Excellent Apatite-forming Ability Research Articles

Preparation and In Vitro Bioactivity Study of a Novel Hollow Mesoporous Bioactive Glass Nanofiber Scaffold.

In this study, a novel three-dimensional hollow mesoporous bioactive glass nanofiber scaffold has been synthesized with a template-assisted sol-gel method using bacterial cellulose (BC) as a template and nonionic triblock copolymer (P123) as a pore-directing agent, ethyl orthosilicate (TEOS), calcium nitrate tetrahydrate (CN), and triethyl phosphate (TEP) as glass precursors. Scanning and transmission electron microscopies, X-ray diffraction, nitrogen adsorption-desorption, and nuclear magnetic resonance method were applied to characterize the morphology, crystal structure, and chemical structure of the mesoporous bioactive glass nanofiber scaffold. Furthermore, the in vitro bioactivity and biocompatibility were also explored. The obtained scaffold depicted nanofiber-like morphology and interconnected three-dimensional network structure that replicated the BC template. The scaffold showed a large specific surface area (230.0 cm2 g-1) and pore volume (0.2 m3 g-1). More importantly, the scaffold exhibited excellent apatite-forming ability and cellular biocompatibility. We believe that the hollow mesoporous bioactive glass nanofiber scaffold has great potential application in bone tissue regeneration.

Fabrication and in vitro evaluation of Ca11B2Si4O22 ceramic for bone tissue engineering

• For the first time, a novel Ca 11 B 2 Si 4 O 22 powder was prepared by a sol-gel method. • In vitro experimental results indicated that the Ca 11 B 2 Si 4 O 22 ceramic enhanced osteogenic differentiation of mBMSCs. • Ca 11 B 2 Si 4 O 22 ceramics had good mechanical property. Calcium borosilicates are bioactive materials. This work synthesized a novel Ca 11 B 2 Si 4 O 22 powder by a sol-gel method. Besides, Ca 11 B 2 Si 4 O 22 ceramic was prepared via the dry-pressure molding and high temperature sintering. XRD analysis results revealed that the high-purity Ca 11 B 2 Si 4 O 22 crystalline powder was successfully prepared. Meanwhile, the compressive strength of the Ca 11 B 2 Si 4 O 22 ceramic reached to 290 MPa. More interestingly, the Ca 11 B 2 Si 4 O 22 ceramic exhibited excellent apatite-forming ability in simulated body fluid and osteogenic activity in vitro . These results indicated that the novel Ca 11 B 2 Si 4 O 22 ceramic holds great potential for load-bearing bone repair.

Effect of nitrogen on the structure evolution and biological properties of mesoporous bioactive glass nanospheres: Experiments and simulations

Mesoporous bioactive glasses (MBGs) have displayed great potential in dental restorations and bone regeneration for their controllable structure and great bioactivity. In this work, we have systematically investigated the effect of nitrogen on structure evolution, apatite-forming ability and cytotoxicity in MBG by successfully preparing the N-containing MBG nanospheres by a modified sol-gel method. It is interesting to demonstrate that all obtained samples exhibit uniform interstitial mesoporous nanospheres microstructure, with the particles size increases as the nitrogen addition increases from 5 to 15 mol.%. Notably, a large amount of blooming flower-like hydroxyapatite deposited on the surface of 15N-MBG after immersed in simulated body fluid for 7 days, exhibiting excellent apatite-forming ability. It is highlighted that the incorporation of nitrogen can stimulate cell proliferation at early incubation time. Moreover, all the MBGs have no obvious inhibitory impact on the hPDLCs growth at extracted concentration. Furthermore, via glass network connectivity analysis from molecular dynamics simulations, the decrease of network connectivity caused by the incorporation of nitrogen could provide looser glass network and higher bioactivity, which explains the experimental results well.

Comparison Between Bioactive Sol-Gel and Melt-Derived Glasses/Glass-Ceramics Based on the Multicomponent SiO2-P2O5-CaO-MgO-Na2O-K2O System.

