Dissolution behavior of CaO-MgO-SiO2-based bioceramic powders in simulated physiological environments

In this study, the dissolution behavior of CaO-MgO-SiO₂-based bioceramics was investigated in vitro by using a stage-by-stage simulating physiological environment method. Preliminary dissolution rules of CaO-MgO-SiO₂-based bioceramics are presented by soaking akermanite, bredigite, and diopside powders in saline solution. Dissolved Ca and Mg ion concentrations were proportional to the chemical composition of the bioceramics, while the dissolution of Si ion was more affected by their crystal structure. The analysis of zeta potential indicated that ions (possibly including both the dissolved and intrinsic ions) would be adsorbed on the surface of bioceramic powders during soaking in saline solution. Further studies of the dissolution of akermanite powder was performed using different solid-liquid ratios in simulated body fluid (SBF) and α-MEM culture medium. It was found that hydroxyapatite was formed on the surface of akermanite in SBF and amino-containing compounds attracted to the surface of the powders in α-MEM culture medium would impede the diffusion of ions to delay ions release and weaken hydroxyapatite formation. When akermanite powders were co-cultured with BMSCs, HUVECs, or L929 cells, the concentrations of Ca, Mg and Si ions in the solution were lower than that in cell-free medium. Additionally, the pH value gradually decreased with soaking time, unlike what occurs when the materials are soaked in cell-free media, suggesting effects due to the cellular intake of related ions and the release of acidic cellular metabolites. The akermanite extracts in a certain concentration range could promote cell proliferation via cellular intake of related ions. In turn, this ion consumption would affect the dissolution behavior of bioceramics in simulated physiological environments.     

Adsorption of Mercury(II), Lead(II), Cadmium(II) and Zinc(II) from Aqueous Solutions using Mercapto‐Modified Silica Particles

This article presents a novel systematic approach to the fabrication of highly functionalized, silica (SiO₂) nanoparticles used for the adsorption of heavy‐metal ions (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺). Almost monodispersed silica (SiO₂) nanoparticles with narrow particle size distributions of around 85 ± 5 nm were formed using the Stöber process. The prepared SiO₂ nanoparticles were successfully surface‐treated during a one‐step procedure by the covalent attachment of mercaptopropyl groups onto the surfaces of the SiO₂ nanoparticles. A FTIR spectra analysis confirmed that the binding of the mercaptosilane molecules onto the surface of the silica nanoparticles mediated the Si–O–Si and –SH vibrations. TEM/EDXS micrographs indicated the almost monodispersed and spherical morphology of the prepared product with strong signals of Si and S, thus implying that the coating procedure involving the mercapto groups onto the silica surface had been successfully accomplished. The final results for the heavy‐metal (Hg²⁺, Pb²⁺, Cd²⁺, Zn²⁺) adsorption showed the strongest affinity within the following sequence Hg²⁺ (99.9%) > Pb²⁺ (55.9%) > Cd²⁺ (50.2%) > Zn²⁺ (4%). Adsorption equilibrium was achieved after 1 h for all the analyzed samples.     

Preparation,Characterization, and In Vitro Bioactivity of Nagelschmidtite Bioceramics

The aim of this study is to prepare Ca, P and Si‐containing ternary oxide nagelschmidtite (NAGEL, Ca₇Si₂P₂O₁₆) bioceramics and explore their in vitro bioactivity for potential bone tissue regeneration. We prepared dense NAGEL ceramics through high‐temperature sintering of NAGEL ceramic powders. The apatite‐mineralization ability, dissolution rate, and human osteoblast response (including cytotoxicity analysis, attachment, morphology, proliferation, and bone‐related gene expression) to NAGEL ceramics have been systematically studied by comparing with conventional β‐tricalcium phosphate (β‐TCP) ceramics. The results showed that NAGEL ceramics possessed more obvious apatite mineralization and dissolution (degradation) and stimulated bone‐related gene expression (OCN and OPN) of osteoblasts than β‐TCP ceramics. NAGEL ceramics also showed no significant cytotoxicity. NAGEL ceramics supported osteoblast attachment, proliferation, and osteogenic gene expression, with a comparable cell proliferation activity with β‐TCP ceramics. These results indicate that novel NAGEL bioceramics with the specific composition of Ca₇Si₂P₂O₁₆, are a promising biomaterial for bone tissue regeneration application.     

