ABSTRACT Silicon (Si) is known to alleviate several abiotic stresses in plants, including ammonium (NH4 +) toxicity. However, the availability of Si in the nutrient solution depends on factors such as the Si source and NH4 + concentration. This study evaluated the effects of two Si sources, stabilized silicic acid (ASiE) and potassium silicate (SiK), on Micro-Tom tomato grown under NH4 + toxicity. In the first experiment, plants were supplied with 0.0, 0.2, 0.4, 0.6, and 0.8 mmol L−1 Si from either SiK or ASiE. NH4 + toxicity was induced at a NO3 −:NH4 + ratio of 3.8:11.2 mmol L−1. In the second experiment, plants received 0.0, 1.0, 2.0, and 2.5 mmol L−1 Si supplied as SiK. NH4 + toxicity was induced by 5.9 mmol L−1 NH4 +, while 5.9 mmol L−1 NO3 − was used as the control treatment. In the first experiment, Si supply did not increase shoot Si content or Si accumulation, and NH4 + toxicity was not alleviated. In contrast, in the second experiment, Si supply increased shoot Si content and Si accumulation, resulting in greater shoot and root dry weight under NH4 + toxicity. Similarly, plants supplied with NO3 − also showed increased shoot and root dry weight in response to Si application. In conclusion, low concentrations of Si supplied as either SiK or ASiE were ineffective in alleviating NH4 + toxicity. However, SiK at 1.29 mmol L−1 Si alleviated NH4 + toxicity induced by 5.9 mmol L−1 NH4 + alone.

Comparative evaluation of Tobit and Free Ion Activity Models for optimizing genotype-specific permissible arsenic limits in rice soil and irrigation water.

Gaussians On Surface Tesserae Simulate HYdrostatic Pressure (GOSTSHYP) and the eXtended Hydrostatic Compression Force Field (X-HCFF) are quantum chemical methods to simulate the effects of pressure on a single molecule. Both methods have the usage of discretized molecular surfaces in common, which are also needed in implicit solvation models like the Conductor-like Polarizable Continuum Model (C-PCM). However, a combined usage of GOSTSHYP or X-HCFF with C-PCM was not possible in previous implementations inside the Q-Chem program package. To address this circumstance, we present an independent surface construction routine for both of the pressure models. This routine enables a stable combination of C-PCM with GOSTSHYP or X-HCFF, which serves as the first step to consider the chemical surrounding inside these two pressure models. For three different compounds occurring in both neutral and zwitterionic forms, the energetic difference between these states under pressure via GOSTSHYP was investigated. Especially for compounds occurring in both zwitterionic and neutral structures, the C-PCM is essential to access the zwitterionic state. Calculated pressure dependencies in the Raman spectra of the zwitterionic structure of glycine show good agreement with experimental data. The dimerization reaction of orthosilicic acid at elevated pressure is also influenced by implicit solvation, leading to better agreement between the simulations and the experimental data. This study paves the way for the inclusion of explicit solvation to disentangle intra- and intermolecular effects that cause geometric and spectroscopic changes under pressure applied with GOSTSHYP and X-HCFF.

ABSTRACT To simultaneously achieve the valorisation of metal resources and mitigate the environmental hazards associated with solid waste, this study investigated the sulfuric acid extraction behaviour of magnesium, iron, and nickel from asbestos tailings. Single-factor leaching experiments evaluated the effects of leaching temperature, reaction time, acid-to-ore ratio, and liquid-to-solid ratio on metal extraction. Within the investigated ranges, the most favourable leaching conditions were 100 °C, 2.5 h, an acid-to-ore ratio of 0.9 mL·g−1, and a liquid-to-solid ratio of 6 mL·g−1. Under these conditions, the leaching rates of Mg, Fe, and Ni were 89.24%, 62.57%, and 76.13%, respectively. Characterisation results confirmed that silicon from the tailings remained in the leaching residue, primarily in the form of amorphous silicic acid. Furthermore, kinetic modelling revealed that the dissolution of all three metals follows a mixed control mechanism. This process is governed synergistically by interfacial chemical reactions and diffusion across the product layer. The apparent activation energies of magnesium, iron, and nickel were 38.16, 41.84, and 25.98 kJ·mol−1, respectively. The outcomes of this work establish a theoretical basis for the acid leaching process. Furthermore, they provide a valuable reference for the comprehensive valorisation of asbestos tailings.