Bioactive sol-gel glasses are attractive biomaterials from both technological and functional viewpoints as they require lower processing temperatures compared to their melt-derived counterparts and exhibit a high specific surface area due to inherent nanoporosity. However, most of these materials are based on relatively simple binary or ternary oxide systems since the synthesis of multicomponent glasses via sol-gel still is a challenge. This work reports for the first time the production and characterization of sol-gel materials based on a six-oxide basic system (SiO2–P2O5–CaO–MgO–Na2O–K2O). It was shown that calcination played a role in inducing the formation of crystalline phases, thus generating glass-ceramic materials. The thermal, microstructural and textural properties, as well as the in vitro bioactivity, of these sol-gel materials were assessed and compared to those of the melt-derived counterpart glass with the same nominal composition. In spite of their glass-ceramic nature, these materials retained an excellent apatite-forming ability, which is key in bone repair applications.

Surface modification of TiNb alloy through hydrothermal treatment and its in vitro bioactivity

Surface modification of biomedical titanium and its alloys was considered as an effective method to improve their bioactivity and accelerate the integration between implanted materials and the human tissue. For this purpose, we described the fabrication of TiO2 thin film on the surface of TiNb, one kind of titanium alloy with good biocompatibility, by a facile hydrothermal treatment in H2O2 solution in this study. Field-emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), x-ray photoelectron scanning (XPS), Energy dispersive x-ray spectroscopy (EDS) and water contact angle measurement were used to characterize the morphology, crystal phase, chemical compositions and surface character of the samples. The results show that irregular micro-sized island-like structure, assembled by many nanocrystals with a size of 20 ∼ 40 nm, was formed on the surface of TiNb alloy after hydrothermal treatment. Moreover, the crystal phase of the as-fabricated film was determined as Nb-doping anatase TiO2. Meanwhile, in vitro bioactivity of the micro/nano-textured TiNb-based TiO2 film was evaluated by simulated body fluid (SBF) immersion test. The result demonstrated that TiNb alloy after surface modification exhibited excellent apatite-forming ability. After immersion in SBF for 18 days, a dense spherical hydroxyapatite layer was formed on the surface of TiNb alloy. Its outstanding bioactivity could be attributed to the good super-hydrophilicity, micro/nano microstructure and abundant hydroxyl group of the TiO2 film obtained by hydrothermal treatment of TiNb alloy.

Bioactive glass nanotube scaffold with well-ordered mesoporous structure for improved bioactivity and controlled drug delivery

In this study, a novel mesoporous bioactive glass nanotube (MBGN) scaffold has been fabricated via template-assisted sol-gel method using bacterial cellulose (BC) as template and nonionic block copolymer (P123) as pore-directing agent. The scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption analysis. Furthermore, simvastatin was used to evaluate the loading efficiency and release kinetics of the scaffold. The obtained scaffold displays nanofiber-like morphology, ordered mesopores on the tube walls, and interconnected three-dimensional (3D) network structure that completely replicates the BC template. In addition, it shows dual pore sizes (16.2 and 3.3 nm), large specific surface area (537.2 m2 g−1) and pore volume (1.429 cm3 g−1). More importantly, the scaffold possesses excellent apatite-forming ability and sustainable drug release as compared to the counterpart scaffold without mesopores. This unique scaffold can be considered a promising candidate for drug delivery and bone tissue regeneration.

Suspension Plasma-Sprayed Fluoridated Hydroxyapatite/Calcium Silicate Composite Coatings for Biomedical Applications

A novel fluoridated hydroxyapatite/calcium silicate (FHA/CS) composite coating deposited via suspension plasma spraying has been designed to improve the bonding strength between coating and substrate and to provide a suitable dissolution rate for faster initial bone fixation. Composite coatings with different ratios of FHA to CS were fabricated on Ti substrates by changing the composition of the suspension. The thicknesses of the composite coatings ranged from 75 to 92 μm with porosity of 7.4-8.3%. When the ratio of FHA to CS is 3:7, the composite coating shows the highest bonding strength and dissolution rate. The in vitro bioactivity of the coatings was characterized by evaluating their apatite-forming ability after immersion in simulated body fluid (SBF). The results show that the composite coatings possess strong reactivity after immersion in SBF. The antibacterial behavior of the coatings was also examined by observing the number of viable bacteria after incubation with the composite coatings; the data show that the proliferation of Staphylococcus aureus can be inhibited. Given the combination of high bonding strength, good chemical resistance, excellent apatite-forming ability and antibacterial activity, the FHA/CS composite coating should be a very promising coating material for implants.

