Bioactive Glass Fibers Research Articles

Performance of Surface Immobilized RGDC 13–93 Bioactive Glass Fiber Rafts and Scaffolds with MLO-A5 Osteogenic Cells In Vitro

The aim of this study was to evaluate the ability of 13–93 bioactive glass constructs with surface immobilized peptide Arg-Gly-Asp-Cys (RGDC) to support the growth and differentiation of mouse MLO-A5 cells, an established osteogenic cell line. The construct types tested included 13–93 glass fiber rafts and fiber scaffolds possessing a surface with covalently bonded RGDC and seeded with MLO-A5 cells cultured for intervals up to 5 days. The RGDC treated rafts showed about a 3-fold higher cell attachment and about an 8-fold higher cell growth compared to control rafts. The RGDC treated scaffolds had an estimated 2-fold higher cell abundance than untreated control scaffolds. Protein measurements indicated a 1.6-fold higher level of cell growth on the RGDC coated scaffolds compared to controls during the incubation. Alkaline phosphatase activity, a key marker of osteoblast differentiation, was 2.3-fold higher at day 5 on RGDC scaffolds compared to controls. Collectively, the results indicate that the 13–93 glass fiber rafts and scaffolds with immobilized RGDC enhance the attachment, growth, and differentiation of MLO-A5 osteogenic cells and that bioactive glass scaffolds with biomimetic surfaces could potentially be effective for enhanced bone tissue engineering applications.

Reverse-biomineralization assembly of acid-sensitive biomimetic fibers for hard tissue engineering and drug delivery.

Biomimetic design and fabrication of tissue-engineered bone scaffolds that not only resemble natural bone in structure and performance, but also are endowed with specific functions, e.g., for drug delivery, are always an exciting research area. Herein, we report a kind of doxorubicin hydrochloride-loaded biomimetic ultrathin fiber, which is synthesized by preparing a kind of nanoporous bioactive glass fiber as a drug/protein carrier and bio-template and combining them in a reverse-biomineralization reaction. Protein adsorption experiments demonstrate that bovine serum albumin can be hosted in open large nanopores of bioactive glass fibers and the adsorption mechanism follows the intraparticle diffusion process. Biomineralization shows that proteins and drugs can be integrated at the nanoscale into minerals to form biomimetic and drug-loaded fibers, and the formation of such fibers depends on the functional ion (Ca, P, and Si) release of bioactive glass fibers and electrostatic interaction among bioactive glass fibers, proteins, and drugs. The drug-loaded composite fibers demonstrate bare homogeneous solid matrices in the fiber interior and surfaces upon which amorphous carbonated apatite resides. The drug release profiles show that the as-synthesized fibers are acid-sensitive and drugs can be released at pH 5, but not at neutral pH 7.4. Because of their structural advantages and the characteristics of acid-sensitive drug release, the biomimetic fibers have potential applications for repairing the bone defects resulting from tumour extirpation.

Bioactive Glass Cloth that Promotes New Bone Formation

A new composition of bioactive glass was proposed that can be drawn into fibers, woven into cloth, and has appropriate alkali-releasing ability for bioactivity. The glass was drawn into fibers and woven into cloth, then the biological efficacy of the cloth was examined in in vivo tests. Bone defects made in tibial bones of Wistar rats were covered with the cloth just like "bandage" for two weeks. The cloth was found to promote new bone formation in the bone defects without causing any adverse effects. In contrast, excessive infection was recognized and new bone was not formed when cloth made of E-glass fibers was used. This was the first successful demonstration that glass cloth made of bioactive glass fibers assisted bone regeneration. The present glass cloth, therefore, is expected to be a promising material for "bone bandage" or porous scaffolds for bone tissue regeneration.

Biological response of a recently developed nanocomposite based on calcium phosphate cement and sol–gel derived bioactive glass fibers as substitution of bone tissues

Calcium phosphate cements (CPCs) have been used in a number of medical and dental procedures due to their excellent osteoconductivity and bone replacement capability. However, the low mechanical properties of CPCs prohibit their usage in many unsupported defects and stress bearing locations. Bioactive glass fiber (BGF) reinforced-CPC with enhanced mechanical property has been recently developed [Nezafati et al. 2011, Ceramics International]. In the present study, the in vitro bioactivity and cellular properties of the CPC optimally reinforced with 15vol% BGFs were evaluated and compared with a control group, i.e. unreinforced CPC. The samples were soaked in simulated body fluid (SBF) for different time intervals and were then characterized by various techniques. Carbonate substituted apatite crystals with oriented plate-like morphology were also found on the surface of the samples. Furthermore, rat-derived osteoblastic cells were seeded on the samples for different times and evaluated in terms of proliferation, morphology and alkaline phosphatase (ALP) activity. In addition, the proliferation of osteoblastic cells on samples and increasing in level of alkaline phosphatase enzyme were observed as a function of time. The obtained results indicated that the reinforced composite made of CPC and BGFs could be considered as a highly bioactive material for bone tissue defect treatment after successful passage of in vivo experiments.

