Five types of polyurethane vascular grafts in dogs: the importance of structural design and material selection.

Five polyurethane vascular grafts with three different chemistries were investigated in terms of device function, healing characteristics and material stability in a canine abdominal aorta model for prescheduled periods of 1 and 6 months. Corvita-reinforced grafts, with walls made of poly(carbonate urethane) (PCU) filaments, displayed a relatively thin, uniform and partially endothelialized inner capsule with good tissue in-growth. The external polyester mesh separated from the underlying PCU wall due to the degradation of the melt adhesive between these two layers.

Newly developed hybrid suture without lubricant: noninvasive in vivo assessment of biocompatibility with multiparametric MR imaging.

Magnetic resonance imaging (MRI) and magnetic resonance (MR) relaxometry were used to assess noninvasively the tissue response of a new uncoated hybrid braided suture made from a combination of ultra-high-molecular-weight polyethylene (UHMWPE) and polyester (polyethylene terephthalate) (PET) yarns in comparison to a silicone impregnated braided 100% polyester (PET) control suture (Ticron). Both biomaterials were monitored for a period of 30 days following implantation in both incised and nonincised paravertebral rabbit muscles. In all cases, MR images and relaxometry demonstrated that the hybrid suture elicited either a milder or a similar tissue and cellular response compared to the control suture.

In vitro homogeneous and heterogeneous degradation of poly(epsilon-caprolactone/polyethylene glycol/L-lactide): The absence of autocatalysis and the role of enzymes.

This study investigated the in vitro degradation behavior of poly(epsilon-caprolactone/polyethylene glycol/L-lactide) (PCEL) in comparison with that of three other biodegradable polymers. Polymer membranes were incubated in pancreatin solution, Ringer's solution, and distilled water at 37 degrees C for up to 20 weeks. Characterization involved measuring weight loss, observing the morphological changes by scanning electron microscopy (SEM), analyzing molecular weight using size exclusion chromatography (SEC), and studying the crystalline structure using differential scanning calorimetry (DSC).

Evaluation of biodegradable synthetic scaffold coated on arterial prostheses implanted in rat subcutaneous tissue.

Polyester arterial prostheses impregnated with various synthetic biodegradable materials and with gelatin were implanted subcutaneously in rats for 3-180 days. The inflammation was assessed by quantifying the activity of alkaline phosphatase and by histology. The degradation of the scaffold materials was determined by scanning electron microscopy (SEM), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC).

Tissue reaction to polypyrrole-coated polyester fabrics: an in vivo study in rats.

Electrically conductive polypyrrole is very attractive for tissue engineering because of its potential to modulate cellular activities through electrical stimulation. However, its in vivo behaviors have not been fully studied. This paper investigates the in vivo biocompatibility and biostability of PPy-coated polyester fabrics.

Hemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: a review.

In 1984, low-density polyethylene (LDPE) and polymethylsiloxane (PDMS), two primary reference materials (PRM), were made available by the National Heart, Lung, and Blood Institute (NHLBI) as discriminatory tools for the validation of standardized and novel in vitro and in vivo tests in the evaluation of biomaterials. This article reviews the results and conclusions obtained by several studies investigating the hemocompatibility, in vitro biocompatibility, inflammatory response, and in vivo tissue reactions of these two reference materials. Variable results obtained with LDPE and PDMS in ex vivo hemocompatibility studies were attributed to the type of animal model used, the flow velocity of the circulating blood, the time of exposure, and the methodology used to measure blood cell adhesion or activation at the surface of the materials.

Selection of a polyurethane membrane for the manufacture of ventricles for a totally implantable artificial heart: blood compatibility and biocompatibility studies.

Membranes made from 4 commercial poly(carbonate urethanes): Carbothane (CB), Chronoflex (CF), Corethane 80A (CT80), and Corethane 55D (CT55), and from 2 poly(ether urethanes): Tecoflex (TF) and Tecothane (TT) were prepared by solution casting and sterilized by either ethylene oxide (EO) or gamma radiation. Their biocompatibility was evaluated in vitro in terms of proliferation, cell viability, and adhesion characteristics of human umbilical veins (HUVEC), monocytes (THP-1), and skin fibroblasts, and by measuring complement activation through the generation of the C3a complex. Their hemocompatibility was determined by measuring the level of radiolabeled platelet, neutrophil, and fibrin adhesion in an ex vivo arteriovenous circuit study in piglets as well as via an in vitro hemolysis test.

Analysis of retrieved polymer fiber based replacements for the ACL.

The present retrospective analysis of 117 surgically excised anterior cruciate ligament (ACL) prostheses was designed to elucidate the etiology and mechanisms of failure of synthetic ligamentous prostheses. They were harvested from young and active patients (26 +/- 7 yrs) at various orthopaedic centers in France between 1983 and 1993. The average duration of implantation of augmentation and replacement prostheses were 21.

