Formation Of Carbonated Hydroxyapatite Research Articles

Structural and in vitro study of cerium, gallium and zinc containing sol–gel bioactive glasses

Sol–gel derived glasses comprised of bioactive materials exhibit a high in vitro response, i.e., the capability to form a hydroxycarbonate apatite (HCA) layer that is claimed to be responsible for the bonding between the glass and the host bone. In this paper, the sol–gel bioactive glass 80% SiO2–15% CaO–5% P2O5 (B_BG) was modified by adding the biologically relevant elements cerium, gallium and zinc. Structural characterization of the glasses was performed by 29Si MAS NMR and their in vitro response was investigated by soaking them in simulated body fluid (SBF) for up to 15 days at 37 °C. The HCA formation was monitored by XRD, FTIR, SEM-EDS and ICP measurements. Ce3+, Ga3+, and Zn2+ can be classified as “intermediate ions”. However, 29Si NMR revealed that Ce3+ ions have a more marked role of “modifier ions” than Ga3+ ions, while the behavior of Zn2+ lies between those of Ce3+ and Ga3+. On the other hand, in spite of the decrease in the in vitro response of B_BG by substitution, the glasses show HCA formation after 15 days of soaking. In addition, an increase in substitution of zinc accelerated the formation of HCA along with the formation of the mixed phase CaZn2(PO4)2·2H2O (scholzite) acting as nucleating agent for HCA. Moreover, the therapeutic effect of optimum Zn released as an ionic dissolution product from Zn-glasses could be beneficial to stimulate osteogenesis.

Influence of strontium for calcium substitution in bioactive glasses on degradation, ion release and apatite formation

Bioactive glasses are able to bond to bone through the formation of hydroxy-carbonate apatite in body fluids while strontium (Sr)-releasing bioactive glasses are of interest for patients suffering from osteoporosis, as Sr was shown to increase bone formation both in vitro and in vivo. A melt-derived glass series (SiO(2)-P(2)O(5)-CaO-Na(2)O) with 0-100% of calcium (Ca) replaced by Sr on a molar base was prepared. pH change, ion release and apatite formation during immersion of glass powder in simulated body fluid and Tris buffer at 37°C over up to 8 h were investigated and showed that substituting Sr for Ca increased glass dissolution and ion release, an effect owing to an expansion of the glass network caused by the larger ionic radius of Sr ions compared with Ca. Sr release increased linearly with Sr substitution, and apatite formation was enhanced significantly in the fully Sr-substituted glass, which allowed for enhanced osteoblast attachment as well as proliferation and control of osteoblast and osteoclast activity as shown previously. Studying the composition-structure-property relationship in bioactive glasses enables us to successfully design next-generation biomaterials that combine the bone regenerative properties of bioactive glasses with the release of therapeutically active Sr ions.

Hydroxyapatite Coatings Incorporating Silicon Ion Releasing System on Titanium Prepared Using Water Glass and Vaterite

A new type of bioactive coating with the ability to release soluble silica species was prepared on a titanium substrate surface using water glass and vaterite (CaCO3) particles and precipitating hydroxycarbonate apatite (HCA) from solution. Silica was incorporated because soluble silica and calcium ions have been reported to stimulate osteogenic cells to produce new bone matrix. Water glass was coated on the substrate surface and then heated at 300°C for 2 h and then soaked in 0.1M HCl aqueous solution at 50°C for 120 min, resulting in the formation of silica layer on the surface. One of vaterite, calcite, aragonite, or CaCl2 was coated on the silica layer to enhance HCA formation on the surface in modified simulated body fluid (1.5 SBF). Vaterite was found to encourage the most rapid HCA formation. The titanium substrates coated with silica and HCA layers, continuously released about 53 mM of silicon species a day. The HCA layer contained a trace amount of silicon, which was expected to be released from the silica layer and trapped in the layer during 1.5 SBF‐soaking. Osteoblast‐like cells (MC3T3‐E1) proliferated better on the substrate releasing soluble silica than on an HCA layer on titanium containing no silica.

Biomimetic Apatite Mineralization Mechanisms of Mesoporous Bioactive Glasses as Probed by Multinuclear 31P, 29Si, 23Na and 13C Solid-State NMR

An array of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy experiments is applied to explore the surface reactions of a mesoporous bioactive glass (MBG) of composition Ca0.10Si0.85P0.04O1.90 when subjected to a simulated body fluid (SBF) for variable intervals. Powder X-ray diffraction and 31P NMR techniques are employed to quantitatively monitor the formation of an initially amorphous calcium phosphate surface layer and its subsequent crystallization into hydroxycarbonate apatite (HCA). Prior to the onset of HCA formation, 1H → 29Si cross-polarization (CP) NMR evidence dissolution of calcium ions; a slightly increased connectivity of the speciation of silicate ions is observed at the MBG surface over 1 week of SBF exposure. The incorporation of carbonate and sodium ions into the bioactive orthophosphate surface layer is explored by 1H → 13C CPMAS and 23Na NMR, respectively. We discuss similarities and distinctions in composition−bioactivity relationships established for traditio...

