New Gel Promotes Bone Growth on Orthopedic Implants

A research group at Uppsala University in Sweden has developed a new responsive coating for implants used in surgery to improve their integration into bone and to prevent rejection. Neutron scattering experiments at the Institut Laue-Langevin (ILL) in France have shown how a protein promoting bone growth binds to this surface and can be released in a controlled way.

Orthopaedic implants must last for many years and success for these surgical components depends on integration into adjacent bone tissue. Gels made by modifying hyaluronan, a large biological molecule, can be used to coat implants. A new paper in Advanced Engineering Materials shows that the coated titanium surfaces can bind protein molecules that promote bone formation. These can be released slowly once the surface comes in contact with a solution of calcium ions. This process would stimulate the growth of bone on the implant.

The gel layers, a few millionths of a millimeter thick, were characterised using neutron reflection at the ILL, a technique that provides a detailed picture of what happens at a surface. In their new paper the research team showed that the protein, BMP-2, that encourages bone growth was bound to the gel. They also demonstrated that the layer of protein was stable in water but could be released slowly by adding solutions containing calcium, a process that was observed in real time using neutron reflection to track the amount of protein at the surface.

The research group has now launched trials of similar materials for metal implants in rabbits. These ongoing studies are made in collaboration with the Swedish University of Agricultural Sciences in Uppsala and they provide a step towards transfer of the results to clinical applications.

“We envisage that the materials will be used in medicine to modulate the healing process in bone”, said associate professor Dmitri Ossipov. “Neutrons are an ideal tool to understand the interactions of metal surfaces, polysaccharide biopolymers, and proteins thanks to a contrast matching technique that highlights only the protein components at the interface.”

“Neutron scattering techniques are increasingly relevant to optimise bio-materials and to study systems that relate to health. The importance of combining conventional laboratory studies with those at a large-scale facility to give a complete picture of a process was proven once more.” said Dr. Giovanna Fragneto, of the Institut Laue-Langevin.