In vitro surface biocompatibility of high-content silicon-substituted calcium phosphate ceramics

The present work investigates surface biocompatibility of silicon-substituted calcium phosphate ceramics. Different silicon-substituted calcium phosphate ceramic bodies were prepared from co-precipitated powders by sintering at 1300°C. The in vitro bioactivity of the ceramics was assessed in simulated body fluid (SBF) at 37°C for periods up to 4 weeks. The changes in the surface morphology and composition were determined by scanning electron microscopy (SEM) coupled with electron probe microanalysis and energy dispersive spectrometer (EDX). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to observe the change in ionic concentration of SBF after removal of the samples. The bioactivity of the ceramics increased with an increasing silicate ion substitution in a systematic way. The surface of ceramics with 2.23% silicon substitution was partially covered with apatite layer after one week, while ceramics with 8.1% silicon substitution were completely covered with apatite in the first week. The porous microstructure of high-concentration Si-substituted ceramics helps the dissolution of surface ions and the leaching process. This allows SBF to reach supersaturation in a short time and accelerate the deposition of apatite layer.      

Study of the mineralization of coral implanted in vivo by radioactive tracers

Coral has ben used for the last ten years as bone substitution in the body because of its mechanical an osteoconductor properties. Our primary studies have shown, for the first time, the quantitative behavior of the atomic components. We study by some physical method of analysis a biocoral implanted in vivo. The natural biocorals used in this work are the calcium carbonated exoskeletons built by Madrepian coral polyps. Neutron activation analysis showed that initial coral, essentially CaCO₃, becomes a new material which has a mineral composition close to that of bone. In this work, we have studied the calcification mechanism of this implant by using radioactive tracers. We have established the transfer kinetics of calcium biomaterial in the blood circuit and showed its use by the organism for skeleton mineralization.     

Biocompatibility of some materials used in dental implantology: histological study

This study deals with bioreactive materials for potential applications as endosseus dental implants. Currently used dental implants are made of dental alloys but due to cytotoxic problems, high strength ceramic materials appear as an interesting alternative to these alloys. In order to combine good mechanical properties and promotion of the osteointegration process, a ceramic composite material composed of 10 wt.% tricalcium phosphate (TCP) mixed with partially stabilized zirconia has been elaborated. Such a ceramic has been implanted into albino rats, the sites of implantation being the adrenal gland for the toxicity evaluation and the sphenoid bone to estimate the osteogenesis potential. These results have been compared to those obtained with implants made of alumina (Al₂O₃), zirconia (ZrO₂) or poly(ethylene terephthalate) (Dacron®). In all cases no rejection effect was observed. The histological study indicated that ZrO₂-TCP ceramics induced a marginal and subjacent cell disorganization. However, the existence of an irregular cellular band indicated a cellular colonization process on the TCP particles. The microscopy study of the implants after removal confirmed the bioresorption of TCP.     

Mass spectrometric monitoring of Sr-enriched bone cements—from in vitro to in vivo

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a well-established technique in materials science, but is now increasingly applied also in the life sciences. Here, we demonstrate the potential of this analytical technique for use in the development of new bone implant materials. We tracked strontium-enriched calcium phosphate cements, which were developed for the treatment of osteoporotic bone, from in vitro to in vivo. Essentially, the spatial distribution of strontium in two different types of strontium-modified calcium phosphate cements is analysed by SIMS depth profiling. To gain information about the strontium release kinetics, the cements were immersed for 3, 7, 14 and 21 days in α-MEM and tris(hydroxymethyl)-aminomethane solution and analysed afterwards by ToF-SIMS depth profiling. For cements stored in α-MEM solution an inhibited strontium release was observed. By using principal component analysis to evaluate TOF-SIMS surface spectra, we are able to prove the adsorption of proteins on the cement surface, which inhibit the release kinetics. Cell experiments with human osteoblast-like cells cultured on the strontium-modified cements and subsequent mass spectrometric analysis of the mineralised extracellular matrix (mECM) prove clearly that strontium is incorporated into the mECM of the osteoblast-like cells. Finally, in an animal experiment, the strontium-doped cements are implanted into the femur of osteoporotic rats. After 6 weeks, only a slight release of strontium was found in the vicinity of the implant material. By using ToF-SIMS, it is proven that strontium is localised in regions of newly formed bone but also within the pre-existing tissue.

