silicon and tetraethoxysilane

Dimensional instability caused by sintering shrinkage is an inevitable drawback for conventional processing of hydroxyapatite (HA). A new preparation method for biphasic calcium phosphates was developed to increase micro pores and biodegradation without significant dimensional change. Powder pressed HA discs, under 100MPa, were immersed in a colloidal mixture of tetraethoxysilane (TEOS) and ammonium hydroxide for 10min, followed by drying, and then were sintered at 900°C, 1050°C, and 1200°C, respectively. Comparing with pure HA discs, the newly prepared product sintered up to 1200°C contained silicon substituted HA, beta-tricalcium phosphate, and calcium silicate with better micro-porosity, high specific surface area, less sintering shrinkage and the strength maintained. The cytocompatibility test demonstrated a better viability for D1 mice stem cells cultured on TEOS treated HA for 14days compared to the pure HA. This simple TEOS sol-gel pretreatment has the potential to be applied to any existing manufacturing process of HA scaffold for better control of sintering shrinkage, create micropores, and increase biodegradation.

Topics: Ammonium Hydroxide; Biocompatible Materials; Calcium Phosphates; Durapatite; Hydroxyapatites; Materials Testing; Silanes; Silicon

A new method was developed for the preparation of highly monodisperse isotopically enriched Si-29 silica nanoparticles ((29)Si-silica NPs) with the purpose of using them as spikes for isotope dilution mass spectrometry (IDMS) quantification of silica NPs with natural isotopic distribution. Si-29 tetraethyl orthosilicate ((29)Si-TEOS), the silica precursor was prepared in two steps starting from elementary silicon-29 pellets. In the first step Si-29 silicon tetrachloride ((29)SiCl4) was prepared by heating elementary silicon-29 in chlorine gas stream. By using a multistep cooling system and the dilution of the volatile and moisture-sensitive (29)SiCl4 in carbon tetrachloride as inert medium we managed to reduce product loss caused by evaporation. (29)Si-TEOS was obtained by treating (29)SiCl4 with absolute ethanol. Structural characterisation of (29)Si-TEOS was performed by using (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. For the NP preparation, a basic amino acid catalysis route was used and the resulting NPs were analysed using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), dynamic light scattering (DLS) and zeta potential measurements. Finally, the feasibility of using enriched NPs for on-line field-flow fractionation coupled with multi-angle light scattering and inductively coupled plasma mass spectrometry (FFF/MALS/ICP-MS) has been demonstrated.

Topics: Chlorides; Fractionation, Field Flow; Indicator Dilution Techniques; Isotopes; Mass Spectrometry; Nanoparticles; Scattering, Small Angle; Silanes; Silicon; Silicon Compounds; Silicon Dioxide; X-Ray Diffraction

In this study, bioactive glass (BG) particles were synthesized directly using spray pyrolysis (SP). Since the bioactivity of glass particles is well correlated with their chemical composition, how to obtain homogenous bioactive glass becomes an important issue. For SP, the main reason for chemical inhomogeneity was considered to be caused by the difference in the precipitation speed of each precursor. So, two Si-containing precursors of BG, namely tetraethyl orthosilicate (TEOS) and silicon acetate (SiA), have been applied to prepare BG particles. The bioglasses were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy to examine their phase composition, and surface structures, inner morphologies and chemical compositions. It was observed that, under the calcination temperature of 700 degrees C, TEOS-derived powder contained Si-rich nanoparticles and Si-deficit submicron particles as inhomogeneity, whereas the SiA-derived powder was homogenous. The reason of inhomogeneity is that TEOS dissolves in "volatile" ethanol more readily than in water via the SP mechanism of "gas-to-particle-conversion" to form Si-rich nanoparticles. The presence of Si-rich nanoparticles causes Si-deficit "wollastonite submicron particles" to form, which impairs the bioactivity. Finally, BG particle formation mechanisms from different precursors have been proposed.

Topics: Biocompatible Materials; Glass; Microscopy, Electron, Transmission; Nanoparticles; Silanes; Silicon; X-Ray Diffraction

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr(2+) act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO2 polymorphs and is at the origin of the epitaxial growth.

