Deposition of silica in sorghum root endodermis modifies the chemistry of associated lignin.

Silica aggregates at the endodermis of sorghum roots. Aggregation follows a spotted pattern of locally deposited lignin at the inner tangential cell walls. Autofluorescence microscopy suggests that non-silicified (-Si) lignin spots are composed of two distinct concentric regions of varied composition. To highlight variations in lignin chemistry, we used Raman microspectroscopy to map the endodermal cell wall and silica aggregation sites in sorghum roots grown hydroponically with or without Si amendment. In +Si samples, the aggregate center was characterized by typical lignin monomer bands surrounded by lignin with a low level of polymerization. Farther from the spot, polysaccharide concentration increased and soluble silicic acid was detected in addition to silica bands. In -Si samples, the main band at the spot center was assigned to lignin radicals and highly polymerized lignin. Both +Si and -Si loci were enriched by aromatic carbonyls. We propose that at silica aggregation sites, carbonyl rich lignin monomers are locally exported to the apoplast. These monomers are radicalized and polymerized into short lignin polymers. In the presence of silicic acid, bonds typically involved in lignin extension, bind to silanols and nucleate silica aggregates near the monomer extrusion loci. This process inhibits further polymerization of lignin. In -Si samples, the monomers diffuse farther in the wall and crosslink with cell wall polymers, forming a ring of dense lignified cell wall around their export sites.

Oral Excretion Kinetics of Food-Additive Silicon Dioxides and Their Effect on In Vivo Macrophage Activation.

A food additive, silicon dioxide (SiO2) is commonly used in the food industry as an anti-caking agent. The presence of nanoparticles (NPs) in commercial food-grade SiO2 has raised concerns regarding their potential toxicity related to nano size. While recent studies have demonstrated the oral absorption and tissue distribution of food-additive SiO2 particles, limited information is available about their excretion behaviors and potential impact on macrophage activation. In this study, the excretion kinetics of two differently manufactured (fumed and precipitated) SiO2 particles were evaluated following repeated oral administration to rats for 28 d. The excretion fate of their intact particles, decomposed forms, or ionic forms was investigated in feces and urine, respectively. Monocyte uptake, Kupffer cell activation, and cytokine release were assessed after the oral administration of SiO2 particles. Additionally, their intracellular fates were determined in Raw 264.7 cells. The results revealed that the majority of SiO2 particles were not absorbed but directly excreted via feces in intact particle forms. Only a small portion of SiO2 was eliminated via urine, predominantly in the form of bioconverted silicic acid and slightly decomposed ionic forms. SiO2 particles were mainly present in particle forms inside cells, followed by ionic and silicic acid forms, indicating their slow conversion into silicic acid after cellular uptake. No effects of the manufacturing method were observed on excretion and fates. Moreover, no in vivo monocyte uptake, Kupffer cell polarization, or cytokine release were induced by orally administered SiO2 particles. These finding contribute to understanding the oral toxicokinetics of food-additive SiO2 and provide valuable insights into its potential toxicity.

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.

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 100 µM, 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.

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.

[Determination of boric acid and silicic acid in mineral water by nonsuppressed ion chromatography].

