DThe printer looks like a futuristic microwave oven. Layer after layer, the plastic mixture is fused in a so-called “melted filament manufacturing” printing process to form a frame with a stable shell and an open-cell core. A bone segment was created with an enlarged visual model similar to Swiss cheese. Eva Schätzlein, a PhD student in the team of Andreas Blaeser in the Department of Mechanical Engineering at Darmstadt University of Technology, explained why: “Ideally, the substitute should mimic the function of real bone. For example, it must provide support and contain pores for blood vessel growth. .”
Bones are not inanimate materials, but are composed of cellular tissues. Cells ensure that the bones of our bones are renewed and small cracks or fractures heal. However, the body is unable to heal the larger defects caused by accidents or tumor removal on its own. Usually the implant must be inserted at this time. Today, for this purpose, material is taken from the patient’s pelvis or other bones.
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According to the Darmstadt research team, an intervention that may be waived. “In the future, a combination of living cells and hybrid printed enhanced structures can be used to make implants,” says TU scientist Schätzlein. Future bone substitutes may come from 3D printers.
Medical technology since the 2018/19 winter semester
In the 2018/19 winter semester, TU expanded the range of courses to include medical technology courses in cooperation with the Goethe University Frankfurt. Biomedical printing technology is still a young subject in Darmstadt. In 2019, she joined the Department of Mechanical Engineering. Andreas Blaeser leads the department focusing on the research and development of 3D bioprinting systems.
The professor has been studying various applications in this field for a long time; regenerative medicine implants such as bone substitutes are a possibility; in vitro tissue models that can replace animal experiments are another research method. This also applies to “human on a chip” research, where parts and functions of organs can be replicated on a chip. 3-D printers can even provide meat substitutes.
For many years, people have been researching new bone substitutes obtained from printers. “The main feature of our research method is the use of a hybrid 3-D bioprinting process based on filaments and the composite materials used,” Blaeser emphasized.
The team developed a composite material made of plastic polylactic acid (PLA) and bioglass. In her paper, Eva Schätzlein is studying the best mixture. The goal is to create a structure or framework in which blood vessels can grow and cells can adhere. “The biological aspects of bioglass are crucial to this,” she said.
Both PLA and bioglass are decomposed in the body and do not need to be removed in another painful operation on the patient. However, the degradation of polylactic acid is acidic and may trigger an inflammatory response.
“The cell-friendly printing process is groundbreaking work”
Schätzlein explained: “We are investigating to what extent the combination with bioglass can compensate for this effect.” She also wanted to know what effect this material has on the recruitment of bone cells and the promotion of new bone formation. The support structure made of composite materials using the printing process is an ideal growth environment for bone tissue.
However, all problems have not been resolved. “Up to now, the achievable size of alternative structures that fill living cells has been a challenge due to the limited supply of nutrients,” Schätzlein said. An under-supplied organization may die. Nonetheless: “Incorporating different material categories in a cell-friendly printing process is a pioneering work,” the professor praised the doctoral student.
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The research project is carried out in cooperation with the Orthopedic and Traumatology Center of the Gutenberg University of Mainz and the Trauma, Hand and Reconstructive Surgery Clinic of the Goethe University in Frankfurt. Bone substitutes made of PLA have been successfully tested in animal experiments, and the PLA bioglass frame will also be tested with colleagues in Mainz and Frankfurt.
Darmstadt University of Technology, Gutenberg University and Goethe University form the Rhine-Main University (RMU) alliance. Their research program provides funding for Darmstadt’s bone replacement research. Blaeser and Schätzlein are currently working on modular systems with their RMU colleagues. This includes printing parts of bones. They can be used quickly in emergencies during surgery.
The bone substitute from the printer can be molded separately. A computed tomography scan of a fracture or trauma is sufficient to calculate an anatomically perfect print file. “We conduct basic research and can collaborate with clinics for rapid application,” Blaeser emphasized.