Preparation of conductive polyaniline/nanosilica particle composites through ultrasonic irradiation

Polyaniline/nano‐SiO₂ particle composites were prepared through ultrasonic irradiation. Polymerization of aniline was conducted under ultrasonic irradiation in the presence of two types of nano‐SiO₂: porous nanosilica and spherical nanosilica. The stability of the colloid dispersion, UV–vis spectra, composition, interaction, conductivity, and other characteristics of the composites were examined. It was found that the aggregation of nano‐SiO₂ could be reduced under ultrasonic irradiation and that nanoparticles were redispersed in the aqueous solution. The formed polyaniline deposited on the surface of the nanoparticle, which led to a core–shell structure. Two particle morphologies, threadlike aggregates with a few spherical nanoparticles for porous nanosilica and spherical particles with a few sandwichlike particles for spherical nanosilica, were observed. X‐ray photoelectron spectroscopy showed that for two types of composites the ratio of Si atoms to N atoms (Si:N) on the surface was much higher than that in the bulk. The UV–vis spectra of the diluted colloid dispersion of polyaniline/nano‐SiO₂ composite particles were similar to those of the polyaniline system. Fourier transform infrared spectroscopy suggested strong interaction between polyaniline and nano‐SiO₂. The conductivity of the polyaniline/porous nanosilica (23.1 wt % polyaniline) and polyaniline/spherical nanosilica (20.6 wt % polyaniline) composites was 2.9 and 0.2 S/cm, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1811–1817, 2003     

Resolving the Interface of Calcium Phosphate Formation on the Porous Bioceramics In Vitro

Porous bioceramics have been widely studied for bone tissue engineering. A deep understanding on the mechanism of bone growth and biomineralization depends on the extracted interface information between the new precipitated calcium phosphates (CaPs) and the porous substrate at a nanometer scale. However, due to their intrinsic brittleness and the complexity of the sample shape, there is still lack of such information. Here, by a combination of focused ion beam (FIB) and transmission electron microscopy (TEM), in‐situ cross‐sectional electron transparent interface was prepared. The precipitated dense apatite layer is composed of individual microgranules which further consist of tiny flake‐like crystals. The new crystallites grow along c‐axis and are mostly oriented perpendicular to HA substrate. This preferred orientation is more pronounced in the presence of protein. This work offers a novel and feasible approach using FIB‐TEM to in situ image porous bioceramic scaffold and precipitated apatite layer interface and can be extended to study many other biointerfaces.     

Preparation and Antibacterial Activities of Porous Silver‐doped β‐Tricalcium Phosphate Bioceramics

Infection is still a major concern in bone implants, especially in the implants with porous structures. As silver shows superior and broad‐spectrum antibacterial activity, porous silver‐doped β‐tricalcium phosphate (β‐TCP) bioceramics are prepared with 5% and 10% nanometer silver. The bioceramics show similar porous macrostructure with pure β‐TCP bioceramic, except slightly color change. They have almost identical microstructure to its pure β‐TCP counterpart under field emission scanning electron microscope. Their physical, chemical, and mechanical properties were investigated with X‐ray diffraction, Fourier transforming infrared spectrometer, and AG‐5kN, and no significant difference has been found between silver‐doped β‐TCP bioceramics and pure β‐TCP bioceramic. Bactericidal concentration of silver ions was detected in the solution soaked with the bioceramics. They can efficiently inhibit the growth of Staphylococcus epidermidis and Styphylococcus aureus, but show no cytotoxicity to L929 cells. It suggests that silver‐doped β‐TCP bioceramics can be developed into new type of bone substitutes with anti‐infection properties.     

Synthesis and properties of Zn and Zn–Mg-doped tricalcium phosphates obtained by Spark Plasma Sintering

β-tricalcium phosphate (Ca₃(PO₄)₂ or TCP) are essential biomaterials because of the chemical composition, high biocompatibility and osseointegration. However, their limited mechanical properties restrict their use to areas where high mechanical performances are not required. Spark Plasma Sintering (SPS) was selected out of the unconventional sintering methods in order to obtain high-density doped-TCP bioceramic materials. The main advantages of SPS are a high heating rate, low sintering temperatures and short residence times, producing bioceramics with full density and fine-grain microstructure. The main purpose was to design, obtain by SPS and characterize undoped β-TCP, 1ZnO-doped β-TCP and 1ZnO-1MgO codoped β-TCP (wt. %) bioceramics. All the obtained samples were visually semitransparent and mainly β-TCP was detected by X-ray analysis. Densification behavior was determined by Archimedes' method and microstructural features of the sintered specimens were analyzed by Field Emission Scanning Electron Microscopy (FE-SEM-EDX). The undoped and doped β-TCP bioceramics were mechanically characterized, specifically the modulus of elasticity and Vickers microhardness. The results are compared with equivalent samples obtained by conventional solid-state sintering (CS) reaction. A first study of biological behavior was carried out, specifically direct cell adhesion of MG-63 human osteoblast-like cells on the polished surfaces of β-TCP, 1ZnO-β-TCP and 1ZnO–1MgO-β-TCP dense samples were determined. The present study concludes that the SPS process together with the doping effect enhanced sinterability, mechanical and biological properties of Zn-TCP and Zn–Mg-TCP based materials.     

