| In the present article, a systematic research was conducted on the electrochemical deposition of Magnesium-substituted/Strontium-substituted hydroxyapatite (Mg-HAp/Sr-HAp). By controlling various experimental parameters, the nanometer Mg-HAp/Sr-HAp coatings with different amount of Mg/Sr were deposited on the titanium surface. Homogeneous coatings were obtained by electrochemical method in electrolytes containing (Ca, Mg or Sr)Cl2·6H2O, NH4H2PO4 with (Ca+Mg)/P or (Ca+Sr)/P molar ratio being 1.67. The deposition process was conducted with the electrochemical analyzer (CHI 1140A) operated at 3.0 V at 85℃for 50 min in electrolytes with various molar ratio of Mg/(Ca+Mg) or Sr/(Ca+Sr). The crystal structure, the micro-morphologies, compositions and biocompatibility of Mg-HAp/Sr-HAp coatings were characterized with XRD, SEM, FT-IR, ICP-AES and MTT assay.The results suggested that the electrochemical deposition was a practical method for obtaining Mg-HAp coatings. In the present study, the (0-10 mol% ) Mg for Ca substituted HAp was deposited on the titanium substrate, which corresponds to 0-2 wt.% of Mg concentration in HAp crystals. With the increasing amount of Mg in the obtained coatings, the size of crystals became smaller. Mg2+ had the ability to inhibit the crystal growth of the HAp, especially in the (001) plane, and consequently decrease the crystallinity. The results of MTT assay showed that the proliferation of cells was not significantly influenced by Mg-substituted HAp coatings.The results also suggested that the electrochemical deposition was a practical method for obtaining Sr-HAp coatings. In the present study, the (0-100 mol% ) Sr for Ca substituted HAp was deposited on the titanium substrate. Due to the similarity of Ca2+ and Sr2+, Sr2+ does not inhibit the growth of crystal during the electrochemical deposition. The results of MTT assay showed that the proliferation of cells was not significantly influenced by Sr-substituted HAp coatings.
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