Elsevier

Materials Letters

Volume 264, 1 April 2020, 127322
Materials Letters

Enhanced corrosion resistance and biocompatibility of magnesium alloy by hydroxyapatite/graphene oxide bilayer coating

https://doi.org/10.1016/j.matlet.2020.127322Get rights and content

Highlights

  • Hydroxyapatite/graphene oxide (HA/GO#) bilayer coating is prepared on AZ31 alloy via hydrothermal treatment and spin coating.

  • The presence of GO can effectively inhibit the formation and growth of cracks on HA layer.

  • HA/GO# coating shows enhanced corrosion resistance and biocompatibility.

Abstract

Fast degradation is the major limitation for biomedical application of Mg alloy. In the current work, a bilayer coating (HA/GO#) with hydroxyapatite as the inner layer and graphene oxide as the out layer was prepared on AZ31 alloy. Graphene oxide could sufficiently inhibit the formation and growth of corrosion cracks on hydroxyapatite layer, which result in its superior corrosion resistance. In vitro cell viability results suggested that MC3T3-E1 cells exhibited larger spreading area on HA/GO# coating at the initial 4 h of incubation. Furthermore, cells on HA/GO# coating showed superior proliferation rate. Considering its satisfied corrosion resistance and biocompatibility, the as prepared bilayer coating on AZ31 alloy is promising for clinical application.

Introduction

Ca-P coating is an effective modification method to improve the corrosion resistance of Mg alloys, especially at the initial stage of corrosion. However, large cracks would appear in Ca-P coating when contact with physiological environment, and thus destroying its corrosion protection effect [1]. Graphene oxide (GO) is widely studied for its fascinating properties, such as impermeable, which means GO can effectively avoid the attack of corrosive liquid. Furthermore, many literatures revealed that GO film is biocompatibility and could guide bone generation [2], [3], [4]. With all these considerations in mind, GO might be a good choice to inhibit the growth of cracks on Ca-P coating and might also be favor for the regeneration of bone tissue.

Here, we report a bilayer coating with hydroxyapatite (HA) as the inner layer and GO as the outer layer on AZ31 alloy (HA/GO#) to enhance its corrosion resistance and biocompatibility. Surface morphology, thickness and component of the prepared coating were characterized. Electrochemical test and immersion test were used to evaluate corrosion behaviors of HA/GO#. In vitro biocompatibility was studied by culturing MC3T3-E1 on the surface of HA/GO#.

Section snippets

Sample preparation and characterization

AZ31 alloy with diameters of 10 mm and thickness of 2 mm were used as substrates. 2.05 g Ca-EDTA and 0.68 g KH2(PO4)3 were dissolved in 50 mL ultrapure water, and pH value was adjusted to 9. AZ31 were placed in a Teflon-lined stainless, and then the above solution was poured into the Teflon liner. After kept at 90 °C for 12 h, the obtained samples were denoted as HA#. Subsequently, 200 μL commercial purchased GO (2 mg/mL) was dropped on the surface of HA# samples, and the spin coater worked at

Results and discussions

Surface views of various samples are displayed in Fig. 1a-c. After hydrothermal treatment, the surface was covered by many cauliflower-like structures (Fig. 1b) [5]. Further spinning coated with GO, the cauliflower-like structures remained (Fig. 1c), but was covered by a thin film. The cross-sectional view of HA# sample is showed in Fig. 1d, and corresponding detection of Mg, Ca, P elements are exhibited in Fig. 1e and f. It can be seen that Ca and P elements homogeneously distributed across

Conclusions

A bilayer coating with HA as the inner layer and GO as the outer layer was successfully formed on AZ31 alloy. The HA/GO# bilayer coating was proved to inhibit the growth of cracks on the coating with the impermeable property of GO, and thus resulted in its enhanced corrosion resistance. MC3T3-E1 cells showed superior adhesion, spreading and proliferation on HA/GO# sample. With improved corrosion resistance and biocompatibility, we expect that as prepared HA/GO# coating on Mg alloy is promising

CRediT authorship contribution statement

Feng Peng: Methodology, Data curation, Formal analysis, Investigation, Writing - original draft. Dongdong Zhang: Methodology, Data curation, Formal analysis, Investigation, Writing - original draft. Donghui Wang: Investigation, Validation, Methodology. Lidan Liu: Investigation, Validation, Methodology. Yu Zhang: Funding acquisition, Methodology, Project administration, Supervision, Writing - review & editing. Xuanyong Liu: Funding acquisition, Methodology, Project administration, Supervision,

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

Financial supported from the National Natural Science Foundation of China (31771044), Shanghai Committee of Science and Technology, China (18410760600) and International Partnership Program of Chinese Academy of Sciences Grant No.GJHZ1850.

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These authors contributed equally to this work.

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