Bone-like Apatite Research Articles

In-vitro bioactivity, biocompatibility and dissolution studies of diopside prepared from biowaste by using sol–gel combustion method

Diopside was synthesized from biowaste (Eggshell) by sol–gel combustion method at low calcination temperature and the influence of two different fuels (urea, l-alanine) on the phase formation temperature, physical and biological properties of the resultant diopside was studied. The synthesized materials were characterized by heating microscopy, FTIR, XRD, BET, SEM and EDAX techniques. BET analysis reveals particles were of submicron size with porosity in the nanometer range. Bone-like apatite deposition ability of diopside scaffolds was examined under static and circulation mode of SBF (Simulated Body Fluid). It was noticed that diopside has the capability to deposit HAP (hydroxyapatite) within the early stages of immersion. ICP-OES analysis indicates release of Ca, Mg, Si ions and removal of P ions from the SBF, but in different quantities from diopside scaffolds. Cytocompatability studies on human bone marrow stromal cells (hBMSCs) revealed good cellular attachment on the surface of diopside scaffolds and formation of extracellular matrix (ECM). This study suggests that the usage of eggshell biowaste as calcium source provides an effective substitute for synthetic starting materials to fabricate bioproducts for biomedical applications.

Involvement of 3D osteoblast migration and bone apatite during in vitro early osteocytogenesis

The transition from osteoblast to osteocyte is described to occur through passive entrapment mechanism (self-buried, or embedded by neighboring cells). Here, we provide evidence of a new pathway where osteoblasts are “more” active than generally assumed. We demonstrate that osteoblasts possess the ability to migrate and differentiate into early osteocytes inside dense collagen matrices. This step involves MMP-13 simultaneously with IBSP and DMP1 expression. We also show that osteoblast migration is enhanced by the presence of apatite bone mineral. To reach this conclusion, we used an in vitro hybrid model based on both the structural characteristics of the osteoid tissue (including its density, texture and three-dimensional order), and the use of bone-like apatite. This finding highlights the mutual dynamic influence of osteoblast cell and bone extra cellular matrix. Such interactivity extends the role of physicochemical effects in bone morphogenesis complementing the widely studied molecular signals. This result represents a conceptual advancement in the fundamental understanding of bone formation.

Fabrication of Bioactive Stainless Steel by the Function of Apatite Nuclei

Micropores were formed on the surfaces of stainless steel (SUS) by sandblasting methods and Apatite Nuclei (AN) were formed in the pores. By this treatments, a bioactive SUS was fabricated. Apatite-forming ability of the SUS was evaluated by immersing in an acellular simulated body fluid. Formation of bonelike apatite was induced on the surface of the SUS within 1 day. High bonding strength of the bonelike apatite layer was achieved by a mechanical interlocking effect between the bonelike apatite formed in the pores and the SUS specimen.

Enzyme Immobilization by Using Apatite Microcapsules with Magnetic Properties

Apatite Nucleus (AN) was attached on the surfaces of maghemite (γ-Fe2O3) particles and soaked them in SBF. By this treatment, formation of bonelike apatite was induced by AN and the apatite covered the whole surface of the γ-Fe2O3 particles. Urease was immobilized on the surfaces of microcapsules and collected by a neodymium magnet. The immobilized urease has an ability of a urea decomposition in an aqueous solution.

Novel Bioactive Materials Derived by Bioglass: Glass‐Ceramic A‐W and Surface‐Modified Ti Metal

It is shown in this study how bioactive glass‐ceramic A‐W with a high mechanical strength and bioactive surface‐modified Ti metal with a high fracture toughness was derived from Bioglass®. Glass‐ceramic A‐W precipitating apatite and wollastonite was obtained by crystallization of a glass of a modified composition of Bioglass®. The resultant product showed a higher mechanical strength than human cortical bone, as well as bone‐bonding ability. It was clinically used for various kinds of bone substitute such as artificial vertebrae and iliac crest. However, its fracture toughness is not so high as that of human cortical bone. By examining bone‐bonding mechanism of Bioglass® and glass‐ceramic A‐W, it was found that a material capable of forming bonelike apatite on its surface in the living body bonds to living bone through the apatite layer. The apatite formation on a material in the living body can be evaluated even in a simulated body fluid in vitro. On the basis of these findings, a Ti metal with high fracture toughness was conferred bone‐bonding ability by surface modification with simple chemical and heat treatments. The resultant products are in clinical use for an artificial hip joint and spinal fusion devices.

