Formation Of Carbonate Apatite Research Articles

Efficient Bioactive Surface Coatings with Calcium Minerals: Step-Wise Biomimetic Transformation of Vaterite to Carbonated Apatite.

Carbonated apatite (CAp), known as the main mineral that makes up human bone, can be utilized in conjunction with scaffolds to increase their bioactivity. Various methods (e.g., co-precipitation, hydrothermal, and biomimetic coatings) have been used to provide bioactivity by forming CAp on surfaces similar to bone minerals. Among them, the use of simulated body fluids (SBF) is the most popular biomimetic method for generating CAp, as it can provide a mimetic environment. However, coating methods using SBF require at least a week for CAp formation. The long time it takes to coat biomimetic scaffolds is a point of improvement in a field that requires rapid regeneration. Here, we report a step-wise biomimetic coating method to form CAp using calcium carbonate vaterite (CCV) as a precursor. We can manufacture CCV-transformed CAp (V-CAp) on the surface in 4 h at least by immersing CCV in a phosphate solution. The V-CAp deposited surface was analyzed using scanning electron microscopy (SEM) images according to the type of phosphate solutions to optimize the reaction conditions. X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis validated the conversion of CCV to V-CAp on surfaces. In addition, the bioactivity of V-CAp coating was analyzed by the proliferation and differentiation of osteoblasts in vitro. V-CAp showed 2.3-folded higher cell proliferation and 1.4-fold higher ALP activity than the glass surface. The step-wise method of CCV-transformed CAp is a biocompatible method that allows the environment of bone regeneration and has the potential to confer bioactivity to biomaterial surfaces, such as imparting bioactivity to non-bioactive metal or scaffold surfaces within one day. It can rapidly form carbonated apatite, which can greatly improve time efficiency in research and industrial applications.

Tunable polymer-peptide hybrids for dentin tissue repair

ObjectivesThis study targets to assess the remineralization capability of conditioned dentin infiltrated with polymeric nanoparticles (NPs) doped with tideglusib (TDg) (TDg-NPs). MethodsDentin conditioned surfaces were infiltrated with NPs and TDg-NPs. Bonded interfaces were created, stored for 24 h and submitted to mechanical and thermal challenging. Resin-dentin interfaces were evaluated through nanohardness, Masson's trichrome staining microscopy, and Raman analysis. ResultsDentin surfaces treated with TDg-NPs and load cycled produced higher nanohardness than the rest of the groups at the hybrid layer. At the bottom of the hybrid layer, all samples treated with TDg-NPs showed higher nanohardness than the rest of the groups. Active remineralization underneath the hybrid layer was detected in all groups after TDg application and load cycling, inducting new dentinal tubuli formation. After thermocycling, remineralization at the hybrid layer was not evidenced in the absence of NPs. Raman analysis showed increase mineralization, enriched carbonate apatite formation, and improved crosslinking and scaffolding of the collagen. ConclusionsMechanical loading on the specimens obtained after TDg-NPs dentin infiltration inducts an increase of mineralization at the resin/dentin interface, indicating remineralization of peritubular and intertubular dentin with augmented crystallographic maturity in crystals. Enriched collagen quality was produced, generating an adequate matrix organization to promote apatite nucleation, after tideglusib infiltration. Clinical significanceAt the present research, it has been proved the creation of reparative dentin, at the resin-dentin interface, after tideglusib dentin infiltration. Chemical stability, to favor integrity of the resin-dentin interface, is warranted in the presence of the TDg-NPs in the demineralized dentin collagen.

Remineralization Potential of Three Restorative Glass Ionomer Cements: An In Vitro Study.

