Apatite-forming Ability In Simulated Body Fluid Research Articles

Copper-doped Ordered Mesoporous Bioactive Glass: A Promising Multifunctional Platform for Bone Tissue Engineering †.

The design and development of biomaterials with multifunctional properties is highly attractive in the context of bone tissue engineering due to the potential of providing multiple therapies and, thus, better treatment of diseases. In order to tackle this challenge, copper-doped silicate mesoporous bioactive glasses (MBGs) were synthesized via a sol-gel route coupled with an evaporation-induced self-assembly process by using a non-ionic block co-polymer as a structure directing agent. The structure and textural properties of calcined materials were investigated by X-ray powder diffraction, scanning-transmission electron microscopy and nitrogen adsorption-desorption measurements. In vitro bioactivity was assessed by immersion tests in simulated body fluid (SBF). Preliminary antibacterial tests using Staphylococcus aureus were also carried out. Copper-doped glasses revealed an ordered arrangement of mesopores (diameter around 5 nm) and exhibited apatite-forming ability in SBF along with promising antibacterial properties. These results suggest the potential suitability of copper-doped MBG powder for use as a multifunctional biomaterial to promote bone regeneration (bioactivity) and prevent/combat microbial infection at the implantation site, thereby promoting tissue healing.

In vitro apatite mineralization and heat generation of magnetite-reduced graphene oxide nanocomposites for hyperthermia treatment

Nanocomposites of magnetite (Fe3O4) and reduced graphene oxide (rGO) generate heat under an alternating magnetic field and therefore have potential applications as thermoseeds for cancer hyperthermia treatment. However, the properties of such nanocomposites as biomaterials have not been sufficiently well characterized. In this study, the osteoconductivity of Fe3O4-rGO nanocomposites of various compositions was evaluated in vitro in terms of their apatite-forming ability in simulated body fluid (SBF). Furthermore, the heat generation of the nanocomposites was measured under an alternating magnetic field. The apatite-forming ability in SBF improved as the Fe3O4 content in the nanocomposite was increased. As the Fe3O4 content was increased, the nanocomposite not only rapidly raised the surrounding temperature to approximately 100 °C, but the specific absorption rate also increased. We assumed that the ionic interaction between the Fe3O4 and rGO was enhanced and that Brown relaxation was suppressed as the proportion of rGO in the nanocomposite was increased. Consequently, a high content of Fe3O4 in the nanocomposite was effective for improving both the osteoconductivity and heat generation characteristics for hyperthermia applications.

Calcium phosphate coating on dental composite resins by a laser-assisted biomimetic process

ObjectivesDental composite resins with better biocompatibility and osteoconductivity have been sought in endodontic treatments. This study aimed to develop a technique to produce the osteoconductive resin surfaces through calcium phosphate (CaP) coating using a laser-assisted biomimetic (LAB) process. MethodsLight-cured, acrylic-based composite resins were used as substrates. The resin substrate was subjected to a LAB process comprising Nd:YAG pulsed laser irradiation in a supersaturated CaP solution. The LAB-processed substrate was immersed for 3 days in a simulated body fluid (SBF) for the preliminary osteoconductivity assessment. ResultsAfter irradiation for 30 min, the resin surfaces were partly coated with a newly formed CaP layer. The coating layer contained hydroxyapatite as the main crystalline phase and the coating coverage depended on the laser wavelength and the type of resin. The LAB-processed CaP-coated surface exhibited apatite-forming ability in SBF. ConclusionsLAB process is effective for CaP coating on light-cured dental composite resins and improving their osteoconductivity. Clinical significanceThe LAB process is a potential new tool to create a cementum-like osteoconductive surface on dental composite resins.

Surface structure and in vitro apatite-forming ability of titanium doped with various metals

Surface modification by sodium hydroxide (NaOH) and subsequent heat treatment can provide titanium and its alloys an apatite-forming ability in simulated body fluid (SBF), and is used clinically to treat titanium alloy hip joints in Japan. However, there is no systematic study on the relationship between the amount and chemical state of metals incorporated into titanium and the apatite-forming ability in SBF. We have studied this relationship herein by treating NaOH–modified titanium with aqueous solutions containing different types (aluminum, calcium, chromium, copper, zinc, and silver) and concentrations (0.01, 0.1, and 1 M) of metal ions. As a result, we found that formation of anatase and the chemical states of the metals incorporated into titanium control the apatite-forming ability. Further, the chemical states of the metals can be interpreted in terms of the ionization tendency. These findings would aid future design of metal-doped bioactive titanium for orthopedic or dental implants.

