RESUMO
OBJECTIVES: Silicon-releasing biomaterials are widely used in the field of dentistry. However, unlike bone, very little is known about the role of silicon on dental tissue formation and repair. This study investigates the influence of silicic acid on the survival, differentiation and mineralizing ability of human dental pulp stem cells (hDPSCs) in 3D pulp-like environments METHODS: Dense type I collagen hydrogels seeded with hDPSCs were cultured over 4 weeks in the presence of silicic acid at physiological (10 µM) and supraphysiological (100 µM) concentrations. Cell viability and proliferation were studied by Alamar Blue and live/dead staining. The collagen network was investigated using second harmonic generation imaging. Mineral deposition was monitored by histology and scanning electron microscopy. Gene expression of mineralization- and matrix remodeling-associated proteins was studied by qPCR. RESULTS: Presence of silicic acid did not show any significant influence on cell survival, metabolic activity and gene expression of key mineralization-related proteins (ALP, OCN, BSP). However, it induced enhanced cell clustering and delayed expression of matrix remodeling-associated proteins (MMP13, Col I). OPN expression and mineral deposition were inhibited at 100 µM. It could be inferred that silicic acid has no direct cellular effect but rather interacts with the collagen network, leading to a modification of the cell-matrix interface. SIGNIFICANCE: Our results offer advanced insights on the possible role of silicic acid, as released by pulp capping calcium silicates biomaterials, in reparative dentine formation. More globally, these results interrogate the possible role of Si in pulp pathophysiology.
Assuntos
Diferenciação Celular , Proliferação de Células , Sobrevivência Celular , Polpa Dentária , Ácido Silícico , Células-Tronco , Humanos , Polpa Dentária/citologia , Células-Tronco/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ácido Silícico/farmacologia , Ácido Silícico/química , Células Cultivadas , Hidrogéis/química , Microscopia Eletrônica de Varredura , Silício/química , Colágeno , Calcificação Fisiológica/efeitos dos fármacos , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Colágeno Tipo I/metabolismo , Reação em Cadeia da Polimerase em Tempo RealRESUMO
Plants undergo substantial biomineralization of silicon, which is deposited primarily in cell walls as amorphous silica. The mineral formation could be moderated by the structure and chemistry of lignin, a polyphenol polymer that is a major constituent of the secondary cell wall. However, the reactions between lignin and silica have not yet been well elucidated. Here, we investigate silica deposition onto a lignin model compound. Polyphenyl propanoid was synthesized from coniferyl alcohol by oxidative coupling with peroxidase in the presence of acidic tetramethyl orthosilicate, a silicic acid precursor. Raman, Fourier transform infrared, and X-ray photoelectron spectroscopies detected changes in lignin formation in the presence of silicic acid. Bonds between the Si-O/Si-OH residues and phenoxyl radicals and lignin functional groups formed during the first 3 h of the reaction, while silica continued to form over 3 days. Thermal gravimetric analysis indicated that lignin yields increased in the presence of silicic acid, possibly via the stabilization of phenolic radicals. This, in turn, resulted in shorter stretches of the lignin polymer. Silica deposition initiated within a lignin matrix via the formation of covalent Si-O-C bonds. The silica nucleants grew into 2-5 nm particles, as observed via scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. Additional silica precipitated into an extended gel. Collectively, our results demonstrate a reciprocal relation by which lignin polymerization catalyzes the formation of silica, and at the same time silicic acid enhances lignin polymerization and yield.
Assuntos
Lignina , Dióxido de Silício , Lignina/química , Dióxido de Silício/química , Biomineralização , Ácido Silícico/química , Silício/químicaRESUMO
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.
