Sol-gel Bioactive Glasses Research Articles

Time- and Concentration-Dependent Effects of Dissolution Products of 58S Sol–Gel Bioactive Glass on Proliferation and Differentiation of Murine and Human Osteoblasts

Time- and Concentration-Dependent Effects of Dissolution Products of 58S Sol–Gel Bioactive Glass on Proliferation and Differentiation of Murine and Human Osteoblasts

A new route to prepare macroporous bioactive sol–gel glasses with high mechanical strength

This paper reports a new method to obtain macroporous bioactive glasses by sol–gel and pore former technologies. The in vitro tests showed that the samples had good apatite-forming ability. Noticeably, these bioglasses exhibit high specific surface areas and excellent mechanical performances. The compressive strength is as high as 34.4±5.7 MPa. This method may be a useful approach for preparation of scaffolds for tissue engineering.

Bioactive glasses as accelerators of apatite bioactivity.

Synthetic carbonatehydroxyapatite is the ceramic closest to the mineral component of human bone and seems, therefore, the optimum material to use in osseous implants. However, in vitro assays performed to determine its bioactivity have shown no positive results after 2 months of assay. With the aim of improving this bioactivity, a new biphasic material was synthesized composed mainly of synthetic carbonatehydroxyapatite and only 5% of a sol-gel bioactive glass. In vitro assays were assessed to determine the bioactive behavior of this new material and revealed that the addition of a minimal amount of bioactive glass is enough to induce bioactivity on synthetic carbonatehydroxyapatites.

Bioactive sol–gel glasses with and without a hydroxycarbonate apatite layer as substrates for osteoblast cell adhesion and proliferation

The biocompatibility of three sol–gel bioactive glasses with SiO 2 as the main constituent (75, 72.5 and 70 mol%), identical CaO content (25 mol%), and without or with P 2O 5 as third constituent (0, 2.5 and 5 mol%), have been analyzed (S75, S72.5P2.5, and S70P5 glasses). These studies were performed on both untreated glasses and on glasses coated with a hydroxycarbonate apatite (HCA) layer formed in vitro by soaking 7 d in an acellular simulated body fluid. Cell attachment, spreading and proliferation were studied using neonatal rat calvaria osteoblasts. Cells attach to the three untreated glasses but show a higher efficiency on that with the higher phosphate content (S70P5). The formation of the HCA layer significantly enhances this process (1.7-fold). In all cases, attachment is followed by cell spreading on the surface of the materials, adopting the cells a flattened morphology and showing diverse anchoring cell projections. Mitotic activity has been detected on osteoblasts growing on the sol–gel glasses, being this process 2–4-fold higher when the apatite-like layer is already formed. Taking into account the results herein presented, these bioactive glasses can be considered biocompatible. In addition, their biocompatibility is greatly enhanced after induction of the formation of an HCA layer.

Biphasic materials for bone grafting and hyperthermia treatment of cancer.

Three biphasic materials have been synthesized from a magnetic glass-ceramic (Si-Ca-Fe) and a bioactive sol-gel glass (Si-P-Ca). The ratios of glass-ceramic:sol-gel glass used in this work were 1:1, 2:1, and 5:1. These materials show bioactive and magnetic properties and can be used as thermoseeds for hyperthermia treatment of bone tumors. The sol-gel glass content affects the textural properties of the glass-ceramic, giving rise to porosity, which plays a fundamental role in the formation of an apatite-like layer on the surface. On the other hand, as the sol-gel glass content increases, the magnetic properties change due to the diffusion of Fe ions to the glassy phases of the biphasic materials. The biphasic nature of these materials allows the changing of both properties, depending on the requirements of the patient.

Biocompatibility and in vivo gentamicin release from bioactive sol-gel glass implants.

Biomaterial pieces, with suitable osteogenic properties for use in the treatment of bone defects and the capability to avoid bone infections, have been synthesized. These materials are composed exclusively of gentamicin sulfate and bioactive SiO(2)-CaO-P(2)O(5) sol-gel glass (previously synthesized). Implant processing was achieved by uniaxial and isostatic pressure of the components mixture. After implanting the pieces into rabbit femur, we studied (i) the antibiotic release, determining the concentration in proximal and distal bone, liver, kidney, and lung as a function of time; and (ii) the bone growth resulting from the glass reactivity in the biologic environment. The results indicate that the implants are good carriers for local gentamicin release in the osseous tissue, exhibiting excellent biocompatibility and bone integration. Moreover, these implants are able to promote bone growth during their resorption process.