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.

Biomineralization behavior of a vinylphosphonic acid-based copolymer added with polymerization accelerator in simulated body fluid

Apatite-polymer composites have been evaluated in terms of its potential application as bone substitutes. Biomimetic processes using simulated body fluid (SBF) are well-known methods for preparation of such composites. They are reliant on specific functional groups to induce the heterogeneous apatite nucleation and phosphate groups possess good apatite-forming ability in SBF. Improving the degree of polymerization is important for obtaining phosphate-containing polymers, because the release of significant quantities of monomer or low molecular weight polymers can lead to suppression of the apatite formation. To date, there have been very few studies pertaining to the effect of adding a polymerization accelerator to the polymerization reaction involved in the formation of these composite materials under physiological conditions. In this study, we have prepared a copolymer from triethylene glycol dimethacrylate and vinylphosphonic acid (VPA) in the presence of different amounts of sodium p-toluenesulfinate (p-TSS) as a polymerization accelerator. The effects of p-TSS on the chemical durability and apatite formation of the copolymers were investigated in SBF. The addition of 0.1–1.0 wt% of p-TSS was effective for suppressing the dissolution of the copolymers in SBF, whereas larger amount had a detrimental effect. A calcium polyvinylphosphate instead of the apatite was precipitated in SBF.

Bioactivity and degradability of hybrids nano-composites materials with great application as bone tissue substitutes

In this work, hybrids with great application as bioactive materials having different compositions based on siloxane network were prepared. In vitro bioactivity and in vitro degradability tests were carried out in the materials by soaking them into simulated body fluid (SBF) and into phosphate buffer solution (PBS) to prove their apatite-forming ability and to show their degradation process, respectively. In both in vitro tests, measurements of pH and loss weight were made to observe bioactivity and degradation processes. To prove growth of HA, the materials were characterized through X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. The results showed that some samples have better bioactivity than others. It was found that the incorporation of CaO component into the network of the materials results in an increase of the apatite-forming ability in SBF. Moreover, during the degradation tests, all the samples presented weight loss, especially the ones that contain CaO.

Characteristics of heat-treated plasma-sprayed CaO–MgO–SiO2-based bioactive glass–ceramic coatings on Ti–6Al–4V alloy

In this study, a novel CaO–MgO–SiO2-based bioactive glass–ceramic M2 (43.19% CaO–7.68% MgO–49.13% SiO2 (wt.%)) was coated onto Ti–6Al–4V substrates by atmospheric plasma spraying (APS) to evaluate its application potentials in biomedicine. The bonding strength, phase composition and morphologies of commercial plasma-sprayed hydroxyapatite (HA, Ca10(PO4)6(OH)2) coatings and M2 coatings before and after heat treatment at 650–800°C were investigated. The M2 coatings were soaked in simulated body fluid (SBF) to evaluate their bioactivity in vitro, and the cytocompatibility in vitro was detected by osteoblast proliferation, differentiation and adhesion assays. The results indicated that heat treatment could induce recrystallization of the as-sprayed M2 coatings, and the optimum condition for heat treatment might be 800°C for 6h in air. Compared with commercial HA coating, the micro-cracks in the heat-treated M2 coating were much less, and the bonding strength of M2 coating to Ti–6Al–4V substrate was nearly twice as much as that of HA coating. In addition, M2 coating possessed a bone-like apatite-formation ability in SBF. The M2 coating extracts at certain concentrations could stimulate the proliferation and differentiation of osteoblasts, and cells adhered and spread well on M2 coatings, indicating good bioactivity and cytocompatibility in vitro.