Study of controlled tetracycline release from porous calcium phosphate/polyhydroxybutyrate composites

Porous calcium phosphate ceramics were prepared by sintering of mixtures of nanocrystalline apatitic calcium phosphate and fibrous natural cotton cellulose after pressing at temperatures of 1150 °C and 1250 °C. Micro-and macropores were present in microstructures of ceramic samples. The microstructures of porous ceramics were similar to those observed in bone tissues and fiber-like randomly oriented texture was observed in ceramics. Polyhydroxybutyrate (PHB) biopolymer layers are distributed homogeneously in the samples after evaporation of the diluent (chloroform) from the PHB vacuum impregnated porous samples. The tetracycline (TTC) release rate decreases with the content of polyhydroxybutyrate in the ceramic samples, which corresponds to the rise in amount of biopolymer displaced in the pores of ceramics. The concentration of TTC in the phosphate buffer saline solution varies almost linearly with time after the first seven hours from the start of the release of the calcium phosphate ceramic samples with 2.4 mass % of polyhydroxybutyrate. The initial burst effect was significantly depressed by the preparation method used.     

Investigation of the thermal degradation of the aged pyrotechnic titanium hydride/potassium perchlorate

In previous works, the effects on the devitrification mechanism of a certain composition calcium phosphate with additives of TiO₂, SiO₂, Al₂O₃, CeO₂ have been studied. It was found that some metal oxide additives played a key role as the nucleation agent in calcium phosphate glass-ceramics, and the devitrification mechanism of calcium phosphate glass system was changed drastically by addition such as metal oxide. Hydroxyapatite (HAp), tricalcium phosphate (TCP) and β-calcium phosphate (β-CaP₂O₆) whisker are the three most biologically compatible materials to human bone in bio-ceramics field. In this work, the effect on devitrification mechanism and the physical properties of certain composition calcium phosphate glass with three above additives were investigated, and the result shown that although no fine crystalline was induced in the certain composition of calcium phosphate glass when a large amount of additive was added, but such additives play a catalyst role by lowering the activation energies of devitrification. It would supplement the mechanical properties and the biocompatibility for the calcium phosphate glasses.     

Trends in development of calcium phosphate-based ceramic and composite materials for medical applications: Transition to nanoscale

Current status and lines of research were considered for calcium phosphate-based ceramic materials intended for application in new technologies for damaged bone tissue regeneration. The main trend is toward mimicking the composition, structure, and properties of biological bone tissues by ceramic materials. This necessitated developmental efforts on synthesizing polysubstituted, in particular nanocrystalline, biphasic calcium phosphates and on preparing ceramics and composite materials thereof. The progress achieved in this area was reviewed, and certain benefits associated with medical application of these materials were discussed.     

The Sol-Gel Process as a Basic Technology for Nanoparticle-Dispersed Inorganic-Organic Composites

Nanoparticles containing hybrid materials became of interest for many areas in the last decade. The reason for this is the fact that, in addition to the molecular inorganic-organic hybrid network, the physical, electronical, optical or catalytical properties of nanoparticles resulting from the inorganic crystalline, glassy or metallic properties also can be used for the material tailoring. For this reason, a survey is given over some interesting developments. Furthermore, in case studies, examples are given for the effect of nanoparticles on the two component Ormosil type of hybrids composed of ethyl ortho-silicate (TEOS) and methylethoxy(methoxy)triethoxy silane (MTEOS, MTMOS). It was shown that the 6 nm SiO₂-containing nanocomposite hybrid sols can be dried in form of thick films up to 14 m after a one step dip-coating process and densified crack-free. This is attributed to the increase of relaxation ability and flexibility. This nanocomposite based on TEOS, MTEOS and particulate SiO₂ has been used to develop an industrial process for a new type of environmentally friendly glass fiber mat with a temperature resistance up to 600°C.     

