Getting implants close to the bone using magnets
Dr Athina Markaki
Dr Athina Markaki, wasn't planning to apply her engineering expertise to biology. She was working on a material sciences project with Cambridge colleague Professor Bill Clyne when work on controlling the orientation of ferritic (magnetic) stainless steel fibres led to the idea that the bonded fibre networks could be used on the surface of prosthetic implants surfaces. The fibres could help bone grow around the implant, increasing implant durability. Currently, hip prostheses only last up to about 15 years before they loosen, requiring replacement.
Markaki built upon several well established findings in the field. She knew from her previous work that interconnected networks of slender fibres could perform as actuators, converting input energy into physical movement. She also knew that cementless implants work by coaxing bone into growing around the implant.
“The idea of using a porous material has been around for decades,” says Markaki, “What’s different about this is that it’s smart design. This porous coating can change shape.” The idea involves a porous surface layer made of ferromagnetic fibres that is attached to a conventional prosthesis. After the surgery, a magnetic field is applied externally, minutely displacing the fibres and any bone cells that have started growing around them. The resulting strain promotes growth of bone cells and integration of the implant into the bone itself.
“The treatment would be applied only in the first few weeks after transplantation,” says Markaki, explaining that a magnetic field of around 1 Tesla would be used, about one third the magnetic energy used for a MRI scan. Importantly, the proposed treatment could be used in the patient’s home, fitting in with a growing healthcare demand to replace hospital treatments with home treatments.
IT’S SMART DESIGN. THIS POROUS COATING CAN CHANGE SHAPE. I HAD AN IDEA AND IT DEVELOPED INTO A PROOF OF CONCEPT.Dr Athina Markaki
Markaki initially tested the idea using a model created for such "magneto-mechanical activation" and confirmed its potential with experimental measurements (1) gathering enough data to net a prestigious European Research Council (ERC) grant of €1.5 million which allowed her to set up a multi-disciplinary research lab in Cambridge. First, Markaki had to find the right material. The fibre networks had to be able to support bone growth, without overly damaging cells or stimulating inflammation, and have good mechanical properties.
By the end of the ERC grant in 2016, Markaki’s team had proof of concept data supporting the potential of magneto-mechanical actuation. In vitro experiments show that ferromagnetic fibres, chosen for their size and combability with bone cells (osteoblasts), stimulated osteoblast growth (2,3). More recently, the team completed in vitro experiments showing that magnetically actuated scaffolds had upregulated expression of genes responsible for bone formation (unpublished data).
Markaki is now collaborating with her university commercialisation office to define future steps. “We need to look at the advantages of our design, patents, IP rights, costs, design, processing”, says Markaki, “This doesn't come naturally for an academic!”
Something that does come naturally to Markaki is a sense of teamwork. “To do such an interdisciplinary research single-handedly is extremely difficult, says Markaki. “The award of the ERC Starting Grant gave me the opportunity to employ a critical mass of researchers over a long period of time effectively allowing me to push this project forward”. Her team is multi-disciplinary, including engineers, materials scientists and biologists. The multi-disciplinary approach has paid off. “I had an idea and it developed into a proof of concept” she says.