Papers by Keyword: Strontium

Abstract: Whether silicate-substituted strontium apatite (SrSiP) stimulates osteogenesis on the surface of implants has been evaluated in the present study. Polyether ether ketone (PEEK) disks were coated with a nanocrystalline SrSiP dispersion using CO₂ laser irradiation. At approximately 300°C, the coating layer of SrSiP was tightly adhered to the surface of PEEK disks. The SrSiP-coated PEEK showed excellent bioactive properties when bone marrow-derived mesenchymal stem cells were cultured on the PEEK disks, when compared to the untreated PEEK disks.

Abstract: The results of the studies on complex oxide systems based on antimony oxide are presented with the aim to isolate strontium from radioactive wastes solutions. The compositions for experimental investigations are selected by computational screening of potentially suitable mixed oxide systems using atomistic modeling. Based on the results of experimental studies of selected compositions, methods for isolating strontium are proposed for various solutions and conditions of disposal.

Abstract: In this work, the sol-gel method was used to prepare composite gels based on 1,2-bis(5-triethoxysilyl-3-thiopentoxy)ethane and tetraethoxysilane, which showed sorption properties for strontium cations. Composite gels with colloidal silica were obtained. The obtained gels possess sorption activity to strontium cations. Template synthesis of gels in the presence of cesium cations was carried out. The results of sorption demonstrate the expected manifestation of the template effect, which determines the selectivity to cesium cations.

Abstract: A simple chemical conversion coating was adopted to deposit zinc calcium phosphate (ZCP) coating and strontium doped ZCP (SZCP) coating on AZ31 magnesium alloy to induce biocompatibility and reduce the degradation rate. The surface morphology, chemical composition and functional groups of the coating were characterized by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), X-Ray Diffraction (XRD) studies and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy respectively. SZCP coating formed at 20 min deposition time produced crack free surface with a high degree of crystallinity with barrier property, which ultimately retards the dissolution of magnesium in Simulated Body Fluid (SBF). The corrosion resistance of AZ31 magnesium alloy was improved by SZCP coating as evident from hydrogen evolution test (HET). Cytotoxicity evaluation with L969 cells showed that Sr doped ZCP coatings showed less toxicity on resorbable magnesium alloys.

Abstract: Variety of different bone substitutive materials are synthetized to improve bone healing potentials in pathological bone conditions. Physiologically active molecules within biomaterials, can initiate expression level of biomarkers, regulating bone remodeling. Aim of our study was to analyze bone healing process in bone defects followed by implantation with 5% strontium substituted hydroxyapatite (HAP) /tricalcium phosphate (TCP) 70/30 granules (group A) or HAP/TCP biphasic ceramic granules without strontium substitution (group B), or sham surgery affected bone (group C) in osteoporotic rabbits’ femur. Tissue samples from contralateral intact left leg were used for evaluation of systemic effects after surgery. Changes of bone volume were measured and appearance of OPG, NFkB-105, OC, COL-1, BMP-2/4, MMP-2, TIMP-2, IL-1 and IL-10-positive osteocytes in osteoporotic rabbits’ bone defect were evaluated. No statistical difference between groups of trabecular bone volume was detected. All analyzed markers showed higher appearance of positive osteocytes in groups A and B with comparison to control left leg (p<0.05). Only NFkB105-positive cells showed important difference between sham surgery affected leg and control one (p=0.034). Numerous OPG-positive cells appeared in group A, while moderate number of them was found in groups B and C (p=0.025; p=0.027). Numerous to abundant OC-positive osteocytes were detected in group A, while moderate in group C (p=0.034). Statistical difference of rest biomarkers between groups was not detected. We concluded that implantation of biomaterials in osteoporotic bone improves local bone regenerative properties. However, the notable increase of OPG-containing cells proves the increase of osteoclastogenesis suppression and gives the evidence for renew of bone functionality.

