Bioactivity and biodegradability of high temperature sintered 58S ceramics

Bioactive glasses are often considered in bone tissue engineering applications where mechanical strength is essential. As such, bioactive glass scaffolds are often sintered to improve mechanical strength. However, sintering can lead to crystallization, which reduces bioactivity and biodegradability. It has generally been considered that amorphous biomaterials exhibit better bioactivity. However, the in-vitro bioactivity and biodegradability of the sintered 58S made from initial amorphous powder and partially crystalline powder with the same chemical compositions (60SiO₂-36CaO-4P₂O₅ (mol%)) have not been compared before.In this study, 58S bioactive glass (fully amorphous) and glass-ceramic (partially crystallized) powders were synthesized using the sol-gel process, followed by heat-treating at 600 °C for 3 h (calcination). The powders were mixed with carboxymethyl cellulose solution as a binder, shaped in a cylindrical mold, dried, and then sintered at 1100 °C for 5 h. The in-vitro bioactivity and biodegradability of the sintered samples were assessed in simulated body fluid (SBF) for times up to 28 days. The specimens were investigated before and after immersion in SBF using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The In-vitro bioactivity and biodegradability rate of the sintered 58S produced from the glass ceramic powder were higher than that from fully amorphous powder. This study shows that the initial structure after calcination is important and affects the subsequent crystallization during sintering. Therefore, crystallinity and formation of hydroxyapatite after calcination are important controlling mechanisms that can increase the bioactivity and biodegradability rate of sintered 58S.     

生物活性玻璃多孔材料的制备及性能研究

采用溶胶-凝胶法制备生物活性玻璃58S及77S;通过熔融法制备生物活性玻璃45S5,分别向上述3种生物活性玻璃粉体以及它们的混合物中添加一定比例的造孔剂,通过一定的烧结工艺制成具有不同组成的生物活性多孔材料,利用体外实验方法结合DTA,SEM及FTIR等材料显微结构及性能研究手段分析比较了各种多孔材料的显微结构、表面形貌、抗折强度及生物活性.研究表明:58S和45S5混合制备的多孔材料是一种具有良好生物活性和生物矿化特性的生物材料,可用于制备骨缺损填充材料和骨组织工程支架.     

Effect of ZrO2 addition on in-vitro bioactivity and mechanical properties of SiO2–Na2O–CaO–P2O5 bioactive glass-ceramic

Herein, a multicomponent bioactive glass (0Z, 46SiO₂–30CaO–18Na₂O–6P₂O₅, wt.%) is prepared via melting. ZrO₂ is introduced into the bioglass using two different methods, and then three types of glass-ceramic bulks are manufactured using low-cost pressureless sintering. The effect of ZrO₂ addition on the bioactivity and mechanical properties of the bioactive glass-ceramic is assessed. The results indicate that the main crystalline precipitate from the bioactive glass-ceramic is Na₂Ca(Si₂O₆). The crystallisation ability of the 5Z glass-ceramic, bioactive glass-ceramic with ZrO₂ added during melting at high temperature, is reduced because ZrO₂ participated in the reconstruction of the glass network. Further, the ZrO₂ addition led to a low rate of cation release when soaked in simulated body fluid, indicating a decreased bioactivity. At the same time, the 5Y bioactive glass-ceramic, prepared by mixing YSZ particles with 0Z using ball-milling, possesses not only the highest mechanical strength (about twice the strength of 0Z) but also a high bioactivity. This study presents a promising method for the production of excellent bioactive glass-ceramic and a candidate (5Y) for the clinical applications where load bearing is required.     

Two-step sinter-crystallization of K2O–CaO–P2O5–SiO2 (45S5-K) bioactive glass

Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K₂O-26.9CaO-46.1SiO₂-2.6P₂O₅ mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration.     

Fabrication and characterization of bioactive glass (45S5)/titania biocomposites

Bioactive glass (BG) (45S5) has been used successfully as bone-filling material in orthopedic and dental surgery but its lean mechanical strength limits its applications in load-bearing positions. Approaches to strengthen these materials decreased their bioactivity. In order to realize the optimal matching between mechanical and bioactivity properties, bioactive glass (45S5) was reinforced by introducing titania (TiO₂) in anatase form and treated at 1000 °C to form new bioactive glass/titania biocomposites. The prepared biocomposites were assessed by XRD, FT-IR, mechanical properties and SEM. The results verified that the increase of titania percentage to BG powder enhanced gradually the mechanical data of the prepared biocomposites. SEM and FT-IRRS confirmed the presence of a rich bone-like apatite layer post-immersion on the composite surface. It has been found that the new BG/titania biocomposite materials especially those containing high content of titania have high bioactivity properties and compressive strength values comparable to cortical bone. Therefore, these biocomposite materials are promising for medical applications such as bone substitutes especially in load-bearing sites.     