Assuntos
Ácido Silícico , Dióxido de Silício , Dióxido de Silício/química , Ácido Silícico/química , Polímeros/química , Amidas , AminasRESUMO
Silica is extensively deposited by plants, however, only little is known about the molecular control over this process. Siliplant1 is the only known plant protein to precipitate biosilica. The protein contains seven repeats made of three domains. One of the domains exhibits a conserved sequence, which catalyzes silica precipitation in vitro. Here, silica was synthesized by the activity of a peptide carrying this conserved sequence. Infrared spectroscopy and thermal gravimetric analyses showed that the peptide was bound to the mineral. Scanning electron microscopy showed that silica-peptide particles of 22 ± 4 nm aggregated to spherical structures of 200-300 nm when the ratio of silicic acid to the peptide was below 183:1 molecules. When the ratio was about 183:1, similar particles aggregated into irregular structures, and silica gel formed at higher ratios. Solid-state NMR spectra indicated that the irregular aggregates were richer in Si-O-Si bonds as well as disordered peptide. Our results suggest that the peptide catalyzed the condensation of silicic acid and the formation of â¼20 nm particles, which aggregated into spheres. Excess of the peptide stabilized surface Si-OH groups that prevented spontaneous Si-O-Si bonding between aggregates. Under Si concentrations relevant to plant sap, the peptide and possibly Siliplant1, could catalyze nucleation of silica particles that aggregate into spherical aggregates.
Assuntos
Ácido Silícico , Dióxido de Silício , Dióxido de Silício/química , Ácido Silícico/química , Peptídeos/química , Proteínas , Espectrofotometria InfravermelhoRESUMO
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.
Assuntos
Ácido Silícico , Dióxido de Silício , Dióxido de Silício/metabolismo , Ácido Silícico/química , Ácido Silícico/metabolismo , Silício/metabolismo , Plantas/metabolismo , PolímerosRESUMO
Diatoms are an important group of algae that can produce intricate silicified cell walls (frustules). The complex process of silicification involves a set of enigmatic integral membrane proteins that are thought to actively transport the soluble precursor of biosilica, dissolved silicic acid. Full-length silicic acid transporters are found widely across the diatoms while homologous shorter proteins have now been identified in a range of other organisms. It has been suggested that modern silicic acid transporters arose from the union of such partial sequences. Here, we present a computational study of the silicic acid transporters and related transporter-like sequences to help understand the structure, function and evolution of this class of membrane protein. The AlphaFold software predicts that all of the protein sequences studied here share a common fold in the membrane domain which is entirely different from the predicted folds of non-homologous silicic acid transporters from plants. Substrate docking reveals how conserved polar residues could interact with silicic acid at a central solvent-accessible binding site, consistent with an alternating access mechanism of transport. The structural conservation between these proteins supports a model where modern silicon transporters evolved from smaller ancestral proteins by gene fusion.
Assuntos
Diatomáceas , Ácido Silícico , Ácido Silícico/química , Ácido Silícico/metabolismo , Diatomáceas/genética , Diatomáceas/química , Diatomáceas/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Membrana Transportadoras/metabolismo , Silício/química , Proteínas de Membrana/metabolismo , Simulação por ComputadorRESUMO
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.
Assuntos
Aquaporinas/química , Proteínas de Arabidopsis/química , Oryza/metabolismo , Raízes de Plantas/metabolismo , Ácido Silícico/metabolismo , Silício/metabolismo , Sequência de Aminoácidos , Aquaporinas/genética , Aquaporinas/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sítios de Ligação , Transporte Biológico , Cristalografia por Raios X , Difusão , Expressão Gênica , Cinética , Modelos Moleculares , Simulação de Dinâmica Molecular , Oryza/genética , Raízes de Plantas/genética , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Ácido Silícico/química , Silício/química , Especificidade por SubstratoRESUMO
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.