New Bioactive Ceramics Obtained by Heat Treatment of Modified Polymeric Precursors

Summary: The aim of this work was to obtain pseudowollastonite-based ceramics and to determine its bioactive features. The materials were obtained by new method, namely thermal treatment of ceramic active fillers-containing polysiloxane polymeric precursor. As active fillers, commercially available Ca(OH)₂ and silica nanopowders (SiO₂) were used. The phase composition of ceramic products were analysed by the means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). The microstructure of ceramic products were studied by scanning electron microscopy (SEM) with EDS point analysis. The bioactivity was determined in “in vitro” conditions, by immersing of ceramic samples in simulated body fluid (SBF). The results presented in this work indicate that heat treatment of active fillers-containing polysiloxane precursor is an alternative method for receiving of pseudowollastonite-containing materials. Such obtained samples demonstrate bioactivity in “in vitro” conditions.     

The Inclusion of Timolol and Lisinopril in Calcium Phosphate Particles Covered by Chitosan: Application in Ophthalmology

Chitosan-covered calcium phosphate nanoparticles with the mean dynamic radii of 30 to 130 nm and ζ-potential of +22 ± 4 mV containing timolol and lisinopril are prepared and characterized. These particles are formed by the amorphous phase represented by amorphous calcium phosphate Ca _x (PO₄) _y · zH₂O and the crystalline phase represented by hydrated calcium hydrophoshate (brushite) CaHPO₄ · 2H₂O. The experiments in vivo demonstrated that the inclusion of timolol into calcium phosphate particles covered with chitosan substantially prolonged its effect on the intraocular pressure.     

Catalyst preparation by combustion synthesis for electrochemical hydrocarbon devices

Metals and ceramics can behave as active electrocatalyst materials, particularly in hydrocarbon oxidation in anodic reaction fuel cells. Combustion synthesis is a very reliable, fruitful and rapid synthesis method to produce metals, ceramics and cermets with low particle size and high specific surface area. This work describes the preparation of nanoparticle Pt/Ru alloys, ceramic perovskites such as Sm_0.95CoO_3–, and Sm_0.95CoO_3–/Pt cermets, and shows how promising these materials can be in the role of electrochemically active materials.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

151Eu Mössbauer Study of Calcium Aluminate Glass and Glass Ceramics Containing a Small Amount of Europium(III)

¹⁵¹Eu Mössbauer spectrum of IR-transmitting calcium aluminate glass, 60CaO·32Al₂O₃·5Fe₂O₃·3Eu₂O₃, consists of a broad peak due to distorted Eu(III) with and values of 0.91 and –2.02 mm·s^–1, respectively. Debye temperatures (_D) of 360 and 320 K were obtained from the temperature dependence of absorption area (A) and that of , respectively. These _D values indicate that Eu(III) atoms occupy substitutional sites of distorted Al(III)O₄ tetrahedra in calcium aluminate glass. The value of 0.62 mm/s obtained from the heat-treated sample (glass ceramic) indicates that Eu(III)-O bonds became less covalent. A smaller value of –1.20 mm·s^–1 was obtained for Eu(III) in the glass ceramic, indicating less distorted Eu(III)O₄ tetrahedra.     

Preparation of La2O3-TiO2-SiO2 Inorganic-Organic Hybrid Materials and Their Optical Properties

Inorganic-organic hybrid materials in La₂O₃-TiO₂-SiO₂ system were prepared from La(NO₃)₃, titanium tetraisopropoxide, and silicon alkoxides. Ternary transparent materials prepared from glycidyloxypropyltrimethoxysilane (GPTS) were obtained in a wide composition region (La₂O₃ 50 mol%, TiO₂ 40 mol%). Hybrid materials prepared using methyltrimethoxysilane (MTMS) at MTMS/TMOS = 1 were transparent in the composition of La₂O₃ 30 mol% and TiO₂ 25 mol%. La(NO₃)₃ crystallines or TiO₂ small particles were precipitated in translucent materials. La₂O₃ content strongly affected the bulk density compared with TiO₂ content. Absorption edge of the hybrid materials was shifted to longer wavelength as TiO₂ and La₂O₃ contents increased. Partial coefficient of refractive index for the three metal oxides increased in the order SiO₂ < TiO₂ < La₂O₃ for both hybrid materials.     

