Preparation,characterization and in vitro biological response of simultaneous co-substitution of Zr+4/Sr+2 58S bioactive glass powder

In the present study, structure of zirconium-containing bioactive glass (58S-BG (Zr-BG)) with optimal fixed Zr content (5 mol.%) was modified by incorporation of strontium (Sr). These Zr and Sr-containing BGs (ZS-BGs) were synthesized by sol-gel method and substitution of Ca with modifier ions (Sr content = 0, 3, 6, 9, and 12 mol.%). The results obtained from characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDS) techniques from surface of all the ZS-BGs revealed formation of hydroxyapatite (HA) after 7 days of immersion in the simulated body fluid (SBF) solution. Evaluation of changes in the SBF solution, by monitoring pH variations and ions? concentration, was in agreement with the results of morphological and structural investigations. The in-vitro biological function of synthesized BGs was studied through (MTT) assay and alkaline phosphatase (ALP) activity analysis. The results showed that all the specimens significantly stimulated proliferation and viability of MC3T3 osteoblast-like cells. Furthermore, antibacterial studies confirmed less resistance of methicillin-resistant Staphylococcus aureus (MRSA) bacteria against ZS-BGs. Eventually, the results of in-vitro bio-analysis were clarified and confirmed by two cell staining techniques of Live/Dead and Dapi/Actin. This confirmation was achieved by observing the increased quantity of live cells and their nuclei as well as the decreased number of dead cells after co-culturing with all ZS-BGs.     

Characterization,in vitro bioactivity and biological studies of sol-gel-derived TiO2 substituted 58S bioactive glass

Bioactive glasses (BGs) have been used for bone formation and bone repair processes in recent years. This study investigated the titanium substitution effect on 58S BGs (Ti-BGs) 60SiO₂-(36 − X)CaO-4P₂O₅-XTiO₂ (X = 0, 3, and 5 mol.%) prepared by the sol-gel technique, and the main goal was to find the optimum amount of titanium in Ti-BGs. Synthesized BGs, which were investigated after immersion in simulated body fluid (SBF), were tested by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy. Moreover alkaline phosphate (ALP) activity, 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and antibacterial studies were employed to investigate the biological properties of Ti-BGs. According to the FTIR and XRD test results, hydroxyapatite (HA) formation on Ti-BGs surfaces was confirmed. Meanwhile, the presence of 5 mol.% compared to 3 mol.% increased the HA grain distribution and their size on the Ti-BGs surface. Additionally, MTT and ALP results confirmed that the optimal amount of titanium substitution in BG was 5 mol.%. Since 5 mol.% Ti incorporated BG (BG-5) had the highest biocompatibility level, antibacterial properties, maximum cell proliferation, and ALP activity among the synthesized Ti-BGs, it is presented as the best candidate for further in vivo investigations.     

Synthesis, characterization and in vitro bioactivity of magnesium-doped sol-gel glass and glass-ceramics

Bioactive glass and glass-ceramics in the system CaO-MgO-SiO₂-P₂O₅ have been prepared by the sol-gel and high temperature sintering techniques. The obtained samples were characterized by thermogravimetric and differential thermal analysis (TG/DTA), N₂-adsorption measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In vitro bioactivity tests were also conducted in simulated body fluid (SBF). The studies of crystallization kinetics under non-isothermal conditions showed the activation energy for crystallization to be 381 kJ/mol and the crystallization mechanism gradually changed from three-dimension growth to two-dimension crystallization with the increase of heating rate. Sintering temperature had great influence on the samples texture and structure. In addition, the apatite-formation on glass and glass-ceramics was confirmed by in vitro tests, and crystallization decreased the samples bioactivity.     

The effect of magnesium content on in vitro bioactivity,biological behavior and antibacterial activity of sol–gel derived 58S bioactive glass

