Silica-Based Bioactive Glasses and Their Applications in Hard Tissue Regeneration: A Review (original) (raw)
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Bioactive glass in tissue engineering
Acta Biomaterialia, 2011
This review focuses on recent advances in the development and use of bioactive glass for tissue engineering applications. Despite its inherent brittleness, bioactive glass has several appealing characteristics as a scaffold material for bone tissue engineering. New bioactive glasses based on borate and borosilicate compositions have shown the ability to enhance new bone formation when compared to silicate bioactive glass. Borate-based bioactive glasses also have controllable degradation rates, so the degradation of the bioactive glass implant can be more closely matched to the rate of new bone formation. Bioactive glasses can be doped with trace quantities of elements such as Cu, Zn and Sr, which are known to be beneficial for healthy bone growth. In addition to the new bioactive glasses, recent advances in biomaterials processing have resulted in the creation of scaffold architectures with a range of mechanical properties suitable for the substitution of loaded as well as non-loaded bone. While bioactive glass has been extensively investigated for bone repair, there has been relatively little research on the application of bioactive glass to the repair of soft tissues. However, recent work has shown the ability of bioactive glass to promote angiogenesis, which is critical to numerous applications in tissue regeneration, such as neovascularization for bone regeneration and the healing of soft tissue wounds. Bioactive glass has also been shown to enhance neocartilage formation during in vitro culture of chondrocyte-seeded hydrogels, and to serve as a subchondral substrate for tissue-engineered osteochondral constructs. Methods used to manipulate the structure and performance of bioactive glass in these tissue engineering applications are analyzed.
Doped Bioactive Glass Materials in Bone Regeneration
Advanced Techniques in Bone Regeneration, 2016
In the arena of orthopaedic surgery, autograft is considered to be the gold standard for correction of fracture repair or other bone pathologies. But, it has some limitations such as donor site morbidity and shortage of supply, which evolved the use of allograft that also has some disadvantages such as immunogenic response to the host, low osteogenicity as well as possibilities of disease transmission. Despite the benefits of autografts and allografts, the limitations of each have necessitated the pursuit of alternatives biomaterials that has the ability to initiate osteogenesis, and the graft should closely mimic the natural bone along with regeneration of fibroblasts. A variety of artificial materials such as demineralised bone matrix, coralline hydroxyapatite and calcium phosphate-based ceramics such as hydroxyapatite (HA), β-tricalcium phosphate (β-TCP) and bioactive glass have been used over the decades to fill bone defects almost without associated soft tissue development. Most of them were having only the properties of osteointegration and osteoconduction. Only bioactive glass possesses osteogenic property that stimulates proliferation and differentiation of osteoprogenitor cells and in some cases influencing the fibroblastic properties. But, this material has also some disadvantages such as short-term and low mechanical strength along with decreased fracture resistance; but, this was further minimised by ion doping that positively enhanced new bone formation. There are many metal ions such as magnesium (Mg), strontium (Sr), manganese (Mn), iron (Fe), zinc (Zn), silver (Ag) and some rare earths that have been doped successfully into bioactive glass to enhance their mechanical and biological properties. In some of the cases, mesoporous bioactive glass materials with or without such doping have also been employed (with homogeneous distribution of pores in the size ranging between 2 and 50 nm). These biomaterials can be served as scaffold for bone regeneration with adequate mechanical properties to restore bone defects and facilitate healing process by regeneration of soft tissues as well. This chapter encompasses the use of bioactive glass in bulk and mesoporous form with doped therapeutic ions, their role in bone tissue regeneration, use as delivery of growth factors as well as coating material for orthopaedic implants.
Economic route to sodium-containing silicate bioactive glass scaffold
Tetraethyl orthosilicate (TEOS) and trimethyl orthosilicate (TMOS) alkoxysilanes are expensive common precursors for silicate-based solgel-derived bioactive glasses. Facile approaches involving low cost substitutes are a necessity for bioactive glass implants in bone regeneration therapy. Quaternary SiO 2-Na 2 O-CaO-P 2 O 5 bioactive glass was prepared by the sol-gel method from locally sourced sand as precursor. The monolith glass material obtained was subjected to immersion studies in simulated body fluid (SBF) for 21 days. The surface morphology and composition of the glass before and after immersion in SBF was studied using SEM-EDX, while pH analysis was used to monitor changes on the glass surface in SBF solution. FTIR was used to confirm apatite formation on the material. Results showed that the concentration of Ca, P and C increased on the surface of the glass sample as immersion time increased, which was attributed to the formation of carbonated hydroxyapatite (HCA). The material shows ability to bond to bone making it a promising scaffold material for bone repair.
