A new biodegradable stent to safely deliver heart valves for young patients
Researchers have developed a biodegradable stent that helps slide replacement tissue-engineered valves into the heart, before disintegrating once the valve has fully integrated with the patient’s heart tissue. These new stents are more flexible, unlike the metal stents that are currently used for minimally invasive heart valve replacement.
New avenues in heart valve technology
Cutting edge tissue-engineered replacement valves can adapt and grow as the patient does, unlike traditional synthetic or bioprosthetic valves1. This could avoid multiple valve replacements in children as they outgrow their old replacement valve. However the metal stents currently used to deliver and support the replacement valve don’t have this flexibility, and can cause problems such as thrombosis. In addition, the stent’s support is only needed until the tissue engineered valve has integrated into the patient’s own tissue. A disappearing biodegradable stent has been developed to tackle this problem by a team from Eindhoven University, the Netherlands.
Using computational modelling and 3D printing technology, the team confirmed functionality and degradation of their prototype stent in a proof-of concept study2. “To the best of our knowledge, this was one of the first successful attempts to create a biodegradable stent for heart-valve delivery and we certainly hope that the development of biodegradable stents evolves hand in hand with the progress in heart valve technologies,” said one of the researchers, Dr María Cabrera, Department of Soft Tissue Biomechanics and Tissue Engineering at Eindhoven.
The researchers chose a polymer that would allow the stent to be 3D printed, and designed an homologous polymeric stent using computational modelling. Experiments to test the mechanical strength and the crush and crimping properties of the prototype validated the predictions of the computer model. The mechanical performance was comparable to that of conventional metal stents used for heart valve implantation. In enhanced degradation laboratory condition, the polymer degraded over time, becoming porous and cracking after 2-3 weeks. The speed of degradation was affected by factors such as temperature, humidity and the presence of active enzymes. The researchers suggest that the body’s own scavenger cells could then sweep up the remnants of the degraded stent via a process called phagocytosis.
Research and business go hand in hand
The research is still in its initial phases as the group continues tweaking the material properties of the stent and its design, which will also comply with the 3D printing requirements. The next step is to move their design into translational animal models. But the group knows that challenges lay ahead.
“Bringing a high-risk class III medical device to the market is a costly and extensive process”, said Dr Cabrera. “It is fundamental to find an optimal biocompatible and biodegradable material that is suitable for the chosen manufacturing/3D printing technique, that fulfils the mechanical requirements of the application, and that can remain mechanically competent for a certain period before reducing its force due its degradation.”
Dr Cabrera is aware that a long journey lies ahead after perfecting their stent design. All going well, that journey will take them from confirmatory pre-clinical trials to proof of safety and efficacy in clinical trials and market approval. The research group have already made changes to their stents to consider cost-effective manufacturing. Dr Cabrera highlighted the importance of also considering the business case behind medical research. “If your ambition is to bring a product to the patient, you must have a solid scientific base but if you don’t think about the business side of it, it might not go beyond the research phase”, said Dr Cabrera.
According to Dr Cabrera, teamwork is important to succeed. “Multidisciplinary work is imperative to design high performance medical devices. Regulatory experts should ideally be part of your team. People with an entrepreneurial vision provide context and the right focus to your development.”
…WE CERTAINLY HOPE THAT THE DEVELOPMENT OF BIODEGRADABLE STENTS EVOLVES HAND IN HAND WITH THE PROGRESS IN HEART VALVE TECHNOLOGIES…
Confidence is the key
Dr Cabrera believes building up confidence in your research is important. “Your work is constantly being scrutinized, evaluated and criticized. In addition to believing in your ideas, you also have to develop expertise in different fields and face several barriers as you progress. Trying to bring a medical device to the market is not an easy task but it is a lot easier when you are able to covey confidence to the people you interact with. I built up that confidence when I realized that the real challenges appear when you put things into practice. It is then that you can either figure out the way to solve them or try to find people with the right expertise to guide you. It’s not much more complicated than that. My advice would be: don’t be afraid to take the lead, challenge your thinking, learn from the experts and be persistent.”
MY ADVICE WOULD BE: DON’T BE AFRAID TO TAKE THE LEAD, CHALLENGE YOUR THINKING, LEARN FROM THE EXPERTS AND BE PERSISTENT.
Driessen-Mol A, Emmert MY, Dijkman PE, et al.Transcatheter implantation of homologous “off-the-shelf” tissue-engineered heart valves with self-repair capacity. J Am Coll Cardiol 2014;63:1320–1329.
Cabrera MS, Sanders B, Goor Olga JGM, et al. Computationally designed 3D printed self-expandable polymer stents with biodegrading capacity for minimally invasive heart valve implantation: a proof of concept study. 3D Print Addit Manuf. 2017; 4: 1. Published online: DOI: doi/10.1089/3dp.2016.0052