Silicic Acid Research Articles

Native selenium in the apical rocks of the Gaisky copper-pyrite deposit

Research subject. Selenium mineralization in altered rocks of the Gaisky deposit. Aim. Determination of formation conditions of native selenium in altered rocks. Results. Selenium mineralization is established in three zones of altered rocks in the sides of the 3rd quarry and is confined to the upper part of the sulfur-quartz rocks. Layers with a high content of native selenium and tiemannite are distinguished by a carbon-black color against the general background of yellow-green sulfur-quartz rocks, forming subvertical trickle textures. The maximum propagation of selenium mineralization was found in the southwestern zone of the quarry. Here, selenium-containing rocks are traced vertically by 6 m, forming a lens with a diameter of up to 70 cm. The accumulation of selenium occurs due to its physical properties. Selenium is similar to sulfur in volatility, although it undergoes more intense condensation under decreased temperatures. The accumulation of selenium condensate is facilitated by a silicic acid gel, which prevents the removal of selenium by a hydrothermal flow. Conclusion. The native selenium of the Gaisky deposit is characterized by a hydrothermal genesis, which, along with the presence of monoclinic native sulfur in the rocks, indicates the hydrothermal formation of the entire complex of altered rocks.

Ortho-silicic Acid Prevents Glucocorticoid-Induced Femoral Head Necrosis by Promoting Akt Phosphorylation to Inhibit Endoplasmic Reticulum Stress-Mediated Apoptosis and Enhance Angiogenesis and Osteogenesis.

Glucocorticoid-induced osteonecrosis of the femoral head (SONFH) is the most prevalent form of secondary osteonecrosis affecting the femoral head. Glucocorticoids can cause damage to both vascular endothelial cells and osteoblasts. Previous studies have demonstrated that silicon can improve the resistance of vascular endothelial cells to oxidative stress and positively impact bone health. However, the impact of silicon on SONFH has yet to be investigated. We examined the influence of ortho-silicic acid (OSA, Si(OH)4) on the apoptosis and proliferation of vascular endothelial cells after glucocorticoid induction. Additionally, we evaluated the expression of apoptosis-related genes such as cleaved-caspase-3, Bcl-2 and Bax. The impact of glucocorticoids and OSA on the function of vascular endothelial cells was evaluated through wound healing, transwell and angiogenesis assays. Osteogenic function was subsequently evaluated through alizarin red staining, alkaline phosphatase staining and expression levels of osteogenic genes like RUNX2 and ALP. Moreover, we investigated the potential role of OSA in vivo using the SONFH animal model. At concentrations below 100μM, OSA exhibits no toxicity on vascular endothelial cells and effectively reverses glucocorticoid-induced apoptosis in these cells. OSA increases the resilience of vascular endothelial cells against oxidative stress and enhances osteoblast differentiation. Our study revealed that glucocorticoids activate endoplasmic reticulum stress, a process that mediates the apoptosis of vascular endothelial cells. OSA ameliorated the endoplasmic reticulum stress associated with glucocorticoids through the increased expression of p-Akt levels. In vivo, OSA treatment effectively improved SONFH by enhancing vascular endothelial cell function and promoting osteogenic differentiation. OSA counteracted the adverse effects of glucocorticoids both in vitro and in vivo, demonstrating a beneficial therapeutic effect on SONFH.

Experimental and computational evidence of U(VI)–OH–Si(OH)4 complexes under alkaline conditions: Implications for cement systems

