Ceramics In Simulated Body Fluid Research Articles

Bioactive calcium phosphate foam ceramics modified by biomimetic apatite

By combining the method of replication of polyurethane foam matrices at 1200 °C and modification in model SBF (Simulated Body Fluid) solutions of various compositions, open-pore calcium phosphate foam ceramics with a porosity of 53-60 % was obtained. The architecture and morphology of the calcium phosphate foam ceramics surface was formed by using polyurethane foam matrices («Granufoam», «STR») with different porosity and quantity of open pores. Modification of the calcium phosphate foam ceramics in SBF solutions of various compositions leads to a slight decrease in porosity to 3 %, which indicates the formation of an ultrathin apatite layer. The calcium phosphate-modified foam ceramics consisted of β-tricalcium phosphate, β-calcium pyrophosphate, α-tricalcium phosphate, and biomimetic apatite. In the standard SBF solution, the formation of apatite on calcium phosphate foam ceramics occurs slowly (14-56 days) and the strength increases by a factor of 2 as compared to the initial one. Soaking of calcium phosphate foam ceramics in SBF without HCO3- leads to the formation of biomimetic apatite with inclusions of calcium chloride dihydrophosphate in spherulites. Modification in a 5-fold concentrated SBF solution for 3-5 days at 37 °C makes it possible to form 6-10 times more biomimetic apatite compared to standard SBF with a 2.5-fold increase in static strength to 0.05 MPa. It has been established that at 800 °C biomimetic apatite crystallizes into β- tricalcium phosphate.

Novel Porous Forsterite Ceramics Biocompatibility and Bioactivity Evaluation

This study is aimed to evaluate the biocompatibility and bioactivity of some new porous forsterite ceramics (FCs) produced from high-purity nano forsterite powder, synthesized by an original sol-gel method, which was subjected to pressing into pellets, by using a poly vinyl alcohol solution as a binding component. Then, the raw pellets were sintered at 1200 �C, 1300 �C, 1400 �C and 1450 �C. The obtained four forsterite ceramics, FC-1200, FC-1300, FC-1400 and FC-1450, were fully characterized by density, porosity and shrinkage measurements. The forsterite ceramics exhibited excellent biocompatibility determined by an in vitro cell viability assay, such as MTT test. Furthermore, the in vitro bioactivity test was performed by immersing the forsterite ceramics into simulated body fluid (SBF) and examining the hydroxyapatite (HAP) formation on forsterite ceramics, as evidenced by XRD, FTIR, SEM with EDX. Moreover, the relationship between porous structure and bioactivity of forsterite ceramics in SBF as well as the performance of FC in a cell culture was evaluated. The findings strongly recommend these forsterite ceramics for biomedical applications, as potential bone substitutes.

Preparation and in vitro apatite-forming ability of hydroxyapatite and β-wollastonite composite materials

This paper provides a one-step method of preparation of the ceramic powders, containing various amounts of hydroxyapatite (HA) and β-wollastonite (WT), based on the salt coprecipitation and subsequent thermal treatment of the synthesis products at 1000 °C. Aqueous solutions of Ca(OH)2, H3PO4 and Na2SiO3 were used as precursors of Ca10(PO4)6(OH)2 and β-CaSiO3, as a minimal amount of by-product is formed during such an interaction of reagents. Variation of the concentration of the initial reagents allows the preparation of ceramic powders containing from 0 to 100 wt% of apatite. All composites were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), laser diffraction analysis and an adsorption method (BET). Degradability of composite powders was analyzed in the Tris-HCl buffer solution. The apatite-forming ability of synthetic composites was investigated by soaking composite ceramics in a simulated body fluid (SBF). The results that were obtained reveal an increase in the dissolution rate of powders with wollastonite addition. Soaking of the composite ceramics in SBF leads to the formation of a bone-like apatite spherical particle layer on their surfaces, which become thicker while the content of β-СаSiO3 in the samples increases.

