Polytetrafluoroethylene Vascular Prostheses Research Articles

Modified polymeric biomaterials with antimicrobial and immunomodulating properties

The modification of the surgical polypropylene mesh and the polytetrafluoroethylene vascular prosthesis with cecropin A (small peptide) and puromycin (aminonucleoside) yielded very stable preparations of modified biomaterials. The main emphasis was placed on analyses of their antimicrobial activity and potential immunomodulatory and non-cytotoxic properties towards the CCD841 CoTr model cell line. Cecropin A did not significantly affect the viability or proliferation of the CCD 841 CoTr cells, regardless of its soluble or immobilized form. In contrast, puromycin did not induce a significant decrease in the cell viability or proliferation in the immobilized form but significantly decreased cell viability and proliferation when administered in the soluble form. The covalent immobilization of these two molecules on the surface of biomaterials resulted in stable preparations that were able to inhibit the multiplication of Staphylococcus aureus and S. epidermidis strains. It was also found that the preparations induced the production of cytokines involved in antibacterial protection mechanisms and stimulated the immune response. The key regulator of this activity may be related to TLR4, a receptor recognizing bacterial LPS. In the present study, these factors were produced not only in the conditions of LPS stimulation but also in the absence of LPS, which indicates that cecropin A- and puromycin-modified biomaterials may upregulate pathways leading to humoral antibacterial immune response.

Biventricular repair of double-outlet right ventricle with noncommitted ventricular septal defect using intraventricular conduit

ObjectiveBiventricular repair of double-outlet right ventricle with noncommitted ventricular septal defect is preferred, but previously developed surgical procedures are complicated and associated with high mortality and morbidity. We developed a technique using an intraventricular conduit to connect the ventricular septal defect and the aorta in this anomaly in patients aged more than 2 years. MethodsThirty-one patients (age 2-23 years; median, 5.4) with double-outlet right ventricle with noncommitted ventricular septal defect underwent biventricular repair with intraventricular conduit. A 16-mm or 19-mm polytetrafluoroethylene (Gore-Tex; WL Gore & Associates, Flagstaff, Ariz) vascular prosthesis was used to construct the intraventricular conduit rerouting the ventricular septal defect to the aorta, with enlargement of the ventricular septal defect and resecting the hypertrophic muscular bands in the bilateral conus when necessary. Follow-up was made in all patients with a median duration of 93 months (range, 8-140 months). ResultsOne patient died during hospitalization and 1 patient died at 8 months after operation, making the mortality 6.5%. The peak pressure gradient across the left ventricular outflow tract was less than 30 mm Hg in all patients but 1 (3.3%). In the last patient, it increased from 16 mm Hg early after operation to 50 mm Hg at 7 years follow-up. The peak pressure gradient across the right ventricular outflow tract ranged from 6 to 30 mm Hg in all patients. One patient had moderate mitral regurgitation with New York Heart Association class II. One patient had preoperative severe pulmonary arterial hypertension (mean pressure, 50 mm Hg) and was treated with bosentan. Other patients were in New York Heart Association class I. ConclusionsBiventricular repair with intraventricular conduit is a relatively simple and safe procedure for patients aged more than 2 years with double-outlet right ventricle with noncommitted ventricular septal defect, with excellent early and midterm outcomes.

A pilot study comparing bovine mesenteric artery and expanded polytetrafluoroethylene grafts as non-autogenous hemodialysis options.

Background Many dialysis patients do not have the necessary conditions for construction of a native arteriovenous fistula (AVF). Expanded Polytetrafluoroethylene (ePTFE) vascular prostheses are the most widely-used option, but it is known that they are inferior to native vein AVFs. Objectives To identify a graft with superior performance to ePTFE, comparing their results with those of AVFs made from bovine mesenteric arteries treated with L-Hydro technology (Labcor Laboratories ®). Methods A prospective and controlled study of 10 patients with AVFs constructed with ePTFE and 10 patients with L-Hydro bioprostheses, matched for comorbidities. The variables studied were: primary patency, assisted primary patency, and secondary patency, surgical manipulability, and prevalence of infections. The performance of prostheses was assessed by duplex-scan and repeated consultations with health professionals at hemodialysis clinics. The chi-square test was used for statistical analysis. Results After 1 year of postoperative follow-up, secondary and primary patency rates were higher for L-Hydro than ePTFE AVFs. Fewer interventions were needed to maintain AVF patency in the L-Hydro AVF group. The most common complication was graft thrombosis, which was more frequent in the ePTFE group. While the figures indicate more favorable outcomes in the L-Hydro AVFs, this could not be confirmed with the statistical treatment employed. Conclusions The L-Hydro graft appears to be a valuable alternative option for AVFs, since it seems to require fewer interventions to maintain patency when compared to ePTFE grafts.

