Development, preclinical evaluation and validation of a novel quick vascular closure device for transluminal, cardiac and radiological arterial catheterization.

Following percutaneous coronary intervention, vascular closure devices (VCDs) are increasingly used to reduce time to ambulation, enhance patient comfort, and reduce potential complications compared with traditional manual compression. Newer techniques include complicated, more or less automated suture devices, local application of pads or the use of metal clips and staples. These techniques often have the disadvantage of being time consuming, expensive or not efficient enough. The VCD failure rate in association with vascular complications of 2.0-9.5%, depending on the type of VCD, is still not acceptable. Therefore, the aim of this study is to develop a self-expanding quick vascular closure device (QVCD) made from a bioabsorbable elastic polymer that can be easily applied through the placed introducer sheath. Bioabsorbable block-co-polymers were synthesized and the chemical and mechanical degradation were determined by in vitro tests. The best fitting polymer was selected for further investigation and for microinjection moulding. After comprehensive haemocompatibility analyses in vitro, QVCDs were implanted in arterial vessels following arteriotomy for different time points in sheep to investigate the healing process. The in vivo tests proved that the new QVCD can be safely placed in the arteriotomy hole through the existing sheath instantly sealing the vessel. The degradation time of 14 days found in vitro was sufficient for vessel healing. After 4 weeks, the remaining QVCD material was covered by neointima. Overall, our experiments showed the safety and feasibility of applying this novel QVCD through an existing arterial sheath and hence encourage future work with larger calibers.

Protection of islets of Langerhans from interleukin-1 toxicity by artificial membranes.

Recently it has been reported that interleukin 1 may play a central role in the immune destruction of islets. Since the mass weight of interleukin-1 is close to that of insulin, destruction of transplanted islets may be possible although they are enclosed in membranes that prevent penetration by immune-competent cells and cyto-toxic antibodies. The present in vitro study showed that the encapsulated rat islets are protected from high doses of IL-1 (1000 ng) inside a hollow fiber membrane with a cutoff of 50,000 D. The function of islets in a free-floating culture, however, was suppressed in a dose-dependent manner (1000 ng/L; 20-30% of controls). Histologically, no damage of the free-floating or encapsulated islets was observed at 1000 ng of IL-1-containing medium. Islets washed out of the devices after 2 days of exposure to IL-1 showed no difference in glucose-stimulated insulin release when compared with islets not exposed that were kept in free-floating culture. It is suggested that an unspecific coating of the membranes by serum proteins (containing physiological IL-1 antagonists) may cause the protective effect.

Experiments on a new hollow fiber membrane for immuno isolated transplantation of islets of Langerhans.

Immunoisolated transplantation of xenogeneic islets could solve problems concerning the immunology of islet transplantation. This study presents results from in vitro and in vivo experiments in rodents by the use of a PEEK-hollow fiber. Glucagon secretion of encapsulated islets during a 48-hour-culture period sustained on the same level from day 2 to 28. There were no significant differences in glucose (16.7 mmol/l)-stimulated insulin release after 6, 14 or 28 days in culture. Contrary, intraperitoneal transplantation of 800 encapsulated islets resulted in a normoglycemia of 3.8 days (medium survival time) which was similar to that of not encapsulated controls. It was concluded that a more open ultrastructure of the membrane tested could result in a minimization of the diffusion distance and overcome principle geometric problems of the hollow fiber model.