Boron and silicon are widely distributed in nature; in water, these compounds typically present in the forms of boric acid and silicic acid, respectively. The maximum allowable levels of silicic acid and boric acid in water are stipulated in relevant national and industry standards, such as GB 8538-2022. Quality changes in water, which are of great significance in water-quality evaluations, can be understood in terms of its silicic acid and boric acid contents. Boric acid content is usually determined by ion exclusion chromatography, whereas silicic acid content is usually determined by postcolumn derivatization. Therefore, traditional methods cannot achieve the simultaneous determination of silicic acid and boric acid contents in water. Modern ion chromatography has been widely used in the detection of ionic compounds, such as anions, cations, organic acids, organic amines, amino acids, and sugars. Boric (pKa=9.24) and silicic (pKa=9.77) acids are weak acids that dissociate into ionic states under alkaline conditions. Although these compounds cannot be tested using suppressed ion chromatography, they can be retained on ion chromatography columns. In this study, a method based on nonsuppressed conductance detection was established for the simultaneous determination of boric acid and silicic acid in water. The contents of boric acid and silicic acid were detected by nonsuppressed ion chromatography using a Dionex IonPacTM AS20 analytical column. The chromatographic conditions were as follows: flow rate, 1.0 mL/min; column temperature, 30 ℃; eluent, 6 mmol/L sodium hydroxide solution and 60 mmol/L mannitol; and sample injection volume, 50 µL. The effective separation of silicic acid and boric acid was achieved within 8 min. SiO32- and boric acid demonstrated good linear relationships in the concentration ranges of 0.25-100 and 0.5-100 mg/L (correlation coefficients, 0.9999), respectively. The method detection (MDL) and quantification (MQL) limits were 0.078 and 0.26 mg/L for SiO32-, and the MDL and MQL limits were 0.18 and 0.60 mg/L for boric acid. The average recoveries of boric acid and SiO32- (n=6) were 97.3%-105.3%. Moreover, the relative standard deviations were less than 0.9% for boric acid at four spiked levels and less than 0.30% for SiO32- at three spiked levels. Thus, the method meets detection requirements. The pretreatment method is very simple, and the sample can be directly injected through a 0.22 µm water filtration membrane and into the column. The boric acid and silicic acid contents in nine mineral drinking water samples were determined under the optimized analytical conditions. Boric acid was not detected in these nine samples, but silicic acid was detected in six samples. The silicic acid contents detected were between 18.70 and 62.08 mg/L, which was consistent with the concentration ranges marked on the manufacturers' packaging. The proposed method can be used for the determination of boric acid and silicic acid in mineral drinking water and laboratory water, and provides a reference for the simultaneous detection of boric acid and silicic acid in ultrapure water used in the semiconductor industry.

From promoting aggregation to enhancing obstruction: A negative feedback regulatory mechanism of alleviation of trivalent chromium toxicity by silicon in rice.

Trivalent chromium [Cr(III)] is a threat to the environment and crop production. Silicon (Si) has been shown to be effective in mitigating Cr(III) toxicity in rice. However, the mechanisms by which Si reduces Cr(III) uptake in rice are unclear. Herein, we hypothesized that the ability of Si to obstruct Cr(III) diffusion via apoplastic bypass is related to silicic acid polymerization, which may be affected by Cr(III) in rice roots. To test this hypothesis, we employed hydroponics experiments on rice (Oryza sativa L.) and utilized apoplastic bypass tracer techniques, as well as model simulations, to investigate 1) the effect of Si on Cr(III) toxicity and its obstruction capacity via apoplastic bypass, 2) the effect of Cr(III) on silicic acid polymerization, and 3) the relationship between the degree of silicic acid polymerization and its Cr(III) obstruction capacity. We found that Si reversed the damage caused by Cr(III) stress in rice. Si exerted an obstruction effect in the apoplast, significantly decreasing the share of Cr(III) uptake via the apoplastic bypass from 18% to 11%. Moreover, Cr(III) reduced silica particles' radii and increased Si concentration in roots. Modeling revealed that a 5-fold reduction in their radii decreased the diffusion of Cr(III) in apoplast by approximately 17%. We revealed that Cr(III) promoted silicic acid polymerization, resulting in the formation of a higher number of Si particles with a smaller radius in roots, which in turn increased the ability of Si to obstruct Cr(III) diffusion. This negative feedback regulatory mechanism is novel and crucially important for maintaining homeostasis in rice, unveiling the unique role of Si under Cr(III) ion stress and providing a theoretical basis for promoting the use of Si fertilizer in the field.

Silica deposition in plants: scaffolding the mineralization.

