Glass Scaffolds Research Articles

Bioactivation of titanium dioxide scaffolds by ALP-functionalization

Three dimensional TiO2 scaffolds are receiving renewed attention for bone tissue engineering (TE) due to their biocompatibility and attractive mechanical properties. However the bioactivity of these scaffolds is comparatively lower than that of bioactive glass or hydroxyapatite (HA) scaffolds. One strategy to improve bioactivity is to functionalize the surface of the scaffolds using biomolecules. Alkaline phosphatase (ALP) was chosen in this study due to its important role in the bone mineralization process. The current study investigated the ALP functionalization of 3D titanium dioxide scaffolds using self-polymerization of dopamine. Robust titanium scaffolds (compressive strength∼2.7 ± 0.3 MPa) were produced via foam replica method. Enzyme grafting was performed by dip-coating in polydopamine/ALP solution. The presence of ALP was indirectly confirmed by contact angle measurements and enzymatic activity study. The influence of the enzyme on the bioactivity, e.g. hydroxyapatite formation on the scaffold surface, was measured in simulated body fluid (SBF). After 28 days in SBF, 5 mg ALP coated titania scaffolds exhibited increased hydroxyapatite formation. It was thus confirmed that ALP enhances the bioactivity of titania scaffolds, converting an inert bioceramic in an attractive bioactive system for bone TE.

Finite element method simulation for the prediction of mechanical properties of three-dimensional periodic bioactive glass scaffolds

The desired mechanical properties of porous tissue engineering scaffolds may differ depending on the clinical applications. Therefore, it is crucial to be able to control these properties for specific cases. In the current study, cube shape, porous, silicate-based (13-93) bioactive glass scaffolds were fabricated by robotic deposition method. Scaffolds were prepared layer by layer to form constructs with a grid-like microstructure. After binder burnout, the constructs were sintered for 1 h at 700 °C to produce scaffolds consisting of dense bioactive glass struts (∼280 ± 20 μm in diameter) at different pore widths (300 ± 50, 600 ± 25, and 900 ± 50 μm). The mechanical response of the scaffolds in compression was measured experimentally. The stress analysis of the complete scaffolds with varying pore width and layer spacing parameters has been performed by finite element method (FEM) under compression to investigate the state of stress fields created within the scaffolds. Such an analysis can be used to vary several geometrical parameters and to choose the most suitable ones for the replacement of natural tissues. The compressive strengths predicted by the FEM simulations were successfully validated by comparison with experimental uniaxial compression test data, justifying the suitability of the present approach for the optimization purposes.

Preparation, structural characterization, and in vitro cell studies of three-dimensional SiO2–CaO binary glass scaffolds built ofultra-small nanofibers

Three-dimensional (3D) nanofibrous scaffolds hold great promises in tissue engineering and regenerative medicine. In this work, for the first time, 3D SiO2–CaO binary glass nanofibrous scaffolds have been fabricated via a combined method of template-assisted sol-gel and calcination by using bacterial cellulose as the template. SEM with EDS, TEM, and AFM confirm that the molar ratio of Ca to Si and fiber diameter of the resultant SiO2–CaO nanofibers can be controlled by immersion time in the solution of tetraethyl orthosilicate and ethanol. The optimal immersion time was 6h which produced the SiO2–CaO binary glass containing 60at.% Si and 40at.% Ca (named 60S40C). The fiber diameter of 60S40C scaffold is as small as 29nm. In addition, the scaffold has highly porous 3D nanostructure with dominant mesopores at 10.6nm and macropores at 20μm as well as a large BET surface area (240.9m2g−1), which endow the 60S40C scaffold excellent biocompatibility and high ALP activity as revealed by cell studies using osteoblast cells. These results suggest that the 60S40C scaffold has great potential in bone tissue regeneration.

