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In this study, we develop hydroxyapatite coatings that consist of micrometric hexagonal crystals grown on the Ti/TiO2 substrate. The coatings are synthesized by a hydrothermal method. The advance of our hydrothermal approach lies in the concomitant use of two reagents: ethylenediamine tetraacetic acid and monoethanolamine. The phase identification, surface morphology, and elemental composition of structures are examined by x-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. We also assess the in vitro bioactivity of hydroxyapatite structure and uncoated materials after incubation in the SBF solution. Simultaneously, we conduct a series of experiments to investigate electrochemical properties of titanium with and without hydroxyapatite by the means of electrochemical impedance and potentiodynamic polarization experiments in the Ringer's solution. Our results show that monoethanolamine-assisted hydrothermal method is an efficient and promising approach to obtain hydroxyapatite coatings with excellent crystal quality and Ca/P ratio close to the stoichiometric value of the Ca10(PO4)6(OH)2 phase. The SBF immersion tests indicate high bioactivity of hydroxyapatite coating after 7 days of incubation. However, the hydroxyapatite coating does not improve the corrosion behavior of the metallic titanium substrate. Electrochemical studies of all structures show the highest corrosion resistance for the Ti/TiO2 surface as compared to other samples. The lowest value of corrosion current density (jcor = 0.65 ± 0.19 nA cm−2) is found for the Ti/TiO2 surface. This result could be attributed to the porous morphology of the hydroxyapatite layer which could favor direct flow of electrolyte between the corrosive medium and the titanium substrate or to the adverse effect of hydrothermal synthesis on the barrier properties of the TiO2 intermediate layer.

Development of functional coatings for artificial bone implants that strengthen the osseointegration and accelerate bone healing processes is urgently needed in the biomedical field. In this study we present biological effect of novel composite coatings with different concentration of silica nanoparticles within crystalline hydroxyapatite matrix (HAp-SiO2) synthesized on titanium under hydrothermal conditions. Samples were analyzed for their elemental composition, structure, bioactivity and in vitro cytotoxicity. The results indicate the formation and homogeneous distribution of silica nanoparticles on the surface of hexagonal hydroxyapatite (HAp) crystals. The coatings show improved bioactivity in comparison with pure HAp after 4 days of immersion in simulated body fluid (SBF). The responses of human osteoblast-like cells (MG-63) cultured onto the synthesized materials provide evidence that HAp-SiO2 composites exhibit good biocompatibility. We propose that this is because HAp-SiO2 composites favor biomineralization process with cell proliferation remaining unaffected, regardless of the amount of silica. Furthermore, SEM and fluorescence measurements demonstrate that HAp-SiO2 had positive effect on cell morphology, favoring cell adhesion.

Nanotechnology is a very attractive tool for tailoring the surface of an orthopedic implant to optimize its interaction with the biological environment. Nanostructured interfaces are promising, especially for orthopedic applications. They can not only improve osseointegration between the implant and the living bone but also may be used as drug delivery platforms. The nanoporous structure can be used as a drug carrier to the surrounding tissue, with the intention to accelerate tissue–implant integration as well as to reduce and treat bacterial infections occurring after implantation. Titanium oxide nanotubes are promising for such applications; however, their brittle nature could be a significantly limiting factor. In this work, we modified the topography of commercially used titanium foil by the anodization process and hydrothermal treatment. As a result, we obtained a crystalline nanoporous u-shaped structure (US) of anodized titanium oxide with improved resistance to scratch compared to TiO2 nanotubes. The US titanium substrate was successfully modified with hydroxyapatite coating and investigated for bioactivity. Results showed high bioactivity in simulated body fluid (SBF) after two weeks of incubation.

Calcium phosphates offer outstanding biological adaptability. Thanks to their specific physico-chemical properties they are one of the most widely used materials in bone tissue engineering applications. The search for an innovative and economic strategy of synthesizing their different forms has been drawing considerable attention in the field. Herein, we report on a facile hydrothermal process in the presence of ethylenediamine tetraacetic acid and monoethanolamine to obtain various forms of calcium phosphates. The monoethanolamine served as an alkaline source and crystal growth modifier, while ethylenediamine tetraacetic acid was used to control the Ca2+ supersaturation level under high temperature and high pressure conditions. The obtained inorganic compounds were examined for their elemental composition, morphology, and structure using scanning electron microscopy, Raman spectroscopy, and powder x-ray diffraction. We were able to selectively synthesize monetite plate-like microcrystals as well as hydroxyapatite plates and nanofibers by simply varying the concentration of monoethanolamine.

Hydroxyapatite coatings were successfully produced on modified titanium substrates via hydrothermal synthesis in a Ca(EDTA) 2 − and (NH 4 ) 2 HPO 4 solution. The morphology of modified titanium substrates as well as hydroxyapatite coatings was studied using scanning electron microcopy and phase identification by X-ray diffraction, and Raman and FTIR spectroscopy. The results show that the nucleation and growth of hydroxyapatite needle-like crystals with hexagonal symmetry occurred only on titanium substrates both chemically and thermally treated. No hydroxyapatite phase was detected on only acid etched Ti metal. This finding demonstrates that only a particular titanium surface treatment can effectively induce the apatite nucleation under hydrothermal conditions.