The fabrication of nanostructured titania polymorphs layer with high crystallinity and its apatite-forming ability

High crystallinity anatase/rutile layers are prepared on the surface of commercially pure titanium (cpTi) by hydrothermal method at 160 °C for 3 h. The surface morphology of titania layers is changed by adjusting the pH value and Ti4+concentration of treating solution (TS). Obtained nanorods on all TS samples are composed of pure rutile and the anatase co-deposited with rutile is found in the dense bottom layer. The possible co-deposition mechanism of polymorphs layers is given in this study. In this study, the rutile nanorods array with high energy (101) facet exposed is found on the TS3 sample. In vitro apatite forming ability of the TS samples are confirmed by soaking them in Kokubo's simulated body fluid (SBF, pH 7.4, 36.5 °C) for 1 and 3 days. Results show that apatite particles could be obtained on all TS samples within 1 d. After 3 days' immersion in SBF, TS3 sample shows strongest apatite X-ray diffraction. These results indicate that the ability in inducing apatite on cpTi with TS3 treatment is excellent. Such excellent apatite-forming ability is ascribed to the existence of thick titania layer with high energy (101) facet exposed on the TS3 sample.

Fe-doped bioactive glass-derived scaffolds produced by sol-gel foaming

Multifunctional scaffolds were prepared by foaming Fe-containing sols according to a composition-optimized approach. These foams exhibited high specific surface area (16–80 m2/g) and hierarchical porosity from the macro- (50–600 µm) to the meso-scale (4–20 nm). The effects of iron content on the textural properties and in vitro bioactivity were investigated. It was observed that the increase of iron content involved a decrease of specific surface and mesopore size. Interestingly, an excellent apatite-forming ability was observed regardless of the material composition. The potential osteoconductivity of these bioactive foams, coupled with their ferrimagnetic properties, open new perspectives as regards the hyperthermia-assisted treatment and regeneration of osseous defects caused by bone cancer.

Ultra-fast microwave-assisted synthesis of diopside nanopowder for biomedical applications

Diopside (CaMgSi2O6) has recently attracted considerable attention in several fields due to its wide range of applications. In this research, pure diopside nanopowder was fabricated by microwave irradiation technique. Synthesis of diopside nanopowder through microwave irradiation technique has several significant advantages when compared to the other techniques; these include ultra-short synthesis time (a few minutes), cost-effective, high purity of the synthetized powder, and low required calcination temperature. The formation of pure crystalline diopside nanopowder was confirmed by X-ray diffraction (XRD)rgy dispersive X-ray spectrometer (EDS) and transmission electron microscopy (TEM) analyses. The synthesized powder was found to be agglomerated and composed of nanocrystalline particles with a mean particle size of ~ 70 nm. In vitro bioactivity evaluation of the synthesized diopside nanopowder reflected its excellent apatite-forming ability in SBF. In addition, cell viability results showed no cytotoxicity and improved cell proliferation. Moreover, cell morphology study indicated that MG63 cells were well attached and spread on the surface of diopside sample. Furthermore, Alkaline phosphatase (ALP) activity experiments indicated that the synthesized diopside nanopowders could facilitate the cells to proliferate and differentiate. The superior biological properties of the synthesized diopside nanopowder make it a suitable candidate for applications in biomedical applications. Therefore, microwave-assisted synthesis technique could be considered as a novel, safe and high efficient method for the production of bioactive diopside nanopowder.