Processing and in vitro bioactivity of high-strength 45S5 glass-ceramic scaffolds for bone regeneration

In this paper, the compressive strength and in vitro bioactivity of sintered 45S5 bioactive glass scaffolds produced by powder technology and polymer foaming were investigated. The sintering temperature of scaffolds was 975°C. The characterization of scaffolds before immersion in SBF was performed by scanning electron microscopy (SEM) and microtomography (μCT). The scaffolds were also tested for compression, and their density and porosity were measured. After immersion, the samples were observed through SEM and analyzed using EDS, X-ray diffraction (XRD), and infrared spectroscopy (FT-IR). Mass variation was also estimated. The glass-ceramic scaffolds showed a 61.44±3.13% interconnected porosity and an average compressive strength of 13.78±2.43MPa. They also showed the formation of a hydroxyapatite layer after seven days of immersion in SBF, demonstrating that partial crystallization during sintering did not suppress their bioactivity.

Setd2 is associated with strontium-induced bone regeneration.

Our research group recently demonstrated that the combination of MBG scaffolds with Sr, efficiently promoted bone regeneration in rat femoral defects even in severely compromised osteoporotic animals, however, the epigenetic mechanism by which Sr ions function to promote bone generation remains unclear. This study showed an increased expression and affiliation of Setd2 and H3K36me3. In vitro, the increased expression of Setd2 promoted osteoblastic differentiation of MG63 stimulated by SrCl2 in MAPK-dependent way, which activated ERK in turn leading to a positive feedback. Based on these findings, it was shown that Setd2 has an active role in osteoblast differentiation and may also turn to be an epigenetic target for new treatment options of osteoporosis and the development of novel bone regeneration scaffold.

Three dimensional printing of calcium sulfate and mesoporous bioactive glass scaffolds for improving bone regeneration in vitro and in vivo

In the clinic, bone defects resulting from infections, trauma, surgical resection and genetic malformations remain a significant challenge. In the field of bone tissue engineering, three-dimensional (3D) scaffolds are promising for the treatment of bone defects. In this study, calcium sulfate hydrate (CSH)/mesoporous bioactive glass (MBG) scaffolds were successfully fabricated using a 3D printing technique, which had a regular and uniform square macroporous structure, high porosity and excellent apatite mineralization ability. Human bone marrow-derived mesenchymal stem cells (hBMSCs) were cultured on scaffolds to evaluate hBMSC attachment, proliferation and osteogenesis-related gene expression. Critical-sized rat calvarial defects were applied to investigate the effect of CSH/MBG scaffolds on bone regeneration in vivo. The in vitro results showed that CSH/MBG scaffolds stimulated the adhesion, proliferation, alkaline phosphatase (ALP) activity and osteogenesis-related gene expression of hBMSCs. In vivo results showed that CSH/MBG scaffolds could significantly enhance new bone formation in calvarial defects compared to CSH scaffolds. Thus 3D printed CSH/MBG scaffolds would be promising candidates for promoting bone regeneration.

Rapid vacuum sintering: A novel technique for fabricating fluorapatite ceramic scaffolds for bone tissue engineering.

Macroporous bioceramic scaffolds are often fabricated via the foam replica technique, based on polymeric foam impregnation with a glass slurry, followed by slow heat treatment to allow for drying, polymeric burnout, and sintering of the glass particles. As a consequence, the process is time consuming and complicated by concurrent crystallization of the glass, often leading to incomplete sintering. Our goal was to investigate the effect of heating rate on sintering behavior, architecture, and mechanical properties of fluorapatite-based glass and glass-ceramic scaffolds. Glass scaffolds were prepared and sintered by rapid vacuum sintering (RVS) at 785°C under vacuum at a fast heating rate (55°C/min.) or without vacuum at a slow heating rate (2°C/min.). Two additional groups were further crystallized at 775°C/1 h. XRD confirmed the presence of fluorapatite for crystallized scaffolds. All groups presented interconnected porosity with a pore size in the 500 μm range. Scaffolds produced by RVS exhibited an excellent degree of sintering while scaffolds produced by slow sintering were incompletely sintered. The mean compressive strength was significantly higher for the RVS groups (1.52 ± 0.55 and 1.72 ± 0.61 MPa) compared to the slow-sintered groups (0.54 ± 0.30 and 0.45 ± 0.26 MPa). Meanwhile, the total production time was reduced by more than 12 h by using the RVS technique. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 291-299, 2018.

Tough and strong porous bioactive glass-PLA composites for structural bone repair.

