Close-up of a cylinder in a Melt Electrowriting system showing a printed scaffold of the heart valve. Credit: Andreas Heddergott / TUM
Researchers have developed 3D-printed artificial heart valves designed to allow a patient’s cells to form new tissue. To form these scaffolds using cast electrode writing, an advanced additive manufacturing technique, the team has created a new manufacturing platform that allows them to combine different precise and customized patterns and therefore adjust the mechanical properties of the scaffold. Its long-term goal is to create implants for children that develop into new tissues and therefore last a lifetime.
In the human body, four heart valves ensure that the blood flows in the right direction. It is essential that the heart valves open and close properly. To perform this function, the heart valve tissue is heterogeneous, meaning that the heart valves have different biomechanical properties within the same tissue.
A team of researchers working with Petra Mela, a professor of medical materials and implants at the Technical University of Munich (TUM), and Professor Elena De-Juan Pardo of the University of Western Australia, have now, for the first time, imitated this heterogeneity. structure using a 3D printing process called melt electrowriting. To do this, they have developed a platform that facilitates the printing of precise custom patterns and their combination, which allowed them to fine-tune different mechanical properties within a single scaffold.
Fusion electrode writing allows the creation of precise and customized fiber scaffolding
Fusion electrowriting is a relatively new additive manufacturing technology that uses high voltage to create precise patterns of very thin polymeric fibers. A polymer is heated, melted, and ejected out of a printhead as a jet of liquid to form the fibers.
During this process a high voltage electric field is applied, which considerably reduces the diameter of the polymer jet by accelerating it and stretching it towards a collector. This results in a thin fiber typically between five and fifty micrometers in diameter. In addition, the electric field stabilizes the polymer beam, which is important for creating defined and precise patterns.
The “writing” of the fiber beam according to predefined patterns is done by a computer-controlled mobile collector. Similar to moving a slice of bread under a spoon dripping with honey, the mobile platform picks up the emerging fiber along a defined path. The user specifies this path by programming its coordinates.
In order to significantly reduce the programming effort associated with creating complex structures for heart valves, the researchers developed software to easily assign different patterns to different scaffold regions by choosing from a library of available patterns. In addition, geometric specifications such as scaffold length, diameter, and thickness can be easily adjusted via the graphical interface.
A close-up of a printed scaffold for a heart valve. The different structures that guarantee proper biomechanics are clearly visible. Credit: Munich Technical University
Heart valve scaffolds are cell compatible and biodegradable
The team used medical grade polycaprolactone (PCL) for 3D printing, which is cell compatible and biodegradable. The idea is that once the PCL heart valves are implanted, the patient’s own cells grow in the porous scaffold, as was the case in the first cell culture studies. The cells could then form new tissue before the PCL scaffold degrades.
The PCL scaffold is embedded in an elastin-like material that mimics the properties of the natural elastin present in real heart valves and provides micro-pores smaller than the pores of the PCL structure. The goal is to leave enough space for the cells to settle, but to seal the valves properly for blood flow.
The designed valves were tested using a simulated circulatory flow system that simulated physiological blood pressure and flow. The heart valves opened and closed properly under the conditions examined.
Nanoparticles allow magnetic resonance imaging
PCL material was further developed and evaluated in conjunction with Franz Schilling, Professor of Biomedical MRI, and Sonja Berensmeier, Professor of Bioseparation Engineering at TUM. By modifying the PCL with ultra-thin superparamagnetic iron oxide nanoparticles, the researchers could visualize the scaffolds using magnetic resonance imaging (MRI). The modified material remains printable and compatible with the cells. This could facilitate the transfer of technology to clinics, as scaffolding can be controlled in this way after implementation.
“Our goal is to design bioinspired heart valves that support the formation of new functional tissues in patients. Children will especially benefit from this solution, as current heart valves do not grow with the patient and therefore they need to be replaced over the years in multiple Our heart valves, on the other hand, mimic the complexity of native heart valves and are designed to let the patient’s cells infiltrate the scaffold, “says Petra Mela.
The next step on the road to the clinic will be preclinical studies in animal models. The team is also working to further improve the technology and develop new biomaterials. The results of his current study are published in Advanced functional materials.
Bioengineering of living heart valves More information: Navid Toosi Saidy et al, Spatially heterogeneous tubular scaffolds for in situ cardiac tissue tissue engineering using fusion electronics, Advanced functional materials (2022). DOI: 10.1002 / adfm.202110716
Kilian MA Mueller et al. Biomaterials Science (2021). DOI: 10.1039 / D1BM00461A
Provided by the Technical University of Munich
Citation: Heart Valves Bioinspired and Printed in 3D: Scaffolding Created by Fusion Electrode Writing Aims to Support the Formation of New Tissues (2022, June 2) Retrieved June 2, 2022
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