Surface Treatment Fast Coating Process for Infection-Free Bone Implants

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Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Bremen have developed an innovative surface functionalization for bone implants that can be loaded with an antibiotic to prevent complications from infections after implant placement.

Complications from infections are not uncommon after implant placement. The risk increases with heavily contaminated wounds, which are particularly common in war zones like Ukraine—yet many bone injuries need treatment there. Given the heavy burden on Ukraine's healthcare system with a multitude of poorly healing bone defects, the Fraunhofer IFAM decided to help in 2023. In addition to the news situation, personal connections were decisive: "Two of our employees are from Lviv and were involved in the project from the very beginning. Through them, contact was established with the National Rehabilitation Center Unbroken in Ukraine, with which we are now working closely to best understand the local needs and further develop the technology in a targeted manner," says Dr. Kai Borcherding, Head of the Medical Technology and Life Sciences Division at Fraunhofer IFAM. The MAOmed project is funded by the Fraunhofer Future Foundation.

Special Process Creates Pores on the Surface

The researchers' idea: They use the so-called Micro-Arc Oxidation (MAO) to create an innovative surface on titanium implants. The metal parts are immersed in an electrolyte solution containing silver salts—a conductive liquid—and exposed to a voltage of up to 300 volts. High-energy plasma discharges form a silver-containing oxide layer on the material within a few minutes, where pores are created through targeted current control, and silver is incorporated as nanoparticles. These reservoirs can then absorb antibiotics or other active substances like a sponge.

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Local Antibiotic Delivery And Silver Reduce the Risk of Infection

Through the selection of the electrolyte and process control, the researchers can adjust the resulting pore structure in terms of size and design. This is crucial for the loading capacity and the duration of antibiotic release: "After completing the MAO layer, the metal parts are immersed in a highly concentrated antibiotic solution. The pores uniformly absorb the active substance up to a defined capacity through capillary forces, which is then released in the body through diffusion," explains Linda Gätjen, Co-Head of the Polymer Chemistry and Material Behavior Department at Fraunhofer IFAM. "How the antibiotic is released over the desired period was also tested directly here at the institute through in-vitro tests after developing the surface and successfully finding project partners." In laboratory tests, the researchers were also able to demonstrate that the integrated silver particles provide additional support to the antibiotic.

Overall, there are only a few solutions for medical devices that use an antibiotic-containing coating, and when they do, the manufacturing process is much more complex.

Kai Borcherding

In the field of implants, this type of surface treatment is entirely new: "There is nothing comparable on the market so far. Overall, there are only a few solutions for medical devices that use an antibiotic-containing coating, and when they do, the manufacturing process is much more complex," explains Kai Borcherding.

Simple And Fast Coating Process

The simple setup—even under challenging conditions—is a major advantage of the method: Essentially, a power supply and a cooling unit for the immersion bath are sufficient to carry out the MAO coating process. This makes it so simple and cost-effective that it could even be implemented directly in crisis areas during later development stages. Additionally, the excellent biocompatibility of the MAO surface ensures good and rapid integration of the implant into the body.

How the innovative coating performs in practice is to be tested in the future in Ukraine. The next steps initially involve the preclinical further development of the technology and clinical studies that could be conducted at the Unbroken National Rehabilitation Center in Lviv.

The method is also garnering interest in Germany. KLS Martin, as a technology partner of Fraunhofer IFAM, has already provided sample implants that the Bremen researchers are currently working with—a first step towards application. Dr. Tobias Wolfram, Head of Implant Research at KLS Martin, explains: "In addition to the high ethical value of the project, we see great potential in the MAO method for medical technology—not only in the field of bone implants. We are happy to support the team with our expertise and materials."

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