Bioactive Glass Composites Research Articles

Impact of 13-93 bio-glass inclusion on the machinability, in-vitro degradation, and biological behavior of Y-TZP-based bioceramic composite

Nowadays, bio-ceramic composite material is demanded in the biomedical industry due to its remarkable biological and mechanical properties. But, the shaping of such material challenges the manufacturer. In this work, bioceramic composite materials, having general weight composition [(100-x) (3Y-TZP) – x (13-93 BG)] where x = 0 to 25 wt%, has been prepared, and their machinability in terms of MRR (material removal rate) and SR (surface roughness) is studied as a function of BG composition and machining temperature. It is found that MRR decreases with increasing the concentration of bioactive glass (BG) while it increases with increasing the machining temperature. The SR is found in the opposite trend. The MRR, SR, and material removal mechanics (MRM) are also confirmed by the HR-SEM and AFM (atomic force microscopy) analysis. The effect of BG addition on the physical, mechanical, in-vitro degradation, and cell culture behaviour of the composite materials are also evaluated. The relative density and mechanical properties, such as flexural and compressive strength, are found to increase up to 10 wt% of BG content; afterward, it decreases. The hardness is increased with BG addition in 3Y-TZP ceramics. The in-vitro degradation indicates the dissolution and apatite layer formation after 35 days of immersion in simulated body fluid (SBF) solution. The cell proliferation is examined by MTT assay over MG-63 cell lines. The cell proliferation ability of the composite is increased with increasing the BG concentration and found a maximum of up to 25 wt% of BG. Overall, the best findings were obtained with 10 wt% BG contained 3Y-TZP ceramic composite sintered at 1250 °C. The relative density, flexural strength, and compressive strength are about 98.34%, 397.9 MPa, and 488.7 MPa, respectively. Based on the obtained results, it may be recommended that 10 wt% BG concentration in 3Y-TZP bioceramic composite is the most suitable and potential material for biomedical application.

Fabrication and characterization of cobalt- and copper-doped mesoporous borate bioactive glasses for potential applications in tissue engineering

Developing novel compositions of bioactive glasses (BGs) is key for accelerating tissue repair and regeneration. In this work, we developed a series of cobalt (Co)- and copper (Cu)-doped mesoporous bioactive glasses (MBGs) based on borate 13-93B3 composition using nitrate precursors. We took benefit from data science algorithms to predict and assess the physico-chemical and biological properties of the samples. The results showed that the presence of the dopants (Co and Cu) in the MBGs could change the glass transition temperature (Tg) (from 773 to 539 °C), the zeta potential (from -12 to -43 mV), and surface area (from 54 to 194 m2/g). However, the presence of 2.5 mol% of dopants in the composition led to just a slight decrease in their bioactivity. In vitro biocompatibility assays confirmed that all the glass samples were biocompatible. Furthermore, the doped MBGs exhibited potent antibacterial activity against both Gram-positive and Gram-negative bacteria. In addition, these glasses could induce the mobility of human umbilical vein endothelial cells (HUVECs) and enhance new blood vessel formation in ovo. According to the obtained data, it can be stated that this type of doped borate MBGs held great promise in tissue engineering applications.

Investigation the Structural Influences of Silver Oxide Addition in the Bioactive Phosphate Glasses

