Additive Manufacturing Tissue Replacement from the 3D Printer

Teams from the Fraunhofer Institute for Applied Polymer Research IAP and the NMI Natural and Medical Sciences Institute have developed a biomimetic tissue substitute that combines defined mechanical and biological properties.

The development of functional implants places high demands on materials: they must be both mechanically resilient and biologically compatible. Natural tissue such as the pericardium has complex properties that can only be reproduced to a limited extent with conventional plastics. In particular, the non-linear stretching behavior—initially flexible, but then becoming significantly stiffer as the load increases—is considered a key challenge for material development. Against this background, the "PolyKARD" project (FKZ 13XP5087), funded by the Federal Ministry of Research, Technology and Space BMFTR, aimed to develop a biomimetic tissue substitute that technically reproduces these properties and can also be adapted for various medical applications.

By selectively combining structural design and biomaterials, we can achieve mechanical properties that closely resemble those of natural tissues.

Dr. Hadi Bakhshi from Fraunhofer IAP

Applying Wave-Shaped Metastructure to Polymer Film Using 3D Printing

In the project, the Fraunhofer IAP at the Potsdam Science Park worked with the NMI to develop a multi-layer structure that combines defined mechanical and biological properties. The basis is a dense polymer film made of polyurethane acrylate. A wave-shaped metastructure is applied to this using 3D printing. This structured layer largely determines the mechanical behavior of the tissue substitute. Electrospun collagen is then applied in a process researched at the NMI, which supports the biological functionality. The quality of the collagen fibers is monitored using special enzymatic and non-invasive spectroscopic analyses. Our tensile tests show a very similar stretching and strength behavior to that of natural pericardial tissue. When stretched, the waves elongate, keeping the material flexible. Only at higher elongation does the stiffness increase abruptly, explains Dr. Hadi Bakhshi from the Fraunhofer IAP, who developed the material and the printing technology for the structural design together with Dr. Wolfdietrich Meyer. Meyer adds: "Through the targeted combination of structural design and biomaterials, we can realize mechanical properties that come very close to those of natural tissue.

Biomimetic And Biocompatible

Specific cell-material interaction studies at the NMI show that the material is well tolerated. Cytotoxicity tests did not reveal any adverse effects on cells. In addition, studies with human skin fibroblasts and epithelial cells indicate that the three-dimensional morphology of the fiber mesh provides a favorable environment for cell adhesion and growth.The results show that technical materials and biological functionality can be specifically produced and combined to create biomimetic materials, says Dr. Hanna Hartmann from the NMI. This opens up new possibilities for the development of biohybrid implants. That is why we have now jointly applied for a patent for this tissue substitute, which is not limited to a single application. Rather, the material concept can be transferred to various medical fields of application, such as artificial blood vessels, stent grafts, replacement materials for the dura mater or applications for artificial skin.

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