Chemical research

Making Implants Safer

Swiss researchers develop innovative nano-coatings

12.3.2014 | Nowadays, hip and knee replacement surgeries are among the most common surgeries in developed countries - but bacterial infections pose a serious problem. Chemists supported by the Swiss National Science Foundation have developed encapsulated nanoparticles for antimicrobial coatings of implants.
Western populations live longer, and many senior citizens enjoy a good health. In order to pursue their various activities, more and more seniors have implant surgery to replace hip or knee joints. But this surgery is not without its risks: during an operation, bacteria can reach the implant surface. Once they have colonised the surface and formed a biofilm, the implant has to be removed and the wound has to be cleaned thoroughly. No new implant can be fitted until the infection has been eradicated completely. These complications affect 2 percent of artificial hip joints, 5 - 10 percent of artificial knee joints and can affect up to fifty percent of cardiac shunt and stent operations.

Prof. Katharina M. Fromm
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Prof. Katharina M. Fromm
One way of fighting the growth of bacteria on the implant surface is the addition of an antimicrobial coating. A research group, led by Katharina Fromm from the University of Fribourg, Switzerland, has now developed such a coating. It is currently undergoing in-vivo test. This coating continually emits an antimicrobial agent - silver ions, for a duration of approximately three months. To prolong the efficiency of the coating, the researchers are currently working on a second-generation coating in which the silver nanoparticle would be encapsulated in silica. This would enhance the stability of the nanoparticle by isolating it from its environment. It would also slow down the diffusion of the silver and prolong the efficiency of the coating. Another advantage of this method: cells can tolerate a much greater number of silver nanoparticles if they are encapsulated.

To this end, the researchers have developed, within the context of the National Research Programme "Smart Materials" (NRP 62), a one-pot synthesis process to encapsulate the nanoparticles. This allows them to determine the porosity and the size of the silica container in relation to the nanoparticle it contains. Under the microscope, it looks like a nanoscopic rattle. In order to improve the performance of the coating even further, the researchers - in collaboration with Prof. Christian Bochet's research group - are working on bacterial sensors aiming to attach to the encapsulated nanoparticles. If a sensor like this were in place, the silver would only be released if a pathogen were nearby. This targeted release would further prolong the efficiency of the protection and it would prevent silver from being needlessly released into the organism.

The synthesis developed by the researchers allows for the development of various types of containers for various nanoparticles. The application potential for these nano-rattles is therefore considerable: by controlling the porosity of the container, it is for example possible to control which molecules can get close to the nanoparticles. This, in turn, would make it possible to create a nanoreactor in which chemical reactions could take place. The technique might also enable new battery designs in which each encapsulated nanoparticle would play the role of an electrode.   (© Swiss National Science Foundation SNF, AcademiaNet)

More information


  • Magdalena Priebe and Katharina M. Fromm (2014): One-pot synthesis and catalytic properties of encapsulated nanoparticles in silica nanocontainers. Particle & Particle Systems Characterization online: doi:10.1002/ppsc


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