The objective of this work was to evaluate the effect of fertilization with different sources of silicon on key physiological traits and the pattern of absorption and distribution of the silicon element in passion fruit seedlings. A randomized block design was used with eight treatments (control; Agrosilicon Plus®; pure silicic acid; pure silicic acid + calcium oxide; pure silicic acid + magnesium oxide; pure silicic acid + calcium oxide + magnesium oxide; calcium oxide; magnesium oxide) x four replications and two pots per plot. Quantum yield of photosystem II, photosynthetic index, stomatal conductance, transpiration rate and water use efficiency were assessed. Moreover, the contents of Si in shoot, roots and soil, as well as its absorption efficiency and distribution within plants were evaluated. Although the supplementation with pure silicic acid reduced net photosynthetic rates and transpiration, the other physiological traits were not significantly changed when compared to the control. In addition, higher silicon content was found in both shoots and root system of plants treated with pure silicic acid. Silicon sources altered silicon accumulation patterns, with greater root accumulation under pure silicic acid, indicating limited internal distribution under the evaluated conditions.

The transport of carbon into the deep Earth is governed by the stability and properties of carbon-bearing phases. However, despite extensive research efforts, it is still an open question whether there are high-pressure minerals that can incorporate both silicon and carbon simultaneously. Multiple theoretical studies suggest that Si─C─O compounds could be stabilized at high pressures, but so far, no reliable experimental evidence for their presence has been presented. Here, we demonstrate that at 40(2) gigapascals and ≈ 1800(200) kelvin, CO2 reacts with silicic acid or cristobalite and forms the anhydrous silicon carbonate Si[CO3]2. The structure consists of [SiO6] octahedra coordinated by six [CO3]2− groups. Similar groups occur in many ambient and high-pressure carbonates, suggesting that mixed carbonate-silicate phases may be stable at midmantle pressures. Silicon carbonate decomposes upon decompression at pressures of <6 gigapascals but could act as a potential host for carbon in Earth’s lower mantle.

Sea ice primary production is a key component supplying carbon to higher trophic levels when few other resources are available. In bottom-ice habitats, this production is limited by light availability and nutrient supply from underlying seawater. Reports of low sea ice primary production from Greenland have reinforced the view that landfast ice is regionally unimportant. Here, we document a single early-spring observation of intense algal production in sea ice adjacent to marine terminating glaciers in West Greenland, an environment rarely examined in ice studies. The bloom included abundant pennate diatoms, including Nitzschia frigida, and reached a daily primary production of 146 ± 4.8mg C m⁻² d⁻¹ and biomass accumulation of 42.4 ± 1.6mg Chlorophyll a (Chl a) m⁻², exceeding previous Greenland observations. A biomass-specific production of 3.40mg C mg Chl a⁻¹ d⁻¹ and maximum quantum yield (ΦPSII_max) of 0.44 indicated an active community. Strong silicic acid depletion in the presence of significant nitrate and phosphate concentrations suggested that silicic acid was the primary limiting nutrient within the ice. We propose that inflow-driven fjord circulation likely enhanced nutrient availability beneath the ice, while turbulence-driven fluxes across the ice-ocean interface represent a plausible mechanism for sustaining the observed high sympagic production during this sampling event. Sea ice in fjords with marine-terminating glaciers may therefore support high early-season production under favorable local conditions.

Silica solubilizing bacteria (SSB) play a vital role in the silicon (Si) cycle by producing the enzyme silicase, which converts insoluble silicates into bioavailable silicic acid, replenishing bio-available Si in soil. Si, a beneficial element for silica-rich plants, is depleted annually due to plants uptake, intensive agriculture, and slow silicate bio-weathering. This study aims to isolate novel SSB with an enhanced silicate desilicification potential from rice field soil. Primary screening for silica solubilization ability was performed on silicate glucose agar (SGA). The selected bacterial strain was evaluated for silicase production under submerged fermentation (SmF) condition using a modified Horikoshi medium. Then, molecular identification was performed by 16S rRNA sequencing analysis and confirmed for silicic acid formation by FTIR-ATR analysis. The investigation resulted with a bacterial isolate forming a clear zone with a solubilization index (SI) of 3.3. Subsequently, 16S rRNA gene sequencing analysis confirmed the isolate as Etopseudomonas mendocina. Further a comparative silicase activity of the bacterial isolate showed its maximum activity of 1.67 ± 0.06U/mL on in rice husk against other agro residues viz, rice straw, wheat husk and wheat straw. FTIR-ATR analyses confirmed the presence of silicic acid in the crude extracts of the agro residues after culture with the bacterial isolate, with characteristic peaks at 3400-3200, 1600-1650, and 1100-1300cm-1. The research findings reveal that the bacterial isolate effectively biodegrade silica-rich agricultural residues and may have potential applications in agro-residue management. These degradative products could be used as Si-based biofertilizers for sustainable agricultural practices.

