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.

Acoustomechanical properties of open TTP titanium middle ear prostheses.

OBJECTIVE: The purpose of the study was to identify acoustcomechanical properties of various biostable and biocompatible materials to create a middle ear prosthesis with the following properties: (i) improved handling including a good view of the head of the stapes or footplate and adjustable length, (ii) improved acoustical characteristics that are adequate for ossiculoplastic. The identified material should serve to build CE and FDA approved prostheses for clinical use in patients. METHODS: Test models made of Teflon, polyetheretherketone, polyethylenterephtalate, polysulfone, gold, Al2O3 ceramics, carbon and titanium were investigated for their potential to fulfill the requirements. Acoustical properties were investigated by laser Doppler velocimetry (LDV) in mechanical middle ear models (MMM). Measured data were fed in to a recently created computer model of the middle ear (multibody systems approach, MBS). Using computer-aided design (CAD) measured and computed data allowed creation and fine precision of titanium prostheses (Tübingen Titanium Protheses, TTP). Their handling was tested in temporal bones. Acoustomechanical properties were investigated using the MBS and mechanical middle ear models. MAIN OUTCOME MEASURES: Input impedance, mass, stiffness, and geometry of test models and prostheses were determined. Furthermore, their influence on the intraprosthetic transfer functions and on coupling to either tympanic membrane or stapes was investigated. RESULTS: Final results were FDA- and CE-approved filigreed titanium prostheses with an open head that fulfilled the four requirements detailed above. The prostheses (TTP) were developed in defined lengths of between 1.75 and 3.5 mm (partial) and 3.0 and 6.5 mm (total) as well as in adjustable lengths (TTP-Vario). CONCLUSIONS: The results suggest acoustomechanical advantages of TTPs because they combine a significantly low mass with high stiffness. In contrast to closed prostheses, the open head and filigreed design allow an excellent view of the prosthesis foot during coupling to the head or footplate of stapes, contributing to an improved intraoperative reliability of prosthesis coupling.

Cultivation of porcine hepatocytes in polyurethane nonwovens as part of a biohybrid liver support system.

Many patients suffering from end-stage liver disease cannot be transplanted within reasonable time due to the shortage of donor organs. Bioartificial liver support systems may contribute to the liver regeneration or bridging the time until a liver graft for transplantation becomes available. Nonwovens with integrated oxygenation capacity have been developed and manufactured by melt blow technology using thermoplastic polyurethane. Capillary membranes for oxygenation were integrated into the nonwoven during the processing. The polyurethane nonwoven structures with adapted pore size and high pore volume allow high cell densities in the hepatocyte culture. The three-dimensional cell culture was housed by a flow bioreactor system and was integrated in a closed loop circulation with monitoring possibilities for pressure, pH, temperature, ammonia, and oxygen. Hepatocytes were isolated from rats or pigs by collagenase perfusion and infused into the medium-perfused circulation. Cells showed high viability and hepatocyte specific cytochrome P450-dependent metabolic function in culture (MEGX test).