Hydroxycarbonate Apatite Layer Research Articles

Rapidly derived equimolar Ca: P phasic bioactive glass infused flexible gelatin multi-functional scaffolds – A promising tissue engineering

The study aims to design and fabricate an ultra-easier multi-functional biomedical polymeric scaffold loaded with unique equimolar Ca:P phasic bioactive glass material (BG). Gelatin (G) – 45S5 bioactive glass (BG) scaffolds were synthesized via a simple laboratory refrigerator with higher biocompatibility and cytocompatibility. The results proved that BG has enhanced bio-mineralization of the scaffolds and results support that the G: BG (1:2) ratio is the more appropriate composition. Brunauer-Emmett-Teller (BET) study confirms the higher surface area for pure Gelatin and G: BG (1:2). Scanning Electron Microscopic images display the precipitation of hydroxycarbonate apatite layer over the scaffolds on immersing it in simulated body fluid. Alkaline phosphate activity proved that G: BG (1:2) scaffold could induce mitogenesis in MG-63 osteoblast cells, thus helping in hard tissue regeneration. Sirius red collagen deposition showed that higher content bioactive glass incorporated Gelatin polymeric scaffold G: BG (1:2) could induce rapid collagen secretion of NIH 3T3 fibroblast cell line that could help in soft tissue regeneration and earlier wound healing. The scaffolds were also tested for cell viability using NIH 3T3 fibroblast cell lines and MG 63 osteoblastic cell lines through methyl thiazolyl tetrazolium (MTT) assay. Thus, the study shows a scaffold of appropriate composition G: BG (1:2) can be a multifunctional material to regenerate hard and soft tissues.

Polyvinylpyrrolidone Nanofibers Incorporating Mesoporous Bioactive Glass for Bone Tissue Engineering.

Composite biomaterials that combine osteoconductive and osteoinductive properties are a promising approach for bone tissue engineering (BTE) since they stimulate osteogenesis while mimicking extracellular matrix (ECM) morphology. In this context, the aim of the present research was to produce polyvinylpyrrolidone (PVP) nanofibers containing mesoporous bioactive glass (MBG) 80S15 nanoparticles. These composite materials were produced by the electrospinning technique. Design of experiments (DOE) was used to estimate the optimal electrospinning parameters to reduce average fiber diameter. The polymeric matrices were thermally crosslinked under different conditions, and the fibers' morphology was studied using scanning electron microscopy (SEM). Evaluation of the mechanical properties of nanofibrous mats revealed a dependence on thermal crosslinking parameters and on the presence of MBG 80S15 particles inside the polymeric fibers. Degradation tests indicated that the presence of MBG led to a faster degradation of nanofibrous mats and to a higher swelling capacity. The assessment of in vitro bioactivity in simulated body fluid (SBF) was performed using MBG pellets and PVP/MBG (1:1) composites to assess if the bioactive properties of MBG 80S15 were kept when it was incorporated into PVP nanofibers. FTIR and XRD analysis along with SEM-EDS results indicated that a hydroxy-carbonate apatite (HCA) layer formed on the surface of MBG pellets and nanofibrous webs after soaking in SBF over different time periods. In general, the materials revealed no cytotoxic effects on the Saos-2 cell line. The overall results for the materials produced show the potential of the composites to be used in BTE.

Hydroxyapatite-Bioceramic/Expanded Perlite Hybrid Composites Coating on Ti6Al4V by Hydrothermal Method and in vitro Behavior.

This study was aimed to coat a hybrid bioceramic composite onto Ti6Al4V by using hydrothermal method. The Hybrid bioceramic composite for coating was prepared by reinforcing different rations of expanded perlite (EP) and 5 wt.% chitosan into synthesized Hydroxyapatite (HA). Coating was performed at 1800°C for 12 hours. The coated specimens were gradually subjected to a sintering at 6000°C for 1 hour. For in vitro analysis, the specimens were kept in Ringer's solution for 1, 10, and 25 days. All specimens were examined by SEM, EDX, FTIR, and surface roughness analyses for characterizing. It was concluded that as the reinforcement ratio increased, there was an increase in coating thickness and surface roughness. The optimum reinforcement ratio for expanded perlite can be 10 wt.% (A3-B3). With increasing ratio of calcium (Ca) and phosphate (P) (Ca/P), the surface becomes more active in body fluid and then observed the formation of the hydroxycarbonate apatite (HCA) layer. As the waiting time increased, there was an increase in the formation of an apatite structure.