Bioactive glass/ZrO2 composites for orthopaedic applications

Binary biocomposites were realized by combining yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with a bioactive glass matrix. Few works are available regarding composites containing zirconia and a relatively high content of glass because the resulting samples are usually biocompatible but not bioactive after thermal treatment. In the present research, the promising properties of the new BG_Ca–K glass, with its low tendency to crystallize and high apatite-forming ability, allowed us to sinter the composites at a relatively low temperature with excellent effects in terms of bioactivity. In addition, it was possible to benefit from the good mechanical behaviour of Y-TZP, thus obtaining samples with microhardness values that were among the highest reported in the literature. After a detailed analysis regarding the thermal behaviour of the composite powders, the sintered bodies were fully characterized by means of x-ray diffraction, SEM equipped with EDS, density measurements, volumetric shrinkage determination, mechanical testing and in vitro evaluation in a simulated body fluid (SBF) solution. According to the experimental results, the presence of Y-TZP improved the mechanical performance. Meanwhile, the BG_Ca–K glass, which mainly preserved its amorphous structure after sintering, provided the composites with a good apatite-forming ability in SBF.

Microstructural design of functionally graded coatings composed of suspension plasma sprayed hydroxyapatite and bioactive glass

Various bioactive glass/hydroxyapatite (HA) functional coatings were designed by the suspension plasma spraying (SPS) technique. Their microstructure, scratch resistance, and apatite-forming ability in a simulated body fluid (SBF) were compared. The functional coatings design included: (i) composite coating, that is, randomly distributed constituent phases; (ii) duplex coating with glass top layer onto HA layer; and (iii) graded coating with a gradual changing composition starting from pure HA at the interface with the metal substrate up to pure glass on the surface. The SPS was a suitable coating technique to produce all the coating designs. The SBF tests revealed that the presence of a pure glass layer on the working surface significantly improved the reactivity of the duplex and graded coatings, but the duplex coating suffered a relatively low scratch resistance because of residual stresses. The graded coating therefore provided the best compromise between mechanical reliability and apatite-forming ability in SBF. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 551-560, 2014.

Effect of Autoclave and Hot Water Treatment on Surface Structure and Apatite-Forming Ability of NaOH- and Heat-Treated Titanium Metals in Simulated Body Fluid

Sodium hydroxide (NaOH)-, heat- and autoclave-treated Ti metal did not form apatite in simulated body fluid (SBF) within 7 days although certain amounts of sodium (Na) still remained on the Ti metal surface even after the autoclave treatment. When hot water treatment was applied between NaOH and heat treatment, the Ti metal formed apatite within 7 days in SBF. Anatase-type TiO2 was partially precipitated by the NaOH and heat treatment but it was disappeared by the subsequent autoclave treatment. When the hot water treatment was applied between the NaOH and heat treatment, considerable amount of anatase-type TiO2 was formed and it still remained even after the autoclave treatment. The zeta potential of the Ti metal with the hot water treatment was almost zero in SBF. These results indicate that Ti metal can show apatite-forming ability in SBF even after autoclave treatment, when hot water treatment is applied between the NaOH and heat treatment, and that anatase-type TiO2 might play an important role in the apatite formation rather than the amount of Na and/or the zeta potential.

The Influence of Na and Ti on theIn VitroDegradation and Bioactivity in 58S Sol-Gel Bioactive Glass

The aim of this study was to investigate the effect of Na and Ti on thein vitrodegradation and bioactivity in the 58S bioactive glass. The degradation was evaluated through the activation energy of Si ion release from bioactive glasses and the weight loss of bioactive glasses in Tris-HCl buffer solution. Thein vitrobioactivity of the bioactive glasses was investigated by analysis of apatite-formation ability in the simulated body fluid (SBF). The results showed that Na in the 58S glass accelerated the dissolution rate of the glass, whereas Ti in the 58S glass slowed down the rate of glass solubility. Bioactivity tests showed that Na in glass increased the apatite-forming ability in SBF. In contrast, Ti in glass retards the apatite formation at the initial stage of SBF soaking but does not affect the growth of apatite after long periods of soaking.

In vitro bioactivity and cytocompatibility of tricalcium silicate

The in vitro bioactivity of tricalcium silicate (Ca3SiO5) ceramics was investigated by the bone-like apatite-formation ability in simulated body fluid (SBF), and the cytocompatibility was evaluated through osteoblast adhesion and proliferation assay. The results show that the Ca3SiO5 ceramics possess bone-like apatite formation ability in SBF. In vitro cytocompatible evaluation reveals that osteoblasts adhere and spread well on the Ca3SiO5 ceramics, indicating good bioactivity and cytocompatibility.

