silicon and calcium-silicate

To investigate the effect of a fluoride-containing aluminocalciumsilicate nanoparticle glass dispersed aqueous solution (Nanoseal) on enamel and dentin, under the hypothesis that this material can form insoluble mineral deposits that confer acid resistance to the tooth structure and occlude open dentin tubules.. Labial enamel and dentin of human extracted incisors were used. Morphology of the enamel and dentin artificially demineralized with a lactic acid solution that before and/or after coated with the test material were analyzed with a wavelength-dispersive X-ray spectroscopy electron probe microanalyzer with an image observation function (SEM-EPMA). Moreover, incorporation of the calcium and silicon by enamel and dentin were also detected with SEM-EPMA.. Application of the fluoroaluminocalciumsilicate-based tooth coating material resulted in the deposition of substances (nanoparticles) onto the enamel surface porosities and open dentin tubules on the artificial lesions. Prior coating with the test material reduced the demineralization-induced loss of enamel and dentin. Moreover, Ca and Si incorporation into superficial enamel and dentin was detected.

Topics: Aluminum Compounds; Calcium; Calcium Compounds; Cariostatic Agents; Dental Enamel; Dental Enamel Solubility; Dentin; Dentin Desensitizing Agents; Dentin Solubility; Electron Probe Microanalysis; Fluorides; Humans; Hydrogen-Ion Concentration; Materials Testing; Microscopy, Electron, Scanning; Nanoparticles; Saliva, Artificial; Silicates; Silicon; Silicon Compounds; Spectrometry, X-Ray Emission; Temperature; Time Factors; Tooth Demineralization

Silicon-rich lye (SRL), a byproduct generated from pre-treatment of coal-based solid waste (CSW), was considered as a preponderant silicon source to prepare hierarchically nanostructured calcium silicate hydrate (C-S-H). Through the novel mild-causticization synthesis strategy, C-S-H was prepared under optimal caustic process conditions at time of 3 h, temperature of 80 °C, Ca/Si of 1.25:1, and active CaO to obtain a conversion rate of Si up to 97.33 % during the high-value utilization of SRL. The synthesized C-S-H possesses abundant mesoporous structure and massive exchangeable active sites, whose formation is advanced through an appropriate elevation regulation of caustic temperature and time. The silicate chain depolymerization occurs to C-S-H prepared in the highly alkaline system at higher caustic temperature, longer caustic period, especially at existence of massive sodium ions, but it presents higher polymerization degree at more aluminum co-existing. The adsorption capacity up to 119.27 mg/g for C-S-H presents a valid removal performance toward phosphorus in the wastewater than massive present reports. The removal mechanism of phosphorus can be identified as the surface chemisorption and formation of calcium phosphate co-precipitation. This study can provide considerable and potential guidance to the coordinated disposal between industrial solid wastes and wastewater purification.

Topics: Aluminum; Calcium Compounds; Caustics; Coal; Industrial Waste; Lye; Phosphorus; Silicates; Silicon; Solid Waste; Wastewater

Topics: Animals; Bone Cements; Bone Regeneration; Calcium Compounds; Calcium Phosphates; Glass Ionomer Cements; Ions; Osteogenesis; Rabbits; Silicates; Silicon; Zinc

The lack of drugs that target both disease progression and tissue preservation makes it difficult to effectively manage rheumatoid arthritis (RA). Here, we report a porous silicon-based nanomedicine that efficiently delivers an antirheumatic drug to inflamed synovium while degrading into bone-remodeling products. Methotrexate (MTX) is loaded into the porous silicon nanoparticles using a calcium silicate based condenser chemistry. The calcium silicate-porous silicon nanoparticle constructs (pCaSiNPs) degrade and release the drug preferentially in an inflammatory environment. The biodegradation products of the pCaSiNP drug carrier are orthosilicic acid and calcium ions, which exhibit immunomodulatory and antiresorptive effects. In a mouse model of collagen-induced arthritis, systemically administered MTX-loaded pCaSiNPs accumulate in the inflamed joints and ameliorate the progression of RA at both early and established stages of the disease. The disease state readouts show that the combination is more effective than the monotherapies.

Topics: Animals; Antirheumatic Agents; Arthritis, Rheumatoid; Calcium; Drug Carriers; Inflammation; Methotrexate; Mice; Nanomedicine; Porosity; Silicon

It has recently been demonstrated that the addition of zinc can enhance the mechanical strength of tricalcium silicates (C

Topics: Calcium Compounds; Silicates; Silicon; Zinc

Vascularization is an important early indicator of osteogenesis involving biomaterials. Bone repair and new bone formation are associated with extensive neovascularization. Silicon-based biomaterials have attracted widespread attention due to their rapid vascularization. Although calcium phosphate cement (CPC) is a mature substitute for bone, the application of CPC is limited by its slow degradation and insufficient promotion of neovascularization. Calcium silicate (CS) has been shown to stimulate vascular endothelial proliferation. Thus, CS may be added to CPC (CPC-CS) to improve the biocompatibility and neovascularization of CPC. In the early phase of bone repair (the inflammatory phase), macrophages accumulate around the biomaterial and exert both anti- and pro-inflammatory effects. However, the effect of CPC-CS on macrophage polarization is not known, and it is not clear whether the effect on neovascularization is mediated through macrophage polarization. In the present study, we explored whether silicon-mediated macrophage polarization contributes to vascularization by evaluating the CPC-CS-mediated changes in the immuno-environment under different silicate ion contents both in vivo and in vitro. We found that the silicon released from CPC-CS can promote macrophage polarization into the M2 phenotype and rapid endothelial neovascularization during bone repair. Dramatic neovascularization and osteogenesis were observed in mouse calvarial bone defects implanted with CPC-CS containing 60% CS. These findings suggest that CPC-CS is a novel biomaterial that can modulate immune response, promote endothelial proliferation, and facilitate neovascularization and osteogenesis. Thus, CPC-CS shows potential as a bone substitute material.

Topics: Animals; Bone Cements; Bone Regeneration; Calcium Compounds; Calcium Phosphates; Cell Differentiation; Cell Survival; Macrophage Activation; Male; Mice; Mice, Inbred C57BL; Neovascularization, Physiologic; Osteogenesis; RAW 264.7 Cells; Silicates; Silicon; Skull

This research was developed to investigate whether inoculation with Azospirillum brasilense in combination with silicon (Si) can enhance N use efficiency (NUE) in wheat and to evaluate and correlate nutritional and productive components and wheat grain yield. The study was carried out on a Rhodic Hapludox under a no-till system with a completely randomized block design with four replications in a 2 × 2 × 5 factorial scheme: two liming sources (with Ca and Mg silicate as the Si source and limestone); two inoculations (control - without inoculation and seed inoculation with A. brasilense) and five side-dress N rates (0, 50, 100, 150 and 200 kg ha

Topics: Azospirillum brasilense; Calcium Compounds; Crop Production; Fertilizers; Magnesium Silicates; Nitrogen; Silicates; Silicon; Triticum