Nanostructured monticellite for tissue engineering applications - Part I: Microstructural and physicochemical characteristics

In this study, nanostructured monticellite (CaMgSiO4) bioceramics were prepared via sintering the sol–gel-derived monticellite powder compacts at 1200 °C. The mean of particles size distribution of the synthesized monticellite powders was approximately 90 nm. After evaluating physicochemical characteristics of the synthesized bioceramics, apatite-forming ability of the samples were examined in simulated body fluid (SBF) for different time periods. The soaking effect of various time periods on the X-ray diffraction (XRD) patterns, followed by the calculations from scherrer's equation, showed that the crystallite size of the immersed monticellite ceramics in SBF for 3 and 7 days was around 88 nm. Williamson-Hall analysis was also used to calculate the lattice strain of the samples. Based on the results, by changing the soaking time, crystallite size and lattice strain have meaningfully changed. The release of Ca, Mg and Si ions from the nanostructured monticellite significantly promoted cell proliferation and growth at a certain concentration range more than that of positive and negative controls. This study could provide an in-depth understanding of the microstructural and physicochemical characteristics of this class of biomaterials. The follow-up studies should correlate the microstructural and physicochemical properties to the molecular and biological characteristics for applications in tissue engineering and regenerative medicine.

Surface reactivity and hydroxyapatite formation on Ca5MgSi3O12 ceramics in simulated body fluid

In this work, the new calcium-magnesium-silicate Ca5MgSi3O12 ceramic was made via traditional solid-state reaction. The bioactivities were investigated by immerging the as-made ceramics in simulated body fluid (SBF) for different time at body temperature (37°C). Then the samples were taken to measure X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy-dispersive spectra (EDS), and Fourier transform infrared spectroscopy (FT-IR) measurements. The bone-like hydroxyapatite nanoparticles formation was observed on the ceramic surfaces after the immersion in SBF solutions. Ca5MgSi3O12 ceramics possess the Young’s modulus and the bending strength and of 96.3±1.2GPa and 98.7±2.3MPa, respectively. The data suggest that Ca5MgSi3O12 ceramics can quickly induce HA new layers after soaking in SBF. Ca5MgSi3O12 ceramics are potential to be used as biomaterials for bone-tissue repair. The cell adherence and proliferation experiments are conducted confirming the reliability of the ceramics as a potential candidate.

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.

In situ hydroxyapatite nanofiber growth on calcium borate silicate ceramics in SBF and its structural characteristics.

A novel calcium silicate borate Ca11Si4B2O22 ceramic was firstly prepared by the conventional solid-state reaction. In vitro hydroxyapatite mineralization was investigated by soaking the ceramics in simulated body fluid (SBF) solutions at body temperature (37 °C) for various time periods. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) measurements were applied to investigate the samples before and after the immersion of ceramics in SBF solution. The elemental compositions of a hydroxyapatite layer on the ceramics during the mineralization were confirmed by X-ray energy-dispersive spectra (EDS). Meanwhile, the bending strength and elastic modulus of Ca11Si4B2O22 ceramics were also measured, which indicate that the biomaterials based on Ca11Si4B2O22 ceramics possess bioactivity and might be a potential candidate as biomaterials for hard tissue repair. The bioactive mineralization ability was evaluated on the base of its crystal structural characteristics, i.e., silanol (Si-OH) and B-OH groups can be easily induced on the surface of Ca11Si4B2O22 ceramics soaked in SBF solutions.

Sol–gel synthesis, structure, sintering and properties of bioactive and inert nano-apatite–zirconia glass–ceramics

We synthesized four glasses of the system 61.2SiO2–(24.3–x)CaO–4.5P2O5–10ZrO2–xK2O (x=0, 2, 4, 6mol%=Ca replaced by K) using a sol–gel route and compared their properties with a 68SiO2–27CaO–5P2O5 (mol%) Zr-free base glass. Their structure, sintering and crystallization behavior were investigated with the aim of converting the gel-glasses into dense glass–ceramics. Then, the in vitro bioactivity and mechanical properties of the optimized sintered samples were characterized. The structure of the gel-glasses was investigated by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and high-resolution transmission electron microscopy (HR-TEM). The sintering and crystallization kinetics of the glasses were studied by hot stage microscopy (HSM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The microstructures of the resulting glass–ceramics were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with energy dispersive spectroscopy (EDS). The apatite-forming ability of the sintered glass–ceramics in simulated body fluid (SBF) was investigated using FTIR spectroscopy and SEM. The three-point bending strength, Vickers microhardness and fracture toughness were also measured. Structural analysis by NMR and FTIR revealed that Zr acts as a glass former and K is a modifier, as expected. The K2O addition strongly improved the material׳s sinterability, e.g., 2mol% K2O decreased the optimum sintering temperature from 1300°C to 1050°C. Uniformly dispersed ZrO2 nano-crystals, with particle sizes of 25–55nm, were precipitated in the glass–ceramics. In vitro bioactivity tests confirmed that the K2O-free glass–ceramics (partially sintered at 1000°C) were bioactive and hydroxycarbonate apatite (HCA) grew on their surface after 24h in SBF. However, the >90% dense glass–ceramics with various contents of K2O exhibited low solubility and a much smaller tendency toward HCA formation. Improvement of some mechanical properties was observed for the sample containing 2mol% K2O, in which apatite and zirconia crystallized. The 3p-bending strength and fracture toughness of the 94% dense sample were approximately 140MPa and 2MPam1/2, respectively. We propose that crack deflection by the ZrO2 crystals and the presence of Zr ions in the residual glass network are prevalent for improving the materials׳ mechanical properties. Some potential applications, such as bioactive scaffolds, are suggested for these glass–ceramics.