Synthesis and characterization of three-dimensional ordered mesoporous–macroporous bioactive glass

Three-dimensional ordered mesoporous–macroporous bioactive glass (MMBG) was synthesized by a combination of surfactant and polystyrene bead templates, the sol–gel method, and the evaporation-induced self-assembly process. The incorporation of regular spherical macropores only slightly perturbed the mesoporous network. The bioactivity of the MMBG was assessed by its immersion in simulated body fluid for different lengths of time and the subsequent determination of hydroxycarbonate apatite formation. The synthesized MMBG displayed good in vitro bioactivity and may have potential applications in bone tissue engineering.

Investigation of the physico-chemical reactivity of a mesoporous bioactive SiO 2–CaO–P 2O 5 glass in simulated body fluid

A new mesoporous bioactive glass (MpBaG) based on SiO 2–CaO–P 2O 5 by the sol–gel method has been successfully synthesized for biomedical applications. The obtained material was evaluated by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and N 2 adsorption analysis. The N 2 adsorption isotherm analysis showed that the pores were in mesopore size range and the MpBaG presented a specific surface area 137.9 m 2 g − 1 and a median pore size 15.4 nm. The surface reactivity of the MpBaG was studied in vitro in simulated body fluid (SBF). Inductively coupled plasma-atomic emission spectrometry (ICP-AES), SEM, EDS, XRD and FTIR were used to characterize the MpBaG surfaces and the SBF compositional changes. Immediately after immersion in SBF, reactions occurred on the surface of MpBaG. It is notable that the obtained results from FTIR and XRD analyses showed all typical characteristic peaks of bone-like hydroxyapatite (HAp). Also, it was obvious that the other new peaks after immersion in SBF were certainly related to the formation of hydroxycarbonate apatite (HCAp) and carbonate calcium (calcite). Finally, this research demonstrated that the synthesized MpBaG is a non-toxic and biocompatible material for ongoing osteogenic studies in segmental defects in the goat model in vivo.

Synthesis and in vitro bioactivity of ordered mesostructured bioactive glasses with adjustable pore sizes

Four ordered mesoporous bioactive glasses (MBGs) with the same composition and hexagonal mesostructure but adjustable pore diameters (1.9, 3.4, 5.0, 6.4 nm, denoted MBGs A–D, respectively) have been prepared for the first time by using different structure-directing agents as templates. Their in vitro bioactivities have been carefully studied by investigating the formation of hydroxycarbonate apatite (HCA) on MBG surfaces. MBG A with the smallest pore diameter (1.9 nm) shows the fastest nucleation rate of HCA, however, the total amount of calcium phosphate (CaP) species deposited after immersing in SBF for 2 days is the smallest among four MBG samples under study. The in vitro bioactivity sequence of MBGs with different pore sizes is determined to be MBG C ≈ D > B > A in terms of the total amount of CaP species deposition. MBG A has the highest surface area and thinnest wall thickness, which favor the rapid release of Ca and P species from the wall framework and thus fasten the nucleation rate. Nevertheless, the small pore of MBG A may be easily blocked by the nucleates, which is disadvantageous for the subsequent ionic diffusion and crystal growth of HCA. Our results have indicated that the fast nucleation does not necessarily correlate to a high amount of HCA deposition, which is important in the evaluation of the in vitro bioactivity of BG-related biomaterials. By understanding the relationship between the pore structure and the in vitro bioactivity, it is anticipated that MBGs with controllable mesostructure and enhanced bioactivity can be designed and fabricated.

Fabrication and characterization of bioactive silk fibroin/wollastonite composite scaffolds

Composite scaffolds of silk fibroin (SF) with bioactive wollastonite were prepared by freeze-drying. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy analysis showed that random coil and β-sheet structure co-existed in the SF scaffold. The mechanical performance, surface hydrophilicity and water-uptake capacity of the composite scaffolds were improved compared with those of pure SF scaffold. The bioactivity of the composite scaffold was evaluated by soaking in a simulated body fluid (SBF), and formation of a hydroxycarbonate apatite (HCA) layer was determined by FT-IR and XRD. The results showed that the SF/wollastonite composite scaffold was bioactive as it induced the formation of HCA on the surface of the composite scaffold after soaking in SBF for 5 days. In vitro cell attachment and proliferation tests showed that the composite scaffold was a good matrix for the growth of L929 mouse fibroblast cells. Consequently, the incorporation of wollastonite into the SF scaffold can enhance both the mechanical strength and bioactivity of the scaffold, which suggests that the SF/wollastonite composite scaffold may be a potential biomaterial for tissue engineering.