The complexation of uranyl hydroxides with orthosilicic acid was investigated by experimental and theoretical methods. Spectroluminescence titration was performed in a glovebox under argon atmosphere at pH 9.2, 10.5 and 11.5, with [U(VI)] = 10−6 and 5 × 10−6 mol kgw−1. The polymerization effects of silicic acid were minimized by ruling out samples with less than 90 % monomeric silicic acid present, identified via UV–Vis spectrometry using the molybdate blue method. Linear regression analysis based on time-resolved laser-induced fluorescence spectroscopy (TRLFS) results yielded the conditional stepwise formation constants of U(VI)–OH–Si(OH)4 complexes at 0.05 mol kgw−1 NaNO3. The main spectroscopic features – characteristic peak positions and decay-time – are reported for the first time for the UO2(OH)2SiO(OH)3− species observed at pH 9.2 and 10.5 and UO2(OH)2SiO2(OH)22− predominant at pH 11.5. Quantum chemical calculations successfully computed the theoretical luminescence spectrum of the complex UO2(OH)2SiO(OH)3− species, thus underpinning the proposed chemical model for weakly alkaline systems. The conditional stability constants were extrapolated to infinite dilution using the Davies equation, resulting in log10β°(UO2(OH)2SiO(OH)3−) and log10β°(UO2(OH)2SiO2(OH)22−). Implications for U(VI) speciation in the presence and absence of competing carbonate are discussed for silicate-rich environments expected in certain repository concepts for nuclear waste disposal.

Hydrothermal precipitation of hematite from the model solution of zinc hydrometallurgical extraction

Abstract The effect of temperature and silicon concentration on iron precipitation and morphology of hematite particles was discussed. The results showed that increase of initial silicon centration will lead to the decrease of iron removal efficiency, and the Fe content decreases and S content increases in hematite. Increasing temperature is beneficial to increase iron removal rate and Fe content in hematite, but increasing temperature can not decrease silicon content in hematite. The content of Si in precipitate is proportional to the concentration of silicon in solution. Silicon is adsorbed on the surface of hematite in the form of silicic acid. Hematite particle was agglomerated microsphere. Increasing concentration of silicon will increase the disorder degree of hematite crystallization. With the increase of silicon concentration, the agglomeration of hematite particle was more obvious, and the average particle size of hematite particles increased. At 175 °C, the morphology of iron precipitation particles are composed of flake particles and rhomboid massive particles, but when the temperature rises to 195 °C, the agglomeration phenomenon is obvious, small flake particles agglomerate into microspherical aggregates.

Tolerability of silica microparticle gels as drug delivery vehicles

Aims/Purpose: Over the past decades, polymeric particles have become widespread in the field of drug delivery. Silica microparticles (SiMPs) are biodegradable—silicic acid being the main degradation product—and can release medication sustainably for a long period of time. Our aim was to determine the effects of soluble silicic acid on in vitro models of human epithelial cells.Methods: HCE‐2 and ARPE‐19 cells were exposed to serial dilutions of silicic acid produced by dissolving silica hydrogel in PBS, and cell viability was assessed after 24, 48 and 72 h of incubation. Cell viability data were provided by AlamarBlue assay, while membrane integrity was analysed through LDH release. For more information on the silicic acid impact on cellular stress, we assayed biochemical markers, such as IL‐6, IL‐8, MCP‐1, Caspase‐3 and Hsp‐70, using specific ELISAs.Results: AlamarBlue assay did not show any statistical differences in survival rate between the control group and maximum 30 μg/mL silicic acid in all timepoints in ARPE‐19 cells (24 h 95.42 ± 4.81%, 48 h 87.55 ± 6.48% and 72 h 97.64 ± 6.38%) and HCE‐2 cells (24 h 97.38 ± 5.97%, 48 h 100.81 ± 8.32% and 72 h 101.73 ± 2.62%). Additionally, we did not detect any toxic changes in LDH release test in ARPE‐19 cells in 24, 48 and 72 h time points (30 μg/mL silicic acid: 24 h 9.0 ± 11.5%, 48 h 10.4 ± 13.4% and 72 h 13.8 ± 16.6%). The LDH release data in treated (max. 30 μg/mL) HCE‐2 cells were comparable to control cells. Assessed inflammatory markers mostly were similar as well when comparing control and treatment groups, although IL‐6, MCP‐1, Caspase‐3 and Hsp‐70 showed increased values with time.Conclusions: Our results do not show major cytotoxicity of silicic acid on the two different epithelial cell lines, nor did not induce stress or inflammatory markers. Therefore, these findings support the use of our novel SiMPs as drug delivery vehicles in the treatment of ophthalmic diseases.