The aim of this in vitro study was to evaluate the remineralizing ability of three glass ionomers on demineralized dentin with different thicknesses and time periods. Fifty third molars were obtained and were sectioned into 1-, 2-, and 3-mm thick slices (n = 36 for each thickness). The specimens were demineralized with 18% EDTA for 2 h. From the glass ionomer cements (GICs) under study (Ketac Molar Aplicap, Equia Forte, or Riva Light Cure), 1 mm was placed over each slice, set, and preserved in PBS until observation after 1, 7, 14, and 28 days after placement. For each material, thickness, and time, three samples were prepared. Using Fourier Transform Infrared Spectrometry (FTIR), apatite formation was determined on the side opposite to that on which the material had been placed. By means of Energy Dispersive Spectroscopy (EDX), the changes in the Calcium/Phosphate (Ca/P) ratio were evaluated. These changes were compared between the different materials by means of a two-way ANOVA test, considering time and dentin thickness, for a significance level of p < 0.05. Results: FTIR showed a peak at 1420 cm-1, evidencing the presence of carbonated hydroxyapatite in all the materials after 14 days, which indicates that a remineralization process occurred. Riva Light Cure showed the most homogeneous results at all depths at 28 days. The Ca/P ratio was maximum at 7 days in 2 mm of dentin for Riva Light Cure and Equia Forte HT (3.16 and 3.07; respectively) and for Ketac Molar at 14 days in 1 mm (3.67). All materials induced remineralization. Equia Forte achieved the greatest effect at 2 mm and Ketac Molar at 1 mm, whereas Riva Light Cure showed similar results at all depths. In terms of Ca/P ratio, Equia Forte and Riva Light Cure remineralized best at 2 mm, whereas for Ketac Molar, it was 1 mm. Carbonate apatite formation was higher at 24 h and 7 days for Ketac Molar, whereas it decreased at 14 days for Ketac Molar and peaked in Riva Light Cure and Equia Forte.

Bioactivity evaluation of printable calcium polyphosphate/alginoplast cement for bone tissue engineering; In vitro study

By developing the three-dimensional (3D) printing technology and patient-specific medicine, 3D calcium phosphate cement, designed for every complex defect, remains a new challenge. This study developed a novel printable calcium polyphosphate (CPP) powder by adding alginoplast (ALG) to fabricated 3D cement using low-temperature binder jetting-based 3D printing without any sintering. The powder flowability and 3D cement biological properties were analyzed using Freeman technology, immersion in simulated body fluid (SBF) solution, and MG63 human osteoblast-like cells culture. According to the Freeman technology, adding 10 wt% of ALG in CPP showed better powder flowability. Together with the SEM, XRD, and FTIR results, the high bioactivity potential of 3D cement containing ALG was recorded by the cauliflower-like carbonate apatite formation on the 3D cement surface after 21 days of immersion. Furthermore, the 3D cement porous microstructure provided a cell attachment. The number of cells showed the 3D cement biocompatibility increased by increasing the cell culture time in 3D cement extraction through the MTT result.

Effect of varying phosphate content on the structure and properties of sol-gel derived SiO2-CaO-P2O5 bio-glass

In this work, biocompatible glass (bioglass) particles were prepared by low temperature, acid catalysed sol-gel method. The effect of varying phosphate (P2O5) content (10, 15 and 20 mol %) in the sol-gel derived glass composition were studied. The sol-gel derived bioglass particles were compacted into cylindrical pellets via hydraulic press machine and sintered at 600°C for 3 hours. The bioglass particulates were analysed by x-ray fluorescence (XRF), Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD) and nitrogen gas adsorption. Meanwhile, the sintered bioglass pellets were analysed by FTIR, XRD and FESEM-EDX. Furthermore, in vitro bioactivity analysis was performed by immersion in simulated body fluid (SBF) for 14 days. Bioglass particulates with high glassy phase, high surface area and high porosities were obtained for all compositions. Increasing of phosphate content to 20 mol% particularly reduced the porous characteristics of the bioglass particulates. Furthermore, leads to higher bridging oxygen (BO) atoms, higher amorphous silicate networks, lower glass crystallinity and higher number of phosphate crystallites within the amorphous glassy matrix. Increased to 20 mol% of phosphate also reduced the ability of the bioglass surface to induce carbonated apatite formation when immersed in simulated body fluid (SBF) solution.

