Borosilicate Bioactive Glass Research Articles

Exploring the bioactivity and antibacterial properties of silver and cerium co-doped borosilicate bioactive glass.

Bone defects resulting from trauma or diseases that lead to bone loss have created a growing need for innovative materials suitable for treating bone-related conditions. The purpose of this study is, therefore, to synthesize and analyse the synergistic effects of cerium (Ce) and cerium-silver (Ce-Ag) doping of borosilicate bioactive glass (BBG) on the bioactivity, antibacterial properties, and biocompatibility for potential applications in bone tissue engineering. This study utilized a sol-gel Stöber method to synthesize doped BBGs based on S49B4. Characterization techniques were utilized to evaluate the thermal stability, elemental composition, structural integrity, and morphological properties of the synthesized Ce and AgCe-BBGs. Cytotoxicity was evaluated using a GMSM-K gingival cell line, while antimicrobial tests were conducted using clinical isolates of Escherichia coli and Staphylococcus aureus. The characterization results confirmed the successful incorporation of Ce and Ag, resulting in elongated pineal to spherical nanosized BG particles (33-68 nm). Thermal analysis indicated that silver exhibited lower thermal stability compared to cerium. Bioactivity tests indicated that while silver has intrinsic bioactive qualities, elevated cerium levels above 0.5 wt% may inhibit or delay apatite formation by generating insoluble cerium phosphate ions. Lactate dehydrogenase assays demonstrated that among other BBGs, SBAgCe1 showed the highest LDH activity, suggesting mild cytotoxicity. The co-doped BBG exhibited strong antibacterial activity through a complex interaction between Ag and Ce ionic exchange. Nonetheless, a careful balance of Ce and Ag concentrations is critical, as high levels can compromise bioactivity and increase cytotoxicity. The results highlight the potential of SBAgCe0.5 as a candidate for bone tissue engineering applications due to its favourable bioactivity, and antibacterial and cytocompatible properties, emphasizing the importance of optimizing dopant concentrations for therapeutic applications in favour of good health and the well-being of humanity.

A Multisynergistic Strategy for Bone Tumor Treatment: Orchestrating Oxidative Stress and Autophagic Flux Inhibition by Environmental-Response Nanoparticle.

Tumor therapy has advanced significantly in recent years, but tumor cells can still evade and survive the treatment through various mechanisms. Notably, tumor cells use autophagy to sustain viability by removing impaired mitochondria and clearing excess reactive oxygen species (ROS). In this study, the aim is to amplify intracellular oxidative stress by inhibiting mitochondrial autophagic flux. Multisynergistic environmental-response nanoparticles (ERNs) are engineered by integrating gold nanoparticles and copper peroxide with borosilicate bioactive glass. The controlled release of copper and inhibition of autophagy flux triggered an overabundance and accumulation of oxidative stress within the tumor cells. This stress triggered immunogenic tumor cell death, believed to initiate a systemic immune response. The tumor microenvironment (TME)transitioned back to a normal physiological state as tumor cells are ablated. ERNs responded to the microenvironment changes by depositing hydroxyapatite on the surface and spontaneously enhancing bone regeneration. This innovative formulation facilitates the functional transition of ERNs from "anti-tumor therapy" to "biomineralization" that kills cancers and induces new bone formation. Overall, it is shown that the ERNs effectively eradicate cancers by utilizing chemodynamic therapy, starvation therapy, and immunotherapy.

Borosilicate bioactive glasses with added Mg/Sr enhances human adipose-derived stem cells osteogenic commitment and angiogenic properties

Bioactive glasses are one of the most promising materials for applications in bone tissue engineering. In this study, the focus was on borosilicate bioactive glasses with composition 47.12 SiO2 - 6.73 B2O3 - 21.77-x-y CaO - 22.65 Na2O - 1.72 P2O5 - x MgO - y SrO (mol%). These compositions are based on silicate S53P4 bioactive glass, from where 12.5% of SiO2 is replaced with B2O3, and additionally, part of CaO is substituted for MgO and/or SrO. The impact of ion release, both as extract and in direct contact, on human adipose-derived stem cells’ (hADSCs) viability, proliferation, ECM maturation, osteogenic commitment and endothelial marker expression was assessed. Osteogenic media supplements were utilized with the extracts, and in part of the direct cell/material culturing conditions. While it has been reported in other studies that boron release can induce cytotoxicity, the glasses in this study supported cells viability and proliferation. Moreover, borosilicate’s, especially with further Mg/Sr substitutions, upregulated several osteogenic markers (such as RUNX2a, OSTERIX, DLX5, OSTEOPONTIN), as well as angiogenic factors (e.g., vWF and PECAM-1). Furthermore, the studied glasses supported collagen-I production even in the absence of osteogenic supplements, when hADSCs were cultured in contact with the glasses, suggesting that while the bioactive glass degradation products are beneficial for osteogenesis, the glasses surface physico-chemical properties play a significant role on hADSCs differentiation. This study brings critical information on the impact of bioactive glass compositional modification to control glass dissolution and the subsequent influence on stem cells proliferation and differentiation. Furthermore, the role of the material surface chemistry on promoting cell differentiation is reported.Graphical

