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Effect of Amino-, Methyl- and Epoxy-Silane Coupling as a Molecular Bridge for Formatting a Biomimetic Hydroxyapatite Coating on Titanium by Electrochemical Deposition

Tan Guoxin , Ouyang Kongyou , Wang Hang , Zhou Lei , Wang Xiaolan , Liu Yan , Zhang Lan , Ning Chengyun

材料科学技术（英文） doi:10.1016/j.jmst.2016.07.012

The objective of this study was to determine the role of functional groups of silane coupling on bioactive titanium (Ti) surface by electrochemical deposition, and calcium phosphate (CaP) coating, as well as bone cell adhesion and proliferation. Methyl group (—CH₃), amino group (—NH₂), and epoxy group (—glyph name—C(O)C) were introduced onto the bioactive Ti surface using self-assembled monolayers (SAMs) with different silane coupling agents as molecular bridges. The effect of the surface functional groups on the growth features of the CaP crystals was analyzed (including chemical compositions, element content, minerals morphology and crystal structure etc.). CH₃-terminated SAMs showed a hydrophobic surface and others were hydrophilic by contact angle measurement; NH₂-terminated SAMs showed a positive charge and others were negatively charged using zeta-potential measurement. Scanning electron microscopy results confirmed that flower-like structure coatings consisting of various pinpoint-like crystals were formatted by different functional groups of silane coupling, and the CaP coatings were multicrystalline consisting of hydroxyapatite (HA) and precursors. CaP coating of CH₃-terminated SAMs exhibited more excellent crystallization property as compared to coatings of —NH₂ and —C(O)C groups. In vitro MC3T3-E1 cells adhesion and proliferation were performed. The results showed that CaP coatings on silane coupling functionalized surfaces supported cell adhesion and proliferation. Thus, these functional groups of silane coupling on Ti can form homogeneous and oriented nano-CaP coatings and provide a more biocompatible surface for bone regeneration and biomedical applications.

关键词: Silane coupling , Molecular bridge , Calcium phosphate coatings , Titanium , Electrochemical deposition

Zn and Ag Co-doped Anti-microbial TiO₂ Coatings on Ti by Micro-arc Oxidation

Zhang Lan , Gao Qin , Han Yong

材料科学技术（英文） doi:10.1016/j.jmst.2016.01.008

Micro-porous TiO₂ coatings co-doped with Zn²⁺ and Ag nanoparticles were fabricated on Ti by micro-arc oxidation (MAO) for 0.5, 1.5, 2 and 4?min, respectively. The evolutions of morphology and phase component of the coating as a function of processing time were investigated. The microstructure of the 2?min treated coating was further observed by transmission electron microscopy to explore the coating formation mechanism. The amounts of Ag and Zn released from the 2?min treated coating were measured and the antibacterial properties of the coatings against Staphylococcus aureus (S.?aureus) were also investigated. The obtained results showed that with prolonged MAO time, the contents of Ag and Zn on the coating surfaces increased. All the coatings were micro-porous with pore diameters of 1-4?μm; however, some pores were blocked by deposits on the 4?min treated coating. The 2?min treated coating was composed of amorphous TiO₂, anatase, rutile, ZnO, Zn₂TiO₄ and homogenously distributed Ag nanoparticles. After immersion, Zn²⁺, Ag⁺, Ti²⁺ and Ca²⁺ were released from the coating and with the immersion time prolonged, the accumulated concentrations of these ions increased. After immersion for 36 weeks, the accumulated Zn²⁺ and Ag⁺ concentrations were 6.88 and 0.684?ppm, respectively, which are higher than the minimal inhibitory concentration but much lower than the cytotoxic concentration. Compared with polished Ti control, the coatings co-doped with Zn²⁺ and Ag nanoparticles significantly inhibited the adhesions of S.?aureus and reduced the amounts of planktonic bacteria in culture medium, indicating that the Zn and Ag co-doped TiO₂ could be a bio-adaptable coating for long-lasting anti-microbial performance.

关键词: Zn , Ag nanoparticle , Co-doped TiO2 , Micro-arc oxidation , Bio-adaptable

Formation and Bioactivity of SrTiO₃ Nanotubes on Titanium by Modified Anodization and Hydrothermal Treatment

Zhang Yanni , Han Yong , Zhang Lan

材料科学技术（英文） doi:10.1016/j.jmst.2016.06.007

SrTiO₃ nanotube films with good adhesion strengths to Ti substrates were fabricated by using a hybrid approach with a modified anodization and a hydrothermal treatment (HT). The effect of Sr²⁺ concentration in HT solutions on the morphologies and phase components of the nanotubes were investigated, the SrTiO₃ nanotubes formation mechanism was explored, and the adhesion strengths, hydrophilicity and apatite-forming ability of the SrTiO₃ nanotubes were also evaluated. The results demonstrated that with increasing the incorporation of Sr²⁺ into the nanotubes, no obvious changes of the lengths and outer diameters of the nanotubes were observed, but the wall thickness and the crystallinity of SrTiO₃ in the nanotubes increased. The accumulation of Sr at the inner tube wall indicated that the reaction of Sr²⁺ with TiO₂ mainly occurred in the vicinity of internal surfaces of the closely arranged nanotubes. The formation of the SrTiO₃ nanotubes could be attributed to an in situ dissolution-recrystallization process. The SrTiO₃ nanotubes exhibited good hydrophilicity and bioactivity, and the induced apatite preferred to nucleate on the nanotubes with higher crystallinity and Sr content, indicating a good bio-adaptability of the SrTiO₃ nanotubes for orthopedic application.