This research investigates the impact of varying concentrations of silver oxide on the structure and morphology of phosphate bioactive glass (PBG). PBGs are gaining popularity as a potential replacement for traditional silicate glasses in biomedical applications due to their adjustable chemical resistance and exceptional bioactivity. Upon examination of the scanning electron microscope of the composites without Ag2O, it was observed that the grains tended to merge together, and the surface particles appeared to be larger than those in composites with Ag2O at concentrations of 0.25, 0.5, and 0.75 wt%. The study found that the diffraction pattern of phosphate bioactive glass composites sintered without Ag2O showed the presence of Strontium di-phosphate and Calcium di-phosphate. The XRD pattern of these composites without Ag2O revealed specific planes that corresponded to both types of di-phosphate. However, when Ag2O was added, a new cubic phase was detected, and the intensity of the calcium and strontium diphosphate increased with higher Ag2O content. The XRD pattern of the composites with Ag2O displayed specific planes that corresponded to Ag2O. In other words, the absence of Ag2O in the composite material led to larger particle sizes and less distinct boundaries between grains. In addition, it has been found that, as the concentration of Ag2O increased from 0 to 0.25, 0.5, and 0.75 wt%, the average crystallite size decreased from 36.2 to 31.7, 31.0, and 32.8 nm, respectively. These results suggest that the addition of Ag2O can effectively reduce the average crystallite size of the composite materials. Also, as the concentration of Ag2O increased from 0 g to 0.5 wt% within the composite material, the average lattice strain increased from 3.41·10-3 to 4.40·10-3. In simpler terms, adding Ag2O to the composite material resulted in a slight increase in the average lattice strain.

Isothermal crystallization behavior of poly-ether-ether-ketone/bioactive glass composites and its correlation with scaffold warpage in laser powder bed fusion process

The preparation of poly-ether-ether-ketone/bioactive glass (PEEK/BG) composite scaffolds using laser powder bed fusion (LPBF) has enormous clinical potential. However, ensuring the desired accuracy and reproducibility of composite scaffolds during the LPBF process remains a significant challenge. Therefore, a thorough understanding of the relationship between the crystallization behaviors and the scaffold warpage during the LPBF process is crucial. To address this challenge, this study systematically investigates the isothermal crystallization kinetics of PEEK/BG composites and their relationship with scaffold warpage. The results reveal that the crystallization rates of pure PEEK and PEEK/BG composites decrease as isothermal crystallization temperature increases. Additionally, BG significantly suppresses the isothermal crystallization kinetics of PEEK, resulting in a 250% increase in the half-crystallization time (t1/2) of PEEK/25 wt% BG at 316 °C relative to pure PEEK. Extrapolating the t1/2 using the Hoffman-Lauritzen model can obtain the optimal powder bed temperature (Tb) for each powder in LPBF. Pure PEEK and PEEK/25 wt% BG Diamond scaffolds are printed at the respective inferred Tb (330 °C and 323 °C) and their warpage degrees are compared to that of the pure PEEK scaffold printed at 323 °C. The results demonstrate that raising Tb from 323 °C to 330 °C and adding 25 wt% BG are both effective methods to reduce the scaffold warpage by slowing down the crystallization kinetics of PEEK, resulting in reductions of 57.8% and 50.6% in warpage degree respectively. Furthermore, the incorporation of BG successfully tackles the challenge of simultaneously preventing warpage and secondary sintering in pure PEEK printing. Overall, this study offers a deep comprehension regarding the relationship between crystallization kinetics and scaffold warpage, which is crucial for achieving the reproducibility with desired accuracy of LPBF-printed biological scaffolds for clinical applications.

Clustering of fluoride and phosphate ions in bioactive glass from computer simulation.

In order to understand the nature of ionic clustering in bioactive glass compositions, computer simulation was used to model four different compositions of bioactive glass with various amounts of flouride and phosphate. Fluoride ions were chemically bonded only to sodium and calcium, creating regions rich in fluoride and modifiers, and fluoride clustering was seen to be present in all compositions. The majority of phosphate groups are present as orthophosphate and phosphate clustering is also seen, and shown to be stronger in compositions with a lower phosphate content. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'.

