title: The effect of treatment temperature on corrosion resistance and hydrophilicity of an ionic liquid coating for Mg-based stents.
abstract: Mg alloys are attractive candidate materials for biodegradable stents. However, there are few commercially available Mg-based stents in clinical use because Mg alloys generally undergo rapid localized corrosion in the body. In this study, we report a new surface coating for Mg alloy AZ31 based on a low-toxicity ionic liquid (IL), tributyl(methyl)phosphonium diphenyl phosphate (P1,4,4,4 dpp), to control its corrosion rate. Emphasis is placed on the effect of treatment temperature. We showed that enhancing the treatment temperature provided remarkable improvements in the performances of both corrosion resistance and biocompatibility. Increasing treatment temperature resulted in a thicker (although still nanometer scale) and more homogeneous IL film on the surface. Scanning electron microscopy and optical profilometry observations showed that there were many large, deep pits formed on the surface of bare AZ31 after 2 h of immersion in simulated body fluid (SBF). The IL coating (particularly when formed at 100 °C for 1 h) significantly suppressed the formation of these pits on the surface, making corrosion occur more uniformly. The P1,4,4,4 dpp IL film formed at 100 °C was more hydrophilic than the bare AZ31 surface, which was believed to be beneficial for avoiding the deposition of the proteins and cells on the surface and therefore improving the biocompatibility of AZ31 in blood. The interaction mechanism between this IL and AZ31 was also investigated using ATR-FTIR, which showed that both anion and cation of this IL were present in the film, and there was a chemical interaction between dpp(-) anion and the surface of AZ31 during the film formation.
authors.affiliation: Institute for Frontier Materials, Deakin University , Burwood, Victoria 3125, Australia.
authors.forename: Yafei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Maria
authors.initials: M
authors.lastname: Forsyth
authors.forename: Bruce R W
authors.initials: BR
authors.lastname: Hinton
mesh_terms: D020341:Absorbable Implants; D000497:Alloys / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D003343:Corrosion; D054855:Drug-Eluting Stents; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids; D008422:Materials Testing; D013499:Surface Properties
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D052578:Ionic Liquids; C586533:Mg-Al-Zn-Mn-Si-Cu alloy
keywords: Mg alloy; biodegradable stents; corrosion protection; hydrophilic surface; ionic liquid; morphology