Bioactive glasses (BGs) have a great potential for bone replacement and regeneration in bone tissue engineering applications. In this research, first, sol–gel derived magnesium substituted 58?S BGs (MBGs) series composed of 60SiO₂–4P₂O₅-(36-x) CaO- xMgO, (x = 0; 1; 3; 5; 8 and 10?mol.%) were synthesized and stabilized at 700?°C to eliminate the nitrates and prevent the crystallization of MBGs. MgO was substituted for CaO in the BG formula up to 10?mol% and the effect of Mg concentration on in vitro bioactivity and cellular properties of the MBGs were investigated by immersing them in simulated body fluid (SBF) followed by structural characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The effects Mg on proliferation and differentiation of osteoblastic MC3T3-E1 cells were also evaluated by 3-(4,5dimethylthiazol-2-yl)??2,5-diphenyltetrazolium bromide (MTT) and alkaline phosphate (ALP) activity.Results revealed that magnesium-substituted 58?S BG with 5?mol% MgO (BG-5) had the highest formation rate of hydroxyapatite (HA) while substitution of 8?mol% and10 mol% MgO (BG-8 and BG-10) lowered the bioactivity. MTT and ALP results confirmed that the substitution of the MgO up to 5?mol% increased both proliferation and differentiation of MC3T3-E1 cells, while more substitution had a negative effect and resulted in a decrease of proliferation and differentiation in BG-8 and BG-10. The result of antibacterial test showed that MBGs exhibited antibacterial effect against methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Taken together, results suggest that, among all the synthesized MBGs, sample BG-5 is a promising candidate as multifunctional biomaterial for bone tissue engineering with maximum cell proliferation and ALP activity, good bioactivity and high antibacterial efficiency against MRSA bacteria. Eventually, the BG-5 is suggested to be used in segmental defects in rat model in vivo.     

In vitro assessment of degradation and bioactivity of robocast bioactive glass scaffolds in simulated body fluid

In this study porous three-dimensional scaffolds of borate (13-93B3) bioactive glass were prepared by robocasting and in vitro degradation and bioactivity was evaluated. Grid like scaffolds with interconnected pores was assembled using robotic deposition technique which is a direct ink writing method. After binder burnout, the constructs were sintered for 1 h at 560 °C to produce scaffolds (porosity≈60%) consisting of dense glass struts (300±20 μm in diameter) and interconnected pores of width 580±20 μm. Hydroxyapatite formation on borate bioactive glass scaffolds was investigated in simulated body fluid (SBF) using three different scaffold/SBF (S/S) ratios (1, 2 and 10 mg/ml) at 37 °C. When immersed in SBF, degradation rate of the scaffolds and conversion to a calcium phosphate material showed a strong dependence to the S/S ratio. At high solid concentration (10 mg/ml) surface of the glass scaffolds converted to the calcium rich amorphous calcium phosphate after 30 days. At lower solid concentrations (2 and 1 mg/ml) an amorphous calcium phosphate layer formation was observed followed by the conversion to hydroxyapatite.     

Fabrication and characterization of bioactive glass/hydroxyapatite nanocomposite foam by gelcasting method

Bioceramic foams have been applied for drug releasing agents, cell loading, and widely for hard tissue scaffold. The aim of this study was fabrication and characterization of nanostructure bioceramic composite foam (BCF) consisting of hydroxyapatite (HA) and bioactive glass (BG) via gelcasting method for applications in tissue engineering. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis techniques were utilized in order to evaluate respectively, phase composition, dimension, morphology, and interconnectivity of pores, and particle size of synthesized HA, BG, and BCF. The results showed that fabrication of the BCF with a particle size in the range 20-42 nm and pore size in the range 100-250 μm was successfully performed. The maximum values of compressive strength and elastic modulus of the BCF were found to be about 1.95 MPa and 204 MPa, respectively, related to a sample sintered at 900 °C for 4 h. The mean values of the true (total) and apparent (interconnected) porosity were calculated in the range 86-91% and 60-71%, respectively. It seems that the measured properties make the BCF a good candidate for tissue engineering applications, preferentially in drug delivery, cell loading, and other nonloading applications.     

Freeze-cast composite scaffolds prepared from sol-gel derived 58S bioactive glass and polycaprolactone