Effect of heat treatments on apatite-forming ability of NaOH- and HCl-treated titanium metal

Titanium (Ti) metal was soaked in HCl solution after NaOH treatment and then subjected to heat treatments at different temperatures. Their apatite-forming abilities in a simulated body fluid (SBF) were discussed in terms of their surface structures and properties. The nanometer scale roughness formed on Ti metal after NaOH treatment remained after the HCl treatment and a subsequent heat treatment below 700°C. Hydrogen titanate was formed on Ti metal from an HCl treatment after NaOH treatment, and this was converted into titanium oxide of anatase and rutile phases by a subsequent heat treatment above 500°C. The scratch resistance of the surface layer increased with the formation of the titanium oxide after a heat treatment up to 700°C, and then decreased with increasing temperature. The Ti metal with a titanium oxide layer formed on its surface showed a high apatite-forming ability in SBF when the heat treatment temperature was in the range 500-700°C. The high apatite-forming ability was attributed to the positive surface charge in an SBF. These positive surface charges were ascribed to the presence of chloride ions, which were adsorbed on the surfaces and dissociated in the SBF to give an acid environment.

Preparation and in vitro evaluation of nanostructured TiO 2/TCP composite coating by plasma electrolytic oxidation

Porous and nanostructured TiO 2/tricalcium phosphate (TCP) composite coating on titanium substrate was prepared by plasma electrolytic oxidation (PEO). The microstructure and phase composition of the coating were characterized using scanning electron microscopy and X-ray diffraction. Its bioactivity was evaluated by simulated body fluid (SBF) immersion tests. MG63 cells were cultured on the surface of the coating to investigate its cytocompatibility. Potentiodynamic polarization tests were applied to measure its corrosion resistance. The results revealed that rough and hydrophilic TiO 2/TCP composite coating with pores of several micrometers and grains of 50–200 nm was prepared by one-step PEO treatment. The TiO 2/TCP composite coating showed good apatite-forming ability in SBF, and the TCP phase in the coating played an important role in inducing apatite formation. MG63 cells could adhere and proliferate on the surface of the coating, indicating its good cytocompatibility. The composite coating also exhibited good corrosion resistance in 0.9% NaCl solution.

Effect of MgO contents on the mechanical properties and biological performances of bioceramics in the MgO–CaO–SiO2 system

The aim of this research was to investigate the effect of the chemical composition on the mechanical properties, bioactivity, and cytocompatibility in vitro of bioceramics in the MgO-CaO-SiO(2) system. Three single-phase ceramics (merwinite, akermanite and monticellite ceramics) with different MgO contents were fabricated. The mechanical properties were tested by an electronic universal machine, while the bioactivity in vitro of the ceramics was detected by investigating the bone-like apatite-formation ability in simulated body fluid (SBF), and the cytocompatibility was evaluated through osteoblast proliferation and adhesion assay. The results showed that their mechanical properties were improved from merwinite to akermanite and monticellite ceramics with the increase of MgO contents, whereas the apatite-formation ability in SBF and cell proliferation decreased. Furthermore, osteoblasts could adhere, spread and proliferate on these ceramic wafers. Finally, the elongated appearance and minor filopodia of cells on merwinite ceramic were more obvious than the other two ceramics.

Fabrication of Apatite-Hyaluronic Acid Hybrids

Apatite-polymer hybrids have been attractive as novel bone-bonding bioactive bone substitutes with mechanical performances analogous to those of natural bone. It is shown that carboxyl group (COOH) can induce the apatite nucleation in an environment of simulated body fluid (SBF). In the present study, we fabricated porous hyaluronic acid gels abundant in COOH group and investigated their apatite formation ability in SBF. Hyaluronic acid has been attractive for boneand cartilagerepairing materials due to high biological compatibility. We attempted the preparation of bioactive organic-inorganic hybrids from Hyaluronic acid. It has been attractive for boneand cartilage-repairing materials due to high biological compatibility. It is known that divinyl sulfone is a candidate of cross-linker to bridge the hydroxyl groups. The hydroxyl group of hyaluronic acid side chains were bridged by divinyl sulfone. Porous hyaluronic acid gels stable in aqueous environment were obtained by appropriate crosslinking. They formed the apatite on their surfaces in SBF, when they were priorly treated with CaCl2 aqueous solution. In addition, trehalose, a kind of disaccharide, is found to increase the pore size of the porous hyaluronic acid. This suggests that the pore size and porosity can be controlled by addition of trehalose during fabrication of the scaffolds.

