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Magnesium as well as its alloys appears increasingly as a revolutionary bio-metal for biodegradable implants application but the biggest challenges exist in its too fast bio-corrosion/degradation. Both corrosion-controllable and bio-compatible Mg-based bio-metal is highly desirable in clinic. In present work, hexamethylenediaminetetrakis (methylenephosphonic acid) [HDTMPA, (H2 O3 P-CH2 )2 -N-(CH2 )6 -N-(CH2 -PO3 H2 )2 ], as a natural and bioactive organic substance, was covalently immobilized and chelating-deposited onto Mg surface by means of chemical conversion process and dip-coating method, to fullfill dual-task performance of corrosion-protective and osteo-compatible functionalities. The chemical grafting of HDTMPA molecules, by participation of functional groups on pretreated Mg surface, ensured a firmly anchored base layer, and then sub-sequential chelating reactions of HDTMPA molecules guaranteed a homogenous and dense HDTMPA coating deposition on Mg substrate. Electrochemical corrosion and immersion degradation results reveal that the HDTMPA coated Mg provides a significantly better controlled bio-corrosion/degradation behavior in phosphate buffer saline solution as compared with untreated Mg from perspective of clinic requirement. Moreover, the HDTMPA coated Mg exhibits osteo-compatible in that it induces not only bioactivity of bone-like apatite precipitation but also promotes osteoblast cells adhesion and proliferation. Our well-controlled biodegradable and biocompatible HDTMPA modified Mg might bode well for next generation bone implant application., (© 2014 Wiley Periodicals, Inc.)

Biodegradable, a new revolutionary concept, is shaping the future design of biomedical implants that need to serve only as a temporary scaffold. Magnesium appears to be the most promising biodegradable metal, but challenges remain in its corrosion-controlling and uncertain biocompatibility. In this work, we employ chemical conversion and alternating dip-coating methods to anchor and deposit an Mg ion-integrated phytic acid (Mg-PA) coating on Mg, which is supposed to function both corrosion-controlling and osteo-compatible. It was ascertained that PA molecules were covalently immobilized on a chemically converted Mg(OH)2 base layer, and more PA molecules were deposited subsequently via chelating reactions with the help of additive Mg ions. The covalent immobilization and the Mg ion-supported chelating deposition contribute to a dense and homogeneous protective Mg-PA coating, which guarantees an improved corrosion resistance as well as a reduced degradation rate. Moreover, the Mg-PA coating performed osteo-compatible to promote not only bioactivity of bonelike apatite precipitation, but also induced osteoblast cells adhesion and proliferation. This is ascribed to its nature of PA molecule and the biocompatible Mg ion, both of which mimic partly the compositional structure of bone. Our magnesium ion-integrated PA-coated Mg might bode well for the future of biodegradable bone implant application.

Long-term corrosion profile of molybdenum was studied in three different simulated body fluids up to 28 days, compared with magnesium, zinc, and iron from the perspective of biodegradable metals (bio-metals). Their corrosion rate, mode, products and surface characteristics were comprehensively fathomed. Strikingly, Mo showed progressively advantageous long-term corrosion behavior with the smallest corrosion rate, and most importantly, more uniform mode, as compared with the other three bio-metals. It also performed bilaterally under the simulated inflammatory and bovine serum protein added conditions, with different corrosion progressions. These findings provide an optimistic outlook in opting molybdenum as a new type of bio-metal. [Display omitted] • Long-term corrosion profile of Mo as new type of bio-metal compared to Mg, Zn & Fe. • Mo exhibited lowest corrosion rate with more uniform mode vs. the other 3 bio-metals. • In inflammatory case, its corrosion accelerated albeit still uniform & palliated by BSA. • These findings help better-understand corrosion of Mo as bio-metal & optimistic outlooks. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Zn was compared with those of Fe and Mg in a long-term course of immersing in phosphate buffered saline (PBS) as biodegradable metal for bio-implants application. The comparison focused on corrosion rate, mode, products and surface characteristics along the immersion degradation up to 21 days. For transient assays, the open circuit potential and corrosion rate placed Zn between Fe and Mg. However, in a long-term course the corrosion rate of Zinc developed faster than Fe and Mg. This was ascribed to its unique localized corrosion and corrosion products changing in contrast to Fe and Mg. [ABSTRACT FROM AUTHOR]