In vivo magnetic resonance imaging and relaxometry study of a porous hydrogel implanted in the trapezius muscle of rabbits.

In vivo magnetic resonance imaging (MRI) and relaxometry were performed to assess noninvasively the tissue reaction and the biological integration of hydrogels made of poly[N-(2-hydroxypropyl) methacrylamide] (PHPMA) after implantation in the trapezius muscle of rabbits. The benefits of incorporating RGD peptide sequences in the polymer backbone were also investigated. The histological status of each implant was probed by the trend of their transversal relaxation times, T(2), while their biocompatibility was evaluated by analyzing the host tissue response through the evolution of the relaxation times of the adjacent muscle tissue.

Biostability, inflammatory response, and healing characteristics of a fluoropassivated polyester-knit mesh in the repair of experimental abdominal hernias.

The present study was undertaken to validate the benefits of a fluoropolymer treatment on the biostability, inflammatory response, and healing characteristics of a polyester mesh used for hernia repair, the Fluoromesh, as compared to a commercial monofilament-knit polypropylene mesh, Marlex, used as the control. Both were implanted for the repair of surgically induced abdominal hernias in piglets for prescheduled durations of implantation of 4, 15, and 60 days. The mesh and surrounding tissue were harvested at the sacrifice for the bursting strength and inflammatory response measurements in terms of alkaline and acid phosphatase secretion in the tissue, and for histological observations of the healing sequence and tissue thickness measurements by histomorphometric techniques.

Characterization of plasma proteins adsorbed onto biomaterials. By MALDI-TOFMS.

The analysis of plasma proteins adsorbed onto a polyurethane (PU) biomaterial was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). This article marks the first study on MALDI-TOFMS analysis of multiple proteins adsorbed from plasma, in vitro, onto the surface of a biomaterial to easily enable their characterization. Plasma standards from three different hosts were placed in contact with non-porous PU, a model biomaterial.

First-generation aortic endografts: analysis of explanted Stentor devices from the EUROSTAR Registry.

Purpose: To examine the structure and healing characteristics of chronically implanted Stentor endografts that were explanted due to migration, endoleak, thrombosis, or aneurysm expansion.

Methods: The devices were harvested following reoperation (n = 5) or autopsy (n = 1) with implantation times ranging from 13 to 53 months. Structural modifications to the metal components were examined using radiography, endoscopy, and magnetic resonance imaging (MRI).

Mechanical characteristics of the canine thoracic duct: what are the driving forces of the lymph flow?

This study is designed to better understand the mode of lymph transport, particularly through the extrinsic pumping by external compression of the lymph vessel. The pressure-diameter relationship of lymphatic segments isolated from the canine thoracic duct was examined using a laser optical micrometer measurement system. Results revealed that the thoracic duct displayed a high extensibility or compliance in the physiological pressure range, yet became progressively less so with increasing internal pressure.

Endovascular repair of thoracic aortic aneurysm in dogs: evaluation of a nitinol-polyester self-expanding stent-graft.

Purpose: To validate the ease of deployment and in vivo healing performance of a nitinol-polyester self-expanding stent-graft using a canine thoracic aortic aneurysm model.

Methods: Arterial aneurysms were surgically created in 8 dogs by sewing a polyester patch onto the anterior side of the thoracic aorta. The nitinol-polyester self-expandable stent-grafts (Cragg EndoPro System 1) were implanted transluminally via the femoral route and deployed at the site of the thoracic aneurysm.

Mechanism and rate of degradation of polyhydroxyoctanoate films in aqueous media: A long-term in vitro study.

The present study investigated the in vitro mechanism and degradation rate of polyhydroxyoctanoate (PHO). Solution-cast PHO films were incubated in either water or isoosmotic phosphate-buffered saline (PBS) for periods ranging from 1 to 24 months. Physical characterization included weight loss, water absorption, pH change, tensile strength, and scanning electron microscopy (SEM) studies.

Tissue reactions to polypyrrole-coated polyesters: A magnetic resonance relaxometry study.

The electrically conductive properties of polypyrrole (PPy) as a coating on polyester material are very attractive for the manufacture of small diameter blood conduits. However, before these PPy-coated materials can be investigated for their capacity to generate endothelialized luminal surfaces, they must first be studied for their innocuousness in a living environment. The specific goal of the present study was to investigate the in vivo interactions of PPy-coated and noncoated woven polyester materials implanted subcutaneously in rats for prescheduled periods of 2, 5, 10, 20, and 30 days.

In vivo biocompatibility and degradation studies of polyhydroxyoctanoate in the rat: a new sealant for the polyester arterial prosthesis.

