Novel bioactive and biodegradable glass ceramics with high mechanical strength in the CaO?SiO2?B2O3 system

Efficacy of Allograft Versus Bioactive Glass-Ceramic Cage in Anterior Cervical Discectomy and Fusion: A Randomized Controlled Study

STUDY DESIGN

A randomized controlled trial.

OBJECTIVE

The aim of this study is to compare the efficacy of allografts and bioactive glass-ceramic (BG) cages for anterior cervical discectomy and fusion (ACDF) in treating cervical degenerative disc disease.

METHODS

We conducted a single-center, randomized controlled trial between August 2017 and August 2022. Participants were randomized into two groups, and consecutive patients requiring ACDF were randomly assigned to receive either the allograft cage or the BG cage. The surgical outcomes measured included pain levels, neck disability, surgical details, and radiological assessments.

RESULTS

Of the 45 assessed, 40 participants were included, with 18 in the allograft cage group and 22 in the BG cage group. By the 12-month follow-up, both groups exhibited significant improvements in pain levels and disability scores, with no notable intergroup differences. Over 85% of patients in both groups were satisfied with their outcomes. Radiological assessments revealed stability in the cervical spine with both cage types post intervention. Although both materials showed a trend toward increased subsidence over time, the difference between them was not statistically significant. Fusion rates were comparable between the groups at 12 months, with BG cage showing a slightly higher early fusion rate at 6 months. No significant differences were observed between the two groups in terms of complications.

CONCLUSIONS

Both allograft and BG cages are effective in ACDF surgeries for cervical degenerative disc disease, with both contributing to substantial postoperative improvements. Differences in disc height, interspinous motion, and subsidence were not significant in the last follow-up, indicating both materials' suitability for clinical use. Future research with a larger cohort and longer follow-up is needed to confirm these preliminary findings.

High Boron Content Enhances Bioactive Glass Biodegradation

Derived Hench bioactive glass (BaG) containing boron (B) is explored in this work as it plays an important role in bone development and regeneration. B was also found to enhance BaG dissociation. However, it is only possible to incorporate a limited amount of B. To increase the amount of B in BaG, bioactive borosilicate glasses (BaG-B_x) were fabricated based on the use of the solution-gelation process (sol-gel). In this work, a high B content (20 wt.%) in BaG, respecting the conditions of bioactivity and biodegradability required by Hench, was achieved for the first time. The capability of BaG-B_x to form an apatite phase was assessed in vitro by immersion in simulated body fluid (SBF). Then, the chemical structure and the morphological changes in the fabricated BaG-B_x (x = 0, 5, 10 and 20) were studied. The formation of hydroxyapatite (HAp) layer was observed with X-ray diffraction (XRD) and infrared (IR) spectroscopy. The presence of HAp layer was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Enhanced bioactivity and chemical stability of BaG-B_x were evaluated with an ion exchange study based on Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and energy dispersive spectroscopy (EDS). Results indicate that by increasing the concentration of B in BaG-Bx, the crystallization rate and the quality of the newly formed HAp layer on BaG-B_x surfaces can be improved. The presence of B also leads to enhanced degradation of BaGs in SBF. Accordingly, BAG-B_x can be used for bone regeneration, especially in children, because of its faster degradation as compared to B-free glass.

A review on borate bioactive glasses (BBG): effect of doping elements, degradation, and applications

Because of their excellent biologically active qualities, bioactive glasses (BGs) have been extensively used in the biomedical domain, leading to better tissue-implant interactions and promoting bone regeneration and wound healing. Aside from having attractive characteristics, BGs are appealing as a porous scaffold material. On the other hand, such porous scaffolds should enable tissue proliferation and integration with the natural bone and neighboring soft tissues and degrade at a rate that allows for new bone development while preventing bacterial colonization. Therefore, researchers have recently become interested in a different BG composition based on borate (B₂O₃) rather than silicate (SiO₂). Furthermore, apatite synthesis in the borate-based bioactive glass (BBG) is faster than in the silicate-based bioactive glass, which slowly transforms to hydroxyapatite. This low chemical durability of BBG indicates a fast degradation process, which has become a concern for their utilization in biological and biomedical applications. To address these shortcomings, glass network modifiers, active ions, and other materials can be combined with BBG to improve the bioactivity, mechanical, and regenerative properties, including its degradation potential. To this end, this review article will highlight the details of BBGs, including their structure, properties, and medical applications, such as bone regeneration, wound care, and dental/bone implant coatings. Furthermore, the mechanism of BBG surface reaction kinetics and the role of doping ions in controlling the low chemical durability of BBG and its effects on osteogenesis and angiogenesis will be outlined.