Bioactive composites fabricated by freezing‐thawing method for bone regeneration applications

Hydrogels are widely used for controlled delivery of therapeutic agents. However, hydrogels lack bioactivity to encourage bone formation and mechanical integrity. Moreover, chemically crosslinked hydrogels exhibit cytotoxic effect. To overcome these limitations poly‐vinyl alcohol (PVA) and poly‐acrylic acid (PAA) blends were combined with ceramic materials based on β tricalcium phosphate, wollastonite, and magnesium silicate with different pore size distributions. The final 3D matrix was physically crosslinked using various freeze thawing (F/T) cycles. FTIR and SEM analysis showed that ceramics were dispersed within the polymer matrix and formed hydrogen bonds. Swelling studies in buffer solution pH 7.4 showed an increase in polymer swelling when ceramic was added. Furthermore, rheological testing demonstrated that incorporation of ceramics caused an increase in mechanical properties which varies with different pore size distributions of ceramics grains added. DSC thermograms showed increased T_g values for samples containing ceramics. Antimicrobial activity containing ciprofloxacin was tested against a pathogen associated with osteomyelitis and presented positive results with ciprofloxacin. The combination of increased strength and ability to encapsulate a clinically relevant antimicrobial agent indicates that the composite tested in this study has potential for the treatment of osteomyelitis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 761–773     

Preparation of a biphasic calcium phosphate from Ca(H2PO4)2·H2O AND CaCO3

Sintered hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) are the two most common bio-ceramics for bone substitute. Although their composition are analogous to the constituent of human hard tissue, but some disadvantages are always exist till now, such as they need a high temperature sintering process, and this would lose the functional groups for bioactivity and closed the micro- pores without any interconnections, that hamper the body fluid transportation and angiogenesis during regeneration. Furthermore, the sintered ceramics with block and fixed size is difficult to fit non-regular defect area. In this study, the mixtures of Ca(H₂PO₄)₂·H₂O and CaCO₃ were adjusted firstly, then distilled water were introduced in wet chemical method, and a biphasic ceramic of HAp/β-TCP will be obtained after drying and sintering, then the result product that prepared by wet chemical method will be the sample in this investigation. The physical properties of result powders were characterized by DTA/TG, XRD and SEM, respectively, the particle size of two bio-ceramics that after heat treatment were found under 5 μm in SEM examination. Powder type calcium phosphate ceramics with the Ca/P molar ratio of 1.67 can be as bone cement by mixing with polymeric binder, the fine particle product of the setting cement will possess micro-pores and macro-pores that after suitable heat treatment process, and this is good for fluid transportation and tissue regeneration.     

Ho3+/Yb3+共掺ZnO-Al2O3-GeO2-SiO2玻璃陶瓷的制备和上转换发光性质

综合ZnO-Al₂O₃-SiO₂系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho³⁺/Yb³⁺共掺以ZnAl₂O₄为主晶相的ZnO-Al₂O₃-GeO₂-SiO₂系玻璃陶瓷。因[GeO₄]四面体和[SiO₄]四面体都是玻璃网络形成体,讨论了GeO₂取代SiO₂对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO₂的取代量为10.55%（w/w）时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色（546 nm）和弱的红色（650 nm）上转换发光,并研究了不同Ho³⁺/Yb³⁺掺杂比对样品上转换发光的影响,最终结果表明当Ho³⁺/Yb³⁺掺杂比为1：11（n/n）时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。     

Formation characteristics of calcium phosphate deposits on a metal surface by H2O2-electrolysis reaction under various conditions