This work deals with the preparation of freeze-cast scaffolds using sol-gel derived 58S bioactive glass and a hypoeutectic naphthalene-camphor mixture as the starting powder and freezing vehicle, respectively. After the freeze-casting step, samples were air sintered at 1250?°C for 2?h, which led to the crystallization of 58S. The obtained scaffolds were subsequently infiltrated with poly(ε-caprolactone) (PCL), a biodegradable polymer with potential application for bone tissue repair. The prepared materials were examined by helium pycnometry, laser granulometry, scanning electron microscopy (SEM), Archimedes tests, X-ray microtomography (micro-CT), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption, X-ray diffraction (XRD), and uniaxial compression tests. Samples cytotoxicity was evaluated by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction (MTT) and LIVE/DEAD assays. Their biocompatibility was also examined after soaking in a simulated body fluid (SBF) solution at 37?°C for up to 14 days. It was observed that the infiltration of PCL into the 58S scaffolds greatly increased their mechanical stability. Moreover, it was shown that these composites displayed a high cell viability (above 70%), which reveals that they did not interfere in the production of osteoblast cells. A hydroxyapatite coating was observed on the samples surface upon soaking in SBF, reinforcing that they are biocompatible materials. As far as we know, this is the first time that freeze-cast scaffolds were obtained using sol-gel derived 58S particles and a naphthalene-camphor mixture. Besides, as the infiltration of PCL into freeze-cast bioactive glass scaffolds improved their mechanical stability without impairing their bioactivity, this is a promising approach to prepare samples for load-bearing applications in bone tissue engineering.     

Processing and in vitro bioactivity of high-strength 45S5 glass-ceramic scaffolds for bone regeneration

In this paper, the compressive strength and in vitro bioactivity of sintered 45S5 bioactive glass scaffolds produced by powder technology and polymer foaming were investigated. The sintering temperature of scaffolds was 975 °C. The characterization of scaffolds before immersion in SBF was performed by scanning electron microscopy (SEM) and microtomography (μCT). The scaffolds were also tested for compression, and their density and porosity were measured. After immersion, the samples were observed through SEM and analyzed using EDS, X-ray diffraction (XRD), and infrared spectroscopy (FT-IR). Mass variation was also estimated. The glass-ceramic scaffolds showed a 61.44±3.13% interconnected porosity and an average compressive strength of 13.78±2.43 MPa. They also showed the formation of a hydroxyapatite layer after seven days of immersion in SBF, demonstrating that partial crystallization during sintering did not suppress their bioactivity.     

Studies on novel bioactive glasses and bioactive glass-nano-HAp composites suitable for coating on metallic implants

A series of novel zinc oxide (ZnO) containing bioactive glass compositions in SiO₂-Na₂O-CaO-P₂O₅ system and composite with hydroxyapatite (HAp) nano-particles were developed and applied as coating on Ti-6Al-4V substrates. The bioactive glasses and their composites were also processed to yield dense scaffolds, porous scaffolds and porous bone filler materials. The coating materials and the coatings were characterized and evaluated by different in vitro techniques to establish their superior mechanical properties. The cytotoxicity test of the coating material, porous and dense scaffolds and coated specimens showed non-cytotoxicity, biocompatibility and promising in vitro bioactivity for all tested samples. The dissolution behaviour studies of the bioactive glasses and the composites in simulated body fluid showed promising in vitro release pattern and bioactivity for all tested samples. Addition of nanosized HAp improves mechanical properties of the bioactive glass coating without affecting the in vitro bioactivity.     

Potassium-based composition for a bioactive glass

The increasing need for biomedical devices, required to face dysfunctions of natural tissues and organs caused by traumatic events, diseases and simple ageing, has drawn attention onto new materials, that could be able to positively interact with the human body. Among them, Bioglass^® is firmly diffused in medical practice, thanks to its high bioactivity. In particular, due to its brittleness, it is mainly applied as a coating onto tougher bionert substrates; nevertheless, its bioactivity may be altered by the crystallization phenomena that could be involved by its processing. With the aim of reducing the tendency to crystallize, a new glass composition, inspired by the 45S5 Bioglass^®, was formulated by substituting the sodium oxide with potassium oxide. A parallel characterization of the new glass and the 45S5 Bioglass^® was carried out in order to define the effect of the potassium oxide on the thermal behaviour, mechanical properties and bioactivity. The results proved that the thermo-mechanical properties, as well as the in vitro response of the two glasses were comparable; however, preliminary tests to produce glass coatings by enamelling evidenced a higher stability of the new glass that, unlike the 45S5 Bioglass^®, did not crystallize during processing.     