Determination and assessment of healing properties based on chemical analysis of spring waters in Jizzakh (Uzbekistan)

About 400 water samples were taken from the springs of Forish, Bakhmal, Zomin area and checked for organic matter, bromine, iodine, total mineralization, silicic acids, dissolved free carbon dioxide, total hardness. According to the results of the research, 60 springs met the requirements for healing water, that is, 9 springs with the required amount of total mineralization in the water, 1 spring rich in iron, 4 springs with bromine, and the iodine content is the highest. There was 1 spring, the number of springs rich in carbon dioxide dissolved in water was 26, and the number of springs rich in organic matter was 19. These chemical indicators are considered an important therapeutic factor in improving human health, in particular, peripheral nervous system, skin, gynecology, support and movement organs, metabolism, digestive system, urology, cardiovascular system, liver, biliary tract, urology.

Enhancing salt stress tolerance of forage sorghum by foliar application of ortho-silicic acid

Enhancing salt stress tolerance of forage sorghum by foliar application of ortho-silicic acid

From silicon to silica: a green chemistry approach for hollow sphere nanoparticle formation.

Herein we report on an environmentally friendly and scalable production route for hollow silica spheres (HSSs). The process is based on close to 100% conversion of non-crystalline solid Si nanoparticles (D̄ = 40 ± 9 nm) in mild alkaline solutions (pH ≤ 9.0) at ambient temperature. The Si nanoparticles are prepared using the centrifugal chemical vapor deposition (cCVD) method. Combining transmission electron microscopy (TEM) imaging and nanoparticle size analysis with hydrogen evolution data, elemental mapping, and nitrogen adsorption for surface area measurement, we show for the first time experimental data that document a Kirkendall type Si-to-HSS formation process. Our understanding is that the Si nanoparticles exposed to air form a SiO2 film, which is stable in the mild alkaline environment. Silicon from the Si nanoparticles is transported through the thin SiO2 film and is reacting with H2O/OH- species on the particle surface or in the already thickened SiO2 shell to form silicic acid that in turn rapidly gets converted to a sol-gel to continue the growing of the silica shell. We foresee that this green chemistry approach can be utilized for HSS preparation for use in batteries, insulation materials and drug delivery.

The secondary structure of diatom silaffin peptide R5 determined by two-dimensional infrared spectroscopy.

Diatoms, unicellular marine organisms, harness short peptide repeats of the protein silaffin to transform silicic acid into biosilica nanoparticles. This process has been a white whale for material scientists due to its potential in biomimetic applications, ranging from medical to microelectronic fields. Replicating diatom biosilicification will depend on a thorough understanding of the silaffin peptide structure during the reaction, yet existing models in the literature offer conflicting views on peptide folding during silicification. In our study, we employed two-dimensional infrared spectroscopy (2DIR) within the amide I region to determine the secondary structure of the silaffin repeat unit 5 (R5), both pre- and post-interaction with silica. The 2DIR experiments are complemented by molecular dynamics (MD) simulations of pure R5 reacting with silicate. Subsequently, theoretical 2DIR spectra calculated from these MD trajectories allowed us to compare calculated spectra with experimental data, and to determine the diverse structural poses of R5. Our findings indicate that unbound R5 predominantly forms β-strand structures alongside various atypical secondary structures. Post-silicification, there's a noticeable shift: a decrease in β-strands coupled with an increase in turn-type and bend-type configurations. We theorize that this structural transformation stems from silicate embedding within R5's hydrogen-bond network, prompting the peptide backbone to contract and adapt around the biosilica precursors.

Development of Fast Disintegrating Tablets Containing Loxoprofen Sodium by HYDROFLASH Manufacturing Method.

In order to create and offer superior pharmaceuticals for consumers who wish to be relieved of headache and fever as soon as possible, we established HYDROFLASH manufacturing method that enables us to offer fast disintegration tablets containing loxoprofen sodium (LX), which are difficult to disintegrate. As a result of screening excipients, tablets using mannitol showed the fastest disintegration time, about 2 min. From the result of viscosity measurement, we found that LX produced higher viscosity when dissolved in water. This suggests that tablets containing LX disintegrate slower by inhibiting the penetration of water into the tablet due to the viscosity caused of LX. Therefore, we created a manufacturing method to make it easy for water to penetrate the tablet. It is possible to achieve fastest disintegration in about 30 s for tablets containing LX by granulating in a fluidized-bed with spraying of the dispersion of light anhydrous silicic acid (LASA). LX-containing tablets manufactured by the HYDROFLASH method disintegrated immediately after contact with water. Furthermore, it was observed that LASA was uniformly dotted on the surface of tablets by HYDROFLASH method, compared with other manufacturing methods. We considered that by fluidized-bed granulation with LASA dispersion (HYDROFLASH manufacturing method), water permeates through LASA on the tablet surface regardless of viscosity of LX. Futhermore, LX-containing tablets by the HYDROFLASH method showed that the dissolution rate of LX was nearly 100% at 5 min after starting the test. We considered that the initial dissolution became faster because of the fast disintegration.