Borosilicate bioactive glass synergizing low-dose antibiotic loaded implants to combat bacteria through ATP disruption and oxidative stress to sequentially achieve osseointegration

Bone infection is a catastrophe in clinical orthopedics. Despite being the standard therapy for osteomyelitis, antibiotic-loaded polymethyl methacrylate (PMMA) cement has low efficiency against bacteria in biofilms. Furthermore, high-dose antibiotic-loaded implants carry risks of bacterial resistance, tissue toxicity, and impairment of local tissue healing. By incorporating borosilicate bioactive glass (BSG) into low-dose gentamicin sulfate (GS)-loaded PMMA cement, an intelligent strategy that synergistically eradicates bacteria and sequentially promotes osseointegration, was devised. Results showed that BSG did not compromises the handling properties of the cement, but actually endowed it with an ionic and alkaline microenvironment, thereby damaging the integrity of bacterial cell walls and membranes, inhibiting ATP synthesis by disrupting the respiratory chain in cell membranes and glycogen metabolism, and elevating reactive oxygen species (ROS) levels by weakening antioxidant components (peroxisomes and carotenoids). These antibacterial characteristics of BSG synergistically reinforced the effectiveness of GS, which was far below the actual clinical dosage, achieving efficient bacterial killing and biofilm clearance by binding to the 30S subunit of ribosomes. Furthermore, the released GS and the ionic and alkaline microenvironment from the implants fostered the osteogenic activity of hBMSCs in vitro and coordinately enhanced osseointegration in vivo. Collectively, this study underscores that BSG incorporation offers a promising strategy for reducing antibiotic dosage while simultaneously enhancing the antibacterial activity and osteogenesis of implants. This approach holds potential for resolving the conflict between bacterial resistance and bone infection.

Biocompatibility and antimicrobial efficacy of silver-doped borosilicate bioactive glass for tissue engineering application

Borate bioactive glasses are an auspicious material for tissue engineering applications due to their enhanced dissolution rate, bioactivity, and capacity to integrate therapeutic ions. In this study, borate-based S49B4 bioactive glass doped with silver at mass fraction of 0.5, 1, and 3 wt% were studied for bioactivity, degradation, antibacterial, and cytocompatibility. Thermogravimetric analysis revealed that the bioactive glasses were thermally stable between 600 and 700 °C. Fourier transform infrared spectroscopy and X-ray diffraction confirmed the successful synthesis of an amorphous phase of the doped borosilicate bioactive glasses and the incorporation of silver ion crystals within the structure, as well as associated contributions from borate and silicate network formers in the borosilicate bioactive glass. Morphological evaluation revealed that the borosilicate bioactive glasses exhibit a uniform and spherical shape across all formulations, with the mean particle size varying from 65 to 76 nm. An in-vitro acellular bioactivity in simulated body fluid medium showed that increasing the silver content increased the degradation rate and pH. Besides, scanning electron microscopy and Energy dispersive X-ray spectroscopy analysis revealed an upsurge in apatite production on the BBGs' surfaces as well as incremental Calcium-Phosphate ratio values of 1.50, 1.65 and 1.70 as the silver content increases. The antibacterial effect was tested against Escherichia coli and Staphylococcus aureus, while cytocompatibility was tested against human gingival epithelial cells. Silver integration at 1 wt percent yielded the most promising outcomes, which were particularly bactericidal at 79.8 % for Escherichia coli and 93.41 % for Staphylococcus aureus. Similarly, its Lactate Dehydrogenase percentage is significantly similar to the negative control employed in the study, indicating its biocompatibility. In contrast, 3 wt% silver exhibited the maximum bactericidal activity while also exhibiting mild cytotoxicity. In summary, our research indicates that elevated silver concentration enhances the bioactivity and antimicrobial characteristics of borosilicate bioactive glasses; nevertheless, a higher silver weight percent in this study also increases the possibility of cytotoxicity. It is therefore essential to carefully regulate the amount of silver doping at lower concentrations in order to maximize antibacterial action and minimize toxicity to human cells. The results presented here contribute to our understanding of the prospective use of silver doped borosilicate bioactive glasses as a possible material for tissue engineering applications.

