Structural Characterization of Gel-Derived Calcium Silicate Systems

Synergistic Effect of Polyethylene Glycol and Lactic Acid on Handling Properties and Antibacterial Efficacy of Premixed Calcium Silicate Cement

Calcium silicate (CaSi) bone cement with antibacterial and osteogenic properties has attracted significant interest. However, there is a need to develop a variety of new premixed bone cement to meet the clinical requirements of fast setting time, ease of handling, and efficient antibacterial properties. In this study, different volume ratios of polyethylene glycol (PEG) and lactic acid liquids were added to calcium silicate, and the effects of varying liquid-to-powder ratios (L/P) were examined. This study assessed the physicochemical properties, cytotoxicity, and antibacterial activity against S. aureus and E. coli of this premixed cement. The results from the experiments indicated that lactic acid significantly reduced the setting time of the CaSi-based cement and enhanced its mechanical strength. Furthermore, the appropriate concentration of lactic acid and matching L/P ratio improved its washout resistance. The cell viability of all premixed cement was found to be over 80%. The premixed cement containing PEG and lactic acid exhibited superior antibacterial properties compared to the CaSi control. Based on its setting time, washout resistance, and antibacterial activity, a premixed cement with a liquid phase of 80% PEG and 20% lactic acid at an L/P ratio of 0.4 appeared promising for use in dental and orthopedic practice.

Spectral Investigations of 60S Bioactive Glass Modified with La and Y Ions

The changes in the atomic structure and in the network of bonds between oxide tetrahedra in 60S bioactive glass upon modification of its structure by yttrium and lanthanum atoms were investigated via XPS, FTIR, and NMR spectroscopy methods. The presence of nanostructure in the samples of 60S bioactive glass modified with yttrium and lanthanum was demonstrated. The formation of a bioinert core of 60S bioactive glass nanoparticles with the subsequent formation of a biocompatible layer is facilitated by the redistribution of electron density when oxygen bridge bonds are broken, PO4 and SiO4 tetrahedra are fragmented in the polymer matrix, and isolated nanoclusters are formed. Given the fact that during the interaction with the extracellular matrix, the breakdown of covalent bonds -O-Si-O-P- is more energetically costly than the rapid ionic exchange of network modifiers Ca2+ (Y3+, La3+) and the leaching of isolated nanoclusters into the surrounding physiological environment, it is argued that modification of 60S bioactive glass with yttrium or lanthanum can accelerate bioactive ionic processes in the extracellular matrix.

Plant-based calcium silicate from rice husk ash: A green adsorbent for free fatty acid recovery from waste frying oil

Driven by the urgent need for a solution to tackle the surge of rice husk (RH) and waste frying oil (WFO) waste accumulation at a global scale, this report highlights the use of calcium silicates (CS) extracted from acid-pre-treated rice husk ash (RHA) for free fatty acid (FFA) removal from WFO as conventional RHA shows limited FFA adsorption performance. A novel alkaline earth silicate extraction method from acid-pre-treated RHA was outlined. The structural and behavioural attributes of the synthesised CS were identified through BET, SEM-EDS, and XRD analyses and compared to those of RHA. Notable morphology and structural modification were determined, including reducing specific surface areas, mitigating from amorphous to crystalline structure with regular geometric forms, and detecting Si-O-Ca functional groups exclusive to CS adsorbents. A comparison study showed superior lauric acid (LA) adsorption performance by CS absorbents over acid-pre-treated RHA, with a significant increase from 0.0831 ± 0.0004 mmol LA/g to 2.5808 ± 0.0011 mmol LA/g after 60 min. Recognised as the best-performing CS adsorbent, CS-1.0 was used for further investigations on the effect of dosage, LA concentration, and temperature for efficient LA adsorption, with up to 100% LA removal and 5.6712 ± 0.0016 mmol LA/g adsorption capacity. The adsorption isotherm and kinetic studies showed LA adsorption onto CS-1.0 followed Freundlich isotherm with KF = 0.0598 mmol(1-1/n) L(1/n) g-1 & Qe,cal = 3.1696 mmol g-1 and intraparticle diffusion model with kid = 0.1250 mmol g-1 min0.5 & Ci = 0.9625 mmol g-1, indicating rapid initial adsorption and involvement of carboxylate end of LA and the calcium ions on the CS-1.0 in the rate-limiting step. The high equilibrium adsorption capacity and LA adsorption rate indicated that the proposed CS-1.0 adsorbent has excellent potential to recover FFA from WFO effectively.