Experimental research on the novel small-caliber vascular prosthesis basing on controlled release of heparin from mesoporous channel

Objective To fabricate the mesoporous-based heparin-loaded expanded polytetrafluoroethylene (ePTFE) vascular prosthesis and evaluate their biocompatibility.Methods The study included the mesoporous-based vascular prosthesis group and the control group.The chromogenic assay.Pressing-perfusion test,protein adsorption assay and lactate dehydrogenase (LDH) cytotoxicity assay were determined to evaluate hemocompatibility and compatibility of vascular prosthesis.Results The heparin-released mesoporous-based vascular prosthesis weas synthesized successfully.The chromogenic assay confirmed that heparin-loaded keep lasting activity than the control vascular prosthesis group (P ＜ 0.05).HMVP-n keep compliance of original vascular prosthesis (P ＞ 0.05).The adsorption of fibrinogen on the surface of HMVP-n membranes is effectively reduced (OD values:0.29 ±0.12,0.31 ±0.06 and 0.30 ± 0.07,respectively),but HMVP-n grafts attracted higher amount of albumin (OD values:0.390 ± 0.150,0.327 ± 0.210 and 0.332 ± 0.240,respectively) compared than unmodified ePTFE graft (P ＜ 0.05),HMVP-1 especially.there was not significant difference of A values between HMVP-n and unmodified material (P ＞0.05) by LDH Cytotoxicity Assay.Conclusion The heparin-released mesoporous-based vascular prosthesis keep lasting antithrombotic activity and has good biocompatibility. Key words: Expanded polytetrafluoroethylene; Artificial vascular prosthesis ; Mesoporous ; Heparin; Biocompatibility

Alcohol Pretreatment of Small‐diameter Expanded Polytetrafluoroethylene Grafts: Quantitative Analysis of Graft Healing Characteristics in the Rat Abdominal Aorta Interposition Model

Long-term patency rates of small-diameter expanded polytetrafluoroethylene (ePTFE) vascular prostheses are unsatisfactory. Treatment of ePTFE grafts by alcohol before implantation was reported to increase hydrophilic properties, yielding better endothelialization and cellular in-growth, thus improving graft healing. The effect of alcohol pretreatment on ePTFE grafts and postoperative healing characteristics of wet ePTFE grafts were evaluated in this study. Ten sterile ePTFE grafts (2 mm ID, 30 micro thru-pore, 12 mm long) were implanted in the infrarenal aorta of male Sprague-Dawley rats (324-380 g). Five grafts were treated with ethanol 70% and soaked with saline solution before implantation (wet); five nontreated grafts served as control. All rats were sacrificed after digital subtraction angiography and sampling of the graft for histological investigation after 3 weeks. Histomorphometric analysis was performed for endothelial coverage, cellular in-growth, and intimal hyperplasia. All grafts were patent at the end of 3 weeks in both groups. Histological evaluation revealed significantly better endothelial coverage and prominent infiltration by fibroblasts and lymphocytes in the wet group. Endothelial coverage (31.03 +/- 10.61% vs. 13.03 +/- 9.46%, P = 0.03) and cellular infiltration of grafts (50.91 +/- 8.55% vs. 39.29 +/- 10.70%, P = 0.11) were higher in the wet group. Area of intimal hyperplasia per graft length was also higher in the wet group (5.32 +/- 4.75 microm(2)/microm vs. 2.69 +/- 3.41 microm(2)/microm, P = 0.36). Wetting of ePTFE grafts with ethanol 70% pretreatment before implantation might have a beneficial effect on long-term patency of small-diameter vascular grafts due to facilitated graft healing.

