Ability In Simulated Body Fluid Research Articles

Effects of Ca/P molar ratios on regulating biological functions of hybridized carbon nanofibers containing bioactive glass nanoparticles

Biological functions of hybridized carbon nanofibers (CNFs) depend closely on the incorporated bioactive components. For hybridized CNFs containing bioactive glass (BG) nanoparticles (CNF/BG), chemical compositions of BG nanoparticles might have decisive effects on their cell affinity and osteocompatibility. Herein, three hybridized CNF/BGs were produced by incorporating 68S-type BG nanoparticles with different Ca/P molar ratios (1.0, 1.67 or 2.5) into CNFs via a sol–gel/electrospinning and carbonization method. Structural evolution of these hybridized CNF/BGs was studied in relation to their Ca/P molar ratios. Crystalline wollastonite was found to be the dominant phase at a high feeding Ca/P molar ratio (i.e. 2.5), but weak crystallized hydroxyapatite was the main phase at the low feeding Ca/P molar ratio (i.e. 1.0). These findings were correlated to the biological functions of the resulted CNF/BG hybrids including apatite formation ability in simulated body fluid and osteoblast behaviors in in vitro culture. All the CNF/BG hybrids displayed a strong affinity for inducing apatite deposition, showing insignificant difference after the initial nucleation stage, while they behaved differently in promoting the proliferation and osteogenic differentiation of osteoblasts. The fastest proliferation rate and the highest expression of alkaline phosphatase activity was found on the CNF/BG (Ca/P = 1.0). The results suggested a feasible way to upregulate osteoblast behaviors is by changing the feeding Ca/P molar ratios in the preparation of CNF/BG hybrids for potential bone repairing applications.

Effect of surface charge of TiO2 particles on hydroxyapatite formation in simulated body fluid

TiO2 particles formed by heat treatment in a nitrogen atmosphere with an extremely low oxygen partial pressure exhibited high hydroxyapatite (HAp)-forming ability in simulated body fluid (SBF). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS) indicated that the particles were rutile-type TiO2, which contains hardly any nitrogen. Electron spin resonance (ESR) spectra revealed the reduction of Ti4+ in TiO2 to Ti3+ and the simultaneous introduction of oxygen vacancies to maintain charge neutrality. The enhanced HAp-forming ability of the TiO2 particles was likely related to their negatively charged surface, induced by water adsorption on oxygen vacancies, which resulted in acidic point formation. In contrast, TiO2 particles formed by heat treatment in air showed low HAp-forming ability because their surfaces had almost zero charge.

In vitro bioactivity studies of larnite and larnite/chitin composites prepared from biowaste for biomedical applications

Larnite (Ca2SiO4) was synthesized by the sol–gel combustion process by using raw eggshell powder as a calcium source and urea as a fuel. The main focus of this work is to convert biowaste into a biomedical material at a low-processing temperature. X-ray diffraction (XRD) pattern confirms the phase purity of the larnite and Fourier transform infrared (FTIR) spectra confirms the presence of characteristic functional groups of larnite. Scanning electron microscopy (SEM) image shows agglomerated particles with cauliflower-like morphology and energy dispersive X-ray spectroscopy (EDX) confirms the presence of the stoichiometric ratio of required elements. Atomic force microscope (AFM) images reveal the presence of pores on the surface of spherical particles. Larnite/chitin composites were fabricated into scaffold with different ratios of bioceramic to biopolymer (70:30, 80:20) to investigate the influence of the polymer content on the apatite formation ability in simulated body fluid (SBF) medium. XRD pattern and FTIR spectra of the scaffold immersed in SBF shows apatite deposition within 5 days. The deposition of hydroxyapatite (HAP) on the scaffold surface increases with the increase in polymer content of the composite.