Effects of temperature on the migration behaviour of arsenic and chromium in tannery sludge under CO2 gasification

To reduce heavy metals (HMs) contamination from tannery sludge, this study investigated the migration behaviour of arsenic (As) and chromium (Cr) at 700-900 °C using CO2 gasification. The HMs enrichment results showed that As contents of ash decreased (6.42→1.87 mg/kg) while Cr contents increased (41.40→78.24 mg/kg) over 700-900 °C. More Si-O bonds and fewer Ca-O bonds with increasing temperature in ash primarily determined this migration behaviour of HMs. Meanwhile, the proportions of toxic As(III) and Cr(VI) declined from 96.02% and 64.26-76.96% and 21.24%, forming As(0) and Cr(III) with less toxicity. This reduction was conducted via two pathways: (i) carbon reduced As(III)/Cr(VI) and (ii) carbon reduced Fe(II)/Fe(III) to Fe(0), then Fe(0) reduced As(III)/Cr(VI) assisted with carbon via Fe(0)→Fe(II)→Fe(III). However, free calcium ions oxidized As(0)/Cr(III) to As(III)/Cr(VI) at 700 ○C. At higher temperatures, silicate glass conversion of ash immobilized free calcium ions and barely oxidized HMs. Furthermore, this study identified the positive effect of increasing temperature on enhancing the stability of HMs in ash by transforming bioavailable HMs into non-bioavailable HMs, which decreased the leaching toxicity and environmental risk. Regarding HMs emissions control and cold gas efficiency, CO2 gasification treatment of tannery sludge is most effective at 800 °C.

The Origin of the Intracellular Silver in Bacteria: A Comprehensive Study using Targeting Gold-Silver Alloy Nanoparticles

The bactericidal effects of silver nanoparticles (Ag NPs) against infectious strains of multiresistant bacteria is a well-studied phenomenon, highly relevant for many researchers and clinicians battling bacterial infections. However, little is known about the uptake of the Ag NPs into the bacteria, the related uptake mechanisms, and how they are connected to antimicrobial activity. Even less information is available on AgAu alloy NPs uptake. In this work, the interactions between colloidal silver-gold alloy nanoparticles (AgAu NPs) and Staphylococcus aureus (S. aureus) using advanced electron microscopy methods are studied. The localization of the nanoparticles is monitored on the membrane and inside the bacterial cells and the elemental compositions of intra- and extracellular nanoparticle species. The findings reveal the formation of pure silver nanoparticles with diameters smaller than 10 nm inside the bacteria, even though those particles are not present in the original colloid. This finding is explained by a local RElease PEnetration Reduction (REPER) mechanism of silver cations emitted from the AgAu nanoparticles, emphasized by the localization of the AgAu nanoparticles on the bacterial membrane by aptamer targeting ligands. These findings can deepen the understanding of the antimicrobial effect of nanosilver, where the microbes are defusing the attacking silver ions via their reduction, and aid in the development of suitable therapeutic approaches.

Low temperature preparation of diopside nanoparticles: in-vitro bioactivity and drug loading evaluation