Optically Monitoring Mineralization and Demineralization on Photoluminescent Bioactive Nanofibers.

Bone regeneration and scaffold degradation do not usually follow the same rate, representing a daunting challenge in bone repair. Toward this end, we propose to use an external field such as light (in particular, a tissue-penetrating near-infrared light) to precisely monitor the degradation of the mineralized scaffold (demineralization) and the formation of apatite mineral (mineralization). Herein, CaTiO3:Yb(3+),Er(3+)@bioactive glass (CaTiO3:Yb(3+),Er(3+)@BG) nanofibers with upconversion (UC) photoluminescence (PL) were synthesized. Such nanofibers are biocompatible and can emit green and red light under 980 nm excitation. The UC PL intensity is quenched during the bone-like apatite formation on the surface of the nanofibers in simulated body fluid; more mineral formation on the nanofibers induces more rapid optical quenching of the UC PL. Furthermore, the quenched UC PL can recover back to its original magnitude when the apatite on the nanofibers is degraded. Our work suggests that it is possible to optically monitor the apatite mineralization and demineralization on the surface of nanofibers used in bone repair.

Bioactivity of fluorapatite/alumina composite coatings deposited on Ti6Al4V substrates by laser cladding

Hydroxyapatite (HA) is one of the most commonly used coating materials for metal implants. However, following high-temperature deposition, HA easily decomposes into an unstable phase or forms an amorphous phase, and hence, the long-term stability of the implant is reduced. Accordingly, the present study investigates the use of fluorapatite (FA) fortified with 20 wt% alumina (α-Al2O3) as an alternative biomedical coating material. The coatings are deposited on Ti6Al4V substrates using a Nd:YAG laser cladding process performed with laser powers and travel speeds of 400 W/200 mm/min, 800 W/400 mm/min and 1200 W/600 mm/min, respectively. The results show that for all of the specimens, a strong metallurgical bond is formed at the interface between the coating layer and the transition layer due to melting and diffusion. The XRD analysis results reveal that the cladding layers in all of the specimens consist mainly of FA, β-TCP, CaF2, Ti and θ-Al2O3 phases. In addition, the cladding layers of the specimens prepared using laser powers of 400 and 800 W also contain CaTiO3 and CaAl2O4, while that of the specimen clad using a power of 1200 W contains TTCP and CaO. Following immersion in simulated body fluid for 14 days, all of the specimens precipitate dense bone-like apatite and exhibit excellent bioactivity. However, among all of the specimens, the specimen that is prepared with a laser power of 800 W shows the best biological activity due to the presence of residual FA, apatite-generating CaTiO3 and a rough cladding layer surface.

Structure and in vitro bioactivity of ceramic coatings on magnesium alloys by microarc oxidation

Magnesium and its alloys have the potential to serve as lightweight, degradable, biocompatible and bioactive orthopedic implants for load-bearing applications. However, severe local corrosion attack and high corrosion rate have prevented their further clinical use. Micro-arc oxidation (MAO) is proved to be a simple, controllable and efficient electrochemistry technique that can prepare protective ceramic coatings on magnesium alloys. In this paper, electrolyte containing silicate salts was used for microarc oxidation to form ceramic bioactive coatings on the ZK61 alloy substrate. The structure characteristics and element distributions of the coating were investigated by XRD, TEM, SEM and EPMA. The MAO samples were immersed in simulated body fluid (SBF) for 7 and 14days, respectively. The surface characteristic of the immersed coatings was investigated by Fourier-transform infrared (FTIR) spectroscopy. The results show that these MAO coatings have low crystallinity and are mainly composed of MgO, Mg2SiO4 and Mg2Si2O6. The coating surface is porous. During the SBF immersion period, the nucleation and precipitation of bone-like apatites occur on the MAO coating surface. The corrosion resistance of the substrate is improved by the MAO coatings.