Assuntos
Dendrímeros/química , Poliaminas/química , Ácido Silícico/química , Adsorção , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Simulação de Dinâmica Molecular , Dióxido de Silício/química , TemperaturaRESUMO
Silicon (Si) has numerous health properties. It is an element of the extracellular matrix; it is involved in collagen synthesis, bone mineralization, and immune system modulation; and it reduces metal accumulation in Alzheimer's disease and the risk of atherosclerosis. Given its poor intestinal absorption, Si is ingested in the form of orthosilicic acid (OSA) to promote its bioavailability. The aim of this work was to compare different commercial dietary supplements containing stabilized OSA to ascertain their bioaccessibility, bioavailability, and safety in a model of human intestinal epithelium. Biocompatibility with the glycocalyx was also investigated. Supplements containing collagen, maltodextrins, and choline as OSA stabilizers were analyzed. Bioaccessibility was explored by means of an in vitro digestive process. Bioavailability was investigated using a Caco2 cell line alone, or co-culturing with a HT29-MTX cell line. The safety of the compounds tested (in terms of intestinal epithelium integrity) was judged on the grounds of MTS assay, transepithelial electrical resistance, and apparent permeability. The three formulations were also tested in a Caco2 cell model of intestinal glycocalyx Si retention. The choline-formulated OSA formulation outperformed the maltodextrin-stabilized supplement, with a Si bioavailability about 14 times higher (P < .05). The choline-formulated OSA formulation increased cell permeability, with consequent intestinal epithelium disruption. The supplements' absorption and bioavailability (and harmfulness) differed considerably, depending on the OSA stabilizer involved. Of the three formulations tested, the collagen-formulated OSA represents the best Si dietary supplement.
Assuntos
Ácido Silícico/farmacocinética , Silício/farmacocinética , Disponibilidade Biológica , Células CACO-2 , Sobrevivência Celular/efeitos dos fármacos , Colágeno/química , Suplementos Nutricionais , Composição de Medicamentos , Glicocálix/metabolismo , Humanos , Absorção Intestinal , Mucosa Intestinal/efeitos dos fármacos , Ácido Silícico/química , Ácido Silícico/farmacologia , Silício/químicaRESUMO
The unmodified R5 peptide from silaffin in the diatom Cylindrotheca fusiformis rapidly precipitates silica particles from neutral aqueous solutions of orthosilicic acid. A range of post-translational modifications found in R5 contribute toward tailoring silica morphologies in a species-specific manner. We investigated the specific effect of R5 lysine side-chain trimethylation, which adds permanent positive charges, on silica particle formation. Our studies revealed that a doubly trimethylated R5K3,4me3 peptide has reduced maximum activity yet, surprisingly, generates larger silica particles. Molecular dynamics simulations of R5K3,4me3 binding by the precursor orthosilicate anion revealed that orthosilicate preferentially associates with unmodified lysine side-chain amines and the peptide N terminus. Thus, larger silica particles arise from reduced orthosilicate association with trimethylated lysine side chains and their redirection to the N terminus of the R5 peptide.
Assuntos
Fragmentos de Peptídeos/química , Precursores de Proteínas/química , Ácido Silícico/química , Dióxido de Silício/química , Sítios de Ligação , Diatomáceas/química , Metilação , Simulação de Dinâmica Molecular , Tamanho da PartículaRESUMO
Mesoporous silica has attracted significant attention in the drug delivery area; however, impurities can be a source of toxicity. The current study used commercial microparticles produced at large scale in a well-controlled environment. Micrometer sized mesoporous silica particles were acquired through a commercial vendor and pore structures were characterized by SEM. The three silica particle formulations had a diameter of 15 micrometers and three different pore sizes of 10 nm, 30 nm, and 100 nm. The fourth formulation had particle size of 20-40 micrometers with 50 nm pores. Before in vivo tests, an in vitro cytotoxicity test was conducted with silicic acid, derived from the sol-gel particles, on EA.hy926 cells. Low concentration (2.5 µg/mL) of silicic acid showed no cytotoxicity; however, high concentration (25 µg/mL) was cytotoxic. In vivo intravitreal injection demonstrated that 15 um silica particles with 10 nm pore were safe in both rabbit and guinea pig eyes and the particles lasted in the vitreous for longer than two months. Formulations of with larger pores demonstrated variable localized vitreous cloudiness around the sol-gel particle depot and mild inflammatory cells in the aqueous humor. The incidence of reaction trended higher with larger pores (10 nm: 0%, 30 nm: 29%, 50 nm: 71%, 100 nm: 100%, p < .0001, Cochran Armitage Trend Test). Sol-gel mesoporous silica particles have uniform particle sizes and well-defined pores, which is an advantage for implantation via a fine needle. Selected formulations may be used as an intraocular drug delivery system with proper loading and encapsulation.