BACKGROUND: Silicon and aluminium oxides make the bulk of agricultural soils. Plants absorb dissolved silicon as silicic acid into their bodies through their roots. The silicic acid moves with transpiration to target tissues in the plant body, where it polymerizes into biogenic silica. Mostly, the mineral forms on a matrix of cell wall polymers to create a composite material. Historically, silica deposition (silicification) was supposed to occur once water evaporated from the plant surface, leaving behind an increased concentration of silicic acid within plant tissues. However, recent publications indicate that certain cell wall polymers and proteins initiate and control the extent of plant silicification. SCOPE: Here we review recent publications on the polymers that scaffold the formation of biogenic plant silica, and propose a paradigm shift from spontaneous polymerization of silicic acid to dedicated active metabolic processes that control both the location and the extent of the mineralization. CONCLUSION: Protein activity concentrates silicic acid beyond its saturation level. Polymeric structures at the cell wall stabilize the supersaturated silicic acid and allow its flow with the transpiration stream, or bind it and allow its initial condensation. Silica nucleation and further polymerization are enabled on a polymeric scaffold, which is embedded within the mineral. Deposition is terminated once free silicic acid is consumed or the chemical moieties for its binding are saturated.

Silicic Acid Removal by Metal-Organic Frameworks for Silica-Scale Mitigation in Reverse Osmosis.

Reverse osmosis (RO) membranes are susceptible to silica scaling, resulting in irreversible degradation of membrane performance. This work covered the fabrication of MIL-101(Fe) for silicic acid adsorption to alleviate the silica scaling of RO membranes. The effect of pH, mixing time and initial concentration on silicic acid adsorption of MIL-101(Fe) was appraised in detail. The adsorption experiments demonstrated that MIL-101(Fe) possessed an excellent adsorption ability for silicic acid with the maximum adsorption capacity reaching 220.1 mgSiO2·g-1. Data fitting confirmed the pseudo-second-order equation and Freundlich equation were consistent with silicic acid adsorption on MIL-101(Fe). Finally, a simulated anti-scaling experiment was carried out using a feed solution pretreated by MIL-101(Fe) adsorption, and the permeance exhibited a much lower decline after 24 h filtration, confirming that MIL-101(Fe) exhibits an excellent application potential for silica-scale mitigation in RO systems.

Ortho-silicic Acid Plays a Protective Role in Glucocorticoid-Induced Osteoporosis via the Akt/Bad Signal Pathway In Vitro and In Vivo.

Glucocorticoid-induced osteoporosis (GIOP) has been the most common form of secondary osteoporosis. Glucocorticoids (GCs) can induce osteocyte and osteoblast apoptosis. Plenty of research has verified that silicon intake would positively affect bone. However, the effects of silicon on GIOP are not investigated. In this study, we assessed the impact of ortho-silicic acid (OSA) on Dex-induced apoptosis of osteocytes by cell apoptosis assays. The apoptosis-related genes, cleaved-caspase-3, Bcl-2, and Bax, were detected by western blotting. Then, we evaluated the possible role of OSA on osteogenesis and osteoclastogenesis with Dex using Alizarin red staining and tartrate-resistant acid phosphatase (TRAP) staining. We also detected the related genes by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blotting. We then established the GIOP mouse model to evaluate the potential role of OSA in vivo. We found that OSA showed no cytotoxic on osteocytes below 50 µM and prevented MLO-Y4 from Dex-induced apoptosis. We also found that OSA promoted osteogenesis and inhibited osteoclastogenesis with Dex. OSA had a protective effect on GIOP mice via the Akt signal pathway in vivo. In the end, we verified the Akt/Bad signal pathway in vitro, which showed the same results. Our finding demonstrated that OSA could protect osteocytes from apoptosis induced by GCs both in vitro and in vivo. Also, it promoted osteogenesis and inhibited osteoclastogenesis with the exitance of Dex. In conclusion, OSA has the potential value as a therapeutic agent for GIOP.

Stability of Eu(III)-silicate colloids: Effect of Eu content, pH, electrolyte and fulvic acid.

