pH Value Of Simulated Body Fluid Research Articles

3D gel-printing of porous MgFe2O4 magnetic scaffolds for bone tissue engineering

It is increasing evidence that the synergistic effects of magnetic scaffolds and magnetic fields can accelerate bone repairing and regeneration, and the bone tumor may be treated using magnetite nanoparticles (MNPs) with hyperthermia. In this study, in order to apply the magnetocaloric performance of MgFe2O4 to bone tissue engineering, porous MgFe2O4 magnetic scaffolds were successfully prepared by chemical coprecipitation method and 3D gel-printing (3DGP) technology. The printing slurry based on polyvinyl alcohol (PVA) system exhibited shear thinning properties, and its maximum solid loading was about 63 wt%. When the slurry was squeezed out of the needle, the slurry viscosity was 0.58 Pa·s at the shear rate of 316.3 s-1. The scaffolds sintered above 1100 °C were superparamagnetic and their compressive strength was within 1.8–12.51MPa, which is suitable for human cancellous bone. The highest saturation magnetization of porous MgFe2O4 scaffolds printed by 3DGP was 10.63 emu/g when they were sintered at 1200 °C. The weight loss rate of the scaffolds was 2.15% after degradation in simulated body fluid (SBF) for 5 weeks, pH value of SBF was between 6.78 and 7.4. Preliminary biological experiment shows that MC3T3-E1 cells had good adhesion and proliferation on MgFe2O4 scaffolds surface, and MgFe2O4 scaffolds can promote alkaline phosphatase (ALP) activation, which explain that porous MgFe2O4 magnetic scaffolds may be used for bone repairing.

Mechanical and in vitro biological performance of graphene nanoplatelets reinforced calcium silicate composite.

Calcium silicate (CaSiO3, CS) ceramic composites reinforced with graphene nanoplatelets (GNP) were prepared using hot isostatic pressing (HIP) at 1150°C. Quantitative microstructural analysis suggests that GNP play a role in grain size and is responsible for the improved densification. Raman spectroscopy and scanning electron microscopy showed that GNP survived the harsh processing conditions of the selected HIP processing parameters. The uniform distribution of 1 wt.% GNP in the CS matrix, high densification and fine CS grain size help to improve the fracture toughness by ∼130%, hardness by ∼30% and brittleness index by ∼40% as compared to the CS matrix without GNP. The toughening mechanisms, such as crack bridging, pull-out, branching and deflection induced by GNP are observed and discussed. The GNP/CS composites exhibit good apatite-forming ability in the simulated body fluid (SBF). Our results indicate that the addition of GNP decreased pH value in SBF. Effect of addition of GNP on early adhesion and proliferation of human osteoblast cells (hFOB) was measured in vitro. The GNP/CS composites showed good biocompatibility and promoted cell viability and cell proliferation. The results indicated that the cell viability and proliferation are affected by time and concentration of GNP in the CS matrix.

Evaluation of biomechanical strength, stability, bioactivity, and in vivo biocompatibility of a novel calcium deficient hydroxyapatite/poly(amino acid) composite cervical vertebra cage

A new type of cervical vertebra cage was prepared using a novel composite, calcium deficient hydroxyapatite/poly(amino acid) (HA/PAA), and its mechanical properties, in vitro stability and bioactivity, and in vivo biocompatibility were characterized. The results showed that the axial compressive loads of the HA/PAA cage were in the range of 10058–10612 N and the lateral compressive loads were in the range of 1180–2363 N, and varied with the height of the cervical vertebra cages. After immersion in simulated body fluid (SBF) for 16 weeks, the axial compressive loads of the cage decreased from 10058 to 7131 N and the lateral compressive loads decreased from 1180 to 479 N. In addition, the weight loss decreased 6.01%, showing that HA/PAA composites had good stability during the incubation period. The pH value of SBF was also monitored during the whole soaking period; it fluctuated in the range of 6.9–7.4. Scanning electron microscope and energy dispersive spectrometer results showed the cage was bioactive with a new apatite layer attached on the surface. The histological evaluation revealed that new bone tissue bonded tightly with the surfaces of the implants, showing excellent biocompatibility. In conclusion, the HA/PAA cage showed sufficient strength, good stability, bioactivity, and biocompatibility, and has potential applications for clinical cervical vertebrae repair.

