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Biodegradable magnesium alloys are advantageous in various implant applications, as they reduce the risks associated with permanent metallic implants. However, a rapid corrosion rate is usually a hindrance in biomedical applications. Here we report a facile two step procedure to introduce multifunctional, anticorrosive coatings on Mg alloys, such as AZ31. The first step involves treating the NaOH-activated Mg with bistriethoxysilylethane to immobilize a layer of densely crosslinked silane coating with good corrosion resistance; the second step is to impart amine functionality to the surface by treating the modified Mg with 3-amino-propyltrimethoxysilane. We characterized the two-layer anticorrosive coating of Mg alloy AZ31 by Fourier transform infrared spectroscopy, static contact angle measurement and optical profilometry, potentiodynamic polarization and AC impedance measurements. Furthermore, heparin was covalently conjugated onto the silane-treated AZ31 to render the coating haemocompatible, as demonstrated by reduced platelet adhesion on the heparinized surface. The method reported here is also applicable to the preparation of other types of biofunctional, anti-corrosive coatings and thus of significant interest in biodegradable implant applications.Keywords coatings, magnesium, alloys, corrosive, biofunctionalized, silane, anti Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsLiu, X., Yue, Z., Romeo, T., Weber, J., Scheuermann, T., Moulton, S. & Wallace, G. (2013). Biofunctionalized anti-corrosive silane coatings for magnesium alloys. Acta Biomaterialia, 9 (10), 8671-8677. AuthorsXiao Liu, Zhilian Yue, Tony Romeo, Jan Weber, Torsten Scheuermann, Simon E. Moulton, and Gordon G. Wallace AbstractBiodegradable magnesium (Mg) alloys are advantageous in various implant applications, as they reduce the risks associated with permanent metallic implants. However, the fast corrosion rate is usually a hindrance in biomedical applications. Here we report a facile twostep procedure to introduce multifunctional, anticorrosive coatings on Mg alloys, such as AZ31. The first step involves treating the NaOH-activated Mg with bistriethoxysilylethane (BTSE) to immobilise a layer of densely crosslinked silane coating with good corrosion resistance; the second step is to impart amine functionality to the surface by treating the modified Mg with 3-amino-propyltrimethoxysilane (γ-APS). We characterised the two-layer anticorrosive coating of AZ31 Mg alloy by Fourier transform infrared spectroscopy, static contact angle measurement and optical profilometry, potentiodynamic polarization and AC impedance measurements. Furthermore, heparin was covalently conjugated onto the silane treated AZ31 to render the coating haemocompatible, as demonstrated by reduced platelet adhesion on the heparinised surface. The method reported here is also applicable to the preparation of other types of biofunctional, anticorrosive coatings, and thus of significant interest in biodegradable implant applications.

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Different modes of scanning electrochemical mapping (SECM) such as surface generation/tip collection (SG/TC), amperometry, AC-SECM and potentiometry were employed to characterize the active/passive domains, hydrogen gas (H2) evolution and local pH on a corroding surface of AZ31 in simulated biological fluid (SBF). It was found that the main domains of H2 evolution are associated with lower insulating properties of the surface as well as higher local pH. The near surface pH was found to be highly alkaline indicating that, even in a buffered solution such as SBF, the local pH on a corroding AZ31 surface can be significantly different to the bulk pH. AbstractDifferent modes of scanning electrochemical mapping (SECM) such as surface generation/tip collection (SG/TC), amperometry, AC-SECM and potentiometry were employed to characterise the active/passive domains, hydrogen gas (H 2 ) evolution and local pH on a corroding surface of AZ31 in simulated biological fluid (SBF). It was found that the main domains of H 2 evolution are associated with lower insulating properties of the surface as well as higher local pH. The near surface pH was found to be highly alkaline indicating that, even in a buffered solution such as SBF, the local pH on a corroding AZ31 surface can be significantly different to the bulk pH.

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A carbon microfiber electrode coated with an electrodeposited cobalt chelate of a tetra-N-methylpyridoporphyrazinocobalt derivative has been used for the potentiometric detection of ascorbic acid. It is effective over a fairly wide range of ascorbic acid concentration and may have value for in vivo analysis.