Magnesium's first corrosion layer slides across the implant surface in student calculations

Magnesium hydroxide is one of the first compounds to form on the implant surface as degradation begins ^[8]. The second student team looked at how that layer sits on the metal, and at what three amino acids do to it ^[9]. "We found that magnesium hydroxide does not bind very strongly to the magnesium surface and can move relatively freely across it," a member of the team said in the phys.org report ^[10]. On those results the weak link is the interface with the metal. "One of the most interesting findings was that the bond between different magnesium hydroxide layers is much stronger than the bond between the hydroxide and the magnesium surface itself," the same team member said ^[12].

Both published papers are density functional theory studies, by their own titles ^[22]. Everything the report attributes to them is of one kind: how strongly a molecule or a layer binds to a magnesium surface, and whether a protective coating forms there ^[25]. A corrosion rate, or a figure in weeks, is missing from both accounts ^[26].

The two teams disagree on how much the choice of amino acid buys. Alva Limback, Olof Hildeberg, John Bolin and Amanda Goold reported that glycine, proline and hydroxyproline, all naturally present in collagen, can contribute to a protective coating, and that the effect was clearest when the magnesium contained small amounts of other metals ^[6]. That, according to phys.org, could help researchers develop implants that degrade at a slower and more controlled rate ^[23]. The second team's summary is flatter: "We also observed that adding an amino acid affected the interaction to some extent, although the specific amino acid made very little difference," the team member said ^[11]. Four distinct amino acids appear across the two studies, with glycine and proline in both ^[21].

Magnesium is biodegradable, unlike titanium or steel, and dissolves once it has done its job ^[13]. "This means patients do not need a second operation to remove the implant once the bone has healed, which is often necessary with more conventional materials," Hildeberg said ^[15]. Schroder, a professor of Quantum Device Physics, said the same logic applies to stents: "Unlike traditional stents, which are typically made from metals that remain permanently in the body, magnesium gradually corrodes in bodily fluids and is converted into substances that the body can process naturally" ^[17].

The phys.org headline says amino acids and a bone mineral "may help control magnesium implant breakdown" ^[19], and both papers it describes are about amino acids ^[25]. Nine undergraduates are named as authors between them ^[20]. Publishing a bachelor's thesis in a scientific journal is relatively uncommon, and three from one group within three months is rare ^[24]. "It feels fantastic, of course. I certainly wasn't expecting this," Limback said ^[4].