Characterization and <i>In Vitro</i> Evaluation of Silicate-Containing Tricalcium Phosphate Prepared through Wet Chemical Process

Tricalcium phosphate (TCP) ceramics are useful biodegradable bone-repairing materials. Silicate-containing TCP ceramics are expected to be useful as biodegradable bone-repairing materials which promote the bone regeneration because it has been reported that the silicate promotes bone formation. In the present study, silicate-containing TCP ceramics were prepared through a wet chemical process at the starting compositions from 0 to 0.05 in the Si/(P+Si) molar ratio. The prepared silicate-containing TCP ceramics were characterized and evaluated in vitro. The crystal phase of the products was α-TCP, and the tendency that the lattice constants linearly shifted from 0 to 0.05 in the starting Si/(P+Si) molar ratio was observed. It is speculated that the added silicate was incorporated in the crystal structure of TCP. The pellets were prepared by a sintering process, and soaked in a simulated body fluid (SBF) to estimate their bone-bonding ability. The addition of silicate to TCP promoted to hydroxyapatite formation on the TCP ceramics in SBF. This result implies the high possibility that the silicate addition would promote the bone-bonding ability of the TCP ceramics.

Effect of akermanite morphology on precipitation of bone-like apatite

Bioactivity in vivo of ceramic materials has been related to their surface micro-topography and may be estimated by means of simulated body fluid method in vitro. In order to investigate the effect of surface topographies of akermanite ceramics on bioactivity in vitro, akermanite ceramics were synthesized by sol–gel method and different surface topographies of disc-shaped akermanite ceramics were prepared by polishing with different SiC sandpapers. Atomic force microscopy (AFM) was used to evaluate the surface morphology and roughness. The bioactivity in vitro of ceramics with different surface states was evaluated by soaking the ceramics in simulated body fluid (SBF). And the samples after being soaked were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The results showed that the amounts of precipitated apatite on the ceramics with different surface roughness after being soaked in SBF were different and the bioactivity in vitro of ceramic with rough surface was significantly higher than that of ceramic with smooth surface. The study suggested that suitable surface roughness may improve the bioactivity in vitro of akermanite ceramics.

Tribological behavior of alumina-added apatite–wollastonite glass–ceramics in simulated body fluid

Tribological properties of an alumina-added apatite–wollastonite glass–ceramic produced by controlled heat treatment of a glass in the system MgO–CaO–SiO 2–P 2O 5–Al 2O 3 have been evaluated and compared with those of selected commercial dental ceramics, Duceragold and IPS Empress. Tribological tests were performed in dry condition and in simulated body fluid (SBF) using a pin-on-disk apparatus. The friction coefficient and specific wear rate of the tested materials were measured in dry and in artificial saliva (simulated body fluid: SBF) in order to elucidate the appropriateness of the alumina-added apatite–wollastonite (A–W) glass–ceramic for dental applications. Wear rate of the materials investigated varied from 0.96 × 10 −4 mm 3 N −1 m to 41.37 × 10 −4 mm 3 N −1 m depending on the bioenvironmental test conditions. The results of this study revealed that the alumina-added A–W glass–ceramic becomes more wear resistant as sintering temperature is increased and exhibits tribological properties similar to those of the commercial dental materials investigated.