Assuntos
Portadores de Fármacos , Células Endoteliais/efeitos dos fármacos , Olho/efeitos dos fármacos , Sílica Gel , Animais , Técnicas de Cultura de Células , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Portadores de Fármacos/química , Portadores de Fármacos/toxicidade , Liberação Controlada de Fármacos , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Olho/metabolismo , Olho/patologia , Cobaias , Humanos , Técnicas In Vitro , Injeções Intravítreas , Tamanho da Partícula , Porosidade , Coelhos , Sílica Gel/química , Sílica Gel/toxicidade , Ácido Silícico/química , Ácido Silícico/toxicidade , Propriedades de SuperfícieRESUMO
Bone injury, especially bone damages due to the removal of bone tumors, is one of the most important issues in the field of therapeutic research in tissue engineering applications. In this context, ceramic-based composites have attracted widespread attention since they have mechanical properties close to the natural bone, hence providing similar conditions for the extracellular matrix (ECM). Thus, in this study, hardystonite and diopside (HT-Di) scaffolds containing various diopside amounts from 5 to 25 wt% were prepared by the space holder method. The results revealed that the fabricated scaffolds contain 70%-75% porosity with a pore size of 300-500 µm and a compressive strength of about 0.54 to 1.71 MPa which is perfectly in the range of the compressive strength of the sponge bone. Noticeably, great apatite formation ability was observed in the scaffold with diopside, although the scaffold without diopside showed poor bioactivity. The MTT assay depicted that the inclusion of diopside into hardystonite scaffold resulted in dramatic enhancement in the MG-63 cell viability. Moreover, the scaffold with diopside offered greater cell attachment and spreading than the scaffold without diopside. Therefore, the synergistic effects of the scaffold with 12.5 wt% of diopside, including great mechanical characteristic, excellent bioactivity, and appealing biocompatibility enable it to be an appealing choice for bone tissue engineering applications.
Assuntos
Materiais Biocompatíveis , Nanocompostos/química , Silicatos/química , Ácido Silícico/química , Engenharia Tecidual/instrumentação , Engenharia Tecidual/métodos , Substitutos Ósseos , Osso e Ossos/patologia , Linhagem Celular Tumoral , Cerâmica , Força Compressiva , Durapatita/farmacologia , Matriz Extracelular/efeitos dos fármacos , Humanos , Concentração de Íons de Hidrogênio , Teste de Materiais , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Transição de Fase , Porosidade , Pós , Pressão , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Alicerces Teciduais/química , Difração de Raios XRESUMO
This paper concerns simultaneous removal of fluoride and hydrated silica from groundwater (4.08 mg L-1 fluoride, 90 mg L-1 hydrated silica, 50 mg L-1 sulfate, 0.23 mg L-1 phosphate, pH 7.38 and 450 µS cm-1 conductivity) by electrocoagulation (EC), using an up-flow EC reactor, with a six-cell stack in a serpentine array, opened at the top of the cell to favor gas release. Aluminum plates were used as sacrificial electrodes. The effect of current density (4 ≤ j ≤ 7 mA cm-2) and mean linear flow rate (1.2 ≤ u ≤ 4.8 cm s-1), applied to the EC reactor, on the elimination of fluoride and hydrated silica was analyzed. The removal of fluoride followed the WHO guideline (<1.5 mg L-1), while the hydrated silica was abated at 7 mA cm-2 and 1.2 cm s-1, with energy consumption of 2.48 kWh m-3 and an overall operational cost of 0.441 USD m-3. Spectroscopic analyses of the flocs by XRD, XRF-EDS, SEM-EDS, and FTIR indicated that hydrated silica reacted with the coagulant forming aluminosilicates, and fluoride replaced a hydroxide from aluminum aggregates, while sulfates and phosphates were removed by adsorption process onto the flocs. The well-engineered EC reactor allowed the simultaneous removal of fluoride and hydrated silica.