Coupling sol-gel with electrospray deposition: Towards nanotextured bioactive glass coatings

For the first time, the sol-gel method was coupled with electrostatic spray deposition (ESD) to fabricate nanotextured bioactive glass (BG) coatings with a controlled microstructure in a one-pot-process. Three BG compositions belonging to the SiO₂-CaO-P₂O₅ system (S85, S75, and S58) were homogeneously deposited on metallic Ti6Al4V substrates starting from the atomization of precursor solutions. All coatings displayed an amorphous character, as confirmed by XRD. A wide variety of innovative BG morphologies were obtained, tuning the key parameters of ESD, leading from highly porous coral-like to compact reticular-type coatings. The bioactivity, in terms of apatite formation, of as-deposited coatings was tested by immersion in simulated body fluid solution. Textural properties were found to play an important impact in its biological performance. Highly porous ESD-coatings exhibited remarkable bioactivity for S75 and S58 compositions, compared with more compacted ones of equal formulations. S85 composition was found extremely reactive regardless of the coating microstructure.     

Fabrication and in vitro characterization of antibacterial magneto-luminescent core-shell bioactive glass nanoparticles

When nanomaterials with antibacterial properties were sent to the infected area, it was predicted that infection and related complications could be prevented. The nanoparticles can be designed to possess magnetic and luminescence (magneto-luminescent) properties to be effectively targeted and localized at the infection foci without dispersing into the body. Simultaneously, the magneto-luminescent characteristic of particles allows visualization and confirmation of localized particles at the desired area. In this regard, there are no studies on the use of antibacterial magneto-luminescent bioactive glass for orthopedic applications and the treatment of orthopedic device-related infections. In this study, antibacterial magneto-luminescent 58S bioactive glasses were synthesized by the modified Stöber using coupled with a layer-by-layer assembly approach to possess core/shell particle morphology. SPION/Bioactive glass nanoparticles had an average size of 50 nm and displayed superparamagnetic behavior. While the saturation magnetization value (σ_s) of the undoped 58S sample was 25.32 emu/g, that of the co-doped sample (2% Eu, 2% Zn) was 21.74 emu/g; this showed that the doping slightly reduced the magnetization value. Europium (Eu) doping of SPION/Bioactive glass nanoparticles induced characteristic red emission originating from Eu emissions belonging to ⁵D₀–⁷F_J (J = 1–4) transitions and the strongest peak was at 612 nm (electric-dipole transition, ⁵D₀–⁷F₂). Color chromaticity coordinates confirmed emission in the red region. XPS spectrum revealed the existence of Eu and Zn dopant elements in 58S bioactive glass. After soaking characteristic peaks at 31.74° and 45.43° belonging to the hexagonal hydroxyapatite phase were detected in the XRD data, confirming the SEM images. 2% Eu doped SPION/Bioactive glass nanoparticles had the highest osteoblast viability up to 7 days in vitro, while doping the samples with 2% zinc did not yield bone cell viability as high as the Eu doped ones. Importantly, Eu doped SPION/Bioactive glass nanoparticles inhibited gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli) growth up to 48 h in vitro. The results showed that Eu doping of SPION/Bioactive glass nanoparticles increased osteoblast viability and inhibited bacterial growth, while possessing superparamagnetic properties and exhibiting red luminescence.     

Synthesis,characterization and in-vitro bioactivity evaluation of mesoporous Ca10-xFex(PO4)6(OH)2 nanorods-like particles

Multifunctional nanomaterials with superior super-paramagnetic and bioactivity properties with regulated particle morphology can be advantageous for several therapeutic applications. In this investigation, nanorods-like mesoporous particles of Ca_10-xFe_x(PO₄)₆(OH)₂ with varying concentrations of Fe ions were hydrothermally synthesized. In addition to the evaluation of structural and physicochemical properties, magnetic and in-vitro bioactivity attributes were further investigated. Results suggested that with increasing concentration of Fe ions; lattice parameters, crystal size and crystallinity decreased, whereas, surface area, porosity and magnetization of nanorods-like mesoporous particles increased. Nanocomposites exhibited superior super-paramagnetic property. Particles were bioactive and non-resorbable in simulated conditions. Thus, the amalgamation of super-paramagnetism with superior textural and bioactive properties of nanoparticles suggested their high potential for multifunctional applications, including anti-cancer hyperthermia treatment, drug delivery and tissue regeneration.     