SiO2−P2O5−CaO Glasses and Glass-Ceramics with and without ZnO: Relationships among Composition, Microstructure, and Bioactivity

Bioactive glasses and glass-ceramics of the system SiO2−P2O5−CaO with and without zinc were synthesized by sol−gel with the aim to address the influence of both the chemical composition and the microstructure on the growth of hydroxycarbonate apatite (HCA) following soaking in simulated body fluid (SBF). In the standard compositions 58S, 70S, and 80S the silica precursor was also partially replaced with a nanoscale silica powder (HiSil) in order to separate the contributions of porosity and composition. The combined use of XRPD, N2 absorption measurements, and SEM allowed us to establish quantitative correlations among the above-mentioned quantities. We found that the HCA formation rate increases with the silica content and that an important role is played by the specific surface area of the samples. Notably, the addition of even small quantities (0.4 wt %) of ZnO at the expenses of both CaO and P2O5 in the 58S glass leads to the increase, with respect to the 58S sample, of both the HCA formation rate and the HCA content after 8 days of treatment in SBF. A preliminary result revealed that sample with 0.4 wt % ZnO displayed good in vitro biocompatibility as shown by LDH assay.

An Evaluation of CaF<sub>2</sub> Doping Tricalcium Silicate as Dental Restorative Materials

The aim of this study was to evaluate the suitability of CaF2 doping tricalcium silicate (Ca3SiO5, C3S) as dental restorative materials. The solid state reaction method was used to prepare CaF2 doping C3S (F-C3S) using CaCO3, SiO2 and CaF2 as the starting materials. The in vitro bioactivity, the rate of heat evolution and the compressive strength were investigated. The in vitro bioactivity was examined by soaking the pastes in simulated body fluid (SBF). The FTIR and SEM results indicated the hydroxycarbonate apatite (HCA) layers of F-C3S pastes and pure C3S pastes occurred after soaking for 1 day and 3 days, respectively. The difference in bioactivity was attributed to the formation of F-substituted apatite, which has a Ksp lower than HCA. As compared with the pure C3S, the rate of heat evolution during the hydration of F-C3S was slower. This was avail to the dimensional stability of dental restorative materials. The pastes of F-C3S had a lower early compressive strength in the early stage, but a higher compressive strength in the later stage. Our results indicated that F-C3S would be bonded better to the teeth because of the earlier formation of HCA and the higher later compressive strength. F-C3S may be a progressive candidate for dental restorative materials.

Fabrication and in vitro characterization of magnetic hydroxycarbonate apatite coatings with hierarchically porous structures

Hydroxycarbonate apatite/Fe 3O 4 composite coatings (MHACs) with hierarchically porous structures were fabricated by electrophoretic deposition of CaCO 3/Fe 3O 4 particles on Ti6Al4V substrates followed by treatment with phosphate buffer solution (PBS) at 37 °C. The effects of Fe 3O 4 on the conversion rate of calcium carbonate to hydroxycarbonate apatite and the porous structures and in vitro bioactivity of MHACs were investigated. After soaking CaCO 3/Fe 3O 4 coatings in PBS, hydroxycarbonate apatite nucleates heterogeneously on the surfaces of CaCO 3/Fe 3O 4 particles and forms a plate-like structure. Fe 3O 4 increases the velocity of nucleus formation of hydroxycarbonate apatite. After soaking for 1 day, the percentage of unreacted calcium carbonate for MHACs is ∼9.1%, lower than the ∼41.0% for hydroxycarbonate apatite coatings (HCACs). As the CaCO 3/Fe 3O 4 coatings are converted to MHACs, macropores with a pore size of ∼4 μm on the coatings and mesopores with a pore size of ∼3.9 nm within the hydroxycarbonate apatite plates are formed. The mesopores remain in the MHACs after treatment with PBS for 9 days, while they disappear in the HCACs. Simulated body fluid immersion tests reveal that Fe 3O 4 improves the in vitro bioactivity of biocoatings. The amount of bone-like apatite precipitated on the surfaces of MHACs is greater than that on the surfaces of HCACs.