A modified sol-gel method was used in the current work to prepare a 13-93 bioactive glass powder, which was selected for the therapeutic actions of its constituent parts. In particular bioactive glass 13-93 can chemically bond with host tissue and induce osteogenesis. The produced gel was calcined at a temperature of 600 ºC, while particle size analysis and x-ray diffraction were performed after the preparation of the glass powder. Porous bioactive glass 13-93 scaffolds were synthesised using the polymer foam replication technique that uses polyurethane sponges as a template. Sintering at 700 ºC was then performed for one hour to the produce the required structures. After sintering, the microstructure was examined by scanning electron microscope (SEM) and Fourier transform infrared analysis (FTIR). The x-ray diffraction (XRD) results were also examined. The average particle size of bioactive glass 13-93 thus produced was about 2.978 µm, and XRD pattern analysis showed that the porous scaffolds were amorphous. The microstructure of the 13-93 glass scaffolds contained interconnected cellular pores and a dense network of bioactive glass, allowing scaffolds with porosity between 80 and 83% to be obtained. An in vitro bioactivity test was performed on the scaffolds by soaking them in a solution of simulated body fluid (SBF). The subsequent SEM images confirmed the bioactivity of the prepared scaffolds based on the formation of obvious and dense hydroxyapatite particles on the surface after 7 days of immersion in SBF. It was thus concluded that bioactive glass scaffold prepared in this work via the polymer foam replication technique has the potential to be used in several future applications.
Bioactive glass scaffolds for bone regeneration and their hierarchical characterisation
Proceedings of the …, 2010
Scaffolds are needed that can act as temporary templates for bone regeneration and actively stimulate vascularized bone growth so that bone grafting is no longer necessary. To achieve this, the scaffold must have a suitable interconnected pore network and be made of an osteogenic material. Bioactive glass is an ideal material because it rapidly bonds to bone and degrades over time, releasing soluble silica and calcium ions that are thought to stimulate osteoprogenitor cells. Melt-derived bioactive glasses, such as the original BioglassH composition, are available commercially, but porous scaffolds have been difficult to produce because Bioglass and similar compositions crystallize on sintering. Sol-gel foam scaffolds have been developed that avoid this problem. They have a hierarchical pore structure comprising interconnected macropores, with interconnect diameters in excess of the 100 mm that is thought to be needed for vascularized bone ingrowth, and an inherent nanoporosity of interconnected mesopores (2-50 nm) which is beneficial for the attachment of osteoprogenitor cells. They also have a compressive strength in the range of cancellous bone. This paper describes the optimized sol-gel foaming process and illustrates the importance of optimizing the hierarchical structure from the atomic through nano, to the macro scale with respect to biological response.
Molecular basis for action of bioactive glasses as bone graft substitute
Scandinavian journal of surgery : SJS : official organ for the Finnish Surgical Society and the Scandinavian Surgical Society, 2006
Bone grafting procedures are undergoing a major shift from autologous and allogeneic bone grafts to synthetic bone graft substitutes. Bioactive glasses are a group of synthetic silica-based bioactive materials with bone bonding properties first discovered by Larry Hench. They have several unique properties compared with other synthetic bioresorbable bioactive ceramics, such as calcium phosphates, hydroxyapatite (HA) and tricalcium phosphate (TCP). Bioactive glasses have different rates of bioactivity and resorption rates depending on their chemical compositions. The critical feature for the rate of bioactivity is a SiO2 content < 60% in weight. In vivo, the material is highly osteoconductive and it seems to promote the growth of new bone on its surface. In a recent study, the activity of the material was found even to overshadow the effect of BMP-2 gene therapy. In vivo, there is a dynamic balance between intramedullary bone formation and bioactive glass resorption. Recent studie...