Artificial Circulation System Research Articles

Multiwavelength tissue-mimicking phantoms with tunable vessel pulsation

For the development and routine characterization of optical devices used in medicine, tissue-equivalent phantoms mimicking a broad spectrum of human skin properties are indispensable. Our work aims to develop a tissue-equivalent phantom suitable for photoplethysmography applications. The phantom includes the optical and mechanical properties of the three uppermost human skin layers (dermis, epidermis, and hypodermis, each containing different types of blood vessels) plus the ability to mimic pulsation. While the mechanical properties of the polydimethylsiloxane base material are adjusted by different mixing ratios of a base and curing agent, the optical properties are tuned by adding titanium dioxide particles, India ink, and synthetic melanin in different concentrations. The layered structure of the phantom is realized using a doctor blade technique, and blood vessels are fabricated using molding wires of different diameters. The tissue-mimicking phantom is then integrated into an artificial circulatory system employing piezo-actuated double diaphragm pumps for testing. The optical and mechanical properties of human skin were successfully replicated. The diameter of the artificial blood vessels is linearly dependent on pump actuation, and the time-dependent expansion profile of real pulse forms were mimicked. A tissue equivalent phantom suitable for the ex-vivo testing of opto-medical devices was demonstrated.

Cardiac surgery-associated acute kidney injury

This literature review is devoted to one of the topical multidisciplinary problems of modern clinical practice the development of acute kidney injury after cardiac surgery. The prevalence of this pathology varies on average from 5 to 43 %, while the frequency of early hospital mortality increases significantly in the population of such patients compared with patients without cardiac surgery-associated renal damage. It is assumed that the work of the artificial circulatory system contributes to the development of such complications, but as shown by many studies, the etiology of such kidney damage is multifactorial and cannot be explained by only one pathogenetic mechanism. The article highlights the current understanding of the etiology, pathogenesis and risk factors of acute kidney injury after cardiovascular interventions, describes new markers of early detection of renal dysfunction, and describes some prognostic aspects of the disease. Early identification and stratification of risk groups will allow for a timely preventive strategy, which will significantly improve early and long-term postoperative outcomes in such patients.

The composition of vulnerable plaque and its effect on arterial waveforms

Carotid plaque composition is a key factor of plaque stability and it carries significant prognostic information. The carotid unstable plaques are characterized by a thin fibrous cap (FC) ≤65μm with large lipid core (LC), while stable plaques have a thicker FC and less LC. Identifying the percentage of plaque compositions could help surgeons to make a precise decision for their patients’ treatment protocol. This study aims to distinguish between stable and unstable plaque by defining the relationship between plaque composition and arterial waveform non-invasively. An in-vitro arterial system, composed of a Harvard pulsatile flow pump and artificial circulation system, was used to investigate the effect of the plaque compositions on the pulsatile arterial waveforms. Five types of arterial plaques, composed of the LC, FC, Collagen (Col) and Calcium (Ca), were implemented into the artificial carotid artery to represent the diseased arterial system with 30% of blockage. The pulsatile pressure, velocity and arterial wall movement were measured simultaneously at the site proximal to the plaque. Non-invasive wave intensity analysis (Non-WIA) was used to separate the waves into forward and backward components. The correlation between the plaque compositions and the reflected waveforms was quantitatively analysed. The experimental results indicate that the reflected waveforms are strongly correlated with the plaque compositions, where the percentages of the Col are linearly correlated with the amplitude of the backward diameter (correlation coefficient, r = 0.74) and the lipid content has a strong negative correlation with the backward diameter (r = 0.82). A slight weak correlation exists between the reflected waveform and the percentage of Ca. The strong correlation between the compositions of the plaques with the backward waveforms observed in this study demonstrates that the components of the arterial plaques could be distinguished by the arterial waveforms. This finding might lead to a potential novel non-invasive clinical tool to determine the composition of the plaques and distinguish between stable and vulnerable arterial plaques at the early stage.

