A feasible approach toward bioactive glass nanofibers with tunable protein release kinetics for bone scaffolds

Preparation, in vitro mineralization and osteoblast cell response of electrospun 13-93 bioactive glass nanofibers.

Novel biodegradable hybrid composite of polylactic acid (PLA) matrix reinforced by bioactive glass (BG) fibres and magnesium (Mg) wires for orthopaedic application

The effects of Sm3+ content on the optical properties and bioactivity of 13-93 bioactive glass were presented. Sm3+ doped glass fibers drawn from bioactive glass were analyzed in simulated body fluid (SBF) for the determination of ion release. Optical analysis of the Sm3+ ions in bioactive glass fibers was used for degradation monitoring. While the fibers were immersed in SBF solution, changes in their luminescence spectra under 405 nm laser excitation were measured continuously for 48 h. The morphology of the fibers after the immersion process was determined by SEM/EDS. It was shown that the proposed approach to the analysis of changes in Sm3+ ion luminescence is a sensitive method for the monitoring of degradation processes and the formation of hydroxycarbonate-apatite (HCA) layers on glass fiber surfaces. SEM/EDS measurements showed a significant deterioration on the surface of the fibers and the formation of HCA on 13-93_02Sm bioactive glass. The optical analysis of the time constant indicated that bioactive glass fibers doped with 2 %mol Sm3+ degrade at a rate almost five times slower than 13-93_02Sm.

In order to provide a fixation vehicle between a polymeric composite femoral hip prosthesis and bone tissue, we fabricated bioactive glass fibers. The glass fibers had a tensile strength of 596 MPa, 14 times that of bulk bioactive glass. After immersion in protein-free simulated body fluid for 10 days, we observed the development of a calcium phosphate layer (specifically, partially crystallized, calcium-deficient carbonated hydroxyapatite) on the surface of the glass fibers. The stages of the surface reaction layer formation were similar to those of 45S5 bioactive glass although the kinetics of the reaction layer formation were slower. We combined the bioactive glass fibers with a polymeric matrix to form a fiber-reinforced composite material and observed the formation of a calcium phosphate layer on the surface of the glass fibers within the composite material after immersion in both protein-free and protein-containing simulated body fluids. The rate of reaction layer formation was reduced in the presence of proteins. In both protein-free and protein-containing solutions, a “halo” of bioactivity reactions was observed on the surface of the polymer in regions surrounding the glass fibers. Our results suggest these glass fibers and glass fiber composites will exhibit bioactivity reactions in vivo. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 37, 440–448, 1997.

In order to provide a fixation vehicle between a polymeric composite femoral hip prosthesis and bone tissue, we fabricated bioactive glass fibers. The glass fibers had a tensile strength of 596 MPa, 14 times that of bulk bioactive glass. After immersion in protein-free simulated body fluid for 10 days, we observed the development of a calcium phosphate layer (specifically, partially crystallized, calcium-deficient carbonated hydroxyapatite) on the surface of the glass fibers. The stages of the surface reaction layer formation were similar to those of 45S5 bioactive glass although the kinetics of the reaction layer formation were slower. We combined the bioactive glass fibers with a polymeric matrix to form a fiber-reinforced composite material and observed the formation of a calcium phosphate layer on the surface of the glass fibers within the composite material after immersion in both protein-free and protein-containing simulated body fluids. The rate of reaction layer formation was reduced in the presence of proteins. In both protein-free and protein-containing solutions, a "halo" of bioactivity reactions was observed on the surface of the polymer in regions surrounding the glass fibers. Our results suggest these glass fibers and glass fiber composites will exhibit bioactivity reactions in vivo.

Submicron bioactive glass tubes for bone tissue engineering

The purpose of this study was to perform an intra-animal comparison of biodegradable woven fabrics made of bioactive glass (BG) fibers and poly(L-lactide-co-glycolide) 80/20 copolymer (PLGA(80)) fibers or PLGA(80) fibers alone, in surgical stabilization of bone graft. The BG fibers (BG 1-98) were aimed to enhance bone growth at site of bone grafting, whereas the PLGA component was intended to provide structural strength and flexibility to the fabric. Bone formation was analyzed qualitatively by histology and quantitatively by peripheral quantitative computed tomography (pQCT) at 12 weeks. The surgical handling properties of the control PLGA(80) fabric were more favorable. Both fabrics were integrated with the cortical bone surfaces, but BG fibers showed almost complete resorption. There were no signs of adverse local tissue reactions. As a proof of material integration and induced new bone formation, there was a significant increase in bone volume of the operated femurs compared with the contralateral intact bone (25% with BG/PLGA(80) fabric, p < 0.001 and 28% with the control PLGA(80) fabric, p = 0.006). This study failed to demonstrate the previously seen positive effect of BG 1-98 on osteogenesis, probably due to the changed resorption properties of BG in the form of fibers. Therefore, the feasibility and safety of BG as fibers needs to be reevaluated before use in clinical applications.

