A TiO 2 nanofilm was prepared on the surface of AZ31 magnesium alloy with controllable thickness through atomic layer deposition (ALD) technique, which can adjust the corrosion behaviors of AZ31 Mg alloy. Compared with the untreated Mg alloys, corrosion current densities ( i corr ) can decline by 58% in the 200-cycles TiO 2 -covered Mg alloy and further decline by up to 74% with the thickness of nanofilm up to 63 nm (400 cycles). The subsequent modification with a cross-linked conversion layer of 3-amino-propyltriethoxysilane (APTES) by a dipping method can produce a compact silane coating on TiO 2 nanofilm, which can seal pinholes of TiO 2 nanofilm and serve as a barrier to further adjust the corrosion behavior of the substrate. The i corr can decline about two orders of magnitude in the TiO 2 /silane composite coating. Making the adjustable corrosion rate come true, which can be attributed to the precise control on the thickness of metal oxide nanofilm and additional protection from the compact silane coating. In vitro study discloses that the TiO 2 /silane hybrid coating shows higher expression of alkaline phosphatase (ALP) and can promote cellular adhesion and proliferation with better cytocompatibility than untreated Mg alloy.
Bo Zhang,Ruijuan Yao,Manfred F. Maitz,Genwen Mao,Zhe Hou,Hongchi Yu,Rifang Luo,Yunbing Wang
Controlled corrosion and proper biological response are key demands for biodegradable Mg-alloy based vascular stents. To achieve those properties, herein, a chemical conversion coating was fabricated through layer-by-layer (LBL) assembly via the sequential assembly of poly (dimethyl-diallyl ammonium chloride) (PDDA), epigallocatechin gallate (EGCG) and heparin (Hep). Each component in the coating played a unique role, in which EGCG chelates Mg ions and enhances the stability of the coating by introducing multiple intermolecular interactions, while PDDA effectively enhances the resistance against chloride corrosion, and Hep provides adequate hemocompatibility and promotes endothelialization. Electrochemical assay and immersion test demonstrated that the synergistic combination of PDDA and EGCG effectively suppressed the corrosion rate. A systematic in vitro and ex-vivo evaluation demonstrated an impressive antithrombotic performance, along with a selective promotion of endothelial cells (ECs) proliferation and inhibition of smooth muscle cells (SMCs) growth and macrophages (MAs) activation. More importantly, subcutaneous implantation and implantation in the abdominal aorta wall indicated that the PDDA/EGCG/Hep-modified implants displayed good corrosion resistance and mild tissue response, enhanced endothelialization and suppressed intima hyperplasia. These promising outcomes revealed the clinical potential of the PDDA/EGCG/Hep coating on AZ31 as biodegradable cardiovascular implants.
危险品化学品经营许可证（带存储）