Bioactive glass scaffolds have been used to heal small contained bone defects but their application to repairing structural bone is limited by concerns about their mechanical reliability. In the present study, the addition of an adherent polymer layer to the external surface of strong porous bioactive glass (13-93) scaffolds was investigated to improve their toughness. Finite element modeling (FEM) of the flexural mechanical response of beams composed of a porous glass and an adherent polymer layer predicted a reduction in the tensile stress in the glass with increasing thickness and elastic modulus of the polymer layer. Mechanical testing of composites with structures similar to the models, formed from 13-93 glass and polylactic acid (PLA), showed trends predicted by the FEM simulations but the observed effects were considerably more dramatic. A PLA layer of thickness -400 µm, equal to -12.5% of the scaffold thickness, increased the load-bearing capacity of the scaffold in four-point bending by ~50%. The work of fracture increased by more than 10,000%, resulting in a non-brittle mechanical response. These bioactive glass-PLA composites, combining bioactivity, high strength, high work of fracture and an internal architecture shown to be conducive to bone infiltration, could provide optimal implants for healing structural bone defects.

Reinforcement with reduced graphene oxide of bioactive glass scaffolds fabricated by robocasting

45S5 bioactive glass composite scaffolds reinforced with reduced graphene oxide (rGO) were fabricated for the first time by robocasting (direct-writing) technique. Composite scaffolds with 0–3vol.% content of rGO platelets were printed, and then consolidated by pressureless sintering at 550 or 1000°C in Ar atmosphere. It was found that the addition of rGO platelets up to 1.5vol.% content enhanced the mechanical performance of the 45S5 bioactive glass scaffolds in terms of strength and toughness. Best performance was obtained for 1vol.% rGO, which yielded an enhancement of the fracture toughness of ∼850 and 380% for sintering temperatures of 550 and 1000°C, respectively, while the compressive strength increased by ∼290 and 75%. rGO addition thus emerges as a promising approach for the fabrication of novel bioglass scaffolds with improved mechanical performance without deterioration of their bioactivity, which may then find use in load-bearing bone tissue engineering applications.

A 3D graphene coated bioglass scaffold for bone defect therapy based on the molecular targeting approach.

Development of a cell-free scaffold with excellent mechanical properties and osteoconductivity is of significant need for bone regeneration. Herein, a reduced graphene oxide (rGO) functionalized hierarchical macro-mesoporous bioactive glass scaffold integrated with an osteoblast-specific aptamer is rationally designed to recruit and induce the rapid differentiation of osteoblasts for bone regeneration. This scaffold exhibits a macroporous structure with fully interconnected open pores and shows excellent mechanical properties with a Young's modulus of ∼80 kPa, which provides a strong scaffold to support the growth of osteoblasts and bone tissue regeneration. Furthermore, the scaffold displays good performance in accelerating osteoblast differentiation and promoting new bone formation. The osteoblast recruitment is achieved since the osteoblast-specific aptamer can specifically target osteoblasts with strong binding affinity. Micro-computed tomography and histological tests confirmed that the large bone defects fully heal with new plate-like-pattern bone appearing both peripherally and centrally, suggesting the outstanding bone regeneration performance of this cell-free and graphene functionalized scaffold. Considering the promising bioapplications of the graphene functionalized bioactive glass scaffold with osteoblast recruitment capacity, our strategy paves a way for the design of new bioactive functional materials for tissue regeneration and shows attractive prospects in targeted therapy.

Freeform extrusion fabrication of titanium fiber reinforced 13–93 bioactive glass scaffolds

Although implants made with bioactive glass have shown promising results for bone repair, their application in repairing load-bearing long bone is limited due to their poor mechanical properties in comparison to human bone. This work investigates the freeform extrusion fabrication of bioactive silicate 13–93 glass scaffolds reinforced with titanium (Ti) fibers. A composite paste prepared with 13–93 glass and Ti fibers (~16µm in diameter and lengths varying from ~200µm to ~2 mm) was extruded through a nozzle to fabricate scaffolds (0–90° filament orientation pattern) on a heated plate. The sintered scaffolds measured pore sizes ranging from 400 to 800µm and a porosity of ~50%. Scaffolds with 0.4vol% Ti fibers measured fracture toughness of ~0.8MPam1/2 and a flexural strength of ~15MPa. 13–93 glass scaffolds without Ti fibers had a toughness of ~0.5MPam1/2 and a strength of ~10MPa. The addition of Ti fibers increased the fracture toughness of the scaffolds by ~70% and flexural strength by ~40%. The scaffolds’ biocompatibility and their degradation in mechanical properties in vitro were assessed by immersing the scaffolds in a simulated body fluid over a period of one to four weeks.