Design, Implementation, and Validation of a Pulsatile Heart Phantom Pump

The developments in Computed Tomography (CT) and Magnetic Resonance allow visualization of blood flow in vivo using these techniques. However, validation tests are needed to determine a gold standard. For the validation tests, controllable systems that can generate pulsatile flow are needed. In this study, we aimed to develop an affordable pulsatile pump and an artificial circulatory system to simulate the blood flow for validation purposes. Initially, the prerequisites for the phantom were pulsating flow output equal to that of the human cardiac pulse pattern; the flow pattern of the mimicked cardiac output should be equal to that of a human, a variable stroke volume (40–120 ml/beat), and a variable heart rate (60–170 bpm). The developed phantom setup was tested with CT scanner. A washout profile was created based on the image intensity of the selected slice. The test was successful for a heart rate of 70 bpm and a stroke volume of 68 ml, but the system failed to work at various heartbeats and stroke volumes. This was due to the problems with software of the microcontroller. As conclusion in this study, we present a proof of concept for a pulsatile heart phantom pump that can be used in validation tests.

Stable Low-Dose Oxygen Release Using H2O2/Perfluoropentane Phase-Change Nanoparticles with Low-Intensity Focused Ultrasound for Coronary Thrombolysis

After the onset of myocardial infarction, extensive coronary thrombus and oxygen supply insufficiency lead to severe myocardial damage and heart failure. Recently, ultrasound-irradiated phase-change nanoparticles have been recognized for their cardiovascular thrombolysis potential. Therefore, we sought to establish a novel treatment method using hydrogen peroxide (H2O2)/perfluoropentane (PFP) phase-change nanoparticles with low-intensity focused ultrasound (LIFU) for the simulation of acute coronary thrombolysis and myocardial preservation. There were three groups in our study: Group A consisted of phosphate-buffered saline (PBS) as the blank control, group B consisted of SonoVue microbubbles and group C consisted of H2O2/PFP phase-change nanoparticles. The H2O2/PFP phase-change nanoparticles were prepared using a double-emulsification process. The in vitro experiments were conducted in an artificial circulatory system connected to an LIFU system and dissolved oxygen detector. Thrombolysis efficiency and oxygen release efficiency were compared among the groups. H2O2/PFP nanoparticles with 3% H2O2 (average size: 456.7 ± 31.2 nm, charge: –37.5 ± 5.22 mV) was the optimal selection in group C because of the stable loading capacity and stable low-dose oxygen release efficiency in the in vitro experiments. Thrombolytic weight loss and loss rates in group C (322.0 ± 40.8 mg, 54.8 ± 5.7%) were significantly higher than those in group A (36.2 ± 18.1 mg, 5.5 ± 2.5%) and group B (91.0 ± 11.9 mg, 14.3 ± 2.4%) (p < 0.01). The innovative method using H2O2/PFP phase-change nanoparticles with LIFU exhibited high thrombolytic efficiency and stable low-flow oxygen supply in the artificial circulatory system, providing a solid experimental foundation for the establishment of a novel treatment method for acute myocardial infarction.

Artificial Circulatory Model for Analysis of Human and Artificial Vessels

Background: Ex vivo computer controlled circulatory reactors are advantageous for the investigation of circulatory systems. So far, most of the models have dealt with laminar or pulsatile flow. This study aimed to monitor blood vessel and vessel graft compliance continuously under physiological flow in real time. Methods: Human common iliac arteries and silicon tubes served as interposition grafts. Changes in wall diameter and displacement were analyzed. The artificial circulatory system (ACM) presented an “artificial heart” able to simulate various ejection pressures, ejection volumes (EV), and frequencies of pulsation (FP). ACM was validated by comparing medical data reconstructed with the 2D-speckle-tracking-technique (2DSTT). Results: Silicon tubes were more rigid compared to iliac arteries, as changes in diameter were approximately 48% lower (0.56 ± 0.007 mm vs. 0.83 ± 0.016 mm, p &lt; 0.0001, for EV = 70 mL and FP = 60 min−1). Wall displacement was 2.3-fold less pronounced in silicon tubes (1.45 ± 0.032 mm vs. 5.79 ± 0.043 mm for iliac arteries (p &lt; 0.0001)). FP and EV did not further increase differences in wall displacement between both types of grafts. There were no significant changes between results gathered from ACM and 2DSTT. Conclusions: The ACM was successfully validated by 2DSTT with the use of selected grafts. It may become a useful tool to investigate different types of vascular grafts.