Non-Collagenous Dentin Protein Binding Sites Control Mineral Formation during the Biomineralisation Process in Radicular Dentin.

The biomineralisation of radicular dentin involves complex molecular signalling. Providing evidence of protein binding sites for calcium ions and mineral precipitation is essential for a better understanding of the remineralisation process. This study aimed to evaluate the functional relationship of metalloproteinases (MMPs) and non-collagenous proteins (NCPs) with mineral initiation and maturation during the biomineralisation of radicular dentin. A standardized demineralisation procedure was performed to radicular dentin slices. Samples were remineralised in a PBS-bioactive material system for different periods of time. Assessments of ion exchange, Raman analysis, and energy dispersive X-ray analysis (EDAX) with a scanning electron microscope (SEM) were used to evaluate the remineralisation process. Immunohistochemistry and zymography were performed to analyse NCPs and MMPs expression. SEM evaluation showed that the mineral nucleation and growth occurs, exclusively, on the demineralised radicular dentin surface. Raman analysis of remineralised dentin showed intense peaks at 955 and 1063 cm−1, which can be attributed to carbonate apatite formation. Immunohistochemistry of demineralised samples revealed the presence of DMP1-CT, mainly in intratubular dentin, whereas DSPP in intratubular and intertubular dentin. DMP1-CT and DSPP binding sites control carbonate apatite nucleation and maturation guiding the remineralisation of radicular dentin.

Osteoclast and osteoblast responsive carbonate apatite coatings for biodegradable magnesium alloys

ABSTRACT Corrosion-control coatings which can enhance bone formation and be completely replaced by bone are attractive for biodegradable Mg alloys. Carbonate apatite (CAp) and hydroxyapatite (HAp) coatings were formed on Mg-4 wt% Y-3 wt% rare earth (WE43) alloy as a corrosion-control and bioabsorbable coating in the coating solution with various concentrations of NaHCO3. The incorporation of carbonate group in apatite structure was examined using X-ray diffraction and Fourier transform infrared spectroscopy. Rat osteoclast precursor and MC3T3-E1 osteoblast cells were cultured on the CAp- and HAp-coated WE43 to examine the osteoclastic resorption and the alkaline phosphatase (ALP) activity, respectively. Mg ions in the used medium were quantified to examine the corrosion-control ability. The NaHCO3 addition in the solution resulted in the formation of B-type CAp in which the phosphate group of apatite structure was substituted with the carbonate group. The osteoclastic resorption was observed only for the CAp coatings as the cracking of the coatings and the corrosion of substrate WE43 strongly localized under osteoclast cell bodies. The CAp and HAp coatings significantly enhanced the ALP activity of osteoblasts. The CAp-coated WE43 specimens showed 1/5 smaller amount of Mg ion release than the uncoated WE43 on the first day of culturing osteoblasts. For the subsequent 22 days, the Mg ion release was reduced to 1/2 by the CAp coatings. In the presence of osteoclasts, the CAp coatings showed slightly lower corrosion protectiveness than the HAp coating. It was demonstrated that the CAp coatings can be a bioabsorbable and corrosion-control coating for biodegradable Mg alloys.