The dissolution behavior in alkaline solutions of a borosilicate glass with and without P2O5

There are a variety of applications for glasses in alkaline environments, including glass fibers and glass‐coated steel to reinforce concrete structures. To understand how a simple glass reacts in such environments, the dissolution behavior of a 25Na₂O–25B₂O₃–50SiO₂ (mol%) glass, doped with and without 3 mol% P₂O₅, in pH 12 KOH and pH 12 KOH saturated with Ca²⁺ ions was studied. Ca²⁺ ions in the solution significantly reduce the glass dissolution rate by forming a passivating calcium silicate hydrate (C–S–H) gel layer on the glass surface. When these corroded glasses were then exposed to Ca‐free KOH, the C–S–H layer redissolves into the undersaturated solution and the glass dissolution rate increases. For phosphate‐doped borosilicate glass, PO₄^3? units released from the dissolving glass react with Ca²⁺ ions in saturated solutions to form crystalline hydroxylapatite on the glass surface, but this layer does not protect the glass from corrosion as well as the C–S–H does. The nature of the C–S–H layer was characterized by Raman spectroscopy, which reveals a gel layer constituted mainly of silicate anions.     

Design Strategy for the Multilayer Core–Shell Bioceramics with Controlled Chemistry

New strategies for fabricating multiphase bioceramic porous scaffolds with time‐dependent biodegradation and pore network enlargement are of fundamental importance in the advancement of bioceramics. Here, we developed a one‐step preparation of core–shell bioceramic microspheres (~2 mm in diameter) with single‐ or double‐shell structure through a coaxially aligned multilayer capillary system. The Ca‐phosphate (CaP) and Ca‐silicate (CaSi) ceramic phase distribution could be also adjusted by extruding through different capillaries, and thus the biodegradation rate would be readily tailored over time. When the polystyrene (PS) microbeads of ~15 μm in diameter were premixed into the CaP‐ or CaSi‐containing alginate slurry, the tailorable porous structures could be introduced into the core or different shell layers of the microspheres. These micropores may potentially maximize the permeability for rapid exchange of guest molecules or inorganic ions from the bioceramics. Totally, such strategy is promising because the ceramic phases with different biological properties can be assembled into the core–shell bioceramic microspheres, and thus the macropore structure evolution may be readily manipulated in the closely packed microsphere systems. We believe our gradient hybrid methodology will have potential in various categories of advanced biomaterials of organic–inorganic composites.     

In vitro degradation and apatite-formation of ZnO–CaO–SiO2–P2O5 glass–ceramics by substitution of zinc for calcium

A series of CaSiO₃–Ca₂ZnSi₂O₇-based glass–ceramics of the type ZnO–CaO–SiO₂–P₂O₅ were successfully obtained by the partial substitution of calcium with zinc. The effect of zinc addition on structure, dissolution behavior and apatite-forming ability of the resultant glass–ceramics was comprehensively investigated by X-ray diffraction (XRD), thermogravimetric and differential scanning calorimetry (TG/DSC), and scanning electron microscopy coupled to an energy dispersive X-Ray spectrometer (EDS). The data revealed that the zinc addition favored the generation of Ca₂ZnSi₂O₇ and induced the formation of ZnSiO₄ and SiO₂ phases. In addition, the excessive content of these compounds led to the attendant loss in the dissolution rate and apatite-forming ability, indicating that the incorporation of zinc into CaSiO₃ is a promising route to regulate the dissolution and apatite formation of CaSiO₃–Ca₂ZnSi₂O₇- based bioceramics.     