In vitro performance of 13‐93 bioactive glass fiber and trabecular scaffolds with MLO‐A5 osteogenic cells

This in vitro study was performed to evaluate the ability of two types of porous bioactive glass scaffolds to support the growth and differentiation of an established osteogenic cell line. The two scaffold types tested included 13-93 glass fiber and trabecular-like scaffolds seeded with murine MLO-A5 cells and cultured for intervals of 2 to 12 days. Culture in MTT-containing medium showed metabolically active cells both on the surface and within the interior of the scaffolds. Scanning electron microscopy revealed well-attached cells on both types of scaffolds with a continual increase in cell density over a 6-day period. Protein measurements also showed a linear increase in cell density during the incubation. Activity of alkaline phosphatase, a key indicator of osteoblast differentiation, increased about 10-fold during the 6-day incubation with both scaffold types. The addition of mineralization media to MLO-A5 seeded scaffolds triggered extensive formation of alizarin red-positive mineralized extracellular material, additional evidence of cell differentiation and completion of the final step of bone formation on the constructs. Collectively, the results indicate that the 13-93 glass fiber and trabecular scaffolds promote the attachment, growth, and differentiation of MLO-A5 osteogenic cells and could potentially be used for bone tissue engineering applications.

Effect of phosphate-based glass fibre surface properties on thermally produced poly(lactic acid) matrix composites

Incorporation of soluble bioactive glass fibres into biodegradable polymers is an interesting approach for bone repair and regeneration. However, the glass composition and its surface properties significantly affect the nature of the fibre-matrix interface and composite properties. Herein, the effect of Si and Fe on the surface properties of calcium containing phosphate based glasses (PGs) in the system (50P(2)O(5)-40CaO-(10-x)SiO(2)-xFe(2)O(3), where x = 0, 5 and 10 mol.%) were investigated. Contact angle measurements revealed a higher surface energy, and surface polarity as well as increased hydrophilicity for Si doped PG which may account for the presence of surface hydroxyl groups. Two PG formulations, 50P(2)O(5)-40CaO-10Fe(2)O(3) (Fe10) and 50P(2)O(5)-40CaO-5Fe(2)O(3)-5SiO(2) (Fe5Si5), were melt drawn into fibres and randomly incorporated into poly(lactic acid) (PLA) produced by melt processing. The ageing in deionised water (DW), mechanical property changes in phosphate buffered saline (PBS) and cytocompatibility properties of these composites were investigated. In contrast to Fe10 and as a consequence of the higher surface energy and polarity of Fe5Si5, its incorporation into PLA led to increased inorganic/organic interaction indicated by a reduction in the carbonyl group of the matrix. PLA chain scission was confirmed by a greater reduction in its molecular weight in PLA-Fe5Si5 composites. In DW, the dissolution rate of PLA-Fe5Si5 was significantly higher than that of PLA-Fe10. Dissolution of the glass fibres resulted in the formation of channels within the matrix. Initial flexural strength was significantly increased through PGF incorporation. After PBS ageing, the reduction in mechanical properties was greater for PLA-Fe5Si5 compared to PLA-Fe10. MC3T3-E1 preosteoblasts seeded onto PG discs, PLA and PLA-PGF composites were evaluated for up to 7 days indicating that the materials were generally cytocompatible. In addition, cell alignment along the PGF orientation was observed showing cell preference towards PGF.

Partially resorbable composite bone plate with controlled degradation rate, desired mechanical properties and bioactivity

Rate of polymer degradation is very important for implantable biomaterials since controlling the degradation rate may complement the biological response and affected mechanical property requirements. In spite of numerous publications on the potential use of combinations of poly lactic acid/bioactive glass fillers for degradable bone plate, little information exists on the controlling degradation rate and its effects on the other aspects such as biomechanical compatibility, bioactivity, etc. Our previous study revealed that a composite bone plate consist of poly l-lactic acid/braided bioactive glass fibers has the initial mechanical properties near to cortical bone. In this study, degradation rate and mechanical behavior of the composite bone plate were assessed, and also degradation rate was controlled by using proper manufacturing process and improving bonding between matrix and reinforcement. Moreover, bioactivity of the composite was considered before and after controlling degradation rate, because of the important role of bioactivity and ion release in healing acceleration. Results showed that degradation process of the composite could be controlled properly. Strength of the treated composite decreased only about 5% through 2 weeks and about 35% after 8 weeks while, the strength loss for the untreated composites was about 50 and 70 percent after 2 weeks and 8 weeks of degradation respectively. Although calcium-phosphate formation on the surface of the composite was postponed in the treated samples, the bioactivity of the composite remained unchanged and bone-like apatite was formed on the composite surface which is important for the application of the composite in bone tissue environment.

