printed scaffold Image
A close-up of a printed scaffold for a heart valve. The different structures that ensure the appropriate biomechanics are clearly visible. Andreas Heddergott/TUM

Researchers from the Technical University of Munich (TUM) and the University of Western Australia used melt electrowriting have created the first-ever 3D printed heart valve with a heterogeneous structure as is seen in human heart valve tissue. This heterogeneous property is essential to the proper opening and closing of valves, so the development holds great potential for the future of artificial valve replacement, especially in children who need adaptability as they grow.

The team developed a platform that precisely prints customized patterns and pattern combinations, allowing the team to perfect various mechanical properties within a single scaffold, as well as created software that eased the difficulty in creating complex heart valve structures.

“Our goal is to engineer bioinspired heart valves that support the formation of new functional tissue in patients,” says Petra Mela, Professor of Medical Materials and Implants at TUM and a leader of the study. “Children would especially benefit from such a solution, as current heart valves do not grow with the patient and therefore have to be replaced over the years in multiple surgeries. Our heart valves, in contrast, mimic the complexity of native heart valves and are designed to let a patient’s own cells infiltrate the scaffold.”

In melt electrowriting, a polymer—in this case medical-grade polycaprolactone (PCL)—is melted and pushed from the printing head in a liquid stream. A high-voltage electric field narrows the diameter to 5–50 μm and stabilizes the stream for precision as it follows a predetermined path via the research team’s software. The software reduced the need to assign individual patterns to different scaffold sections, which would be incredibly time consuming without the program. In addition, the research team worked with other departments to modify the PCL with superparamagnetic nanoparticles, which allow MRI visualization of the scaffolds so they can be monitored after implantation.

Because the team used PCL for printing, they are both biodegradable and cell compatible, allowing a patient’s cells to grow on the scaffold and form new tissue before the scaffold degrades. The PCL scaffold is surrounded by a material that imitates the natural elastin of heart valves and provides micro-pores small enough to seal adequately by large enough to allow cells to enter. The team’s first cell cultures showed success with cell growth on scaffolds, and the heart valves worked properly in the circulatory system simulation with which the researchers tested.

The team is currently working to improve the technology and is looking to begin pre-clinical studies in animal models.