Investigation of in vitro mineralization of silicate-based 45S5 and 13-93 bioactive glasses in artificial saliva for dental applications

Bioactive glasses are important class of materials that have a wide range of applications in tissue engineering and dentistry. In dental tissue engineering, nanofibrous structures exhibit interesting features, such as high surface area, surface functionalization and porosity. In this study, silicate-based 45S5 and 13-93 bioactive glass fibers were fabricated using electrospinning technique and their in vitro mineralization behavior was investigated in two different artificial saliva solutions for various time intervals. Results revealed that both 45S5 and 13-93 bioactive glass fibers show high mineralization behavior in artificial saliva solutions. However different hydroxyapatite (HA) formation rates were observed depending on the glass type and the artificial saliva composition. HA formation initiated earlier in 45S5 glass fibers treated in artificial saliva compared to 13-93 glass. On the other hand, after 30 days of treatment, the surface of 13-93 glass fibers converted to pure crystalline HA, whereas, 45S5 glass surface contained some additional crystalline phases such as aragonite and calcite. Treatment in SAGF medium resulted with better HA conversion ability compared to Carter-Brugirard saliva for both types of glass fibers. In conclusion, the use of electrospun nanofibrous 45S5 and 13-93 bioactive glass scaffolds could be one approach suitable to dental applications.

P21 Three-dimensional polymer coated 45S5-type bioactive glass scaffolds seeded with human mesenchymal stem cells show bone formation in-vivo

P21 Three-dimensional polymer coated 45S5-type bioactive glass scaffolds seeded with human mesenchymal stem cells show bone formation in-vivo

Influence of single and binary doping of strontium and lithium on in vivo biological properties of bioactive glass scaffolds

Effects of strontium and lithium ion doping on the biological properties of bioactive glass (BAG) porous scaffolds have been checked in vitro and in vivo. BAG scaffolds were prepared by conventional glass melting route and subsequently, scaffolds were produced by evaporation of fugitive pore formers. After thorough physico-chemical and in vitro cell characterization, scaffolds were used for pre-clinical study. Soft and hard tissue formation in a rabbit femoral defect model after 2 and 4 months, were assessed using different tools. Histological observations showed excellent osseous tissue formation in Sr and Li + Sr scaffolds and moderate bone regeneration in Li scaffolds. Fluorochrome labeling studies showed wide regions of new bone formation in Sr and Li + Sr doped samples as compared to Li doped samples. SEM revealed abundant collagenous network and minimal or no interfacial gap between bone and implant in Sr and Li + Sr doped samples compared to Li doped samples. Micro CT of Li + Sr samples showed highest degree of peripheral cancellous tissue formation on periphery and cortical tissues inside implanted samples and vascularity among four compositions. Our findings suggest that addition of Sr and/or Li alters physico-chemical properties of BAG and promotes early stage in vivo osseointegration and bone remodeling that may offer new insight in bone tissue engineering.

Tailoring Mechanical Properties of Sol–Gel Hybrids for Bone Regeneration through Polymer Structure

Bioglass was the first synthetic biomaterial that formed a chemical bond to bone. Although bioactive glass scaffolds can mimic bone’s porous structure, they are brittle. Sol–gel derived hybrids could overcome this problem because their nanoscale conetworks of silica and organic polymer have the potential to provide unique physical properties and controlled homogeneous biodegradation. Copolymers of methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) have been used as an organic source for hybrids to take advantage of their self-hardening property. However, the effect of well-defined poly(MMA-co-TMSPMA) architecture in the hybrid system has not been investigated. Here, linear, randomly branched, and star shaped methacrylate based copolymers were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization method. These copolymers were then used to fabricate hybrids. The 3-D polymer structure had a significant effect on mechanical properties, providing high...