Different Molarities and Dissolution-Precipitation Duration Affect the Formation of Carbonate-Apatite Blocks for Bone Graft Material

Objective: To determine diametral tensile strength and water absorption ability of Carbonate-apatite blocks fabricated from gypsum precursors (CaSO4) through a dissolution-precipitation method, with different solution molarities and immersion times. Material and Methods: Thirty-six CaSO4 gypsum specimens with 6 mm diameter; 3 mm height (Group A for diametral tensile strength) and 36 specimens of 6 mm diameter; 3 mm thickness (Group B for water absorption ability) were used. Each group was divided into 4 group treatments of: 1) dissolution-precipitation in solution of 0.5mol / L Na 2 CO 3 + 0.5mol / L Na 3 PO 4 for 48 hours and 72 hours; 1mol / L Na 2 CO 3 + 1mol / L Na 3 PO 4 for 48 hours and 72 hours. The C-Ap blocks were then tested using ATR-FTIR spectrometer to identify the formation of C-Ap functional groups. Furthermore, Group A specimens were tested for diametral tensile strength using Universal Testing Machine, and Group B specimens were tested for water adsorption ability using an analytical balance by measuring initial and final weight after immersion in saline solution at 37 o C for 24 hours . Results: The formation of carbonate-apatite (C-Ap) in groups with solution molarity of 1 mol/L for 48 hours and 72 hours resulted in a lower diametral tensile strength and water absorption ability than the groups with a 0.5 mol/L solution . Conclusion: Solution with different molarities and dissolution-precipitation duration affect the formation of carbonate-apatite blocks.

FABRICATION OF POROUS CARBONATE APATITE BASED ON THE DISSOLUTION-PRECIPITATION OF CALCIUM SULFATE HEMIHYDRATE

Background : Carbonate apatite (C-Ap) has been used as a bone replacement material because it has osteoconductive properties. The pores contained in C-Ap are useful so that cells can diffuse during new bone formation. C alcium sulfate hemihydrate (CaSO 4 .1/2H 2 O) precursor has been used as it possesses Ca 2+ ions, while polymethylmetacrylate (PMMA) is chosen because it is easily burned out at low temperatures. O bjectives: To fabricate porous carbonate apatite based on a calcium sulfate hemihydrate precursor using the dissolution-precipitation method and identify its phases by X-ray diffraction. Methods : The pores were made by crushing polymethyl methacrylate (PMMA) granules and sieving them to sizes of 300–500 µm. Specimens of porous carbonate apatite were prepared from a mixed calcium sulfate hemihydrate precursor with different quantities of porogen: 0 wt% PMMA (n = 60 ), 25 wt% PMMA ( n = 60 ), and 50 wt% PMMA ( n = 60 ). Calcium sulfate hemihydrate containing PMMA was mixed with distilled water at a water: powder ratio of 0.5 ml: 1g. Calcium sulfate dihydrate specimens were placed in an oven at 700˚C for 4 h to burn out the PMMA, resulting in porous calcium sulfate anhydrate. This was then immersed in phosphate mixed solution (Na 3 PO 4 ) and carbonate solution (Na 2 CO 3 ) for 1, 3, and 5 days to obtain carbonate apatite through a precipitation-dissolution process. An X-ray diffraction technique (X-Ray Diffractometer, PANalytical XPert PRO) was used to analyze each group of specimens to identify the phase formation of porous carbonate apatite. Results : The X-ray diffraction pattern showed peaks of carbonate apatite in all specimens with 0, 25, and 50 wt% PMMA in 1, 3, and 5 days of immersion, except in the 0 wt% specimens at 1 day. The carbonate apatite diffraction peaks were at 2 q = 25.9 °, 29.2 °, 32 °, and 34 °. The earliest complete formation of the carbonate apatite phase was identified from the preparation of porous anhydrous CaSO 4 with porogen of 50 wt% PMMA immersed for 1 day. Conclusion : Porous carbonate apatite can be produced from precursors of calcium sulfate hemihydrate and porogen of PMMA via a precipitation-dissolution method.