A comparative study of bone bioactivity and osteogenic potential of different bioceramics in methacrylated collagen hydrogels.

Biomimetic scaffolds composed of bioactive ceramic-based materials incorporated within a polymeric framework have shown immense promise for use in bone tissue engineering (BTE) applications. However, studies on direct comparison of the efficacy of different bioceramics on bone bioactivity and osteogenic differentiation are lacking. Herein, we performed an in vitro direct comparison of three different bioceramics-Bioglass 45S5 (BG), Laponite XLG (LAP), and β-Tricalcium Phosphate (TCP)-on the physical properties and bone bioactivity of methacrylated collagen (CMA) hydrogels (10% w/w bioceramic:CMA). In addition, human MSCs (hMSCs) were encapsulated in bioceramic-laden CMA hydrogels and the effect of different bioceramics on osteogenic differentiation of hMSCs was investigated in two different culture medium-osteoconductive (without dexamethasone [DEX]) and osteoinductive (with DEX). Results showed that the stability of CMA hydrogels was maintained upon bioceramic addition. Compression testing revealed that BG incorporation significantly decreased (p < 0.05) the modulus of photochemically crosslinked CMA hydrogels. Incubation of TCP-CMA and LAP-CMA hydrogels in simulated body fluid showed deposition of hydroxycarbonate apatite layer on the surface indicating that these hydrogels may be more bone bioactive than BG-CMA and CMA only hydrogels. Cell cytoskeleton staining results showed greater cell spreading in TCP-CMA hydrogels. Furthermore, TCP incorporation significantly increased alkaline phosphatase activity (ALP; p < 0.05) in hMSCs. Together, these results indicate that TCP has superior osteogenic potential compared with BG and LAP and hence should be considered as a bioceramic of preferred choice for use in the biomimetic design of cell-laden hydrogels for BTE applications.

Characterization and Evaluation of Composite Biomaterial Bioactive Glass-Polylactic Acid for Bone Tissue Engineering Applications.

The limitations associated with the clinical use of autographs and allografts are driving efforts to develop relevant and applicable biomaterial substitutes. In this research, 3D porous scaffolds composed of bioactive glass (BG) obtained through the sol-gel technique and polylactic acid (PLA) synthesized via lactic acid (LA) ring-opening polymerization were prepared by the gel-pressing technique. Two different weight compositions were evaluated, namely, BG70-PLA30 and BG30-PLA70. The structure and morphology of the resulting scaffolds were analysed by FTIR, XRD, SEM, and under ASTM F1635 standard characterizations. The results confirmed that BG promotes the formation of a hydroxy-carbonated apatite (HAp) layer on composites when immersed in simulated body fluid (SBF). Biodegradability evaluations were carried out according to the ISO 10993-13:2010 standard. In addition, electrochemical evaluations were performed in both Hank’s and SBF solutions at 37 °C in order to analyse the degradation of the material. This evaluation allowed us to observe that both samples showed an activation mechanism in the early stages followed by pseudo-passivation due to physical bioactive glass characteristics, suggesting an improvement in the formation of the HAp nucleation. The described composites showed excellent resistance to degradation and outstanding suitability for bone tissue engineering applications.

Deposition of bioactive glass coatings based on a novel composition containing strontium and magnesium

In this work a novel bioactive glass composition was used to deposit coatings by means of plasma spraying. Different coatings were manufactured and optimized by varying the processing parameters and were studied by X-ray diffraction and scanning electron microscopy. Moreover, the bioactivity was assessed by in vitro tests in Simulated Body Fluid solution.The coatings displayed the typical microstructure of atmospheric plasma sprayed coatings, that is a coating made up by the stacking of melted splats, with different thicknesses, porosities and crystalline phases depending on the spraying parameters used. The work showed that all the coatings are denser and with less porosity than those observed for plasma sprayed coatings of the well-known 45S5 bioactive glass, with similar particle size deposited under the same spraying conditions. The in vitro tests demonstrated the bioactive aptitude of all the coatings, on whose surface an hydroxycarbonate apatite layer formed after 7 days of soaking.