Topics: Cetrimonium; Cetrimonium Compounds; Crystallization; Gels; Quartz; Silanes; Silicon; Silicon Dioxide; Solutions; Surface Properties; Water

This study aimed to improve Ti-porcelain bonding strength through SiO2 modifications. Wax patterns were coated with SiO2 mixed with tetraethoxy silane (group C), patterns without coating were used as controls and subdivided into sandblasting group (group S) and polishing group (group P). Castingsurfaces were analyzed with XRD, while Ti-ceramic interfaces were characterized using SEM/EDS. Metal-ceramic specimens were tested in three point bending, and characterizations were also analyzed with SEM/EDS of porcelain debonding surfaces. In group C, SiO2 and Ti5Si3 phases were observed; SEM micrograph showed that Ti-porcelain had a compacted interface, and EDS maps of the interface illustrated the diffusion of Si, Al, and Sn to Ti, and cohesive fracture within the bonding agent. The bond strength of group C was 39.04±5.0 MPa, which was 15% higher than that of group S and 32% higher than that of group P. SiO2 coating could improve Ti-porcelain bond strength.

Topics: Aluminum; Coated Materials, Biocompatible; Dental Bonding; Dental Casting Technique; Dental Etching; Dental Materials; Dental Polishing; Dental Porcelain; Hot Temperature; Humans; Inlay Casting Wax; Materials Testing; Microscopy, Electron, Scanning; Silanes; Silicon; Silicon Dioxide; Spectrometry, X-Ray Emission; Stress, Mechanical; Surface Properties; Time Factors; Tin; Titanium; X-Ray Diffraction

Usage of supercritical carbon dioxide as a medium for finishing cotton fabrics with modified dimethylsiloxane polymers terminated with silanol groups was investigated, different cross-linkers namely 3-isocyanatepropyltriethoxysilane (IPES) and tetraethylorthosilicate (TEOS) were used for covalently bonding between silicon and cellulose. The presence and the amount of PDMS compounds on the treated fabrics were characterized by FT-IR. Qualitative and quantitative information on the distribution of the silicon molecules across the fibre cross section was provided by SEM/EDX analysis and Confocal Raman microscopy (CRM) respectively. The results confirm that all fibres treated with PDMS and IPES have larger silicon amounts than those treated with TEOS. SC-CO2 medium provides good coating of cotton surface with a 3D network of DMS compound and cross linker, and leads to forming highest DMS concentration in a layer between 1 and 2μ under the surface of cotton fabrics.

Topics: Carbon Dioxide; Cellulose; Dimethylpolysiloxanes; Shear Strength; Silanes; Silicon; Tensile Strength; Textiles

Tetraethoxysilane (TEOS) is used as a precursor in the industrial production of silica nanoparticles using thermal decomposition methods such as flame spray pyrolysis (FSP). Despite the industrial importance of this process, the current kinetic model of high-temperature decomposition of TEOS to produce intermediate silicon species and eventually form amorphous silica (R-SiO2) nanoparticles remains inadequate. This is partly due to the fact only a small proportion of the possible species is considered. This work presents the thermochemistry of practically all of the species that can exist in the early stages of the reaction mechanism. In order to ensure that all possible species are considered, the process is automated by considering all species that can be formed from the reactions that are deemed reasonable in the standard ethanol combustion model in the literature. Thermochemical data for 180 species (over 160 of which have not appeared in the literature before) are calculated using density functional theory with two different hybrid functionals, B3LYP and B97-1. The standard enthalpy of formation (DeltafH(298.15K) degrees) values for these species are calculated using isodesmic reactions. It is observed that internal rotation may be important because the barriers to rotation are reasonably low. Comparisons are then made between the rigid rotor harmonic oscillator approximation (RRHO) and the RRHO with some of the vibrational modes treated as hindered rotors. It is found that full treatment of the hindered rotors makes a significant difference to the thermochemistry and thus has an impact on equilibrium concentrations and kinetics in this system. For this reason, all of the species are treated using the hindered rotor approximation where appropriate. Finally, equilibrium calculations are performed to identify the intermediates that are likely to be most prevalent in the high-temperature industrial process. Particularly, Si(OH)4, SiH(OH)3, SiH2(OH)2, SiH3(OH), Si(OH)3(OCH3), Si(OH)2(OCH3)2, the silicon dimers (CH3)3-SiOSi(CH3)3 and SiH3OSiH3, and the smaller hydrocarbon species CH4, CO2, C2H4, and C2H6 are highlighted as the important species.

Topics: Silanes; Silicon; Temperature; Thermodynamics

Certain proteolytic enzymes are capable of mediating the processing of tri- and tetra-alkoxysilanes to form monolithic silica via the sol-gel process, or silsesquioxane sol-gels under green, solvent-free conditions.