Bioactive diopside (CaMgSi2O6) nanoparticles have recently gained potential usefulness as bone replacement materials and nano vehicles for delivering therapeutics. The structural characteristics of this ceramic have found to be a key factor in bone bonding ability. To attain the desired product for 100% clinical success, it is important to realize the relationship between structure and biological activity. Synthesis of these nanoparticles via the solid-state method has been regarded as a low-cost and easy process in large-scale, but time consuming reactions and high temperature (≈ 1400 °C) are required. On the other side, the wet chemistry can overcome these drawbacks, whereas the presence of byproducts in the final powder has limited this method in large-scale production. The present document has represented a simple, fast and one-pot sol-gel approach for the synthesis of highly pure diopside nano-powders (< 20 nm) by using not-expensive precursors. Calcination of the obtained powder has been conducted at various temperatures (700, 1000 and 1200 °C). The physicochemical and microstructural properties of the products have been characterized by XRD, FTIR, FESEM and TEM. Moreover, the impact of the crystallinity on the bioactivity, drug loading capacity and drug release behavior of the synthesized nanoparticles have been investigated here for the first time. The in-vitro bioactivity results of the prepared diopside samples in a simulated body fluid (SBF) at 37 °C revealed the higher capability of the sintered sample to deposit calcium phosphate, compared with the amorphous one. High quantity of gentamicin (around 10 µg) could attach to the surface of 1 miligram of the sintered diopside during the early stages of contact (3 h), suggesting the potential use of diopside as a new class of nano-vehicles for antibiotics. The release behavior indicated a sustained release of gentamicin (80%) after 24 h. In conclusion, diopside nanoparticles can be a promising candidate as a drug-vehicle for bone filling, implant coating or bone cement applications.

V and Cr substitution in dicalcium silicate under oxidizing and reducing conditions - Synthesis, reactivity, and leaching behavior studies

Dicalcium silicate (C₂S) is known to incorporate potentially hazardous metals (Cr and V) in a belite-rich cementitious system. The effect of the electrovalence nature of V and Cr on C₂S polymorphs' (α´, β, γ) stability under oxidizing and reducing conditions as well as their reactivity are systematically investigated via analyzing oxidation states, phase composition, bonding system, and microstructure as well as oxide composition quantitively. It is shown that C₂S can incorporate Cr (VI) and V(V) consequently leading to stabilization of α´, β-C₂S. Instead, Cr (II, III) and V < (V) tend not to substitute in C₂S. Despite reactive polymorphs (α´, β-C₂S) stability due to Cr (VI) and V(V) incorporation, the early age (48-72 h) C₂S reactivity is drastically reduced due to Cr (VI) and V (V) incorporation. Moreover, one batch leaching test revealed that the V (V) leaching is inversely proportional to aqueous Ca²⁺ ion at pH > 12 while Cr leaching is sensitive to its oxidation state, and dissolution of C₂S. Even though C₂S can incorporate Cr (VI) and V (V) ions, the final leaching is governed by the immobilization potential of C-S-H gel, pH as well as types of calcium chromate and vanadate complexes.

Fly ash derived calcium silicate hydrate as a highly efficient and fast adsorbent for Cu(ii) ions: role of copolymer functionalization

The environmental issues caused by heavy metal accumulation from polluted water are becoming serious and threaten human health and the ecosystem. The adsorption technology represented by calcium silicate hydrate has attracted much attention, but suffers from high manufacturing costs and poor stability bottlenecks. Here, we have proposed a "trash-to-treasure" conversion strategy to prepare a thin sheet calcium silicate hydrate material (ACSH) using solid waste fly ash as silicon source and a small amount of Acumer2000 as modifier. The obtained materials showed fast adsorption rates, superior adsorption capacities and remarkable long-term stability for Cu(ii) removal. Under the conditions of 0.5 g L-1 adsorbent concentration and 100 mL Cu(ii) solution with a concentration of 100 mg L-1, ACSH can adsorb 95.6% Cu(ii) within 5 min. The adsorption isotherms conformed to Langmuir models and the maximum adsorption capacity was 532 mg g-1. Using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, specific surface area and pore structure analysis, it was found that the excellent adsorption performance could be attributed to the ultrahigh surface area (356 m2 g-1), abundant pores and multiple active sites induced by Acumer2000 modification. Moreover, the encapsulation effect from carboxylate and long carbon chains in Acumer2000 endowed modified samples with strong corrosion resistance to CO2, which effectively inhibited the formation of by-product CaCO3 and retained the remarkable adsorption performance for more than 100 days. Interestingly enough, the advantages of ACSH in economy and performance could been maintained in ACSH based adsorptive membranes. This work is of great significance for solid waste utilization as well as the preparation of high quality, cost-effective and long-term stability calcium silicate hydrate materials.