Ultra-fast, highly efficient and green synthesis of bioactive forsterite nanopowder via microwave irradiation

Forsterite (Mg2SiO4) has recently attracted considerable attention in different fields because of its wide range of applications. In this paper, pure forsterite nanopowders were synthesized by an ultra-fast, highly efficient and green method for the first time. Microwave irradiation was used to synthesize forsterite nanopowder. The formation of highly crystalline forsterite nanopowder was confirmed by X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDS) analyses. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses showed that the agglomerated powder composed of nanocrystalline particles with the mean particle size of ~100 nm. Microwave irradiation significantly accelerated the rate of the reactions and dramatically decreased reaction times from hours to minutes and seconds. In vitro bioactivity evaluation was performed by soaking the forsterite samples in simulated body fluid (SBF). Results indicated that synthesized forsterite nanopowder via microwave irradiation method possessed excellent apatite-forming ability in SBF. Cell viability results showed that synthesized forsterite nanopowder not only showed no cytotoxicity but also improved cell proliferation. Alkaline phosphatase (ALP) activity assay indicated that the fabricated forsterite nanopowder could facilitate the MG63 osteoblast-like cells to proliferate and differentiate. Therefore, microwave-assisted synthesis technique could be considered as a novel, safe and high efficient method in saving time and energy for bioactive forsterite nanopowder production.

Monodispersed Bioactive Glass Nanoclusters with Ultralarge Pores and Intrinsic Exceptionally High miRNA Loading for Efficiently Enhancing Bone Regeneration.

Bioactive glass nanoparticles (BGNs) have attracted much attention in drug delivery and bone tissue regeneration, due to the advantages including biodegradation, high bone-bonding bioactivity, and facile large-scale fabrication. However, the wide biomedical applications of BGNs such as efficient gene delivery are limited due to their poor pore structure and easy aggregation. Herein, for the first time, this study reports novel monodispersed bioactive glass nanoclusters (BGNCs) with ultralarge mesopores (10-30 nm) and excellent miRNA delivery for accelerating critical-sized bone regeneration. BGNCs with different size (100-500 nm) are fabricated by using a branched polyethylenimine as the structure director and catalyst. BGNCs show an excellent apatite-forming ability and high biocompatibility. Importantly, BGNCs demonstrate an almost 19 times higher miRNA loading than those of conventional BGNs. Additionally, BGNCs-miRNA nanocomplexes exhibit a significantly high antienzymolysis, enhance cellular uptake and miRNA transfection efficiency, overpassing BGNs and commercial Lipofectamine 3000. BGNCs-mediated miRNA delivery significantly improves the osteogenic differentiation of bone marrow stromal stem cells in vitro and efficiently enhances bone formation in vivo. BGNCs can be a highly efficient nonviral vector for various gene therapy applications. The study may provide a novel strategy to develop highly gene-activated bioactive nanomaterials for simultaneous tissue regeneration and disease therapy.

Novel bioactive Fe-based metallic glasses with excellent apatite-forming ability

We demonstrate, for the first time, that the (Fe0.75B0.15Si0.1)100−xNbx (x=0, 1 and 3at.%) metallic glasses without toxic and allergic elements exhibit excellent apatite-forming ability in simulated body fluids (SBF), which is expected to be a new generation of biomaterials in stents and orthopedic implants. For the alloys without any surface treatment, spherical particles corresponding to octacalcium phosphate are spontaneously nucleated and precipitated throughout the alloy surface after immersion only for 1day, indicating that the present alloys possess an unusual high bioactivity. During the subsequent in-vitro immersion for 3days, SEM image reveals the typical ‘cauliflower’ morphology of bone-like hydroxyapatite (HA) with Ca/P ratio of 1.65. In addition, it is surprising to find that the in-vitro SBF immersion not only leads to the formation and growth of the apatite layer but also causes the progressive development of the underlying alloy substrate. Moreover, for the alloys immersed for 3 or 9days, the substrate alloy just beneath the apatite layer consists of a hierarchical nano/macro-porous structure through selective dissolution of the active components Fe and B in the surface. XPS analysis indicates that the apatite nucleation on the present alloys in SBF is attributed to the specific dissolution properties of the present alloys and the fast formation of Si-OH and Fe–OH or Nb-OH functional groups, followed by combination of these groups with Ca2+ and phosphate ions.

