Early-stage research into biomimetic elastic polymers that can imitate the mechanical properties of pericardial tissue and be used to produce patient-specific implants via 3D printing and electro-spinning is achieving promising results. The first clinical studies could happen as soon as 2022.
|The initial application of the synthetic pericardium replacement material is the surface of an extra-vascular cardiac support system. Image courtesy AdjuCor GmbH.|
Initiated in April 2019, the publicly funded PolyKARD project includes the participation of AdjuCor GmbH, the Fraunhofer Institute for Applied Polymer Research IAP, the NMI Natural and Medical Sciences Institute, Young Optics Europe GmbH and pro3dure medical GmbH. Each partner brings specific expertise to the project, which is managed by German engineering association, VDI Verein Deutscher Ingenieure. If successful, the development of these polymers and the associated manufacturing technologies could be a lifeline for people suffering from heart disease.
Approximately 23 million people worldwide suffer from cardiac insufficiency, and the number is increasing, notes a press release from Fraunhofer IAP (Potsdam, Germany), part of the Fraunhofer network, Europe’s largest application-oriented research organization. The number of heart transplants is stagnating at about 3000 per year worldwide, and artificially produced implants could help many patients who are waiting for a donor organ. The challenge, according to Fraunhofer IAP, is developing synthetic elastic tissue that retains its mechanical properties for many years, is 100% biocompatible, and is not rejected by the immune system.
In the PolyKARD project, polymers are being developed that mimic the biological and mechanical material properties of the pericardium, the double-walled sac that contains the heart. Currently, pig and cow pericardia are used to replace human heart valves or to reconstruct blood vessels. However, the processing of animal tissue is expensive, does not guarantee long-term mechanical stability and the quality is inconsistent, said Fraunhofer. The practice also raises ethical and religious issues.
"In this project, we are developing biomimetic pericardial replacement materials that can be used, for example, for artificial pericardium, heart valves, blood vessels, stents, tendons or septum occlusions,” explained Dr. Wolfdietrich Meyer, who heads the project at Fraunhofer IAP. “The special feature of these implants is that they are made of photopolymers and can be produced individually using a 3D printer or by electro-spinning. The monomers are developed as inks or resins. They only polymerize when they are irradiated with UV light,” said Meyer.
The research team at Fraunhofer IAP is synthesizing a photo-crosslinkable material consisting of different polyurethane segments and collagen components.
The newly synthesized polymers are then tested for in vitro cytotoxicity at the NMI Natural and Medical Sciences Institute, where they are processed by means of different 3D-printing methods and electro-spinning. The spinning process is used to create porous structures that can grow together with the patient's own body tissue. The carrier substrates produced are characterized in terms of their mechanical and biological properties. Special emphasis is placed on the reproduction of the mechanical properties of the pericardium and the growth behavior of cells.
In its first application, the biomimetic polymer will be used to print a novel surface for an extravascular cardiac support system developed by Munich-based AdjuCor GmbH. The patient-specific mechanical implant is positioned completely outside the blood flow in the pericardial cavity around the epicardial surface of both heart chambers. "A biomimetic pericardial replacement material would cause only minor immune reactions and would thus lead to a gentle healing phase. This could further shorten intensive care and hospital stays," explained heart surgeon and AdjuCor CEO Prof. Stephen Wildhirt.
Pro3dure medical GmbH is tasked with establishing the upscaling process of the photopolymers as well as the resin synthesis under consideration and ensuring that they comply with Good Manufacturing Practices and other regulatory requirements.
Young Optics Europe GmbH, which has processed biocompatible photopolymers for Class I and IIa medical products using its 3D printers, is developing a 3D-printing system suited for the production of Class III medical products as part of the PolyKARD project.
At a meeting today, the PolyKARD partners presented the first milestones in the not-quite one-year-old project. “We have already successfully synthesized and printed the first elastic photo-urethane resins from non-toxic starting materials,” said Meyer. "In the future, we would like to apply the medical concept of wholeness even more strongly to our chemistry. We want to develop more materials based on renewable raw materials for 3D printing and electro-spinning that are biocompatible and can be processed with the highest precision. We are also keeping an eye on the life cycle of the component and, if necessary, environmentally friendly disposal," said Meyer.
The PolyKARD project is funded for three years.