Two-Dimensional calcium silicate nanosheets for trapping atmospheric water molecules in humidity-immune gas sensors

In humid conditions, water vapor can easily neutralize the surface active sites of metal oxide sensors, leading to a lowering in the sensitivity of the gas sensor and a resultant inaccurate signal in practical applications. Herein, we present a new hybrid sensor by introducing a two-dimensional calcium silicate (CS) nanosheet as a water-trapping layer in SnO₂ nanowires. Unlike the heavily wrinkled and aggregated morphology of conventional CS nanosheets, our nanosheet in the hybrid material is ultrathin and flat. Moreover, it was grown in the empty spaces between the spider-web-like networks of SnO₂ nanowires without covering the nanowire surface. These two morphological features improve moisture trapping with minimal reduction in the active sensing area. Consequently, stable and sensitive gas detection under humid conditions was achieved in this hybrid sensor. The superior humidity-independent sensing is ascribed to the preferential adsorption of water molecules on hydroscopic CS nanosheets through the hydrogen bond. Based on density functional theory calculations, we determined that the improved gas response is driven by the additional formation of oxygen vacancy in SnO₂ due to the diffusion of aliovalent Ca ions from the CS nanosheet.

Original implementation of low-temperature SPS for bioactive glass used as a bone biomaterial

Alkali borated bioactive glasses powders with compositions based on the SiO₂-Na₂O-CaO-P₂O₅-x B₂O₃ system (0 < x < 20 wt%); have been consolidated at low temperature using Spark Plasma Sintering (SPS). Through SPS technique under 50 MPa, it was possible to achieve fully dense and completely amorphous borated glasses at temperatures as low as 420 °C. By increasing the sintering temperature up to 430 °C, the dense samples crystallized which is mostly achieved at higher temperatures. This study reveals that the mechanical properties of these new borated biomaterials are suitable to be used as a promising candidate for repairing defects in non-load-bearing bones as well as for coating on the metallic surface implants to improve the bioactivity process bone/implant. The pressure had a weak effect on the crystallization and densification of the glass compared to the temperature during the powder consolidation by SPS. Moreover, by increasing the boron content, the compressive strength and the elastic modulus of the elaborated glasses decreased for being close to those of the natural.

In vitro comparisons of microscale and nanoscale calcium silicate particles

Calcium silicate (CaSi) materials have been used for bone repair and generation due to their osteogenic properties. Tailoring the surface chemistry and structure of CaSi can enhance its clinical performance. There is no direct comparison between microscale and nanoscale CaSi particles. Therefore, this article aimed to compare and evaluate the surface chemistry, structure, and in vitro properties of microscale CaSi (μCaSi) and nanoscale CaSi (nCaSi) particles synthesized by the sol-gel method and precipitation method, respectively. As a result, the semi-crystalline μCaSi powders were assemblies of irregular microparticles containing a major β-dicalcium silicate phase, while the amorphous nCaSi powders consisted of spherical particles with a size of 100 nm. After soaking in a Tris-HCl solution, the amount of Si ions released from nCaSi was higher than that released from μCaSi, but there was no significant difference in Ca ion release between the two CaSi particles. Compared to microscale CaSi (μCaSi), nanoscale CaSi (nCaSi) significantly enhanced the growth and differentiation of human mesenchymal stem cells (hMSC) and inhibited the function of RAW 264.7 macrophages. In the case of antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), nanoscale nCaSi displayed a higher bacteriostatic ratio, a greater growth inhibition zone and more reactive oxygen species (ROS) production than microscale μCaSi. The conclusion is that nanoscale CaSi had greater antibacterial and osteogenic activity compared to microscale CaSi. Next generation CaSi-based materials with unique properties are emerging to meet specific clinical needs.