The scaffolds, which morphologically and physiologically mimic natural features of the bone, are of high demand for regenerative medicine. To address this challenge, we have developed innovative bioactive porous silicon- wollastonite substrates for bone tissue engineering. Additive manufacturing through selective laser melting approach has been exploited to fabricate scaffolds of different architecture. Unique material combining osteoinductivity, osteoconductivity and bioactive elements allows flexibility in design. As the porous structure is required for the ingrowth of the bone tissue, the CAD designed scaffolds with pore size of 400 μm and hierarchical gradient of pore size from 50 μm to 350 μm have been 3D printed and tested in vitro. The scaffolds have demonstrated not only the enhanced viability and differential patterning of human mesenchymal cells (hMSC) guided by the biomimetic design onto extra and intra scaffold space but also promoted the osteogenic differentiation in vitro. Both homogeneous and gradient scaffolds have shown the differential expression of primary transcription factors (RUNX2, OSX), anti-inflammatory factors and cytokines, which are important for the regulation of ossification. The effective elastic modulus and compressive strength of scaffolds have been calculated as 1.1 ± 0.9 GPa and 37 ± 13.5 MPa with progressive failure for homogeneous structured scaffold; and 1.8 ± 0.9 GPa and 71 ± 9.5 MPa for gradient-structured scaffold with saw-tooth fracture mode and sudden incognito failure zones. The finite element analysis reveals more bulk stress onto the gradient scaffolds when compared to the homogeneous counterpart. The findings demonstrate that as-produced composite ceramic scaffolds can pave the way for treating specific orthopaedic defects by tailoring the design through additive manufacturing.

Topics: Bone and Bones; Calcium Compounds; Humans; Lasers; Osteogenesis; Porosity; Silicates; Silicon; Tissue Engineering; Tissue Scaffolds

Many agrowastes are being used for energy production by combustion in power plants. This process generates huge amounts of ash, which has a potential pozzolanic activity for blending with Portland cement or hydrated lime. In this paper, the ash obtained from elephant grass (Pennisetum purpureum Schum var. purple) leaves (EGLs) was studied, including the silicon content and its distribution, the presence of other compounds, and in addition, the presence of silica bodies (phytoliths). Combustion temperatures of 450 and 650°C produced an unaltered inorganic skeleton (spodogram), whereas at 850°C, there is a sintering process because of high potassium content in the ash. Phytoliths and different types of hairs were identified, and they contained high percentages of silica. Magnesium (mainly as periclase) was distributed in the most porous parts in the interior of the leaves. The silica can react with calcium hydroxide (pozzolanic reaction) forming calcium silicate hydrates (observed by field-emission scanning electron microscopy and thermogravimetric analysis). Fixed lime percentages at 28 curing days (63%) indicated the high reactivity of EGL ashes in calcium hydroxide pastes due to the pozzolanic reaction. This study demonstrates the possibility of the reuse of ashes from EGLs for the production of environmental-friendly cements.

Topics: Agriculture; Calcium Compounds; Calcium Hydroxide; Fires; Magnesium; Pennisetum; Plant Leaves; Potassium; Silicates; Silicon

Recently a modified glass ionomer cement (GIC) with enhanced bioactivity due to the incorporation of wollastonite or mineral trioxide aggregate (MTA) has been reported. The aim of this study was to evaluate the cytotoxic effect of the modified GIC on odontoblast-like cells. The cytotoxicity of a conventional GIC, wollastonite modified GIC (W-mGIC), MTA modified GIC (M-mGIC) and MTA cement has been evaluated using cement extracts, a culture media modified by the cement. Ion concentration and pH of each material in the culture media were measured and correlated to the results of the cytotoxicity study. Among the four groups, conventional GIC showed the most cytotoxicity effect, followed by W-mGIC and M-mGIC. MTA showed the least toxic effect. GIC showed the lowest pH (6.36) while MTA showed the highest (8.62). In terms of ion concentration, MTA showed the largest Ca(2+) concentration (467.3 mg/L) while GIC showed the highest concentration of Si(4+) (19.9 mg/L), Al(3+) (7.2 mg/L) and Sr(2+) (100.3 mg/L). Concentration of F(-) was under the detection limit (0.02 mg/L) for all samples. However the concentrations of these ions are considered too low to be toxic. Our study showed that the cytotoxicity of conventional GIC can be moderated by incorporating calcium silicate based ceramics. The modified GIC might be promising as novel dental restorative cements.

Topics: Aluminum; Aluminum Compounds; Animals; Biocompatible Materials; Calcium; Calcium Compounds; Culture Media; Dental Cements; Drug Combinations; Fluorine; Glass Ionomer Cements; Hydrogen-Ion Concentration; Ions; Mice; Odontoblasts; Oxides; Silicates; Silicon; Strontium; Surface Properties

Calcium ions react with silicic acid released from dissolving porous silicon nanoparticles to create an insoluble calcium silicate shell. The calcium silicate shell traps and protects an siRNA payload, which can be delivered to neuronal tissues in vitro or in vivo. Gene delivery is enhanced by the action of targeting and cell-penetrating peptides attached to the calcium silicate shell.

Topics: Animals; Brain; Brain Injuries; Calcium Compounds; Cell Line, Tumor; Disease Models, Animal; Mice; Nanoparticles; Porosity; RNA, Small Interfering; Silicates; Silicon

It is widely recognized that carbonic anhydrase (CA) participates in silicate weathering and carbonate formation. Nevertheless, it is still not known if the magnitude of the effect produced by CA on surface rock evolution changes or not. In this work, CA gene expression from Bacillus mucilaginosus and the effects of recombination protein on wollastonite dissolution and carbonate formation under different conditions are explored. Real-time fluorescent quantitative PCR was used to explore the correlation between CA gene expression and sufficiency or deficiency in calcium and CO₂ concentration. The results show that the expression of CA genes is negatively correlated with both CO₂ concentration and ease of obtaining soluble calcium. A pure form of the protein of interest (CA) is obtained by cloning, heterologous expression, and purification. The results from tests of the recombination protein on wollastonite dissolution and carbonate formation at different levels of CO₂ concentration show that the magnitudes of the effects of CA and CO₂ concentration are negatively correlated. These results suggest that the effects of microbial CA in relation to silicate weathering and carbonate formation may have increased importance at the modern atmospheric CO₂ concentration compared to 3 billion years ago.