Fabrication of corrosion resistant, bioactive and antibacterial silver substituted hydroxyapatite/titania composite coating on Cp Ti

The present work is aimed at developing a bioactive, corrosion resistant and anti bacterial nanostructured silver substituted hydroxyapatite/titania (AgHA/TiO₂) composite coating in a single step on commercially pure titanium (Cp Ti) by plasma electrolytic processing (PEP) technique. For this purpose 2.5 wt% silver substituted hydroxyapatite (AgHA) nanoparticles were prepared by microwave processing technique and were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) methods. The as-synthesized AgHA particles with particle length ranging from 60 to 70 nm and width ranging from 15 to 20 nm were used for the subsequent development of coating on Cp Ti. The PEP treated Cp Ti showed both titania and AgHA in its coating and exhibited an improved corrosion resistance in 7.4 pH simulated body fluid (SBF) and 4.5 pH osteoclast bioresorbable conditions compared to untreated Cp Ti. The in vitro bioactivity test conducted under Kokubo SBF conditions indicated an enhanced apatite forming ability of PEP treated Cp Ti surface compared to that of the untreated Cp Ti. The Kirby-Bauer disc diffusion method or antibiotic sensitivity test conducted with the test organisms of Escherichia coli (E. coli) for 24 h showed a significant zone of inhibition for PEP treated Cp Ti compared to untreated Cp Ti.     

Synthesis and characterization of spray pyrolyzed mesoporous bioactive glass

Mesoporous bioactive glasses (MBGs) have recently been applied as important bone implant materials due to their high reactive surface areas and superior bioactivities. Various processes have been developed to fabricate MBGs. Among them, the sol–gel process is one of most popular. However, sol–gel has the drawbacks of discontinuous processing and long processing time, making it unsuitable for mass production. This study demonstrates a successful synthesis of MBGs using a spray pyrolysis (SP) method to overcome these problems. The bioactivities of the SP synthesized MBGs are correlated with the main SP processing parameter of calcination temperatures and their structures. Comparisons of the surface areas and bioactivities for the MBG particles prepared from the sol–gel and the SP process are included. Finally, the MBG formation mechanism using SP is proposed.     

Influence of silver on the structure,dielectric and antibacterial effect of silver doped bioglass-ceramic nanoparticles

We present the structural, dielectric, biocompatibility and antibacterial properties of nano-sized calcium phosphosilicate bioglass ceramics doped with 0, 2, 4 and 6 mol% Ag₂O. Sol-gel processes were chosen to synthesize the silver embedded nanosized glass ceramic particles. All samples were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, UV–visible and high resolution transmission electron microscopy (HR-TEM). The glass-ceramic nature of the samples is confirmed by XRD analysis. The FTIR spectra reveal the probable stretching and bending vibration modes of silicate and phosphate groups. UV–visible absorption spectra reveal the silver embedment as Ag⁺/Ag° form in the glass matrix. Nano-size of the glass ceramics and silver nanoparticle embedment in glass matrix are confirmed by HR-TEM analysis. Dielectric spectra of samples reveal non-Debye relaxation processes. The dielectric constant of samples initially decreased and then increased with Ag₂O content. The antibacterial activities of these bioceramics were tested with different bacteria using an agar well diffusion method. Silver doped samples show good antibacterial effects without compromising the formation of hydroxyapatites. The dielectric constant of the bioglass ceramics is correlated to their antibacterial performance, with low dielectric constants giving higher antibacterial activity.     

A comparative physico-chemical study of bioactive glass and bone-derived hydroxyapatite

This study aimed at comparing the physico-chemical properties of bioactive glass and bone-derived hydroxyapatite (HA). 63S bioglass particles were obtained by sol-gel process and HA samples were derived from bovine bone. The chemical composition and the crystalline structure of both bioceramics were evaluated. Then the zeta potential in physiological saline and at different pH values was determined. It was found that the negativity of zeta potential for 63S bioglass is higher than that of bone-derived HA. The exothermal behavior through the hydration process was evaluated by isothermal microcalorimetry. The results showed that the librated heat during bioactive glass hydration process and its rate are almost ten times higher than HA. It could be related to different hydration mechanisms of bioglass and HA. However, for both bioglass and HA, this value is in the safe range and cannot be harmful for the adjacent tissues in the body.     

Synthesis and characterization of bioactive forsterite nanopowder

Forsterite ceramic is a new bioceramic with good biocompatibility. However, the degradation rate of forsterite ceramic is extremely low, and the apatite-formation ability is also poor. On the other hand, nanostructured bioceramics are expected to have better bioactivity than coarser crystals. The aim of this work was preparation, characterization and bioactivity evaluation of forsterite nanopowder. Forsterite nanopowder was synthesized by the sol–gel process. Bioactivity evaluation was preformed by immersing the forsterite powder in the simulated body fluid (SBF) and apatite formation on the surface of the immersed forsterite nanopowders was investigated. Results showed the particle size of pure forsterite was 25–45 nm. During immersion in SBF, the dissolution rate of the forsterite nanopowder was higher than conventional forsterite powders and apatite was formed after soaking for 14 days. Our study indicated that forsterite nanopowder unlike micron-sized forsterite possessed apatite-formation ability and might be used for preparation of new biomaterials.     