Synthesis, physico-chemical and biological characterization of strontium and cobalt substituted bioactive glasses for bone tissue engineering

Due to their vast potential for repair and regeneration, different types of bioactive glasses (BGs) have been widely studied for bone tissue engineering. In this study, different groups of melt-derived bioactive glasses containing strontium (Sr2+) and cobalt (Co2+) ions have been designed to investigate their potential effect on increasing cell osteogenic activity. After full characterization of the synthesized bioactive glasses, they were evaluated for apatite forming ability in simulated body fluid (SBF) after different time intervals. The glasses have been examined for cell attachment and cell cytotoxicity plus their influence on osteogenic activity of the cells was analyzed by alkaline phosphatase assay (ALP) and alizarin red staining. The results show that the samples are in glassy state before immersion in SBF and an apatite-like layer has formed on the surface of SBF-immersed samples after 3, 7 and 14days. In vitro experiments demonstrated that the incorporation of Sr2+ and Co2+ in the glass composition significantly promote osteogenic activity of human osteosarcoma cells without any cytotoxicity effect.

Bioactive effect of alkali-heat treated TiO 2 nanotubes by water or acid treatment

Abstract Various surface treatments are used to enhance the biological activity of titanium. Alkali and heat treatments promote the formation of hydroxyl apatite (HAp), which increases the bone-bonding ability in simulated body fluid (SBF). The sodium titanate layer is converted to the more bioactive layer, with sodium-ion removal from alkali- and heat-treated surfaces, via a water treatment. The anatase phase resulting by water treatment is effective in generating apatite nuclei in SBF. In this study, two types of surface treatment were performed to improve the bioactivity of alkali and heat-treated TiO 2 nanotubes: One is the only water treatment for 48 h. Another is the combination of the acid-solution (10 and 50 mM of HCl or HNO 3 ) treatment for 24 h and the water treatment for 24 h. Each treatment was conducted after the fabrication of alkali-treated TiO 2 nanotubes via anodization and an alkali treatment in 5 M NaOH. Finally, all of the treated groups were all heated at 550 °C. The properties, bioactivity, and cytotoxicity of the alkali-heat treated TiO 2 nanotubes were determined after the water or acid treatment. In addition, histological samples were evaluated by inserting implants into bilateral rat tibia for 3 and 6 weeks. The concentration of O ions and the amount of anatase phase increased after the HCl treatment. Furthermore, the apatite-forming ability was greatly enhanced with an increase in the amount of anatase phase, especially in the 50 mM HCl-treated group. The surface of the water- or 50 mM HCl-treated group promoted osteoblastic proliferation and differentiation, thereby allowing effective osteointegration. In the 6-week implant, the uniform new bone layer grew in the case of the HC50 group only. Therefore, we conclude that the HCl treatment constitutes the most favorable surface-modification method for improving the bioactivity of alkali- and heat-treated TiO 2 nanotubes.

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.

Crack-free polydimethylsiloxane–bioactive glass–poly(ethylene glycol) hybrid monoliths with controlled biomineralization activity and mechanical property for bone tissue regeneration

Crack-free organic–inorganic hybrid monoliths with controlled biomineralization activity and mechanical property have an important role for highly efficient bone tissue regeneration. Here, biomimetic and crack-free polydimethylsiloxane (PDMS)–modified bioactive glass (BG)–poly(ethylene glycol) (PEG) (PDMS–BG–PEG) hybrids monoliths were prepared by a facile sol–gel technique. Results indicate that under the assist of co-solvents, BG sol and PDMS and PEG could be hybridized at a molecular level, and effects of the PEG molecular weight on the structure, biomineralization activity, and mechanical property of the as-prepared hybrid monoliths were also investigated in detail. It is found that an addition of low molecular weight PEG can significantly prevent the formation of cracks and speed up the gelation of the hybrid monoliths, and the surface microstructure of the hybrid monoliths can be changed from the porous to the smooth as the PEG molecular weight increases. Additionally, the hybrid monoliths with low molecular weight PEG show the high formation of the biological apatite layer, while the hybrids with high molecular weight PEG exhibit negligible biomineralization ability in simulated body fluid (SBF). Furthermore, the PDMS–BG–PEG 600 hybrid monolith has significantly high compressive strength (32±3MPa) and modulus (153±11MPa), as well as good cell biocompatibility by supporting osteoblast (MC3T3-E1) attachment and proliferation. These results indicate that the as-prepared PDMS–BG–PEG hybrid monoliths may have promising applications for bone tissue regeneration.