2B13 ヒト動脈の診断デバイス開発のための人工循環器における脳波プロファイルデザイン

2B13 ヒト動脈の診断デバイス開発のための人工循環器における脳波プロファイルデザイン

Using 6% Hydroxyethyl Starch (HESPAN) as an Indicator to Measure Plasma Volume in Whole Blood

PURPOSE: The present in vitro study tested the validity of using 6% hydroxyethyl starch (HESPAN) as an indicator to measure plasma volume (PV) in whole blood. METHODS: 30-mL of whole blood was collected from seven subjects (4 males, 3 females; ages 19-61) in sealed tubes containing EDTA. PV was determined from whole blood samples using the formula PV=BV(100-0.87(Hct))/100 where; BV= blood volume and Hct= hematocrit. Each blood collection was inserted into an artificial circulation system constructed from tubing and a peristalsis pump. A sufficient quantity of HESPAN was then added to the blood generating a HESPAN:PV ratio of 1:10. The HESPAN-infused blood was allowed to circulate for five minutes before being withdrawn, centrifuged, and allocated to eight 0.6-mL aliquots of plasma. These plasma aliquots underwent acid hydrolysis using 0.15-mL of concentrated HCl that was heated in a boiling water bath. The samples were then neutralized using 0.55-mL of 3.33-M TRIS buffer, cooled to room temperature, and centrifuged to yield a clear supernatant. The glucose concentration of the supernatant was measured against a baseline plasma sample that was handled identically without added HESPAN. The difference in glucose concentration was calculated and related to a known concentration standard. The estimated PV was compared to the known PV that was previously determined. RESULTS: The average difference between the known PV and the estimated PV was 0.51±1.49-mL, which represents 4.79% of the average PV of 10.9-mL. CONCLUSIONS: HESPAN may be a valid indicator to measure PV when added to whole blood in an in vitro artificial circulation.

A preliminary study to measure plasma volume using hydroxyethyl starch (707.6)

Purpose: This study tested the potential of using hydroxyethyl starch (HESPAN) as an indicator to measure plasma volume. Methods: Fifty‐ml of whole blood was collected in tubes containing EDTA from ten subjects (n=10, male=6, female=4) between the ages of 18 and 60. The blood samples were centrifuged at 3000‐rpm for 20 min. The plasma was removed and inserted into an artificial circulation system constructed from Tygon tubing, a central mixing chamber, and a peristaltic pump. For each subject, the initial glucose level was measured using an Accu‐Chek Active glucose monitor. Ten 0.5‐ml aliquots of a 6% HESPAN solution were sequentially added into the system and allowed to circulate for a period of six minutes. Two‐mL plasma samples were withdrawn between the additions of each aliquot, treated with concentrated hydrochloric acid for hydrolysis of the HESPAN starch to glucose monosaccharide units, and neutralized with TRIS buffer. The resulting samples were then used to measure the increase in plasma glucose concentration. Results: A graph was constructed displaying the relationship between HESPAN concentration and increases in plasma glucose levels. It was determined that there was a nearly linear relationship resulting in an r2 value of 0.9395. Conclusions: Using HESPAN, as an indicator may be valid technique to measure plasma volume due to the linear relationship between HESPAN concentration increases in plasma glucose.