<i>In Vitro</i> Evaluations of a Mechanically Optimized Calcium Phosphate Cement as a Filler for Bone Repair<sup></sup>

Basic drawbacks of calcium phosphate cements (CPCs) are the brittleness and low strength behavior which prohibit their use in many stress-bearing locations, unsupported defects, or reconstruction of thin bones. Recently, to solve these problems, researchers investigated the incorporation of fibers into CPCs to improve their strength. In the present study, various amounts of a highly bioactive glass fiber were incorporated into calcium phosphate bone cement. The obtained results showed that the compressive strength of the set cements without any fibers optimally increased by further addition of the fiber phase. Also, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Herein, with the aim of using the reinforced-CPC as appropriate bone filler, the prepared sample was evaluated in vitro using simulated body fluid (SBF) and osteoblast cells. The samples showed significant enhancement in bioactivity within few days of immersion in SBF solution. Also, in vitro experiments with osteoblast cells indicated an appropriate penetration of the cells, and also the continuous increase in cell aggregation on the samples during the incubation time demonstrated the ability of the reinforced-CPC to support cell growth. Therefore, we concluded that this filler and strong reinforced-CPC may be beneficial to be used as bone fillers in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.

Submicron bioactive glass tubes for bone tissue engineering

Herein we describe a method to fabricate submicron bioactive glass tubes using sol–gel and coaxial electrospinning techniques for applications in bone tissue engineering. Heavy mineral oil and gel solution were delivered by two independent syringe pumps during the coaxial electrospinning process. Subsequently, submicron bioactive glass tubes were obtained by removal of poly(vinyl pyrrolidone) and heavy mineral oil via calcination at 600 °C for 5 h. Tubular structure was confirmed by scanning electron microscopy and transmission electron microscopy imaging. We examined the bioactivity of submicron bioactive glass tubes and fibers and evaluated their biocompatibility, using electrospun poly(ε-caprolactone) fibers – a bioinactive material – for comparison. The bioactivity of the glass tubes was examined in a simulated body fluid and they demonstrated the formation of hydroxyapatite-like minerals on both the outer and inner surfaces. In contrast, mineralization only occurred on their surface for bioactive glass solid fibers. Energy-dispersive X-ray data suggested that the bioactive glass tubes had a faster induction of mineral formation than the solid fibers. We demonstrate that the proliferation rate of mouse preosteoblastic MC3T3-E1 cells on bioactive glass tubes was comparable to that on solid fibers. We also show that bioactive glass tubes can be loaded with a model protein drug, bovine serum albumin, and that these structures exhibit delayed release properties. The bioactivity of released lysozyme can be as high as 90.9%. Taken together, these data suggest that submicron bioactive glass tubes could hold great potential for use in bone tissue engineering as well as topical drug or gene delivery.

Synergistically reinforcement of a self-setting calcium phosphate cement with bioactive glass fibers

Calcium phosphate cements (CPCs) are highly promising for clinical uses due to their in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits their uses to non-load-bearing applications. In the present research, first, bioactive glass fibers (BGFs) in the ternary SiO2–CaO–P2O5 system were prepared, and then the fiber composites with compositions based on CPC and BGFs were prepared and characterized. Then, the effect of structure and amount of BGF incorporation into the CPC system, and the effect of mechanical compaction on the fiber-modified system were investigated. The results showed that the compressive strength of the set cements without any BGFs was 0.635MPa which was optimally increased to 3.69MPa by applying 15% BGF and then decreased by further addition of it. In addition, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Also, the setting time slightly decreased by applying the fibers. In summary, processing parameters were tailored to achieve optimum mechanical properties and strength. The prepared composite may be useful in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.