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass–ceramics having iron oxide

The effect of ZnO on phase emergence and microstructure properties of glass and glass–ceramics with composition 25SiO 2–50CaO–15P 2O 5–(10 − x)Fe 2O 3– xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass–ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass–ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 °C calcium phosphate, hematite and magnetite are developed as major phases in the glass–ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca 3Si 2O 7) phase is also observed when glass is heat treated at 1000 °C. The microstructure of the glass–ceramics heat treated at 800 °C exhibits the formation of nano-size (40–50 nm) grains. On heat treatment at 1000 °C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration ( x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca–P-rich layer on the glass–ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.

Electrovector effect on bone-like apatite crystal growth on Inside pores of polarized porous hydroxyapatite ceramics in simulated body fluid

Porous hydroxyapatite (HA) disks and blocks with interconnecting pores (pore size≅150 μm, interconnecting window size≅30 μm, and porosity≅75%) were polarized and bone-like apatite formations on the pore surfaces were investigated by immersion test using simulated body fluid (SBF) to estimate the electrovector effect in porous bodies. Thermally stimulated depolarization current (TSDC) measurements were used to estimate the stored charges of polarized porous HA disks and blocks as 11 and 7 μC cm-2, respectively, demonstrating that both the porous disks and blocks were successfully polarized. After immersion in SBF for 14 d, bone-like apatite formations within the pores were observed in the polarized and non-polarized HA disks and blocks. Based on scanning electron microscopic (SEM) images of the pores located around the center of the disks and the blocks (inside-pores), formation of bone-like apatite was accelerated in the polarized HA compared with that in the non-polarized HA. Although the weight of the polarized and non-polarized porous HA increased linearly with immersion time regardless of shape, the rate of weight change of the polarized HA was greater than that of the non-polarized HA. It was demonstrated that the electric charges on the inside-pore surface of porous HA have a positive effect on the formation of bone-like apatite crystals.

Preparation and Characterization of CaSiO<sub>3</sub>-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> Composite Bioceramics

In this study, CaSiO3 (CS)/Ca3(PO4)2 (TCP) composites with 50% CS and 50% TCP sintered at different temperatures (1100oC, 1200oC and 1300oC) were prepared. The formation of bone-like apatite on CS-TCP composites was investigated by soaking the ceramics in simulated body fluid (SBF), and the presence of bone-like apatite layer on the composite surface after soaking in SBF was determined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results showed that the bone-like apatite was formed on all the CS-TCP composites sintered at different temperatures after 7 days of immersion. In addition, the degradation of CS-TCP composites prepared at different temperatures was evaluated by measurement of weight loss of the ceramics in Tris-HCl buffer solution at 37oC, and the results showed that there was no difference in degradation rate between the samples. In vitro cell experiments indicated that the osteoblasts proliferated faster on the CS-TCP ceramics sintered at higher temperature, and cells on the CS-TCP ceramics sintered at 1300oC showed highest proliferation rate. These results provide valuable information for designing CS-TCP composite bioceramics for bone regeneration applications.

In vitro bioactivity of novel tricalcium silicate ceramics

In this study, bone-like apatite-formation ability of tricalcium silicate (Ca(3)SiO(5)) ceramics in simulated body fluid (SBF) was evaluated and the in vitro degradability was investigated by soaking in Ringer's solution. The effect of ionic products from Ca(3)SiO(5) dissolution on osteobalsts proliferation was investigated. The result indicated that hydroxyapatite (HA) was formed on the surface of the Ca(3)SiO(5) ceramics after soaking in SBF for 1 day, and Ca(3)SiO(5) ceramics could degraded in Ringer's solution. The Si ions from Ca(3)SiO(5) dissolution at certain concentration range significantly stimulated osteoblasts proliferation. Our results show that Ca(3)SiO(5) ceramics possess bone-like apatite-formation ability and degradability, and can release soluble ionic products to stimulate cell proliferation.

Chemicovector Effect of Nano-Size-Hydroxyapatite Doped YSZ Ceramics on Apatite Formability in SBF

To produce ceramics with high mechanical strength and bioactivity, we developed the little amount of nano-sized hydroxyapatite (HA)-doped zirconia composite ceramics (nanoHA-Z). The bioactivity of the nanoHA-Z was studied by in vitro estimation with simulated body fluid (SBF). Scanning electron microscopy observation showed deposited bone-like apatite layer entire covering the surface of nanoHA-Z ceramics in SBF. The enhanced apatite formability was attributed to higher Ca and PO4 concentrations in the vicinities of the nanoHA-Z surfaces due to the dissolution of the β-tricalcium phosphate decomposed from the added HA. Utilization of Chemicovector effect was proved to be one of the powerful approaches for improvement method of biomaterials.