A sol-gel based bioactive glass coating on laser textured 316L stainless steel substrate for enhanced biocompatability and anti-corrosion properties

In this study, we have synthesized a new family of bioactive glass (BAG) comprising of SiO₂, Na₂O, CaO, K₂O, P₂O₅ and MgO via sol-gel route. The composition of these oxides has been selected in such a way that the BAG has a coefficient of thermal expansion close to the 316L stainless steel (SS). In vitro test by soaking the BAG in simulated body fluid (SBF) showed good bioactivity due to ion exchange between alkali ions from the BAG and the ions present in the SBF. The 316L SS substrates were textured using laser before application of BAG using sol-gel dip coating. Pull off test showed that the adhesion strength in case of textured and non-textured surfaces were 4.2 MPa and 2.46 MPa, respectively. This implies that texturing of the surface is helpful in increasing the adhesion strength of the coating. The bioactive glass-coated textured surface of 316L SS substrate showed better corrosion resistance in SBF than the bare substrate for which the respective corrosion current densities were 35 nA/cm² and 353 nA/cm², thereby indicating that the single layer sol-gel dip coating of bioactive glass improved the corrosion resistance of the 316L SS implants. The analysis of scanning electron microscopy (SEM) images of the coating after immersion in SBF shows the formation and growth of the apatite layer that will further inhibit the corrosion of the substrate. These results demonstrate the potential of the synthesized BAG as a coating material for 316L SS implants.     

Chitosan effects on glass matrices evaluated by biomaterial. MAS-NMR and biological investigations

Bioactive glass 46S6 and biodegradable therapeutic polymer (Chitosan: CH) have been elaborated to form 46S6-CH composite by freeze-drying process. The kinetics of chemical reactivity and bioactivity at the surface were investigated by using physicochemical techniques, particularly solid-state MAS-NMR. Immortalized cell line used to construct multicellular spheroids was employed as three-dimensional (3D) cell cultures for in vitro studies. Obtained results showed a novel structure of the composite; the chemical treatment (ultrasound, magnetic stirring, freeze drying process and lyophilization) led the bioactive glass particles to be loaded in the chitosan-based materials. ²⁹Si and ³¹P MAS-NMR results showed the emergence of two new species, Q _Si ³ (OH) and Q _Si ⁴ , which are characteristic of the vitreous network dissolution in simulated body fluid (SBF). MAS-NMR also confirmed the formation of amorphous calcium phosphate (ACP) at the surface of the initial 46S6-CH. Three-dimensional (3D) cell cultures highlighted the effect of chitosan, where the cell viability reached up to 78% in 46S6-CH composite and up to 67% in 46S6. The association of (CH) and bioactive glass (BG) matrix promotes a highly significant bioactivity, demonstrating surface bone formation and satisfactory behavior in biological environment.     

Bioactive glass nanoparticles with negative zeta potential

The purpose of this work was to produce and characterize SiO₂–CaO–P₂O₅ bioactive glass nanoparticles with negative zeta potential for possible use in biomedical applications. 63S bioactive glass was obtained using the sol–gel method. X-ray fluorescence (XRF) spectroscopy and dispersive X-ray analysis (EDX) confirmed the preparation of the 63S bioactive glass with 62.17% SiO₂, 28.47% CaO and 9.25% P₂O₅ (in molar percentage). The in vitro apatite forming ability of prepared bioactive glass was evaluated by Fourier transform infrared spectroscopy (FTIR) after immersion in simulated body fluid (SBF). The result showed that high crystalline hydroxyapatite can form on glass particles. By the gas adsorption (BET method), particle specific surface area and theoretical particle size were 223.6 ± 0.5 m²/g and ∼24 nm, respectively. Laser dynamic light scattering (DLS) indicated particles were mostly agglomerated and had an average diameter between 100 and 500 nm. Finally, using laser Doppler electrophoresis (LDE) the zeta potential of bioactive glass nanoparticles suspended in physiological saline was determined. The zeta potential was negative for acidic, neutral and basic pH values and was −16.18 ± 1.8 mV at pH 7.4. In summary, the sol–gel derived nanoparticles revealed in vitro bioactivity in SBF and had a negative zeta potential in physiological saline solution. This negative surface charge is due to the amount and kind of the ions in glass structure and according to the literature, promotes cell attachment and facilitates osteogenesis. The nanometric particle size, bioactivity and negative zeta potential make this material a possible candidate for bone tissue engineering.     

