Β-glycerophosphate Disodium Research Articles

Protection of Cells in Physiological Oxygen Tensions against DNA Damage-induced Apoptosis

Oxygen availability has important effects on cell physiology. Although hyperoxic and hypoxic stresses have been well characterized, little is known about cellular functions in the oxygen levels commonly found in vivo. Here, we show that p53-dependent apoptosis in response to different DNA-damaging agents was reduced when normal and cancer cells were cultured at physiological oxygen tensions instead of the usual atmospheric levels. Different from what has been described in hypoxia, this was neither determined by decreases in p53 induction or its transactivation activity, nor by differences in the intracellular accumulation of reactive oxygen species. At these physiological oxygen levels, we found a constitutive activation of the ERK1/2 MAPK in all the models studied. Inhibition of this signaling pathway reversed the protective effect in some but not all cell lines. We conclude that a stress-independent constitutive activation of prosurvival pathways, including but probably not limited to MAPK, can protect cells in physiological oxygen tensions against genotoxic stress. Our results underscore the need of considering the impact of oxygen levels present in the tissue microenvironment when studying cell sensitivity to treatments such as chemotherapy and radiotherapy.

Formation of hydroxyapatite on low Young's modulus Ti–30Nb–1Fe–1Hf alloy via anodic oxidation and hydrothermal treatment

Hydroxyapatite (HA) on the Ti–30Nb–1Fe–1Hf alloy has been fabricated via anodic oxidation followed with the hydrothermal treatment. The anodic oxide film (AOF) containing Ca and P was formed by anodic oxidation in a solution consisting of β-glycerophosphate disodium pentahydrate(β-GP), and calcium acetate monohydrate(CA). The AOF was formed by a 2-stage growth: (1) a thin oxide film that intimately contacted the substrate formed prior to sparking; (2) after sparking, the thickness of AOF increased rapidly, accompanying with the formation of numerous craters in the AOF. When anodizing to 300 V, the AOF had a glassy amorphous structure. Increasing anodizing potential increased the Ca/P ratio and contents of Ca and P, but decreased the adhesion strength between the AOF and the substrate. After 6 h of hydrothermal treatment at 250 °C, a great number of crystalline HA precipitated on the surface of AOF anodized to 300 V. The shapes and population density of HA crystals can be controlled by modifying the anodizing potential and the solution pH of hydrothermal treatment. Increasing the pH of the solution in hydrothermal treatment enhanced the precipitation of HA crystals. Numerous needle-like HA crystals that nearly covered the surface of AOF were obtained when hydrothermally treated in the pH 13 solution.

Nanocrystallized SrHA/SrHA–SrTiO3/SrTiO3–TiO2 multilayer coatings formed by micro-arc oxidation for photocatalytic application

Novel photocatalytic coatings containing strontium hydroxyapatite (SrHA), strontium titanate(SrTiO3),and TiO2 were formed by micro-arc oxidation (MAO) in an aqueous electrolyte containing strontium acetateand β-glycerophosphate disodium at 530 V for 0.1–5 min. The structure evolution of the coatingswas investigated as a function of processing time, and the photocatalytic activity of thecoatings was evaluated by measuring the decomposition rate of methyl orangeunder ultraviolet irradiation. During the MAO processing of the coatings, it wasobserved that some granules appeared in the electrolyte adjacent to the anode andthey increased in amount as the processing time was prolonged. The obtainedresults show that the granules are amorphous and poorly crystallized SrHA withnegative charges. The coating prepared for 5 min presents a microporous structure ofSrHA/SrHA–SrTiO3/SrTiO3–TiO2 multilayers, in which the SrHA outermost layer and theSrHA–SrTiO3 intermediate layer are nanocrystallized. It is suggested that formation of thegranules, electro-migration of the granules onto the pre-formed layer, andcrystallization of the adhered granules are possible mechanisms for the formation of aSrHA/SrHA–SrTiO3/SrTiO3–TiO2 multilayer coating. This coating shows much higher photocatalytic decomposition efficiency relative to theMAO-formed TiO2 coating, and is expected to have an important photocatalytic application.