Assuntos
Fluoretos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Alumínio/química , Eletrocoagulação/métodos , Eletrodos , Água Subterrânea/química , Concentração de Íons de Hidrogênio , Ácido Silícico/química , SulfatosRESUMO
Ti scaffolds combined with autologous human adipose-derived mesenchymal stem cells (hASCs) have been successfully applied for regenerative cranio-maxillofacial bone therapies. Future challenges reside in regeneration of larger bone defects and displacement of the permanent Ti structure, thus, advanced resorbable scaffolds are needed. Composites of ß-Ca3 (PO4 )2 with 80 and 60 wt % of CaMg(SiO3 )2 with improved mechanical properties compared to tricalcium phosphate (TCP) materials are presented. Synthetic CaMg(SiO3 )2 and a precursor of Ca3 (PO4 )2 were used to fabricate the composites and a reference ß-Ca3 (PO4 )2 material by uniaxial pressing and solid state sintering. Optimum sintering temperature of 1225°C was selected. Microstructural analysis and Weibull distributions of tensile strengths determined by the diametral compression of discs test are reported. Thermodynamic simulation of the dissolution process in simulated body fluid body fluid was done. The biological response with hASCs was analyzed using basic and osteogenic media. Viability and osteogenic potential-LIVE/DEAD assay; alkaline phosphatase activity and collagen type-I production-were characterized. The composites have higher tensile strength (>3×) than TCP materials, for similar reliability, and support viability and osteogenic differentiation of hASCs. Resorption of the high strength phase diopside is the slowest. The promising results reported here suggest possible uses of these bioactive ß-Ca3 (PO4 )2 -CaMg(SiO3 )2 ceramics together with hASCs in bone tissue engineering.
Assuntos
Adipócitos/citologia , Fosfatos de Cálcio/química , Osteogênese , Ácido Silícico/química , Células-Tronco/citologia , Fosfatase Alcalina/metabolismo , Osso e Ossos/patologia , Diferenciação Celular , Sobrevivência Celular , Humanos , Cinética , Microscopia Eletrônica de Varredura , Microscopia de Fluorescência , Pressão , Reprodutibilidade dos Testes , Estresse Mecânico , Temperatura , Resistência à Tração , Termodinâmica , Engenharia Tecidual/métodos , Difração de Raios XRESUMO
One of the significant challenges in bone tissue engineering is the fabrication of highly porous scaffolds with interconnected pores and appropriate mechanical properties. Artificial scaffolds which used in the field of medicine are usually made of single phase of polymer or ceramic. However, composition of these materials can produce the scaffolds with improve mechanical and biological properties.The aim of this study is to synthesize three-dimensional hardystonite-diopside (HT-Dio) porous scaffolds modified by polycaporolacton fumarate coating for low-load-bearing bone tissue engineering applications. The results showed that hardystonite scaffolds with 15â¯wt. % diopside and 6 w/v % polymer polycaporolacton fumarate (PCLF) had a significant bioactivity. The cell culture and cell attachment assay results revealed the well spreading of BMS cells on the surface of modified scaffolds which indicates the high biocompatibility of this scaffold. The modified scaffolds had a mean pore size, porosity, compressive strength, modules and toughness of 293.47⯱â¯5.51⯵m, 74%⯱â¯1.01, 3.37⯱â¯0.6â¯MPa, 151⯱â¯1.1â¯MPa and 31.3⯱â¯0.32â¯kJ/m3, respectively, which are in the appropriate range for spongy bone and hence can be a good candidate for bone tissue engineering applications.