Dissolved silicic acid in the environment has strong affinity for actinides (An), but An(III)-silicate colloids have been scarcely investigated. In this study, Eu(III)-silicate colloids, an analogue to An(III)-silicate, were prepared and the aggregation kinetics of the colloids was investigated as a function of Eu content (Si/Eu molar ratio), pH, background electrolyte (NaCl, NaNO3, NaClO4, KCl and CsCl) and fulvic acid (FA). Results indicated that the colloids with higher Si/Eu molar ratio exhibited higher stability under the same conditions. The stability of the colloids increased with increasing aqueous pH (7.1-9.4) and decreasing ionic strength, and the inhibition effect of monovalent electrolytes on the colloid stability followed the order of Na+ < K+ < Cs+ and Cl- < NO3- < ClO4-. In addition, the presence of FA significantly increased the stability of the colloids. The dependence of the stability on the chemical conditions in all cases could be illustrated by DLVO theory. Disaggregation kinetics showed that the aggregation process of the colloids was not fully reversible, because a time-dependent size memory effect led to a bigger mean size of disaggregated colloids as compared to the initial ones. The present work provides detailed insight in the formation and stability of An(III)-silicate colloids under the alkaline conditions relevant to geological disposal of radioactive waste, which is critical for understanding the behavior of this type of colloids in the environment.

Silicon enhances abundances of reducing microbes in rhizoplane and decreases arsenite uptake by rice (Oryza sativa L.).

Although silicon (Si) transporters-mediated uptake of arsenic (As) by rice roots is well-documented, how Si influences As behaviors in rhizosphere and rhizoplane before As entry into roots is still unclear. Here we used three rice genotypes to explore the effect of silicic acid on the root uptake of As as impacted by chemical and microbial changes in bulk soil, rhizosphere, rhizoplane and endosphere. The results show that exogenous Si decreased root arsenite [As(III)] absorption, which was attributed to Si-mediated alteration of traits in chemical plaque and microbial films on the rhizoplane. The pH, Eh, As and Fe in the porewater were not influenced by Si. However, Si enhanced the concentrations of As(III) (16-49%) and Fe (15-80%) in the rhizoplane while decreasing As(III) concentrations in the roots (19-39%) and grains (22-29%). The diversities and richness of microbes in soils and plants were not affected by Si. The microbial connections were negatively influenced by Si in bulk and rhizosphere soils, but positively impacted in rhizoplane and endosphere. Both the abundance of reducing microbes, Anaeromyxobacter and Geobacteraceae, and the level of As(III) and Fe in rhizoplane were significantly increased by the addition of Si, thereby restraining As(III) from uptake into roots. This study provides new insights into the microbial mechanisms of Si-mediated As uptake by rice.

Engineering a biomimetic bone scaffold that can regulate redox homeostasis and promote osteogenesis to repair large bone defects.

The reconstruction of a large bone defect to an extent that exceeds its self-healing capacity has been a great clinical challenge. In pursuit of this goal, a biomaterial-based scaffold that comprises radially aligned mineralized collagen (RA-MC) fibers that incorporate nanosilicon (RA-MC/nSi), is proposed. The chemical composition of the MC fibers is similar to that of natural bone matrices. The therapeutic efficacy of the RA-MC/nSi scaffold is evaluated in a mouse model with an experimentally created large calvarial defect. In vitro and in vivo results reveal that the RA-MC fibers of the scaffold guide the directional infiltration and migration of reparative cells from the host tissue toward the center of the defect, suggesting a potential application in promoting osteoconductivity. The incorporated nSi renders the scaffold able sustainably to release gaseous hydrogen and water-soluble silicic acid during the healing process. The released hydrogen gas can effectively regulate redox homeostasis and mitigate excessive inflammation, and the silicic acid can promote the proliferation of reparative cells and enhance their osteogenic differentiation, indicative of osteoinductivity. These findings support the use of the as-proposed biomimetic RA-MC/nSi scaffold as a promising bone substitute to enhance the regeneration of large bone defects.

Improving the Durability of Lime Finishing Mortars by Modifying Them with Silicic Acid Sol.

