Browsing by Author "Williams, DF"

Now showing 1 - 2 of 2
  • Item
    Influence of steam sterilization induced surface changes of polyester materials on its biocompatibility
    (BULLETIN OF MATERIALS SCIENCE, 1997) Nair, PD; Doherty, PJ; Williams, DF
    Steam sterilization is conventionally used for the sterilization of materials used in surgery and medicine. When subjected to repeated steam sterilization, oligomers of polyethylene terephthalate are produced on the surface of the polyester materials. The consequences of the production of such oligomers on the biocompatibility of the polyester material have been investigated. Growth inhibition of L929 fibroblast cells has been observed on the repeatedly sterilized materials in the in vitro cell-material contact studies. In vivo implantation of the repeatedly sterilized materials elicited a hostile tissue response comprising enhanced macrophage activity, which could have an adverse effect on the long term stability of the polyester materials.
  • Item
    Influence of wall shear rate on parameters of blood compatibility of intravascular catheters
    (BIOMATERIALS, 1996) Rhodes, NP; Kumary, TV; Williams, DF
    Three polymeric materials (silicone, PVC and nylon) were compared in an in vitro perfusion model, whereby 5 ml whole blood were perfused along 1 m lengths of polymeric tubing of 1 mm internal diameter at wall shear rates of up to 1000 s(-1). Perfusion took place at 37 degrees C for 30 min. The polymers were investigated for platelet activation, granulocyte secretion, complement activation and contact phase activation. These parameters were also analysed in static contact for comparison. All the parameters measured displayed a dependence on wall shear rate. In all the materials studied, platelet adhesion and platelet activation increased with increasing flow rate. Granulocyte elastase release increased slightly with increasing flow rate up to 300 s(-1). Complement activation was greatest for PVC at 1000 s(-1), greatest for nylon at 100 s(-1), but there was no measurable difference at either rate for silicone. All samples caused an increase in clotting time with increasing wall shear rate. PVC was the most platelet compatible material, nylon the worst. Silicone caused least contact phase activation, PVC and nylon the most. (C) 1996 Elsevier Science Limited.