Silica oligomers formed in solutions are difficult to characterize due to their size and chemical dynamics. Raman spectroscopy is well suited to track such structures, provided that a clear and unambiguous identification of the compounds is established. We report a comprehensive theoretical and experimental study of the spectra of key polysilicic acids species. We compute ab initio spectra at both the harmonic static and molecular dynamics levels that we compare with experimental Raman spectra. Silica-containing solutions with different polymerization ratios were obtained by tuning the pH in an aqueous media. Finally, we unambiguously assign vibrational modes to linear, cyclic, and cage-like silica oligomers. Our findings reveal trends in the νsym(Si-O-Si) band that correlate with the backbone structure supporting its use for the unique determination of these oligomers enabling reliable, quick and easy in situ identification of silicic acid oligomers in soluble silica mixtures.

In 2017–2019, in a field experiment in Sahryń, Poland (50°40′42″ N, 23°47′35″ E), the effect of foliar application of various forms of silicon (calcium silicate—CS, sodium metasilicate—SM, and micronized silica—MS) and the timing of their application (at the 6-leaf stage of sugar beet, 7 and 14 days later) at single and double doses on physiological parameters, yield, and technological quality of sugar beet roots was studied. The silicon form significantly modified all assessed physiological parameters (NDVI, LAI, and PAR absorption) at all measurement dates. The application date had a significant effect on the assessed parameters at later measurement dates, while the product dose had essentially no effect. The silicon form significantly affected root yield and technological quality, with the exception of α-amino nitrogen content, biological sugar yield, and pure sugar yield. Foliar application of CS and SM resulted in the highest root yield, biological sugar yield, and pure sugar yield, as well as the highest sugar content and the lowest Na content in CS roots. The timing of foliar application significantly affected root yield, biological sugar yield, and α-amino N content. The highest root yield (88.53 t ha−1) and biological sugar yield (15.47 t ha−1) were achieved when the application was performed 14 days after the 6-leaf stage. Simultaneously, the technological quality of the roots deteriorated due to a significant increase in α-amino N content. Application of a double dose of the product significantly increased sugar content and decreased Na content in the roots.

Abstract We present measurements of silicon isotopes in silicic acid, δ 30 Si, from GEOTRACES GP17 OCE between 20°S and 60°S along 152°W. The section sampled key water masses, allowing assessment of controls on large‐scale δ 30 Si features. Observational data paralleled results of a data‐constrained Si isotope model and are consistent with nutrient trapping and partial nutrient consumption in polar surface waters leading to the accumulation of light silicon isotopes in the deep Southern Ocean (SO) and transport of the residually heavy fraction northward within Sub‐Antarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). Deep‐water δ 30 Si values were nearly constant along isopycnals in the South Pacific, with vertical gradients driven by an increasing fractional contribution of isotopically light regenerated silicic acid with depth. Isotope values in deep waters from the SO to Tahiti exhibited a greater range than previously observed in the South Pacific or predicted by models, with δ 30 Si falling between 1.19‰ and 1.45‰. SAMW and AAIW exhibited relatively heavy, uniform δ 30 Si. Model results suggest that these mode waters are composed of preformed silicic acid subducted in the outcropping region and regenerated silicic acid sourced in roughly equal measure from polar waters and northern distal sources. Distal input is mainly through entrainment of underlying Upper Circumpolar Deep Water into AAIW.