Leakage of the Arterial Prosthesis of an Impella RVAD

Seromas occurring around a vascular graft are a rare complication. We report a life-threatening plasma leakage that occurred through the polytetrafluoroethylene vascular prosthesis of an Impella right ventricular assist device (Impella RD [Impella Cardiosystems GmbH, Aachen, Germany]) implanted in a 62-year-old patient with acute right ventricular failure after cardiac transplantation. The leakage became progressively massive. Weaning the patient from the right ventricular assist device was not possible. The prosthesis was thus wrapped within a pericardial patch to contain the leakage. Three days later the patient could be successfully weaned and the pump was removed. The clinical evolution was favorable.

Synthetic Vascular Prosthesis Impregnated With Mesenchymal Stem Cells Overexpressing Endothelial Nitric Oxide Synthase

Endothelial dysfunction is known to exaggerate coronary artery disease, sometimes leading to irreversible myocardial damage. In such cases, repetitive coronary revascularization including coronary artery bypass grafting is needed, which may cause a shortage of graft conduits. On the other hand, endothelial nitric oxide synthase (eNOS) is an attractive target of cardiovascular gene therapy. The vascular prostheses, of which the inner surfaces are covered with mesenchymal stem cells (MSCs) overexpressing eNOS, are expected to offer feasible effects of NO and angiogenic effects of MSCs on the native coronary arterial beds, as well as improvement of self-patency. Herein, we attempted to develop small caliber vascular prostheses generating the bioactive proteins. Also, we attempted to transduce eNOS cDNA into MSCs. The MSCs were isolated from rat bone marrow and transduced with each adenovirus harboring rat eNOS cDNA and beta-galactosidase (beta-gal) (eNOS/MSCs and beta-gal/MSCs). The beta-gal/MSCs were impregnated into vascular prostheses, then the expressions of beta-gal on the inner surfaces of them were evaluated by 5-bromo-4-chloro-3-indolyl beta-D-galactoside staining. The NOS activity of eNOS/MSCs was assayed by monitoring the conversion of 3H-arginine to 3H-citrulline. The inner surfaces of the vascular prostheses were covered with MSCs expressing beta-gal. The amount of the 3H-citrulline increased, and eNOS/MSCs were determined to generate enzymatic activity of eNOS. This activity was completely inhibited by N(G)-nitro-L-arginine methyl ester. The inner surface of expanded polytetrafluoroethylene vascular prostheses seeded with lacZ gene-transduced MSCs exhibited recombinant proteins. Development of eNOS/MSC-seeded vascular prostheses would promise much longer graft patency and vasculoprotective effects.

Viscoelastic and Functional Similarities Between Native Femoral Arteries and Fresh or Cryopreserved Arterial and Venous Homografts

It is not yet known whether cryopreservation enables vessels to retain their viscoelastic properties or whether cryopreserved homografts are biomechanically more like native arteries than currently used vascular prostheses. The study objectives were: a) to determine whether our cryopreservation methodology enables arterial and venous homografts to retain their viscoelastic and functional properties; and b) to assess similarities between patients' femoral arteries, homografts, and other vascular prostheses in common use. The pressure and the diameter and parietal thickness of 15 muscular (femoral) arteries were measured in patients using tonometry and echography, both noninvasive techniques. In addition, the pressure in and diameter and parietal thickness of 15 fresh and 15 cryopreserved human muscular (femoral) artery segments, saphenous veins, and 15 expanded polytetrafluoroethylene (ePTFE) vascular prostheses were measured in vitro under hemodynamic conditions similar to those in patients. A Kelvin-Voigt model of the segment wall was used to derive elastic (Epd, mm Hg/mm) and viscous (Vpd, mm Hg x s/mm) pressure-diameter indices, the buffering function (Vpd/Epd), and the conduit function (1/Zc, where Zc is the characteristic impedance). The incremental Young modulus, the pressure-strain elastic modulus, and pulse wave velocity were also calculated. No difference was observed between either the viscoelastic or functional properties of fresh and cryopreserved homografts. Arterial homografts were the most similar to the patient's arteries. Cryopreservation enabled venous and arterial homografts to retain their viscoelastic and functional properties. Of all the grafts investigated, arterial homografts were most similar, both biomechanically and functionally, to the patient's femoral arteries.

