For several years, scientists have been working on the development of biodegradable implants that would exhibit strength, flexibility, durability and the ability to dissolve harmlessly in the body. Magnesium-based alloys have been found to be the most promising candidates for that purpose due to their mechanical stability, favorable dissolution properties and their ability to be absorbed by the human body without any toxicity. However, they present one major drawback: as they dissolve, they produce hydrogen gas bubbles that linger around the implant and hinder the bone healing process.
The new metallic glass synthesized by Dr. Zberg and his colleagues, under the leadership of Prof. Jorg Löffler at the EHT Zurich, shows a fundamentally different behavior from previous materials synthesized in the past, and appears to eliminate the problem of hydrogen-forming gas. By producing a metallic glass structure, the researchers were able to develop a magnesium-zinc-calcium alloy containing a high proportion of zinc (35%), far superior to the usual percentage used in traditional metals. Indeed, in traditional metals, undesirable crystalline phases precipitate in the magnesium matrix above a maximum amount of 2.4% zinc atoms. On the other hand, the amorphous structure of metallic glass, produced by rapid cooling of the combined mixture of molten materials, does not present such limitation.
By producing a magnesium (60%)-zinc (35%)-calcium (5%) glass, the researchers were able to dramatically alter the corrosion behavior of the magnesium contained in the alloy, and therefore significantly reduce the formation of undesirable hydrogen gas in the body. In fact, animal studies performed by Zberg et al., reported no clinically observable production of hydrogen-forming bubbles during the degradation process of the implant. Further studies and clinical tests will be needed to determine whether the new metallic glass fulfills all criteria for actual implementation in patients.