Enhanced osteoblastic activity and bone regeneration using surface‐modified porous bioactive glass scaffolds

The potential use as a bone substitute material of a three-dimensional bioactive glass fiber scaffold composed of Na(2)O-K(2)O-MgO-CaO-B(2)O(3)-P(2)O(5)-SiO(2) (BG1) was investigated in this work. Scaffolds were pre-treated with simulated body fluid (SBF) to promote the formation of two different bone-like apatite layers on their surfaces. The topography and roughness of the deposited layers were assessed by scanning electron microscopy (SEM), while the chemical composition and structure using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, respectively. Based on surface analysis, the bioactive glass surfaces were ranked from smoothest to roughest: 0 SBF (untreated), 1x SBF and 2x SBF. A calcium-deficient carbonated hydroxyapatite (HCA) layer was present on both SBF-treated scaffolds, with higher number and larger bone-like apatite nodule formation in the 2x SBF case. MC3T3-E1 preosteoblasts showed a more flattened morphology and higher cell proliferation on the nontreated scaffolds; whereas, cells were more elongated and had higher osteoblastic activity on SBF-treated samples. In vivo results in a rabbit calvarial bone defect model showed enhanced bone formation with SBF pretreated scaffolds, compared with untreated ones, commercially available Perioglass particles and empty defects. Our findings demonstrate that the formation of a rough HCA layer on bioactive glass porous scaffolds enhanced preosteoblast maturation in vitro, as well as bone formation in vivo.

Fabrication and Drug Delivery of Ultrathin Mesoporous Bioactive Glass Hollow Fibers

AbstractUltrathin mesoporous bioactive glass hollow fibers (MBGHFs) fabricated using an electrospinning technique and combined with a phase‐separation‐induced agent, poly(ethylene oxide) (PEO), are described. The rapid solvent evaporation during electrospinning and the PEO‐induced phase separation process demonstrated play vital roles in the formation of ultrathin bioactive glass fibers with hollow cores and mesoporous walls. Immersing the MBGHFs in simulated body fluid rapidly results in the development of a layer of enamel‐like apatite mesocrystals at the fiber surfaces and apatite nanocrystals inside the hollow cores. Drug loading and release experiments indicate that the drug loading capacity and drug release behavior of the MBGHFs strongly depends on the fiber length. MBGHFs with fiber length >50 µm can become excellent carriers for drug delivery. The shortening of the fiber length reduces drug loading amounts and accelerates drug release. The MBGHFs reported here with sophisticated structure, high bioactivity, and good drug delivery capability can be a promising scaffold for hard tissue repair and wound healing when organized into 3D macroporous membranes.

In vivo testing of a biodegradable woven fabric made of bioactive glass fibers and PLGA80—A pilot study in the rabbit

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, Bioactivity, and Drug Release of Hierarchical Nanoporous Bioactive Glass Ultrathin Fibers

Hierarchical nanoporous bioactive glass ultrathin fibers with different pore diameters from 1.5-nm micropores up to 65-nm macropores are synthesized using P123–PEO co-templates and an electrospinning technique (see image). Experiments demonstrate that the prepared bioactive glass fibers are highly homogenous and bioactive and their nanopores can control drug release well.

Electrospun submicron bioactive glass fibers for bone tissue scaffold

Submicron bioactive glass fibers 70S30C (70 mol% SiO(2), 30 mol% CaO) acting as bone tissue scaffolds were fabricated by electrospinning method. The scaffold is a hierarchical pore network that consists of interconnected fibers with macropores and mesopores. The structure, morphological characterization and mechanical properties of the submicron bioactive glass fibers were studied by XRD, EDS, FIIR, SEM, N(2) gas absorption analyses and nanoindentation. The effect of the voltage on the morphology of electrospun bioactive glass fibers was investigated. It was found that decreasing the applied voltage from 19 to 7 kV can facilitate the formation of finer fibers with fewer bead defects. The hardness and Young's modulus of submicron bioactive glass fibers were measured as 0.21 and 5.5 GPa, respectively. Comparing with other bone tissue scaffolds measured by nanoindentation, the elastic modulus of the present scaffold was relatively high and close to the bone.