Exploratory Investigation of Zinc-Modified Borosilicate Bioactive Glass: A New Methodology for Its Biocompatibility, Immunoregulation, and Pro-Angiogenic Property Evaluation.

The assessment of biodegradable materials, such as bioactive glass, under the existing ISO 10993 standard test methods poses a significant challenge due to potential cell viability impairment caused by the accumulation of degraded products in a static environment. Therefore, innovative methodologies are urgently needed to tailor the unique biodegradation characteristics of these materials, providing more precise and scientific insights into biosafety and efficacy verification. Motivation by its bidirectional regulation of angiogenesis and immunity, zinc (Zn) was incorporated into sol-gel-derived borosilicate bioactive glasses (SBSGs) to fabricate Zn-incorporated borosilicate bioactive glasses (SBSG-Zn) to complement the tissue repair capabilities of bioactive glasses. Both SBSG and SBSG-Zn glasses consist of nanosized particles, slit mesoporous pores, high specific surface areas, and bioreactivity. In vitro comparative analysis, conducted according to ISO 10993 standards, demonstrates that only at suitable dilution rates─such as the 8-fold dilution employed in this study─do extracts of SBSG and SBSG-Zn glasses exhibit low cytotoxicity when cultured with human umbilical vein endothelial cells (HUVECs). Notably, SBSG-Zn glasses show optimal promotion of angiogenic gene expression in HUVECs. Furthermore, within an appropriate concentration range of released ions, SBSG-Zn glass extracts not only promote cell survival but also modulate the expression of anti-inflammatory genes while simultaneously inhibiting pro-inflammatory genes concurrently. After being implanted in rat subcutaneous defect models, both SBSG and SBSG-Zn glasses demonstrated the local immunoregulation and angiogenic effects. SBSG-Zn stands out by demonstrating superior modulation of M1/M2 polarization in macrophages as validated by altered secretion of key factors in macrophages and expression of relevant growth factors in HUVECs. These findings underscore the potential for convenient manipulation of localized angiogenic and immunoregulation through the incorporation of zinc into bioactive glass, emphasizing the importance of ensuring the appropriate ion doses are applied for achieving optimal therapeutic efficiency.

Diphasic CeO2 Nanocrystal/Bioactive Glass Nanosphere-Based Composite Hydrogel for Diabetic Wound Healing by Reactive Oxygen Species Scavenging and Inflammation Regulation.

Background: Antioxidant therapy aimed at reducing excessive local oxidative stress is one of the most important strategies for promoting diabetic wound repair. The reversible transformation of Ce3+/Ce4+ in ceria (CeO2) can reduce excessive local oxidative stress. However, inducing angiogenesis, local anti-inflammatory effects, and other positive effects are challenging. Therefore, ideal dressings for chronic diabetic wound management must concurrently reduce excessive oxidative stress, promote angiogenesis, and have anti-inflammatory effects. Methods: In this study, Ce-doped borosilicate bioactive glasses (BGs) were prepared using the sol-gel method, and CeO2 nanocrystals (CeO2-NCs) were precipitated on the glass surface by heat treatment to obtain BG-xCe composite glass nanospheres. Subsequently, nanospheres were modified by amino group and combined with dopamine and acrylamide to obtain BG-xCe/polydopamine/polyacrylamide (PDA/PAM) composite hydrogel. Then, the morphology and properties of composite hydrogels were detected, and the properties to treat the diabetic wounds were also evaluated. Results: The results demonstrated that the BG-10Ce/PDA/PAM composite hydrogel possessed excellent tensile and adhesive properties. Invitro, the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) and fibroblasts (L929) were enhanced by reducing reactive oxygen species (ROS) levels in the conditioned medium. Animal experiments have shown that CeO2-NCs in hydrogels effectively scavenge ROS in diabetic wounds, and Sr dissolved from the glassy phase can modulate macrophage polarization to the M2 phenotype. Conclusions: The synergistic effect of both amorphous materials and nanocrystals provides the BG-10Ce/PDA/PAM composite hydrogel with great potential for diabetic wound healing.