Bioactive glass-ceramic synthesis using nano and normal silica: a comparative study

Bioactive glass-ceramics are very promising materials for soft and hard tissue repair due to their high biocompatibility and bioactivity. The bioactive glass-ceramics (NSGC) containing (38-X)normal-SiO2-28CaO-18Al2O3-12CaF2-4P2O5-Xnano-SiO2 (mol%) (where X = 0, 19, and 38) system were synthesized using melt-quench method. The thermal behaviors were assessed by differential thermal analysis (DTA). The glass transition temperature (Tg) was high in the case of a mixture of 19 mol% normal silica and 19 mol% nano-silica. However, it was less with 38 mol%, either normal silica-containing or nano-silica-containing samples. As the quantity of nano-silica increases, the crystallization peak temperature (Tp) was increased. The X-ray diffractometer (XRD) result showed that the fluorapatite (FA) (Ca5(PO4)3F), mullite (M) (3Al2O3.2SiO2), and wollastonite (W) (CaSiO3) had the main crystalline phases for all the three batches. The crystals were needle and irregular shaped in all sintered specimens, as shown in a scanning electron microscope (SEM). They also showed the indications of surface cracks in case of high sintering temperature. Energy-dispersive X-ray spectroscopy (EDX) analysis showed the specimen’s elemental composition before and after the immersion in synthetic body fluid (SBF) solution. Fourier transform infrared (FTIR) spectra showed the characteristic peaks for Si–O–Si, Si–O–Ca, C–O stretching, O–H bending vibration, carbonate, and phosphate groups. The transmission electron microscope (TEM) images confirmed that the nanoparticles (2.58–8.15 nm) were present in the prepared glass-ceramics. The hydroxycarbonate apatite (HCA) layer was developed after 28 days of immersing in the modified SBF. The addition of nano-SiO2 in the specimens showed an increase in Vickers hardness, density, and acid-base resistivity.

Influence of random and designed porosities on 3D printed tricalcium phosphate-bioactive glass scaffolds.

Calcium phosphate (CaP)-based ceramics are a popular choice for bone-graft applications due to their compositional similarities with bone. Similarly, Bioactive glass (BG) is also common for bone tissue engineering applications due to its excellent biocompatibility and bone binding ability. We report tricalcium phosphate (TCP)-BG (45S5 BG) composite scaffolds using conventional processing and binder jetting-based 3D printing (3DP) technique. We hypothesize that BG's addition in TCP will enhance densification via liquid phase sintering and improve mechanical properties. Further, BG addition to TCP should modulate the dissolution kinetics in vitro. This work's scientific objective is to understand the influence of random vs. designed porosity in TCP-BG ceramics towards variations in compressive strength and in vitro biocompatibility. Our findings indicate that a 5 wt % BG in TCP composite shows a compressive strength of 26.7 ± 2.7 MPa for random porosity structures having a total porosity of ~47.9%. The same composition in a designed porosity structure shows a compressive strength of 21.3 ± 2.9 MPa, having a total porosity of ~54.1%. Scaffolds are also tested for their dissolution kinetics and in vitro bone cell materials interaction, where TCP-BG compositions show favorable bone cell materials interactions. The addition of BG enhances a flaky hydroxycarbonate apatite (HCA) layer in 8 weeks in vitro. Our research shows that the porous TCP- BG scaffolds, fabricated via binder jetting method with enhanced mechanical properties and dissolution properties can be utilized in bone graft applications.

