The bioactive PCL and glass composite supports the treatment of broken bones

A broken bone that does not heal places a huge burden on patients, which often leads to the need for further, additional surgeries. Scientists at the Fraunhofer Institute in Germany have developed a composite material used to treat such cases of bone nonunion. The resulting implant (called a scaffold) is expected to significantly improve the effectiveness of treatment and accelerate the fracture healing process. The material consists of a combination of biodegradable polymer and bioactive glass and can serve as the main and load-bearing structure. Its purpose is to inhibit the growth of bacteria at the wound site and support the growth of new bone structures.

The Fraunhofer Institute for Manufacturing Technologies and Advanced Materials IFAM in Bremen provided an effective solution in the joint research project SCABAEGO (Scaffold Bioactive Glass-Enhanced Osteogenesis). The aim of the project was to test the working hypothesis that the use of bioactive materials in surgery supports the healing process and reduces the risk of infection. The Institute’s partners in this project are the Department of Trauma and Reconstructive Surgery at the University Hospital of Heidelberg and the BellaSeno company based in Leipzig, specializing in medical engineering.

Scientists at Fraunhofer IFAM have developed a composite material consisting of the biodegradable polymer polycaprolactone (PCL) and bioactive glass. This composite is then used to 3D print custom-made structures that support bone fracture sites. Previously, the structure of the damaged bone is mapped using computed tomography (CT), and a specially adapted structure replaces its missing part. The printed scaffold is filled with bone marrow taken from the iliac crest or larger long bones. This ensures that the biological bone replacement material (autologous bone disc, ABG) is firmly seated and the fracture site heals safely.

The innovative medical product provides even more benefits. “The bioactive glass in the scaffold raises the pH of the environment to alkaline. The next thing we want to investigate is the expected inhibition of bacterial growth,” explains Dr. Kai Borcherding, head of the Medical Technology and Life Sciences business unit at Fraunhofer IFAM. Scientists expect that this will ultimately significantly reduce the risk of post-operative infection.

Bioactive glass also supports the growth of new bone at the fracture site. When glass comes into contact with body fluids, it turns into hydroxyapatite, a chemical compound formed primarily from calcium phosphate and a substance very similar to bone. “Thanks to bioactive glass, we can address the problems faced by clinics – we can inhibit the growth of bacteria and provide effective support for bone healing. After six to seven years, the printed scaffold will completely biodegrade and transform into bone,” says Tobias Großner, MD, trauma surgeon and head of experimental trauma surgery at the University Hospital of Heidelberg.

Bioactive glass is already used in the treatment of bone defects. What’s new is its combination with PCL on an industrial scale. Scientists at Fraunhofer have managed to bond glass and PCL, creating a composite material that can be used directly in the additive manufacturing process. The main result of this is the ability to produce customized 3D-printed scaffolds. Manufacturing composite material on an industrial scale is simple and quick. “The PCL polymer is mixed with glass pellets and a solvent before undergoing multiple processing steps. Finally, the solvent is removed by drying and the residual composite is finely ground,” explains Borcherding.

Project partner BellaSeno “prints” a scaffold from this material using a 3D printer. “We use 3D printing, so we can create each scaffold individually to fit the fracture site in each patient,” says Dr. Mohit Chhaya, managing director of BellaSeno and project coordinator. Before that, a computed tomography of the damaged bone is performed. A virtual 3D image of the bone can then be created. Using this data, the 3D printer builds a scaffold that perfectly fits the bone. “Each patient receives a unique, tailor-made scaffold. This avoids the time-consuming mechanical adjustment of the implant in the operating room,” says Großner.

Going beyond current procedures, the innovative composite material should contribute to significant progress in treatment. The modern technique involves covering the fracture site with bone cement during the initial surgery. The human body perceives this cement as a foreign substance and protects itself with the periosteum (bone membrane). This is known as the Masquelet induced membrane technique. The process may take up to two months – after this period the patient must undergo surgery again. This time, the surgeon cuts the periosteum, removes the cement, fills the space with autologous bone and re-seals the periosteum. Until now, there were few options for fractures to heal safely and without disruption.

The SCABAEGO research team is already investigating this concept in vitro and in vivo through preclinical tests in collaboration with the University Hospital of Heidelberg. While this work is ongoing, the composite formulation is being optimized. The share of bioactive glass in the scaffold can range from 10 to 30 percent. “We are experimenting with mixture proportions so that we can make the most of the biologically positive properties of the glass while maintaining the strength of the scaffold core,” says Borcherding.


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