advantageous for the testing and translation of novel antithrombogenic coatings and blood‐contacting materials in general.

What's in a wrap?

What's in a wrap?

Physical shish-kebab modification vs. chemical surface coating on expanded polytetrafluoroethylene vascular grafts for enhanced endothelial cell adhesion

Promoting rapid adhesion of endothelial cells is of significance for the viability of vascular grafts for small-diameter blood vessels (SDBVs) made of expanded polytetrafluoroethylene (ePTFE). Many physical and chemical surface modification methods have been developed to overcome the inertness of ePTFE and to promote cell adhesion. In this study, a biomimetic poly(ε-caprolactone) (PCL) shish-kebab microstructure was formed on the fibrillated domains of ePTFE through induced crystallization. The surface morphology and chemistry, mechanical property, cytocompatibility, and endothelial cell adhesion of PCL shish-kebab modified ePTFE were investigated. The effectiveness of and synergy between this physical topology modification and the traditional chemical RGD dig-coating in terms of cell adhesion were also evaluated. The positive effect of the shish-kebab structure on cell adhesion was found to be more significant than that of RGD coating, and there is a strong synergy between ePTFE surface modification and RGD coating. The biomimetic shish-kebab structure could be a promising material platform for further grafting and/or surface functionalization of ePTFE for other tissue engineering applications.

Pre‐implantation evaluation of a small‐diameter, long vascular graft (Biotube®) for below‐knee bypass surgery in goats

There are no small-diameter, long artificial vascular grafts for below-knee bypass surgery in chronic limb-threatening ischemia. We have developed tissue-engineered vascular grafts called "Biotubes®" using a completely autologous approach called in-body tissue architecture (iBTA). This study aimed at pre-implantation evaluation of Biotube and its in vivo preparation device, Biotube Maker, for use in below-knee bypass surgery.Forty nine makers were subcutaneously embedded into 17 goats for predetermined periods (1, 2, or 3months). All makers produced Biotubes as designed without inflammation over all periods, with the exception of a few cases with minor defects (success rate: 94%). Small hole formation occurred in only a few cases. All Biotubes obtained had an inner diameter of 4 mm and a length of 51 to 52 cm with a wall thickness of 594 ± 97 μm. All Biotubes did not kink when completely bent under an internal pressure of 100 mmHg and did not leak without any deformation under a water pressure of 200 mmHg. Their burst strength was 2409 ± 473 mmHg, and suture retention strength was 1.75 ± 0.27 N, regardless of the embedding period, whereas tensile strength increased from 7.5± 1.3N at 1month to 9.7± 2.0N at 3months with the embedding period. The amount of water leakage from the needle holes prepared in the Biotube wall was approximately 1/7th of that in expanded polytetrafluoroethylene vascular grafts. The Biotubes could be easily connected to each other without cutting or anastomosis leaks. They could be stored for at least 1year at room temperature. This study confirmed that even Biotubes formed 1month after embedding of Biotube Makers had properties comparable to arteries.

Comparison of popliteal artery aneurysm outcomes after open repair and endovascular repair: reducing post-operative type II endoleak and sac enlargement.

BackgroundThis cohort study aimed to evaluate the short- and long-term outcomes of open repair (OR) and endovascular repair (ER) and identify the most suitable graft and approach for treating popliteal artery aneurysm (PAA) patients.MethodsThe data of PAA patients from January 2000 to August 2020 were retrospectively collected and analyzed. The primary endpoints were 30-day mortality, peri-operative complication morbidity, post-operative type II endoleak, and sac- enlargement. The secondary endpoints were primary graft patency, secondary graft patency, the reintervention rate, and overall mortality.ResultsA total of 213 PAAs of 186 patients were surgically repaired. The ER group had a significantly lower mean length of hospital stay, blood loss volume, and aneurysm diameter than the OR group. There were no significant differences between the ER and OR groups in terms of average surgery time, 30-day mortality, peri-operative complication morbidity, post-operative type II endoleak, sac enlargement, primary and secondary graft patency, reintervention rate, and overall mortality. However, in the sub-group analysis, autologous vein grafts had significantly higher primary and secondary graft patency rates than expanded polytetrafluoroethylene (ePTFE) vascular grafts and stent grafts. Type II endoleaks and post-operative sac enlargements were less likely to occur in OR patients when the posterior approach was adopted.ConclusionsWe failed to establish any difference in superiority between OR or ER. However, we found that autologous vein grafts have better graft patency and the posterior approach is less likely to lead to type II endoleaks and sac enlargements after the initial PAA surgical procedure. However, more high-quality, large-scale randomized controlled trials need to be conducted.

A Radiation-Crosslinked Gelatin Hydrogel That Promotes Tissue Incorporation of an Expanded Polytetrafluoroethylene Vascular Graft in Rats.