Differential scanning calorimetric examination of the tracheal cartilage after primary reconstruction with differential suturing techniques

Objective Long segmental tracheal defects often lead to life threatening clinical conditions. Treatment of these lesions still represents an unsolved surgical challenge. The aim of the study was to test the effect of continuous and simple interrupted suturing in the replacement of long segment tracheal defects using polytetrafluoroethylene (PTFE) vascular prosthesis in a rabbit model. Methods 2 cm long segment of the cervical trachea was resected in 20 New Zealand rabbits. The trachea was replaced with reinforced polytetrafluoroethylene vascular graft. The anastomoses were performed telescopically using continuous (group I, n = 10) or simple interrupted sutures (group II, n = 10). Laser Doppler measurements were taken before the resection and following the anastomoses. Length of survivals were noted, the patency and microscopical pattern of the anastomoses were evaluated. Calorimetric examinations were performed to detect possible structural changes in the tracheal cartilage. Results Following the resection local microcirculation decreased by 9 ± 4%. The anastomoses caused a significant decrease of 29% in group I ( p = 0.02) and 13% in group II. The mean survival was 58 ± 17 and 135 ± 25 days, respectively. Calorimetric results showed no change after the resection, but significant shift in melting temperature and calorimetric enthalpy proved the presence of structural changes of the cartilage in group II. Conclusions We saw significant lowering of microcirculation following continuous sutures, while simple interrupted stitches produced only moderate decrease. We found that interrupted suture technique is superior to the continuous technique causing only moderate damage to the tracheal anastomosis.

Synthetic Vascular Prosthesis Impregnated With Genetically Modified Bone Marrow Cells Produced Recombinant Proteins

The aim of this study is to develop an experimental model of small caliber expanded polytetrafluoroethylene (ePTFE) vascular prostheses that produce recombinant proteins by seeding genetically modified bone marrow mesenchymal stem cells (MSC). Beta-galactosidase (beta-gal) cDNA was transduced into rat MSC mediated by an adenovirus vector. The cells were impregnated into the ePTFE vascular prostheses measuring 2 mm in internal diameter and 90 microm in fibril length, followed by 48 h of incubation. The expressions of beta-gal were determined by X-gal staining. The luminal surface of the ePTFE vascular prostheses was covered with the MSC expressing beta-gal. Most of the gene-transduced MSC spread along the fibers forming colonies. These results suggest that small caliber vascular prostheses, in which the inner surface was seeded by genetically modified MSC, produced recombinant proteins. This may be a preliminary model to autocrine functioning vascular prostheses.

Improving arterial prosthesis neo-endothelialization: Application of a proactive VEGF construct onto PTFE surfaces

The formation of a confluent endothelium on expanded polytetrafluoroethylene (PTFE) vascular prostheses has never been observed. This lack of endothelialization is known to be one of the main reasons leading to the development of thromboses and/or intimal hyperplasia. In this context, several efforts were put forward to promote endothelial cell coverage on the internal surface of synthetic vascular prostheses. The goal of the present study was to immobilize the vascular endothelial growth factor (VEGF) onto Teflon ® PTFE surfaces to generate a proactive polymer construct favoring interaction with endothelial cells. An ammonia plasma treatment was first used to graft amino groups on PTFE films. Subsequent reactions were performed to covalently bind human serum albumin (HSA) on the polymer surface and to load this protein with negative charges, which allows adsorbtion of VEGF onto HSA via strong electrostatic interactions. X-ray photoelectron spectroscopy (XPS) experiments along with surface derivatization strategies were performed between each synthesis step to ascertain the occurrence of the various molecules surface immobilization. Finally, the electrostatic binding of VEGF to the negatively charged HSA matrix was performed and validated by ELISA. Endothelial cell adhesion and migration experiments were carried out to validate the potential of this VEGF-containing biological construct to act as a proactive media toward the development of endothelial cells.