Investigating the Mechanical and Tribological Properties of Bio-Waste Derived Bioactive Borosilicate Glass Incorporating Strontium Oxide

Abstract The primary goal of the current research paper is to investigate the mechanical and tribological behavior of biologically active glass consisting of 31B2O3-(20-x) SiO2-24.5Na2O-24.5CaO and xSrO (in mol%). The specimens were fabricated partly using bio-waste material, in which Silica and Calcium Oxide were derived from rice husks and egg shells, respectively. The produced specimens underwent immersion in simulated bodily fluid for a week to observe their bioactive response. The bioactive behavior of the samples were examined using X-ray diffraction and FTIR spectroscopy. The compression test and hardness of the specimens were measured using universal testing machine and Vickers micro-hardness tester. Abrasion test of the specimens were performed on pin-on-disc tribometer and the worn-out surfaces were later analyzed using FESEM. The findings from FTIR and XRD analyses validated the existence of a hydroxyapatite layer on the specimen surfaces. Further, XRD data showed an increase in peak intensity after SrO was incorporated, suggesting that it played a supporting role in boosting bioactivity. The mechanical investigations indicated that the addition of SrO adversely affects both hardness and compression strength. The abrasion wear test demonstrated that BSG-5 had the highest wear rate, while BSG-0 exhibited the lowest wear rate among all specimens at a 30 mm track radius. Despite the trade-off between enhanced bioactivity and diminished mechanical strength and wear resistance, incorporating Strontium Oxide makes the glass suitable for applications prioritizing bioactivity, such as bone filling and dental contexts.

Initial therapeutic evidence of a borosilicate bioactive glass (BSG) and Fe3O4 magnetic nanoparticle scaffold on implant-associated Staphylococcal aureus bone infection

Implant-associated Staphylococcus aureus (S. aureus) osteomyelitis is a severe challenge in orthopedics. While antibiotic-loaded bone cement is a standardized therapeutic approach for S. aureus osteomyelitis, it falls short in eradicating Staphylococcus abscess communities (SACs) and bacteria within osteocyte-lacuna canalicular network (OLCN) and repairing bone defects. To address limitations, we developed a borosilicate bioactive glass (BSG) combined with ferroferric oxide (Fe3O4) magnetic scaffold to enhance antibacterial efficacy and bone repair capabilities. We conducted comprehensive assessments of the osteoinductive, immunomodulatory, antibacterial properties, and thermal response of this scaffold, with or without an alternating magnetic field (AMF). Utilizing a well-established implant-related S. aureus tibial infection rabbit model, we evaluated its antibacterial performance in vivo. RNA transcriptome sequencing demonstrated that BSG + 5%Fe3O4 enhanced the immune response to bacteria and promoted osteogenic differentiation and mineralization of MSCs. Notably, BSG + 5%Fe3O4 upregulated gene expression of NOD-like receptor and TNF pathway in MSCs, alongside increased the expression of osteogenic factors (RUNX2, ALP and OCN) in vitro. Flow cytometry on macrophage exhibited a polarization effect towards M2, accompanied by upregulation of anti-inflammatory genes (TGF-β1 and IL-1Ra) and downregulation of pro-inflammatory genes (IL-6 and IL-1β) among macrophages. In vivo CT imaging revealed the absence of osteolysis and periosteal response in rabbits treated with BSG + 5%Fe3O4 + AMF at 42 days. Histological analysis indicated complete controls of SACs and bacteria within OLCN by day 42, along with new bone formation, signifying effective control of S. aureus osteomyelitis. Further investigations will focus on the in vivo biosafety and biological mechanism of this scaffold within infectious microenvironment.

A Composite Hydrogel Functionalized by Borosilicate Bioactive Glasses and VEGF for Critical-Size Bone Regeneration.