A prosthetic vascular graft that induces perigraft tissue incorporation may effectively prevent serious sequelae such as seroma formation and infection. Radiation-crosslinked gelatin hydrogel (RXgel) mimics the chemical and physical properties of the in vivo extracellular matrix and may facilitate wound healing by promoting tissue organization. Fibroblasts cultured on RXgel actively migrated into the gel for up to 7 days. RXgels of three different degrees of hardness (Rx[10], soft; Rx[15], middle; Rx[20], hard) were prepared, and small disc-like samples of RXgels were implanted into rats. In vitro and in vivo results indicated that Rx[10] was too soft to coat vascular grafts. Thus, expanded polytetrafluoroethylene (ePTFE) vascular grafts coated with RXgel were developed using Rx[15] and Rx[20] gels, and ring-shaped slices of the graft were implanted into rats. Alpha-smooth muscle actin (αSMA) and type III collagen (Col-III) levels were detected by immunohistochemistry. Immunohistochemical staining for αSMA and Col-III demonstrated that RXgel-coated vascular grafts induced more granulation tissue than non-coated grafts on days 14 and 28 after implantation. RXgel-coated ePTFE vascular grafts may provide a solution for patients by reducing poor perigraft tissue incorporation.

A rechargeable anti-thrombotic coating for blood-contacting devices

Despite the potential of anti-thrombogenic coatings, including heparinized surfaces, to improve the performance of blood-contacting devices, the inevitable deterioration of bioactivity remains an important factor in device failure and related thrombotic complications. As a consequence, the ability to restore the bioactivity of a surface coating after implantation of a blood-contacting device provides a potentially important strategy to enhance its clinical performance. Here, we report the regeneration of a multicomponent anti-thrombogenic coating through use of an evolved sortase A to mediate reversible transpeptidation. Both recombinant thrombomodulin and a chemoenzymatically synthesized ultra-low molecular weight heparin were repeatedly and selectively immobilized or removed in a sequential, alternating, or simultaneous manner. The generation of activated protein C (aPC) and inhibition of activated factor X (FXa) was consistent with the molecular composition of the surface. The fabrication of a rechargeable anti-thrombogenic surface was demonstrated on an expanded polytetrafluoroethylene (ePTFE) vascular graft with reconstitution of the surface bound coating 4 weeks after in vivo implantation in a rat model.

Assessment of Electrospun Pellethane-Based Scaffolds for Vascular Tissue Engineering.

We examined the physicochemical properties and the biocompatibility and hemocompatibility of electrospun 3D matrices produced using polyurethane Pellethane 2363-80A (Pel-80A) blends Pel-80A with gelatin or/and bivalirudin. Two layers of vascular grafts of 1.8 mm in diameter were manufactured and studied for hemocompatibility ex vivo and functioning in the infrarenal position of Wistar rat abdominal aorta in vivo (n = 18). Expanded polytetrafluoroethylene (ePTFE) vascular grafts of similar diameter were implanted as a control (n = 18). Scaffolds produced from Pel-80A with Gel showed high stiffness with a long proportional limit and limited influence of wetting on mechanical characteristics. The electrospun matrices with gelatin have moderate capacity to support cell adhesion and proliferation (~30–47%), whereas vascular grafts with bivalirudin in the inner layer have good hemocompatibility ex vivo. The introduction of bivalirudin into grafts inhibited platelet adhesion and does not lead to a change hemolysis and D-dimers concentration. Study in vivo indicates the advantages of Pel-80A grafts over ePTFE in terms of graft occlusion, calcification level, and blood velocity after 6 months of implantation. The thickness of neointima in Pel-80A–based grafts stabilizes after three months (41.84 ± 20.21 µm) and does not increase until six months, demonstrating potential for long-term functioning without stenosis and as a suitable candidate for subsequent preclinical studies in large animals.

Small-diameter polyurethane vascular graft with high strength and excellent compliance

In this study, a polyurethane vascular graft with excellent strength and compliance for clinical application was designed and fabricated by preparing three small-diameter vascular graft layers via the textile techniques of wet spinning and knitting. The polyurethane filament that was fabricated by wet spinning formed the inner layer. The polyurethane tubular fabric was used as the middle layer. The outer layer was prepared by spraying polyurethane solution. The three layers of the polyurethane vascular graft have uniform wall thickness, high strength, excellent compliance, and good puncture resistance compared with clinical poly(ethylene terephthalate) (PET) and expanded polytetrafluoroethylene (ePTFE) vascular graft. Therefore, these layers can have potential clinical applications in the replacement of the conventional artificial vascular graft prepared from PET and ePTFE.