Preparation and in vitro characterization of electrospun 45S5 bioactive glass nanofibers

Bioactive glasses (BGs) exhibit potential applications for gene transfection because of their composition including Ca and P. Here, bioactive glass fibers (BGFs) with mesopores or hierarchical nanopores, were prepared by electrospinning process using BGs Sol-Gel precursor and its effect on mediating gene transfection was investigated. The results indicate that BGF acts as a gene vector by releasing Ca and PO4, and then reunioning them along with plasmid DNA in Dulbecco's Modified Eagle’s Medium (DMEM). BGFs have a dose-dependent manner in transfection efficiency. When using 1 μg/mL plasmid, the transfection efficiency of BGF with concentration at 1000 μg/mL is higher than 50% of lipofectamine LTX_PLUS. The transfection mechanism of BGF is similar to that of calcium phosphate (CaP) system. Furthermore, BGF’s sufficient ions releasing ensures stability and effectiveness to be applied in gene transfection, which makes BGF a promising candidate for gene delivery in replace of traditional gene carrier, the nano-calcium phosphate system.

Tissue regeneration and tumor cell killing after surgical resection are the two keys to achieving effective tumor therapy. In this study, an implantable system with combined functions of tumor therapy and tissue repair was constructed. Tannic acid (TA)/Fe3+ nanoparticles with Fenton catalytic activity were loaded with GSH inhibitor BSO drug (BTF), and acted as the therapeutic factor to realize amplified chemodynamic tumor treatment. Bioactive glass (BG) fibers loaded with vascular endothelial growth factor (VEGF) were used as the drug carrier matrix with tissue repair function (BGV). Then the BGV@BTF composite fibers were obtained by anchoring BTF nanoparticles on the surface of BGV fibers. Under tumorous acidic conditions, BTF nanoparticles can be released from the composite fibers, and taken up by tumor cells. Facilitated by BSO with the GSH suppression effect and TA with Fe3+ reducing properties, BTF nanoparticles can realize high oxidative stress in tumor cells and subsequent cell death. In addition, BG fibers and VEGF can both promote tissue regeneration and accelerate postoperative wound healing. The simultaneous suppression of tumor growth and promotion of tissue repair in this work is inspiring in the field of postoperative tumor treatment and recovery.

Effect of immersion in SBF on porous bioactive bodies made by sintering bioactive glass microspheres

Event Abstract Back to Event Newly developed bioactive borosilicate glasses: impact of boron on particles sintering and hASCs response. Ayush Mishra1*, Minna Ojansivu2, 3*, Maeva Fabert1*, Nirajan Ohja1*, Erika Erasmus4*, Iakovos Sigalas4*, Susanna Miettinen2, 3 and Jonathan Massera1, 3* 1 Tampere University of Technology, Department of Electronics and Communications Engineering, Biomaterials and Tissue Engineering Group, Finland 2 University of Tampere, Adult Stem Cell Research Group, Finland 3 BioMediTech, Finland 4 University of the Witwatersrand, School of Chemical and Metallurgical Engineering, South Africa Introduction: Traditional bioactive glasses (BAG) face major drawbacks. They are prone to crystallization during hot working which inhibits the glass sintering and reduces the glass bioactivity[1]. Furthermore, studies have shown that, 14 years post-surgery, incomplete conversion of the glass into hydroxyapatite (HA) led to glass particles reminiscence[2]. Thus, there is a need for new BAG that can convert fully into HA while having thermal properties enabling sintering. Materials and Methods: Glasses based on the S53P4 (commercial glass) composition were processed with various B2O3/(SiO2+B2O3) ratio (0% (B0), 25% (B25), 50% (B50), 75% (B75) and 100% (B100)). The glasses’ characteristic temperatures were recorded using DTA. The structural properties of the materials were assessed by FTIR, Raman spectroscopy and 11B NMR. The dissolution test was performed by immersing glass particles in simulated body fluid (SBF) for up to 168h. The pH and Ca concentration (Atomic Absorption Spectrometry) were measured as a function of immersion time. The formation of HA was assessed using EDX/SEM and FTIR. Human adipose stem cells (hASC) were plated on top of glass discs and the biocompatibility of the materials confirmed by live/dead staining. Results and Discussion: In this presentation, we will show that upon immersion, the pH of all solutions increases due to glass dissolution. The Ca concentration in the SBF increases with increasing immersion time and B2O3 content. The largest increase in Ca content in the B100 glass containing solution is due to its faster dissolution rate. EDX/SEM analysis and FTIR showed precipitation of HA at all glass surfaces. B100 almost fully converted into HA after 168h in SBF. The addition of boron also decreases all characteristic temperatures due to the formation of Si-O-B bonds and planar [BO3] units. B50 possesses the largest hot working domain and also the crystallization peak with lower intensity. Therefore, this glass was selected for sintering experiments. Figure 1 shows a photograph of the sintered porous bodies obtained by sintering at 550, 575, 600 and 650oC for 1h. Samples sintered at 550 and 650oC were not further studied due to low mechanical properties and low porosity resepctively. The porosity varied from 1 (650oC) to 55% (575oC) with compression strength from 5 to 100Mpa. Scaffold from the glass B50 were also immersed in SBF and their mechanical properties slightly decrease with respect to immersion time. Figure 2 presents the live/dead staining images obtained at 14d. All glasses except B100 allow adhesion and proliferation of cells. However, with increasing boron content the proliferation of cells seems slightly reduced as compared to S53P4. Conclusion: Glass B50 was found to have good biocompatibility and thermal properties for hot working of BAG. The sintering temperature is rather low compared to sintering performed on commercial BAG. From the dissolution test, the addition of boron leads to a glass more prone to dissolution with higher conversion to HA, making this borosilicate glass system promising for use as scaffolds for tissue engineering. Academy of Finland