Oil-in-dispersion emulsions co-stabilized by CO2-switchable dicarboxylic acid surfactants and silica nanoparticles

Development of a double-network gel foam based on sodium carboxymethyl cellulose with enhanced extinguishing and re-ignition resistance performance for tank fires.

Biomineralization evolved repeatedly across animals, resulting in novel strategies for buoyancy, locomotion, and defense. Sponges are the only metazoans that build a silica-based skeleton and the mechanisms underlying their biosilicification are relatively understudied compared to other major silicifiers. Here, we show that in freshwater sponges, cells specialized for biosilicification, termed sclerocytes, highly express lysosomal-associated genes, including the V-H+-ATPase (VHA) proton pump, oculocutaneous albinism type 2 (OCA2) anion channels, cathepsins, silicateins, TMEM55A/B, TMEM192, TMEM199, and other proteins involved in lysosomal maintenance and degradation. We demonstrate that VHA protein localizes to the sclerocyte silica deposition vesicle (SDV) and that VHA-dependent SDV acidification is essential for silica spicule formation. This function mirrors the role of VHA in diatom biosilicification and in biocalcification across a broad sweep of taxa. We also found that genes homologous to the plant silicon efflux transporter Lsi2 are highly upregulated in sclerocytes and confirmed their localization using Hybridization Chain Reaction Fluorescence In Situ Hybridization (HCR-FISH). These results corroborate phylogenetic and transcriptomic evidence that Lsi2 homologs are involved in sponge silicic acid transport. Data mining of previous studies revealed many of the sponge sclerocyte lysosomal-associated genes have been correlated with biomineralization across eukaryotes, including coccolithophores, bryozoans, crustaceans, mollusks, and mammals. As detoxification was a likely driver for the evolution of biomineralization, we propose that lysosomal machinery aided in detoxification by allowing sponges to sequester Si in acidified compartments to prevent its catastrophic intracellular precipitation. This lysosomal toolkit was likely independently co-opted for the formation of biomineralized structures in multiple species.

Dissolved silicic acid (Si) in groundwater can reduce the As-removal performance of adsorbents used for treating contaminated water. However, its effects on Mg-based adsorbents remain largely unexplored. In this study, As-removal tests were conducted under various test conditions to evaluate the suitability of Mg-based adsorbents (MgO, Mg(OH)2, and MgCO3) for the purification of As-contaminated water in the presence of Si. As-removal performance varied significantly depending on the Mg-based adsorbent type and dosage (WAd0/V), As valence, and the initial As and Si (CSi0) concentrations. In some cases, As removal improved at relatively low CSi0; however, overall performance decreased with increasing CSi0 for all Mg-based adsorbents. Moreover, compared with Mg(OH)2, the performance of MgO and MgCO3 was more strongly affected by Si. This inhibition is attributed to competition between Si and As for adsorption sites on the adsorbent surface. Furthermore, for MgO and MgCO3, the amount of As removed by coprecipitation with secondarily generated Mg(OH)2 aggregates was inferred to decrease with increasing CSi0, because higher CSi0 lowered the solution pH. Overall, MgO and Mg(OH)2 can function effectively as adsorbents for As treatment when WAd0/V is appropriately selected, considering the range of Si concentrations typically found in groundwater.

Opaline silica bodies (phytoliths) are found in plants, particularly grasses, and primarily contribute to plant strength and protection. They form from silicic acid, which is transported from the soil to the leaves – a process that is still being researched. Key transmembrane proteins involved in this transport are Lsi1, Lsi2, Lsi3, and Lsi6, with Lsi1 being the most well understood. Our study focuses on determining the structures of Lsi2, Lsi3, and Lsi6 in rice, revealing an α-helix composition and heterogeneous silicon transport sites, with findings validated using AlphaFold2. Lsi1 and Lsi6 share highly comparable structures, while Lsi2 and Lsi3 also show significant structural similarities. Previous research has shown that in certain regions, the pore sizes of Lsi1 proteins are smaller than Si(OH)4, facilitating effective silicic acid transport through hydrogen bonding with amino acids. Molecular dynamics (MD) simulations over 200 ns demonstrate that this hydrogen bonding enhances the transport of Si(OH)4 during protein conformational changes. Using quantitative real-time PCR (qRT-PCR), the OsLsi3 gene was expressed most strongly in the root, in both wild and cultivated rice plants. Spectrophotometric analysis revealed significant variations in silicon content across different tissues, with the root displaying the highest intensity around ∼ 415 nm, indicating greater silicon concentration. Together, these structural, expression, and compositional analyses provide new insights into the organisation and potential functional roles of silicon transporters in rice. Our research paves the way for improving secure and sustainable rice yield through the precise manipulation of the selectivity of Lsi2, Lsi3, and Lsi6.