Topics: Atmosphere; Bacillus; Calcium Compounds; Carbon Dioxide; Carbonates; Carbonic Anhydrases; Electrophoresis, Polyacrylamide Gel; Gene Expression Regulation, Enzymologic; Hydrogen-Ion Concentration; Kinetics; Recombinant Proteins; RNA, Messenger; Silicates; Silicon; Solubility; Weather

The investigation of the bone regeneration ability, degradation and excretion of the grafts is critical for development and application of the newly developed biomaterials. Herein, the in vivo bone-regeneration, biodegradation and silicon (Si) excretion of the new type calcium silicate (CaSiO3, CS) bioactive ceramics were investigated using rabbit femur defect model, and the results were compared with the traditional β-tricalcium phosphate [β-Ca3(PO4)2, β-TCP] bioceramics. After implantation of the scaffolds in rabbit femur defects for 4, 8 and 12 weeks, the bone regenerative capacity and degradation were evaluated by histomorphometric analysis. While urine and some organs such as kidney, liver, lung and spleen were resected for chemical analysis to determine the excretion of the ionic products from CS implants. The histomorphometric analysis showed that the bioresorption rate of CS was similar to that of β-TCP in femur defect model, while the CS grafts could significantly stimulate bone formation capacity as compared with β-TCP bioceramics (P < 0.05). The chemical analysis results showed that Si concentration in urinary of the CS group was apparently higher than that in control group of β-TCP. However, no significant increase of the Si excretion was found in the organs including kidney, which suggests that the resorbed Si element is harmlessly excreted in soluble form via the urine. The present studies show that the CS ceramics can be used as safe, bioactive and biodegradable materials for hard tissue repair and tissue engineering applications.

Topics: Absorbable Implants; Animals; Bone Regeneration; Bone Substitutes; Calcium Compounds; Calcium Phosphates; Ceramics; Femur; Male; Materials Testing; Microscopy, Electron, Scanning; Porosity; Rabbits; Silicates; Silicon; Tissue Engineering; Tissue Scaffolds

In the absence of any organic surfactants and solvents, the silicon (Si) and strontium (Sr) co-substituted hydroxyapatite [Ca10(PO4)6(OH)2, Si/Sr-HAp] nanowires were synthesized via hydrothermal treatment of the Sr-containing calcium silicate (Sr-CS) powders as the precursors in trisodium phosphate (Na3PO4) aqueous solution. The morphology, phase, chemical compositions, lattice constants and the degradability of the products were characterized. The Si/Sr-HAp nanowires with diameter of about 60nm and up to 2μm in length were obtained after hydrothermal treatment of the Sr-CS precursors. The Sr and Si substitution amount of the HAp nanowires could be well regulated by facile tailoring the Sr substitution level of the precursors and the reaction ratio of the precursor/solution, respectively. The SiO4 tetrahedra and Sr(2+) ions occupied the crystal sites of the HAp, and the lattice constants increased apparently with the increase of the substitution amount. EDS mapping also suggested the uniform distribution of Si and Sr in the synthetic nanowires. Moreover, the Si/Sr-substitution apparently improved the degradability of the HAp materials. Our study suggested that the precursor transformation method provided a facile approach to synthesize the Si/Sr co-substituted HAp nanowires with controllable substitution amount, and the synthetic Si/Sr-HAp nanowires might be used as bioactive materials for hard tissue regeneration applications.

Topics: Calcium Compounds; Crystallization; Durapatite; Ions; Nanowires; Particle Size; Phosphates; Silicates; Silicon; Strontium; Temperature; Water

This study investigated that calcium silicate (CS) cement may influence the behavior of human dental pulp cells (hDPCs) via mitogen-activated protein kinase pathway, in particular p38. We have addressed that Si ion released from CS cement can influence osmolarity in the medium, which may stimulate hDPC viability and induce angiogenesis-related proteins through stimulation of the nitric oxide synthase and nitric oxide secretion.. The hDPCs was cultured with CS cement to angiogenesis. Then, cell viability, ion concentration, osmolality, nitric oxide secretion, the von Willebrand factor, and angiopoietin-1 protein expression were examined.. CS cement elicited a significant (P < .05) increase of 15%, 20%, and 19% in viability compared with control on days 1, 3, and 5 of cell seeding, respectively. The CS cement consumed calcium and phosphate ions and released more Si ions in medium. The CS significantly (P < .05) increased the osmolality to 303.52 ± 3.07, 315.03 ± 5.80, and 319.95 ± 4.68 mOsm/kg for 1, 3, and 5 days, respectively. P38 was activated through phosphorylation; the phosphorylation kinase was investigated in our cell system after culture with CS cement. Moreover, expression levels for angiopoietin-1 and von Willebrand factor in hDPCs on CS cement were higher than those of the CS + p38 inhibitor (SB203580) group (P < .05) at all of the analyzed time points.. This study showed that CS cement was able to activate the p38 pathway in hDPCs cultured in vitro. Moreover, Si was shown to increase osmolality required to facilitate the angiogenic differentiation of hDPCs via the p38 signaling pathway. When the p38 pathway was blocked by SB203580, the angiogenic-dependent protein secretion was decreased. These findings verified that the p38 pathway plays a key role in regulating the angiogenic behavior of hDPCs cultured on CS cement.

Topics: Angiogenic Proteins; Angiopoietin-1; Calcium; Calcium Compounds; Cell Culture Techniques; Cell Survival; Cells, Cultured; Dental Pulp; Free Radical Scavengers; Humans; Imidazoles; MAP Kinase Signaling System; Nitric Oxide; Nitric Oxide Synthase Type III; Osmolar Concentration; p38 Mitogen-Activated Protein Kinases; Phosphates; Pyridines; Silicate Cement; Silicates; Silicon; Time Factors; von Willebrand Factor

In this study, a nanocalcium silicate (n-CS)/polyetheretherketone (PEEK) bioactive composite was prepared using a process of compounding and injection-molding. The mechanical properties, hydrophilicity, and in vitro bioactivity of the composite, as well as the cellular responses of MC3T3-E1 cells (attachment, proliferation, spreading, and differentiation) to the composite, were investigated. The results showed that the mechanical properties and hydrophilicity of the composites were significantly improved by the addition of n-CS to PEEK. In addition, an apatite-layer formed on the composite surface after immersion in simulated body fluid (SBF) for 7 days. In cell culture tests, the results revealed that the n-CS/PEEK composite significantly promoted cell attachment, proliferation, and spreading compared with PEEK or ultrahigh molecular weight polyethylene (UHMWPE). Moreover, cells grown on the composite exhibited higher alkaline phosphatase (ALP) activity, more calcium nodule-formation, and higher expression levels of osteogenic differentiation-related genes than cells grown on PEEK or UHMWPE. These results indicated that the incorporation of n-CS to PEEK could greatly improve the bioactivity and biocompatibility of the composite. Thus, the n-CS/PEEK composite may be a promising bone repair material for use in orthopedic clinics.