Cellular Response to Sol-Gel Hybrid Materials Releasing Boron and Calcium Ions

Poly(dimethylsiloxane) (PDMS)-SiO₂-CaO-based hybrid materials prepared by sol-gel have proved to be very promising materials for tissue engineering applications and drug-delivery systems. These hybrids are biocompatible and present osteogenic and bioactive properties supporting osteoblast attachment and bone growth. The incorporation of therapeutic elements in these materials, such as boron (B) and calcium (Ca), was considered in this study as an approach to develop biomaterials capable of stimulating bone regeneration. The main purpose of this work was thus to produce, by sol-gel, bioactive and biocompatible hybrid materials of the PDMS-SiO₂-B₂O₃-CaO system, capable of a controlled Ca and B release. Different compositions with different boron amounts were prepared using the same precursors resulting in different monolithic materials, with distinct structures and microstructures. Structural features were assessed by Fourier transform infrared (FT-IR) spectrometry and solid-state nuclear magnetic resonance (NMR) techniques, which confirmed the presence of hybrid bonds (Si-O-Si) between organic (PDMS) and inorganic phase (tetraethyl orthosilicate (TEOS)), as well as borosiloxane bonds (B-O-Si). From the ¹¹B NMR results, it was found that Ca changes the boron coordination, from trigonal (BO₃) to tetrahedral (BO₄). Scanning electron microscopy (SEM) micrographs and N₂ isotherms showed that the incorporation of boron modifies the material's microstructure by increasing the macroporosity and decreasing the specific surface area (SSA). In vitro tests in simulated body fluid (SBF) showed the precipitation of a calcium phosphate layer on the material surface and the controlled release of therapeutic ions. The cytocompatibility of the prepared hybrids was studied with bone marrow stromal cells (ST-2 cell line) by analyzing the cell viability and cell density. The results demonstrated that increasing the dilution rate of extraction medium from the hybrids leads to improved cell behavior. The relationship between the in vitro response and the structural and microstructural features of the materials was explored. It was shown that the release of calcium and boron ions, determined by the hybrid structure was crucial for the observed cells behavior. Although not completely understood, the encouraging results obtained constitute an incentive for further studies on this topic.

Cellulose acetate-gelatin-coated boron-bioactive glass biocomposite scaffolds for bone tissue engineering

In this study, we aimed to prepare and characterize porous scaffolds composed of pure and boron oxide (B₂O₃)-doped bioactive glass (BG) that were infiltrated by cellulose acetate-gelatin (CA-GE) polymer solution for bone tissue engineering applications. Composite scaffolds were cross-linked with glutaraldehyde after polymer coating to protect the structural integrity of the polymeric-coated scaffolds. The impact of B₂O₃ incorporation into BG-polymer porous scaffolds on the cross-sectional morphology, porosity, mechanical properties, degradation and bioactivity of the scaffolds was investigated. Human dental pulp stem cells (hDPSCs) were enzymatically isolated and used for cell culture studies. According to scanning electron microscope analysis, the porous structure of the scaffolds was preserved after polymer coating. After polymer infiltration, the porosity of the scaffolds decreased from 64.2% to 59.35% for pure BG scaffolds and from 67.3% to 58.9% for B₂O₃-doped scaffolds. Meanwhile, their compressive strengths increased from 0.13 to 0.57 MPa and from 0.20 to 0.82 MPa, respectively. After polymer infiltration, 7% B₂O₃-incorporated BG scaffolds had higher weight loss and Ca-P layer deposition than pure BG scaffolds, after 14 d of incubation in simulated body fluid at 37 °C. Higher attachment and proliferation of hDPSCs were observed on 7% B₂O₃-BG-CA/GE scaffolds. In addition, the alkaline phosphatase activity of the cells was about 1.25-fold higher in this group than that observed on BG-CA/GE scaffolds after 14 d of incubation in osteogenic medium, while their intracellular calcium amounts were 1.7-fold higher than observed on BG-CA/GE after 7 d of incubation in osteogenic medium. Our results suggested that porous cellulose acetate-gelatin-coated boron-BG scaffolds hold promise for bone tissue engineering applications.