Impact of substituting K2O for Na2O on physico-chemical properties and in vitro bioactivity of bioactive glass S53P4

The impact of substituting K2O for Na2O (0–100%) on the physico-chemical and bioactive properties of bioactive glass S53P4 was studied. The thermal properties were evaluated using differential thermal analysis and high-temperature microscopy. Ion release kinetics was measured in static and dynamic TRIS-buffer and SBF using inductively coupled plasma optical emission spectroscopy. Substituting K2O for Na2O showed a mixed-alkali effect (MAE) for the thermal properties with a minimum value for the glass containing around 20% K2O. The hot-working range increased with the potassium content. The glass with 66% of Na2O replaced with K2O exhibited MAE in static TRIS by giving the biggest pH change and ion release at 24 h. The same glass showed the lowest pH and Si species release in dynamic SBF at the longest dissolution time, 72 h. Both single-alkali glasses showed higher in vitro bioactivity in dynamic SBF. The results provide tools for tailoring new bioactive glass compositions with desired properties.

Effect of B/Si molar ratio on the structure and properties of borosilicate bioactive glasses assessed using molecular dynamics simulations

Due to the improvement and innovation of theoretical methods and the increasing enhancement of high performance computing, computer simulations provide a new method and strategy for optimizing complex composition of novel bioactive glass. In this work, molecular dynamics simulations were used to analyze the effect of B/Si molar ratio on the structure of borosilicate bioactive glass (BBG) and to investigate the effect of structural alterations on its ions release and biological effects. Structural descriptor a theoretical structural descriptor that estimates the overall strength of the glass network (F net) was calculated from the simulated data, and the linear relationships of F net with B and Mg releasing rate in deionized water and simulated body fluid were built. In vitro mineralization experiments showed that all three BBGs could generate hydroxyapatite and the release of some network modifier ions such as Mg would be regulated by the B/Si ratio. In vitro cellular experiments revealed that the BBG sample with a composition of 1.25B (6Na2O–8K2O–8MgO–22CaO–22.5B2O3–2P2O5–31.5SiO2) promoted the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells, and significantly enhanced the expression of osteogenesis-related genes such as osteopontin, which might be related to the release of Mg at an early stage.

Unraveling the relationship between the structural features and solubility properties in Sr-containing bioactive glasses

Understanding the effect of glass network structure on the solubility properties of bioactive glasses is fundamental for designing new compositions with tailored biological functions and applications. This paper bridged the composition-structure-property relationship utilizing experimental measurements and molecular dynamics simulations. The Sr atom reorganized the network structures through a partial transformation of tetrahedral to trigonal boron units and the change of the ratio of bridged oxygen/non-bridged oxygen, which modified the glass structures at longer lengths scales, such as through changing the ring size distribution. Our results demonstrated that the evolution of solubility properties can be linked to the atomic structure change in short- and medium-range ordering. The structure-property relationship can be used to design and tune bioactive glass composition with specific properties.

Effect of solution treatment of AZ91 alloy on microstructure, mechanical properties and corrosion behavior of friction stir back extruded AZ91/bioactive glass composite

In the present study, we investigated the effects of solution treatment and friction stir back extrusion on the microstructure, mechanical properties, and in-vitro corrosion behavior of the AZ91/64SiO2–31CaO–5P2O5 composite. The findings demonstrate that the reinforcing phase of bioactive glass in the AZ91 matrix exhibits a gradient distribution, resulting in grain refinement in the zone near the surface of the composite wire. The fabrication of the AZ91-3 vol% bioactive glass composite through friction stir back extrusion, utilizing a rotational speed of 1200 rpm and an extrusion speed of 20 mm/min, leads to a significant improvement in corrosion resistance compared to the solid solutionized AZ91 alloy, as demonstrated by a ∼93% increase in simulated body fluid (SBF). During the friction stir back extrusion of the solid solutionized AZ91 alloy, heat and plastic deformation result in the re-precipitation of the ß-Mg17Al12 phase in the α-Mg matrix. The presence of bioactive glass particles facilitates this re-precipitation process during friction stir back extrusion. In comparison to the solid solutionized AZ91 alloy, the AZ91-3 vol% bioactive glass composite exhibits a 23% increase in ultimate tensile strength (UTS), a 28% increase in yield strength (YS), and a 30% decrease in elongation.