Absorbability of Bulk Sol-Gel Bioactive Glasses

Absorbability of Bulk Sol-Gel Bioactive Glasses

Bioactivity of sol-gel bioactive glass coated alumina implants.

Alumina on alumina total hip arthroplasty has been in use for more than 25 years with encouraging results. However, an improvement of the alumina/bone interface still is required. The objective of this study was to investigate the in vitro and in vivo osteoconductive properties of sol-gel bioactive glass coated alumina implants. Two sol-gel glass compositions (58S Bioglass(R) and 77S Bioglass(R)) were used as coatings on alumina substrates and implanted in a rabbit model. The 58S sol-gel coating was employed in two configurations, single (A58S1) and double layer (A58S2). SEM analysis after one week in simulated body fluid revealed small crystals assumed to represent the initial phase of hydroxyapatite formation, whereas no clear conclusion could be drawn from Fourier transform infrared spectroscopy data. The percentage of bone in direct contact was greater for coated implants when compared to bulk alumina implants (p <0.001). In the case of A58S1 implants, bone percentage significantly increased from 45.1% after 3 weeks up to 87. 8% after 24 weeks of implantation (p = 0.0004). The presence of osteoid tissue, related to an aluminum release from the alumina substrates, was greatly diminished when compared to melt-derived glass-coated alumina implants.

Processing and properties of sol-gel bioactive glasses.

Melt derived 45S5 Bioglass(R) has been studied for more than 25 years. Bioglass(R) has excellent biocompatibility, and its surface reactivity has contributed to its clinical success over the past 10 years. Recently, porous bioactive glasses have been derived through sol-gel processing in an attempt to increase the specific surface area, and, thus, the surface reactivity and degradability of the material. This allows the material to be replaced ultimately by natural tissue while it stimulates bone regeneration. In this work, the processing and properties of these sol-gel bioactive glasses are discussed, and a new drying method and treatment is described to make homogeneous particulate and monoliths on a production scale.

Molecular Control of Bioactivity in Sol-Gel Glasses

Bioactive materials can be divided into: Class A bioactive glasses which exhibit rapid bonding to bone and soft connective tissue and are osteoproductive, and osteoconductive; and Class B bioactive ceramics, which bond slowly only to bone and are only osteoconductive. Bioactive sol-gel glasses composed of SiO2-CaO-P2O5 have Class A behavior in vitro and in vivo and also resorb as they enhance the proliferation of new trabecular bone.

Properties of trypsin and of acid phosphatase immobilized in sol-gel glass matrices.

Trypsin and acid phosphatase-containing silica sol-gel glasses were obtained by mixing a solution of an enzyme with polyethylene glycol (PEG) 6000 and tetramethoxy orthosilicate at room temperature, followed by gelation and drying. Activity of the immobilized trypsin toward small substrates, such as N-benzoyl-L-arginine-4-nitroanilide at its Km, for the best preparations equaled that of the soluble enzyme. Polylysine (M(r) less than or equal to 13,000) and aprotinin (M(r) = 6,500) inhibited this activity. Larger polylysines as well as soybean trypsin inhibitor (M(r) = 20,100) were ineffective. The sol-gel-entrapped trypsin activity was stable when sol-gel glasses were incubated at ambient temperature (pH 7.5) for several months. In comparison, trypsin, immobilized in sol-gel glass by surface adsorption and incubated under the same conditions overnight, was completely autodigested. The firm interaction between the protein molecules and the silica matrix stabilized the enzymes. Thus, the half-life of sol-gel-entrapped acid phosphatase at 70 degrees C (pH 8.0) was two orders of magnitude larger than that of the enzyme in solution. Transparent, mechanically and chemically stable bioactive sol-gel glasses may be used for the development of robust on-line biochemical photodetection sensors and for the purposes of chemical catalysis.