This preclinical study evaluated feasibility of an injectable biodegradable silica hydrogel depot formulation for subconjunctival drug delivery into the eye utilizing dexamethasone as active component. The silica hydrogel formulation was manufactured using spray-dried silica microparticles with encapsulated dexamethasone which were mixed with a silica hydrogel to form a continuous solid phase within an aqueous liquid phase. The formulation was then analyzed for dexamethasone and silica contents, rheology, injectability, as well as in vitro dissolution of dexamethasone and silica. Finally, the formulation was studied for pharmacokinetics and release of dexamethasone in the rabbit after subconjunctival injections for 26days. Dexamethasone and silica release profiles in vitro and in vivo were compared with pharmacokinetic simulations made in silico. Dexamethasone was efficiently encapsulated within a visually white, homogenous, shear thinning and injectable hydrogel consisting of silica microparticles with an average diameter of 2.5µm and a span of 3.5µm. The hydrogel depot dissolved completely in vitro in sink in few days. In the rabbit study dexamethasone levels were measurable in both plasma and vitreous up to 26days post injection. Pharmacokinetics was modelled in silico and a predictive tool was generated to support iterative formulation development. Silica hydrogel depot is a promising carrier material for subconjunctival injection of dexamethasone. Pharmacokinetic modelling is a useful tool for optimization of subconjunctival controlled release formulations and for refining the design of animal studies. Chemical compounds studied: Dexamethasone, Silicic Acid, Non-porous Silica.

Protonation-induced blue coloration and photostability of beta-carotene by adsorption on acidic silica materials

Silicon exists in diverse chemical forms and, despite its low abundance in mammals, plays essential roles in skeletal and connective-tissue biology. Many marine organisms, particularly diatoms, have evolved sophisticated pathways for the controlled uptake, transport, and polymerization of silicic acid to generate mechanically robust, intricately patterned silica architectures. These natural systems challenge classical views of silicon as biologically inert and provide molecular blueprints for engineering silicon-biological interfaces. Advances in synthetic biology, mutagenesis, and materials science now enable rapid and programmable modulation of silicification beyond evolutionary time scales. This Perspective highlights recent progress across molecular, cellular, and tissue levels, outlining strategies, challenges, and opportunities for biosilicification as a platform to enhance biomaterial performance, preserve living systems, and integrate synthetic and biological matter.

Silicon has traditionally received limited attention in poultry nutrition compared to macro and trace minerals, yet increasing evidence suggests it plays important physiological roles relevant to modern intensive production systems. This review compiles current knowledge on the presence, metabolism, and nutritional value of silicon in poultry, focusing on skeletal health, performance results, and egg quality. Silicon is common in plant and mineral feed ingredients but exists in various chemical forms that vary widely in solubility and biological availability. Although not traditionally considered essential, silicon appears to support collagen production, cartilage growth, and the mineralization of bone and connective tissue. Reported benefits of dietary supplementation include stronger tibias in broilers, improved bone stability in laying hens, and, in some cases, better eggshell quality and overall performance. Potential effects on gut health and immune function have also been suggested. However, results across studies are inconsistent. Variations likely stem from differences in silicon sources’ chemical structure, interactions with dietary calcium and phosphorus, environmental stressors, and the bird’s developmental stage. Bioavailable forms like orthosilicic acid seem more effective than less soluble silicates, but standardized methods for measuring availability are limited. Importantly, the gap between known requirements and typical dietary intake remains unclear, and silicon is not yet universally recognized as essential for poultry. Overall, silicon is a promising yet incompletely understood nutrient with practical potential to reduce skeletal issues, enhance longevity in layers, and improve welfare. Future research should focus on elucidating absorption pathways, establishing safe and effective supplementation levels, and exploring interactions with key minerals and gut health. A clearer understanding of silicon biology will help incorporate this overlooked element into evidence-based poultry nutrition strategies.