Bioactive glass fibers are attractive materials for use as tissue-engineering scaffolds and as the reinforcing phase for resorbable bioactive composites. The bioactivity of S520 glass fibers (52.0 mol % SiO(2), 20.9 Na(2)O, 7.1 K(2)O, 18.0 CaO, and 2.0 P(2)O(5)) was evaluated in two media, simulated body fluid (SBF) and Dulbecco's modified Eagle's medium (DMEM), for up to 20 days at 37 degrees C. Hydroxyapatite formation was observed on S520 fiber surfaces after 5 h in SBF. After a 20-day immersion, a continuous hydroxyapatite layer was present on the surface of samples immersed in SBF as well as on those samples immersed in DMEM [fiber surface area to solution volume ratio (SA:V) of 0.10 cm(2)/mL]. Backscattered electron imaging and EDS analysis revealed that the hydroxyapatite layer formation was more extensive for samples immersed in SBF. Decreasing the SA:V ratio to 0.05 cm(2)/mL decreased the time required to form a continuous hydroxyapatite surface layer. ICP was used to reveal Si, Ca, and P release profiles in DMEM after the 1st h (15.1, 83.8, and 29.7 ppm, respectively) were similar to those concentrations previously determined to stimulate gene expression in osteoblasts in vitro (16.5, 83.3, and 30.4 ppm, respectively). The tensile strength of the 20-microm diameter fibers was 925 +/- 424 MPa. Primary human osteoblast attachment to the fiber surface was studied by using SEM, and mineralization was studied by using alizarin red staining. Osteoblast dorsal ruffles, cell projections, and lamellipodia were observed, and by 7 days, cells had proliferated to form monolayer areas as shown by SEM. At 14 days, nodule formation was observed, and these nodules stained positive for alizarin red, demonstrating Ca deposition and, therefore mineralization.

It has been a major challenge to treat osteoporotic bone defects with irregular shapes. Although bioactive glass offers an attractive material for bone regeneration, its inherent brittleness has greatly limited its scope of application. Herein, we report the fabrication of bioactive glass (SiO2-CaO) nanofibers with excellent flexibility to even allow for 180° bending. The bioactive glass nanofibers could be further assembled into 3D fibrous scaffolds with chitosan serving as the linkers. The scaffolds constructed from an assembly of 85SiO2-15CaO nanofibers and chitosan (85SiO2-15CaO NF/CS) possessed significantly better mechanical properties when benchmarked against both 75SiO2-25CaO nanofiber- and chitosan-based scaffolds. Moreover, the 85SiO2-15CaO NF/CS scaffolds exhibited an elastic behavior, with full recovery from 80% compression and good fatigue resistance over 1000 cycles of compression under water. Upon implantation, the elastic fibrous scaffolds were able to deform and fit irregularly shaped bone defects, followed by a self-deploying behavior to achieve a perfect match with the cavities. When applied to the repair of an osteoporotic calvarial defect in a rat model, the 85SiO2-15CaO NF/CS scaffolds showed substantial promotion of bone regrowth and vascularization. This new class of 3D fibrous scaffold provides a promising advancement in engineering smart materials for complex bone repair.

Bioactive glasses have been used for many years in the human body as bone substitute. Since bioactive glasses are not readily available in the form of endless thin fibres with diameters below 20 µm, their use is limited to mainly non-load-bearing applications in the form of particles or granules. In this study, the spinnability of four bioactive silicate glasses was evaluated in terms of crystallisation behaviour, characteristic processing temperatures and viscosity determined by thermal analysis. The glass melts were drawn into fibres and their mechanical strength was measured by single fibre tensile tests before and after the surface treatment with different silanes. The degradation of the bioactive glasses was observed in simulated body fluid and pure water by recording the changes of the pH value and the ion concentration by inductively coupled plasma optical emission spectrometry; further, the glass degradation process was monitored by scanning electron microscopy. Additionally, first in vitro experiments using murine pre-osteoblast cell line MC3T3E1 were carried out in order to evaluate the interaction with the glass fibre surface. The results achieved in this work show up the potential of the manufacturing of endless bioactive glass fibres with appropriate mechanical strength to be applied as reinforcing fibres in new innovative medical implants.