Conference Agenda

Introduction

Bioprostheses with leaflets made from decellularized animal tissue represent the current state of the art in heart valve replacement. These valves are prone to calcification and structural degeneration, which limits their lifespan and re-quires repeated surgical interventions. The goal of this project is to investigate a leaflet scaffold based on a load-oriented woven textile. It is designed to provide structural integrity and can be further processed with a hemocompat-ible and bioactive coating for in situ tissue engineering.

Methods

Mechanical testing was used to preselect the fabric configuration, followed by porosity testing. The woven scaffolds were coated with TPU chloroform (Carbothane PC-3585A, Lubrizol) and mounted in a balloon expandable TAVI stent. Accelerated wear tests were performed under simulated physiological load in a LinA testing device (AME-HIA and ac.biomed GmbH). The function of the leaflets and signs of wear were assessed by high-speed camera recordings, photography and microscopic examination. Favorable textile scaffold - stent designs were tested with a higher number of load cycles. In addition, finite element analysis (FEA) was performed to investigate the stresses in the leaflet mate-rial and individual warp threads at the leaflet-stent interface during valve closure.

Results

After design optimization, current lab samples withstand more than 200 million load cycles. Critical failure zones, especially near the commissures, were avoided by adapting the weave pattern and the way the weave is attached to the stent. The FEA revealed areas of high stresses in the woven textile and quantified the influence of stent flexibility on the load dynamics. The latest R&D results on these aspects will be presented.

Conclusion

Current results promise to achieve reasonable durability of a valve composed of woven leaflet scaffolds. Further he-mocompatibility, cell colonization, and calcification testing are required to confirm suitability as an in situ heart valve replacement.

Introduction

Technological advances in micro- and nanotechnology leads to the development of new implantable medical devices. Active implantable medical devices are increasingly playing an important role in treating and even curing many diseases that would otherwise be incurable such as chronic heart failure. Here we report results of a BMBF research project to realize core components for a minimally invasive (MIV) implantable patch electrode system. An innovative self-expandable high-flexible 3D electrode platform with new microtechnical and functional components from biomedical material multi-layers and manufactured highly cost effective with microsystem technology (MST) processes.

Methods

Individual and system level components are specified, constructed and manufactured and thereafter scientifically characterized. Suitable design concepts for advanced processes (e.g. etching, magnetron sputtering (PVD/CVD) or atomic layer deposition (ALD)) have been applied. Laboratory samples have been examined in a number of directions: function, reliability, matching requirements, safety aspects, costs, quality reproducibility, complexity with new testing and quality procedures.

Results

We present capabilities of today`s advanced MST platforms. Our project end point (functional demonstrator for MIV implantation) will be discussed. Design concepts and data from bench tests and animal experiments for long-term implants will be disclosed (mechanical, electrical, physico-chemical and functional tests).

Conclusion

Our design concept met the application's requirements for the final electrode area, biocompatibility, corrosion resistance, handleability and robustness for a chronic heart failure patch electrode. New advanced manufacturing processes from microsystem technologies in combination with sputter deposition can be used for future MIV medical devices such as bioelectronic implants. However, to realize the full potential of these modern technologies (from a therapeutic, engineering and cost perspective) require advanced design concepts, too. Here we demonstrate a highly flexible biomedical implant device platform that can be used for a variety of modern bioelectronic therapies with brought future application potentials (e.g. ablation, EP mapping, neurotechnologies, electroporation).

Wird nachgereicht siehe Remark/message from the authors to the programme committee and chairs

This study examines hydrophobic surface coatings for stimulation electrodes to mitigate foreign body reactions and encapsulation. Electrospinning of polydimethylsiloxane (PDMS) resin is explored to create fiber structures for electrode coatings. PDMS resin is succesfully processed into fiber mats. Electrospun PDMS fiber structures showed an increased water contact angle (124 °/125 °) in comparison to a cast flat film (102 °). To further increase hydrophobicity, the fabrication process of Slippery Liquid-Infused Porous Surface (SLIPS) systems with a polyurethane substrate and different natural lubricants is assessed with promising results in an increase in water contact angles up to 11°. The findings suggest the potential of these surface coatings to enhance the performance and safety of stimulation electrodes.

Introduction

Heart valve replacement in children is a major challenge. In addition to other problems, current heart valves do not adapt to the growing size of the child's heart, leading to frequent reinterventions to adjust the size of the valve. The aim of this study is to develop a scaffold structure for a biohybrid implant that can adapt to the growing size of paediatric hearts.

Methods

In order to create a textile scaffold structure that can adapt to the growing diameter and orifice area of the valve in a time-controlled manner, a warp-knitted structure made of non-degradable yarns (polyethylene-terephthalate) was spe-cifically reinforced with biodegradable fibres (polylactide, polylactide-co-glycolide, polycaprolactone). For the integra-tion of degradable fibres, direct incorporation into the warp knitting process by means of combined lappings and tai-lored integration of reinforcing fibres into the structure were investigated. Samples were stored in phosphate-buffered saline solution at 37 °C to simulate degradation in vivo.

Results

The geometry and mechanics of the scaffold were evaluated as it degraded, including diameter, surface area, strength, elongation and compliance. By combining fibres with different degradation rates and geometric structures, valve diam-eter increased by up to 50% and orifice area by up to 60%. After fibre degradation, radial elongation varied from 5% to 50% for different tailored reinforcement structures. Integrating degradable fibres directly into a warp knit structure re-sulted in diameter increases of 10 - 22% for different stitch densities. This growth capacity is equivalent to the growth of a paediatric heart valve over ten years if implanted within the first year of life.

Conclusion

By combining a non-degradable textile base structure with a controlled degradable reinforcement structure, it was pos-sible to realise a textile scaffold structure that can grow with the valve. These results are a decisive step on the way to a growth-capable heart valve implant for the treatment of small children.

At present, there are no bioresorbable systems available for the treatment of aortic coarctation in pediatric patients. However, experience with off-label used systems and knowledge of bioresorbable scaffolds in other applications suggest potential benefits. While stenting techniques are typically preferred for older children, there have been encouraging reports regarding their use in newborns and very young infants recently. Bioresorbable scaffolds could potentially close the technological gap in this area and serve as a bridge therapy for non-operable patients. This work identifies geometric and loading aspects in the light of current literature to improve the growth-responsive development of new scaffolds for the treatment of congenital heart diseases with pediatric-specific characteristics.