Bioactive/Natural Polymeric Scaffolds Loaded with Ciprofloxacin for Treatment of Osteomyelitis.

Local delivery of antibiotic into injured bone is a demand. In this work, different scaffolds of chitosan (C) with or without bioactive glass (G) were prepared using the freeze-drying technique in 2:1, 1:1, and 1:2 weight ratios. Chitosan scaffolds and selected formulas of chitosan to bioglass were loaded with ciprofloxacin in 5%, 10%, and 20% w/w. Scaffold morphology showed an interconnected porous structure, where the glass particles were homogeneously dispersed in the chitosan matrix. The kinetic study confirmed that the scaffold containing 1:2 weight ratio of chitosanto glass (CG12) showed optimal bioactivity with good compromise between Ca and P uptake capacities and Si release rate. Chitosan/bioactive glass scaffolds showed larger t 50 values indicating less burst drug release followed by a sustained drug release profile compared to that of chitosan scaffolds. The cell growth, migration, adhesion, and invasion were enhanced onto CG12 scaffold surfaces. Samples of CG12 scaffolds with or without 5% drug induced vascular endothelial growth factor (VEGF), while those containing 10% drug diminished VEGF level. Only CG12 induced the cell differentiation (alkaline phosphatase activity). In conclusion, CG12 containing 5% drug can be considered a biocompatible carrier which would help in the localized osteomyelitis treatment.

Improvement in degradability of 58s glass scaffolds by ZnO and β-TCP modification

ABSTRACT58s bioactive glass shows great potential for bone defects repair. However, at early repairing stage, the degradation rate of 58s glass is too fast due to the fast ion-exchange. At later repairing stage, the degradation rate of 58s glass is too slow due to the high dense mineral layer. In this work, Zinc oxide (ZnO) and β-tricalcium phosphate (β-TCP) were introduced into 58s glass bone scaffolds to improve the degradability. The results showed that ZnO could decrease the degradation rate and promote the stability of 58s glass at early repairing stage. Moreover, the presence of β-TCP appeared to increase the degradation rate at a later stage of repairing. Furthermore, in vitro biocompatibility study, carried out using human osteoblast-like cells (MG63), demonstrated that ZnO and β-TCP enhanced cell attachment and proliferation. The study provided a reference for further research in bone tissue engineering.

Bioglass in Alveolar Bone Regeneration in Orthodontic Patients: Randomized Controlled Clinical Trial.

This study was designed as a split-mouth randomized controlled clinical trial to evaluate the effects of a novel bioactive glass scaffold-tailored amorphous multiporous (TAMP)-for the preservation of alveolar bone following tooth extraction in class II orthodontic patients. TAMP scaffolds were prepared and sterilized. Patients were screened for eligibility, and 6 patients accounting for 14 extraction sockets were included in this stage. Sockets were randomly allocated to either control (left empty) or test (grafted with TAMP scaffold particles). Follow-up was done after 1, 2, 4, 8, and 12 to 17 wk with digital periapical radiographs to evaluate changes in crestal bone height and bone mineral density (BMD), 3-dimensional volumetric analysis of impression casts, and histologic analysis of core biopsies. Furthermore, alveolar bone marrow mesenchymal stem cells were cultured from control and test sockets following biopsy retrieval to evaluate the ability of TAMP bioactive glass scaffolds to recruit host progenitor cells. Results showed that sockets grafted with TAMP bioactive glass scaffolds better preserved height after 3 mo where mesially 57.1% of test cases showed preservation of socket height, compared with 28.6% of control cases. Distally, this was 42.9% of test cases versus none of the control cases. Regarding BMD, the test sides had higher BMD in all 3 sections of the socket, with the greatest reduction in BMD found in the coronal third. Results were not statistically significant. Histologically, sockets grafted with TAMP bioactive glass scaffolds showed a distinct pattern of bone healing characterized by vertical trabeculae and large vascularized marrow spaces with sockets showing corticalization. Volumetric analysis showed a better preservation of socket contour with TAMP bioactive glass scaffolds. TAMP bioactive glass scaffolds appeared to enhance the recruitment of stem cells from the grafted sockets. In conclusion, TAMP scaffolds appear to better preserve alveolar bone following extraction and allow for a more active bone modeling and remodeling process( ClinicalTrials.gov identifier:NCT01878084). Knowledge Transfer statement: The results of this study set the stage for the recommended use of novel biomimetic scaffolds, such as the tailored amorphous multiporous bioactive glass for preservation of the socket following extraction. This can be valuable for patients and clinicians alike when deciding on long-term prosthetic alternatives that not only result in immediate bone preservation but will accommodate the dynamic nature of bone.