Bioactive glass based scaffolds incorporating gelatin/manganese doped mesoporous bioactive glass nanoparticle coating

We investigated the bioactivity and cytocompatibility of 45S5 bioactive glass (BG) based scaffolds coated with a composite layer formed by gelatin and manganese doped mesoporous bioactive glass nanoparticles (Mn-MBGNs). The scaffolds were prepared using the foam replica method, and they were further coated with Mn-MBGNs/gelatin via dip coating. The synthesized scaffolds were characterized in relation to morphology, porosity, mechanical stability, bioactivity and cell biology behavior using osteoblast-like (MG-63) cells. The scaffolds were highly porous with interconnected porosity, and a suitable pore structure was maintained even after the Mn-MBGNs/gelatin coating. Energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of Mn-MBGNs in the coatings. Moreover, the presence of gelatin was confirmed by Fourier transform infrared spectroscopy (FTIR). The coated scaffolds exhibited in-vitro bioactivity in simulated body fluid comparable to that of uncoated BG scaffolds. Finally, Mn-MBGNs/gelatin coated scaffolds were shown to be non-cytotoxic to MG-63 cells. Hence, the results presented here confirm that the novel Mn containing scaffolds can be considered in the field of biologically active ion releasing scaffolds for bone tissue engineering applications.     

Sodium is not essential for high bioactivity of glasses

This study aims to demonstrate that excellent bioactivity of glass can be achieved without the presence of an alkali metal component in glass composition. In vitro bioactivity of two sodium-free glasses based on the quaternary system SiO₂-P₂O₅-CaO-CaF₂ with 0 and 4.5 mol% CaF₂ content was investigated and compared with the sodium-containing glasses with equivalent amount of CaF₂. The formation of apatite after immersion in Tris buffer was followed by Fourier-transform infrared spectroscopy, X-ray diffraction, ³¹P and ¹⁹F solid-state MAS-NMR. The dissolution study was completed by ion release measurements in Tris buffer. The results show that sodium-free bioactive glasses formed apatite at 3 h of immersion in Tris buffer, which is as fast as the corresponding sodium-containing composition. This signifies that sodium is not an essential component in bioactive glasses and it is possible to make equally degradable bioactive glasses with or without sodium. The results presented here also emphasize the central role of the glass compositions design which is based on understanding of structural role of components and/or predicting the network connectivity of glasses.     

Effects of Sr and Mg dopants on biological and mechanical properties of SiO2–CaO–P2O5 bioactive glass

In the present study, the effects of Sr and Mg were investigated on mechanical and biological properties of 58S bioactive glass (BG). SiO₂-P₂O₅-CaO BG with different contents of Sr and Mg were synthesized via the sol-gel method and immersed in simulated body fluid (SBF) for several days to explore their biocompatibility. Precise analyses of the BG using X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy showed that the Mg-doped BG containing 8 wt % MgO possessed better biocompatibility. It was also found that mechanical properties of the BG could be improved by increasing the amounts of MgO and SrO. Both 5Sr-BG and 8Mg-BG samples did not exhibit any cytotoxicity while showing high alkaline phosphatase activity in comparison with control specimens. However, the Sr-doped BG sample including 5 wt % SrO demonstrated enhanced bioactivity and biocompatibility.     

Characterization of bioactive glass-coated carbon nanotubes prepared by solgel process

Due to its excellent bioactivity, bioactive glass (BG) is suitable for use as bone graft substitutes in biomedical applications. In this study, carbon nanotubes (CNT-COOH) served as templates for depositing bioactive glass based on 60SiO₂–36CaO–4P₂O₅ wt.% were synthesized via the solgel process. The BG and BG/CNT-COOH composites were treated at 300, 500, 700, and 900°C; their properties were also examined by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The experimental results showed that BG/CNT-COOH composites treated at 500 and 700°C were amorphous and contained silicate nanocrystals. By altering precursor concentration, bioactive glass of various thicknesses was successfully solgel coated on CNT-COOH. Immersion of the BG/CNT-COOH composites in simulated body fluid solution and MG-63 cell culture assessment showed the 500°C treated BG/CNT-COOH exhibits excellent bioactivity.     

Carbon sphere influence on textural properties and bioactivity of mesoporous bioactive glass/hydroxyapatite nanocomposite

Mesoporous bioactive glass/hydroxyapatite nanocomposite (MBG-HA) synthesis was conducted through evaporation-induced self-assembly (EISA) method followed by in situ carbonization, with non-ionic block co-polymer as mesoporous template and glucose-derived carbon sphere as co-template. The mixture of different carbon sphere contents into a glass network in the CaO–SiO₂–P₂O₅ system tailored the structural, morphological, and textural properties of MBG–HAs. Based on the preliminary results, the carbon sphere content and textural and structural parameters of as synthesized MBG–HAs showed a negative trend. The MBG–HA 0.5 with additional low carbon sphere content, showed a high surface area and large pore volume. The inclusion of HA nanoparticles inside the channels strongly influenced the high carbon sphere content of the MBG–HA8 mesoporous structure. For in vitro bioactivity tests, MBG–HAs with higher textural parameters possessed a faster apatite phase formation kinetics following the sequence MBG–HA0.5>MBG–HA2>MBG–HA5>MBG–HA8.     