Divalent ion encapsulated nano titania on Ti metal as a bioactive surface with enhanced protein adsorption

A novel approach on incorporation of divalent species such as Mg, Ca and Sr into the titania nanostructures formed on Ti metal surface and their comparative study on enhancement of bioactivity, protein adsorption and cell compatibility is reported. When treated with hydrogen peroxide, Ti metal forms hydrogen titanate. On subsequent treatment with Mg or Ca or Sr nitrate solutions, respective ions are incorporated into hydrogen titanate layer, and heat treatment leads to titania decorated with these ions. The resultant heat-treated samples when soaked in simulated body fluid form bone-like apatite which indicates the present surface modification enhances the bioactivity. Further, enhanced protein adsorption in bovine serum albumin is an indication of suitability of these divalent species to form chelate compounds with amino acids, and Ca containing titania nanostructure favours more protein adsorption compared to the others. Cytocompatibility studies using MG-63, human osteosarcoma cell lines shows these divalent ion containing titania nanostructure favours the cell attachment and did not show any cytotoxicity. Bioactivity, enhanced protein adsorption along with cytocompatibility clearly indicates such surface modification approach to be useful to design hard tissue replacement materials in orthopaedic and dental field.

Synthesis of monodispersed mesoporous bioactive glass nanospheres for bone repair

Mesoporous bioactive glass nanospheres (SiO2-CaO-P2O5, MBG) with remarkable mono-dispersity were successfully synthesized using Pluronic P123 and cetyltrimethylammonium bromide (CTAB) mixed surfactants under neutral condition. The characterizations revealed that MBG NPs had uniform spherical morphology with a homogeneous diameter around 100nm and mesopores sized at 3.7nm. The synthesized nanospheres also have excellent bone-like apatite formation ability and much faster degradation rate compared to pure silica nanoparticles. In addition, MBG NPs showed drug storage/release property demonstrated for dexamethasone drug.

In-Vitro Biocompatibility Studies of Plasma-Nitrided Titanium Alloy β-21S Using Fibroblast Cells

In the present work, titanium alloy β-21S was nitrided in a low-pressure RF plasma with 100% nitrogen and 20% hydrogen-diluted nitrogen at 800 °C for 4 h and the samples were evaluated for in-vitro biocompatibility by using NIH 3T3 fibroblast cell line. Cellular behavior was evaluated in terms of cell morphology and its viability. FESEM was exploited to observe the morphology of the cells fixed over the surface of the implant. Fibroblasts were seemed to be well distributed over the surface with its characteristic spindle-like shape. Over all, the results indicate that nitriding provided a compatible surface for cell attachment and cell growth. Cell viability and proliferation was assessed by using standard MTT assay. Compared with substrate, the nitrided samples exhibited high-percentage cell viability demonstrating their increased biocompatibility. In addition, the nitrided samples facilitate bone-like apatite formation and exhibited a gradual increase of apatite formation after immersion in Hanks’ solution.

Preparation and characterization of wollastonite/titanium oxide nanofiber bioceramic composite as a future implant material

In this study, novel composites consisting of electrospun titanium dioxide (TiO2) nanofibers incorporated into high-purity wollastonite glass ceramics were prepared as materials for use in hard tissue engineering applications. These materials were characterized and investigated by means of physical, mechanical and in vitro studies. The proposed composite showed greater densification and better mechanical characteristics compared to pure wollastonite. The influence of densification temperature and TiO2 content was investigated. Typically, TiO2/wollastonite composites having 0, 10, 20 and 30wt% metal oxide nanofibers were sintered at 900, 1100 and 1250°C. The results indicated that increasing TiO2 nanofibers content leads to increase the bulk density, compressive strength and microhardness with negligible, high and moderate influence for the densification temperature, respectively. While porosity and water adsorption capacity decreased with increasing the metal oxide nanofibers with a considerable impact for the sintering temperature in both properties. Moreover, bone-like apatite formed on the surface of wollastonite and wollastonite/TiO2 nanofibers soaked in simulated body fluid (SBF). All these results show that the inclusion of TiO2 nanofibers improved the characteristics of wollastonite while preserving its in vitro bioactivity; hence, the proposed composite may be used as a bone substitute in high load bearing sites.