Bioactive glasses and electrospun composites that release cobalt to stimulate the HIF pathway for wound healing applications

BackgroundBioactive glasses are traditionally associated with bonding to bone through a hydroxycarbonate apatite (HCA) surface layer but the release of active ions is more important for bone regeneration. They are now being used to deliver ions for soft tissue applications, particularly wound healing. Cobalt is known to simulate hypoxia and provoke angiogenesis. The aim here was to develop new bioactive glass compositions designed to be scaffold materials to locally deliver pro-angiogenic cobalt ions, at a controlled rate, without forming an HCA layer, for wound healing applications.MethodsNew melt-derived bioactive glass compositions were designed that had the same network connectivity (mean number of bridging covalent bonds between silica tetrahedra), and therefore similar biodegradation rate, as the original 45S5 Bioglass. The amount of magnesium and cobalt in the glass was varied, with the aim of reducing or removing calcium and phosphate from the compositions. Electrospun poly(ε-caprolactone)/bioactive glass composites were also produced. Glasses were tested for ion release in dissolution studies and their influence on Hypoxia-Inducible Factor 1-alpha (HIF-1α) and expression of Vascular Endothelial Growth Factor (VEGF) from fibroblast cells was investigated.ResultsDissolution tests showed the silica rich layer differed depending on the amount of MgO in the glass, which influenced the delivery of cobalt. The electrospun composites delivered a more sustained ion release relative to glass particles alone. Exposing fibroblasts to conditioned media from these composites did not cause a detrimental effect on metabolic activity but glasses containing cobalt did stabilise HIF-1α and provoked a significantly higher expression of VEGF (not seen in Co-free controls).ConclusionsThe composite fibres containing new bioactive glass compositions delivered cobalt ions at a sustained rate, which could be mediated by the magnesium content of the glass. The dissolution products stabilised HIF-1α and provoked a significantly higher expression of VEGF, suggesting the composites activated the HIF pathway to stimulate angiogenesis.

Effect of feedstock and plasma gun on the microstructure and bioactivity of plasma sprayed bioactive glass coatings

Plasma-sprayed 45S5 bioactive glass coatings were manufactured using two types of powder feedstocks (commercial and lab-made 45S5 glass) and two plasma torches (single and triple cathode) to analyse their influence on the microstructure and bioactivity of the coatings. Besides, the volatilisation of glass oxides such as Na2O and P2O5 during the deposition was studied. All coatings were microstructurally characterised by scanning electron microscopy, X-ray diffraction and X-ray dispersive energy analysis. Moreover, the bioactivity of the sprayed coatings was studied by immersing the coatings in Simulated Body Fluid until 14 days.The coatings obtained using the triple cathode torch showed similar thickness, less total porosity and greater microstructural homogeneity than the coating deposited with the single cathode torch. X-ray dispersive energy analysis revealed lower amounts of sodium and phosphorus at the surrounding of the lamellae, due to its volatilisation during the formation of the coatings. The volatilisation of these elements varied depending on the type of feedstock and plasma jet enthalpy. Concerning the bioactivity of the coatings, all of them have developed a hydroxycarbonate apatite layer on their surface.

In vitro study of bioactive glass coatings obtained by atmospheric plasma spraying

This research has addressed a complete study of the bioactivity of bioactive glass coatings obtained by atmospheric plasma spraying. The coatings have been characterized in terms of microstructure, adhesion, crystalline phases and bioactivity. Hydroxycarbonate apatite formation was also monitored following a standard protocol and the in vitro cell response was evaluated by human osteoblast-like cells (MG-63 cells) incubation.The obtained coatings shown a microstructure typical of glass coatings. A simulated body fluid test proved that coatings are capable of developing a surface layer of hydroxycarbonate apatite whereas the appearance of this phase takes place at a longer time than that observed for the powder feedstock. Cell-culture test showed multidirectional growth of MG-63 cells which promoted good contact between cells and the surface of the coating. This study has confirmed a positive effect of the coatings in terms of surface bioactivity and, more interestingly, it has proven an adequate cell-material interaction on the coating surface.