Effect of silver oxide on hydroxy carbonated apatite formation for simulated body fluid soaked calcium phospho silicate system

Abstract In the present work, we have synthesized the 58SiO2-(38-x) CaO-xAg2O-4P2O5 glasses using sol-gel method and these glasses were treated for 7 days in simulated body fluid (SBF) solution. The structural properties of SBF treated samples were studied using characterization techniques such as X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). Dissolution studies also have been studied for SBF treated samples. The XRD pattern indicates that crystalline nature increases with increase in Ag2O for synthesizing samples. The formed Hydroxy Carbonated Apatite (HCA) particles were identified by XRD and EDX analysis. Dissolution studies confirmed that HCA formation decreased with Ag2O content. Finally, it was confirmed that Ag2O content resists the HCA formation.

Effect of setting atmosphere on apatite cement resorption: An in vitro and in vivo study

ObjectivesThe aim of this present study was to investigate the effect of setting atmosphere on replacement of apatite cement with new bone both in vitro and in vivo. Material and methodsApatite cement consisting of an equimolar mixture of tetracalcium phosphate and anhydrous dicalcium phosphate was mixed with distilled water and allowed to set at 37 °C and 100% relative humidity under 0%, 5%, and 100% CO2 atmospheres. X-Ray diffraction and Fourier Transform Infrared Spectroscopy were employed to confirm the carbonate apatite formation. Micro-CT and histological evaluation was made at 1 and 6 month(s) using twelve 10-week-old specific-pathogen-free male Wistar rats. ResultsB-type carbonate apatite was found when the apatite cement was set under 100% CO2 and 5% CO2. More carbonate apatite was formed in the case of 100% CO2 when compared with 5% CO2, and none was formed under 0% CO2. Interestingly, unreacted tetracalcium phosphate was significant when apatite cement was set under 0% CO2, indicating the formation of Ca-deficient hydroxyapatite. When a bone defect of rat tibia was reconstructed in these conditions of apatite cement and sintered hydroxyapatite, replacement of the apatite cement was confirmed 6 months after implantation, whereas no replacement was observed in the case of sintered hydroxyapatite. The amount of replacement of apatite cement with bone was greater, on the order of 100% CO2 and 5% CO2, followed by 0% CO2. ConclusionThe results obtained in the present study demonstrated that setting atmosphere clearly plays an important role in the replacement of set apatite cement with bone.

Structural changes of hydroxyapatite coating electrophoretically deposited on NiTi shape memory alloy

The surface of the NiTi shape memory alloy was functionalized through the deposition of hydroxyapatite (HAp) coatings using the electrophoretic method (EPD). The electrophoresis carried out at the voltage of 40 V during the time of 120 s did not affect the crystalline structure of the initial HAp powder and, at the same time, ensured obtaining a homogeneous layer without visible cracks or discontinuities. Next, the coatings were subjected to heat treatment at 800 °C for 2 h in vacuum, wherein the applied conditions did not affect the decomposition of the deposited hydroxyapatite. The heat treatment resulted in the formation of carbonate apatite (C-HAp) in the HAp layer and in ceramic particles’ coalescence. Changes in the morphology and roughness of the layer as well as partial decomposition of the NiTi substrate parent phase into Ti2Ni and Ni4Ti3 phases were also observed.

Biomimetic growth and substrate dependent mechanical properties of bone like apatite nucleated on Ti and magnetron sputtered TiO2 nanostructure

This report presents findings on biomimetic growth of hydroxyapatite (HAp) nanocrystals on Ti and sputtered TiO2 substrates. The possibility of TiO2 nanostructure as candidate materials for future biomedical applications has been explored through the comparison of microstructural and mechanical properties of bone like apatite grown on Ti and nano-TiO2 surfaces. Raman spectroscopy and x-ray diffraction studies reveal formation of carbonate apatite with apparent domain size in the nanoscale range. A better interaction at the nano-TiO2/nano-HAp interface due to higher interfacial area could promote the growth of bone like apatite. The crystal phases, crystallinity, and surface morphology of nano-TiO2 are considered as parameters to understand the nucleation and growth of apatite with different mechanical properties at the nanoscale. The methodology of x-ray line profile analysis encompasses deconvolution of merged peaks by preserving broadening due to nanosized HAp aggregates. The Young’s modulus of bone like apatite exhibits crystallographic directional dependence which suggests the presence of elastic anisotropy in bone like apatite. The lattice contraction in the c-direction is associated with the degree of carbonate substitution in the apatite lattice. The role of residual stress is critical for the lattice distortion of HAp deposited at physiological conditions of temperature and pH of human blood plasma. The ion concentration is crucial for the uniformity, crystallinity, and mechanical behaviour of the apatite.