GEP-based method to formulate adhesion strength and hardness of Nb PVD coated on Ti–6Al–7Nb aimed at developing mixed oxide nanotubular arrays

PVD process as a thin film coating method is highly applicable for both metallic and ceramic materials, which is faced with the necessity of choosing the correct parameters to achieve optimal results. In the present study, a GEP-based model for the first time was proposed as a safe and accurate method to predict the adhesion strength and hardness of the Nb PVD coated aimed at growing the mixed oxide nanotubular arrays on Ti67. Here, the training and testing analysis were executed for both adhesion strength and hardness. The optimum parameter combination for the scratch adhesion strength and micro hardness was determined by the maximum mean S/N ratio, which was 350W, 20 sccm, and a DC bias of 90V. Results showed that the values calculated in the training and testing in GEP model were very close to the actual experiments designed by Taguchi. The as-sputtered Nb coating with highest adhesion strength and microhardness was electrochemically anodized at 20V for 4h. From the FESEM images and EDS results of the annealed sample, a thick layer of bone-like apatite was formed on the sample surface after soaking in SBF for 10 days, which can be connected to the development of a highly ordered nanotube arrays. This novel approach provides an outline for the future design of nanostructured coatings for a wide range of applications.

Optimization and Characterization of Anatase Formed on Anodized Titanium in Phosphoric Acid

Titanium (Ti) is widely used in dental and orthopedic implants because of its good biocombatibility and high corrosion resistance. Titanium oxide (TiO2) has shown to exhibit strong physicochemical bonding between Ti implant and living bone because of its ability to induce bone-like apatite in a body environment. Ti is always coated by an oxide surface layer of 1.5-10 nm thickness. TiO2 crystalline structures; anatase and rutile present several distinctive features, such as photocatalytic behaviour, superhydrophilicity and biocompatible properties. Anodic oxidation is used to modify the surface of pure titanium in a phosphuric acid electrolyte in order to maximize and characterize the TiO2 anatase crystalline phase. In the present work, thick films of the anatase polymorph of TiO2 were formed on commercially pure Ti foil under potentials 200 V-350 V at current densities 40 and 60 mA/cm2 for 10 min. Multiple characterization techniques were used. Glancing angle X-ray diffraction (GAXRD) is used to obtain crystalline phases, field emission scanning electron microscope (FESEM) is used to obtain surface images and water contact angle (WCA) is used to obtain the wettability of the oxide surface. According to GAXRD results the intensity of the major peak increased with increasing applied voltage and current density while decrease with molar concentration. This means that the amount and/or crystallinity of anatase are/is influenced with these parameters. The coated oxides obtained small amount of anatase is comparing to films anodized in H2SO4 electrolyte. Which confirm that slower crystallization in H3PO4 than in H2SO4. FESEM images obtained that as the voltage increased, the film breaks down locally and results in a porous surface. The porosity and the pore size increase with the increasing voltage. The pore size diameter at 300V for 0.3 M can reach up to 1μm. As for WCA results the coated samples at higher voltages (250 V, 300 V and 350 V) and molar concentration 0.3 M have shown more hydrophilic surface, with sample anodized at 350 V at 0.3 M have the lowest contact angle, thus the highest surface energy. While samples anodized at 200 V voltage observed more hydrophobic surface with sample anodized at 200 V at 0.1 M have the lower wettability, thus the lowest surface energy.

Adhesive Bioactive Coatings Inspired by Sea Life

Inspired by nature, in particular by the marine mussels adhesive proteins (MAPs) and by the tough brick-and-mortar nacre-like structure, novel multilayered films are prepared in the present work. Organic-inorganic multilayered films, with an architecture similar to nacre based on bioactive glass nanoparticles (BG), chitosan, and hyaluronic acid modified with catechol groups, which are the main components responsible for the outstanding adhesion in MAPs, are developed for the first time. The biomimetic conjugate is prepared by carbodiimide chemistry and analyzed by ultraviolet-visible spectrophotometry. The buildup of the multilayered films is monitored with a quartz crystal microbalance with dissipation monitoring, and their topography is characterized by atomic force microscopy. The mechanical properties reveal that the films containing catechol groups and BG present an enhanced adhesion. Moreover, the bioactivity of the films upon immersion in a simulated body fluid solution is evaluated by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. It was found that the constructed films promote the formation of bonelike apatite in vitro. Such multifunctional mussel inspired LbL films, which combine enhanced adhesion and bioactivity, could be potentially used as coatings of a variety of implants for orthopedic applications.