Synthesis, Characterization, In Vitro Bioactivity and Biocompatibility Evaluation of Hydroxyapatite/Bredigite (Ca7MgSi4O16) Composite Nanoparticles

Silicate-based bioceramics have been found to possess excellent apatite-forming ability, and they can stimulate cell proliferation and osteogenic differentiation. In this study, bredigite (Ca7MgSi4O16) nanoparticles were synthesized and incorporated into a hydroxyapatite (HA)-based matrix to produce composite nanoparticles with improved bioactivity and biocompatibility. HA/bredigite nanoparticles containing 25% and 50% bredigite were synthesized by using the sol–gel method. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and Fourier transform infrared techniques were used to study the phase structure, morphology, and structural properties of prepared nanoparticles. Results indicated that HA/bredigite nanoparticles with an average particle size of less than 50 nm and homogeneous distribution of bredigite were successfully synthesized. Obtained results also revealed that the presence of bredigite led to a small increase in HA lattice parameters and to a decrease in the agglomeration of composite nanoparticles. The in vitro bioactivity studies performed in the simulated body fluid showed that composite nanoparticles had higher apatite-forming ability than pure HA. The results of a cell proliferation assay revealed that the proliferation of mesenchymal stem cells in the extract of HA/bredigite was significantly higher than those in the extract of the initial HA and control group after 72 h. As the properties of HA/bredigite nanoparticles were highly improved, compared with pure HA, it is concluded that these composite nanoparticles could potentially be good candidates for use as effective bioactive materials in bone regeneration applications.

Synergistic Effect of Carbon Nanotubes and Graphene on Diopside Scaffolds.

A synergetic effect between carbon nanotubes (CNTs) and graphene on diopside (Di) scaffolds was demonstrated. 3D network architecture in the matrix was formed through the 1D CNTs inlaid among the 2D graphene platelets (GNPs). The mechanical properties of the CNTs/GNPs/Di scaffolds were significantly improved compared with the CNTs/Di scaffolds and GNPs/Di scaffolds. In addition, the scaffolds exhibited excellent apatite-forming ability, a modest degradation rate, and stable mechanical properties in simulated body fluid (SBF). Moreover, cell culturing tests indicated that the scaffolds supported the cells attachment and proliferation. Taken together, the CNTs/GNPs/Di scaffolds offered great potential for bone tissue engineering.

Structure, corrosion resistance and in vitro bioactivity of Ca and P containing TiO2 coating fabricated on NiTi alloy by plasma electrolytic oxidation

The Ca and P containing TiO2 coating was fabricated on NiTi alloy by PEO treatment in an organic electrolyte containing TiO2 collosol and Ca-Gp. The surfaces of the coating exhibit a typical PEO porous and rough structure. The XPS analysis indicates that the coatings are mainly composed of Ti, O, C, Ca, P and a little amount of Ni. The concentration of Ni is greatly reduced compared to that of the NiTi substrate. The XRD analysis indicates that the Ca and P elements existing in the PEO coating are mainly in the form of Ca2P4O12. The curves of potentiodynamic porlarization suggest that the corrosion resistance of the NiTi alloy is significantly improved by the TiO2 coating formed on its surface by PEO treatment. The thickness, bonding strength and the corrosion resistance of the PEO coating are obviously affected by adding of Ca-Gp in the electrolyte. The bioactivity of PEO coating is significantly improved due to the incorporation of Ca and P composition, and so exhibits an excellent apatite-forming ability in SBF solution.

In vitro and in vivo evaluation of a nanoparticulate bioceramic paste for dental pulp repair

Bioactive materials play an important role in facilitating dental pulp repair when living dental pulp is exposed after injuries. Mineral trioxide aggregate is the currently recommended material of choice for pulp repair procedures though has several disadvantages, especially the inconvenience of handling. Little information is yet available about the early events and molecular mechanisms involved in bioceramic-mediated dental pulp repair. We aimed to characterize and determine the apatite-forming ability of the novel ready-to-use nanoparticulate bioceramic iRoot BP Plus, and investigate its effects on the in vitro recruitment of human dental pulp stem cells (DPSCs), as well as its capacity to induce dentin bridge formation in an in vivo model of pulp repair. It was found that iRoot BP Plus was nanosized and had excellent apatite-forming ability in vitro. Treatment with iRoot BP Plus extracts promoted the adhesion, migration and attachment of DPSCs, and optimized focal adhesion formation (Vinculin, p-Paxillin and p-Focal adhesion kinase) and stress fibre assembly. Consistent with the in vitro results, we observed the formation of a homogeneous dentin bridge and the expression of odontogenic (dentin sialoprotein, dentin matrix protein 1) and focal adhesion molecules (Vinculin, p-Paxillin) at the injury site of pulp repair model by iRoot BP Plus. Our findings provide valuable insights into the mechanism of bioceramic-mediated dental pulp repair, and the novel revolutionary ready-to-use nanoparticulate bioceramic paste shows promising therapeutic potential in dental pulp repair application.