Clinical experience with autologous endothelial cell–seeded polytetrafluoroethylene coronary artery bypass grafts

Objective: Autologous endothelial cell seeding was used to improve the patency of 4-mm polytetrafluoroethylene vascular prostheses. Methods: Since 1995, 14 patients with coronary artery disease received 21 autologous endothelial cell–seeded polytetrafluoroethylene vascular bypass grafts for coronary artery revascularization. The polytetrafluoroethylene grafts were seeded with the endothelial cells in a multiple step procedure, including cell culture techniques before coronary bypass operation. With the use of extracorporal circulation and cardioplegic arrest, a bypass operation was performed by means of conventional surgical techniques. Results: After a mean postoperative follow-up of 27.7 months (range, 7.5-48 months), the graft patency rate is 90.5%. Follow-up angiograms of the aorta-coronary polytetrafluoroethylene bypass grafts showed patent bypasses in all cases except two. Angiograms of all 19 patent endothelial cell–seeded polytetrafluoroethylene bypass grafts showed a smooth luminal borderline without stenotic regions. The percutaneous transluminal angioscopic evaluation showed a glossy white and smooth endoluminal graft surface without any fibrin, platelet, or erythrocyte deposits. Intravascular ultrasonographic examinations confirmed the results. Conclusion: Patency of autologous endothelial cell–seeded 4-mm polytetrafluoroethylene vascular prostheses as coronary artery bypass grafts was much better than that of unseeded polytetrafluoroethylene grafts. Further evaluations and a larger population of patients will prove whether the encouraging patency will last. (J Thorac Cardiovasc Surg 2000;120:134-41)

Modeling lipid uptake in expanded polytetrafluoroethylene vascular prostheses and its effects on mechanical properties.

The radial transport across the wall of expanded polytetrafluoroethylene (ePTFE) arterial prostheses has a significant effect on lipid uptake observed in prostheses implanted in humans, which has been postulated to be one of the causes associated with implant failure. The goal of this study was to stimulate radial transport on a lipidic dispersion across the wall of an ePTFE prosthesis and investigate its effects on the circumferential mechanical properties of the prosthesis. An in vitro model was developed to simulate the lipidic radial transport across the wall. Lipids contained in a phosphatidylcholine dispersion were used as the transported molecules. Lipid concentration profiles were obtained after exposing commercial ePTFE prostheses to various transmural pressure and/or lipidic concentration gradients. Phospholipids gradually accumulated up to the external reinforcing wrap of the prosthesis, which clearly acted as a rigid barrier against lipid infiltration. Tensile tests performed on the virgin samples showed that the wrap was much more rigid than the microporous part of the prosthesis. After the lipid simulation, the rigidity of the wrap decreased with respect to what was observed for the virgin prosthesis. Finally, some clinical implications of this phenomena are discussed.

Biocompatible surfaces by immobilization of heparin on diamond-like carbon films deposited on various substrates

Although graphitic carbon has been known and used as a biomaterial for a very long time, the excellent biocompatibility of diamond-like carbon (DLC) films has been addressed only in a few cases. We anticipate the combination of bioinert DLC films and surface-immobilized bioactive biomolecules with antithrombogenic properties, such as the polysaccharide heparin, as a straightforward concept to optimize the haemocompatibility of a wide variety of materials. Therefore, to assess this property in view of an application as vascular grafts, surface analytical studies on DLC-coated and heparinized polymer and silicon substrates were performed. The DLC films were deposited on polytetrafluoroethylene (PTFE), PTFE vascular prostheses, polystyrene and silicon wafers by an energetic acetylene plasma beam and subsequently exposed to an ammonia plasma before heparin was covalently coupled to such functionalized surfaces by an end-point attachment method. The biochemical characterization by thrombin tests revealed, in accordance with XPS measurements, a high amount of heparin on the surface and an extended blood coagulation time. Thus, the efficiency of the plasma treatment for functionalization and successful improvement of the haemocompatibility of DLC films could be shown. Copyright © 2000 John Wiley & Sons, Ltd.