Electrophoretic deposition of calcium silicate–reduced graphene oxide composites on titanium substrate

Calcium silicate (CS)/graphene coatings have been used to improve the biological and mechanical fixation of metallic prosthesis. Among the extraordinary features of graphene is its very high mechanical strength, which makes it an attractive nanoreinforcement material for composites. Calcium silicate–reduced graphene oxide (CS–rGO) composites were synthesized, using an in situ hydrothermal method. CS nanowires were uniformly decorated on the rGO, with an appropriate interfacial bonding. The CS–rGO composites behaved like hybrid composites when deposited on a titanium substrate by cathodic electrophoretic deposition (EPD). Compared to a pure CS coating on Ti, the CS–1wt% rGO coating has improved adhesion by 70%, hardness by 150% and the elastic modulus by 240%. The CS–rGO composite coatings exhibit good apatite-forming ability in simulated body fluid (SBF). Moreover, the effect of addition of rGO on morphology, adhesion and proliferation of human osteoblast cells (hFOB) was investigated in vitro.

Microstructure, in vitro bioactivity and degradability of various magnesia-containing wollastonite

Wollastonite (CaSiO3) ceramics with various magnesia contents (0, 5, 10, 15 and 20mol%) were successfully prepared by sintering sol–gel derived precursors. The effects of MgO content on microstructure, in vitro bioactivity and degradability of wollastonite were reported. The ceramics are composed of β-CaSiO3. When adding 5mol% MgO, the new phase of Ca3Mg(SiO4)2 forms. With increasing MgO content, CaMgSi2O6 and Ca2MgSi2O7 form. All ceramics possess apatite formation ability in simulated body fluid. The TEM results indicated that the ceramic structure is polycrystal. MgO decreases the total pore volume of wollastonite and the degradation rate is decreased gradually with increasing MgO content.

Fabrication and characterization of novel porous titanium microspheres for biomedical applications

Microsphere systems have been widely used in the treatment of defective tissues, including bone, cartilage, and muscle. Although researchers are interested in porous calcium–phosphate microspheres, no articles that discuss the preparation of porous Ti microspheres are present in the literature. In the current study, porous Ti microspheres were successfully fabricated via a water-in-oil emulsion technique using camphene as a porogen and a tailored sintering schedule. The results show that the porous Ti microspheres exhibited an interconnected porous structure with pore sizes ranging from several microns to as large as 200μm, and with various porosities from 49.1% to 74.3%. More than 65% of the pores were larger than 50μm. Additionally, the surfaces of Ti microspheres were modified with NaOH treatment, and then the calcium–phosphate forming ability in simulated body fluid (SBF) solution was investigated to assess bioactivity. After NaOH treatment, the Ti microsphere exhibited a porous network structure, which is a sodium hydrogen titanate reaction layer as confirmed by the XRD results. A dense and uniform calcium–phosphate layer covered the surface of the NaOH-treated Ti microsphere after it was soaked in SBF solution for 14days. However, there is no obvious formation of calcium–phosphate on the surface of the untreated Ti microsphere even after it was soaked in SBF for 14days.

A bioactive Ca2SiB2O7 ceramics and in vitro hydroxyapatite mineralization ability in SBF

Calcium borosilicate Ca2SiB2O7 ceramics were prepared by the conventional solid-state reaction. The detailed crystal structure of the as-prepared ceramics was investigated by X-ray diffraction and structural refinements studies. The mechanical properties were measured by the bending strength and elastic modulus. In vitro hydroxyapatite mineralization ability was investigated by soaking the ceramics in simulated body fluid (SBF) at temperature 37°C for various time periods. HA needles can be easily in vitro induced when the ceramics were soaked in SBF solutions. Scanning electron microscopy (SEM), X-ray diffraction patterns and Fourier transform infrared spectroscopy (FT-IR) analysis were applied to investigate the samples before and after immersion in SBF solutions. The elemental compositions of a hydroxyapatite layer on the surface of ceramics during mineralization were confirmed by X-ray energy-dispersive spectra (EDS). The in vitro mineralization ability was discussed on the base of the structural characteristics of Ca2SiB2O7 ceramic such as the silanol (Si–OH), B–OH groups and pentagonal tunnels and layered structure. The results confirmed that Ca2SiB2O7 ceramics possess good bioactivity and mechanical properties.