Influence of textural characteristics on biomineralization behavior of mesoporous SiO2-P2O5-CaO bioactive glass and glass-ceramics

The present work demonstrates the novel synthesis of multi-components, ternary SiO2-P2O5-CaO mesoporous bioactive glass (MBG) and bioactive glass-ceramics (MBGC) through acid assisted sol-gel route by using Pluronic, P123 as structure directing agent followed by evaporation induced self-assembly (EISA) process. As synthesized samples has been characterized by different analytical techniques before and after immersion in physiological solution to unravel the structural, morphological and textural properties and correlate with biomineralization process. The different structural species of the pristine MBG/MBGC samples have been confirmed by high resolution x-ray diffraction (HR-XRD) and Fourier transforms infra-red (FTIR) spectroscopy studies. Bright field transmission electron microscopy (BF TEM) study reveal a wormhole like structures in the pristine samples, which is a typical characteristic of mesoporous samples. Moreover, the obtained samples exhibit superior textural characteristics like enhanced surface area and mesoporosity revealed by nitrogen adsorption-desorption technique. The presence of various anionic species in the pristine samples has been revealed by magic angle spinning nuclear magnetic resonance (MAS NMR) technique. The textural characteristics and the biomineralization behavior of pristine and soaked samples have been studied by varying the calcium and phosphorous contents with respect to silica. The in-vitro bioactivity analysis performed over three different samples in simulated body fluid (SBF) for different immersion duration leads to the formation of hydroxy carbonated apatite (HCA). The formed HCA layer is confirmed by analytical techniques such as HR-XRD and FTIR spectroscopy, which indicates the nano sized HCA crystals are impregnated in the amorphous matrix. Furthermore, significant modifications on the surface of samples have been illustrated by FE-SEM micrographs before and after SBF immersion, which specifies growth of thin-HCA layer. The mesostructured glassy samples showed an excellent cell viability response without toxicity up to the concentration of 100 mg ml−1. Additionally, cell-culture studies like cell-proliferation and cell viability test were also performed on the MBG and MBGC to show the material-cell interaction and it was found to be in good agreement within the desired range.

Cation-doped bioactive ceramics: In vitro bioactivity and effect against bacteria of the oral cavity

We synthesized, using a solid-state reaction, bioactive ceramics of the SiO2−CaO−Na2O−P2O5 system doped with up to 3 mol% of Ag, Mg, Sr, Zn, and Ga, elements that were used as therapeutic agents. On evaluating the in vitro bioactivity of our crystalline samples using the ICG-TC04 method (so far only tested for glassy materials), we observed that those ceramics containing up to 0.5 mol% dopant exhibited hydroxycarbonate apatite (HCA) layer formation on their surfaces in a 24-h in vitro assay — the same time observed for Bioglass®, the material considered to be “gold standard” in terms of bioactivity. The antibacterial activity of these ceramics was confirmed against 23 oral bacteria, related to caries and endodontic infections, by employing three different methods. For the agar dilution method, using a concentration range of 0.5–24 mg/mL, various bacteria were found to be susceptible to the materials — the lowest minimum inhibitory concentration (MIC) values were achieved for the doped samples, particularly those containing Ag. In the biofilm-forming capability assay, we did not observe any viable cells after 24 h incubation. Finally, the direct contact assay confirmed that all the samples showed a stronger antibacterial effect, promoting a significant reduction in the number of viable cells after only 10 min in contact with the microorganisms. This result indicates that the tested materials have an intrinsic antibacterial activity, and do not need to be doped, except for some specific bacteria or depending on how they will be used (extracts or in direct contact). Therefore, besides easy production and in vitro bioactivity, all tested materials demonstrated a considerable antibacterial effect against representative bacteria, stimulating future studies involving their application as topical endodontic disinfectants or in dental prophylaxis procedures.

Microstructural and in vitro characterization of 45S5 bioactive glass coatings deposited by solution precursor plasma spraying (SPPS)

The present work focused on the development of bioactive glass coatings employing Solution Precursor Plasma Spraying. Precursors of SiO2, CaO, Na2O and P2O5 were mixed in distilled water to prepare concentrated solutions with a composition close to the 45S5 bioactive glass.Solutions were rheologically characterized to assess their stability with time and deposited onto AISI type 304 stainless steel to develop coatings under different parameters related to the thermal spraying technique. The effect of these parameters on coatings microstructure was studied by scanning electron microscopy. Coatings were also analysed by X–ray diffraction and scratch test to complete the microstructural characterization. Moreover, coatings bioactivity was evaluated by immersing them in Simulated Body Fluid.The study showed that using short spraying distances and low argon flow rates, gave rise to the typical microstructure derived from liquid feedstocks whereas some crystallization associated to the long spray distance used occurred. Scratch test revealed that the resulting coating possessed good mechanical properties when compared with similar coatings obtained by other plasma spraying techniques. Moreover, the obtained coating could develop an hydroxycarbonate apatite layer when in contact with Simulated Body Fluid as demonstrated by scanning electron microscopy, X–ray diffraction and Fourier transform infrared spectroscopy.