Chromatographic Separation and Quantitation of Sphingolipids from the Central Nervous System or Any Other Biological Tissue.

Chromatographic separation and purification of an individual lipid to homogeneity have long been introduced. Using this concept, a more precise method has been developed to identify and characterize the sphingolipid composition(s) using a small amount (30mg) of biological sample. Sphingolipids (lipids containing sphingosine or dihydrosphingosine) are well-known regulators of the central nervous system development and play a critical role in neurodegenerative diseases. Introducing a silicic acid column chromatography, sphingolipid components have been separated to individual fractions such as ceramide, glucosyl/galactosylceramide, other neutral and acidic glycosphingolipids, including (dihydro)sphingosine and psychosine; as well as phospholipids from which individual components are quantified employing a single or combination of other advanced chromatography procedures such as thin-layer chromatography, gas chromatography-mass spectrometry, and high-performance liquid chromatography-mass spectrometry.

Rapid Determination of PCDDs, PCDFs and DL-PCBs in Foods, Feedingstuffs and Vegetable Oils Using New Modified Acid Silica

Polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls are persistent organic pollutants (POPs), which in the recent years received huge attention due to their extreme stability, high potential toxicity and bioaccumulation in food chains.

Biomimetic Sol-Gel Chemistry to Tailor Structure, Properties, and Functionality of Bionanocomposites by Biopolymers and Cells.

Biosilica, synthesized annually only by diatoms, is almost 1000 times more abundant than industrial silica. Biosilicification occurs at a high rate, although the concentration of silicic acid in natural waters is ~100 μM. It occurs in neutral aqueous solutions, at ambient temperature, and under the control of proteins that determine the formation of hierarchically organized structures. Using diatoms as an example, the fundamental differences between biosilicification and traditional sol-gel technology, which is performed with the addition of acid/alkali, organic solvents and heating, have been identified. The conditions are harsh for the biomaterial, as they cause protein denaturation and cell death. Numerous attempts are being made to bring sol-gel technology closer to biomineralization processes. Biomimetic synthesis must be conducted at physiological pH, room temperature, and without the addition of organic solvents. To date, significant progress has been made in approaching these requirements. The review presents a critical analysis of the approaches proposed to date for the silicification of biomacromolecules and cells, the formation of bionanocomposites with controlled structure, porosity, and functionality determined by the biomaterial. They demonstrated the broad capabilities and prospects of biomimetic methods for creating optical and photonic materials, adsorbents, catalysts and biocatalysts, sensors and biosensors, and biomaterials for biomedicine.

Study of the adsorption-desorption of Cr (III) on green silica obtained from sodium silicate

Mesoporous silica (MS) is nowadays one of the most widely used materials for the removal of contaminants in water; however, its main disadvantage is its production cost, since it is obtained by the sol-gel process using tetraethyl orthosilicate (TEOS) as silica former, which is not an economical reagent. In this article, we propose the synthesis route of SM from industrial sodium silicate; Na2SiO3 by passing it through an ion exchange column (DOWEX-50WX8-100) to obtain silicic acid (Si(OH)4). The acid fraction is collected from the ion exchange column at pH 1–3 and allowed to age for 24 h. The SM silicate is formed from the gelation of the aged silicic acid and was characterized by infrared spectroscopy. The porosity was determined by N2 desorption adsorption isotherms and scanning electron microscopy. The Cr(3+) removal capacity was evaluated by the effect of the initial Cr(3+) concentration. Obtaining that the maximum removal capacity was 108.7 mg/g for a Cr3+ solution of 2794 ppm

Molecular Design of Functional Polymers for Silica Scale Inhibition.