Fabrication of biomimetic polysiloxane-bioactive glass–chitosan hybrid monoliths with high apatite-forming bioactivity

The development of biomimetic hybrid implants with high bioactivity is very important for successful bone tissue regeneration. This paper presents a simple strategy for fabricating polydimethylsiloxane–bioactive glass–chitosan hybrid monoliths by a facile sol–gel process. Here, chitosan, which is a critical component in human body, is a natural biocompatible polymer and glycosaminoglycans. Our results indicate that the as-fabricated hybrid monoliths have a porous structure and crack-free morphology, and the in vitro bioactivity test demonstrates that the novel hybrid monoliths have a high apatite-forming ability in simulated body fluid. The facile synthesis, biomimetic structure and composition, as well as high bioactivity of the as-fabricated hybrid monoliths make them promising materials for applications in bone tissue regeneration.

A multinuclear solid state NMR spectroscopic study of the structural evolution of disordered calcium silicate sol-gel biomaterials.

Disordered sol-gel prepared calcium silicate biomaterials show significant, composition dependent ability to bond with bone. Bone bonding is attributed to rapid hydroxycarbonate apatite (HCA) formation on the glass surface after immersion in body fluid (or implantation). Atomic scale details of the development of the structure of (CaO)x(SiO2)1-x (x = 0.2, 0.3 and 0.5) under heat treatment and subsequent dissolution in simulated body fluid (SBF) are revealed through a multinuclear solid state NMR approach using one-dimensional (17)O, (29)Si, (31)P and (1)H. Central to this study is the combination of conventional static and magic angle spinning (MAS) and two-dimensional (2D) triple quantum (3Q) (17)O NMR experiments that can readily distinguish and quantify the bridging (BOs) and non-bridging (NBOs) oxygens in the silicate network. Although soluble calcium is present in the sol, the (17)O NMR results reveal that the sol-gel produced network structure is initially dominated by BOs after gelation, aging and drying (e.g. at 120 °C), indicating a nanoscale mixture of the calcium salt and a predominantly silicate network. Only once the calcium salt is decomposed at elevated temperatures do the Ca(2+) ions become available to break BO. Apatite forming ability in SBF depends strongly on the surface OH and calcium content. The presence of calcium aids HCA formation via promotion of surface hydration and the ready availability of Ca(2+) ions. (17)O NMR shows the rapid loss of NBOs charge balanced by calcium as it is leached into the SBF. The formation of nanocrystalline, partially ordered HCA can be detected via(31)P NMR. This data indicates the importance of achieving the right balance of BO/NBO for optimal biochemical response and network properties.

Calcium silicate and calcium hydroxide materials for pulp capping: biointeractivity, porosity, solubility and bioactivity of current formulations.

The chemical-physical properties of novel and long-standing calcium silicate cements versus conventional pulp capping calcium hydroxide biomaterials were compared. Calcium hydroxide-based (Calxyl, Dycal, Life, Lime-Lite) and calcium silicate-based (ProRoot MTA, MTA Angelus, MTA Plus, Biodentine, Tech Biosealer capping, TheraCal) biomaterials were examined. Calcium and hydroxyl ion release, water sorption, interconnected open pores, apparent porosity, solubility and apatite-forming ability in simulated body fluid were evaluated. All calcium silicate materials released more calcium. Tech Biosealer capping, MTA Plus gel and Biodentine showed the highest values of calcium release, while Lime-Lite the lowest. All the materials showed alkalizing activity except for Life and Lime-Lite. Calcium silicate materials showed high porosity values: Tech Biosealer capping, MTA Plus gel and MTA Angelus showed the highest values of porosity, water sorption and solubility, while TheraCal the lowest. The solubility of water-containing materials was higher and correlated with the liquid-to-powder ratio. Calcium phosphate (CaP) deposits were noted on materials surfaces after short aging times. Scant deposits were detected on Lime-Lite. A CaP coating composed of spherulites was detected on all calcium silicate materials and Dycal after 28 days. The thickness, continuity and Ca/P ratio differed markedly among the materials. MTA Plus showed the thickest coating, ProRoot MTA showed large spherulitic deposits, while TheraCal presented very small dense spherulites. calcium silicate-based cements are biointeractive (ion-releasing) bioactive (apatite-forming) functional biomaterials. The high rate of calcium release and the fast formation of apatite may well explain the role of calcium silicate biomaterials as scaffold to induce new dentin bridge formation and clinical healing.