The present study examined the biocompatibility and degradation properties of poly (beta-hydroxy octanoate) (PHO) as an impregnation substrate on arterial prostheses. PHO-impregnated polyester grafts sterilized by ethylene oxide (EO) or gamma (gamma) radiation, and polyester Dacron(R) prostheses impregnated with fluoropolymer, gelatin, or albumin were implanted subcutaneously in rats for periods ranging from 2 to 180 days. The biocompatibility was assessed by quantifying the alkaline and acid phosphatase secretion while performing histological studies at the tissue/prosthesis interface.

Endothelial cell behavior on vascular prosthetic grafts: effect of polymer chemistry, surface structure, and surface treatment.

When implanting any vascular prosthetic grafts, one important goal to ensure long-term patency is achieving complete endothelialization of the luminal surface, a process that has rarely been observed clinically in humans. Seeding vascular grafts with endothelial cells has been seen as an attractive approach but has not been clinically convincing. A determining factor may be the type of polymer and surface structure.

In vivo time course studies of the tissue responses to resorbable polylactic acid implants by means of MRI.

Magnetic resonance (MR) imaging and relaxation time measurements of bioresorbable implants made of polylactic acid (PLA), as well as the surrounding tissues, were carried out over a period of 6 months to monitor the implant state and the body's responses, and to determine how these processes are reflected in MR data. Twelve rabbits each received two subcutaneous PLA implants (45 x 10 x 2 mm). Changes in tissue relaxation rates demonstrated inflammation and tissue healing time courses but were not simply linear functions of the tissue water content and so provide new insight into MR characterization of inflammatory processes.

Hydrolytic and enzymatic incubation of polyhydroxyoctanoate (PHO): a short-term in vitro study of a degradable bacterial polyester.

The present study examined the degradation behaviour of poly(beta-hydroxy octanoate) (PHO), a bacterial poly(beta-hydroxy alkanoate), following incubation under hydrolytic or enzymatic conditions in vitro. Solution-cast PHO films were incubated in a citrate buffer solution with and without acid phosphatase and in an acetate buffer with and without beta-glucuronidase for periods ranging from 7 to 60 days. The physical characterization of the PHO films was analyzed by SEM and tensile strength studies.

Effect of sterilization on the physical and structural characteristics of polyhydroxyoctanoate (PHO).

The present study examined the potential applicability of poly(beta-hydroxy octanoate) (PHO), a bacterial polyester, as a candidate for biomaterial applications, by investigating the effect of sterilization on the physical and structural characteristics of PHO. PHO-cast films were sterilized by either ethylene oxide (EO) gas at 38 degrees C or gamma radiation (2.5 Mrad) in air at room temperature.

Comparison of healing in fresh and preserved arterial allografts in the dog.

The use of aortic allografts for the management of vascular prosthetic infections has recently been reintroduced. Impressive results have been obtained; however, the possibility of late degeneration remains a major concern. The healing behavior of aortic allografts, either fresh or preserved, in antibiotic-supplemented nutrient medium at 4 degrees C for 1 week and used as thoracic aorta substitutes in dogs was investigated after 6 months of implantation.

Theoretical prediction of the hemodynamic performance of slow resorbing polyester protein impregnated arterial prostheses after implantation: a plea for fast resorption of the coating.

The clinical literature cites cases where slow, incomplete, or nonuniform protein resorption from protein impregnated arterial prostheses produces undesirable localized internal capsule proliferation leading to a significant reduction of the internal diameter of the prosthesis. In an attempt to describe the hemodynamic response to this phenomenon, the blood flow in such stenotic regions was simulated and characterized numerically using FIDAP computational fluid dynamics software to determine the Navier-Stokes and continuity equations for simple channel flow. To simulate various stages of internal capsule development, numeric computations were made in an idealized tubular expansion at stenosis ratios ranging from 0.

Fluid filtration across the arterial wall under flow conditions: is wall shear rate another factor affecting filtration rate?

The effect of flow on fluid filtration across an arterial wall was investigated in the canine common carotid artery. The arteries were cannulated in situ to maintain their in vivo length and endothelium intact. The excised vessels were pressurized at 120 mmHg through an overflow head-tank system that provided a constant flow rate to the perfused vessels.

Experimental modifications to a canine infrarenal aortic aneurysm model for the validation of endovascular stent-grafts: an exploratory study.

The intraluminal elastase perfusion model has been proven to be potentially effective in producing abdominal aortic aneurysms (AAA) in rodents, yet has produced unpredictable results in larger animals. The purpose of this study was to explore different variations to an existing elastase perfusion model in the dog in the hopes of producing a consistent AAA for endovascular graft validation. The elastase perfusion canine model was modified as follows: (1) inflation of a balloon catheter in the infrarenal aorta (IA) of 3 dogs following elastase perfusion with doses of 2800 U for 40 min; (2) perfusion of the IA of 5 dogs with various elastase doses ranging from 2800 U to 8400 U for 2 h; and (3) perfusion of the IA of 2 dogs with elastase and collagenase for 2 h.