Strain Measurement of Abdominal Aortic Aneurysm with Real-time 3D Ultrasound Speckle Tracking

Abdominal aortic aneurysm rupture is caused by mechanical vascular tissue failure. Although mechanical properties within the aneurysm vary, currently available ultrasound methods assess only one cross-sectional segment of the aorta. This study aims to establish real-time 3-dimensional (3D) speckle tracking ultrasound to explore local displacement and strain parameters of the whole abdominal aortic aneurysm. Validation was performed on a silicone aneurysm model, perfused in a pulsatile artificial circulatory system. Wall motion of the silicone model was measured simultaneously with a commercial real-time 3D speckle tracking ultrasound system and either with laser-scan micrometry or with video photogrammetry. After validation, 3D ultrasound data were collected from abdominal aortic aneurysms of five patients and displacement and strain parameters were analysed. Displacement parameters measured in vitro by 3D ultrasound and laser scan micrometer or video analysis were significantly correlated at pulse pressures between 40 and 80 mmHg. Strong local differences in displacement and strain were identified within the aortic aneurysms of patients. Local wall strain of the whole abdominal aortic aneurysm can be analysed in vivo with real-time 3D ultrasound speckle tracking imaging, offering the prospect of individual non-invasive rupture risk analysis of abdominal aortic aneurysms.

Hydrodynamic comparison of biological prostheses during progressive valve calcification in a simulated exercise situation. An in vitro study

Despite continuous development of anticalcification treatment for biological valve prostheses, calcification remains one major cause of structural failure. The following study investigates hemodynamics and changes in opening and closing kinematics in progressively calcified porcine and pericardial valves in a simulated exercise situation. Five pericardial (Edwards Perimount Magna) and five porcine (Medtronic Mosaic Ultra) aortic valve bioprostheses (23 mm) were investigated in an artificial circulation system (150 beats/min, cardiac output 8l/min). Leaflet kinematics were visualized with a high-speed camera (3000 frames/s). Valves were exposed to a calcifying solution for 6 weeks. Repeated testing was performed every week. All prostheses underwent X-ray and photographic examination including measurement of calcium content for evaluation of progressive calcification. In the exercise situation pericardial valves demonstrated lower pressure gradients initially compared to the porcine valves (8.5+/-1.4 vs 11+/-1.6 mmHg), but significantly higher closing volume (5.3+/-1.2 ml vs 1.2+/-0.2 ml of stroke volume) leading to an equal total energy. Neither valve type demonstrated a significant increase in gradient or closing volume compared to the normal output situation. Opening and closing times were longer for pericardial valves after 6 weeks (opening time 42+/-10 ms vs 28+/-10 ms, closing time 84+/-12 vs 52+/-10 ms after 6 weeks). Pericardial valves calcified faster and more severely leading to an increase in gradients and closure volume. In the exercise situation pericardial valves demonstrated superior systolic function compared to porcine valves. Therefore pericardial valves have some advantage in active patients due to the lower gradients. Total energy loss remained constant during progressive calcification for both valves. Leaflet opening and closing is faster in porcine valves; clinical impact of these findings is not known. Diastolic performance is also important and should always be tested also in vivo.

Flow-induced permeation of non-occlusive blood clots: an MRI study and modelling

The success of clot thrombolysis very much depends on efficient clot permeation with blood plasma carrying the thrombolytic agent. In this paper clot permeation was studied by dynamic magnetic resonance imaging (MRI) on artificial non-occlusive blood clots inserted in an artificial circulation system filled with blood plasma to which an MRI contrast agent was added. The MRI results revealed that clot permeation is much faster and more efficient at the entrance of the flow channel across the clot. Clot permeation with fluid was simulated numerically as well. The simulation was based on numerical solution of Navier-Stokes equations for the flow in the channel and within the clot. The clot was considered as a porous material with known permeability and porosity. Based on the calculated velocity profiles, concentration profiles of fluid in the clot were modelled. These agreed well with the MRI results. The presented model of clot permeation with fluid may also serve as a useful extension to numerical modelling of dissolution of non-occlusive blood clots during thrombolytic therapy.