Topics: Acids; Catalysis; Chymotrypsin; Gels; Hydrolysis; Isotopes; Magnetic Resonance Spectroscopy; Phase Transition; Silanes; Silicon; Silicon Dioxide; Trypsin

The aim of this work was to study the use of silicon oxide matrices for the immobilization and preservation of recombinant-protein-producing bacteria. We immobilized Escherichia coli BL21 transformants containing different expression plasmids. One contained DNA coding for a T-cell receptor beta chain, which was expressed as inclusion bodies in the cytoplasm. The other two encoded bacterial superantigens Staphylococcal Enterotoxin G and Streptococcal Superantigen, which were expressed as soluble proteins in the periplasm. The properties of immobilization and storage stability in inorganic matrices prepared from two precursors, silicon dioxide and tetraethoxysilane, were studied. Immobilized E. coli was stored in sealed tubes at 4 and 20 degrees C and the number of viable cells and level of recombinant protein production were analyzed weekly. Different tests showed that the biochemical characteristics of immobilized E. coli remained intact. At both temperatures selected, we found that the number of bacteria in silicon dioxide-derived matrix was of the same order of magnitude (10(9) cfu ml(-1)) as before immobilization, for 2 months. After 2 weeks, cells immobilized in an alkoxide-derived matrix decreased to 10(4) cfu ml(-1) at 4 degrees C, and no viable cells were detected at 20 degrees C. We found that immobilized bacteria could be used as a starter to produce recombinant proteins with yields comparable to those obtained from glycerol stocks: 15 mg l(-1) for superantigens and 2 mg l(-1) for T-cell receptor beta chain. These results contribute to the development of methods for microbial cell preservation under field conditions.

Topics: Bacteriological Techniques; Cells, Immobilized; Cold Temperature; Escherichia coli; Oxides; Plasmids; Preservation, Biological; Recombinant Proteins; Silanes; Silicon

The hydrolysis of tetraethoxysilane using the sol-gel process was used to produce silica matrices, and these were tested for the immobilization of lipase from Candida rugosa by three methods: physical adsorption, covalent binding, and gel entrapment in the presence and absence of polyethylene glycol (PEG-1450). The silica matrices and their derivatives were characterized regarding particle size distribution, specific surface area, pore size distribution (Brunauer, Emmett, and Teller [B.E.T.] method), yield of grafting (thermogravimetric analyzer [TGA]), and chemical composition (Fourier transform infrared). Immobilization yields based on recovered lipase activity varied from 3.0 to 32.0%, and the highest efficiency was attained when lipase was encapsulated in the presence of PEG.

Topics: Adsorption; Biotechnology; Candida; Enzymes, Immobilized; Hydrolysis; Lipase; Phase Transition; Polyethylene Glycols; Silanes; Silicon; Spectroscopy, Fourier Transform Infrared; Temperature

Two experiments were conducted using completely randomized designs to study the bioavailability of Si from three sources to growing rats and turkeys fed semipurified diets. The basal diets were dextrose-egg albumin for rats and dextrose-casein for turkeys. The Si sources were tetraethylorthosilicate (TES), sodium silicate (NaSil), and sodium zeolite A (NaZA). Rats and turkeys were supplemented at 500 and 270 ppm Si, respectively, from each source. A control group of unsupplemented rats and turkeys was included in each experiment. In general, irrespective of Si source, Si supplementation slowed (p < 0.05 or p < 0.01) growth rates in both rats and turkeys. Although dietary Si supplementation reduced (p < 0.05) plasma Mg levels and liver Zn concentrations in rats, it increased (p < 0.05) plasma P and reduced (p < 0.05) plasma Cu levels in turkeys. Rats on TES had significantly slower (p < 0.05 or p < 0.01) growth rates (5-10%) than those on NaSil or NaZA. In rats, NaZA and TES reduced (p < 0.05) hemoglobin concentrations and plasma Zn, respectively. However, plasma Mg levels were higher (p < 0.05) in TES than NaSil- or NaZA-fed rats. The source of the dietary Si did not affect (p < 0.05) the organ weights of rats and their mineral concentrations. Turkeys on TES diets grew at a significantly faster (p < 0.05) rate (15%) than those on NaSil or NaZA diets during the first 2 wk of experimentation. However, after 4 wk, there were no significant(p > 0.05) differences in growth between the Si sources. In turkeys, NaZA increased (p < 0.05) hematocrit levels and plasma Mg levels. Turkeys on NaZA diets had larger (p < 0.05) hearts and livers than those on NaSil but not TES. Liver Mn content was higher (p < 0.05) in turkeys on NaSil than TES or NaZA. Heart Zn was lower (p < 0.05) in turkeys on NaSil than TES, but not NaZA.