Synthesis of anodic titania nanotubes in Na2SO4/NaF electrolyte: A comparison between anodization time and specimens with biomaterial based approaches

Surface modification of commercially pure titanium (cp-Ti) has been carried out by electrochemical anodic oxidation at constant voltage for different time periods (0.5, 1, 2 and 4.5h). Currents developed during the anodization indicate that the nanotubes are formed due to the competition of titania formation and dissolution under the assistance of electric field. Topologies of the anodized titanium change remarkably with time of oxidation. The morphology of the as-prepared nanotubes was characterized by scanning electron microscopy and atomic force microscopy while the chemistry and crystallinity were characterized by energy-dispersive X-ray spectroscopy and X-ray diffraction respectively. The as-anodized oxide was of amorphous but transformed to anatase and/or rutile crystal structure upon annealing for 3h at 600°C. The anatase structure showed excellent apatite-forming ability and produced a compact apatite layer covering the surface completely upon treatment in simulated body fluid (SBF) solution for 30h. Corrosion of anodized titanium samples was studied in a SBF solution using open circuit potential, polarization and electrochemical impedance measurements and compared with that of non-oxidized titanium. Among these samples, titanium anodized for 4.5h exhibited superior corrosion properties.

Biomineralization on chemically synthesized collagen containing immobilized poly-γ-glutamic acid

Chemically synthesized collagen with a triple helix structure similar to that of natural collagen is attractive as a safe biomaterial. Hybrids of chemically synthesized collagen and apatite are proposed for novel bone substitutes. However their apatite-forming ability in simulated body fluid is still quite low. We examined acceleration of apatite formation on collagen by immobilized poly-γ-glutamic acid (PGA), which has excellent apatite-forming ability. Apatite was formed within 3 days when collagen was treated with PGA solutions containing an appropriate amount of CaCl2. A mixture of apatite and calcite was formed at high CaCl2 concentration. The present results indicate the possibility of preparing hybrid materials, with tailored mechanical and biological properties, based on chemically synthesized collagen.

Fabrication of Composites from Apatite and Chemically Synthesized Collagen

Chemically synthesized collagen with triple helix structure similar to natural collagen has been developed as a safe biomaterial. If the chemically synthesized collagen is deposited with apatite, they are expected for novel bone substitutes having bioactivity and bioresorbability. Although apatite formation on the chemically synthesized collagen has been examined, highly supersaturated condition such as 1.5SBF with ion concentration 1.5 times those of simulated body fluid (SBF) is needed to achieve apatite formation. In the present study, we intended acceleration on the apatite formation on the chemically synthesized collagen by immobilization with polyglutamic acid (PGA). PGA is known as biodegradable and biocompatible polypeptide having excellent apatite-forming ability. We examined effects of the immobilization procedure on mineralization behavior in SBF. At first, PGA was immobilized on porous sponges of chemically synthesized collagen in aqueous solutions containing PGA and CaCl2. As a result, not only apatite but also calcite-type CaCO3 was deposited on the specimens in SBF. The calcite formation was occurred during the treatment with PGA solution. pH of the solution was adjusted to 7 by NaOH solution in order to avoid dissolution of the collagen. During this procedure, Ca (OH)2 would be precipitated by locally increase in pH of the solution and converted into the calcite. When the PGA solution treatment was shortened so as to prevent the calcite formation, single phase of the apatite was formed in SBF. The present results indicate that crystalline phase deposited on the chemically synthesized collagen can be controlled by fabrication procedure, and provide fundamental design of composites containing apatite and chemically synthesized collagen useful for bone regeneration.