Biomedical subjects

P Ukpabi

Publications and source records attributed to P Ukpabi.

5 recordsLinked to original sources

PubMed1995

Evaluating the Dialine vascular prosthesis knitted from an alternative source of polyester yarns.

The sudden and unilateral decision by E. I. DuPont de Nemours & Co., Inc., to withdraw its polymers for use in implantable devices has presented the medical device industry with an immediate and serious challenge to find alternative sources of biomaterials. In France, the company Cardial S.A. has already taken steps to find an alternative polyester yarn to replace Dacron by developing a new arterial prosthesis knitted from polyester yarns supplied by Rhône-Poulenc Fibres. This article describes an in vitro and in vivo study of this French device, called the Dialine prosthesis, with a view to determining its relative performance compared to current American and British prostheses, which rely on DuPont's Dacron yarn. In addition to analyses of the morphology and textile structure, and measurements of its physical and chemical properties, the Dialine graft was implanted as a thoracoabdominal bypass in dogs for periods ranging from 4 h to 6 months. In addition to our pathologic and histologic observations, we cleaned and evaluated the explanted prostheses for in vivo changes in dimensions, strength, and crystalline microstructure. The Dialine graft was found to differ structurally from other polyester prostheses because it is warp-knitted from a mixture of flat and texturized yarns with finer filaments. Its denser structure has a lower water permeability, greater flexibility and ease of handling, satisfactory strength, and dimensional stability, and it presents different textures on its luminal and external surfaces. The in vivo trial demonstrated that it has excellent biocompatibility and biostability over 6 months. With no thrombi observed on the luminal surface after 3 months, it has a faster rate of healing, generates compact external and internal capsules with a thinner neointima, and has an overall milder inflammatory response than is normally observed with Dacron-based prostheses.

Angiography↗

PubMed1995

The gelweave polyester arterial prosthesis.

OBJECTIVE: To determine the effect of the gelatin coating on the efficacy of Gelweave, a new gelatin-sealed woven polyester graft material, as an arterial prosthesis. DESIGN: In-vitro and in-vivo studies of the prosthesis. SETTING: A laboratory of experimental surgery in a university teaching institution. SUBJECTS: After in-vitro testing of the material, eight dogs were subjected to a series of in-vivo tests to evaluate the properties of Gelweave in comparison with its unsealed precursor and a commerically available collagen-coated woven polyester prosthesis. INTERVENTION: Implantation of the prosthesis as a thoracoabdominal bypass for prescheduled periods ranging from 4 hours to 6 months. MAIN OUTCOME MEASURES: Physical and chemical properties of the virgin prosthesis compared with the other two prostheses, effects of the gelatin-sealed prosthesis on healing, the hematologic characteristics of the dogs before operation and at sacrifice, microscopic studies, fibrin and platelet uptakes, prostaglandin secretion, and properties of the Gelweave grafts removed at varying periods after implantation. RESULTS: The gelatin sealant in the Gelweave prosthesis effectively reduced the water permeability of the new prototype to zero. Neither blood loss at implantation nor infection during the postimplantation period was observed. The gelatin impregnation did not cause any adverse response in the dogs and was completely lysed within 2 weeks, thus allowing encapsulation and graft healing to progress satisfactorily. After 2 weeks, the prostacyclin:thromboxane ratio was greater than 1.0, whereas the fibrin and platelet uptakes on the luminal surface of the Gelweave grafts remained low, regardless of the period of implantation. Analysis of the explanted grafts confirmed that this gelatin-sealed prototype prosthesis healed satisfactorily and no adverse biologic response occurred as a result of the gelatin coating. It maintained its biostability during 6 months in situ. CONCLUSION: The new Gelweave arterial prosthesis is ready for clinical use as a thoracic and abdominal vascular substitute.

Animals↗

PubMed1994

Morphological, physical and chemical evaluation of the Vascugraft arterial prosthesis: comparison of a novel polyurethane device with other microporous structures.

In this study the morphology, physical properties, surface chemical characteristics and microstructure of the Vascugraft arterial prosthesis have been investigated. This is a novel microporous polyurethane device, recently developed by the company Braun-Melsungen AG in Germany for use as a small calibre arterial substitute. This comparative study included two other synthetic grafts: the Mitrathane prosthesis, a hydrophilic prototype polyetherurethane urea graft with closed internal pores, and the commercially successful expanded polytetrafluoroethylene reinforced Goretex prosthesis with an open microporous structure. The Vascugraft prosthesis contains a network of fused microfibres of varying thickness and orientation which provide open and communicating pores similar in size to those in the Goretex material. In addition, they extend from one side of the graft wall to the other. As well as having superior longitudinal and radial compliance to the reinforced Goretex device, the Vascugraft prosthesis has more than adequate bursting and suture retention strengths. Through the use of contact angle measurements, electron spectroscopy for chemical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry and molecular weight analysis by size exclusion chromatography, the surface of the Vascugraft prosthesis has been shown to be uniquely hydrophobic, as well as containing carbonate groups within an aliphatic polyesterurethane polymer. In addition, variations in micro-phase separation structure of hard and soft segment domains between different sizes and batches of product are marginal. Because of the interesting physical and chemical properties, it is recommended that in vitro biocompatibility and biostability studies be undertaken prior to using the prosthesis in animal or clinical trials.

Animals↗

PubMed1994

Quantitative analysis of the surface morphology and textile structure of the polyurethane Vascugraft arterial prosthesis using image and statistical analyses.

The surface morphology and textile structure of the Vascugraft polyurethane arterial prosthesis were investigated. Novel methods of image analysis and the presentation of statistical data were used to obtain quantitative results of the surface morphology of the non-woven microfibrous structure of prostheses of three different sizes. These techniques have identified apparent differences in the distributions of thickness and orientation of the microfibres between the internal and external surfaces and between the three prostheses investigated.

Biocompatible Materials↗

PubMedDate not supplied

Polyester arterial prostheses. Recent developments from the Czech Republic and Poland.

To evaluate recent developments in the design and production of polyester vascular prostheses in eastern Europe, a series of in vitro physical and chemical tests and an in vivo study was performed on three new prototype devices from the Czech Republic and one from Poland. The in vitro results for these four prostheses, referred to as the Ra-1n (warp knitted, uncrimped), Ra-1v (warp knitted, crimped), Mikrofroté (weft knitted, uncrimped), and Dallon (warp knitted, crimped) prostheses, were compared against values for three commercial devices of western origin, namely the Triaxial, the Vasculour II, and the Cooley II grafts. The animal trial involved implanting the four prototype devices as a thoracoabdominal bypass in dogs for eight different periods ranging from 4 hrs to 6 months and undertaking histologic and structural investigations on the retrieved grafts. Because of its poor long-term dimensional stability in vivo, the continued use of a weft knitted structure, like the Mikrofroté prosthesis, is to be deprecated. Conversely, the introduction of a more dimensionally stable warp knitted structure in three prototypes is to be acknowledged. However, the presence of surface contaminants was most likely responsible for the excessive inflammatory reaction generated by all four prostheses during the first month in vivo, which resulted in delayed healing performance. In addition, an unusually high surface carbon-oxygen ratio suggests that the crimping process needs further refinement. Improved cleaning and packaging procedures are essential before these products can complete against existing commercial prostheses of western origin. In conclusion, these new developments illustrate that the technology of warp knitting, which is now spreading worldwide, should be evaluated.

Animals↗