Topics: Aluminum; Animals; Biological Availability; Body Weight; Diet; Female; Hemoglobins; Liver; Myocardium; Random Allocation; Rats; Rats, Sprague-Dawley; Silanes; Silicates; Silicon; Sodium; Temperature; Time Factors; Turkeys; Zeolites

It has been shown that the prerequisite for glasses and glass-ceramics to bond to living bone is the formation of a layer of biologically active bonelike apatite on their surfaces. The hydrated silica formed on the surfaces of glasses and glass-ceramics plays an important role in nucleating the apatite. In the present study, the structure of the hydrated silica responsible for the apatite nucleation was investigated in an accellular simulated body fluid with ion concentrations nearly equal to those of human blood plasma. Three kinds of porous silica gels were prepared by hydrolysis and polycondensation of tetraethoxysilane in pure water or in aqueous solution containing polyethylene glycol or polyacrylic acid. The silica gels prepared in aqueous solution containing polyethylene glycol or polyacrylic acid had micron-size interconnected pores, whereas the gel prepared in pure water did not. All the gels contained a large volume of nanometer-size pores, almost the same amounts of silanol groups and D2 defect, and showed a high dissolution rate of the silica. Despite this, only the gel prepared in the solution containing polyethylene glycol formed the apatite on its surface in the simulated body fluid. This indicates that only a certain type of structural unit of the silanol group is responsible for the apatite nucleation.

Topics: Acrylates; Apatites; Body Fluids; Hydrolysis; Microscopy, Electron, Scanning; Polyethylene Glycols; Porosity; Silanes; Silica Gel; Silicon; Silicon Dioxide; Solubility; Surface Properties; X-Ray Diffraction

To clarify the time course of toxicological effects of tetraethoxysaline [Si(OC2H5)4, TEOS] on the kidney and the relationship between blood silicon levels (Si-B) and the effects, 250 mg/kg or 500 mg/kg TEOS was intraperitoneally administered to ten 5-week-old male ICR mice (SPF grade) in each group, and morphological and functional changes of the kidney were assessed at 12 h, 24 h, 3 days and 2 weeks after administration of TEOS. Injury to tubular epithelial cells was observed in mice killed 12 and 24 h after administration, and its severity increased with increasing dosage. The mean values of blood urea nitrogen exhibited dose-related increase in mice sacrificed 24 h after the administration. The concentrations of Si-B increased in order of the administered doses of TEOS, and then decreased steadily. The results of Si-B were consistent with the concept that renal toxicity of TEOS is mediated by siliceous compounds. The kidney was recovering from injury 3 days after administration, and had developed tubulointerstitial nephritis, which could be regarded as repaired lesion of acute injury, by 2 weeks after administration.

Topics: Animals; Blood Urea Nitrogen; Disease Models, Animal; Dose-Response Relationship, Drug; Injections, Intraperitoneal; Kidney; Kidney Function Tests; Kidney Tubules; Male; Mice; Mice, Inbred ICR; Microscopy, Electron; Nephritis, Interstitial; Silanes; Silicon; Specific Pathogen-Free Organisms

