Preparing Ca-P coating on biodegradable magnesium alloy by hydrothermal method: In vitro degradation behavior

Abstract

Magnesium alloys are potentially attractive biodegradable materials. However, their rapid corrosion rate limits their biomedical application. To slow down the rate of biodegradation, a protective calcium-phosphate coating was formed on a magnesium alloy substrate by a hydrothermal method. Scanning electron microscope results showed that the coating consisted of two layers with different crystalline characteristics. The loose outer layer showed a prism-like crystal structure, while the compact inner layer is a dense ultra-fine regular di-pyramid-like structure with an average grain dimension of ~200 nm. The compositions of the inner layer and outer layer were calcium-deficient hydroxyapatite (Ca-def HA) and dicalcium phosphate (DCPa), respectively. The coating adhered well to the substrate with a thickness of about 15 m. Immersion in Hank's solution indicated that the coating could significantly improve the degradation properties of magnesium alloy. The pH of the solution containing the coated samples increased much more slowly than the untreated control. After 8 d immersion, the uncoated sample had corroded seriously while the coated sample was much less corroded. The Ca/P atom ratio in both the layers of the coating increased and the coating was still protecting the substrate. The two layers of the coating corroded differently because of differences in solubility. The outer layer was more severely attacked and many holes were formed on the surface, the inner layer suffered less attack. In addition, a growth of precipitate on the inner layer was observed, indicating that surface bioactivity was improved by the coating. Thus, magnesium alloys coated with a Ca-P coating prepared by a hydrothermal method are promising candidate biodegradable biomaterials, and further investigation of in vivo degradation behavior is suggested. biomaterials, magnesium alloys, Ca-P coating, hydrothermal method, degradation, hydroxyapatite Citation:Li K K, Wang B, Yan B, et al. Preparing Ca-P coating on biodegradable magnesium alloy by hydrothermal method: In vitro degradation behavior. Chin

Surface modification of magnesium and its biodegradable alloys by calcium orthophosphate coatings to improve corrosion resistance and biocompatibility

“…According to the authors, the formation of highly crystalline coatings was achieved primarily due to using Ca-EDTA solutions, which could supply sufficiently high concentrations of Ca 2þ ions to perform precipitation. Similar results were obtained by other researchers Li et al, 2012b). Namely, in weak acidic (pH ¼ 5.9) solutions, a dual-layer structure was formed: an outer coarse layer consisted of plate-like OCP crystals and an inner dense layer consisted primarily of HA crystals.…”

“…Interestingly, the aforementioned biomimetic solutions HBSS Cui et al, 2013;Gan et al, 2013;Geng et al, 2009;Gruba c et al, 2013;Jo et al, 2013;Li et al, 2012aLi et al, , 2012bWang, Tan, et al, 2011;Wang et al, 2013;Waterman et al, 2011;Zhang et al, 2007 and SBF Choudhary, Raman, & Nie, 2012;Gao et al, 2011;Guan et al, 2012;Hahn et al, 2011;Jamesh et al, 2012;Jo et al, 2011;Johnson et al, 2013;Kang et al, 2013;Kannan, 2012Kannan, , 2013Kim et al, 2014;Li et al, 2012a;Liu et al, 2011bLiu et al, , 2014Meng et al, 2011;Noorakma et al, 2013;Pan, Chen, Wang, & Zhao, 2013;Shi, Qi, Chen, & Shi, 2011;Smith et al, 2012;Song et al, 2008Song et al, , 2010Song et al, , 2013Sreekanth & Rameshbabu, 2012;Wang et al, 2007Wang et al, , 2010Xu et al, 2012;Zhang, Dai, et al, 2012;Zhang, Li, et al, 2012;Zhang, Dai, et al, 2013;Zhang, Ma, et al, 2013;…”

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…The authors revealed that the protection level of CaPO 4 deposits could be varied by their crystal phase, microstructure and thickness. In addition, the deposits showed good adhesive properties with slight plastic deformations under cyclic stresses below the fatigue limit [491][492][493][494][495][496][497].…”

“…ACCEPTED MANUSCRIPT 39 Hydrothermal process was used to deposit CaPO 4 on both metallic [408,409,[487][488][489][490][491][492][493][494][495][496][497][498] and polymeric [499,500] substrates. Ones this technique was called as "a chemical bath method" [501].…”

In vitro and in vivo cytocompatibility evaluation of biodegradable magnesium-based stents: a review

“…At present, there are two methods to reduce the degradation rate and improve their mechanical properties. One is alloying with elements such as calcium, zinc, strontium, zirconium, rare earth elements, and aluminum [13,20,21], and another is surface modification [22][23][24]. Both in vitro and in vivo evaluations must be carried out to verify the feasibility of Mg-based stents before the application in human.…”