Marine biological waste as a source of hydroxyapatite for bone tissue engineering applications

The demand for bone graft substitutes for orthopedics and dentistry is constantly growing due to the increase of ageing-related diseases. Synthetic hydroxyapatite (HA) is largely used as a bone graft material thanks to its biocompatibility, osteointegration, osteoconductive and osteoinductive properties and similarity to biological apatite, the main mineral component of bones and teeth. Biogenic apatite has gained attention due to its peculiar intrinsic characteristics: multi-doped ion composition and micro- and nano-scale architecture make natural-derived HA particularly promising for biomedical applications.At the same time, the growing interest in green materials is pushing towards the use of more sustainable biomaterials precursors, including re-use materials: marine waste, such as mollusk-shells, shellfish carapaces, cuttlefish bone, and fishbone have become widely studied sources of biogenic HA. Indeed, they are rich in calcium carbonate (CaCO₃), which can be converted into HA by environmentally sustainable processes. This allows the transformation of waste into valuable materials, while paying attention to the issues of sustainability and circular economy.In this review, we listed and discussed the methods to produce HA starting from shell-derived CaCO₃, describing all the steps and synthesis routes proposed for the conversion procedure, with a special focus on the different species of marine shells used. We discussed the use of HA alone or in combination with other materials (natural and synthetic polymers), used to enhance the mechanical and biological properties.We summarized the types of devices obtained by marine-derived HA, including nanorods, particulates and scaffolds and we described their in vitro and in vivo behavior.The up-to-date literature was summarized in tables with a special focus on the in vitro and in vivo biological evaluation of such materials.In conclusion, composite biomaterials based on marine-derived biogenic HA are reported as potential candidates for synthetic bone substitutes highlighting their potential, limitations and future perspectives.     

Properties of calcium phosphates ceramic composites derived from natural materials

In this study, ceramics containing mixed phases of hydroxyapatite/beta-tricalcium phosphate (HA/β-TCP) were fabricated by a solid-state reaction technique. The HA powder was synthesized from cockle shells while the β-TCP powder was synthesized from egg shells. Pure HA and β-TCP fine powders were successfully obtained. The HA and β-TCP were mixed and subjected to a thermal treatment up to 1100 °C. To form the mixed phase ceramics, the resulting powders were sintered at 1350 °C. Effects of HA concentration on the properties of the studied ceramic were investigated. X-ray diffraction analysis revealed that all samples presented multiphase of calcium phosphate compounds. Average grain size of the ceramics decreased with the HA additive content. The 75 wt% HA ceramic showed the maximum hardness value (5.5 GPa) which is high when compared with many calcium phosphate ceramics. In vitro bioactivity test indicated that apatite forming increased with the HA additive content. To increase antibacterial activity, selected ceramics were coated with AgNO₃. Antibacterial test suggested that an Ag compound coating on the ceramics could improve the antibacterial ability of the studied ceramics. In addition, the antibacterial ability for the Ag coated ceramics depended on the porosity of the ceramics.     

Influence of concentration of hydroxyapatite surface modifier agent on bioactive composite characteristics

The characterization of chitosan – hydroxyapatite (CH – HAp) composite sponges prepared via freeze-drying methodology is reported in this study. Stearic acid (SA), added as a surface modifier of the HAp nanoparticles, induced changes in the TG/DTG results, particle size distribution and particle morphology. Composite sponges prepared with SA coated HAp demonstrated enhanced biocompatibility and structural properties, as compared to the composites prepared with uncoated HAp. SA coating modified the morphology of the composite, promoting a better dispersion of HAp particles within the composite sponges, and better homogeneity of the polymeric cover with HAp particles. The viability of the composites for cell culture applications was analyzed, and the results suggest that the sponges are biocompatible. Therefore, SA proved to be a good candidate for surface coating of HAp nanoparticles prevent agglomerations, and could be used effectively in the preparation of biocompatible composite sponges with chitosan.