Three experiments were conducted to determine the effects of excess dietary calcium carbonate, phosphorus and urine acidifying and alkalizing salts on silica urolith formation in a model using rats fed dextrose-based diets containing 2% tetraethylorthosilicate (TES). Diets containing 2% TES lowered weight gains to 91-95% of gains made by rats fed non-TES diets. Urine silica concentrations of rats fed TES were generally in the range of 50-60 mg/dl. In experiment 1, rats fed TES with no additional dietary calcium carbonate had a silica urolith incidence of 35%. With additions of 1 and 2% calcium carbonate to the basal-TES diet, respective urolith incidences were 45 and 60% (r = 0.99, P less than 0.02). In experiment 2, monobasic sodium phosphate (MP) providing 0.2% additional phosphorus resulted in a mean urine pH of 6.42 and no uroliths. Dibasic sodium phosphate (DP) without and with 0.5% sodium bicarbonate (SB) resulted in respective urine pH values of 6.78 and 7.14 and urolith incidences of 15 and 20% (MP less than DP and DP + SB, P less than 0.05). However, the uroliths were small averaging less than 1 mg. In experiment 3, substitution of autoclaved egg albumin for casein, the protein source in experiments 1 and 2, resulted in urine pH of 7.45 and a silica urolith incidence of 46%. An equal-molar mixture of MP and DP providing an added 0.2% phosphorus resulted in a urine pH of 7.07 and reduced the urolith incidence to 4%, and 0.75% of dietary ammonium chloride either with or without the added 0.2% phosphorus gave urine acidification and complete protection from uroliths.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Administration, Oral; Animals; Bicarbonates; Body Weight; Calcium; Calcium Carbonate; Carbonates; Diet; Drug Interactions; Hydrogen-Ion Concentration; Magnesium; Male; Phosphorus; Rats; Rats, Inbred Strains; Silanes; Silicon; Silicon Dioxide; Sodium; Sodium Bicarbonate; Urinary Calculi

Topics: Fluorides, Topical; Gels; Hydrogen-Ion Concentration; Silanes; Silicon; Surface-Active Agents; Time Factors; Water

Topics: Ammonium Compounds; Chemical Phenomena; Chemistry, Physical; Emulsions; Fluorides; Fluorides, Topical; Gels; Hydrolysis; Phosphates; Polymers; Quaternary Ammonium Compounds; Silanes; Silicon; Sodium Fluoride; Surface-Active Agents; Time Factors

Antiprogesterone antiserum was entrapped within a polysiloxane copolymer prepared from a 3:1 mixture of tetraethoxysilane and 3-aminopropyltriethoxysilane monomers. 400 microliters of this monomer mixture entrapped 70 mg of the 140 mg of immunoglobulins which were added, and the protein could not be washed from the highly stable copolymer which formed. Approximately half of the entrapped antiprogesterone antiserum was found to retain progesterone binding capacity with an apparent Ka equal to that of free antiserum in solution and was insensitive to effects of pH between 3 and 7. These preliminary observations and the unique chemistry of polysiloxane polymer formation suggest that such polymers may be useful in the entrapment of proteins for a variety of applications.

Topics: Animals; Hydrogen-Ion Concentration; Immune Sera; Kinetics; Methods; Progesterone; Propylamines; Sheep; Silanes; Silicon; Silicones

Rats fed a dextrose-casein type of diet adequate for normal growth and containing 2% of tetraethylorthosilicate (TES) were used to study the effect of NaCl and Na2SO4 drinking waters, and dietary additions of chloride, sulfate and phosphate on formation of silica urinary calculi. In experiment 1, rats fed the basal-TES diet had a 53% incidence of silica urinary calculi. NaCl or Na2SO4 (0.07 N) drinking waters each increased (P less than 0.01) water intake and urine volume, whereas only NaCl reduced (P less than 0.05) the incidence of silica urinary calculi. The incidence of calculi in the rats treated with NaCl and Na2SO4 was 15 and 55%, respectively. The saline waters had similar effects on urine pH, silica, phosphorus, magnesium and calcium, as well as blood plasma magnesium and calcium. Plasma phosphorus tended to be higher (P = 0.08) in the NaCl-treated rats. In experiment 2, 50% of rats fed the basal-TES diet developed silica urinary calculi. Addition of 0.2 eq/kg diet of chloride, sulfate or phosphate as sodium salts (phosphate was an equal molar mixture of mono- and dibasic sodium phosphates) resulted in a reduction in silica urinary calculi (P less than 0.05) by dietary chloride (15% incidence) and phosphate (5% incidence) but not by sulfate (35% incidence). Water intake and urine volumes did not differ, urine calcium was increased (P less than 0.05) by sulfate, and urine phosphorus was increased (P less than 0.05) by phosphate. Blood plasma concentrations of calcium and magnesium did not differ, but plasma phosphorus was higher for animals fed the additional phosphate (P less than 0.1) or chloride (P less than 0.05) in the 2% TES diet.

Topics: Administration, Oral; Animals; Chlorides; Kidney; Male; Phosphates; Rats; Rats, Inbred Strains; Silanes; Silicon; Sulfates; Urinary Calculi; Water

Topics: Air Pollution; Ether; Silanes; Silicon