Analysis of in vitro reaction layers formed on 48S4 glass for applications in biomaterial field

The purpose of this work is to study the formation of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) on the surface of glass 48S4 with chemical composition: SiO 2 : 48%, CaO: 30%, Na 2 O: 18% and P 2 O 5 : 4% in weight ratio. This selected composition presents phosphorus contributions lower than that in Bioglass ® [Hench et al. J. Biomed. Mater. 36 , 117 (1971)] developed by L. Hench. Comparison of the kinetic formation of hydroxyapatite on the glass surfaces of these two biomaterials was made. The Material was prepared by melting and rapid quenching. It shows a bioactive character. This phenomenon is confirmed by the “in vitro” formation of hydroxycarbonate apatite (HCA) layer on the surface of glass after immersion in the Simulated Body Fluid (SBF). Before immersion in SBF, The proposed composition of glass was analyzed using several physicochemical methods like XRD, FTIR, SEM, and EDS confirming the composition and its amorphous state well. The pellets were soaked in SBF for 2 h, 1, 3, 7 and 15 days at 37 °C. The analyses of SBF after each immersion time were carried out using ICP-OES method. Results show important exchanges of ions between the surface of glass and the SBF. They revealed the formation of an amorphous CaO-P 2 O 5 - rich layer on the surface of the specimens after 1 day in the solution and a crystalline HCA layer after 3 days immersion time as will be shown by XRD, EDS and FTIR analysis. The cristallinity increases with immersion time. After 15 days immersion in SBF liquid, the specimens are still fully covered by hydroxycarbonate apatite (HCA) layer.

Compositional dependence on the in vitro bioactivity of invert or conventional bioglasses in the Si‐Ca‐Na‐P system

The bioactivity of 34 invert or conventional glasses in the P-free and P-containing Si-Ca-Na system was evaluated by examining the in vitro Hydroxy Carbonate Apatite (HCA) formation time. The silica content in the glasses varies between 39.48 and 55 mol %. The surfaces of glasses after soaking in simulated body fluid at 37 degrees C were analyzed by Fourier transform infraRed spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. To understand the HCA formation mechanism, the modification of the glass surface structure was studied. The aim was to understand, in the Si-Ca-Na-P system, the function of each constituent on glass reactivity. It was noted that the bioactivity of Si-Ca-Na-P glasses depends on the P ratio. One of the P-free glasses is as bioactive as the Hench's Bioglass noted 45S5, because it needs 12 h to develop HCA as for Hench's one. In the quaternary system, some of the P-rich and Na, Si-poor glasses are more bioactive than 45S5 (6-10 h to obtain HCA). Two phosphorus effects were observed: the repolymerization of the silicate network and the formation of phosphate-modifier cation complexes.

Poly- ε-caprolactone/hydroxyapatite for tissue engineering scaffold fabrication via selective laser sintering

Rapid prototyping (RP) techniques are becoming more popular for fabricating tissue engineering (TE) scaffolds owing to their advantages over conventional methods, such as the ability to fabricate scaffolds with predetermined interconnected networks without the use of organic solvents. A versatile RP technique, selective laser sintering (SLS), offers good user control of scaffold microstructure by adjusting the process parameters. This research focuses on a the use of biocomposite material, consisting of poly- ε-caprolactone (PCL) and hydroxyapatite (HA), to fabricate TE scaffolds using SLS. Biocomposite blends with different percentage weights of HA were physically blended and sintered to assess their suitability for fabrication via SLS. Optimal sintering conditions for the powders were achieved by varying parameters such as laser power and scan speed. Studies of the sintered specimen morphology were performed by scanning electron microscopy. Thermogravimetric analysis confirmed the homogeneity of the biocomposite blend. Simulated body fluid (SBF) samples show the formation of hydroxy carbonate apatite, as a result of soaking HA in a SBF environment. Cell culture experiment showed that Saos-2 cells were able to live and replicate on the fabricated scaffolds. The results show the favorable potential of PCL/HA biocomposite as TE scaffolds that are fabricated via SLS.

In Vitro Bioactivity Characterization of K-Mica-Fluorapatite Based Glass Ceramics Containing Varying Amount of TiO<sub>2</sub> Addition

The purpose of this study is to investigate the crystallization behavior and in-vitro bioactivity character of glass ceramics having 3:7 weight ratio of flourapatite (Ca5(PO4)3F) to potassium mica (K2Mg3AlSi3O10F2) as a function of titania addition, and compare the morphology of hydroxycarbonateapatite (HCA) layer formation depending on titania addition on ceramic composition. It is observed from microstructural investigations that there is no morphology change occurred on precipitated HCA layer depending on nucleating agent in glass-ceramics. TF-XRD analysis indicates that after precipitation of initial particulates, crystallization proceeds and crystallization of precipitated HCA phase increases by increasing the time. It is observed that Ca, P ion variation in solution has two stage in terms of precipitation’ first stage represents formation of amorphous HCA and the second stage is related with crystallization. FTIR analysis strongly supports TF-XRD analysis as well.