Topics: 3T3 Cells; Animals; Anthraquinones; Apatites; Benzophenones; Biocompatible Materials; Bone Regeneration; Calcium Compounds; Cell Adhesion; Cell Differentiation; Cell Proliferation; Ketones; Mice; Microscopy, Electron, Scanning; Nanoparticles; Osteogenesis; Polyethylene; Polyethylene Glycols; Polymers; Silicates; Silicon; Spectroscopy, Fourier Transform Infrared; Stress, Mechanical; X-Ray Diffraction

This study examines how calcium silicate cement extracts influence the behavior of human dental pulp cells (hDPCs) through calcium channels and active mitogen-activated protein kinase pathways, in particular extracellular signal-related kinase (ERK).. HDPCs are treated with various silicon concentrations both with and without verapamil, after which the cells' viability and odontogenic differentiation markers are determined by using PrestoBlue assay and Western blot, respectively.. The silicon promoted cell proliferation and inhibited calcium channel blockers. It was also found that silicon increased ERK and p38 activity in a dose-dependent manner. Furthermore, it raised the expression and secretion of alkaline phosphatase, osteocalcin, dentin sialophosphoprotein, and dentin matrix protein-1. In addition, statistically significant differences (P < .05) have been found in the secretion of osteocalcin in ERK inhibitor + verapamil between the silicon concentrations; these varations are dose-dependent and indicate that ERK signaling is involved in the silicon-induced odontogenic differentiation of hDPCs.. The current study shows that silicon ions released from calcium silicate substrates play a key role in odontoblastic differentiation of hDPCs through calcium channels and modulate ERK activation.

Topics: Alkaline Phosphatase; Aluminum Compounds; Calcium Channel Blockers; Calcium Channels; Calcium Compounds; Cell Culture Techniques; Cell Differentiation; Cell Survival; Cells, Cultured; Dental Pulp; Dose-Response Relationship, Drug; Drug Combinations; Extracellular Matrix Proteins; Extracellular Signal-Regulated MAP Kinases; Flavonoids; Humans; MAP Kinase Signaling System; Odontogenesis; Osteocalcin; Oxides; p38 Mitogen-Activated Protein Kinases; Phosphoproteins; Protein Kinase Inhibitors; Sialoglycoproteins; Silicate Cement; Silicates; Silicon; Verapamil

To compare white ProRoot MTA (WMTA), EndoSequence BC sealer (BC sealer) and Biodentine with regard to their ability to produce apatites and cause Ca and Si incorporation in adjacent human root canal dentine after immersion in phosphate-buffered saline (PBS).. Root sections of human single-rooted teeth were filled with one of the materials and immersed in PBS for 1, 7, 30 or 90 days (n = 5 each). Morphology and elemental composition of surface precipitates and interfacial dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Ca- and Si-incorporation depths in the interfacial dentine were measured. In addition, the amount of Ca ions released from the test materials was measured by EDTA titration.. All materials produced surface precipitates of acicular or lath-like morphology with Ca/P ratio of 1.6 : 2.0. Within dentinal tubules, the three materials formed tag-like structures that were frequently composed of Ca- and P-rich and Si-poor materials, suggesting intratubular precipitation. Ca- and Si-incorporation depths were in the order of Biodentine > WMTA > BC sealer, with a significant difference between BC sealer and the others at several time-points (P < 0.05, anova and Tukey's honestly significant difference test). The concentration of released Ca ions was in the order of Biodentine > WMTA > BC sealer with significant differences between the materials (P < 0.05).. Compared with Biodentine and WMTA, BC sealer showed less Ca ion release and did not show Ca and Si incorporation as deeply in human root canal dentine when immersed in PBS for up to 90 days.

Topics: Aluminum Compounds; Apatites; Biocompatible Materials; Buffers; Calcium; Calcium Compounds; Calcium Phosphates; Chemical Precipitation; Dental Pulp Cavity; Dentin; Drug Combinations; Electron Probe Microanalysis; Humans; Materials Testing; Oxides; Phosphorus; Root Canal Filling Materials; Silicates; Silicon; Sodium Chloride; Spectrometry, X-Ray Emission; Tantalum; Time Factors; Zirconium

Bioceramic samples with osteogenic properties, suitable for use in the regeneration of hard tissue, were synthesized. The materials consisting of α-tricalcium phosphate (αTCP) and also αTCP doped with either 1.5 wt.% or 3.0 wt.% of dicalcium silicate (C2S) in the system Dicalcium Silicate-Tricalcium Phosphate (C2S-TCP) were obtained by solid state reaction. All materials were composed of a single phase, αTCP in the case of a pure material, or solid solution of C2S in αTCP (αTCPss) for the doped αTCP. Viability, proliferation and in vitro osteoinductive capacity were investigated by seeding, adult mesenchymal stem cells of human origin (ahMSCs) which were CD73(+), CD90(+), CD105(+), CD34(-) and CD45(-) onto the 3 substrates for 30 days. Results show a non-cytotoxic effect after applying an indirect apoptosis test (Annexin V/7-AAD staining), so ahMSCs adhered, spread, proliferated and produced extracellular matrix (Heparan-sulfate proteoglycan (HS) and osteopontin (OP)) on all the ceramics studied. Finally, the cells lost the cluster differentiation marker expression CD73, CD90 y CD105 characteristic of ahMSCs and they showed an osteoblastic phenotype (Alkaline phosphatase activity (ALP), Osteocalcin production (OC), Collagen type I expression (Col-I), and production of mineralization nodules on the extracellular matrix). These observations were more evident in the αTCP ceramic doped with 1.5 wt.% C2S, indicating osteoblastic differentiation as a result of the increased concentration of solid solution of C2S in αTCP (αTCPss). Overall, these results suggest that the ceramics studied are cytocompatible and they are able to induce osteoblastic differentiation of undifferentiated ahMSCs.

Topics: Adult; Adult Stem Cells; Alkaline Phosphatase; Apoptosis; Calcium; Calcium Compounds; Calcium Phosphates; Cell Adhesion; Cell Differentiation; Cell Proliferation; Cell Survival; Cells, Cultured; Ceramics; Chemical Phenomena; Culture Media; Humans; Materials Testing; Mechanical Phenomena; Mesenchymal Stem Cells; Osteocalcin; Phosphorus; Silicates; Silicon

This study investigated whether calcium silicate cement extract exerted antiosteoclastogenic actions in murine RAW 264.7 macrophages cultured with receptor activator for nuclear factor kappaB (RANKL).. The RAW 264.7 macrophage cell was treated with RANKL to osteoclastogenesis. Then, cell viability, cell death, and cathepsin K expression were examined.. The silicon (Si)-inhibited RANKL-induced formation of osteoclasts during the osteoclast differentiation process. It was also found that ≥4 mmol/L Si reduced RANKL-enhanced tartrate-resistant acid phosphatase (TRAP) activity in a dose-dependent manner. Furthermore, Si diminished the expression and secretion of cathepsin K elevated by RANKL and was concurrent with the inhibition of TRAF6 induction and nuclear factor kappaB activation.. The current report shows that silicate abrogated RANKL-induced osteoclastogenesis by retarding osteoclast differentiation. The Si can modulate every cell through dose-dependent in vitro RANKL-mediated osteoclastogenesis, such as the proliferation and fusion of preosteoclasts, and the function of osteoclasts. Therefore, silicate-based materials may be a potential therapeutic agent targeting osteoclast differentiation in bone defects.