The cathodic electrolysis of H₂O₂ (H₂O₂ + e⁻ → OH⁻ + OH) on a metal surface in the presence of calcium and phosphate ions results in the formation of calcium phosphate deposits on the metal surface. In this study, the deposits formed under various treatment conditions (pHs, concentrations and ratios of calcium/phosphate ions, and so on) were characterized by scanning electron spectroscopy (SEM), and X-ray diffractometry. The exclusive formation of hydroxyapatite, HAP, was observed under comparatively narrow conditions (pH 3–4, [Ca+]/[PO₄³⁻] = 25 mM/15 mM), which is clearly different from the reported conditions for the deposition of HAP on titanium substrates. HAP was deposited in the form of a layer, comprised of morphologically amorphous HAP flakes that were less than 20 nm thick. SEM and FTIR analyses of the deposit at different stages of H₂O₂-electrolysis revealed that a few dozen nanometer-sized spheres of amorphous calcium phosphate were formed in the first step and then fused with each other to form ribbon-like flakes of HAP or broken glass-like brushite, depending on the pH. The pH for HAP formation on a stainless steel surface was markedly lower than that used for titanium, and the observed process by which amorphous calcium phosphate is converted to HAP was markedly different from that for the electrochemical deposition (electrolysis of water) of HAP on a titanium substrate.     

The vibrational spectra and normal coordinate analyses of cubic and monoclinic SiP2O7

The infrared and Raman spectra of cubic and monoclinic SiP₂O₇ were measured and interpreted by normal coordinate analyses using a modified valence force field. Band assignments were made for the vibrational modes of these materials, including those that involved the SiO₆ units. The calculated force constants for the SiO₆ and the P₂O₇ units were consistent with those for SiO₄- and P₂O₇-containing materials as well as stishovite. The Si-O stretching force constants for the SiO₆ units were considerably lower than those for SiO₄ units.     

Preparation of bioactive microspheres of organic modified calcium silicates through sol–gel processing

Bioactive ceramics show specific biological activity, a bone-bonding ability, and are used as bone-repairing materials. Particles of bioactive ceramics may be used as fillers for fabricating bioactive composites where bioactive fillers are dispersed in a polymer matrix. Chemical bonding between the filler and the organic matrix requires an effective organic modification of the bioactive filler. Previous studies have reported that inorganic glasses in the CaO–SiO₂ system act as fundamental components showing bioactivity, as they show a high potential to form bone-like apatite after exposure to a body fluid. Therefore, organically modified microspheres composed of CaO–SiO₂ gels can be useful as bioactive fillers to produce bioactive composites. In this study, the conditions for the preparation of organically modified gels composed of CaO–SiO₂ were investigated using sol–gel processing of tetraethoxysilane, calcium nitrate tetrahydrate and silane coupling agents (SCAs), such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane (GPS), along with polyethyleneglycol (PEG). Spherical particles with diameter of 2–3 μm were obtained when adding the SCAs, except for GPS with PEG. Incorporation of the SCAs was confirmed using Fourier transform infrared spectroscopy. All the samples prepared with the SCAs formed bone-like apatite on their surfaces in a simulated body fluid within a period of 1 day. These results indicate that bioactive microspheres of organically modified CaO–SiO₂ gels can be obtained using sol–gel processing with SCAs.     

Mg<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>SiO<Subscript>4</Subscript> compound obtained via sol–gel method: structural,morphological and electrochemical properties

Prospective cathode materials Mg_2-xMn _x SiO₄ (0.0?≤?x?≤?0.4) for magnesium-ion secondary battery were synthesized using sol gel method. Crystalline structure, morphology, particle size, electrical and electrochemical properties of the samples were investigated. X-ray diffraction patterns of the materials exhibited no extra peak for x?≤?0.6 indicated that Mg_2-xMn _x SiO₄ materials were successfully synthesized. Mn doping in magnesium site did not affect the formation of single phase, and this probably due to the low concentration of Mn to induces structural changes. Mn doping contributed to the enhancement of the electrochemical performance of Mg₂SiO₄. For this work, Mg_1.4Mn_0.6SiO₄ which possesses the largest unit cell volume, smallest charge transfer resistance, and highest conductivity value showed the most promising electrochemical performance compared to the other samples. These results indicated the suitability of the Mg_2-xMn _x SiO₄ to be exploiting further for potential applications as solid electrolytes in electrochemical devices and strengthen the fact that doping could be an effective way to enhanched the structural, electrical and electrochemical performance of materials.

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