Nanoporous hydroxy-carbonate apatite scaffold made of natural bone

A processing method of hydroxy-carbonate apatite (HCAp) from the natural bone and their phase purity, crystal structure, chemical functionality, thermal stability, morphology, and solubility are described in this investigation. The X-ray diffraction analysis suggested that the processed bone corresponds characteristically to carbonate (CO 3 2−) containing hydroxyapatite. Fourier transform infrared spectroscopic study confirmed the presence of CO 3 2− in addition to hydroxyl (OH −) and phosphate (PO 4 3−) functional groups, indicating the formation of HCAp. Environmental scanning electron microscopy was employed to identify the surface morphology of HCAp, which obviously shows a nanoporous structure throughout the matrix. The in vitro solubility study performed under physiological conditions confirms the resorbable nature of HCAp. These findings indicate the feasibility of processing nanoporous HCAp scaffolds from the natural bone by a straightforward method.

HYDROXYCARBONATE APATITE COATING ON CALCIUM CARBONATE COMPOISTES BY A BIOMIMETIC METHOD

Hydroxycarbonate apatite (HCA) coatings on two types of composites containing calcium carbonates were prepared by a biomimetic method using simulated body fluid (SBF). Poly(lactic acid) (PLA) composites containing calcium carbonates formed HCA on the surface after soaking in SBF for 3 h. The PLA composites had numerous carboxy groups bonded with Ca2+ ions. Titania composites containing calcium carbonates formed HCA on the surface after soaking in SBF for 1 d. Formation of titanium hydroxide groups was drastically promoted on the titania composite by soaking in SBF. The HCA-forming ability of these composites was much higher than that of PLA or titania crystals. Vaterite in the composites plays an important role in HCA formation in SBF. By soaking in SBF, a large amount of Ca2+ ions released from the vaterite increase in the supersaturation of HCA in SBF.

Highly Ordered Mesoporous Bioactive Glasses with Superior In Vitro Bone‐Forming Bioactivities

Large pore volumes and highly accessible mesopore surface areas are present in highly ordered mesoporous bioactive glasses (MBGs) prepared by a block copolymer templating approach under non-aqueous conditions. These glasses have a high bone-forming bioactivity in vitro, as shown by immersing them in simulated body fluid (SBF) and monitoring the formation of hydroxycarbonate apatite (HCA) on the surface (see electron micrographs).

Hydroxy Carbonate Apatite Formation on Particulate Bioglass In Vitro as a Function of Time

The mechanism of bonding of bioactive glasses with living tissues has been reported to be associated with the development of a layer consisting of carbonate-containing hydroxyapatite similar to that of bone on the surface of the materials. This layer is also formed in vitro, in solutions with ion concentrations similar to those of human blood plasma, like SBF (Simulated Body Fluid). The development of HCAp (Hydroxy carbonate apatite) layer on the surface of a commercially available Bioglass® Synthetic Bone Graft Particulate (Perioglas®) after immersion in SBF solution using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) with associated Energy Dispersive Spectroscopy (EDS). PerioGlas® powder with particle size 20-63μm, pressed in a vacuum press in order to produce pellets. The pellets were soaked in SBF for 12, 18, 24 and 48 hours at 37°C. Results revealed the formation of an amorphous CaO-P2O5- rich layer on the surface of the specimens after 12 hours in the solution and a well crystalline HCAp layer after 24 hours immersion time.

Application of Raman microspectroscopy to the characterisation of bioactive materials

Bioactive materials offer a more stable and stronger bond between the living tissue and the implant than bioinert materials due to reactions occurring at the material surface when implanted. These reactions lead to formation of a biologically active hydroxycarbonate apatite (HCA) layer to which the living tissue can strongly adhere. It is therefore of primary importance to be able to characterise in vitro the formation of such HCA layers. We report on the use of Raman microspectroscopy to characterise the surface reactions occurring in two types of bioactive materials after immersion in simulated body fluid (SBF) or phosphate buffer saline (PBS). The materials investigated were (1) sol–gel derived bioactive 58S glass foams and (2) bioresorbable polylactic (PDLLA) and poly(lactic-coglycolic) acid (PLGA) foams containing bioactive glass particles (45S5 Bioglass). The results show that Raman microspectroscopy is a very sensitive technique for qualitative and quantitative detection of HCA formation on the materials under different in vitro conditions.