Explore the interface of bone-like apatite formation on the porous hydroxyapatite scaffolds

Explore the interface of bone-like apatite formation on the porous hydroxyapatite scaffolds

Surface functionalization of porous Titanium scaffold for bone tissue engineering

Event Abstract Back to Event Surface functionalization of porous Titanium scaffold for bone tissue engineering Bingjun Zhang1, Zhiwei Han1 and Jie Weng1 1 Southwest Jiaotong University, Key Laboratory of Advanced Technologies of Materials,School of Materials Science and Engineering, China Introduction: Bone tissue engineering materials has been rapidly developed in recent years as an alternative to autografts and allografts. Considerable efforts have been carried out to enhance the properties of tissue engineering architectures via surface engineering and surface functionalization for providing an extracellular matrix mimicking environment for better cell adhesion and tissue in-growth[1]. In this work, in view of excellent function of polydopamine (PDA)[2]-[4] and favourable biocompatibility and mechanical properties of Titanium (Ti), we seek to design a functional bone graft substitute based Ti in a biocompatible, cell-friendly scaffold mimicking the bone morphology would greatly enhance bone regeneration engineering. Materials and Methods: In this study, the Ti powder was used for preparing highly interconnected porous scaffolds by porogen–leaching methods, of which adopting sugar spheres (400-600μm) as pore-forming agent. Subsequently, we introduced a mussel-inspired, biomimetic technique based on a PDA ad-layer developed from oxidative polymerization of dopamine to surface modification of tissue engineering scaffolds and substrates. In virtue of the characteristic of PDA coatings, adhesion peptides (GRGDS) were simply immobilized on the titanium surfaces for efficient and reliable manipulation of bone marrow mesenchymal stem cells (BMSCs) differentiation and proliferation. The surface properties, mechanical properties, and cell adhesion and proliferation properties of the functionalized porous Ti metal scaffold were investigated systematically. Results and Discussion: In the current study, porous Ti metal scaffold had a highly open porous structure (pores size: 500μm; through holes size: 100μm, approximately) and good mechanical strength (26.33MPa). With the use of the biomimetic mineralization method, the nano-net structure calcium phosphate was formed on the surface of sintered scaffolds after immersed in SBF for 7d, indicating that the porous Ti scaffold possessed positive biological compatibility. The nano-net bone-like apatite was very similar to composition of human bone mineral, which be able to shorten the time of bone fusion and improve the biocompatibility and biological activity of Ti scaffolds. When the PDA-coating technique was applied to three-dimensional Ti scaffold, PDA coatings facilitated highly efficient, simple immobilization of GRGDS onto Ti substrates. As confirmed by quantitative alamar blue assay and alkaline phosphatase assay, after 3 days of cultubation, the effect of promoting cell proliferation had been presented on the treated Ti scaffold. It was observed that the number of BMSCs was higher than pure Ti scaffold. And statistical analysis showed that PDA–GRGDS modified Ti scaffold had significant difference compared with untreated Ti, which indicated that PDA-GRGDS introduced on the surface of implanted materials intrinsically facilitated cell adhesion and proliferation. The ALP activity of BMSCs, by 14 days, cultured on treated Ti, was significantly higher than that of pure Ti (p < 0.05).That means the early cell adhesion had play a crucial role in promoting osteogenetic activity of cells. In summary, the GRGDS conjugation greatly enhanced not only the adhesion but also mineralization of osteoblasts or BMSCs compared with untreated scaffolds, while calcium phosphate mineralized layers deposition facilitated cellular osteodifferentiation. Therefore, this kind of biocompatible scaffolds provided an optimal microenvironment for cell proliferation, migration, and differentiation, and guidance for cellular in-growth from host tissue. Conclusions: This functionalized layer formed by PDA-mediated surface modification on porous titanium scaffold promoted BMSCs adhesion and improved osteogenic differentiation and mineralization. In conclusion, this kind of bioactive Ti scaffold with such mechanical strength as that of woven bone should be a promising bone graft in clinical applications. This research was supported by grants from National Basic Research Program of China (973 Program, 2012CB933600), National Natural Science Foundation of China (51172188) and Science & Technology Pillar Project of Sichuan (2010FZ0048)

Formation of hierarchical bone-like apatites on silk microfiber templates via biomineralization

Hierarchical bone-like apatites can be formed on silk microfiber templates and the resulting biocomposites achieved good cytocompatibility.