Silica polymerization, which involves the condensation reaction of silicic acid, is a fundamental process with wide-ranging implications in biological systems, material synthesis, and scale formation. The formation of a silica-based scale poses significant technological challenges to energy-efficient operations in various industrial processes, including heat exchangers and water treatment membranes. Despite the common strategy of applying functional polymers for inhibiting silica polymerization, the underlying mechanisms of inhibition remain elusive. In this study, we synthesized a series of nitrogen-containing polymers as silica inhibitors and elucidated the role of their molecular structures in stabilizing silicic acids. Polymers with both charged amine and uncharged amide groups in their backbones exhibit superior inhibition performance, retaining up to 430 ppm of reactive silica intact for 8 h under neutral pH conditions. In contrast, monomers of these amine/amide-containing polymers as well as polymers containing only amine or amide functionalities present insignificant inhibition. Molecular dynamics simulations reveal strong binding between the deprotonated silicic acid and a polymer when the amine groups in the polymer are protonated. Notably, an extended chain conformation of the polymer is crucial to prevent proximity between the interacting monomeric silica species, thereby facilitating effective silica inhibition. Furthermore, the hydrophobic nature of alkyl segments in polymer chains disrupts the hydration shell around the polymer, resulting in enhanced binding with ionized silicic acid precursors compared to monomers. Our findings provide novel mechanistic insights into the stabilization of silicic acids with functional polymers, highlighting the molecular design principles of effective inhibitors for silica polymerization.

Benthic contribution to seasonal silica budgets in two macrotidal estuaries in North-Western France

The paper aims to build seasonal silica budgets in two macrotidal estuaries, the Elorn and Aulne estuaries of the Bay of Brest (North-Western France), based on modeling and measurements, in order to increase our understanding of the silica (Si) cycle at land-sea interfaces. A diagenetic model was developed to quantify benthic Si fluxes, e.g. aSiO2 deposition fluxes that are difficult to assess through direct measurements. Sediment cores were also seasonally sampled at six stations to provide data essential to parametrize and validate the model. Vertical profiles of porosity, burrowing depth, biodiffusive coefficients, concentrations of amorphous silica (aSiO2) and silicic acid (Si(OH)4 and the proportion of reactive aSiO2 were measured. The results show that sites sampled along the Elorn and Aulne estuaries constitute significant net Si deposition areas (1-4.5 mmol Si m-2 d-1), particularly in the upstream during winter and in midstream and downstream during summer. Year round, reprecipitation is negligible (< 3%) while burial accounts for the retention of ~ 30-80% of deposited aSiO2. In winter, burial dominates the benthic Si budget. As surface-integrated benthic Si fluxes are low compared to riverine aSiO2 fluxes, the Si export to coastal waters is high (93%) during winter. In contrast, in summer, burial accounts for 38% of river Si fluxes, and Si(OH)4 flux from the sediment is high as a result of enhanced benthic recycling and bioirrigation. Internal estuarine processes, e.g., benthic and pelagic primary production, dissolution and benthic Si fluxes, surpass river fluxes in magnitude during summer. Overall, we conclude that the Elorn and Aulne macrotidal estuaries are efficient filters of Si, retaining about 4-38% of river Si fluxes, and even 6-67% when accounting for retention in intertidal marshes, but with massive exports occurring during winter floods.

Extracellular silicon (Si) nanocoating induced by cationic polymers enhances heavy metal resistance in both Si-accumulating and non-Si-accumulating plants

Heavy metal contamination poses a significant threat to food security, requiring the development of plant protection measures. Silicon (Si) deposition on rice roots can inhibit the uptake and translocation of heavy metal ions. However, the slow process of Si polymerization limits its utilization by many plants. This study explored the use of cation-induced silicic acid polymerization to rapidly form extracellular Si nanocoatings on plant roots using ten cationic polymeric materials. Performance, safety, and cost-effectiveness were comprehensively evaluated in enhancing rice's resistance to heavy metals, particularly trivalent chromium. Guar hydroxypropyl trimonium chloride (GHPT) showed the most promising results among the materials studied. A treatment procedure involving immersion in GHPT and silicic acid was found to be effective when repeated twice for 20 min each time. This method effectively doubled Si concentration in rice roots and reduced shoot chromium concentration by 67%. Furthermore, this approach was successfully applied to pakchoi, enabling Si utilization in this non-Si-accumulating plant. The Si concentration in pakchoi roots increased to levels similar to rice (1577.5 μg/g), and shoot chromium concentration decreased by 75.0%, accompanied by a 66.2% reduction in chromium translocation factor. These findings provide a safe, economical and practical solution to reduce heavy metal stress.

