Surgical Tribune International

Researchers develop twofold infection protection for implants

By Fraunhofer IFAM
December 09, 2020

BREMEN, Germany: Researchers have developed a hybrid implant coating made from antibacterial silver and an antibiotic to protect patients from infections in the future. The antibiotic will be tailored to the individual needs of the patient for even enhanced protection. The project was conducted by researchers from Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) in collaboration with a research team from Charité—Universitätsmedizin Berlin.

Any patient who receives an artificial knee, shoulder or hip joint at the hospital can expect the best-possible treatment and cutting-edge medicine. However, implantation is not without its risks. On average, 1 to 2% of all patients will develop a post-surgical infection. If the level of discomfort makes another surgery necessary, an infection can be expected in up to 4% of all cases. Even if the individual risk is low, many patients are affected owing to the high frequency of the surgery. In view of demographic developments, the number of prosthesis operations will also increase steadily.

This new approach promises to significantly reduce the risk of infection. A hybrid coating of antibacterial silver and an antibiotic, tailored to the patient’s specific bacteria, is applied to the implant. The idea was developed four years ago at the Fraunhofer IFAM in Bremen. Kai Borcherding, head of medical technology and life sciences at Fraunhofer IFAM, said: “Surface treatment is one of the areas our institute specialises in. Applying this expertise to medicine was a natural choice.”

Joint project with Charité

Fraunhofer researchers further developed, tested and implemented this idea through the AntiSelectInfekt project in collaboration with researchers of the Julius Wolff Institute and the BIH Center for Regenerative Therapies of Charité in Berlin. The results are promising. “The preclinical studies have demonstrated that the hybrid implant coating effectively reduces the rate of infection,” explained Prof. Britt Wildemann, who was in charge of the studies on effectiveness and biocompatibility at Charité and who heads the Experimental Trauma Surgery Department at the University Hospital Jena.

The idea of coating implants is not necessarily new. The ability of silver and antibiotics to combat infections associated with implants has long been studied. What is new, however, is the approach of combining the two and thus vastly improving active protection against bacteria. This special coating technology also regulates release of the antimicrobial substances.

Made in Bremen: coating technology with laser

The coating process is based on tried-and-true technologies further developed specifically for this project. “The first step is to apply a structure to the surface of the titanium implant using a laser. This creates a porous layer,” explained Borcherding. Tiny pores that are mere micrometres in size appear on the titanium surface. These pores are amphora-shaped, meaning they are narrower above and wider below. In the second step, researchers used the process of physical vapor deposition to apply a layer containing silver particles.

These amphora-shaped pores can be filled during the surgery. Just before implantation, the surgeon immerses the sterile implant with silver coating in a solution containing the antibiotic. “We have seen in preclinical studies that the entire process is very simple and only takes a few minutes,” said Wildemann. Once the implant has been implanted, whether it is a hip, knee or shoulder joint, the antibiotic is released into the surrounding tissue, promptly eliminating any bacteria that could cause an infection. The effect of the silver coating is delayed and lasts much longer. The silver ions remain active for several weeks and offer protection from infection during the healing phase.

Numerous laboratory tests

Biocompatibility and osseointegration were studied both in laboratory tests with human bone cells and in the animal model. “One of the challenges during the development phase was ensuring the concentration of the antibiotic was high enough to kill bacteria, but not high enough to damage the growing bone cells,” explained Borcherding.

In addition, the pores applied to the titanium surface with the laser treatment ensure enhanced bone adherence.  “Our study has shown that surface modification increases bone contact—89% contact with implants featuring the hybrid coating, compared with 52% bone contact in the control group. We were also able to prove that cells grow into the amphora-shaped pores and thus anchor the implant much more effectively”, said Wildemann.

The project was already met with great interest among implant manufacturers and providers of coating services, particularly because no new implants need to be developed for the process, since products that are already available can be coated. Discussions with manufacturers are being intensified in the final stage of the project to ensure the technology can be used for patients in the near future.

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