Molecular and biological activities of metal oxide-modified bioactive glass

Bioactive glass (BG) was prepared by sol–gel method following the composition 60-(x) SiO2.34CaO.6P2O5, where x = 10 (FeO, CuO, ZnO or GeO). Samples were then studied with FTIR. Biological activities of the studied samples were processed with antibacterial test. Model molecules for different glass compositions were built and calculated with density functional theory at B3LYP/6-31 g(d) level. Some important parameters such as total dipole moment (TDM), HOMO/LUMO band gap energy (ΔE), and molecular electrostatic potential beside infrared spectra were calculated. Modeling data indicated that P4O10 vibrational characteristics are enhanced by the addition of SiO2.CaO due to electron rush resonating along whole crystal. FTIR results confirmed that the addition of ZnO to P4O10.SiO2.CaO significantly impacted the vibrational characteristics, unlike the other alternatives CuO, FeO and GeO that caused a smaller change in spectral indexing. The obtained values of TDM and ΔE indicated that P4O10.SiO2.CaO doped with ZnO is the most reactive composition. All the prepared BG composites showed antibacterial activity against three different pathogenic bacterial strains, with ZnO-doped BG demonstrating the highest antibacterial activity, confirming the molecular modeling calculations.

Effect of Thermal Treatments and Ion Substitution on Sintering and Crystallization of Bioactive Glasses: A Review.

Bioactive glasses (BGs) are promising materials for bone regeneration due to their ability to bond with living bone tissue. However, thermal stability and mechanical properties of BGs need improvement for better clinical performance. In this paper, we present an overview of the influence of different ions on the sintering and crystallization of BGs. Specifically, this review focuses on the impact of thermal treatments on the crystallization of 45S5 and other significant BG compositions. Potential applications of these thermally treated BGs, such as scaffolds, BG-based composites, and thermally sprayed coatings, are explored. Moreover, the substitution of ions has been investigated as a method to enhance the thermal properties of BGs. Notably, zinc, potassium, and strontium have been studied extensively and have demonstrated promising effects on both the thermal and the mechanical properties of BGs. However, it is important to note that research on ion inclusion in BGs is still in its early stages, and further investigation is necessary to fully comprehend the effects of different ions on sintering and crystallization. Therefore, future studies should focus on optimizing the ion substitution method to improve the thermal, mechanical, and even biological properties of BGs, thereby enhancing their potential for various biomedical applications.

Incorporation of strontium borosilicate bioactive glass in calcium aluminate biocement: Physicomechanical, bioactivity and antimicrobial properties

Strontium borosilicate bioactive glass (SrBG) and calcium aluminate cement (CA) composites have been synthesized. The primary goal of this work is to evaluate how SrBG affects the bioactivity and physico-mechanical characteristics of CA. To fulfill this aim, SrBG was prepared by melt–quenching method and utilized as a substitute for CA by 5, 10, 15, and 20 wt%. To estimate the biological behavior of the prepared specimens, hydrᴏxyapatite layer (HA) establishment on the surface of cement paste was followed; after their immersion in a solution resembles human blood plasma (simulated body fluid solution (SBF)) at a temperature of about37 ± 0.5 °C for 4 weeks. The variations of pH, Ca and P ions concentrations in the SBF solution after soaking were determined. Compressive strength, apparent porosity, and bulk density were also measured. Via Fourier transform IR spectroscopy and X-ray diffraction analyses, the main components had been analyzed. Using scanning electron microscope (SEM) attached to energy dispersive spectroscopy, morphology of the samples was investigated. Additionally, the antimicrobial property was also assessed. The results proved that the hydrᴏxyapatite layer (HA) was developed on the surface of the prepared samples after soaking in the biological solution (SBF). It was also found that increasing SrBG percent in synthesized samples promotes the physico-mechanical characteristics and also the bioactivity performance of CA cement.Finally, these materials also showed good inhibition behavior towards bacterial biᴏfilms, against S. aureus and E. coli. after 48h. This makes these materials excellent candidates for preventing growth of bacteria after their implantation in teeth or bone.