In vitro evaluation of electrostatic endothelial cell transplantation onto 4 mm interior diameter expanded polytetrafluoroethylene grafts

Purpose: To perform an in vitro evaluation of electrostatic endothelial cell transplantation of human umbilical vein endothelial cells (HUVEC) onto segments of 4 mm internal diameter expanded polytetrafluoroethylene (ePTFE) vascular prostheses. Methods: This evaluation consisted of exposing vascular graft segments that had been subjected to either electrostatic or gravitation transplantation with HUVEC to a physiologic shear stress (15 dynes/cm 2) under steady flow conditions within a flow loop system. Biochemical assays were performed on freshly transplanted grafts by means of radioimmunoassay for prostacyclin and thromboxane A 2. Results: There was a 30% loss of HUVEC after 30 minutes of shear stress exposure from the grafts subjected to gravitational transplantation with no additional significant (α = 0.05) loss after 120 minutes. Grafts subjected to electrostatic transplantation had no significant (α = 0.05) loss of HUVEC during exposure to physiologic shear stress. Furthermore, after 120 minutes of shear-stress exposure, the grafts subjected to electrostatic transplantation (78,420 ± 6274 HUVEC/cm 2) retained 2.3 times more HUVEC than the counterparts subjected to gravitational transplantation (34,427 ± 4637 HUVEC/cm 2). The biochemical assay results indicated no significant (α = 0.05) production of prostacyclin or thromboxane A 2 regardless of the method of cell transplantation. Conclusions: (1) The electrostatic transplantation technique was superior to the gravitational transplantation technique in terms of cellular retention when the ePTFE grafts were exposed to physiologic shear stress. (2) Production of prostacyclin and thromboxane A 2 did not differ between transplanted HUVEC subjected to gravitational or electrostatic procedures. (J Vasc Surg 1998;27:504-11.)

Heparin Bonding Increases Patency of Long Microvascular Prostheses

The high thrombogenicity of synthetic biomaterials has limited their use for reconstructive microsurgery. Prime factors in the thrombogenicity of synthetic materials in contact with blood include gas nuclei at the blood gas interface as well as the inherent thrombogenicity of the materials themselves. Expanded polytetrafluoroethylene (ePTFE) vascular prostheses were denucleated by placement in acetone and ethanol followed by degassed saline or by placement in degassed saline subjected to hydrostatic pressure. Heparinized grafts were prepared by coating with tridodecylmethylammonium chloride (TDMAC), followed by immersion in heparin. Grafts were installed to reconstruct the femoral artery (1 x 10 mm) or as renal-iliac bypasses (1 x 50 mm) in rats. In the femoral artery reconstruction model, control grafts thrombosed within 10 minutes of implantation. All acetone denucleated femoral grafts remained patent for 60 minutes but were occluded at day 1. All pressure denucleated femoral grafts remained patent for 60 minutes, whereas six were patent at 1 month. In contrast, 11 of 15 heparinized femoral grafts were patent at 1 month. In the renal iliac bypass model, all control grafts were thrombosed within 10 minutes, whereas all heparin bonded grafts remained patent at 1 month. This finding confirms that removal of air from small diameter ePTFE grafts decreases acute thrombogenicity and that heparin bonding further decreases thrombogenicity, suggesting that clinically useful lengths of microvascular prostheses may be possible.

Rabbit Model for the Study of Aortic Graft Infection

Despite improvements in surgical technique and antimicrobial therapy, prosthetic aortic graft infections remain a challenging clinical problem. Diagnosis is difficult, and treatment results are less than optimal. An animal model is needed that will allow critical investigation of novel approaches in the therapy of aortic graft infections. Three-millimeter internal diameter polytetrafluoroethylene vascular prostheses were anastomosed as aortic interposition grafts in 25 rabbits. Increasing concentrations of Staplglococcus aureus (no bacteria to 1 × 108) were applied topically to inserted grafts to initiate infection. There were 15 long-term survivors. Surviving rabbits were sacrificed at 2 weeks postoperatively to evaluate the development of aortic graft infection. Of the 15 survivors, 6 developed graft infection. All infected prosthetic aortas were innoculated with 1 × 104 or higher concentrations of S. aureus. A cost-effective, reliable model has been developed suitable for the study of prosthetic aortic infection.