Cerium-containing mesoporous bioactive glasses: Material characterization, in vitro bioactivity, biocompatibility and cytotoxicity evaluation

Abstract Bone defects due to trauma or diseases causing bone loss have led to an increased demand for new materials that have applications in therapies for bone pathologies. Mesoporous bioactive glasses (MBGs), based on 70SiO2-(26-x)CaO 4P2O5-xCeO2 (x = 0, 1 and 5 mol % for MBGS, MBGS1Ce and MBGS5Ce) were synthesized by evaporation-induced self-assembly (EISA) method. Ceria was selected due to its antimicrobial and antioxidant properties and positive impact on cells differentiation and mineralization. The pore size values of 2.8 nm confirmed the mesoporosity of the obtained bio-glasses. The biocompatibility tests on mouse fibroblast cells (NCTC clone L929) using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) activity assays revealed no cytotoxicity of Cerium containing MBGs. Formation of a hydroxycarbonate apatite (HCA) layer on MBGs surface, e.g. bioactivity of BMGs, was confirmed by XRD, FTIR, SEM and Raman Spectroscopy while presence of Ce3+/Ce4+ in the glasses before body simulated fluid (SBF) immersion was determined by XPS, UV–Vis measurements. The obtained results show that investigated MBGs are potential materials for applications in bone regeneration.

The influence of cobalt incorporation and cobalt precursor selection on the structure and bioactivity of sol–gel-derived bioactive glass

Cobalt (Co) is a potential therapeutic ion used to enhance angiogenesis through a stabilizing effect on hypoxia-inducible factor 1 alpha (HIF-1α), and its incorporation into the structure of bioactive glass is a promising strategy to enable sustained local delivery of Co to a wound site or bone defect. Here Co-releasing bioactive glasses were obtained through the sol–gel method, comparing cobalt nitrate and cobalt chloride as precursors. The effect of using different Co precursors on the sol–gel synthesis and in the obtained bioactive glass structure, chemical composition, morphology, dissolution behaviour, hydroxycarbonate apatite (HCA) layer formation was investigated. When the chloride salt was used as Co precursor, evidence of crystalline cobalt (II, III) oxide (Co3O4) phase formation was found, along with the presence of Co3+ species as evaluated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), whereas an amorphous glass containing mainly Co2+ species was obtained when the nitrate salt was the Co source. The presence of a crystalline phase decreased the surface area and pore volume of the final glass, consequently reducing the Co-release rate. Evidence of HCA layer formation after immersion in simulated body fluid (SBF) was still found when different precursors were used, although the rate of formation was reduced by the presence of Co. Therefore, this study showed that Co incorporation and the proper selection of the precursor could affect the final material structure, and properties, and should be considered when designing new bioactive glass compositions for tissue engineering applications.

Structural, physico-mechanical and in-vitro bioactivity studies on SiO2–CaO–P2O5–SrO–Al2O3 bioactive glasses

Strontium based bioactive glasses have shown a better biocompatibility than calcia based bioactive glasses. In this report, we have shown that the bioactivity is found to be even more when we incorporate Al2O3 upto 1.5 mol% in SiO2–CaO–P2O5–SrO bioactive glass. We have studied the structural, physico-mechanical and bioactive properties in these glasses with varying alumina concentration from 0.5 to 2.5 mol%. The bioactivity of the glasses is evaluated by in vitro test in simulated body fluid (SBF). The formation of hydroxy carbonated apatite layer (HCA) on the surface of glasses after immersion in SBF is identified by the XRD, FTIR and SEM. The substitution of Al2O3 for SrO in these glasses demonstrates a significant enhancement in compressive strength and elastic modulus. However cytotoxicity and cell viability assessed using human osteosarcoma U2-OS cell lines show the growth of the cells without causing any significant loss of viability and cell death upto 1.5 mol% addition of Al2O3. Osteosarcoma cells grow on the surface of bioglasses which make them biocompatible and fit for use in clinical trials.