Topics: Acid Phosphatase; Aluminum Compounds; Animals; Calcium Compounds; Cathepsin K; Cell Culture Techniques; Cell Death; Cell Differentiation; Cell Line; Cell Proliferation; Cell Survival; Culture Media; Dose-Response Relationship, Drug; Drug Combinations; Isoenzymes; Macrophages; Materials Testing; Mice; NF-kappa B; Osteoclasts; Oxides; RANK Ligand; Silicate Cement; Silicates; Silicon; Spectrophotometry, Atomic; Tartrate-Resistant Acid Phosphatase; TNF Receptor-Associated Factor 6

Bioceramics are currently in use to cover bone defects in orthopedics and craniofacial surgery. But their compatibility and efficacy in cranium were not investigated in detail. The aims of this study were to produce, characterize, and assess the biocompatibility and osteointegration of Si-HA, Si-Sr-HA, HA-Wollastonite, and HA-Wollastonite-Frit bioceramics.. Bioceramics were implanted into the burr holes of 14 craniotomy patients who were followed up from three to 24 months. Radiologic and scintigraphic examinations were performed.. Osteoblastic activity quantified by scintigraphy increased from 6.865 to 22.991±1.682 from four to eight months in the HA-Woll group. Adding fritt into HA-Woll decreased osteoblastic activity at 10 months. Si-Sr-HA displayed significantly higher osteoblastic activity when compared to the craniotomy site at 12 months. The scintigraphic ratio of the bioceramic implanted regions to the craniotomy sites varied between 1.10 and 1.57. Osteoblast formation and establishment of the trabecular pattern of bone was observed in the surroundings of bioceramics in two patients.. These bioceramics can be safely used to cover the burr holes of craniotomy patients, as well as to close the cranial bone defects.

Topics: Adolescent; Adult; Bone and Bones; Bone Substitutes; Calcium Compounds; Craniotomy; Durapatite; Female; Humans; Male; Middle Aged; Osteoblasts; Osteogenesis; Silicates; Silicon; Skull; Strontium; Tomography, X-Ray Computed; Young Adult

Taking into account the phase equilibrium relationships within the Ca3(PO4)2-CaSiO3-CaMg(SiO3)2 ternary system, three bioactive glasses with a eutectic composition and analogous amounts of Ca3(PO4)2 (∼40 wt.%) have been prepared. The structure of the glasses was investigated by 31P and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The glasses exhibited thermal expansion coefficients (50-600 °C) of 11.8-13.3×10(-6) °C(-1), a glass transition temperature of 790-720 °C and a softening temperature of 811-750 °C. The mechanical properties of the glasses were as follows: bending strength ∼100 MPa, Young's modulus 94-83 GPa, Vickers microhardness 7.1-4.1 GPa and toughness 0.8 MPa m1/2. The bioactive properties were discussed in terms of their structure deduced by MAS-NMR spectroscopy and the field strength of the network modifiers (Mg2+ and Ca2+). A knowledge of the glass structure was important in predicting its bioactivity.

Topics: Biocompatible Materials; Calcium Compounds; Calcium Phosphates; Differential Thermal Analysis; Elastic Modulus; Glass; Magnetic Resonance Spectroscopy; Materials Testing; Mechanical Phenomena; Microscopy, Electron, Scanning; Models, Chemical; Phase Transition; Silicates; Silicon; Spectrometry, X-Ray Emission; Temperature; X-Ray Diffraction

To examine the effects of altering the Si/Ca molar ratio (6 : 4, 5 : 5, and 4 : 6) of a quick-setting calcium silicate cement on in vitro cell attachment.. Working time and setting time of three different calcium silicate cements were measured. Alamar Blue was used for real-time and repeated monitoring of cell attachment and proliferation. The Si and Ca ion concentrations of the cell culture medium in the presence of three different calcium silicate cements seeded with MG63 cells were measured. Kinetic immunofluorescent staining of MG63 cells was performed during cell attachment and spreading. Reverse transcription-polymerase chain reaction was employed to determine gene expression in MG63 cells cultured on the cements. One-way analysis of variance was used to evaluate the significance of the differences between the mean values.. The working time (4-7 min) and setting time (17-24 min) of the cements were shortened with an increase in the Ca content of the calcium silicate powders after mixing the powder with water. In contrast, the higher the Si content in the cement, the more the MG63 cells attached to the cement at all culture time-points, accompanying by the formation of more obvious actin stress fibres. Cell proliferation and differentiation increased significantly (P < 0.05) with an increase in the Si content of the calcium silicate cements. Si ion concentration of the culture medium increased significantly (P < 0.05) with increasing cement Si content and culture time-points.. The higher Si content cement enhanced the higher expression of cell attachment, proliferation and differentiation as compared to the lower Si content cement.

Topics: Actins; Alkaline Phosphatase; Calcium; Calcium Compounds; Cell Adhesion; Cell Culture Techniques; Cell Differentiation; Cell Line; Cell Movement; Cell Proliferation; Culture Media, Conditioned; Dental Cements; Fluorescent Dyes; Humans; Materials Testing; Microscopy, Fluorescence; Osteoblasts; Osteogenesis; Reverse Transcriptase Polymerase Chain Reaction; Silicates; Silicon; Time Factors

This work describes the evaluation of three ceramic materials as potential osteogenic substrate for bone tissue engineering. The capacity of adult human mesenchymal stem cells cultured under experimental conditions known to adhere, proliferate and differentiate into osteoblasts was studied. Two types of culture medium: growth medium and osteogenic medium were evaluated. The materials were pure α-tricalcium phosphate and also αTCP doped with either 1.5 or 3 wt% of dicalcium silicate. The results showed that the hMSCs cultured adhered, spread, proliferated and produced mineralized extracellular matrix on all the ceramics studied. They showed an osteoblastic phenotype, especially in the αTCP doped with 1.5 wt% C(2)S, indicating osteoblastic differentiation as a result of the increased concentration of silicon in solid solution in TCP. Ceramics evaluated in this work are bioactive, cytocompatible and capable of promoting the differentiation of hMSCs into osteoblast.

Topics: Adult; Biocompatible Materials; Bone and Bones; Calcium Compounds; Calcium Phosphates; Cell Adhesion; Cell Culture Techniques; Cell Proliferation; Ceramics; Extracellular Matrix; Female; Humans; Male; Materials Testing; Mesenchymal Stem Cells; Osteoblasts; Silicates; Silicon; Tissue Engineering; X-Ray Diffraction