STUDY OF FACILITY SCALE FOR PREVENTION OF WATER BLOOM BY ARTIFICIAL CIRCULATION

We investigated the relationship between the abundance of cyanobacteria and stratification intensity N2 in three eutrophicated reservoirs in which an artificial circulation system had been installed and the effects of the facility scale on that relationship. Cyanobacteria markedly increased when N2 was above 10-4 [s-2] in all three reservoirs whether the artificial circulation was installed or not. A certain facility scale wais needed for the decrease of N2. Sufficient decrease in N2 by the facility occurred in the reservoir in which cyanobacteria was prevented. The appropriate facility scale to decrease N2 was considered to be related to the internal Froude number inherent in each reservoir.

Opening and closing kinematics of fresh and calcified aortic valve prostheses: An in vitro study

In vitro testing of biologic valves has been performed using only fresh but treated valves suitable for patient implantation. The present study investigates changes in hemodynamic performance and leaflet kinematics in progressively calcified porcine and pericardial aortic valve prostheses. Edwards Perimount Magna (Edwards Lifesciences, Irvine, Calif) (n = 5) and Medtronic Mosaic Ultra (Medtronic Inc, Minneapolis, Minn) (n = 5) heart valves (23 mm) were investigated in an artificial circulation system (70 beats/min, cardiac output 5 L/min). Leaflet kinematics were visualized with a high-speed camera (3000 frames/sec). Valves were then exposed to a calcium-phosphate solution at a constant pulse rate of 300 beats/min for a total of 6 weeks. Repeated testing was performed after 1, 2, 3, 4, and 6 weeks of calcification. The calcification process might not be similar to in vivo performance. Initially, the Perimount Magna valves demonstrated lower pressure gradients compared with the Mosaic Ultra valves (9.7 +/- 0.36 mm Hg vs 14.0 +/- 1.16 mm Hg), but they showed higher closing volume and leakage flow. Total energy loss was equivalent after 1 week of calcification. Perimount Magna valves calcified significantly faster and more severely, leading to an increase in gradients and closure volume. Leaflet kinematics showed progressively longer opening and closing times for the pericardial valves (closing time Perimount Magna 135 +/- 11 msec vs Mosaic Ultra 85 +/- 9 msec after 6 weeks). On the basis of visual inspection, despite the new ThermaFix (Edwards Lifesciences) tissue treatment, the Perimount Magna pericardial valves calcified in vitro faster and more severely than did the Mosaic Ultra porcine valves, which demonstrated a more constant performance throughout the calcification process. Leaflet kinematics showed a progressive prolongation of opening and closing times for pericardial valves, leading to higher closing volume.

The Effect of Surface Roughness on Activation of the Coagulation System and Platelet Adhesion in Rotary Blood Pumps

The surface roughness of left ventricular assist devices (LVADs) is important for the biocompatibility of blood pumps. However, little is known about the effect of surface roughness on the antithrombogenicity of the device. The present study investigated the effect of surface roughness on the activation of the coagulation system and platelet adhesion in an impeller-type blood pump. Three identical Baylor Gyro 710 centrifugal blood pumps (Baylor College of Medicine, Houston, TX, USA) were manufactured with impeller surface roughness of 0.05, 0.2, and 0.4 microm, respectively, as determined by a stylus profilometer and by scanning electron microscopy. Whole blood was anticoagulated (1-IU heparin/mL, ACT 250 s) and circulated for 60 min in an artificial circulatory system, simulating LVAD perfusion (5-L/min flow against 100 mm Hg). Enzyme-linked immunosorbent assays were developed to quantify fibrinogen- and von Willebrand factor (vWf) adsorption as well as platelet adhesion directly on the impellers of the pumps. Levels of prothrombin fragment F1.2 and thrombin-antithrombin (TAT) complex were measured in order to quantify activation of coagulation. Compared with the 0.05-microm surface, platelet adhesion was 40 and 76% higher on the 0.2- and 0.4-microm surface, respectively (P < 0.01). The evaluation of adsorbed fibrinogen and vWf showed significant higher protein antigen levels on the rougher surfaces (P < 0.01). Furthermore, nonpulsatile perfusion activated the coagulation system. By contrast, the surface roughness had no significant influence on plasma prothrombin F1.2 fragment- and TAT concentrations. Antithrombogenicity was significantly reduced in pumps with inferior metal-finishing quality.

