Enhancement of in vitro apatite-forming ability of thermally oxidized titanium surfaces by ultraviolet irradiation

Shozui, Tetsuya; Tsuru, Kanji; Hayakawa, Satoshi; Osaka, Akiyoshi

doi:10.2109/jcersj2.116.530

Cited by 18 publications

(8 citation statements)

References 18 publications

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“…It is highly possible that the reconstructed hydroxyl groups suggested by Sakai et al correspond to the strongly bonded hydroxyl groups, including Ti−OH groups, in our XPS results, which are closely related to the number of DACs. This inference is consistent with many previous reports that electron−hole pairs are generated along with numerous Ti− OH groups on the TiO 2 surface, as follows 2,21,31 (2)…”

Section: ■ Results and Discussionsupporting

confidence: 93%

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism

2021

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TiO2 films generally undergo contact angle relaxation in the dark. It has been suggested that carbon contamination and the loss of surface OH generated by UV may be the major causes. However, the mechanisms for the long-lasting hydrophilicity have not been fully understood. Here, we studied contact angle relaxation of amorphous, mixed-phase, and anatase, and a new mechanism is proposed. After UV exposure and oxygen plasma treatment, the films’ relaxation was observed over short-term (1 day) and long-term (>30 days) scales with XPS analysis using two quantitative parameters: relative amount and binding energy (B.E.) shifting. One day after plasma treatment, we observed that the donor–acceptor complex (DAC) and Ti–OH peaks of anatase shifted toward lower B.E., while the other films showed no shift or positive B.E. shifting. Interestingly, the relaxation of the amorphous and mixed-phase TiO2 occurred over time despite the large number of total OH groups (I OH/I bulk > 75%) and DAC (I DAC/I bulk > 110%), and only the anatase film showed superhydrophilicity (∼10°) for 90 days. Also, the B.E. of all OH peaks increased over time, indicating that polarizable hydroxyls relaxed in the dark. Although the greater binding strength of Ti–OH and DAC on the anatase surface maintains long-lasting hydrophilicity, the loss of polarizable OH causes relaxation on the less-reactive TiO2 films. Carbon contamination can also contribute to the relaxation over time. Taken together, we conclude that the surface energy, polarizable OH, and contaminants are the major factors affecting relaxation; this study gives a full picture of the mechanism integrated over some of the previously reported models.

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Section: ■ Results and Discussionsupporting

confidence: 93%

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism

2021

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“…O vacancies are reported to favor apatite formation on various titania surfaces; for example, when an anatase or rutile surface is irradiated by UV light, a mixed surface of Ti 4+ and Ti 3+ with O vacancies is created by reduction, which improves apatite formation in SBF. [18][19][20] This is because the O vacancies that are created with Ti 3+ react with the surrounding water First-principle calculations suggest that the coexistence of O and Ti vacancies in Ti 2 O 3 crystals causes vacancy formation to be energy-negative and therefore thermodynamically stable. 22 Cations such as Ca 2+ are considered to be easily adsorbed on negatively charged Ti vacancies.…”

Section: Discussionmentioning

confidence: 99%

Relationship between valence of titania and apatite mineralization behavior in simulated body environment

Miyazaki

Akaike

2021

J. Am. Ceram. Soc.

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Titania-based materials are attractive for hard tissue repair due to their bone-bonding ability induced by apatite formation in the body environment. Various surface treatments have therefore been developed to produce a hydrated titania layer on Ti and its alloys. Titania takes various valences, such as TiO (Ti 2+ ) and Ti 2 O 3 (Ti 3+ ), as well as typical TiO 2 (Ti 4+ ); however, there is no comprehensive study of structural effects on the apatite-forming ability of these titanias. In this study, we investigated apatite formation on titania powders with various valences in simulated body fluid. Anataseand rutile-type TiO 2 formed apatite in simulated body fluid within 7 days, but TiO and Ti 2 O 3 did not. In contrast, when the titania powders were treated with NaOH solution, the surface converted to tetravalent titania and all samples formed apatite.It is proposed that the surface electrical states of TiO and Ti 2 O 3 are strongly affected by their bulk conductivity and that these behaved like pure Ti metal, which has poor apatite-forming ability. Apatite formation was favorable when the titania had a high absolute value and exhibited high fluctuations of zeta potential during initial stages in simulated body fluid, owing to adsorption of large amounts of Ca 2+ and HPO 4 2− . K E Y W O R D Sapatite, bioactivity, calcium phosphate, titanium oxide | MATERIALS AND METHODS | SpecimensDivalent TiO, trivalent Ti 2 O 3 (Kojundo Chemical Lab. Co., Ltd., Japan), tetravalent anatase-type TiO 2 (MC-50, average primary particle size: 24 nm; Ishihara Sangyo Kaisha Ltd., Japan, and FUJIFILM Wako Pure Chemical Co., Japan), and rutile-type TiO 2 (FUJIFILM Wako Pure Chemical Co.) were used. The particle sizes of TiO and Ti 2 O 3 were relatively large (around 1-5 mm), so these reagents were ground in a mortar for 7 minutes prior to use.

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“…UV light irradiation has also been applied to assisting apatite formation on titanium [18][19][20][21][22]. Shozui [18] used heat-treated titanium pieces treated with UV light irradiation as the object. He found UV irradiation enhances apatite formation on titanium after an immersion of the titanium in Kokubo's simulated body fluid (SBF).…”

Section: Introductionmentioning

confidence: 99%

Surface Deposition on Titania in a Physiological Solution with Ultraviolet Irradiation In Situ and Effect of Heat Treatment

Zhou

Zou

2019

Coatings

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Photocatalysis-enhanced surface deposition on titanium surfaces for biomedical applications is investigated in this work. Immersion tests of commercially pure titanium (CP-Ti) pieces in a simulated body fluid adding bovine serum albumin (BSA) under ultraviolet (UV) irradiation in situ are carried out. The morphologies of deposition are characterized by SEM and stereo imaging microscopy, and the quantity and composition of the deposition is examined by SEM, energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy. The results show a deposition layer with thickness 89 µm is produced on 600 • C heat-treated specimens. An irradiation pattern of lighting/dark repeated results in more deposition on heat-treated CP-Ti. It is confirmed that a mixture of anatase and rutile phases generated on 600 • C heat-treated specimens has enhanced photocatalysis. The decomposition of BSA by photocatalysis, a possible product of nitrite also results in enhanced deposition on Ti. EDS analysis shows large reduction of carbon in the deposition on UV-light exposed surfaces compared to no UV-light-exposed surfaces. Furthermore, C-H bond decreases and C-C, Ca-O, and P-O bond increases are found on photoactivated surfaces. The deposition produced by this method is expected to be useful for applications to biomaterials with high bioactivity.

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Enhancement of in vitro apatite-forming ability of thermally oxidized titanium surfaces by ultraviolet irradiation

Cited by 18 publications

References 18 publications

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism

Relationship between valence of titania and apatite mineralization behavior in simulated body environment

Surface Deposition on Titania in a Physiological Solution with Ultraviolet Irradiation In Situ and Effect of Heat Treatment

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Enhancement of in vitro apatite-forming ability of thermally oxidized titanium surfaces by ultraviolet irradiation

Cited by 18 publications

References 18 publications

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO2 Films and Its Mechanism

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO2 Films and Its Mechanism

Relationship between valence of titania and apatite mineralization behavior in simulated body environment

Surface Deposition on Titania in a Physiological Solution with Ultraviolet Irradiation In Situ and Effect of Heat Treatment

Contact Info

Product

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Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO₂ Films and Its Mechanism