Lime materials are in great demand for the restoration of the walls of historical buildings. However, lime coatings have insufficient resistance during operation. The purpose of this work was the modification of lime mortars with silicic acid sol in order to obtain more durable crystalline materials for construction purposes. A technology has been developed for obtaining a silica-containing additive, which consists in passing a liquid glass solution with a density of 1.053 kg/m3 through a cationic column and obtaining a silicic acid sol with a pH of 3-4 and a charge of (-) 0.053 V. The regeneration time and the amount of sol have been determined. Regularities of change in the radius of particles of silicic acid sol depending on age are determined. It is established that at an early age (up to 5 days), the radius of sol particles can be determined in accordance with the Rayleigh equation, and at a later age, in accordance with the Heller equation. The results of the calculation show that at the age of 1-5 days, the radius of the sol particles is 17.1-17.9 nm, and then the particles become coarser and the particle radius is 131.2-143 nm at the age of 19 days. The work of adhesion of silicic acid sol to lime and the heat of wetting are estimated. It is shown that the work of adhesion of water to lime is 28.9 erg/cm2, and that of the sol is 32.8 erg/cm2. The amount of heat Q released when lime is wetted with SiO2 sol is 15.0 kJ/kg, and when lime is wetted with water, it is 10.6 kJ/kg.

Hydrogen peroxide modulates silica deposits in sorghum roots.

Hydrated silica (SiO2·nH2O) aggregates in the root endodermis of grasses. Application of soluble silicates (Si) to roots is associated with variations in the balance of reactive oxygen species (ROS), increased tolerance to a broad range of stresses affecting ROS concentrations, and early lignin deposition. In sorghum (Sorghum bicolor L.), silica aggregation is patterned in an active silicification zone (ASZ) by a special type of aromatic material forming a spotted pattern. The deposition has a signature typical of lignin. Since lignin polymerization is mediated by ROS, we studied the formation of root lignin and silica controlled by ROS via modulating hydrogen peroxide (H2O2) concentrations in the growth medium. Sorghum seedlings were grown hydroponically and supplemented with Si, H2O2, and KI, an ionic compound that catalyses H2O2 decomposition. Lignin and silica deposits in the endodermis were studied by histology, scanning electron and Raman microscopies. Cell wall composition was quantified by thermal gravimetric analysis. Endodermal H2O2 concentration correlated to the extent of lignin-like deposition along the root, but did not affect its patterning in spots. Our results show that the ASZ spots were necessary for root silica aggregation, and suggest that silicification is intensified under oxidative stress as a result of increased ASZ lignin-like deposition.

Study on the mechanism of PAMAM(DETA as the core) against silica scale.

Molecular simulation was performed to study the interaction between PAMAM(DETA as the core) with different generations and silicic acid molecules, and discussed the inhibition effect mechanism against silica scale through gyration radius and radial distribution function et al. The results showed that adsorption interactions between silicic acid molecules and the PAMAM with -NH2 terminated groups molecule (G1.0 and G2.0) were stronger than those and the PAMAM with -COOH terminated groups molecule (G0.5 and G1.5). The adsorption interactions were primarily divided into electrostatic interactions, vdW interactions as well as H-bond interactions, where electrostatic interaction was dominant. Molecular simulation results were consistent with our experimental results.

Structural Basis for Silicic Acid Uptake by Higher Plants.

Many of the world's most important food crops such as rice, barley and maize accumulate silicon (Si) to high levels, resulting in better plant growth and crop yields. The first step in Si accumulation is the uptake of silicic acid by the roots, a process mediated by the structurally uncharacterised NIP subfamily of aquaporins, also named metalloid porins. Here, we present the X-ray crystal structure of the archetypal NIP family member from Oryza sativa (OsNIP2;1). The OsNIP2;1 channel is closed in the crystal structure by the cytoplasmic loop D, which is known to regulate channel opening in classical plant aquaporins. The structure further reveals a novel, five-residue extracellular selectivity filter with a large diameter. Unbiased molecular dynamics simulations show a rapid opening of the channel and visualise how silicic acid interacts with the selectivity filter prior to transmembrane diffusion. Our results will enable detailed structure-function studies of metalloid porins, including the basis of their substrate selectivity.

Bacterial biosilicification: a new insight into the global silicon cycle.

Biosilicification is the process by which organisms incorporate soluble, monomeric silicic acid, Si(OH)4, in the form of polymerized insoluble silica, SiO2. Biosilicifying eukaryotes, including diatoms, siliceous sponges, and higher plants, have been the targets of intense research to study the molecular mechanisms underlying biosilicification. By contrast, prokaryotic biosilicification has been less well studied, partly because the biosilicifying capability of well-known bacteria was not recognized until recently. This review summarizes recent findings on bacterial extracellular and intracellular biosilicification, the latter of which has been demonstrated only recently in bacteria. The topics discussed herein include bacterial (and archaeal) extracellular biosilicification in geothermal environments, encapsulation of Bacillus spores within a silica layer, and silicon accumulation in marine cyanobacteria. The possible contribution of bacterial biosilicification to the global silicon cycle is also discussed.

