Albumin coating on magnesium via linker molecules--comparing different coating mechanisms.

As magnesium is a non-toxic and biodegradable metal, it is gaining more and more interest in the biomedical sector. The biodegradability is due to the corrosion of Mg in aqueous, chloride containing environment, as it is present in the body. However, corrosion of pure magnesium occurs too fast and takes place inhomogeneously on the metal surface. Moreover, Mg dissolution is connected with strong hydrogen evolution. Therefore alloying and/or coating of magnesium seem to be promising approaches to slow down corrosion and in return hydrogen evolution. This study explores coating of Mg with albumin via three different linker molecules, aminopropyl-triethoxysilane (APTES) plus ascorbic acid (VitC), carbonyldiimidazole (CDI) and stearic acid (SA). The metal samples were first passivated and after the pre-coating with the linker molecules the protein coating took place by soaking the pre-treated samples in an aqueous albumin solution. The immersion time was varied from 0.25 h up to 24 h. The success and the quality of the different coatings were documented by X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Pre-coatings were additionally characterized by contact angle and surface roughness measurements. Electrochemical measurements were carried out in simulated body fluid (SBF) to characterize the coatings in view of their corrosion behavior. Albumin coatings could be produced with every linker molecule investigated. Certain protective effects were observed already for linker SAM coated Mg, overall the systems CDI-BSA and SA-BSA showed the best corrosion resistances.