Zirconium oxide can be added to dental materials rendering them sufficiently radiopaque. It can thus be used to replace the bismuth oxide in mineral trioxide aggregate (MTA). Replacement of Portland cement with 30% zirconium oxide mixed at a water/cement ratio of 0.3 resulted in a material with adequate physical properties. This study aimed at investigating the microstructure, pH and leaching in physiological solution of Portland cement replaced zirconium oxide at either water-powder or water-cement ratios of 0.3 for use as a root-end filling material. The hydration characteristics of the materials which exhibited optimal behavior were evaluated.. Portland cement replaced by zirconium oxide in varying amounts ranging from 0 to 50% in increments of 10 was prepared and divided into two sets. One set was prepared at a constant water/cement ratio while the other set at a constant water/powder ratio of 0.3. Portland cement and MTA were used as controls. The materials were analyzed under the scanning electron microscope (SEM) and the hydration products were determined. X-ray energy dispersive analysis (EDX) was used to analyze the elemental composition of the hydration products. The pH and the amount of leachate in Hank's balanced salt solution (HBSS) were evaluated. A material that had optimal properties that satisfied set criteria and could replace MTA was selected. The microstructure of the prototype material and Portland cement used as a control was assessed after 30 days using SEM and atomic ratio diagrams of Al/Ca versus Si/Ca and S/Ca versus Al/Ca were plotted.. The hydration products of Portland cement replaced with 30% zirconium oxide mixed at water/cement ratio of 0.3 were calcium silicate hydrate, calcium hydroxide and minimal amounts of ettringite and monosulphate. The calcium hydroxide leached in HBSS solution resulted in an increase in the pH value. The zirconium oxide acted as inert filler and exhibited no reaction with the hydration by-products of Portland cement.. A prototype dental material composed of Portland cement replaced with 30% zirconium oxide as radiopacifier leached calcium ions on hydration which reacted with phosphates present in simulated tissue fluids. This resulted in bioactive cement that could prospectively be used as a root-end filling material. The zirconium oxide acted as inert filler and did not participate in the hydration reaction of the Portland cement.

Topics: Aluminum; Aluminum Compounds; Biocompatible Materials; Bismuth; Calcium; Calcium Compounds; Calcium Hydroxide; Chemical Phenomena; Diffusion; Drug Combinations; Humans; Hydrogen-Ion Concentration; Isotonic Solutions; Materials Testing; Microscopy, Electron, Scanning; Oxides; Phosphorus; Powders; Root Canal Filling Materials; Silicate Cement; Silicates; Silicon; Sodium; Spectrometry, X-Ray Emission; Sulfur; Surface Properties; Water; Zirconium

To compare Biodentine and White ProRoot mineral trioxide aggregate (MTA) with regard to Ca and Si uptake by adjacent root canal dentine in the presence of phosphate-buffered saline (PBS).. Root canals of bovine incisor root segments were instrumented, filled with either Biodentine or MTA (n = 20 each) and then immersed in Ca-and Mg-free PBS for 1, 7, 30 or 90 days (n = 5 each). Unfilled, unimmersed dentine specimens (n = 5) served as controls. The specimens were sectioned longitudinally, and the ultrastructure of the dentine-material interface and the elemental composition/distribution in the material-adjacent dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Data were statistically analyzed using one-way anova and Tukey's honestly significant difference test or the Mann-Whitney U-test.. Along the material-dentine interface, both materials formed a tag-like structure that was composed of either Ca- and P-rich crystalline deposits or the material itself. The width of a Ca- and Si-rich layer detected along the dentine layer of the material-dentine interface showed increases over time. The Ca- and Si-rich layer width was significantly larger (P < 0.05) in Biodentine than MTA at 30 and 90 days.. Both Biodentine and MTA caused the uptake of Ca and Si in the adjacent root canal dentine in the presence of PBS. The dentine element uptake was more prominent for Biodentine than MTA.

Topics: Aluminum Compounds; Animals; Calcium; Calcium Compounds; Carbon; Cattle; Crystallization; Dental Pulp Cavity; Dentin; Diffusion; Drug Combinations; Electron Probe Microanalysis; Humidity; Hydrogen-Ion Concentration; Image Processing, Computer-Assisted; Immersion; Microscopy, Electron, Scanning; Oxides; Oxygen; Phosphorus; Root Canal Filling Materials; Root Canal Preparation; Silicates; Silicon; Spectrometry, X-Ray Emission; Time Factors; Water

We report the effects of two pseudowollastonite (beta-CaSiO(3)) substrates on the attachment, viability, proliferation and osteogenic differentiation of human mesenchymal stem cells (hMSCs), and provide detailed mechanistic links of surface texture, soluble factors and culture media to cell activities. Cell attachment and viability were lower for psWf (fine-grained, roughness 0.74 microm) than for psWc (coarse-grained, roughness 1.25 microm) surface, and were ascribed to the greater specific area of the finer psWf particles resulting in higher release rate of Si, which is cytotoxic at high levels. Interestingly, proliferation was greater on psWf. Osteogenic differentiation occurred on both surfaces, indicated by calcium phosphate bone nodule formation and by osteocalcin, osteopontin and core-binding factor alpha-1 gene expression. Gene levels were lower on psWf than on psWc at day 8 in growth medium, explained by differences in Ca and/or Si concentrations between the two surfaces. Similar gene expression on both surfaces at day 16 in both growth and osteogenic induction media was attributed to pro-osteogenic effects of Ca and P at specific concentrations and complementary Ca and P levels on the two surfaces. In summary, soluble factors from substrates may be more important for osteogenic differentiation in growth medium than small surface roughness variations within a factor of 2. Optimum concentration ranges exist for individual soluble factors to balance cell toxicity/growth versus osteogenic differentiation, and soluble factors together have complex, cooperative or opposing, effects on a given cell activity.

Topics: Animals; Biomarkers; Calcium; Calcium Compounds; Cell Adhesion; Cell Culture Techniques; Cell Differentiation; Cell Proliferation; Cell Shape; Cell Survival; Cells, Cultured; Ceramics; Core Binding Factor Alpha 1 Subunit; Culture Media; Gene Expression; Humans; Mesenchymal Stem Cells; Osteocalcin; Osteogenesis; Osteopontin; Phosphorus; Silicates; Silicon; Surface Properties

The addition of a water-soluble polymer to mineral trioxide aggregate (MTA), which to date has been used primarily to seal lateral root perforations and as a root-end filling material, resulted in material that is suitable for use as an endodontic sealer.. MTA was mixed with water at powder/liquid ratios of 4 and 3.33 and an addition of 2 microL to 20 microL of water-soluble polymer. The materials were tested for flow and film thickness, and the optimal quantity of polymer required to conform to EN ISO 6876 Section 4.3.1, 4.3.4 (2002) was determined. The resultant MTA sealer was tested for radiopacity using methods suggested by ISO 6876 (2002) using pulp canal sealer (PCS) as control. The effect of polymer addition on the hydration characteristics of the MTA and calcium silicate cement was evaluated by assessing paste microstructure under the scanning electron microscope after 30 days and by collecting 50 quantitative analyses of the hydration products and plotting the data as atomic ratios. Plots of Al/Ca versus Si/Ca and S/Ca and Al/Ca were drawn.. High additions of polymer were required for the flow and film thickness of MTA to conform to ISO 6876 (2002). The resultant cement sealer had a lower radiopacity than PCS but greater than the 3-mm thickness of Al specified by the international standard. The addition of polymer did not modify the hydration mechanism of MTA.. The addition of a water-soluble polymer to MTA did not alter the hydration characteristics of the material and resulted in a material with improved properties suitable for use as endodontic sealer cement.