Molecular level-based bioactive glass-poly (caprolactone) hybrids monoliths with porous structure for bone tissue repair

Molecular level-based silicate bioactive glass (BG)-polymer hybrid materials have attracted much attention in bone tissue regeneration, due to their biomimetic structure and bioactivity. However, few successes have been achieved for preparing synthetic biopolymers-based bioactive glass hybrid materials, because of their non-miscible characteristic. Here, the molecular level scale bioactive glass-poly (ε-caprolactone) (MBG-PCL) hybrid monoliths with porous surface structure were successfully fabricated by a polydimethylsiloxane modified sol-gel technique. The as-prepared hybrid monolith presented a porous structure and crack-free morphology. The in vitro bioactivity test showed that the novel MBG-PCL hybrid structure exhibited high apatite-forming ability in simulated body fluid (SBF). The composition, porous structure, as well as high bioactivity of the hybrid monoliths make them a promising candidate as bioactive implants for bone tissue regeneration.

Long-term antibiotic delivery by chitosan-based composite coatings with bone regenerative potential

Composite coatings with bone-bioactivity and drug-eluting capacity are considered as promising materials for titanium bone implants. In this work, drug-eluting chitosan-bioactive glass coatings were fabricated by a single-step electrophoretic deposition technique. Drug-loading and -releasing capacity of the composite coatings were carried out using the vancomycin antibiotic. Uniform coatings with a thickness of ∼55μm containing 23.7wt% bioactive glass particles and various amounts of the antibiotic (380–630μg/cm2) were produced. The coatings were bioactive in terms of apatite-forming ability in simulated body fluid and showed favorable cell adhesion and growth. In vitro biological tests also indicated that the composite coatings had better cellular affinity than pristine chitosan coatings. The in vitro elution kinetics of the composite coating revealed an initial burst release of around 40% of the drug within the first elution step of 1h and following by a continuous eluting over 4 weeks, revealing long-term drug-delivering potential. Antibacterial tests using survival assay against Gram-positive Staphylococcus aureus bacteria determined the effect of vancomycin release on reduction of infection risk. Almost no bacteria were survived on the coatings prepared from the EPD suspension containing ≥0.5g/l vancomycin. The developed chitosan-based composite coatings with bone bioactivity and long-term drug-delivery ability may be potentially useful for metallic implants to reduce infection risk.

Alternating current electrophoretic deposition of antibacterial bioactive glass-chitosan composite coatings.

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings.

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.

Effect of surface pretreatment and pack cementation on bioactivity of titanium dental implant

The bone‐bonding ability of a material is generally assessed by examining the apatite forming ability in simulated body fluid. The bone‐bonding ability can be increased by increasing the surface roughness and forming a surface similar to the bone. In this study, pretreatments of titanium used for dental implant were anodized at a high voltage to form micropores, and at a low voltage to form nanotubes. In addition, pack cementation was performed on the pretreated specimens in a crucible filled with TTCP (tetracalcium phosphate) powder at 700°C for 24h to impart bioactivity.After pack cementation, apatite formed on the surface of all specimens. In particular, the amount of apatite was higher in the anodized specimens. The specimen immersed in SBF for one day was shown to form apatite on the entire surface due to the effect of anodic oxidation pretreatment of forming nanotube, thereby exhibiting the highest bioactivity. The surface roughness was significantly high in the anodized specimens (P<0.05), and the highest surface roughness was observed in the spark anodized specimen after pack cementation. The biocompatibility was good in all specimens that underwent the surface treatments, and cell differentiation and cell proliferation were activated the most in the nanotube‐anodized specimens after pack cementation. Therefore, strong bonding with the bone is expected as the surface roughness imparted by anodic oxidation results in an increase in implant surface area and corrosion resistance.Overall, the pretreatment and pack cementation are expected to be used for the surface modification of implant materials.

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.