Apatite formation on melt-derived bioactive glass powder based on SiO2-CaO-Na2O-P2O5 system

The higher melting temperature and longer soaking time during conventional glass melting route promoted the search for alternative in developing new bioactive glass (BG) composition with improved in fabrication temperature and melting time. The current project involved fabrication of new BG compositions based on SiO₂-CaO-Na₂O-P₂O₅ system via melt derived route. It was confirmed that all bioactive glass composition can be melted at temperature lower than 1400 °C. Formation of Si-O-Si (tetrahedral) functional group highlighted that silicate based glass was established as detected by Fourier transform infrared spectroscope (FTIR). BG bioactivity was performed by incubating the BG powder in Tris-buffer solution (pH 8) for 7, 14 and 21 days. In vitro test confirmed the apatite formation on the bioactive glass surface upon soaking in Tris-buffer solution with characteristic of carbonate group (C-O) and P-O band noticed from FTIR and present of crystalline peak observed in X-ray diffraction (XRD). Morphology of apatite formation on BG surface was observed using scanning electron microscope (SEM).     

Structural behavior and in vitro bioactivity evaluation of hydroxyapatite-like bioactive glass based on the SiO2-CaO-P2O5 system

Silicate bioglass is of great importance in bone engineering because of its excellent bioactivity and osteogenic effects. In this study, hydroxyapatite-like bioactive glass based on the xSiO₂-CaO-P₂O₅ (x = 30, 45, 60 and 90 mol.%, Ca/P = 1.67) system was synthesized by the sol-gel method, and the corresponding structural evolution, apatite-forming ability and cytotoxicity were systematically investigated. The results suggest that both a higher heat treatment temperature and a lower SiO₂ content increase the crystallinity tendency of the bioglass, and the samples become obviously compact as the SiO₂ amount increases from 30 to 90 mol.%. Compared with the samples with higher SiO₂ content, the 30Si sample shows more remarkable internal connected mesoporous structures, with a higher specific surface area up to 129.12 m²/g, exhibiting excellent hydroxyapatite formation in simulated body fluid. Moreover, no obvious inhibitory effect was presented on human periodontal ligament cells (hPDLCs) for any of the silicate glass samples.     

等离子体喷涂生物陶瓷涂层

综合介绍了文献及中国科学院上海硅酸盐研究所在等离子体喷涂生物涂层方面的近期研究进展。羟基磷灰石涂层已在临床上获得应用,但使用效果仍然受其较低的结合强度和结晶度所制约。通过优化喷涂工艺和制备羟基磷灰石基复合涂层,可有效提高羟基磷灰石涂层的结合强度和结晶度。此外,为了获得综合性能优良的植入体材料,制备了多种新型的生物活性陶瓷涂层。纳米氧化钛涂层经合适工艺的后处理可具有良好的生物活性,由于其与钛合金基体有较高的结合强度,在体液环境下具有高稳定性和生物相容性,使纳米氧化钛涂层成为一种具有发展前景的植入体涂层候选材料。新型生物活性硅酸钙涂层具有良好的生物活性,与骨组织能形成有效结合。此外,对这些新型涂层的生物活性机制也做了必要的描述。     

3D printing of bone substitute implants using calcium phosphate and bioactive glasses

Customized implants for bone replacement are a great help for a surgeon to remodel maxillofacial or craniofacial defects in an esthetical way, and to significantly reduce operation times. The hypothesis of this study was that a composite of β-tricalcium phosphate (β-TCP) and a bioactive glass similar to the 45S5 Henchglass^® is suitable to manufacture customized implants via 3D-printing process. The composite was chosen because of the bioresorption properties of the β-TCP, its capability to react as bone cement, and because of the adjustability of the bioactive glass from inert to bioresorbable. Customized implants were manufactured using the 3D-printing technique. The four point bending strength of the printed specimens was 14.9 MPa after sintering. XRD analysis revealed the occurrence of two other phases, CaNaPO₄ and CaSiO₃, both biocompatible and with the potential of biodegradation. We conclude that it is possible to print tailored bone substitute implants using a bioactive TCP/glass composite. The glass is not involved as reactive substance in the printing process. This offers the opportunity to alter the glass composition and therefore to vary the composition of the implant.