The effect of treating the surface of a polyester vascular prosthesis with a novel fluoropolymer before sealing the graft with gelatin has been evaluated in a canine thoracoabdominal bypass model. The healing behavior of the Fluoropassiv graft was compared with that of the Gelsoft ERS prosthesis used as control for prescheduled periods of implantation ranging from 4 hr to 6 months. Both series of explanted grafts were analyzed using macroscopic, histologic, and scanning electron microscopic observations, and by determining the prostacyclin/thromboxane A2 ratio (PGI2/TXA2) and the thrombogenicity of the luminal surface by means of labelled platelets and fibrin deposition. Chemical analysis of explanted and cleaned graft segments was performed using electron spectroscopy for chemical analysis, differential scanning calorimetry, and contact angle methods. No difference in platelet and fibrin deposition or PGI2/TXA2 secretion by the luminal surface was observed between the treated and the control grafts at any implantation period. On the other hand, pathologic investigation has revealed that, although there is no difference between the two grafts during the first month, the healing sequence of the Fluoropassiv graft appeared more complete and mature than the control graft after 3 and 6 months. Differences were observed in the extent of collagenous internal capsular development, endothelialization, and tissue penetration into the knitted structure. The presence of fluorine and a higher contact angle at the surface of all the explanted fluoropassivated grafts is believed to have been responsible for reducing the inflammatory response and enhancing the long-term healing behavior of this novel prototype device over the control gelatin sealed prosthesis.

Animals↗

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↗

PubMedDate not supplied

A capillary method to measure water transmission through polyurethane membranes.

A capillary method has been developed to measure the rate of water transmission through polyurethane membranes prepared for use as ventricles in artificial hearts. The system consisted primarily of a leak-proof sample chamber containing the water, a glass capillary flow meter, and a receiver compartment with continuous dry air ventilation. The capillary flow meter monitored the volume of water loss in the sample chamber. The rate of water transmission through the test membrane was found to be proportional to the water loss in the sample chamber, and dependent on the membrane thickness. For thicknesses from 0.09 mm to 0.34 mm, water vapor transmission rates ranged from 7.53 x 10(-8) to 2.76 x 10(-8) mol/s cm2, respectively. Although the concentration of water vapor in the receiver compartment did affect the rate of water vapor transmission through the membrane, within the pressure range 50-200 mmHg, there was very little effect. These findings suggest that water transmission through a polyurethane membrane is dominated by a diffusion process rather than by bulk convection.

Biocompatible Materials↗

PubMedDate not supplied

Comparison of the in vivo behavior of polyvinylidene fluoride and polypropylene sutures used in vascular surgery.

To find a nonabsorbable suture material that is equivalent to polypropylene in ease of handling and tensile properties, and that has low thrombogenicity and tissue reactivity but improved biostability, some researchers and clinicians see merit in considering the suitability of monofilaments made from polyvinylidene fluoride. The current animal study investigated the relative biocompatibility and biostability of these two suture materials by using them to anastomose a polyester arterial prosthesis in a canine thoracoabdominal bypass model for 10 periods of implantation ranging from 4 hr to 2 years. Biocompatibility was assessed with light and scanning electron microscope examinations of the explanted sutures, and biostability of the cleaned sutures was determined by Fourier transform infrared spectroscopy and scanning electron microscope analysis. The polyvinylidene fluoride and polypropylene sutures were found to have similar handling and healing characteristics. During the first months in vivo, both types of suture experienced a temporary increase in carbonyl group absorption that coincided with the duration of the inflammatory response. After 1 and 2 years in vivo, the explanted polypropylene sutures showed visual evidence of surface stress cracking. This was not found with the explanted polyvinylidene fluoride sutures. These results suggest that polyvinylidene fluoride may be more biostable than polypropylene in the long term.

Animals↗

PubMedDate not supplied

Use of supercritical fluid extraction as a method of cleaning anterior cruciate ligament prostheses: in vitro and in vivo validation.

The process of supercritical fluid extraction (SFE) using carbon dioxide as the mobile phase is finding increasing numbers of applications in a wide variety of industries for the extraction, separation, and cleaning of materials. This study assessed the usefulness of this approach in removing surface contaminants from a knitted polyester anterior cruciate ligament (ACL) prosthesis before packaging and sterilizing the product during manufacture. The physical, dimensional, and chemical properties of SFE treated compared with commercially scoured control samples were characterized using a number of textile test methods: electron spectroscopy for chemical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, and solvent extraction analysis. The biocompatibility of the samples was measured in terms of their ability to generate CD18 integrin expression on activated human polymorphonuclear cells, and their inflammatory response when implanted for up to 30 days in the knee joint of rats. SFE treatment was successful in removing most of the nonpolar contaminants from the ACL prosthesis and reducing the amount of residuals to a commercially acceptable level. However, some nitrogen containing compounds and polar salts were not removed by the SFE process. The results from the biocompatibility tests demonstrated that the cleaner SFE treated prosthesis induced significantly lower CD18 expression than the scoured control fabric, and was also associated with a milder inflammatory response and a more rapid rate of healing during the 30 day animal trial. Another effect of SFE processing was to cause the polyester device to shrink and lose porosity because of yarn contraction and modification of the polymer's microcrystalline structure.

Animals↗

PubMedDate not supplied

[Comparative study of some ions of the bacterial plaque and saliva].

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Dental Plaque↗