Zirconia-containing wollastonite ceramics derived from biowaste resources for bone tissue engineering

Zirconia-containing wollastonite (CaSiO₃) ceramics with partial substitution of zirconia (1, 3 and 5 mol%) were prepared using eggshells and rice husk ash as source materials for calcium oxide and silica, respectively, through a sol-gel technique. The effect of incorporation of zirconia on in vitro bioactivity, mechanical properties, degradability and cytocompatibility of wollastonite was studied. Bioactivity was evaluated by in vitro assay using simulated body fluid while degradability was tested in Tris-HCl buffer solution for different time periods (1, 3, 7, 14 and 21 d) according to the ISO 10 993-14 standard. Human osteosarcoma (MG-63) cells were used to assess cytocompatibility with the MTT assay. X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy-energy dispersive spectroscopy were used to characterize the ceramics before and after in vitro studies. The results obtained showed that increasing the zirconia content in the wollastonite phase increases microhardness, compressive strength, bending strength and the elasticity modulus, while slightly decreasing the rate of formation of the hydroxyapatite layer. Moreover, the samples doped with zirconia had a lower degradation rate and it was noticed that cell viability is unaffected by the incorporation of zirconia.

Enhanced antibacterial activity of calcium silicate-based hybrid cements for bone repair

Calcium silicate cement has attracted much attention for bone defect repair and regeneration due to its osteogenic properties. Biomaterial-associated infections and washout have become a common clinical problem. In order to enhance the antibacterial and washout performance of calcium silicate cement to meet clinical needs, different types of chitosan, including chitosan polysaccharide (CTS), quaternary ammonium chitosan (QTS), and chitosan oligosaccharide (COS), as a liquid phase were added to the calcium silicate powder. The physicochemical properties, in vitro bioactivity, antibacterial efficacy, and osteogenic effects (MG63 cells) of the cement were evaluated. Antibacterial activity was conducted with Gram-negative Escherichia coli (E. coli) and a Gram-positive Staphylococcus aureus (S. aureus) bacteria. The amount of intracellular reactive oxygen species (ROS) produced in the bacteria cultured with the chitosan solution was also detected. The experimental results showed that the chitosan additive did not affect the crystalline phase of calcium silicate cement, but increased the setting time and strength of the cement in a concentration-dependent manner. Within the scope of this study, CTS and QTS solutions with a concentration of not <1 wt% improved the washout resistance of the control cement, while the COS solutions failed to strengthen the cement. When soaked in simulated body fluid (SBF) for 1 day, all cement samples formed apatite spherules. As the soaking time increased, the diametral tensile strength of all cements decreased and the porosity increased. The assays of MG63 cell function showed lower osteogenic activity of osteoblastic cells grown on the surfaces of the chitosan-incorporated cements in comparison with the control cement without chitosan. At the same 1% concentration, compared with QTS and COS cement, CTS cement had lower cell attachment, proliferation, differentiation, and mineralization. Conversely, the CTS cement resulted in the highest bacteriostasis ratio among the three hybrid cements against two bacteria. The ROS production followed the order of CTS > QTS > COS at the same 1% concentration. In conclusion, calcium silicate cement with 1% QTS may be a viable candidate for bone defect repair in view of anti-washout performance, setting time, antibacterial activity, and osteogenic activity shown in this study.

Effect of ion doping in silica-based nanoparticles on the hemolytic and oxidative activity in contact with human erythrocytes

AIM

The aim of this study was the synthesis of ion doped silica-based nanoparticles and the evaluation of their toxic effect on erythrocytes.

MATERIALS & METHODS

Their synthesis was performed using the sol-gel method, by the progressive addition of calcium, magnesium and copper ions on pure silica nanoparticles. The toxicity evaluation was based on hemolysis, lipid peroxidation, ROS, H₂O₂ species and antioxidant enzyme production.

RESULTS

The addition of Mg and Cu in the SNs presented better hemocompatibility by protecting erythrocytes from oxidative stress.

CONCLUSION

Ion doping with magnesium in the investigated calcium silicate system induces a protective effect in erythrocyte membrane in compare with pure silica nanoparticles.