Chemical interactions in composites of gellan gum and bioactive glass: self-crosslinking and in vitro dissolution.

We investigated the interactions between the organic-inorganic phases in composites and the impact on in vitro dissolution. The composite consists of a hydrogel-forming polysaccharide gellan gum (GG, organic phase) and a borosilicate bioactive glass (BAG, inorganic phase). The BAG loading in the gellan gum matrix varied from 10 to 50wt%. While mixing GG and BAG, the ions released from BAG microparticles crosslinked with the carboxylate anions of GG. The nature of the crosslinking was assessed, and its impact on mechanical properties, swelling ratio, and enzymatic degradation profile upon immersion for up to 2weeks was studied. Loading up to 30wt% of BAG in GG caused an increase in mechanical properties associated with an increasing crosslinking density. At higher BAG loading, excess divalent ions and percolation of particles led to a decrease in the fracture strength and compressive modulus. Upon immersion, a decrease in the composite mechanical properties was attributed to the dissolution of the BAG and the loosening of the glass/matrix interface. The enzymatic degradation of the composites was inhibited at higher BAG loadings (40 and 50wt%) even when the specimen was immersed for 48h in PBS buffer with lysozyme. During in vitro dissolution in both SBF and PBS, the ions released from the glass led to the precipitation of hydroxyapatite already at day 7. In conclusion, we thoroughly discussed the in vitro stability of the GG/BAG composite and established the maximum BAG loading to enhance the GG crosslinking and mechanical properties. Based on this study, 30, 40, and 50wt% of BAG in GG will be further investigated in an in vitro cell culture study.

Development and characterization of solvent-based 3D printed polylactic acid/45S5 bioactive glass composites for soft and hard tissue engineering.

With the benefit of offering hydrolysis breakdown and bio-resorption of its products, polylactic acid (PLA) is among the most frequently utilized polymers for many biomedical applications. Composites made of polylactic acid (PLA) and bioactive substances such as bioactive glass (BG) are developing as novel biomaterials because they comprise the mechanical properties and bioactivity of bioactive glass (BG) with the conformability and bio absorption of PLA. In this work, composites of PLA/BG were produced by employing the solvent-based three-dimensional printing process. To accomplish this, 0-2 wt% of BG particles (size ≤ 2 µm) were added to PLA. The resulting composite mix was then fed into a solvent-based 3D printer for the layer-by-layer construction of composites. According to the SEM/EDX investigation, BG particles were evenly dispersed throughout the polymer matrix which resulted in the interfacial bonding between them. FTIR and XRD analysis showed that PLA and BG did not interact chemically. All the composites were evaluated for cytocompatibility by in vitro cellular tests, which also proved their suitability as a substrate for NIH 3T3 cell adherence and growth. The composites were also found to be good in terms of hemocompatibility and platelet adhesion. In conclusion, additional studies on these materials were encouraged by the successful outcomes, which suggested that 3D-printed composite scaffolds consisting of PLA and BG particles might be useful in soft and hard tissue engineering.

Graphene-bioactive glass composites: Structural, Vickers hardness, and gamma-ray attenuation characteristics