Graphene Oxide and Stabilized Ortho-Silicic Acid as Modifiers of Amnion and Burn Affected Skin: A Comparative Study.

INTRODUCTION: Oxidative tissue damage caused by reactive oxygen species results in a significant decrease in the total antioxidant capacity of the biological system. The aim of this interdisciplinary study was to answer the question of whether active antioxidants modify, at a molecular and supramolecular level, the tissue of pathological amnion and the necrotic eschar degraded in thermal burn. METHODS: A Nicolet 6700 Fourier-transform spectrophotometer with OMNIC software and the EasiDiff diffusion accessory were used in the FTIR spectroscopic analysis. A NICOLET MAGNA-IR 860 spectrometer with FT-Raman accessory was used to record the Raman spectra of the samples. The samples were exposed to bacteria capable of causing nosocomial infections, ie Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa. Whereas samples of hypotrophic amnion interacted with Staphylococcus aureus, Escherichia coli and Enterococcus faecalis. The obtained flame retardant effect of placentas was evaluated using the method of the limiting oxygen index (LOI). RESULTS: The infrared spectroscopy analysis proved that after modification of the amniotic samples in graphene oxide and ortho-silicic acid, the amide II band is split into two components. Incubation of samples in modifier solutions: graphene oxide, sodium ascorbate and L-ascorbic acid results in shifts and changes of intensity within the broadly understood lipid band 1743-1745-1747 cm-1. The oxidising changes observed within the lipid and amide bands are affected by the incubation effect of graphene oxide as a modifier, possibly adsorbing on the surface of the amniotic membrane. On the basis of microbiological studies, pathogenic bacteria commonly causing amniotic infections and growing in burn wounds were found to have particularly good resistance to stabilized ortho-silicic acid (E. coli) and lactoferrin (S.aureus). CONCLUSION: This thermogravimetric study found the highest stability of the analysed tissues (hypotrophic amnion and burnt epidermis) after modification with graphene oxide and sodium ascorbate.

Ortho-silicic Acid Inhibits RANKL-Induced Osteoclastogenesis and Reverses Ovariectomy-Induced Bone Loss In Vivo.

Numerous experiments in vitro and in vivo have shown that an appropriate increase intake of silicon can facilitate the synthesis of collagen and its stabilization and promote the differentiation and mineralization of osteoblasts. In this study, we examined whether ortho-silicic acid restrains the differentiation of osteoclast through the receptor activator of nuclear factor κB ligand (RANKL)/receptor activator of nuclear factor κB (RANK)/osteoprotegerin (OPG) signaling pathway by investigating its effect in vitro and in vivo. Bone marrow macrophage (BMM) cells were isolated and cultured with or without ortho-silicic acid, and then TRAP staining and immunofluorescence were performed to detect the differentiation of osteoclast. The RANKL-induced osteoclast marker gene and protein expression including c-Fos, nuclear factor of activated T cells cl (NFATcl), tumor necrosis factor receptor-associated factor 6 (TRAF6), nuclear factor kappa B P50 (NF-κB P50), NF-κB P52, RANK, integrin ß3, cathepsin K (CTSK), DC-STAMP, and TRAP were quantitatively detected by western blot and RT-PCR. Ovariectomized (OVX) rats were injected with ortho-silicic acid (OVX+Si group) and normal saline (OVX group), and sham-operated rats were injected with normal saline (Sham group). And micro-CT, H&E, and TRAP staining, ELISA, and western blot were performed. Ortho-silicic acid could inhibit the differentiation of osteoclast, and the marker genes and proteins were decreased. The OVX-induced bone loss could be reversed by ortho-silicic acid. Our finding demonstrated that ortho-silicic acid suppresses RANKL-induced osteoclastogenesis and has potential value as a therapeutic agent for OVX-induced bone loss.