Preparation and in vitro assessment of economic bio-scaffolds modified with wollastonite (CaSiO3)

Porous bioceramic scaffolds are the preferred option for substituting spongy bone. Therefore, this study evaluates the use of carbonate associated with apatite rocks at Hamadat mines (referred to as calcite) as a source of low-cost bioactive material useful for biomedical applications. In this study, the depositional environment and mineralogical, and petrographic behavior of such depositions were studied. Furthermore, the possibility of producing highly porous, low-cost bioceramic scaffolds using the freeze-drying technique was demonstrated. The bioactivity of the produced scaffolds was enhanced by adding different ratios of wollastonite (25, 50 and 75 wt %) to the scaffold’s batches. However, the scaffolds were coated with ZnCl₂ to enhance their antimicrobial susceptibility. The physical and mechanical properties as well as the phase composition and microstructure of the prepared scaffolds were investigated. The X-ray diffraction results revealed the formation of pure phase of α-wollastonite after 3 h of sintering at 1200 °C. To estimate the scaffolds’ biodegradability, the pH and the weight change were measured. The results were confirmed using the inductively coupled plasma measurements for the scaffolds deposited in a simulated body fluid (SBF) solution for 28 days. Results showed that the scaffolds had excellent bioactivity, which was demonstrated by the appearance of apatite particles on their surface after being immersed in the SBF. The antimicrobial activity test revealed that Zn²⁺, NPs and CaSiO₃ had positive effects due to their oxidative stress process. Zn²⁺, Ca²⁺, and Si⁴⁺ cations can be adsorbed on bacterial surface membranes, interacting with the respiratory microbial enzymes, inhibiting their actions, and damaging the cell, thereby causing the bacterial cell decomposition.     

High-strength and tough bioactive Mg-doped hydroxyapatite bioceramics with oriented microchannels

Mg-doped hydroxyapatite (MH) with oriented microchannels was prepared by hot-pressing sintering and pore-forming heat treatment using continuous carbon fibres (CFs) as the pore-forming agent to achieve balanced mechanical and biological properties. The proportion of MH and (Ca, Mg)₃(PO₄)₂ in the microporous bioceramic with inter-microchannel spacing of 400 μm obtained by sintering at 900 °C (900-2P-MH) was 43.9/56.1 (wt%), which could promote degradation. The compressive strength of the MH bioceramics containing oriented microchannels with a suitable pore size (5–14 μm) did not decrease, but increased in comparison with that of a dense MH sample without microchannels. In particular, the compression strength of the MH bioceramic with oriented microchannels formed using single CF units was 53.31% higher than that of the dense ones. The fracture toughness of the MH bioceramics with oriented microchannels increased to 177.42% of that of the dense ones. The strengthening and toughening mechanism includes contributions from the combination of heating and pressing, uniform distribution of microchannels, and in situ formation of continuous micro/nano-MH ceramic tubes. Moreover, the microchannel-containing MH showed noticeably improved apatite mineralisation in simulated body fluid (SBF). Analysis of the rat tibial bone defect model revealed that the relative bone volumes in the cases of the dense MH without microchannels and the MH with microchannels increased by 23.18 and 40.14%, respectively, compared with that of hydroxyapatite. Furthermore, the MH bioceramics with oriented microchannels displayed a moderate reduction in strength owing to degradation after 8 weeks of implantation. The satisfactory osteogenic properties and degradability of the microporous bioceramic can be attributed to Mg²⁺ doping and oriented microchannels.     

A novel approach to prepare PBT nanocomposites with elastomer‐modified SiO2 particles

Poly(butylenes terephthalate) (PBT)/SiO₂ nanocomposites with uniform dispersion, strong interfacial adhesion, and improved mechanical properties have been prepared by a novel approach. Ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) elastomer chains were first chemically grafted onto the surface of SiO₂ nanoparticles. Fourier transform infrared spectra result shows that elastomer‐modified SiO₂ nanoparticles exhibit absorption at 2963–2862 cm⁻¹ of the stretching modes of C H, which suggests the reaction between the hydroxyl groups of SiO₂ surface and epoxy groups of E‐MA‐GMA. And the binding energy of Si2p and O1s of the elastomer‐modified SiO₂ shifts to lower binding energy, which further confirms the formation of Si O C bonds. This surface treatment allows SiO₂ nanoparticles homogeneously dispersing in PBT matrix. The morphology with loose aggregates contains networked SiO₂ particles with an interparticle distance ranging from 0 to 30 nm. As a result, the storage modulus and the tensile properties of PBT/E‐MA‐GMA‐SiO₂ nanocomposites are higher than those of pure PBT and PBT with untreated SiO₂. The incorporation of E‐MA‐GMA‐modified SiO₂ particles increases the tensile strength and modulus to 58.4MPa and 2661MPa respectively, which is 8% and 16% higher than those of pure PBT. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Quartz Dissolution as Influenced by pH and the Presence of a Disturbed Surface Layer