Development of a bioactive glass fiber reinforced starch–polycaprolactone composite

For bone regeneration and repair, combinations of different materials are often needed. Biodegradable polymers are often combined with osteoconductive materials, such as bioactive glass (BaG), which can also improve the mechanical properties of the composite. The aim of this work was to develop and characterize BaG fiber reinforced starch-poly-epsilon-caprolactone (SPCL) composite. Sheets of SPCL (30/70 wt %) were produced using single-screw extrusion. They were then cut and compression-molded in layers with BaG fibers to form composite structures with different combinations. Mechanical and degradation properties of the composites were studied. The actual amount of BaG in the composites was determined using combustion tests. Initial mechanical properties of the reinforced composites were at least 50% better than the properties of the nonreinforced specimens. However, the mechanical properties of the composites after 2 weeks of hydrolysis were comparable to those of the nonreinforced samples. During the 6 weeks hydrolysis the mass of the composites had decreased only by about 5%. The amount of glass in the composites remained as initial for the 6-week period of hydrolysis. In conclusion, it is possible to enhance initial mechanical properties of SPCL by reinforcing it with BaG fibers. However, mechanical properties of the composites are typical for bone fillers and strength properties need to be further improved for allowing more demanding bone applications.

Mechanical verification of soft-tissue attachment on bioactive glasses and titanium implants

Soft-tissue attachment is a desired feature of many clinical biomaterials. The aim of the current study was to design a suitable experimental method for tensile testing of implant incorporation with soft-tissues. Conical implants were made of three compositions of bioactive glass (SiO 2–P 2O 5–B 2O 3–Na 2O–K 2O–CaO–MgO) or titanium fiber mesh (porosity 84.7%). The implants were surgically inserted into the dorsal subcutaneous soft-tissue or back muscles in the rat. Soft-tissue attachment was evaluated by pull-out testing using a custom-made jig 8 weeks after implantation. Titanium fiber mesh implants had developed a relatively high pull-out force in subcutaneous tissue (12.33 ± 5.29 N, mean ± SD) and also measurable attachment with muscle tissue (2.46 ± 1.33 N). The bioactive glass implants failed to show mechanically relevant soft-tissue bonding. The experimental set-up of mechanical testing seems to be feasible for verification studies of soft-tissue attachment. The inexpensive small animal model is beneficial for large-scale in vivo screening of new biomaterials.

Preparation and Characterization of the Sol-Gel Derived Bioactive Glass-Fibers

The sol-gel derived bioactive glass short fibers in the system CaO-P2O5-SiO2 was prepared using air-spray method. SBF immersion test indicated that the fibers possessed satisfactory bioactivity. SEM, XRD, FTIR analysis revealed that the morphologies and bioactivity of the fibers could be significantly influenced by the composition and viscosity of the solution. The fibers are very promising biomaterials for applications to bone restoration and tissue engineering as the bone defects fillers or additives for strengthening of the biomedical polymers.

Sol–gel derived mesoporous bioactive glass fibers as tissue-engineering scaffolds

Mesoporous bioactive glass (MBG) fibers have been synthesized using the combination of a sol–gel process and a high velocity spray procedure by carefully controlling the sol composition, acidity and water content. A three-dimensional (3D) macro-structure with ∼50–100 μm interconnected macropores is formed in the spraying process. The MBG fibers possess well-ordered hexagonal mesostructure and excellent in vitro bioactivities. Sprague–Dawley (SD) rat osteoblasts have been cultured on MBG fibers. It is found that the MBG fibers have good cell biocompatibility and the 3D macro-structure is beneficial for cell attachment. It is anticipated that MBG fibers with controlled mesostructure and excellent in vitro bioactivity are good candidates for future tissue-engineering scaffolds.

Growth and differentiation of osteoblastic cells on 13–93 bioactive glass fibers and scaffolds

This in vitro study was conducted to evaluate the ability of two types of constructs of bioactive, silica-based 13–93 glass fibers to support the growth and differentiation of MC3T3-E1 osteoblastic cells. The two types of constructs tested included single-layer 13–93 glass fiber rafts and three-dimensional porous scaffolds formed from sintered 13–93 fibers. Scanning electron micrographs showed a closely adhering, well-spread morphology of MC3T3-E1 cells seeded on both types of constructs. The scanning electron microscopy images also showed a continuous increase in cell densities during a 6 day incubation on 13–93 glass fiber rafts and scaffolds. Quantitative fluorescence measurements of DNA also revealed a linear increase in cell density during a 6 day incubation on both types of 13–93 constructs. Examination of scaffolds incubated in MTT containing medium showed the presence of metabolically active viable cells within the interior of the scaffold. The addition of ascorbic acid to MC3T3-E1 cells cultured on the 13–93 glass fibers triggered a threefold increase in alkaline phosphatase, a key indicator of osteoblast differentiation. The sintered scaffolds were found to have open, interconnected pores favorable for tissue ingrowth with a compressive strength similar to cancellous bone. Collectively, the results indicate that 13–93 glass fiber scaffolds are a favorable substrate for the growth and differentiation of osteoblasts and a promising material for bone tissue engineering and repair of bone defects.