Highly Dispersed Ni Nanoparticles on Anhydrous Calcium Silicate (ACS) Nanosheets for Catalytic Dry Reforming of Methane: Tuning the Activity by Different Ways of Ni Introduction

Three kinds of nickel-loaded anhydrous calcium silicate nanocatalysts (ACS), including Ni-ACS-Dop, Ni-ACS-Iex and Ni-ACS-Im, were prepared by introducing Ni species through doping in the synthesis of calcium silicate hydrate (CSH) nanosheets, ion-exchange with premade CSH nanosheets and deposition on calcined ACS nanosheets, respectively. Although Ni species were introduced in different ways, all the Ni-ACS catalysts showed similar chemical compositions and microstructures, where Ni nanoparticles were highly dispersed on the ultrathin ACS nanosheets with a large surface area and good thermal stability. However, the differences in the way of Ni introduction did produce Ni with different electronic states. The Ni-ACS-Iex catalyst with "surface Ni" as a dominant form had more electrons enriched on the surface of Ni, which led to the highest activity in the dry reforming of methane (DRM) reaction among the three catalysts, whereas the Ni-ACS-Dop catalyst with "lattice Ni" as a dominant form showed an electron-deficient property and lowest activity. Different from the introduction of a more favourable nanostructure or chemical component to the catalyst system, this work controlled the chemical environment of metal precursors and created metal catalysts with a preferred surface electronic state during synthesis, which could be a new strategy to improve the catalytic activity.

Simultaneous removal of nitrogen and phosphorus by magnesium-modified calcium silicate core-shell material in water

In this study, a new core-shell material (CMCS) is prepared with magnesium oxide (MgO) around calcium silicate hydrate (CSH), and CSH is prepared by SiO₂ from the red mud. The CMCS simultaneously removes ammonia nitrogen (NH₄⁺) and phosphate (PO₄^3-) by chemical precipitation and it can achieve recovery of nitrogen and phosphorus. The removal process of NH₄⁺ and PO₄^3- is as follows. First, the shell of MgO is used to remove NH₄⁺ and a part of the PO₄^3- by the assisted adsorption and struvite (MgNH₄PO₄·6H₂O) precipitation method. Then the CSH is used to remove the residual part of PO₄^3- by chemical precipitation (Ca₅(PO₄)₃OH, CaHPO₄ and Ca₃(PO₄)₂). Furthermore, the MgO shell of CMCS not only removes NH₄⁺ and PO₄^3-, but also can control the calcium ions (Ca²⁺) spill from CSH and pH in the process of removing NH₄⁺ and PO₄^3-. The removal rate of NH₄⁺ and PO₄^3- can reach 76.63% and 87.18%, respectively, in the solution in 80 min, but in the actual wastewater the removal rate of NH₄⁺ and PO₄^3- is 61.40% and 62.83%, respectively. Finally, CMCS was recycled five times and its removal rates of NH₄⁺ and PO₄^3- are 21.01% and 24.99%, respectively. The aim of this article is to present CMCS, which has a good effect on removing the NH₄⁺ and PO₄^3- simultaneously.

Facile synthesis of novel calcium silicate hydrated-nylon 6/66 nanocomposites by solution mixing method

In this article a facile and green procedure for the synthesis of novel calcium silicate hydrated-nylon 6/66 nanocomposites is proposed. Calcium silicate hydrate (CSH) was synthesized by a hydrolysis technique assisted by ultrasound and using sodium dodecyl sulphate (SDS) as surfactant. CSH-nylon 6/66 nanocomposites were obtained by a solution mixing method at CSH loadings of 2.5, 25, 50 and 75 weight percent (samples CA, CD, CB and CC, respectively). The synthesis of CSH was confirmed by DRX and ATR-FTIR techniques; the CSH sample presents as mesoporous with a diameter between 3.34 nm and 52.68 nm and an average size of 27.07 nm; the specific surface area of the CSH sample was 343.99 m² g⁻¹. The formation of the CSH-nylon 6/66 nanocomposites was confirmed by ATR-FTIR, SEM, XRD, TGA, DSC and XPS techniques. The crystallization and melting temperatures (T_m and T_c, respectively) of CSH-nylon 6/66 nanocomposites occur at a slightly lower temperatures than those of neat Ny 6/66. These results suggest a slight decrease of the crystallite size and crystallization rate of nylon 6/66. The fusion enthalpy (ΔH_f) decreases with increase in CSH content in nylon 6/66, which can be associated to a good dispersion. The XRD peaks of the nylon 6/66 at 19.99° and 23.77° were displaced at slightly higher values of 2θ with the incorporation of CSH in the polymer forming nanocomposite materials.

In this work it was possible to synthesize novel CSH-nylon 6/66 nanocomposites using a simple and easy methodology such as the solution mixing method and using green solvents like water, formic acid and ethanol.