Critical-size bone defects pose a formidable challenge in clinical treatment, prompting extensive research efforts to address this problem. In this study, an inorganic-organic multifunctional composite hydrogel denoted as PLG-g-TA/VEGF/Sr-BGNPs is developed, engineered for the synergistic management of bone defects. The composite hydrogel demonstrated the capacity for mineralization, hydroxyapatite formation, and gradual release of essential functional ions and vascular endothelial growth factor (VEGF) and also maintained an alkaline microenvironment. The composite hydrogel promoted the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs), as indicated by increased expression of osteogenesis-related genes and proteins in vitro. Moreover, the composite hydrogel significantly enhanced the tube-forming capability of human umbilical vein endothelial cells (HUVECs) and effectively inhibited the process of osteoblastic differentiation of nuclear factor kappa-B ligand (RANKL)-induced Raw264.7 cells and osteoclast bone resorption. After the implantation of the composite hydrogel into rat cranial bone defects, the expression of osteogenic and angiogenic biomarkers increased, substantiating its efficacy in promoting bone defect repair in vivo. The commendable attributes of the multifunctional composite hydrogel underscore its pivotal role in expediting hydrogel-associated bone growth and repairing critical bone defects, positioning it as a promising adjuvant therapy candidate for large-segment bone defects.

A comprehensive study on bioactivity, mechanical and tribological behavior of copper-doped borosilicate glass derived from natural waste for dental applications

The present study investigates in-vitro biomineralization, mechanical, and tribological properties of bioactive borosilicate glass composed of 31B2O3–20SiO2-(24.5-x)Na2O-24.5CaO and xCuO (mol%). Glass was manufactured using conventional melt-quench technique, utilizing chemicals partially derived from bio-waste, with varying copper oxide (CuO) content (x = 0, 1, 3, and 5). In-vitro study was conducted by immersing the specimens in simulated body fluid for 21 days. The formation of apatite layer was confirmed using FTIR, XRD and FESEM-EDS. Vicker's micro hardness tester and a universal testing machine measured hardness and compressive strength, while a pin-on-disc tribometer assessed wear. MTT assay was performed for all the specimens using osteosarcoma MG63 cell line. The study revealed that substituting copper in place of sodium increased the ion dissolution and improved the formation of the apatite layer hence, enhanced the bioactivity, however, accompanied by a gradual decrease in hardness and compressive strength. BSG-0 exhibited the highest hardness (6.64 GPa) and compressive strength (86.81 MPa), while wear resistance weakened with higher CuO content, notably in BSG-5 with the highest specific wear rate (0.072 mm³/N-m) under a 5 N load. Although MTT assay showed non-toxicity for all specimens, except BSG-5, the compounds demonstrated cell tolerance and growth stimulation. In conclusion, the study suggests that CuO-doped borosilicate glasses exhibit superior bioactivity, making them potentially effective for bone filling, wound healing, and dental applications, despite a compromise in mechanical strength and wear resistance.

A comparative in vitro and in vivo analysis of the impact of copper substitution on the cytocompatibility, osteogenic, and angiogenic properties of a borosilicate bioactive glass.

The 0106-B1-bioactive glass (BG) composition (in wt %: 37.5 SiO2, 22.6 CaO, 5.9 Na2O, 4.0 P2O5, 12.0 K2O, 5.5 MgO, and 12.5 B2O3) has demonstrated favorable processing properties and promising bone regeneration potential. The present study aimed to evaluate the biological effects of the incorporation of highly pro-angiogenic copper (Cu) in 0106-B1-BG in vitro using human bone marrow-derived mesenchymal stromal cells (BMSCs) as well as its in vivo potential for bone regeneration. CuO was added to 0106-B1-BG in exchange for CaO, resulting in Cu-doped BG compositions containing 1.0, 2.5 and 5.0 wt % CuO (composition in wt %: 37.5 SiO2, 21.6/ 20.1/17.6 CaO, 5.9 Na2O, 4.0 P2O5, 12.0 K2O, 5.5 MgO, 12.5 B2O3, and 1.0/ 2.5/ 5.0 CuO). In vitro, the BGs' impact on the viability, proliferation, and growth patterns of BMSCs was evaluated. Analyses of protein secretion, matrix formation, and gene expression were used for the assessment of the BGs' influence on BMSCs regarding osteogenic differentiation and angiogenic stimulation. The presence of Cu improved cytocompatibility, osteogenic differentiation, and angiogenic response when compared with unmodified 0106-B1-BG in vitro. In vivo, a critical-size femoral defect in rats was filled with scaffolds made from BGs. Bone regeneration was evaluated by micro-computed tomography. Histological analysis was performed to assess bone maturation and angiogenesis. In vivo effects regarding defect closure, presence of osteoclastic cells or vascular structures in the defect were not significantly changed by the addition of Cu compared with undoped 0106-B1-BG scaffolds. Hence, while the in vitro properties of the 0106-B1-BG were significantly improved by the incorporation of Cu, further evaluation of the BG composition is necessary to transfer these effects to an in vivo setting.