Introduction: Graphene-based materials have gained increasing attention for use in radiation attenuation applications. In this study, pristine graphene nanoplatelet-containing (1, 3, 5, and 10 wt%) borate-based bioactive glass composites were prepared.Methods: Structural properties, Vickers microhardness, and gamma-ray radiation shielding properties of the fabricated composites were examined in detail.Results and Discussion: Results revealed that the inclusion of the graphene in the glass matrix led to a decrease in the bulk density of the glass-based composites from 2.41 to 2.31 g/cm3. Similarly, a decrease in Vickers hardness was obtained as the graphene concentration was increased due to a convoluted effect of the non-uniform distribution of graphene nanoplatelets in the bioactive glass matrix and the higher residual porosity. Vickers hardness of the bare and the 10 wt% graphene-containing bioactive glass discs were measured to be 5.03 ± 0.28 GPa and 1.87 ± 0.56 GPa, respectively. On the other hand, the incorporation of graphene starting from 3 wt% decreased the crack propagation after indentation which may be attributed to an increase in fracture toughness. In the study, fundamental gamma ray absorption properties of graphene-containing bioactive glasses were examined in the 0.015–15 MeV incident photon energy range. For this purpose, the Py-MLBUF code was employed to determine gamma ray absorption parameters. Results showed that linear attenuation coefficients of the glass-based composites decreased due to a decrease in the density of the samples. On the other hand, as graphene was incorporated into the bioactive glass structure, exposure buildup factor and energy absorption buildup factor values increased. The growing graphene ratio in the glass structure contributed negatively to the photon’s tendency to interact with the material.

Bioactive Glass Inhibits Tumor Development from Giant Cell Tumor of Bone-Derived Neoplastic Stromal Cells in a Chicken Chorioallantoic Membrane Assay.

Tumor recurrence is a major problem during the treatment of giant cell tumors of bone (GCTB). We recently identified tumor cell-specific cytotoxic effects of bioactive glasses (BGs) toward neoplastic stromal cells derived from GCTB tissue (GCTSCs) in vitro. Since these data indicated a promising role of BGs in the adjuvant treatment of GCTBs, we aimed to investigate the transferability of the in vitro data into the more complex in vivo situation in the current study. We first analyzed the cytotoxicity of three different BGs in vitro by WST-1 assay after co-cultivation with primary GCTSC cell lines. The effects of BGs on tumor engraftment and growth were analyzed by chicken chorioallantoic membrane (CAM) assays and subsequent quantification of tumor take rates and tumor volumes. In vitro, all tested BGs displayed a cytotoxic effect on GCTSCs that was dependent on BG composition, concentration, and particle size. Comparable effects could be observed within the in vivo environment resulting in reduced tumor take rates and tumor volumes in BG-treated samples. These data indicate a possible clinical application of BGs in the context of GCTB therapy, mediating a reduction of recurrence rates with the simultaneous promotion of bone regeneration.

Surface modification of silicate, borosilicate and phosphate bioactive glasses to improve/control protein adsorption: PART I

Bioactive glasses (BGs) are promising for bone tissue regeneration. BG composition can be tailored, according to the application of interest, and/or functionalized with organic molecules/biomolecules to improve their performances. However, despite the wide knowledge concerning BGs, their interaction with proteins, fundamental for controlling the fate of the implant, has not been deeply investigated yet. Controlling or predicting protein adsorption requires a full understanding of the materials surface physico-chemical properties. In this work, four different BGs (S53P4, B25, SCNB, PhGlass) were surface-modified by four different treatments: 72 h-soaking in TRIS, 72 h soaking in simulated body fluid, APTES grafting and quaternized APTES grafting. The surfaces were then characterized both untreated and after each treatment by contact angle, zeta potential analysis, X-ray photoelectron spectroscopy, Fourier Transform InfraRed–Attenuated Total Reflectance spectroscopy and Scanning Electron Microscopy and Energy Dispersive Spectroscopy. Inductively Coupled Plasma – Optical Emission Spectrometry was then performed to investigate the ion leaching. The aim of this study (Part I) is the physico-chemical characterization of BGs as a function of the implemented treatments, aiming to better understand how the superficial properties are successively affecting protein adsorption. Protein adsorption on untreated and treated BGs will be discussed in a following manuscript (Part II).

Effect of bioactive glass particles on mechanical and adhesion properties of resin cements.