Effect of Time on the Fabrication of Bioresorbable Biphasic Granules of Gypsum-Carbonated Apatite for Paediatric Orthopaedic Application

A carbonated apatite (CO3Ap) has a closer chemical composition to the bone mineral which may be suit as an artificial bone substitute. In this study, the fabrication works of biphasic gypsum-carbonated apatite granules has been done through the phase transformation by carbonation and phosphorization of the gypsum granules. Gypsum also known as calcium sulphate dihydrate (CSD) granules was immersed into the 2 M of carbonate and phosphate salt solution at 50 °C and room temperature in variable time. The effect of time on the fabrication of biphasic granules were studied using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier transform infrared (FTIR). The XRD analysis was done to confirm the formation of gypsum and hydroxyapatite phases in the biphasic granules. The FTIR spectroscopy indicated that the formation of carbonate apatite was formed in these biphasic granules. The cross sectional morphology of the biphasic granules was observed using SEM. The compositional elucidation was quantitatively measured by CHN analysis to obtain the contents of CO3.Based on the results obtained, it is observed that the CSD was successfully transformed into carbonated apatite to form biphasic granules and time had influenced on the fabrication of these biphasic.

Carbonate apatite formation on novel multiphase Cao-SiO2-P2O5-MgO glass-ceramics in TRIS-HCL buffer

The main purpose of the presented article is the preparation of novel glass-ceramics in CaO-SiO2-P2O5-MgO system and evaluation of carbonate apatite formation after soaking in TRIS-HCl buffer solution for 14 days. The investigated samples were prepared via sol-gel method and structure of the obtained samples was studied using XRD, FTIR, SEM, XPS and ICP-AES. XRD of the thermally treated samples showed that the presence of some crystalline phases is depended on the gel composition. FTIR revealed the existence of all characteristic bands for the observed crystalline phases. SEM monitored the presence of particles with different morphology. After soaking in TRIS-HCl solution, FTIR confirmed that carbonate apatite was formed on the soaked surface. The obtained data are in a good agreement with XPS analysis. The change of ions concentrations in TRIS-HCl buffer solution after immersion of the prepared glass-ceramics was recorded by ICP-AES measurements.

Inhibition of precipitation of carbonate apatite by trisodium citrate analysed in base of the formation of chemical complexes in growth solution

Effect of trisodium citrate on the precipitation of carbonate apatite is studied. The experimental series are performed in the solution of artificial urine. The investigations are related to infectious urinary stones formation as carbonate apatite is one of the main components of this kind of stones. To mimic a real infection in urinary tract the aqueous ammonia solution was added to the solution of artificial urine. The spectrophotometric results demonstrate that trisodium citrate increases induction time with respect to carbonate apatite formation and decreases the efficiency of carbonate apatite precipitation. The inhibitory effect of trisodium citrate on the precipitation of carbonate apatite is explained in base of chemical speciation analysis. Such an analysis demonstrates that the inhibitory effect is mainly related with the fact that trisodium citrate binds Ca2+ ions and causes the formation of CaCit− and Ca10(PO4)6CO3 complexes. Trisodium citrate binds Ca2+ ions in the range of pH from 6 to 9.5 for which carbonate apatite is favored to be formed.

