Enhanced bonding of biomimetic apatite coatings on surface-modified titanium substrates by hydrothermal pretreatment

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

“…Therefore, shape and sizes of the grains with intimate contact with the substrate were found to affect the adhesion of HA deposits and the hexagonal grains with enlarged sizes (e.g., up to 250 nm in side length) deteriorated the adhesion, while the granular nano-sized grains enhanced the bonding of the deposits through improving the interlocking by the substrate [207]. Furthermore, the adhesion strength was found to be a linear function of the average surface roughness [770]; thus, highly roughened substrate surfaces exhibited higher bond strength as compared to smooth substrate surfaces [330,771]. Specifically, the adhesion forces of CaPO 4 deposits should be high enough to maintain their bioactivity after a surgical implantation.…”

“…For example, if CaPO 4 needs to be biomimetically deposited on titanium or its alloys, a surface layer of titanium oxides, hydroxides and/or titanates should be created prior the deposition [323]. This can be done by various oxidation techniques, such as heat [324] or alkali [49,128,325,326] treatments, oxidation in H 2 O 2 [128,326], micro-arc oxidation [327], precalcification in boiling Ca(OH) 2 solution [328,329] or under the hydrothermal conditions [330], as well as by water vapor treatment [331]. Similar is valid for other chemically inert metals: prior biomimetic deposition of CaPO 4 , a surface layer of hydrated zirconium hydroxides, niobium hydroxides, tantalum hydroxides or their Na-or K-containing salts should be created on the surface of Zr, Nb and Ta, respectively [332,333].…”

“…TiO 2 [789,790] and TiN [229] were also used as under-layers for RF magnetron sputtering. Similarly, formation of intermediate layers of hydrated titanium oxides on Ti [323,330,429] or polar hydrophilic groups on polymers [51,53,60,[69][70][71] is required to improve the adhesion of wet deposited CaPO 4 . Namely, the adhesive strength of the deposited apatite was increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa and from 0.6 to 5.3…”

Review of the biocompatibility of micro-arc oxidation coated titanium alloys

“…The deposition of apatite coatings upon socking in biological fluids depends on many aspects, including roughness, morphology (porosity, size of lamellas) and crystallinity [40]. The enhancement of the kinetics of apatite nucleation on coating surface in biological fluids is significantly related to the interactions.…”

Biomimetic Hydroxyapatite Formation on Titanium Surface in Simulated Body Fluids of Different Chemical Composition

“…Therefore, great attention h a s b e e n p a i d t o g i v e t h e m e t a l s u b s t r a t e s a capability to induce HA formation by attaching functional groups onto their surfaces [8]. It was shown that the process of HA formation occurred on negatively charged surfaces that contained, for instance, -OH or -COOH groups [9].…”