Improved endothelial cell attachment on ePTFE vascular grafts pretreated with synthetic RGD-containing peptides

To assess endothelial cell (EC) attachment in seeding of expanded polytetrafluoroethylene (ePTFE) vascular prostheses by application of a new technique of coupling synthetic RGD-containing peptides with the graft surface. Prospective, open study. University Department of Cardiovascular Surgery and Institute of Biochemistry. ePTFE vascular grafts (group 1) uncoated (group 2) coated with fibronectin (group 3) coated with a RGD-containing peptide or (group 4) coated in a similar way to group 3 but without application of a RGD-peptide, were incubated for 30 min with adult human saphenous vein endothelial cells. After seeding, grafts were exposed to shear stress in an artificial flow circuit. EC attachment after seeding and retention after perfusion was assessed by scanning electron microscopy and image analysis. Both EC attachment and retention were significantly increased by coating with fibronectin in comparison to uncoated ePTFE. Graft coating with an RGD-peptide lead to the highest increase in EC attachment (30.6% +/- 2.1%) and retention after shear stress (62.9% +/- 7.5%) compared to fibronectin coated (26.0% +/- 3.3%/45.5% +/- 2.1%), uncoated (14.9% +/- 3.1%/13.9% +/- 7.9%) and similar coated ePTFE grafts without application of a RGD-peptide (10.5% +/- 1.1%/6.6% +/- 1.5%). EC attachment on uncoated ePTFE vascular prostheses is very weak. Our technique of coupling the ePTFE graft surface with cell adhesion promoting RGD-containing synthetic peptides significantly improved this decisive step in endothelial cell seeding of ePTFE grafts.

Expanded polytetrafluoroethylene arterial prostheses in humans: chemical analysis of 79 explanted specimens

The expanded polytetrafluoroethylene (ePTFE) vascular prostheses are widely used as small and medium diameter blood conduits when an autologous venous material is not available or is not suitable. The long-term performance of a prosthesis is dependent on several factors, including its healing characteristics and its stability in vivo. This study was undertaken to assess whether chemical degradation of ePTFE occurs when such arterial substitutes are implanted in humans. Seventy-nine ePTFE grafts excised for complications were analysed using the following techniques: measurement of the contact angle (θ), electron spectroscopy for chemical analysis (ESCA or XPS), Fourier transform infra-red spectroscopy (FTIR) and differential scanning calorimetry (DSC). The results were compared with those obtained from virgin ePTFE and virgin ePTFE washed prostheses. The measurement of the contact angle (θ) permits the comparison of the level of hydrophobicity of material after in vivo residency. The contact angles of explanted ePTFE grafts are greater than those of virgin ones but remain close to those of washed virgin prostheses. The ESCA method allowed investigation of the chemical changes which occur on the surface of ePTFE prostheses after implantation because of the low penetration of the X-ray (about 50 Å). This study did not reveal any chemical degradation of the ePTFE with time of implantation for periods up to 6.5 yr. Changes in the surface composition were probably related to lipid and/or protein uptake. The FTIR spectroscopy provides information about the chemical composition of material. Compared with the virgin ePTFE prostheses, the FTIR spectra of explanted prostheses showed specific bands which are characteristic of lipid and/or protein absorptions. The bulk properties of ePTFE studied by DSC did not show any significant changes with time of implantation. It is concluded that ePTFE grafts remain stable in vivo for periods up to 6.5 yr.

Expanded polytetrafluoroethylene arterial prostheses in humans: histopathological study of 298 surgically excised grafts

The expanded polytetrafluoroethylene vascular prosthesis is considered to be the best synthetic alternative for peripheral arterial reconstruction. Most studies on the healing characteristics of expanded polytetrafluoroethylene prostheses have been carried out on animals, and very few data are available on prostheses implanted in humans long term. We implanted 298 expanded polytetrafluoroethylene grafts as arterial substitutes in humans. The mean duration of implantation was 523 d and the grafts were implanted mainly for infrainguinal or axillofemoral bypass. The cellular and collagen infiltration of the microporous expanded polytetrafluoroethylene structure was generally poor. Infiltration occurred mainly in the external region of the prosthetic wall and increased with the duration of implantation. The external reinforcement was not a major factor in limiting tissue infiltration. The luminal surfaces were covered with a thin, irregular layer of organized fibrin, interspersed with exposed expanded polytetrafluoroethylene areas. Mineral deposits were observed in five cases. Despite poor healing, the clinical performance of expanded polytetrafluoroethylene vascular prostheses is relatively good. Since the chief advantage of this material is good mechanical stability in vivo, any modifications of the graft to improve healing characteristics or thrombogenic properties should not be made at the expense of stability in vivo.