Preparation of chitosan/strontium-substituted hydroxyapatite films on titanium and its FTIR characteristics

Chitosan/strontium-substituted hydroxyapatite (CHI/SrHAP) coatings were prepared on titanium substrate by electrochemical deposition technique containing Sr2+, Ca2+, PO4(3-) and Chitosan. The as-prepared coatings were examined by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) tests. The results indicate that the CHI/SrHAP coatings take the morphology of flake-like rather than the needle-like crystal , and the composite coating becomes more compact. The FTIR test indicates that the typical vibration absorption peaks of chitosan (amide I and amide II) emerged, simulated body fluid immersion test proved that the CHI/SrHAP coatings had induced carbonate-apatite formation, indicating that the composite coating possesses excellent biocompatibility. In the electrochemical corrosion testing, that the CHI/SrHAP coatings showed stronger corrosion resistance than pure Ti.

Bioactivity and protein attachment onto bioactive glasses containing silver nanoparticles

There is much interest in silver containing glasses for use in bone replacement owing to the demonstrated antibacterial effect. In this work, 2 and 8 mol % of silver was added during the sol-gel process to the composition of a bioactive glass belonging to CaO-SiO(2 -P(2)O(5) system. The samples were characterized by means of ultraviolet-visible spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques to demonstrate that the silver is embedded into the glass matrix as nanoparticles. Bioactivity test in simulated body fluid proved that the presence of silver in the bioactive glass composition, even in high amount, preserve or even improve the bioactivity of the starting glass, and consequently, leads to the carbonated apatite formation, which is the prerequisite for bioactive materials to bond with living bones. Complementary information proving these findings were delivered by performing X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and XPS measurements. The presence of silver also improves protein binding capability to the bioactive glass surface as demonstrated by cw-electron paramagnetic resonance experiments and XPS measurements.

Apatite formation from simulated body fluid on various phases of TiO 2 thin films prepared by filtered cathodic vacuum arc deposition

Hydroxyl (OH −)-free TiO 2 thin films with amorphous and crystalline phases were deposited onto (100) silicon substrates using filtered cathodic vacuum arc deposition in order to investigate the in vitro apatite formation in simulated body fluid (SBF). The surface morphology, composition and structure of the TiO 2 thin films were characterized. The X-ray photoelectron spectroscopy results confirmed the presence of calcium and phosphorus on all TiO 2 thin film surfaces after immersion in SBF at 37 °C. Fourier transform infra red results showed the presence of carbonated apatite on the surface of these films. Amorphous structured TiO 2 thin film showed poor ability to form apatite on its surface in SBF. Apatite formation was more pronounced on the surfaces of the anatase films in comparison to those of rutile. The carbonated apatite deposition rate increased significantly when the TiO 2 film was illuminated with UV light prior to immersing in the SBF. In particular, the UV-treated anatase and rutile films showed increased rates of carbonated apatite formation on their surfaces in comparison to samples not treated with radiation. The increase in hydrophilicity due to UV treatment appears beneficial for the apatite growth on these surfaces.

Synthesis, in vitro hydroxyapatite forming ability, and cytocompatibility of strontium silicate powders

Phase-pure strontium silicate (SrSiO(3)) powders were synthesized by chemical precipitation method. In vitro bioactivity of the powders were evaluated by examining the hydroxyapatite forming ability on their surface soaking simulated body fluid for various periods. The results showed that SrSiO(3) could induce hydroxy carbonate apatite formation after soaking for 7 days. Both L929 and rabbit bone marrow stromal cells (rMSCs) were used to test the in vitro cytocompatibility of SrSiO(3). L929 culture experiment showed that the ionic product of SrSiO(3) did not exhibit cytotoxicity except at high ion concentrations (Si 3.75 mM and Sr 0.12 mM). Moreover, at certain ion concentrations (Si 1.87-0.12 mM and Sr 0.12-3.75 x 10(-3) mM), the ionic product of SrSiO(3) stimulated the proliferation of rMSCs. All the results indicated that SrSiO(3) might be used as a new bioactive material for bone regeneration applications.