Enhancement of Bone-Like Apatite Forming Abilities of Calcium Phosphate Ceramics in SBF by Autoclaving

Bone-like hydroxyapatite (b-HA) formation abilities of /?-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) after autoclaving were evaluated by immersion tests using simulated body fluid (SBF). The b-HA formation was observed on an autoclaved β-TCP, while no deposition was observed on the non-autoclaved one. The b-HA formation on HA was observed to be enhanced after autoclaving. Decrease of surface potentials by autoclaving may enhance the b-HA formation abilities.

Delayed Fatigue of Hydroxy- and Fluorhydroxyapatite Ceramics in Simulated Body Fluid

Ultrafine hydroxyapatite (HA) and fluorhydroxyapatite (FHA) powders were synthesized and dense bioceramic samples were fabricated thereof. The samples were treepoint bend tested in different environments, i.e. in ambient air, distilled water and simulated human saliva, in the wide deformation rate range. Weibull’ statistics test was performed under standard testing conditions but in different media. The stress velocity exponent was evaluated from the dynamic fatigue testing data. The mean strength is shown to decrease when both ceramics are exposed to water or to simulated saliva. HA ceramics is more susceptible to the environment compared to FHA ceramics, due to the later is less subjected to the stress corrosion. Fracture surface observations revealed the crack propagation is of mixed trans- and intergranular mode. Strength distribution changes from uni-modal in air environment to bimodal in harsh conditions of water and saliva, indicating slow increment of flaw size in ceramics. Crack velocity exponent values correspond to transient region from dissociative chemisorption to ion solvation mechanisms of stress corrosion in both HA and FHA ceramics. Generally, FHA ceramics is considered to be much more reliable for application in bone defects replacement or dental reconstruction.

Effect of solid/solution ratio on apatite formation from CaSiO3 ceramics in simulated body fluid

The effect of the solid/solution (S/S) ratio on apatite formation from CaSiO3 ceramics in simulated body fluid (SBF) was investigated. CaSiO3 ceramics with a Ca/Si ratio of 0.91 were prepared by sintering CaSiO3 powder coprecipitated from ethanol solutions of Ca(NO3)2. 4H2O and Si(OC2H5)4 using NH4OH as the precipitant. These ceramics were reacted with SBF at S/S ratios of 1.0, 2.5 and 8.3 mg/ml at 36.5 degrees C for various times. Formation of apatite was observed at all the S/S ratios after soaking for 1 day. The amount and microstructure of the apatite obtained at a S/S ratio of 8.3 mg/ml, however, differed largely from the product formed at the other two S/S ratios. The apatite formed at S/S = 8.3 mg/ml was of smaller particle size, formed in smaller amount and with less preferred orientation of the (001) of apatite crystals compared with those formed at S/S = 1.0 and 2.5 mg/ml. An increase of Ca and decrease of the P components occurred in the soaked SBF at S/S = 8.3 mg/ml, the changes being much more marked than with the other two S/S ratios. These differences in the concentration changes in SBF at different S/S ratios are attributed to the difference in the apatite formation from the CaSiO3 ceramics.

Formation of apatite layers on modified canasite glass-ceramics in simulated body fluid.

Canasite glass-ceramics were modified by either increasing the concentration of calcium in the glass, or by the addition of P2O5. Samples of these novel materials were placed in simulated body fluid (SBF), along with a control material (commercial canasite), for periods ranging from 12 h to 28 days. After immersion, surface analysis was performed using thin film X-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopy equipped with energy dispersive X-ray detectors. The concentrations of sodium, potassium, calcium, silicon, and phosphorus in the SBF solution were measured using inductively coupled plasma emission spectroscopy. No apatite was detected on the surface of commercial canasite, even after 28 days of immersion in SBF. A crystalline apatite layer was formed on the surface of a P2O5-containing canasite after 5 days, and after 3 days for calcium-enriched canasite. Ion release data suggested that the mechanism for apatite deposition was different for P2O5 and non-P2O5-containing glass-ceramics.