Topics: Aluminum; Aluminum Compounds; Calcium; Calcium Compounds; Contrast Media; Dental Cements; Drug Combinations; Electron Probe Microanalysis; Humans; Materials Testing; Microscopy, Electron, Scanning; Oxides; Polymers; Rheology; Root Canal Filling Materials; Silicates; Silicon; Solubility; Sulfur; Surface Properties; Time Factors; Viscosity; Water

In this work, gentamicin loaded collagen was grafted on the surface of plasma sprayed wollastonite coatings to obtain an implant having excellent bioactivity and cytocompatibility as well as antibacterial property. The bioactivity and cytocompatibility of the wollastonite coatings grafting gentamicin loaded collagen were examined by simulated body fluid (SBF) soaking test and in vitro cell culture test. The release rate of gentamicin from collagen was measured using UV spectrophotometer in phosphate-buffered saline (PBS) and the antibacterial activity against Staphylococcus aureus (S. aureus) was evaluated by zone of inhibition test and bacterial counting method. The results showed that a composite layer with collagen and silicon-rich particles was formed on the surface of the coating after the graft of collagen. The grafted collagen layer mixed with silicon-rich particles could induce the precipitation of apatite after soaking in SBF for 14 days and improved the cellular proliferation on wollastonite coatings. The release of gentamicin from the collagen layer sustained 11 days in PBS and effectively inhibited the growth of S. aureus. In conclusion, the wollastonite coating grafting gentamicin loaded collagen had excellent bioactivity and cytocompatibility as well as good antibacterial properties, which would be beneficial for the long term stability and surgical success rate of implants.

Topics: Anti-Bacterial Agents; Body Fluids; Calcium; Calcium Compounds; Cell Proliferation; Cells, Cultured; Coated Materials, Biocompatible; Collagen; Colony Count, Microbial; Drug Carriers; Gentamicins; Humans; Materials Testing; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Osteoblasts; Silicates; Silicon; Spectroscopy, Fourier Transform Infrared; Staphylococcus aureus; Surface Properties; Tissue Engineering

Pseudowollastonite ceramics (beta-CaSiO3) from synthetic and natural sources were assessed with regard to their properties relevant to biomedical applications. Synthetic and natural CaSiO3 powders, with average particle size of 1.6 and 13.2 microm, respectively, were first employed. Powders were pressed and sintered at 1400 degrees C for 2 h. Pseudowollastonite was the only crystalline phase in sintered materials. Glassy phase, eight times more abundant in sintered natural wollastonite (SNW) than in the synthetic one (SSW), was observed in grain boundaries and in triple points. Larger grains and bigger and more abundant pores were present in SNW, resulting in lower diametral tensile strength (26 MPa), than in SSW (42 MPa). However, by milling the natural wollastonite starting powder to a particle size of 2.0 microm and sintering (SNW-M), the microstructure became finer and less porous, and diametral tensile strength increased (48 MPa). Weibull modulus of SNW and SNW-M samples was twice that of the SSW. All the samples released Si and Ca ions, and removed phosphate ions from simulated body fluid in similar amounts and were completely coated by apatite-like spherules after soaking in simulated body fluid for 3 wk. The aqueous extracts from all samples studied were not cytotoxic in a culture of human fibroblastic cells. No differences in fibroblast-like human cells adhesion and proliferation were observed between samples. According to the obtained results, properly processed pseudowollastonite bioceramics, obtained from the natural source, exhibit the same in vitro behavior and better performance in terms of strength and reliability than do the more expensive synthetic materials.

Topics: Biocompatible Materials; Body Fluids; Calcium; Calcium Compounds; Cell Death; Cells, Cultured; Ceramics; Compressive Strength; Fibroblasts; Humans; Hydrogen-Ion Concentration; Materials Testing; Microscopy, Electron, Scanning; Phosphorus; Silicates; Silicon; Temperature; X-Ray Diffraction

Composite scaffolds of poly(D,L-lactic acid) (PDLLA) with bioactive wollastonite were fabricated by the conventional solvent casting-particulate leaching method. The pore structures and morphology of the scaffolds were determined by scanning electron microscopy (SEM). The bioactivity of the composites was evaluated by soaking in a simulated body fluid (SBF), and the formation of the hydroxyapatite (HAp) layer was determined by SEM and energy-dispersive spectrometer. The results showed that the wollastonite/PDLLA composites were bioactive as it induced the formation of HAp on the surface of the composite scaffolds after soaking in SBF for seven days. In addition, pH and ion concentration changes of SBF solutions with composite scaffolds were examined. The results showed that the composites could release Ca and Si ions, which could neutralize the acidic degradation by-products of the PDLLA, and stabilize the pH of the SBF solutions between 6.7 and 7.2 within a three-week soaking period. Furthermore, the measurements of the water contact angles suggested that incorporation of wollastonite into PDLLA could improve the hydrophilicity of the composites and the enhancement was dependent on the wollastonite content. All these results suggest that incorporation of wollastonite into PDLLA might be a useful approach for the preparation of composite scaffolds for tissue repair and tissue-engineering applications.

Topics: Biocompatible Materials; Calcium; Calcium Compounds; Hydrogen-Ion Concentration; Hydroxyapatites; Ions; Lactic Acid; Microscopy, Electron, Scanning; Polyesters; Polymers; Silicates; Silicon; Spectrophotometry; Surface Properties; Time Factors; Tissue Engineering

In vitro experiments show that pseudowollastonite (alpha-CaSiO3) is a highly bioactive material that forms a hydroxyapatite surface layer on exposure to simulated body fluid and also to human parotid saliva. This finding is very significant, as it indicates that the pseudowollastonite can be physically and chemically integrated into the structure of living bone tissue, and therefore could be suitable for repair or replacement of living bone. The physical and chemical nature of the remodelled interface between the pseudowollastonite implants and the surrounding bone has been studied after in vivo implantation of 20 pseudowollastonite cylinders into rat tibias. The interfaces formed after 3, 6, 8 and 12 weeks of implantation were examined histologically using an optical microscope and also by analytical scanning electron microscopy. SEM and X-ray elemental analysis showed that the new bone was growing in direct contact with the implants. Other examinations found that the bone was fully mineralized. The ionic exchange taking place at the implant interface with the body fluids was essential in the process of the implant integration through a dissolution-precipitation-transformation mechanism. The study found the interface biologically and chemically active over the 12-week implantation period. The rate of new bone formation decreased after the first 3 weeks and reached constant value over the following 9 weeks. The osteoblastic cells migrated towards the interface and colonized the surface at the contact areas with the cortical regions and also bone marrow.

