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Heparin (Hep) or bivalirudin (BVLD) were immobilized in an organic phytic acid (PA) coating on Mg by an in situ chemical route. Such a drug-loaded PA coating was designed to enhance both corrosion control and biocompatibility. It was found that both Hep- and BVLD-loaded PA coatings exhibited a dual role in effectively controlling corrosion as well as providing a biofunctional effect. Experiments involving electrochemical corrosion and in vitro degradation by immersion revealed that PA&Hep- and PA&BVLD-coated Mg had the same effect or even slower corrosion/degradation in phosphate buffered saline compared to PA-coated Mg, and it degraded significantly slower than untreated Mg. Moreover, Hep- or BVLD-loaded PA coatings showed relatively good hemocompatibility, with a prolonged clotting time, inhibited platelets adhesion as well as reduced hemolysis compared to untreated Mg. In addition, both PA&Hep and PA&BVLD coatings promoted endothelial cells growth and restrained the proliferation of smooth muscle cells. In vivo assays indicated that PA&Hep-coated Mg exhibited a significant difference in mass loss compared to untreated Mg, as well as better histocompatibility than other samples. These results demonstrate that our coating strategy shows a great potential in surface modification of biodegradable Mg. Finally, the mechanism for the incorporation of the drugs into the PA coating is discussed from both theoretical and practical perspectives. [ABSTRACT FROM AUTHOR]

ABSTRACT 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, (H2O3P−CH2)2−N−(CH2)6−N−(CH2−PO3H2)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. J Biomed Mater Res Part A: 103A: 1640-1652, 2015. [ABSTRACT FROM AUTHOR]