Quartz particles (10 to 2 microns in diameter, produced by grinding) released 45 ppm of SiO₂ to a buffer solution of pH 7 during a 48 hr period. The grinding of quartz particles produced a disturbed surface layer with solubility properties intermediate between crystalline quartz (6 ppm SiO₂) and amorphous silica (120 ppm SiO₂). Removal of the disturbed layer by treatment with 1N HF lowered the SiO₂ dissolution from 45 to 3 ppm. Use of 12N HF decreased the amount of SiO₂ dissolved to 2 ppm, a result found to coincide with a preferential dissolution of the finer quartz particles in addition to the removal of the disturbed surface layer. The rate of dissolution of SiO₂ from quartz particles, subsequent to treatment with 1N HF, increased with decrease in particle size, from 1 to 3 ppm for quartz particles 50 to 20 microns in diameter to 30 to 44 ppm for particles 2 to 0.2 microns in diameter, during each of three consecutive 14-day extractions with pH 7 buffer solution. The amount of SiO₂ dissolved from quartz in buffer solutions increased in the pH range of 4 to 10, from 0.6 ppm of SiO₂ at pH 4 to 19 ppm at pH 10 during a 14-day period of extraction from quartz particles, 10 to 2 microns in diameter. Quartz particles, subsequent to the removal of the disturbed surface layer, removed SiO₂ from pH 4 and pH 8 buffer solutions prepared with more SiO₂ in solution than would be released from quartz in the respective solution.     

PEGylated hollow pH‐responsive polymeric nanocapsules for controlled drug delivery

Novel pH‐responsive PEGylated hollow nanocapsules (HNCaps) were fabricated through a combination of distillation–precipitation copolymerization and surface thiol–ene ‘click’ grafting reaction. For this purpose, SiO₂ nanoparticles were synthesized using the Stöber approach, and then modified using 3‐(trimethoxysilyl)propyl methacrylate (MPS). Afterward, a mixture of triethyleneglycol dimethacrylate (as crosslinker), acrylic acid (AA; as pH‐responsive monomer) and MPS‐modified SiO₂ nanoparticles (as sacrificial template) was copolymerized using the distillation–precipitation approach to afford SiO₂@PAA core–shell nanoparticles. The SiO₂ core was etched from SiO₂@PAA using HF solution, and the obtained PAA HNCaps were grafted with a thiol‐end‐capped poly(ethylene glycol) (PEG) through a thiol–ene ‘click’ reaction to produce PAA‐g‐PEG HNCaps. The fabricated HNCaps were loaded with doxorubicin hydrochloride (DOX) as a model anticancer drug, and their drug loading and encapsulation efficiencies as well as pH‐dependent drug release behavior were investigated. The anticancer activity of the drug‐loaded HNCaps was extensively evaluated using MTT assay against human breast cancer cells (MCF7). The cytotoxicity assay results as well as superior physicochemical and biological features of the fabricated HNCaps mean that the developed DOX‐loaded HNCaps have excellent potential for cancer chemotherapy. © 2020 Society of Chemical Industry     

Effect of surface properties of MgO on its dissolution and spinel growth in CaO–SiO2–Al2O3 slag

The dissolution behavior of MgO in CaO–SiO₂–Al₂O₃ ternary slag at the interface of single-crystal, dense poly-crystal, and porous poly-crystal MgO was investigated to evaluate the effect of the surface properties of the MgO. The experimental results revealed that a detached spinel layer formed at the MgO interface due to the change in thermodynamic condition of the slag, which was independent of the surface properties. On the other hand, it was also confirmed that the growth rate and morphology of the detached spinel layer strongly depended on the surface properties, such as porosity and curvature of MgO. During the formation of the spinel layer at the interface during MgO dissolution, a kinetic approach adopting parabolic relation theory was employed to determine the correlation between the surface properties and the spinel growth mechanism.     