Effect of intraluminal thrombus on pressure transmission in the abdominal aortic aneurysm

To clarify the effect of intraluminal thrombus on pressure transmission. A saccular aneurysm was inserted into an artificial circulation system. Subsequently, the saccular aneurysm was filled with eight different human aortic aneurysm thrombus samples. Starch solution in an empty aneurysm was used as a control. A pressure sensor measured the pressure in the circulation, and a second piezoelectric sensor measured the pressure in the saccular aneurysm at 3, 2, and 1 cm from the endoluminal surface (23 locations). The influence of the elastic characteristics of the aneurysm wall on the extent of pressure reduction was evaluated by experiments performed with aneurysms made of rubber and paraffin. The pressures measured in the empty aneurysm were identical to those measured in circulation (P > .05). The pressure measured in the thrombus was significantly lower than the pressure measured in the circulation (P < .05). The mean pressure ratio between the systolic thrombus pressure and systolic circulation pressure at 1, 2, and 3 cm was 0.90 +/- 0.09, 0.86 +/- 0.10, and 0.81 +/- 0.09, respectively. However, there was a clear correlation between the pressure in the circulation and in the thrombus (Pearson correlation coefficient: mean, r = 0.997; range, 0.975-0.999; P < .01). The change in circulatory pressure was followed by an almost identical change in thrombus pressure (regression coefficient: mean, beta = .997; range, .983-1.000; P < .01). In stiff aneurysms, the pressure reduction is less than in more compliant ones (P < .05). In an in vitro model, pressure in the aneurysmal sac is reduced by fibrinous thrombus. Endovascular aneurysm repair (EVAR) aims at reducing the pressure in the aneurysmal sac. Therefore, it seems attractive to use pressure monitoring in the aneurysmal sac as a follow-up after EVAR. This study contributes to the development of the rationale of pressure monitoring in the aneurysmal sac as a follow-up method after EVAR. The aneurysmal sac is filled with thrombus. To interpret pressure measurements in the thrombus, we have to learn about the effect of the thrombus on pressure transmission and on the pressure measurements themselves. Our study demonstrates that reduction of pressure occurs as it is transmitted through a human aortic thrombus.

Rotational in vitro compliance measurement of diverse anastomotic configurations: a tool for anastomotic engineering

Anastomotic configurations with a small internal diameter are prone to intimal hyperplasia which can cause occlusion within weeks or months. A link between intimal hyperplasia and inhomogenities of the elastic profile of the anastomosis has been established, making anastomotic engineering directed towards smoothing the compliance profile at the anastomotic site essential. Methods to date restrict the anastomotic compliance measurement to one plane. We present a method by which the anastomotic configurations are rotated, thereby allowing an anastomotic elastic profile assessment in multiple planes. Eight end-to-end anastomoses (ovine common carotid artery) and three end-to-side anastomoses (e-PTFE graft to ovine common carotid artery) were prepared and mounted in an artificial circulation system. Anastomotic circumferential compliance (maximal–minimal diameter/(maximal–minimal pressure·minimal diameter)) was measured by means of a laser-scan-micrometer and a Statham pressure transducer. By rotating end-to-end anastomoses, the compliance was measured in three, and in end-to-side anastomoses in four different planes. Multiplanar compliance variability in areas remote to both end-to-end and end-to-side anastomoses was approximately 9%. At the suture line the variability was approximately 22% in end-to-end anastomoses and 78% in end-to-side anastomoses. These results show that local factors result in different compliance profiles when utilizing a multiplanar technique, particularly in end-to-side anastomoses. The rotational apparatus is a tool which can be used to more accurately engineer a homogeneously compliant anastomosis, with the ultimate goal of prolonging anastomotic patency.