Micro-CT Analysis of Bone Healing in Rabbit Calvarial Critical-Sized Defects with Solid Bioactive Glass, Tricalcium Phosphate Granules or Autogenous Bone.

ABSTRACTObjectivesThe purpose of the present study was to evaluate bone healing in rabbit critical-sized calvarial defects using two different synthetic scaffold materials, solid biodegradable bioactive glass and tricalcium phosphate granules alongside solid and particulated autogenous bone grafts.Material and MethodsBilateral full thickness critical-sized calvarial defects were created in 15 New Zealand white adult male rabbits. Ten defects were filled with solid scaffolds made of bioactive glass or with porous tricalcium phosphate granules. The healing of the biomaterial-filled defects was compared at the 6 week time point to the healing of autologous bone grafted defects filled with a solid cranial bone block in 5 defects and with particulated bone combined with fibrin glue in 10 defects. In 5 animals one defect was left unfilled as a negative control. Micro-computed tomography (micro-CT) was used to analyze healing of the defects.ResultsMicro-CT analysis revealed that defects filled with tricalcium phosphate granules showed new bone formation in the order of 3.89 (SD 1.17)% whereas defects treated with solid bioactive glass scaffolds showed 0.21 (SD 0.16)%, new bone formation. In the empty negative control defects there was an average new bone formation of 21.8 (SD 23.7)%.ConclusionsAccording to findings in this study, tricalcium phosphate granules have osteogenic potential superior to bioactive glass, though both particulated bone with fibrin glue and solid bone block were superior defect filling materials.

Characteristics and Effects on Dental Pulp Cells of a Polycaprolactone/Submicron Bioactive Glass Composite Scaffold

IntroductionThis study aimed to evaluate the potential applications of polycaprolactone (PCL)/submicron bioactive glass (smBG) hybrid composites for pulp and dentin tissue regeneration. MethodsPCL/smBG hybrid composites were made with novel monodispersive bioactive glass submicrospheres, and pure PCL and bioactive glass samples were used as controls. Surface characteristics were assessed by scanning electron microscopy. Crystalline apatite deposition in vitro was examined after incubation in simulated body fluid. Inductively coupled plasma spectroscopy was used to further analyze the concentration of Si ions released by the scaffolds. Cell adhesion and morphology of human dental pulp cells were observed by immunofluorescence staining. The proliferation and expression of odontogenic-related markers were subsequently investigated using the Cell Counting Kit-8 assay (Beyotime Institute of Biotechnology, Jiangsu, China), Western blotting, and real-time reverse-transcription polymerase chain reaction. Mineralization activity was assessed by alizarin red staining. ResultsCrystalline apatites were precipitated on the PCL/smBG hybrid and pure bioactive glass surfaces after incubation in vitro, and pure PCL did not exhibit precipitation. Surface deposition on PCL/smBG hybrids presented different topographies and was thicker than on pure bioactive glass scaffolds at a later stage. Human dental pulp cells had a significantly higher proliferation rate on the PCL/smBG hybrid than on the bioactive glass and PCL scaffolds. Furthermore, the integration of smBG into the hybrid scaffold significantly promoted the expression of markers for odontogenic differentiation. More mineralized nodules were generated in the PCL/smBG group than in the other 2 groups. ConclusionsPCL/smBG hybrid composites may serve as potential material for pulp repair and dentin regeneration. The physical and chemical properties of the bioactive glass component affect the bioactivity of hybrid composites.