In Situ Observation of the Dissolution of SiO2 Particles in CaO–Al2O3–SiO2 Slags and Mathematical Analysis of its Dissolution Pattern

The dissolution of amorphous SiO₂ particles in CaO–Al₂O₃–SiO₂ slags was investigated at 1450°C by high‐temperature confocal scanning laser microscopy (HT‐CSLM) and thermodynamic/kinetic analyses. The SiO₂ particles used in this experimental study had a spherical form so that any rotation of the particle did not cause errors in the determination of the particle size during the dissolution. Moreover, a wide composition range of the slag could be chosen without forming any solid reaction layer which could distort the evaluation of the dissolution mechanism. The evolution of the diameter of the spherical SiO₂ particle was measured by image analysis of pictures obtained from the HT‐CSLM. It was found that the dissolution curve of the SiO₂ particle (size as a function of time) exhibited either a parabolic‐like curve or an S‐shaped curve depending on the slag composition. The patterns were compared with a well‐known shrinking core model (SCM), and it was shown that the SCM could not represent the dissolution behavior of the SiO₂ particle observed in this study. It was experimentally found that the shape of the dissolution curves varies as a function of the slag composition. The curve exhibited a parabolic‐like shape for low SiO₂‐containing slags and changed to an S‐type shape with increasing SiO₂ concentration in the slag. To elucidate the dissolution mechanism, a model based on approximations for the diffusion near the particle was proposed by modifying the previously available model [M. J. Whelan, Met. Sci. J., 3, 95–97 (1969)]. From the experimental data and the model calculations, the viscosity of the slag was shown to be the major factor affecting both dissolution rate and mechanism. Effective binary diffusion coefficients were estimated using the model and experimental data. Those were shown to be in the range of literature data.     

Recent advances on akermanite calcium-silicate ceramic for biomedical applications

Owing to great biocompatibility and high capacity of apatite formation, bioceramics, especially calcium silicate-based compounds, were extensively employed in orthopedic and dental uses concerning biomedical applications. Lately, akermanite (AK; Ca₂MgSi₂O₇), as a bioceramic containing Ca-, Mg- and Si, has gained an increased level of attention because of its more tunable mechanical characteristics and degradation rate. All studies indicate that this magnesium incorporating Ca-silicate ceramic has a great capacity to use as a bone graft material to fulfill the necessity of bone reconstruction. Despite the rising interest in using these materials in biomedical fields, there has not yet been an extensive overview of this bioceramic property and its potential benefits. Thus, it has been speculated that this concept and the emergence of akermanite bioactive ceramics might lead to significant upcoming advancements in the field of bone tissue engineering (BTE). Definitely, the approach still requires additional advances to considerably better respond to the vital concerns regarding the clinical application. The review tackles the present research trends on akermanite ceramics for biomedical purposes such as bone scaffold, coating materials, bone cement, and treatment of osteoporotic bone defects, commencing with recent status and shifting to upcoming developments.     

Highly Porous SiOC Bulk Ceramics with Water Vapor Assisted Pyrolysis

Micro/mesoporous SiOC bulk ceramics with the highest surface area and the narrowest pore size distribution were prepared by water‐assisted pyrolysis of polysiloxane in argon atmosphere at controlled temperatures (1100°C–1400°C) followed by etching in hydrofluoric acid (HF) solution. Their pyrolysis behaviors, phase compositions, and microstructures were investigated by DSC, FTIR, XRD, and BET. The Si–O–Si bonds, SiO₂‐rich clusters, and SiO₂ nanocrystals in the pyrolyzed products act as pore‐forming species and could be etched away by HF. Water injection time and pyrolysis temperature have important effects on phase compositions and microstructures of the porous SiOC bulk ceramics, which have a maximum‐specific surface area of 2391.60 m²/g and an average pore size of 2.87 nm. The porous SiOC ceramics consist of free carbon phase, silicon carbide, and silicon oxycarbide.     

Accelerated bioactive behavior of Nagelschmidtite bioceramics: Mimicking the nano and microstructural aspects of biological mineralization

The ability of the Nagelschmidtite (Nagel) phase to promote osteogenesis, cementogenesis, and angiogenesis increased the interest in using this calcium silicophosphate bioceramic for tissue regeneration and vascularization applications. Nagel phase is a solid solution with the general formula Ca_7-xNa_x(PO₄)_2+x(SiO₄)_2-x, which allows several substitutions being Ca₇(PO₄)₂(SiO₄)₂ the most reported stoichiometry. Inspired by the well-known 45S5 bioactive glass chemical composition, we developed a synthesis route to obtain a Na-rich Nagel single phase. The effect of this bioceramic chemical and structural properties on apatite formation and crystallization mechanism is reported. The structural aspects at the nano and microscale of the mechanism of apatite growth and crystallization from the Nagel phase were compared to the formation process of Extra-Cellular Matrix (ECM) deposits in biological systems, revealing a biomimetic behavior during the apatite biomineralization process from the bioceramic.