Bone-like apatite formation on HA/316L stainless steel composite surface in simulated body fluid

HA/316L stainless steel(316L SS) biocomposites were prepared by hot-pressing technique. The formation of bone-like apatite on the biocomposite surfaces in simulated body fluid(SBF) was analyzed by digital pH meter, plasma emission spectrometer, scanning electron microscope(SEM) and energy dispersive X-ray energy spectrometer(EDX). The results indicate that the pH value in SBF varies slightly during the immersion. It is a dynamic process of dissolution-precipitation for the formation of apatite on the surface. With prolonging immersion time, Ca and P ion concentrations increase gradually, and then approach equilibrium. The bone-like apatite layer forms on the composites surface, which possesses benign bioactivity and favorable biocompatibility and achieves osseointegration, and can provide firm fixation between HA60/316L SS composite implants and human body bone.

Study on Corrosion and Degradation Behavior of Mg-Ca Alloy in Simulated Body Fluid

The corrosion and degradation behavior of Mg-Ca binary alloy in simulated body fluid (SBF) were studied by immersion of pure Mg and Mg-Ca alloys with different Ca contents in SBF. The corrosion process was carried out by real-time measurement of sample weight, pH value of SBF and the microstructures of the immersed samples at different immersion time observed by electron microscopy. The result shows that Mg-Ca alloy with 0.7% Ca has better corrosion resistance than the one with 2.0% Ca. The product generated on the surface of Mg-0.7Ca during the immersion was identified by X-ray diffraction and energy spectrum analysis.

Calcium–phosphate–silicate composite bone cement: self-setting properties and in vitro bioactivity

In this study, a novel low temperature setting calcium phosphate-silicate cement was obtained by mixing CaHPO(4) x 2H(2)O (DCPD) and Ca(3)SiO(5) (C(3)S) with 0.75 M sodium phosphate buffers (pH = 7.0) as liquid phase. The self-setting properties of the obtained DCPD/C(3)S paste with liquid to powder ratio (L/P) of 0.6 ml/g, such as setting times, injectability, degradability and compressive strength were investigated and compared with that of DCPD/CaO cement system. The results indicated that, with the weight ratio of C(3)S varied from 20% to 40%, the workable DCPD/C(3)S pastes could set within 20 min, and the hydrated cement showed significantly higher compressive strength (around 34.0 MPa after 24 h) than that of the DCPD/CaO cement system (approximately 10.0 MPa). Furthermore, the in vitro pH value of the cements was investigated by soaking in simulated body fluid (SBF) for 12 h, and the result indicated that the DCPD/C(3)S did not induce significant increase or decrease of pH value in SBF. Additionally, the composite cement possesses better ability to support and stimulate cell proliferation than the DCPD/CaO cement. With good hydraulic properties, improved biocompatibility and moderate degradability, the novel DCPD/C(3)S bone cement may be a potential candidate as bone substitute.

BEHAVIOR OF PLASMA-SPRAYED HYDROXYAPATITE COATINGS ONTO CARBON/CARBON COMPOSITES IN SIMULATED BODY FLUID

Two types of hydroxyapatite (HA) coatings onto carbon/carbon composite ( C / C composites) substrates, deposited by plasma spraying technique, were immersed in a simulated body fluid (SBF) in order to determine their behavior in conditions similar to the human blood plasma. Calcium ion concentration, pH value, microstructure, and phase compositions were analyzed. Results demonstrated that both the crystal Ca – P phases or the amorphous HA do dissolve slightly, and the dissolution of CaO phases in SBF was evident after 1 day of soaking. The calcium-ion concentration was decreased and the pH value of SBF was increased with the increasing of the immersing time. The precipitation was mainly composed of HA, which was verified by X-ray diffraction (XRD) and electron-probe microanalyzer.

In Vitro Dissolution Behavior of Gel-Derived Bioactive Glasses in the SiO<sub>2</sub>-CaO-P<sub>2</sub>O<sub>5</sub>-MgO System

Bioactive glass-ceramics of the SiO2-CaO-P2O5-MgO system were fabricated by sol-gel-self propagating method. Two Gel-derived materials discs， 5S and 3S， were prepared by compression of powders. The materials obtained were examined in vitro with regard to the dissolution behavior and the formation ability of calcium phosphate layer on the surfaces of samples in simulated body fluid (SBF). Concentration of ions and pH value in SBF were determined by ICP-AES and micro acidity meter after 3S and 5S were immerged in SBF for intervals from 6h to 15 days and the surface characteristic of 3S and 5S soaked were determined by SEM. Experiment results showed that the formation ability of calcium phosphate on the surface of gel-derived materials depended on the speed of dissolution of samples, which related to original chemical composition and size of crystal on the surface of materials. With decreasing of Si content and increasing of Ca content, smaller crystal could be formed on the surface of 3S, which tended to dissolve more quickly in SBF. Solubility product of calcium phosphate can be reached more easily in the solution with high concentration of Ca and P and bone-like carbonate apatite formed easily on the surface of 3S.