Assuntos
Materiais Revestidos Biocompatíveis/química , Fenômenos Mecânicos , Nanocompostos/química , Poliésteres/química , Silicatos/química , Ácido Silícico/química , Alicerces Teciduais/química , Adesão Celular/efeitos dos fármacos , Linhagem Celular , Materiais Revestidos Biocompatíveis/farmacologia , Humanos , Porosidade , Engenharia TecidualRESUMO
In this study, a simple and facile strategy was developed for the synthesis of novel hydroxyapatite (HA)/nanostructured monticellite ceramic composites by mechanical method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) were used to peruse the phase structure, and morphology of soaked ceramic composites in simulated body fluid (SBF). The in vitro bioactivity of HA-based ceramic composites with nanostructured monticellite ranging from 0 to 50â¯wt% was evaluated via investigating the formation ability of bone-like calcium phosphates in SBF and the effect of obtained extracts from composites dissolution on osteoblast-like G-292 cell line. Moreover, In vitro cytocompatibility of the HA/monticellite ceramic composites was investigated by MTT, cell growth & adhesion and alkaline phosphatase (ALP) activity assays, and quantitative real-time PCR analysis. The results showed that HA/nanostructured monticellite ceramic composites could induce apatite formation in SBF. The cell proliferation and growth exposed to ceramic composites extracts were significantly stimulated and promoted at a certain concentration range compared to control for various time periods of cell culture. The optimized composite extract enhanced considerably gene expression of G-292 type X collagen (COLX) at different days. Also, G-292 cells were spread and adhered well on the ceramic composite disc. Furthermore, ALP activity of G-292 cells exposed to ceramic composites extracts was dramatically enhanced in comparison with pure HA extract (as control) at different concentrations for various time periods of cell culture. The results suggest that the optimized HA/nanostructured monticellite composite is promising biomaterial for clinical applications such as orthopedic and dentistry.
Assuntos
Materiais Biocompatíveis/síntese química , Tecnologia Biomédica/métodos , Durapatita/síntese química , Nanoestruturas/química , Ácido Silícico/síntese química , Fosfatase Alcalina/metabolismo , Animais , Materiais Biocompatíveis/química , Adesão Celular , Linhagem Celular , Proliferação de Células , Cerâmica/química , Colágeno Tipo X/metabolismo , Corrosão , Durapatita/química , Humanos , Osteoblastos/citologia , Osteogênese , Tamanho da Partícula , Ácido Silícico/química , Difração de Raios XRESUMO
This study focuses on the effect of Sr-, F-, and their co-doping on the structure, biodegradation, bioactivity and cytocompatibility of diopside-based scaffolds, using X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, Archimedes densitometry, inductively coupled plasma spectroscopy, pH-metry, and cell MTT assay. The structural characterization of the scaffolds confirmed the successful incorporation of the dopants into the ceramic. In addition, all the doped scaffolds presented higher apatite-forming ability levels in comparison to the undoped one, where the highest and the least impact of doping on bioactivity belonged to F- and co-doping, respectively. It was found that the biodegradation difference of the scaffolds in terms of principal ions and the chance of F-incorporation into precipitated apatite determine the bioactivity difference of the samples. Osteoblast-like MG-63 cells exhibited the highest and lowest compatibility to the Sr-doped and co-doped scaffolds, respectively. In summary, F- and Sr-doping offered the highest bioactivity and cytocompatibility, respectively, whereas co-doping presented the weakest behaviors comparatively.