Development of Multi-layer Tubular Vascular Scaffold to Enhance Compliance by Exhibiting a Negative Poisson’s Ratio

Synthetic small diameter vascular grafts frequently fail owing to intimal hyperplasia, results from mismatched compliance between the vascular graft and native vessels. A vascular graft with a negative Poisson's ratio (NPR, materials expand transversely when pulled axially) was suggested to enhance compliance. We produced a three-layer tubular vascular scaffold with NRP properties. The luminal side consisted of nanosized electrospun fibers for endothelial cell (EC) growth. The middle layer was an NPR structure created using 3D printing, and the outer layer was a microsized electrospun fiber layer for vascular smooth muscle cell (VSMC) growth. The developed multi-layer tubular vascular scaffold contained NPR value. And the NPR vascular scaffold showed 1.7 time higher compliance than the PPR scaffold and 3.8 times higher than that of commercial polytetrafluoroethylene (PTFE) vascular graft. In addition, the ECs and VSMCs were well survived and proliferated on the scaffold during 10 days of culture. From the optimized co-culture condition of the VSMCs and ECs that VSMC phenotype changed was inhibited, we successfully generated a thin luminal layer, which consisted of ECs and the proper thickness of the VSMC layer under the ECs. This scaffold may have a potential to replace conventional artificial vascular graft by providing enhanced compliance and improved cell culture environment.

Silk fibroin vascular graft: a promising tissue-engineered scaffold material for abdominal venous system replacement

No alternative tissue-engineered vascular grafts for the abdominal venous system are reported. The present study focused on the development of new tissue-engineered vascular graft using a silk-based scaffold material for abdominal venous system replacement. A rat vein, the inferior vena cava, was replaced by a silk fibroin (SF, a biocompatible natural insoluble protein present in silk thread), tissue-engineered vascular graft (10 mm long, 3 mm diameter, n = 19, SF group). The 1 and 4 -week patency rates and histologic reactions were compared with those of expanded polytetrafluoroethylene vascular grafts (n = 10, ePTFE group). The patency rate at 1 and 4 weeks after replacement in the SF group was 100.0% and 94.7%, and that in the ePTFE group was 100.0% and 80.0%, respectively. There was no significant difference between groups (p = 0.36). Unlike the ePTFE graft, CD31-positive endothelial cells covered the whole luminal surface of the SF vascular graft at 4 weeks, indicating better endothelialization. SF vascular grafts may be a promising tissue-engineered scaffold material for abdominal venous system replacement.

Expanded polytetrafluoroethylene/silk fibroin/salicin vascular graft fabrication for improved endothelialization and anticoagulation

Clinical application of small-diameter artificial vascular grafts has been hampered by intimal blockages owing to the lack of an endothelial layer and the formation of thrombosis. In this study, an expanded polytetrafluoroethylene (ePTFE) vascular graft was fabricated using a biofriendly ethanol/water mixture as a lubricant and drug carrier. Natural silk fibroin (SF) hydrogel and white willow extract salicin were embedded into ePTFE graft successfully via the ethanol/water lubricant and drug carrier as verified by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The ePTFE graft functionalized by SF hydrogel improved the proliferation of human umbilical vein endothelial cell (HUVEC) due to SF’s hydrophilia and cytocompatibility as measured by the live/dead and cell counting kit-8 (CCK-8) assays. The rapid endothelialization of ePTFE graft helped reduced intimal blockages in vitro. Furthermore, the salicin-modified ePTFE graft exhibited an anticoagulation property as demonstrated by platelet adhesion and activated partial thromboplastin time (APTT) tests. These results suggest that ePTFE graft fabricated with silk fibroin and salicin can be an attractive candidate for vascular grafts.

Biostable highly aligned polyurethane fibres for the potential application of small calibre vascular grafting

AbstractSynthetic vascular grafting is necessarily when the autografting is not possible in some cases. Conventional polyethylene terephthalate and expanded polytetrafluoroethylene vascular grafts are found to be effective for diameter bigger than 6 mm but not for the diameter smaller than 4 mm due to the compliance mismatch and thrombogenicity. Endothelization on the surface of the graft can reduce the risks of compliance mismatch and thrombogenicity. In order to catalyst the endothelization process, fibrous morphology similar to the extracellular matrix of our body is preferable in the vascular grafts. Apart from that, the biostability of the grafts is also an essential element to be considered as the biodegradation may reduce the efficiency of the grafts. Many polyurethanes have been recognised as biostable materials. Hence, in this study, highly aligned polyurethane fibres are fabricated using a facile dry spinning technique in the view of providing effective sites for endothelization process to occur. These fibres are immersed into the simulated body fluid for as long as 24 weeks before conducting the biostability characterisations. The biostability is assessed in three aspects, physical, mechanical and chemical properties. Results show that the fibres do not have observable or significant deteriorations in all the three aspects mentioned.