Mesoscopically ordered bone mimetic nanocomposites

Event Abstract Back to Event Mesoscopically ordered bone mimetic nanocomposites Martin Andersson1, Wenxiao He1 and Anand K. Rajasekharan1 1 Chalmers University of Technology, Chemistry and Chemical Engineering, Sweden Introduction: Bone provides protection and support for the movements of our body through its excellent load-bearing properties. Though the macrostructure differs depending on bone type, the nanostructure of natural bone universally comprises collagen fibrils possessing periodic gaps, within which elongated bone apatite nanoparticles are aligned and embedded. To synthetically reproduce the complexity of bone has been proven challenging, and the fact that simple mixing of proteins, such as collagen 1, with precipitated apatite crystals does not form materials having mechanical properties even close to that of bone, clearly demonstrates that the hierarchical arrangement of the structure is of outmost importance. Figure 1(A) Formation and nanostructure of bone and our biomimetic composite. (B) SAXS scattering confirms presence of order and anisotropy in composite. (C) TEM image shows alignment of HA nanocrystals with the material. Methods: Herein we demonstrate a novel, synthetic approach, highly inspired by the architecture of natural bone, to design mechanically stable nanocomposites incorporating aligned apatite nanocrystals. To mimic the nanostructure of natural bone, we first combine molecular self-assembly and intermolecular crosslinking to create resilient polymeric matrices with long-range periodicity; then we employ compartmentalized mineral growth via a transient amorphous phase for the biomimetic formation of bone-like apatite, see Fig. 1. Results and Discussion: Small angle X-ray scattering (SAXS) data of the nanocomposite confirmed the presence of meso-ordered (hexagonal) structure with long-range anisotropy of the nanocomposite similar to bone (Figure 1B)[1]. Moreover electron microscopy images of grounded composites show alignment of the HA nanoparticles due to the orientation from the PLC matrix (Figure 1C)[1]. The nanoscale confinements within the polymeric matrices controled the phase purity of calcium phosphates. When CaP is precipitated in confinements of sizes 11-27 nm, multiple phases including acidic polymorphs coexisted. Contrastingly, confinements smaller than 10 nm produced phase pure ACPs, which on aging converted to nanocrystalline apatite[2]. A general hypothesis is proposed that in absence of chemical control, confinements might need to be smaller than naturally occurring ones to control the mineral phase purity in both synthetic and biological systems. The results also provide an insight into designing biomaterials with an ordered structure and high mineral content while maintaining chemical homogeneity. Mechanically, the composite showed compressive strength of 3-4 MPa, which is comparable to cancellous bone, an important result for further developing the implant. Current work focuses on developing the composite with a 3-D hierarchical structure and a porous network for functioning as a scaffold. Conclusion: Molecular self-assembly of synthetic polymers can be used to form mesoscopically ordered polymer-apatite nanocomposites having similar apatite chemistry and a highly ordered nanostructure inspired from bone. We acknowledge the Swedish Research Council, Nano-Sphere Centre/Formas and the Wallenberg Foundation through their Wallenberg Academy Fellow Program for financial support. We also thank MAX-lab (Lund, Sweden) for the allocation of beam time and assistance with SAXS measurements

Tailoring properties of porous Poly (vinylidene fluoride) scaffold through nano-sized 58s bioactive glass

The biological properties of porous poly (vinylidene fluoride) (PVDF) scaffolds fabricated by selective laser sintering were tailored through nano-sized 58s bioactive glass. The results showed that 58s bioactive glass distributed evenly in the PVDF matrix. There were some exposed particles on the surface which provided attachment sites for biological response. It was confirmed that the scaffolds had highly bioactivity by the formation of bone-like apatite in simulated body fluid. And the bone-like apatite became dense with the increase in 58s bioactive glass and culture time. Moreover, the scaffolds were suitable for cell adhesion and proliferation compared with the PVDF scaffolds without 58s bioactive glass. The research showed that the PVDF/58s bioactive glass scaffolds had latent application in bone tissue engineering.