Pore graded borosilicate bioactive glass scaffolds: in vitro dissolution and cytocompatibility

3D borosilicate bioactive glass (1393B20 and B12.5MgSr) scaffolds were prepared by robocasting, with and without a dense layer at the top. Pore graded scaffolds are promising as they allow for membrane deposition and could limit the risk of soft tissue infiltration. In vitro dissolution was studied in tris(hydroxymethyl)aminomethane (TRIS) and Simulated Body Fluid (SBF). 1393B20 scaffolds dissolved faster than B12.5MgSr in TRIS whereas they dissolved slower in SBF. The difference in dissolution profiles, as a function of the medium used, is assigned to the different rates of precipitation of hydroxyapatite (HA). While the precipitation of calcium phosphate (CaP) in the form of HA, first sign of bioactivity, was confirmed by ICP, FTIR-ATR and SEM-EDX analysis for both compositions, 1393B20 was found to precipitate HA at a faster rate. The presence of a dense top layer did not significantly impact the dissolution rate and CaP precipitation. In vitro cell culture was performed using human adipose-derived stem cells (hADSCs). Prior to cell plating, a preincubation of 3 days was found optimum to prevent burst ion release. In direct contact, cells proliferate and spread on the scaffolds while maintaining characteristic spindle morphology. Cell plated on 1393B20 scaffolds showed increased viability when compared to cell plated on B12.5MgSr. The lower cell viability, when testing B12.5MgSr, was assigned to the depletion of Ca2+ ions from culture medium and higher pH. Static cell culture leads to believe that the scaffold produced from the 1393B20 glass composition are promising in bone regeneration applications.Graphical

Biological effects of a zinc-substituted borosilicate bioactive glass on human bone marrow derived stromal cells in vitro and in a critical-size femoral defect model in rats in vivo.

The borosilicate 0106-B1-bioactive glass (BG) composition (in wt%: 37.5 SiO2, 22.6 CaO, 5.9 Na2O, 4.0P2O5, 12.0 K2O, 5.5 MgO, 12.5 B2O3) has shown favorable processing characteristics and bone regeneration ability. This study investigated the addition of zinc (Zn) to 0106-B1-BG as an approach to improve this BG's biological properties. Different proportions of ZnO were substituted for CaO in 0106-B1-BG, resulting in three new BG-compositions: 1-Zn-BG, 2-Zn-BG, 3-Zn-BG (in wt%: 37.5 SiO2, 21.6/20.1/17.6 CaO, 4.0 P2O5, 5.9 Na2O, 12.0 K2O, 5.5 MgO, 12.5 B2O3 and 1.0/2.5/5.0 ZnO). Effects of the BG compositions on cytocompatibility, osteogenic differentiation, extracellular matrix deposition, and angiogenic response of human bone marrow-derived mesenchymal stromal cells (BMSCs) were evaluated in vitro. Angiogenic effects were assessed using a tube formation assay containing human umbilical vein endothelial cells. The in vivo osteogenic and angiogenic potentials of 3-Zn-BG were investigated in comparison to the Zn-free 0106-B1-BG in a rodent critical-size femoral defect model. The osteogenic differentiation of BMSCs improved in the presence of Zn. 3-Zn-BG showed enhanced angiogenic potential, as confirmed by the tube formation assay. While Zn-doped BGs showed clearly superior biological properties in vitro, 3-Zn-BG and 0106-B1-BG equally promoted the formation of new bone in vivo; however, 3-Zn-BG reduced osteoclastic cells and vascular structures in vivo. The acquired data suggests that the differences regarding the in vivo and in vitro results may be due to modulation of inflammatory responses by Zn, as described in the literature. The inflammatory effect should be investigated further to promote clinical applications of Zn-doped BGs.

Microcrystallization Effects in Borosilicate Bioactive Glasses: Controllable Release of Bioactive Elements and In Vitro Degradation Properties.