A Process to Make Collagen Scaffolds with an Artificial Circulatory System using Rapid Prototyping

ABSTRACTTissue engineering aims to produce biological substitutes to restore or repair damaged human tissues or organs. The principle strategy behind tissue engineering involves seeding relevant cell(s) onto porous 3D biodegradable scaffolds. The scaffold acts as a temporary substrate where the cells can attach and then proliferate and differentiate. Collagen is the major protein constituent of the extracellular matrix in the human body and therefore an attractive scaffold material. Current collagen scaffolds are foams which limit the mass transport of oxygen and nutrients deep into the scaffold, and consequently cannot support the growth of thick-cross sections of tissue (greater than 500 μm). We have developed a novel process to make collagen and collagen-hydroxyapatite scaffolds containing an internal artificial circulatory system in the form of branching channels using a sacrificial mould, casting and critical point drying technique. The mould is made using a commercial rapid prototyping system, the Model-Maker II, and is designed to possess a series of connected shafts. The mould is dissolved away and the solvent itself removed by critical point drying with liquid carbon dioxide. Processed hydroxyapatite has been characterised by XRD and FTIR analysis. Tissue engineering with collagen scaffolds possessing controlled internal microarchitecture may be the key to growing thick cross-sections of human tissue.

Effects of amide and amine plasma-treated ePTFE vascular grafts on endothelial cell lining in an artificial circulatory system

We sought to examine whether surface modification of expanded polytetrafluoroethylene (ePTFE) vascular grafts might extend graft patency without modifying the graft structure. Amide and amine plasma (butylamine) were applied to graft surfaces using radio frequency glow discharge. Surface analyses by Fourier transform infrared spectroscopy-attenuated total reflectance, X-ray photoelectron spectroscopy, and dynamic contact angle measurements revealed the presence of nitrogen-containing functional groups on the plasma modified graft surfaces, along with an increased surface hydrophilicity. Bovine aortic endothelial cells were seeded on amide and amine plasma coated ePTFE vascular grafts and placed inside an artificial circulatory system under well-defined flow conditions. The seeded endothelial cells were exposed to either constant or pulsatile flow condition for 5 days. Their corresponding maximum wall shear stresses were 1 dyn/cm2 under constant flow and 65, 108, and 259 dyn/cm2 under various pulsatile flows. Plasma modified ePTFE vascular grafts enhanced the endothelial cell lining under constant and pulsatile flow conditions. Fluorescence nuclear staining, scanning electron microscopy, and histological staining indicated the formation of an endothelial cell monolayer on the plasma coated graft surfaces.

Effects of amide and amine plasma‐treated ePTFE vascular grafts on endothelial cell lining in an artificial circulatory system

We sought to examine whether surface modification of expanded polytetrafluoroethylene (ePTFE) vascular grafts might extend graft patency without modifying the graft structure. Amide and amine plasma (butylamine) were applied to graft surfaces using radio frequency glow discharge. Surface analyses by Fourier transform infrared spectroscopy-attenuated total reflectance, X-ray photoelectron spectroscopy, and dynamic contact angle measurements revealed the presence of nitrogen-containing functional groups on the plasma modified graft surfaces, along with an increased surface hydrophilicity. Bovine aortic endothelial cells were seeded on amide and amine plasma coated ePTFE vascular grafts and placed inside an artificial circulatory system under well-defined flow conditions. The seeded endothelial cells were exposed to either constant or pulsatile flow condition for 5 days. Their corresponding maximum wall shear stresses were 1 dyn/cm2 under constant flow and 65, 108, and 259 dyn/cm2 under various pulsatile flows. Plasma modified ePTFE vascular grafts enhanced the endothelial cell lining under constant and pulsatile flow conditions. Fluorescence nuclear staining, scanning electron microscopy, and histological staining indicated the formation of an endothelial cell monolayer on the plasma coated graft surfaces. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 42, 188–198, 1998.