Effects of Micro-Arc Oxidation Discharge Parameters on Formation and Biomedical Properties of Hydroxyapatite-Containing Flower-like Structure Coatings

Kuan-Ting Chen; Jun-Wei Huang; Wei-Ting Lin; Tsung-Yuan Kuo; Chi-Sheng Chien; Ching-Ping Chang; Yung-Ding Lin

doi:10.3390/ma16010057

Effects of Micro-Arc Oxidation Discharge Parameters on Formation and Biomedical Properties of Hydroxyapatite-Containing Flower-like Structure Coatings

Materials (Basel). 2022 Dec 21;16(1):57. doi: 10.3390/ma16010057.

Authors

Kuan-Ting Chen¹, Jun-Wei Huang², Wei-Ting Lin^{1

2}, Tsung-Yuan Kuo², Chi-Sheng Chien¹, Ching-Ping Chang³, Yung-Ding Lin⁴

Affiliations

¹ Department of Orthopaedics, Chi Mei Medical Center, No. 901, Zhonghua Rd., Yongkang District, Tainan 710, Taiwan.
² Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, 1 Nan-Tai St., Tainan 710, Taiwan.
³ Department of Medical Research, Chi Mei Medical Center, No. 901, Zhonghua Rd., Yongkang District, Tainan City 710, Taiwan.
⁴ School of Intelligent Engineering, Shaoguan University, Shaoguan 512005, China.

Abstract

The micro-arc oxidation (MAO) process was used to prepare hydroxyapatite-containing flower-like structure coatings on commercially pure titanium substrates with various values of the applied voltage (330, 390, 450 V), applied current (0.4, 0.5, 0.6 A), and duration time (1, 3, 5 min). It was found that the surface morphology of the coatings was determined primarily by the applied voltage. A voltage of 330 V yielded a flower-like/plate-like structure, while voltages of 390 V and 450 V produced a flower-like structure and a porous morphology, respectively. The applied current and duration time mainly affected the coating formation speed and petal size of the flower-like structures, respectively. The coatings prepared using voltages of 330 V and 390 V (0.6 A, 5 min) both contained Ti, TiO₂-A (anatase), TiO₂-R (rutile), DCPD (CaHPO₄·2H₂O, calcium hydrogen phosphate), and hydroxyapatite (HA). However, the latter coating contained less DCPD and had a higher HA/DCPD ratio and a Ca/P ratio closer to the ideal value of HA. The coating prepared with a voltage of 450 V consisted mainly of Ti, TiO₂-A, TiO₂-R, and CaTiO₃. For the coatings prepared with a voltage of 390 V, the flower-like structures consisted mainly of HA-containing compounds. DCPD plate-like structures were observed either between the HA-containing flower-like structures (330 V samples) or within the flower-like structures themselves (390 V samples). The coating surfaces with flower-like/plate-like or flower-like structures had a greater roughness, which increased their hydrophilicity and resulted in superior bioactivity (SBF immersion) and biocompatibility (MG-63 cell culture). The optimal biomedical performance was found in the 390 V coating due to its flower-like structure and high HA/DCPD ratio.

Keywords: bioactivity; biocompatibility; flower-like structure; hydroxyapatite; micro-arc oxidation.

Grants and funding

This research was funded by [Ministry of Science and Technology of the Republic of China (Taiwan)] grant number [MOST 109-2622-E-218-007] and by [Chi Mei Medical Center, Republic of China (Taiwan)] grant number [13001090061]. And the APC was funded by [Ministry of Science and Technology of the Republic of China (Taiwan)] grant number [MOST 111-2218-E-006-016].