Topics: Animals; Bone and Bones; Bone Substitutes; Calcium; Calcium Compounds; Implants, Experimental; Microscopy, Electron; Phosphorus; Rats; Silicates; Silicon; Tibia; Time Factors

The inflammatory and fibrogenic potential of three naturally occurring and two man-made industrial minerals were compared. Groups of five rats each received respectively a single intratracheal instillation of saline (control), UICC chrysotile B asbestos, short chrysotile 4T30, attapulgite, xonotlite (a calcium silicate), and Fiberfrax (an aluminum silicate) at doses of 1, 5, and 10 mg. One month after the treatment, assessment of lung morphology and bronchoalveolar lavage were performed on each animal. Under these conditions, UICC chrysotile B at all doses tested (1, 5, and 10 mg) induced fibrotic lesions in bronchiolar tissues while short chrysotile 4T30 (1, 5, and 10 mg) caused focal accumulation of inflammatory cells in the alveolar structures but no apparent fibrosis. Compared to these positive reactions with different fibrogenicity, xonotlite caused minimal inflammatory reactions detectable only at high dose (10 mg) and by bronchoalveolar analysis. By contrast, the rat lung reacted more significantly to attapulgite and Fiberfrax although the tissue reaction differed considerably for these two materials. While attapulgite, at doses up to 10 mg caused minimal reactions characterized by mononuclear cell infiltration mainly in the alveolar structures, Fiberfrax at 1 mg and higher caused significant granulomatous reactions and the appearance of early fibrosis. Overall the order of lung biological reactivity observed for the various silicates was xonotlite much less than attapulgite less than short chrysotile 4T30 less than Fiberfrax less than UICC chrysotile B. These observations indicate that Fiberfrax, attapulgite, and, to a lesser extent, xonotlite are biologically active within the time span studied and potentially deleterious for lung tissue.

Topics: Animals; Asbestos; Asbestos, Serpentine; Bronchoalveolar Lavage Fluid; Calcium Compounds; Dose-Response Relationship, Drug; Lung; Magnesium; Magnesium Compounds; Male; Pulmonary Fibrosis; Rats; Rats, Inbred Strains; Silicates; Silicic Acid; Silicon; Silicon Compounds; Silicon Dioxide; Specific Pathogen-Free Organisms; Time Factors

The membranolytic and cytotoxic properties of two naturally occurring (chrysotile asbestos; attapulgite clay) and two man-made (Fiberfrax, an aluminium-silicate, and xonotlite, a calcium silicate) industrial minerals were compared. "Short" fiber fractions of chrysotile and Fiberfrax were obtained by sedimentation in demineralized water, while the attapulgite and xonotlite samples were used as obtained. The aluminium silicate fibers were found to be non- hemolytic, while for the other three silicates, chrysotile had the strongest hemolysis potential, followed very closely by xonotlite; attapulgite was less hemolytic than the former two silicates, but was nevertheless highly hemolytic to the rat erythrocytes. Using rat pulmonary alveolar macrophages, the in vitro cytotoxicity assays showed that with fresh cell monolayers, all four silicates were equivalent in causing cell damages at a dose of 250 micrograms; at a lower dose (50 micrograms), the intensity of the cytotoxic effect was in the decreasing order: Fiberfrax greater than attapulgite greater than chrysotile greater than xonotlite. With one day-old cultured cell monolayers, a dose of 250 micrograms of the silicates fibers was less cytotoxic, with the exception of the attapulgite fibers which remained essentially as cytotoxic as with the fresh cell monolayers. The reduced cytotoxic response was especially noticeable with the chrysotile fibers. At 50 micrograms, the cytotoxicity scale of the mineral dusts with one day-old cell monolayers was essentially the same as the one obtained with the fresh cell monolayers, that is: Fiberfrax approximately equal to attapulgite greater than chrysotile greater than or equal to xonotlite. Overall, these in vitro tests imply: 1) that all four industrial silicates tested can be considered to be "biologically active"; 2) that on the basis of their different reactivities with the two types of cell culture conditions used, their biological reactivity in vivo might be quite distinct. This might be especially true for at least the chrysotile, attapulgite and xonotlite short fibers, considering that these three types of silicate dusts have very similar dimensions. Moreover, for the chrysotile and attapulgite samples, fiber numbers is probably not an important factor, since the density of the two silicates is roughly the same. The unaltered cytotoxic responses of the American attapulgite fibers in the two macrophage assays correlate well with the fact that short attapulgite f

Topics: Animals; Asbestos; Asbestos, Serpentine; Calcium Compounds; Cell Survival; Cells, Cultured; Dust; Hemolysis; L-Lactate Dehydrogenase; Lactates; Macrophages; Magnesium; Magnesium Compounds; Particle Size; Pulmonary Alveoli; Rats; Silicates; Silicic Acid; Silicon; Silicon Compounds; Silicon Dioxide

The biological activity of natural and synthetic mineral fibers has been examined. Natural attapulgite [(Mg, Al)2Si4O10(OH).4H2O], synthetic xonotlite [Ca3Si3O8(OH)2] and natural sepiolite [Mg2Si3O8.2H2O] were selected. Genotoxic effects were investigated by means of a well established cellular model based upon the measurement of unscheduled DNA synthesis (UDS) in rat hepatocytes in primary culture. The intrinsic capacity of the fibers (1 and 10 micrograms/ml) to induce UDS was first tested. None of the fiber types showed detectable UDS-eliciting activity. Also, the possible modulation of the cellular response to genotoxic agents by the materials was examined by exposing the cells to mixtures of 2-acetylaminofluorene (AAF) (0.05 and 0.25 micrograms/ml) and fibers (1 and 10 micrograms/ml). In these experiments, the UDS response was significantly diminished in the presence of xonotlite. This phenomenon may reflect changes in the uptake and/or metabolism of AAF or may result from an inhibition of DNA repair processes, the latter suggesting a possible cocarcinogenic potential for this synthetic silicate. These results point to the immediate necessity of studying more extensively the biological effects of fibrous materials that can be used as substitutes for asbestos.

Topics: Animals; Calcium Compounds; Liver; Magnesium; Magnesium Compounds; Magnesium Silicates; Male; Minerals; Mutagens; Rats; Rats, Inbred Strains; Silicates; Silicic Acid; Silicon; Silicon Compounds; Silicon Dioxide

Cellular interactions of a series of fibrous materials were examined by the use of a well established in vitro system. Primary cultures of hepatocytes were exposed to natural attapulgite, synthetic xonotlite and natural sepiolite. Ultrastructural analyses revealed that hepatocytes can engage in the phagocytosis of all 3 types of fibers over an exposure period of 20 h. Attapulgite fibers were found in plasma membrane invaginations, and deeper in the cytoplasm, in vesicles exhibiting various shapes. Xonotlite was also incorporated in plasma membrane invaginations; furthermore, these fibers were present in large vacuoles where they were circumscribed by membranes and appeared somewhat isolated from the cytoplasm. Sepiolite fibers were also taken up by the cells and could likewise be identified in the previously described structures. These observations point to the relevance of the hepatocyte model for investigating the effects of fibrous materials at the cellular level.

Topics: Animals; Calcium Compounds; In Vitro Techniques; Liver; Magnesium; Magnesium Compounds; Magnesium Silicates; Microscopy, Electron; Minerals; Phagocytosis; Rats; Silicates; Silicic Acid; Silicon; Silicon Compounds; Subcellular Fractions

Topics: Animals; Calcium; Calcium Compounds; Calcium, Dietary; Dust; Silicates; Silicon