ZnO nanostructures enhance the osteogenic capacity of SaOS-2 cells on acid-etched pure Ti

doi:10.1016/j.matlet.2017.12.055

Materials Letters

Volume 215, 15 March 2018, Pages 173-175

https://doi.org/10.1016/j.matlet.2017.12.055 Get rights and content

Highlights

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Flake-like ZnO nanostructures are prepared on Ti surface by hydrothermal treatment.
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ZnO nanoflakes whose spacings are less than 70 nm can enhance cell osteogenesis.
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The flake-like ZnO nanostructures show the potential to promote osseointegration.

Abstract

Zinc oxide (ZnO) has attracted a great deal of interest due to its electronic and optical properties, and has potential applications in biomedical field, while few studies have been conducted to investigate its biocompatibility. In this study, we prepared nanostructured ZnO on acid-etched pure Ti surface through a moderate hydrothermal treatment in ammonia solution (pH = 12.6). By changing Zn precursor concentration and hydrothermal duration, it was feasible to synthesis flake-like ZnO nanostructures with variable spacings. The adhesion, proliferation and alkaline phosphatase (ALP) activity of SaOS-2 cells were enhanced on the ZnO nanostructures when the Zn precursor concentration was 0.02 M and the hydrothermal duration was 4 h, compared to those on the acid-etched pure Ti without ZnO nanostructures. Narrower spacings (<70 nm) between ZnO nanostructures are considered to contribute to this enhancement. Together, the results indicate that the superposition of ZnO nanostructures on titanium surfaces may be beneficial for the enhanced biological performance.

Introduction

Zinc oxide (ZnO) nanostructures have attracted remarkable attention because of their unique properties and vast applications in microelectronic devices, biosensors as well as energy conversion and storage [1]. Besides, as an essential trace element for human body, Zn plays pivotal roles in diverse metabolic and cellular signalling pathway [2]. It inspires us to extend the applications of ZnO in bone regeneration. ZnO nanostructures with different morphologies can be synthesized via various methods. Rod-like ZnO nanostructures prepared by a combination of solution-based hydrothermal growth method and spin coating were reported to reduce the adhesion and viability of anchorage-dependent cells [3]. Flower-shaped ZnO nanostructures were reported to promote the adhesion, growth and differentiation of osteoblasts [4]. However, the synthesis process of ZnO nano-flowers was complex. In these previous studies, ZnO nanostructures with different morphologies exhibited different biological performances. Thus, it is necessary to develop ZnO nanostructures on Ti surfaces that can promote the osseointegration between implant and bone tissue. In this study, flake-like ZnO nanostructures were prepared through a moderate hydrothermal method on acid-etched pure Ti. The osteogenic capacity of SaOS-2 cells was used to evaluate the biological performances of flake-like ZnO nanostructures.

Section snippets

Materials and methods

Pure titanium discs (grade 2; diameter: 10 mm, thickness: 1 mm) were ground using 800-grit abrasive paper. Then the samples were treated in 48% concentrated sulfuric acid at 60 °C for 60 min. Subsequently, samples were put into teflon-lined autoclaves each containing 20 mL solvent Zn(CH₃COO)₂ ammonia solution (pH = 12.6). The autoclaves were maintained at 95 °C for different durations and then air cooled to room temperature.

Acid-etched pure Ti was referred as group Acid-etch; After a following

Results and discussion

Fig. 1 shows the morphology of various sample surfaces. Micropits were produced on Ti surface by acid-etching (Fig. 1a). While at higher magnification, nanostructures were not observed (Fig. 1a insert). After hydrothermal treatment, the formation of flake-like nanostructures was noticed on Ti surfaces (A-0.02M, A-0.002M, Fig. 1b,c). With the increase of Zn(CH₃COO)₂ concentration from 0.002 M to 0.02 M, the nanostructures were found to be more flake-like. At 1 h, there were only several dots

Conclusions

ZnO nanostructures with diverse morphologies were synthesized via moderate hydrothermal treatment on acid-etched pure Ti surface. Flake-like ZnO nanostructures showed the ability to enhance the proliferation and osteogenic capacity of SaOS-2 cells when the spacings between the ZnO nanoflakes were less than 70 nm. This study demonstrated that ZnO nanostructures on acid-etched Ti surface offer the potential to promote osseointegration.

Acknowledgements

The authors are grateful for the financial support from National Natural Science Foundation of China (U1605243), National Key Research and Development Program of China (2016YFC1100100).

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¹: These authors contributed equally to this work and should be considered co-first authors.

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