Effect of phosphorus precursors on the structure of bioactive calcium phosphate silicate systems

The main aim of this work was to synthesize calcium phosphate silicate bioceramics by a low energy-consuming sol-gel method applying various phosphorous precursors (triethyl phosphate, phosphoric acid, and ammonium hydrogen phosphate). The investigations concentrated on the influence of phosphorous initial compounds on the bond and crystalline structures and the material quality. The application of the alkoxide and inorganic P-precursors results in considerably different textures. The inorganic PO₄-containing precursors lead to sol formations. The sol systems can be characterized by a randomly bonded aggregate structure. Monolith gel systems can only be prepared by using TEP. The alkoxide P-precursor more effectively furthers the connection between the phosphorous and silicon tetrahedra than the inorganic phosphate compounds. Over the P-precursors, the catalyst also affects the structure and properties. In the present work, a special attention was paid to identify the POSi bonds in the FTIR and ³¹P NMR spectra. The bond systems were investigated by FTIR, ³¹P and ²⁹Si MAS NMR spectroscopies, the morphology by SEM, WAXS, and XRD measurements, and the water solubility of the ceramic systems also was tested.

Regulating micro-structure and biomineralization of electrospun PVP-based hybridized carbon nanofibers containing bioglass nanoparticles via aging time

Morphological and micro-structural evolution of BG components in PVP-based CNF/BG composite with aging time.

Effect of tricalcium aluminate on the physicochemical properties, bioactivity, and biocompatibility of partially stabilized cements

Background/Purpose

Mineral Trioxide Aggregate (MTA) was widely used as a root-end filling material and for vital pulp therapy. A significant disadvantage to MTA is the prolonged setting time has limited the application in endodontic treatments. This study examined the physicochemical properties and biological performance of novel partially stabilized cements (PSCs) prepared to address some of the drawbacks of MTA, without causing any change in biological properties. PSC has a great potential as the vital pulp therapy material in dentistry.

Methods

This study examined three experimental groups consisting of samples that were fabricated using sol-gel processes in C3S/C3A molar ratios of 9/1, 7/3, and 5/5 (denoted as PSC-91, PSC-73, and PSC-55, respectively). The comparison group consisted of MTA samples. The setting times, pH variation, compressive strength, morphology, and phase composition of hydration products and ex vivo bioactivity were evaluated. Moreover, biocompatibility was assessed by using lactate dehydrogenase to determine the cytotoxicity and a cell proliferation (WST-1) assay kit to determine cell viability. Mineralization was evaluated using Alizarin Red S staining.

Results

Crystalline phases, which were determined using X-ray diffraction analysis, confirmed that the C3A contents of the material powder differed. The initial setting times of PSC-73 and PSC-55 ranged between 15 and 25 min; these values are significantly (p<0.05, ANOVA and post-hoc test) lower than those obtained for MTA (165 min) and PSC-91 (80.5 min). All of the PSCs exhibited ex vivo bioactivity when immersed in simulated body fluid. The biocompatibility results for all of the tested cements were as favorable as those of the negative control, except for PSC-55, which exhibited mild cytotoxicity.

Conclusion

PSC-91 is a favorable material for vital pulp therapy because it exhibits optimal compressive strength, a short setting time, and high biocompatibility and bioactivity.

Catalysis, nanostructure and macroscopic property triangle in bioactive calcium-containing ceramic systems

Calcium silicate ceramics are intended for application as long-term implant materials. In the present work, attention was paid to understand the correlations between the nanostructure (aggregate size, crystallinity, porosity) and the macroscopic properties (solubility in water and simulated body fluids, SBF; hardness) varying the chemical composition. Varying the catalyst (from a base to various acids) during the chemical synthesis was shown to significantly impact on the pore size, crystallinity and mechanical properties. The basic catalyst yields the ceramics with the highest mechanical strength. Ammonia used in 1.0 or 10.0 molar ratio results in bulk ceramics with parameters required for a biomedical application, good hardness (180-200 HV) and low solubility (1-3%) in water and in SBF. The fine porosity (~50 nm) and homogeneous amorphous structure induce good mechanical character.