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In cases of severe lung disease, a lung transplant is often the last resort. However, donor organs are scarce. Until then, so-called ECMO ventilation systems can support lung function. However, their design, which uses hollow-fibre membranes, limits gas exchange, leads to uneven blood flow and, together with the artificial surfaces, promotes blood clotting. A research team at the MHH, in collaboration with RWTH Aachen University, has now developed a completely new, 3D-printable membrane design that improves not only oxygen supply but also blood compatibility.
For people with severe lung diseases, a transplant of a healthy organ is often their only chance of survival. However, donor lungs are in short supply. A new artificial lung could provide a solution. A team led by Prof. Dr Bettina Wiegmann, an emergency medicine specialist and consultant in cardiac surgery at the Clinical Department of Cardiothoracic, Transplant and Vascular Surgery at Hannover Medical School (MHH), has been researching this since 2017 as part of the priority programme ‘Towards an implantable Lung’ of the German Research Foundation (DFG). Together with her research group at the Lower Saxony Centre for Biomedical Engineering, Implant Research and Development (NIFE), she is developing what is known as the biohybrid lung. This is based on extracorporeal membrane oxygenation (ECMO). In this lung support system, which is already in clinical use, blood is passed through plastic hollow-fibre membranes (HFM), which facilitate gas exchange.
The scientist has now taken a decisive step forward. Together with researchers from RWTH Aachen University, she has developed a novel membrane architecture that makes gas exchange much more efficient. This can be produced easily and with a precise fit using 3D printing, achieves significantly higher oxygen transfer and, at the same time, enables a space-saving design. The method is not only of interest for the development of implantable biohybrid lungs. In future, it could also make conventional ECMO systems more efficient and compact. The study has been published in the journal “Advanced Materials”, an internationally renowned journal for materials science.
New membrane architecture
The HFM membranes used in ECMO resemble tiny straws arranged in parallel rows. However, this arrangement creates turbulence. The flow distribution is therefore not ideal and limits the efficiency of gas exchange. Furthermore, there is an increased tendency for thrombosis to form at the interfaces between the blood and the artificial surfaces. “So far, we have only been able to use ECMO to support lung function for a limited time because the blood forms clots on contact with the artificial surfaces,” explains Professor Wiegmann. She is therefore pursuing a different solution: a completely new membrane architecture based on so-called triply periodic minimal surfaces (TPMS). In contrast to the densely packed HFM, the TPMS structure forms a continuous three-dimensional network. This allows the blood to be distributed more evenly, enabling more efficient gas exchange whilst also laying the foundation for more compact artificial lungs.
Up to 88 per cent more oxygen
TPMS structures – much like natural alveoli – have a very large surface area whilst occupying a small volume. This means that as much surface area as possible is available for gas exchange within a very small space. In the human lung, around 100 to 140 square metres of respiratory surface area is packed space-efficiently into 300 million alveoli. Whilst the TPMS structures do not yet achieve this packing density, they do avoid areas of low blood flow and reduce flow resistance. Furthermore, they can be produced easily and customised using modern 3D printing. “We have optimised the TPMS architectures. As a result, we achieve up to 88 per cent higher oxygen transfer than with conventional hollow-fibre membranes,” says Professor Wiegmann. “This means that, in future, the same or even a better oxygen supply could be possible with significantly smaller artificial lungs.”
Objective: CT lung image as a template
It is not only the architecture, but also the material used that opens up new possibilities. The TPMS membranes are made of a special silicone polymer. It is biocompatible, non-toxic and chemically very stable. At the same time, the material is highly permeable to oxygen and carbon dioxide – a crucial prerequisite for efficient gas exchange. It can also be colonised by endothelial cells. These cells also line our natural blood vessels and can regulate blood clotting. This could significantly improve the haemocompatibility of future artificial lungs.
The long-term aim of the research is to use computed tomography (CT) scans of the damaged lung to create a ‘mould’ and, based on this, to produce individually tailored artificial lung segments or entire lungs using 3D printing. Seeded with the patient’s own or genetically modified endothelial cells, the artificial lungs could then be implanted into patients and take over lung function on a permanent basis. “However, the new TPMS structure also has great potential even without endothelial cells,” emphasises the researcher. “Even as a replacement for today’s hollow-fibre membranes, it could make ECMO systems more efficient, more compact and better tolerated by the blood. In the long term, it also forms the basis for implantable biohybrid lungs.”
Expertise recognised in the USA
Professor Wiegmann now hopes that her work will continue to receive funding so that the implantable biohybrid lung may one day find its way into clinical practice – initially as a temporary solution pending a lung transplant and, in the long term, as a fully-fledged organ replacement. A recent award from the USA also demonstrates that her research and expertise are highly recognised internationally. The American Society for Artificial Internal Organs (ASAIO) has inducted the scientist into the ‘Inaugural Fellow Class 2026’ in recognition of her research achievements, her international commitment and her contributions to the further development of biohybrid organ support systems and extracorporeal therapeutic procedures. With this newly established and internationally renowned award, the professional society honours leading scientists worldwide for their outstanding contributions to the development of artificial organs, modern organ support systems and innovative translational therapeutic concepts.
SERVICE:
Further information can be found here: https://nife-hannover.de/ags/biohybridlunge/
Further information is available from Prof. Dr Bettina Wiegmann, wiegmann.bettina@mh-hannover.de.
The original paper “From Fibre Bundles to Architected Membranes: Triply Periodic Minimal Surface Architectures for Biohybrid Artificial Lungs” can be found here: https://advanced.onlinelibrary.wiley.com/doi/10.1002/adma.74361
Smaller and more efficient: Prof. Dr Bettina Wiegmann demonstrates the new TPMS membrane architectur ...
Copyright: Karin Kaiser/MHH
Smaller and more efficient: Prof. Dr Bettina Wiegmann demonstrates the newly developed TPMS membrane ...
Copyright: Karin Kaiser/MHH
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