Coating technique helps bionic implants fit right in

Six million dollars probably wouldn’t get you much of a bionic man these days, but a new process for coating metal implants could vastly improve the lives of the growing number of people who have undergone complicated total joint replacement surgeries. The new electrochemical process improves the implants’ functionality, longevity and integration into the body by producing a coating that is virtually indistinguishable from the body’s own material.

When today’s surgeons reconstruct joints in the human body using metal implants they often coat the implants with a material called synthetic hydroxyapatite - a material is similar to apatite, the main inorganic constituent of enamel, dentin and vertebrate bone. This allows the implant to better integrate to the adjacent bone, and also prevents poisonous materials from leaking from the metal of the implant into the blood stream.

To apply the synthetic hydroxyapatite a technique called plasma-spraying is traditionally used. But Tel Aviv University researcher Professor Noam Eliaz of the School of Mechanical Engineering found that placing the metal implant into a bath of electrolyte solution and applying an electric current resulted in a coating that more closely mimics the real material. Examined under a microscope, it is virtually indistinguishable from the body's own material, which helps the body accept a new implant. The new coating process actually resulted in a 33% decrease in the level of materials failure for implants.

"The surface chemistry, structure and morphology of our new coatings resemble biological material," explains Prof. Eliaz. "We've been able to enhance the integration of the coating with the mineralized tissue of the body, allowing more peoples' bodies to accept implants."

Since the electrochemical process works at lower temperatures than plasm-spraying biological materials can also be incorporated into the coating. Nano-particles will be used to reinforce the coating and it will also have the potential to incorporate biological material or drugs during the process itself.

"The reinforcement of nanoparticles will improve the mechanical properties and may also improve the biological response. Drug incorporation may reduce the risk of post-surgery infection and even catalyze the growth of the bone,” said Prof. Elias.

Pro. Eliaz’s findings are published in the journal Acta Biomaterialia.