Borosilicate bioactive glasses exhibit excellent bioactivity and degradation properties; however, they suffer from the rapid release of bioactive elements at the initial stage of their degradation. Excessive local concentrations (such as those of B) can affect cell proliferation. Moreover, the degradation and mineralization ability of these glasses deteriorate at the later stages. Aiming to balance the release of bioactive elements during the whole process, herein, a borosilicate bioactive glass 18SiO2-6Na2O-8K2O-8MgO-22CaO-2P2O5-36B2O3 (mol%) was prepared using the melting method. Further, the effects of microcrystallization on the release of bioactive elements and in vitro degradation were studied. Results show that after heat treatment at temperatures over 620 °C, multiple microcrystalline phases, including Ca2SiO4, CaB2O4, and CaMgB2O5, form in the glass. The glass samples heat-treated within the range of 620-640 °C undergo appropriate devitrification degrees, decelerating the rate of pH increase of the immersion solution during the initial stage in comparison to those treated at lower temperatures. This results in a more continuous release of all bioactive elements and allows better control of the overall degradation. Contrarily, the more extensive devitrification degrees of glass samples heat-treated at higher temperatures reverse the pH increase and degradation trends. Since bone marrow mesenchymal stem cells and mouse embryonic osteoblast cells are pH-sensitive, inducing a suitable degree of devitrification proved to favor cell viability and enhance the mineralization capacity. Thus, different microcrystallization degrees provide new approaches for controlling the degradation and release of bioactive elements, resulting in the simultaneous enhancement of biosafety and bioactivity.

Design of sol-gel bioactive glasses: Towards tailored architecture and ion-supply for bone tissue regeneration

This paper reports the synthesis of borosilicate bioactive glasses nanoparticles containing ions of interest (calcium, strontium or silver ions) for the purpose of bone tissue regeneration using a modified Stöber method and their shaping by robocasting to produce macroporous grid-like architectures with controlled interconnected porosity. Main focus is on the design of a paste formulation, the optimization of the robocasting process to produce 3D scaffolds and ion release from the sintered scaffold in solution. Pastes were developed (40 vol% powder loading), characterized, and extruded layer-by-layer to form three-dimensional scaffolds with a grid-like macrostructure (400 μm diameter of the rods). After drying under controlled atmosphere, scaffolds were sintered. The sintering study revealed that the addition of silver reduced the densification point of the borosilicate glass. After immersion in a buffer solution, ionic release (Si, B and Sr) of the sintered scaffold was evaluated, and compared with the synthetized powder. The shaping process did not affect Sr dissolution. This controllable ion-release behavior of the scaffolds are promising for their therapeutic application.

The effect of borate on acellular bioactivity of novel mesoporous borosilicate bioactive glasses for tissue engineering

Four novel mesoporous borate-based 13–93 bioactive glass has been synthesized by a modified Stöber method. Thermogravimetric analysis, Inductively coupled plasma atomic emission spectroscopy, Fourier Transform Infrared Spectroscopy, X-Ray diffraction, Brunauer–Emmet–Teller and Barrett–Joyner–Halenda, nuclear magnetic resonance and Scanning Electron Microscope attached with Energy-dispersive X-ray spectroscopy analyses were carried out to investigate the physicochemical properties, in-vitro acellular bioactivity, and the degradation rate of the bioactive glasses in simulated body fluid across a range of times up to 21 days. The characterization data indicates that the bioactive glasses are amorphous and possess mesoporous properties. Likewise, an increase in boron content reduced the surface area and pore volume of the bioactive glass series. The observed decline is attributed to borate units' smaller atomic radius than silicate. The ability to deposit a new apatite layer in the bioactive glasses depends on the borate concentration. As such, an increase in boron content resulted in a decrease in apatite formation. Additionally, the studies showed that bioactive glasses made of borate degraded more quickly than their silicate counterpart. Overall, borate-based 13–93 bioactive glasses were effectively synthesized, and the in-vitro results showed potential usage for these bioactive glasses in tissue engineering situations where it is desirable to control bone growth or delay the onset of bioactivity.

Microstructural investigation of hydroxyapatite formation in bioactive borosilicate glass

Microstructural investigation of hydroxyapatite formation in bioactive borosilicate glass

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.

Correction to: Effect of Boron Incorporation on the Mechanical, and Radiation Shielding Behaviors of Borosilicate Bioactive Glasses

Correction to: Effect of Boron Incorporation on the Mechanical, and Radiation Shielding Behaviors of Borosilicate Bioactive Glasses