Abstract: A biodegradable Mg-4Zn-0.6Zr alloy with different content of strontium (Sr) was prepared and studied for orthopedic applications biomaterials. The effects of Sr on the microstructure and corrosion degradation of the as-cast Mg-4Zn-0.6Zr-xSr (ZK40xSr) alloys were investigated. The optical micrograph (OM) observation, energy-dispersive spectrometer (EDS), X-ray diffractometer (XRD) and immersion test were used. The grain size of Mg-4Zn-0.6Zr alloys was reduced obviously with the addition of Sr. The excess of Sr would lead to grain size increasing and grain boundaries widening. The possible presence of the following constituent phases in the grain boundaries: α-Mg, Mg₁₇Sr₂, MgZn, Zn_xSr_y binary and Mg_xZn_ySr_z ternary phase. The formation of Zn_xSr_y and Mg_xZn_ySr_z phase owed to the larger difference of electronegativity values of Zn and Sr. The immersion tests indicated that the average corrosion rate of the as-cast ZK40xSr alloys increased with the increase of Sr content. It contributed to the micro-galvanic corrosion between the α-Mg with the continuous distribution of grain boundaries precipitates.

Abstract: In this work, nanocrystalline hydroxyapatite (HAp) powders were synthesized through wet precipitation method by adjusting the reaction temperature between 0 °C and 5 °C. The influence of biologically active Mg and Sr addition on HAp crystalline structure and thermal behavior was assessed. In all synthesis, nanocrystalline and/or amorphous HAp was found to be the major phase, and was accompanied by Ca(OH)₂ as the minor phase. Results suggested that Sr and Mg have an impending effect on nucleation, crystallization and thermal stability of HAp. The addition of Sr or Mg promoted deviation from stoichiometry and formation of amorphous components, which affected thermal stability and sintering behavior of the synthesis products.

Abstract: It is well known that the presence of phosphorus in hypoeutectic Al-Si alloys causes coarsening of Al-Si eutectic even when the phosphorus concentration is as low as a few ppm. The reason is that phosphorus reacts with aluminum to form AlP, the particles of which serve as potential nuclei for silicon due to a very similar lattice parameter with Si. The purpose of this study is to investigate the possibilities for reducing the nucleation potency of AlP by changing the alloy chemistry. The experiments include melting and solidification of a number of aluminum alloys under different conditions. After that, the samples are examined using SEM and TEM microscopy to elucidate the presence of phosphorus-containing compounds and to explain their formation mechanism. The experimentally obtained data are discussed on a systematic basis of thermodynamic calculations and compared with the corresponding data from the relevant literature. Particularly, the results reveal that such elements as Mg, Ca and Sr are potentially capable of neutralizing the nucleation activity of AlP although their effect is dependent on the presence of other chemical elements in the aluminium alloy.

Abstract: Some piezoelectric properties of lead zirconate titanate PbZr_0.53Ti_0.47O₃ ceramic samples sintered at 1100oC for 3 hours has been investigated in this work and compared to the strontium modification at 0.2, 0.4, and 0.6 mol%. Polarization versus Electric Field curve and d₃₃ and K_p piezoelectric parameters was taken at room temperature in order to investigate the correlation with phase amount and lattice parameters of crystalline phases calculated through Rietveld refinement. The results indicated the lead substitution with 0.4 mol% of strontium enhances the d₃₃ and K_p piezoelectric parameters, but there is no systematic variation of the piezoelectric properties with strontium content. By the other hand, tetragonal phase seems plays an important rule on piezoelectric devices operating near the room temperature and some correlations could be found.

Abstract: Bone tissue is a composite material that has hydroxyapatite (HA) as its main inorganic phase component. The biological apatites have low crystallinity and contain cationic and anionic substitutions in their structure, which differ from the available synthetic ceramics. The purpose of this study is to evaluate the biocompatibility of nanostructured carbonated hydroxyapatite microspheres containing 5 wt% strontium (SrcHA) compared with the biocompatibility of carbonated hydroxyapatite (cHA), both synthesized at 37°C and non-sintered, used to control stoichiometric HA microspheres in subcutaneous tissue of mice. The biomaterials (BM) were characterized using X-ray Diffraction (XRD), Vibrational Spectroscopy in an Infrared Fourier Transform (VSIRFT) and Scanning Electron Microscopy (SEM). Forty five balb-C mice were randomly divided into four groups of 15 animals each: SrcHA, cHA, HA, and without material implantation (Sham group). All samples were histologically processed for descriptive evaluation of the biological effect. At each experimental period (1, 3 and 9 weeks), there was a higher biosorption of the tested biomaterials observed in contrast with the HA. The cHA group was the only group completely phagocytosed by macrophages and giant cells after 9 weeks. All biomaterials proved to be biocompatible, and the cHA and SrcHA 3% groups exhibited a faster bioabsorption in comparison with the control group. The doping of strontium did not cause a greater biological response after the 3 experimental periods.