The aim of this study is to evaluate the mechanical and adhesive properties of three different resin cements with bioactive glass (BAG) incorporated in two different ratios. BAG was added to different resin cements (3M Rely-X Ultimate, GC Link Ace, and GC Link Force) in different ratios (5% and 10% by weight). The three-point flexural strength, microhardness, and bond strength properties were evaluated. The fracture types of the groups were then analyzed using a stereo microscope. The data were analyzed using a multifactorial analysis of variance and Tukey's post-hoc tests (α < 0.05). The addition of BAG reduced the flexural strength of the resin cements (P < 0.05).The effect of BAG addition on the Vickers microhardness value was significantly different for each cement group (P < 0.05). In addition, with the exception of the GC link force group (10% BAG addition), the BAG addition decreased the bond strength of cements to dentin in all the groups (P = 0.171). The results of this study confirmed that different resin cements comprising different ratios of BAG exhibited different flexural strength, hardness, and bond-strength properties. Since the bond strength values increased with the addition of 10% BAG in the GC Link Force cement group, the effects of different BAG compositions could be worth investigating in future studies.

Gelatin and Bioactive Glass Composites for Tissue Engineering: A Review.

Nano-/micron-sized bioactive glass (BG) particles are attractive candidates for both soft and hard tissue engineering. They can chemically bond to the host tissues, enhance new tissue formation, activate cell proliferation, stimulate the genetic expression of proteins, and trigger unique anti-bacterial, anti-inflammatory, and anti-cancer functionalities. Recently, composites based on biopolymers and BG particles have been developed with various state-of-the-art techniques for tissue engineering. Gelatin, a semi-synthetic biopolymer, has attracted the attention of researchers because it is derived from the most abundant protein in the body, viz., collagen. It is a polymer that can be dissolved in water and processed to acquire different configurations, such as hydrogels, fibers, films, and scaffolds. Searching "bioactive glass gelatin" in the tile on Scopus renders 80 highly relevant articles published in the last ~10 years, which signifies the importance of such composites. First, this review addresses the basic concepts of soft and hard tissue engineering, including the healing mechanisms and limitations ahead. Then, current knowledge on gelatin/BG composites including composition, processing and properties is summarized and discussed both for soft and hard tissue applications. This review explores physical, chemical and mechanical features and ion-release effects of such composites concerning osteogenic and angiogenic responses in vivo and in vitro. Additionally, recent developments of BG/gelatin composites using 3D/4D printing for tissue engineering are presented. Finally, the perspectives and current challenges in developing desirable composites for the regeneration of different tissues are outlined.

Preparation, Characterization, and Drug Delivery of Hexagonal Boron Nitride-Borate Bioactive Glass Biomimetic Scaffolds for Bone Tissue Engineering

In this study, biomimetic borate-based bioactive glass scaffolds containing hexagonal boron nitride hBN nanoparticles (0.1, 0.2, 0.5, 1, and 2% by weight) were manufactured with the polymer foam replication technique to be used in hard tissue engineering and drug delivery applications. To create three-dimensional cylindrical-shaped scaffolds, polyurethane foams were used as templates and covered using a suspension of glass and hBN powder mixture. Then, a heat treatment was applied at 570 °C in an air atmosphere to remove the polymer foam from the structure and to sinter the glass structures. The structural, morphological, and mechanical properties of the fabricated composites were examined in detail. The in vitro bioactivity of the prepared composites was tested in simulated body fluid, and the release behavior of gentamicin sulfate and 5-fluorouracil from glass scaffolds were analyzed separately as a function of time. The cytotoxicity was investigated using osteoblastic MC3T3-E1 cells. The findings indicated that the hBN nanoparticles, up to a certain concentration in the glass matrix, improved the mechanical strength of the glass scaffolds, which mimic the cancellous bone. Additionally, the inclusion of hBN nanoparticles enhanced the in vitro hydroxyapatite-forming ability of bioactive glass composites. The presence of hBN nanoparticles accelerated the drug release rates of the system. It was concluded that bioactive glass/hBN composite scaffolds mimicking native bone tissue could be used for bone tissue repair and regeneration applications.