Separate and Combined Effects of Silicic and Salicylic Acids On Growth and N2-Fixation in Lentil Plants Under Water Stress

Separate and Combined Effects of Silicic and Salicylic Acids On Growth and N2-Fixation in Lentil Plants Under Water Stress

Efficacy of the Enteroadsorbent Silicol®gel in Adults with Irritable Bowel Syndrome Subtypes IBS-D or Mixed: Observational Open-Label Study.

Irritable bowel syndrome (IBS) is a common chronic gut-brain interaction disorder with limited effective treatment options. Intestinal adsorbents have a high adsorption capacity for gut irritants and may provide nonpharmacological alternatives. This post marketing study is aimed at providing up-to-date evidence to support the safety and efficacy in normal use of an established medical device for IBS treatment. In this open-label, observational study, adults with IBS with predominant diarrhoea (IBS-D) or IBS with mixed bowel habits (IBS-M), according to Rome IV criteria, received 4 weeks of treatment with the enteroadsorbent Silicol®gel, a CE-certified, licenced, medical device containing colloidal silicic acid. Eligible participants were assessed at baseline (visit 1; in-clinic) and after 1 (visit 2; telephone), 2 (visit 3; telephone), and 4 (visit 4; in-clinic) weeks of treatment. The primary endpoint was the proportion of participants with an overall reduction in the IBS severity scoring system (IBS SSS) > 50, representing clinically meaningful improvement. Key secondary endpoints were a reduction in common IBS symptoms and improved quality of life (QoL). Among the 67 treated participants (IBS-D: 37; IBS-M: 30), 65 completed the study. At visit 4, 83.6% (56/67) of participants achieved a reduction in IBS SSS > 50. The mean (standard deviation [SD]) IBS SSS was 323.4 (55.7) at visit 1 and 160.3 (90.3) at visit 4 (overall change: -163.1 (101.7); 95% confidence interval [CI] 138.3, 187.9, p < 0.001). Compared with visit 1, significant reductions in the severity of all key IBS symptoms and overall improvement in QoL were observed at visit 4 (p < 0.001), with improvements observed from visits 1 and 2. In this open-label study of participants with IBS-D and IBS-M, Silicol®gel provided clinically significant improvement in IBS symptoms, demonstrating that enteroadsorbents may be clinically beneficial in this population.

Augmented effects of silicon solubilizer on biochemical analysis of rice grains under normal and water stress conditions

The purpose of this study was to determine whether Si solubilizer could increase nutrient content in rice grains and help mitigate the negative impacts of water stress conditions. A field trial was performed with eight genotypes of rice (Oryza sativa L.) for two seasons to estimate the effects of silicon (Si) solubilizer on rice grains under normal and water stress conditions. Treatments included control (T1), Si sprays (0.6% Ortho silicic acid) (T2), Si sprays + water stress (T3), and water stress only (T4). The findings showed that Si solubilizer had favorable impacts on protein, amylose, iron, and zinc across genotypes. Under water stress, the Si treatment significantly increased the protein content in IIRRH-148 (8.25%), amylose content in IIRRH-143 (18.74%), Fe content in husked seeds of 27P63 (381.36 µg/g), Fe content in dehusked seeds of 27P63 (185. 41 µg/g), Zn content in husked seeds of US-312 (48.09 µg/g), and Zn content in dehusked seeds of US-314 (37.34 µg/g). Given the harsh climate change scenarios, it was determined that the application of Si solubilizer enhances nutrient content, improves the quality of rice grains, and fulfills the needs of an ever-increasing population in the coming years. Therefore, the impact of this factor on increasing the nutrient content should be considered.