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Biomedical subjects

M F Sigot-Luizard

Publications and source records attributed to M F Sigot-Luizard.

34 records · Page 2Linked to original sources
PubMed1986

Degradability of crosslinked albumin as an arterial polyester prosthesis coating in in vitro and in vivo rat studies.

In order to avoid the preclotting procedure in knitted polyester arterial prostheses and in woven models, compound polyester grafts have been proposed, containing preadsorbed collagen or albumin. Since we are currently investigating grafts impregnated with crosslinked albumin, it was decided to establish the degradation rate of this coating after stabilization with either glutaraldehyde (GA) or carbodiimide (CDI). Tests were performed in vitro by incubation in either PBS, plasma or pancreatin and in vivo by implantation in the abdominal cavity of rats. In PBS or plasma in vitro, the coatings were very stable (2% degradation after 144 h incubation), however, in pancreatin the CDI crosslinked albumin degraded much faster than the GA crosslinked albumin (more than 50% degradation in 12 h compared to less than 30% in 48 h). In vivo the degradation rates of the two types of crosslinked albumin were similar (almost all of the albumin having been lost after 4 weeks) but the cellular response was very different: a mild tissue reaction was observed with the CDI crosslinked coating whereas many foreign body giant cells were present on the GA crosslinked material.

Albumins↗
PubMed1986

Chemically fixed human umbilical cord vein grafts as arterial substitutes: potential and limits.

In spite of reported successes, synthetic fabric grafts and microporous and plain synthetic conduits have proven unsuitable for aorto-coronary bypasses and showed weaknesses below the knee. Readily available and uniform diameter vascular substitutes with biological and mechanical properties comparable to human vessels would be of paramount interest. Following reported successes with chemically fixed human umbilical veins (HUV), we have attempted to develop smaller diameter blood conduits and have improved the currently prevalent techniques of fixation, preparation and storage to generate more convenient surgical products. In vitro assessment of the processed HUV demonstrated that the HUV can be easily processed to make an arterial substitute that can be preserved either in a liquid medium or as a dry product. However, the in vivo implantations in dogs led to disappointing results for liquid-preserved or albuminated veins. Critical-point dried grafts gave better results, unfortunately they do not heal and they can only degrade after implantation.

Animals↗
PubMed1984

Cytocompatibility of albuminated polyester fabrics.

An alternative to the usual technique of preclotting porous textile vascular prostheses prior to surgical implantation is to render them impermeable to blood by impregnation with a cross-linked albumin filler matrix. This material subsequently becomes the foundation for cellular development. The compatibility of such impregnated fabrics with newly formed endothelial cells has been evaluated by an in vitro organotypic culture method. This technique enables the characterization and numeration of cells that develop on blood contact surfaces and enables determination of their rate of development. Woven, knitted, and velour fabrics were evaluated following coating with albumin and either storage in Tyrode solution or 40% ethanol or desiccation by critical point drying. Preclotted cardiovascular repair fabrics prepared according to conventional surgical protocol served as controls. The identification of the newly formed cells was confirmed histologically. The most extensive and rapid cellular development was observed on the woven fabric and is believed may have resulted from the smoother surface topography of this substrate. Good cellular development was noted particularly on fabrics which had been stored in Tyrode solution. Ethanol had a deleterious effect on the apparent compatibility.

Albumins↗
PubMed1983

Polyester prostheses as substitutes in the thoracic aorta of dogs. I. Evaluation of commercial prostheses.

Using canine models, a representative selection of polyester or Dacron vascular prostheses, including woven, knitted, and velour types, were evaluated for their relative healing characteristics and for their structural changes during implantation. Following residence periods ranging from 4 h to 6 months at the site of the thoracic aorta, the dogs were sacraficed, and the grafts were excized for measurement of the thrombogenicity of the flow surface and for pathological examination by light microscopy and SEM. The kidneys were also removed and examined for infarcts caused by any trapped circulating emboli. The extent of healing, the presence of embolizing nuclei, and the thrombogenicity and morphology of the lumen surface were also assessed. The healing characteristics of each type of device proved similar. Velour fabrics exhibited more extensive encapsulation, but frequently their internal capsules failed to incorporate all the fibers. In all cases, cellular development on the lumen was limited to areas contiguous to the anastomoses. The initial porosity of the devices as measured by water permeability did not appear to influence the healing sequence to a significant extent. The grafts did exhibit differences in structural stability depending on whether they were of a knitted or woven construction. We suggest that users consider these different mechanical and structural properties when making their choice of a graft. Despite these differences, we believe that the healing process is far more host dependent than graft dependent.

Angiography↗
PubMed1981

[Liquid storage media for vascular prosthesis of biological origins : their impact on biocompatibility (author's transl)].

Unlike synthetic arterial substitutes which are supplied as presterilized, dry-packaged products with potentially indefinite shelf lives, arterial prosthesis of modified biological origin must stored in less convenient liquid preservative media. These preservatives can affect the post-implantation performance and the biocompatibility of the devices. In order to identify the most suitable media, a modified "in vitro" cell culture test method was developed. It makes use of endothelial cells prepared from the aorta of chick embryo. In general, the prosthesis stored in liquid media had a disappointing performance from the point of view of neo-endothelium development and adhesion. Residual cytotoxicity was also noted for most of these currently used prosthesis storage and pre-surgical preparation protocols. Although devices stored in physiologic media showed adequate biocompatibility according to this cell culture test, it appears that neo endothelialization does not proceed concurrently with healing. Cellular development where present, adheres poorly to the substrate and cannot resist the shear forces of normal blood flow. Pre-implantation treatment of such prosthesis with cellular growth-promoting substances may enhance cell-prosthesis adhesion.