Contrasting In Vitro Apatite Growth from Bioactive Glass Surfaces with that of Spontaneous Precipitation.

Body-fluid-exposed bioactive glasses (BGs) integrate with living tissues due to the formation of a biomimetic surface layer of calcium hydroxy-carbonate apatite (HCA) with a close composition to bone mineral. Vast efforts have been spent to understand the mechanisms underlying in vitro apatite mineralization, as either formed by direct precipitation from supersaturated solutions, or from BG substrates in a simulated body fluid (SBF). Formally, these two scenarios are distinct and have hitherto been discussed as such. Herein, we contrast them and identify several shared features. We monitored the formation of amorphous calcium phosphate (ACP) and its crystallization into HCA from a NaO–CaO–SiO–PO glass exposed to SBF for variable periods out to 28 days. The HCA growth was assessed semi-quantitatively by Fourier transform infrared spectroscopy and powder X-ray diffraction, with the evolution of the relative apatite content for increasing SBF-exposure periods evaluated against trends in Ca and P concentrations in the accompanying solutions. This revealed a sigmoidal apatite growth behavior, well-known to apply to spontaneously precipitated apatite. The results are discussed in relation to the prevailing mechanism proposed for in vitro HCA formation from silicate-based BGs, where we highlight largely simultaneous growth processes of ACP and HCA.

Tensile Properties, Biodegradability and Bioactivity of Thermoplastic Starch (TPS)/ Bioglass Composites for Bone Tissue Engineering

Composite fabricated from the combination of biodegradable polymer and bioactive filler is beneficial for bone tissue engineering if the biomaterial can perform similar characteristics of the natural inorganic-organic structures of bone. In this study, we have investigated the thermoplastic starch (TPS)/sol-gel derived bioglass composite as new biomaterial for bone tissue engineering. The composites were produced using selected TPS/bioglass mass ratio of 100/0, 95/5, 90/10, 85/15 and 80/20 by a combination of solvent casting and salt leaching techniques. Tensile test results showed the addition of bioglass increased the tensile strength and Young’s modulus, but reduced the elongation at break of the samples. The modulus of all samples were higher than the requirement for cancellous bone (10-20 MPa). The SEM imaging showed the presence of porous structure on the surface of all samples. XRD results confirmed the formation of hydroxycarbonate apatite (HCA) layer on the surface of bioglass containing samples; indicating the occurrence of surface reactions when the samples were immersed in Simulated Body Fluid (SBF). Furthermore, the presence of P-O stretch band in FTIR spectrum between 1000 and 1150 cm-1 and Si-O-Si stretch band at 1000 cm-1 also proved the bioactivity of TPS/bioglass composite. The in vitro biodegradability analysis shows the biodegradability of TPS/bioglass composite decreases with increasing mass ratio of the bioglass.

Preparation and in vitro investigation on bioactivity of magnesia-contained bioactive glasses

Mg plays an important role in the human skeletal system as it stimulates the bone formation and reduces bone resorption. Magnesium has been substituted into SiO2–Na2O–CaO–P2O5 bioactive glass. In the present work, the bioactive glasses were designed to enhance bioactivity. Bioactivity of these glasses was assessed by the immersion of the samples in simulated body fluid (SBF) for different time periods. The formation of hydroxy carbonate apatite (HCA) layer was confirmed by scanning electron microscopy, X-ray diffractometry, and FTIR spectrometry which had shown the HCA layer formation and growth. The formation of HCA layer was found to increase on the surface of the SBF immersed bioactive glasses with increasing magnesia contents in the glass. In vitro cell culture investigations such as viability, proliferation, and cell attachment were studied using human osteosarcoma U2-OS cell lines. The in vitro results of new magnesium containing bioactive glasses had shown improved bioactivity as well as better biocompatibility.