Synthesis and characterization of multiphase bioactive glass-ceramics in the CaO–MgO–SiO2 system with B2O3 additive

A glass-ceramic (GC0) with nominal composition of 51.2% CaO–12.1% MgO–36.7% SiO2 (wt%) was synthesized. Then multiphase glass-ceramics of MGC1 and MGC2 were obtained by adding 1 and 2 wt% B2O3 to GC0 followed by thermal treatment. The bending strength of MGC1 was the highest, about 89.46 MPa, and the coefficient of thermal expansion was 10.67 × 10−6 °C−1, closer to that of Ti–6Al–4V alloy (10.03 × 10−6 °C−1). X-ray diffraction analysis confirmed that MGC1 was predominantly composed of akermanite, merwinite, and small amounts of dicalcium silicate crystalline phases. The bioactivity and cytocompatibility in vitro of MGC1 were detected by investigating the bonelike apatite-formation ability in simulated body fluid (SBF) and osteoblast morphology and viability. The results showed that MGC1 possessed bonelike apatite-formation ability in SBF and could release ionic products to significantly stimulate cell growth and viability. Furthermore, osteoblasts adhered and spread well on MGC1, indicating good bioactivity and potential cytocompatibility.

Improvement of mechanical and biological properties of porous CaSiO 3 scaffolds by poly( d, l-lactic acid) modification

Porous calcium silicates (CaSiO 3, WT) are regarded as a potential bioactive material for bone tissue engineering. However, their insufficient mechanical strength and high dissolution (degradation) limit their biological applications. The aim of this study is to surface modify WT scaffolds with poly( d, l-lactic acid) (PDLLA) to improve their mechanical and biological properties. The phase composition, microstructure, porosity and interconnectivity of WT and PDLLA-modified WT (WTPL) scaffolds were analyzed by X-ray diffraction, scanning electron microscopy and micro-computerized tomography. The WTPL scaffolds maintained a more uniform and continuous inner network, compared to that of the WT scaffolds, while maintaining the pore size, porosity and interconnectivity of the original materials. The compressive strength, compressive modulus and percentage strain of the WT and WTPL scaffolds were assessed in air and phosphate-buffered saline. PDLLA modification significantly improved the compressive strength and decreased the brittleness of the WT scaffolds. The weight loss and apatite-forming ability of the two scaffolds were evaluated by soaking them in simulated body fluid (SBF) for 1, 3, 7, 14 and 28 days. PDLLA modification decreased the dissolution of the WT scaffolds while maintaining their apatite-forming ability in SBF. In addition, PDLLA modification improved the spreading and viability of human bone-derived cells. Our results indicate that PDLLA-modified CaSiO 3 scaffolds possess improved mechanical and biological properties, suggesting their potential application for bone tissue regeneration.

Synthesis and characteristics of monticellite bioactive ceramic

Mono-phase ceramics of monticellite (CaMgSiO4) were successfully synthesized by sintering sol-gel-derived monticellite powder compacts at 1,480 degrees C for 6 h. The mechanical properties and the coefficient of thermal expansion (CTE) of the monticellite ceramics were tested. In addition, the bioactivity in vitro of the monticellite ceramics was evaluated by investigating their bone-like apatite-formation ability in simulated body fluid (SBF), and the biocompatibility in vitro was detected by osteoblast adhesion and proliferation assay. The results showed that the bending strength, fracture toughness and Young's modulus of the monticellite ceramics were about 159.7 MPa, 1.63 MPa m1/2 and 51 GPa, respectively. The CTE was 10.76x10(-6) degrees C(-1) and close to that of Ti-6Al-4V alloy (10.03x10(-6) degrees C(-1)). Furthermore, the monticellite ceramics possessed bone-like apatite-formation ability in SBF and could release soluble ionic products to significantly stimulate cell growth and proliferation. In addition, osteoblasts adhered and spread well on the monticellite ceramics, which indicated good bioactivity and biocompatibility.