Assuntos
Flúor/química , Ácido Silícico/química , Ácido Silícico/farmacologia , Estrôncio/química , Alicerces Teciduais , Apatitas/química , Neoplasias Ósseas/patologia , Substitutos Ósseos , Linhagem Celular Tumoral , Humanos , Concentração de Íons de Hidrogênio , Teste de Materiais , Microscopia Eletrônica de Varredura , Osteossarcoma/patologia , Análise Espectral Raman , Difração de Raios XRESUMO
Crystallite aluminosilicates are inorganic microporous materials with well-defined pore-size and pore-structures, and have important industrial applications, including gas adsorption and separation, catalysis, etc. Crystallite aluminosilicates are commonly synthesized via hydrothermal processes, where the oligomerization of silicic acids is crucial. The mechanisms for the oligomerization of poly-silicic acids in neutral aqueous solution were systematically investigated by extensive first-principles-based calculations. We showed that oligomerization of poly-silicic acid molecules proceeds through the lateral attacking and simultaneously proton transfer from the approaching molecule for the formation of a 5-coordinated Si species as the transition state, resulting in the ejection of a water molecule from the formed poly-silicic acid. The barriers for this mechanism are in general more plausible than the conventional direct attacking of poly-silicic acid with reaction barriers in the range of 150-160 kJ/mol. The formation of linear or branched poly-silicic acids by intermolecular oligomerization is only slightly more plausible than the formation of cyclic poly-silicic acids via intramolecular oligomerization according to the reaction barriers (124.2-133.0 vs. 130.6-144.9 kJ/mol). The potential contributions of oligomer structures, such as the length of the linear oligomers, ring distortions and neighboring linear branches, etc., to the oligomerization were also investigated but found negligible. According to the small differences among the reaction barriers, we proposed that kinetic selectivity of the poly-silicic acids condensation would be weak in neutral aqueous solution and the formation of zeolite-like structures would be thermodynamics driven.
Assuntos
Ácido Silícico/química , Água/química , Zeolitas/química , Silicatos de Alumínio/química , Dimerização , Cinética , Modelos Moleculares , Soluções , TermodinâmicaAssuntos
Autofagia/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Proteínas de Ligação a RNA/efeitos dos fármacos , Proteína Sequestossoma-1/efeitos dos fármacos , Ácido Silícico/química , Adenina/análogos & derivados , Adenina/química , Fosfatase Alcalina/metabolismo , Animais , Antígenos Glicosídicos Associados a Tumores/metabolismo , Densidade Óssea/efeitos dos fármacos , Calcificação Fisiológica/efeitos dos fármacos , Linhagem Celular , Colágeno/química , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Feminino , Glicoproteínas/metabolismo , Humanos , Camundongos , Proteínas Associadas aos Microtúbulos/metabolismo , Modelos Animais , Osteoblastos/citologia , Osteogênese , Proteínas de Ligação a RNA/genética , Ratos Wistar , Proteína Sequestossoma-1/genéticaRESUMO
In this research, novel monticellite/hydroxyapatite (HA) ceramic composites were successfully prepared by mechanical method. The ability of nanostructured monticellite-based ceramic composites to form a suitable bond to living hard tissues, and stimulate osteoblast-like cells proliferation may be different for various ratios of the reinforcement to monticellite matrix. The differences in physico-chemical characteristics, bone-like apatite formation, cytocompatibility, cell viability and in vitro osteogenic activity of nanostructured monticellite/HA ceramic composites were explored. The surface reactivity and bioactivity of the composite samples were evaluated in vitro in simulated body fluid (SBF). A comparative time- and dose-dependent MTT test showed that the ions release from nanostructured monticellite/HA composites dissolution significantly stimulated cell proliferation and growth than control at a certain concentration range. The cells viability exposed to the composite extract was higher than control and mineral material of bone (HA), illustrating that cytocompatibility was improved due to the presence of magnesium (Mg) and silicon (Si) elements in the composite structure. The comparative results of alkaline phosphatase (ALP) bioactivity assay showed that the osteogenic proliferation of osteoblast-like G292 cell was increased more by the ceramic composites extract than control. These comparative results demonstrated that nanostructured monticellite-based ceramic composites possessed good in vitro bioactivity, cytocompatibility and osteogenic properties, and may be utilized as the promising bioactive materials for bone tissue regeneration and replacement.