Formation mechanism of HA-based coatings by micro-arc oxidation

Hydroxyapatite (HA)-based coatings were prepared by micro-arc oxidation (MAO) in an aqueous electrolyte containing calcium acetate and β-glycerophosphate disodium at high applied voltage. The structure and evolution of phase components in the coatings as a function of duration time (1–20 min) were investigated. It was observed that some granules started to appear in the electrolyte adjacent to anode after MAO duration for about 5 min and become more in amount with prolonging duration time. The obtained results show that the coatings consist of HA- and TiO 2-based two layers, in which the HA-based outerlayer contains small amounts of α-TCP (α-Ca 3(PO 4) 2) and CaCO 3 while the TiO 2-based innerlayer contains CaTiO 3. The granules are negatively charged amorphous HA, TCP and CaCO 3. It is suggested that formation of the granules in the electrolyte adjacent to anode, electro-migration of the granules onto the pre-formed TiO 2-based layer and sintering-caused phase transformation of the adhered granules are possible mechanism for HA-based layer formation.

Preparation of porous anatase titania film

A porous anatase titania film was prepared by a composite oxidation method on pure titanium surfaces, which was in a combination of pre-anodic oxidation and micro-arc oxidation treatment. In the pre-anodic oxidation treatment, the sample was immersed in oxalic acid solution using a DC power supply. In micro-arc oxidation treatment, the sample was put into β-glycerophosphate di-sodium salt and calcium acetate electrolytic solution by using an asymmetry pulse power supply. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with EDS spectrum instrument were employed to characterize the phase, composition and microstructure of the film. A micro-hardness tester was employed to test the hardness of the formed film and a scratching machine to evaluate the bond strength of the film. XRD indicated that the film formed by pre-anodic oxidation was composed of a thin anatase film, which was uniform and even. While the film prepared by micro-arc oxidation treatment was porous and uneven, with a porous size of 1–3 μm. XRD showed that the porous film was also made up of anatase. The micro-hardness of the porous film was 645 HV 0.2 and the bond strength of the porous film 36.3 N. The formed film is expected to have significant applications as medical implants.

Biomimetic apatite coatings on micro-arc oxidized titania

Biomimetic apatite coatings on micro-arc oxidized titania films were investigated and their apatite-inducing ability was evaluated in a simulated body fluid (1.0SBF) as well as in a 1.5 times concentrated SBF (1.5SBF). Titania-based films on titanium were prepared by micro-arc oxidation at various applied voltages (250–500 V) in an electrolytic solution containing β-glycerophosphate disodium salt pentahydrate ( β-GP) and calcium acetate monohydrate (CA). Macro-porous, Ca- and P-containing titania-based films were formed on the titanium substrates. The phase, Ca and P content, morphology, and thickness of the films were strongly dependent on the applied voltage. In particular, Ca- and P-containing compounds such as CaTiO 3, β-Ca 2P 2O 7 and α-Ca 3(PO 4) 2 were produced at higher voltages (>450 V). When immersed in 1.0SBF, a carbonated hydroxyapatite was induced on the surfaces of the films oxidized at higher voltages (>450 V) after 28 days, which is closely related to the Ca- and P-containing phases. The use of 1.5SBF shortened the apatite induction time and apatite formation was confirmed even on the surface of the films oxidized at 350 V, which suggests that the incorporated Ca and P in the titania films play a similar role to the Ca- and P-containing compounds in the SBF.

Structure and in vitro bioactivity of titania-based films by micro-arc oxidation

Titania-based films on titanium were formed by micro-arc oxidation in electrolytic solutions containing sodium carbonate, sodium phosphate, acetate monohydrate and β-glycerophosphate disodium salt pentahydrate using a pulse power supply. The morphology, elemental composition and phase components of the films were investigated as a function of the electrolytes composition and the applied voltage (in the range of 200–500 V). In vitro bioactivity of the films was evaluated in a most commonly used simulated body fluid as proposed by Kokubo et al. The results showed that the films were porous with 1–8 μm pores and nano-crystallized, without apparent interface to the titanium substrates. The phase components of the films could be anatase, rutile, CaTiO 3, β-Ca 2P 2O 7 and α-Ca 3(PO 4) 2, strongly depending on the electrolytes composition and the applied voltage. The pore size and the content of Ca and P tended to increase with the applied voltage. Among the prepared titania-based films, only the film containing CaTiO 3, β-Ca 2P 2O 7 and α-Ca 3(PO 4) 2 could induce an apatite layer on its surface, exhibiting bioactivity. The bioactive response of the micro-arc oxidized films to the structural factors and the apatite-induced mechanism were discussed.