Animals↗
PubMedDate not supplied

Polyester prostheses as substitutes in the thoracic aorta of dogs. II. Evaluation of albuminated polyester grafts stored in ethanol.

In an attempt to find an alternative procedure to the preclotting of porous textile vascular prostheses, the feasibility of an albumin coating and ethanol preservation technique has been evaluated by implanting albuminated polyester prostheses as substitutes in the thoracic aorta of dogs. Nine different grafts representing woven, knitted, and velour constructions were implanted for periods ranging from 4 h to 6 months. At the sacrifice, the grafts were excized for measurement of the thrombogenicity of the flow surface, for pathological examination by light microscopy and SEM, and for quantifying the changes in the textile structure during implantation. Also the kidneys were removed and examined for infarcts caused by trapped circulating emboli. The healing characteristics of the nine different grafts proved similar and followed the same sequence of events as preclotted control grafts. The albumin coating and ethanol preservation resulted in a somewhat slower rate of healing. Yet, given sufficient time, a more completely healed graft was achieved as evidenced by the presence of endothelial-like cells throughout the length of the graft. In addition, the albumin is believed to reinforce the textile structure by reducing the tendency to stretch and dilate in vivo.

Albumins↗
PubMedDate not supplied

Use of myxalin for improving vascular graft healing: evaluation of biocompatibility in rats.

Myxalin is a glycopeptide extracted recently from a gram-negative bacterium. It has blood anticoagulant properties and can enhance endothelial cell growth. With the ultimate objective of using this bioactive molecule to promote vascular graft healing, this study assessed its biocompatibility in vivo by comparing the cellular and immunological responses of gelatin-coated knitted polyester grafts with and without myxalin following implantation in the peritoneal cavity of rats for prescheduled periods of 3 days and 1, 2, and 4 weeks. A nongelatin-coated virgin polyester graft was included as the reference material. The biological response to gelatin alone was characterized by a slower rate of cellular infiltration into the implant, reduced collagen synthesis, and higher levels of acid phosphatase and esterase activity in the surrounding tissue. The addition of myxalin to this coating resulted in a significant reduction of hydrolase secretion in the tissue surrounding the implant and an enhancement of cellular ingrowth.

Acid Phosphatase↗
PubMedDate not supplied

A novel microporous polyurethane blood conduit: biocompatibility assessment of the UTA arterial prosthesis by an organo-typic culture technique.

An organotypic culture assay has been used to assess the biocompatibility and cytotoxicity of an arterial prosthesis developed at the University of Texas-Arlington (the UTA graft) from a structurally modified polyurethane (PU) elastomer (Tecoflex). The cell culture test was applied to the UTA graft after sterilization by ethylene oxide and by gamma radiation in two separate series. First, small specimens of the prosthesis were incubated for 7 days on a semisolid nutrient medium with their luminal surface in direct contact with endothelium explanted from the aorta of chick embryos. Second, the possibility of cytotoxic contaminants being leached from the polyurethane was assessed by immersing the biomaterial in the liquid culture medium for 5 days at 37 degrees C prior to conducting the organo-typic culture assay on a standard control surface. The structure of the UTA polyurethane prosthesis is porous, but the graft wall is impervious because it contains closed (i.e., noncommunicating) pores. In addition, four other vascular prostheses were included in the study for comparison. They were the Hydrophilic Mitrathane PU graft with a similar impervious, closed pore structure, an experimental Hydrophobic Mitrathane PU graft with a fibrous, open pore structure, and the commercial Impra and Reinforced Goretex expanded PTFE grafts. Following 7 days of cell culture, the biocompatibility and cytotoxicity of the various biomaterials were measured in terms of the area of migrating cells, the density of cells surrounding the explants, and the level of cell adhesion. Comparison of the results against control cultures demonstrated that the UTA graft, along with the other four prostheses, does not release cytotoxic extractables. Microscopic observations of its cultured surface indicated that the UTA graft promotes a high density of cell growth over a limited area, similar to the Hydrophilic Mitrathane graft. This level of biocompatibility is considered inferior to that of the two PTFE and the Hydrophobic Mitrathane prostheses, which promote more extensive cell migration, greater cell adhesion, and cell growth in a continuous single layer.

Animals↗
PubMedDate not supplied

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. Using organotypic culture assays, the present investigation studied the effect of different polymers, surface structures, and surface treatments on endothelial cell behavior. The materials tested were polyester (PET), polytetrafluoroethylene (PTFE), polyesterurethane (PESU), and polyetherurethane (PETU) grafts with different surface structures. The surface treatments on the PET grafts included impregnation with cross-linked albumin, collagen, and gelatin, and treatments with fluoropolymer and electrically conducting polypyrrole polymer. Low density polyethylene (LDPE) and polydimethylsiloxane (PDMS) sheets (smooth surface, plain wall) were used as controls. After incubation for 7 days at 37 degrees C, cell adhesion and migration on the different polymers and structures were as follows: woven and knitted PET (high porosity) > PTFE, PESU, PETU hydrophobic (low porosity) > PETU hydrophilic, LDPE, PDMS (no porosity). Cell density results showed no difference between polymers and porous structures and a higher cell density on smooth nonporous surfaces. Compared with the nonimpregnated PET structures, knitted PET treated with albumin, collagen, or gelatin showed slight decreases of cell adhesion. No differences in cell migration and density were reported between any of the PET grafts, except for one polyester graft with a different chemistry than Dacron, which exhibited greater cell migration and lower cell density. Polyester grafts with a fluoropolymer treatment showed lower cell adhesion and migration and higher cell density than the nontreated PET. Finally, the woven PET grafts treated with electrically conducting polypyrrole exhibited contrasting cell behavior depending on the conductivity involved.

Blood Vessel Prosthesis↗