Bioactivity and Antibacterial Studies on Silver Nanoparticles Embedded Calcium Borosilicate Ceramics

We report the structural, bioactivity and antibacterial effect of silver nanoparticle embedded calcium borosilicate ceramics obtained by a simple sol-gel route and post annealing approach. The structural properties were studied by means of powder X-ray diffraction (XRD), UV-visible, Fourier transform infrared (FTIR) and transmission electron microscopy (TEM). The glass-ceramic nature of the sample was confirmed by XRD and FTIR. TEM and UV spectrum reveal the Ag nanoparticle embedment on amorphous matrix. The hydroxyapatite layer formation is investigated by in-vitro approach using Dulbecco’s Modified Eagle’s Medium. The antibacterial effects were tested with different bacteria using an agar well diffusion method. Samples show good antibacterial effect without compromising the formation of hydroxyapatite.

Biodegradable Materials for Bone Repair and Tissue Engineering Applications

This review discusses and summarizes the recent developments and advances in the use of biodegradable materials for bone repair purposes. The choice between using degradable and non-degradable devices for orthopedic and maxillofacial applications must be carefully weighed. Traditional biodegradable devices for osteosynthesis have been successful in low or mild load bearing applications. However, continuing research and recent developments in the field of material science has resulted in development of biomaterials with improved strength and mechanical properties. For this purpose, biodegradable materials, including polymers, ceramics and magnesium alloys have attracted much attention for osteologic repair and applications. The next generation of biodegradable materials would benefit from recent knowledge gained regarding cell material interactions, with better control of interfacing between the material and the surrounding bone tissue. The next generations of biodegradable materials for bone repair and regeneration applications require better control of interfacing between the material and the surrounding bone tissue. Also, the mechanical properties and degradation/resorption profiles of these materials require further improvement to broaden their use and achieve better clinical results.

Skeletal tissue engineering using mesenchymal or embryonic stem cells: clinical and experimental data

INTRODUCTION

Mesenchymal stem cells (MSCs) can be obtained from a wide variety of tissues for bone tissue engineering such as bone marrow, adipose, birth-associated, peripheral blood, periosteum, dental and muscle. MSCs from human fetal bone marrow and embryonic stem cells (ESCs) are also promising cell sources.

AREAS COVERED

In vitro, in vivo and clinical evidence was collected using MEDLINE® (1950 to January 2014), EMBASE (1980 to January 2014) and Google Scholar (1980 to January 2014) databases.

EXPERT OPINION

Enhanced results have been found when combining bone marrow-derived mesenchymal stem cells (BMMSCs) with recently developed scaffolds such as glass ceramics and starch-based polymeric scaffolds. Preclinical studies investigating adipose tissue-derived stem cells and umbilical cord tissue-derived stem cells suggest that they are likely to become promising alternatives. Stem cells derived from periosteum and dental tissues such as the periodontal ligament have an osteogenic potential similar to BMMSCs. Stem cells from human fetal bone marrow have demonstrated superior proliferation and osteogenic differentiation than perinatal and postnatal tissues. Despite ethical concerns and potential for teratoma formation, developments have also been made for the use of ESCs in terms of culture and ideal scaffold.

Toward Strong and Tough Glass and Ceramic Scaffolds for Bone Repair

The need for implants to repair large bone defects is driving the development of porous synthetic scaffolds with the requisite mechanical strength and toughness in vivo. Recent developments in the use of design principles and novel fabrication technologies are paving the way to create synthetic scaffolds with promising potential for reconstituting bone in load-bearing sites. This article reviews the state of the art in the design and fabrication of bioactive glass and ceramic scaffolds that have improved mechanical properties for structural bone repair. Scaffolds with anisotropic and periodic structures can be prepared with compressive strengths comparable to human cortical bone (100-150 MPa), while scaffolds with an isotropic structure typically have strengths in the range of trabecular bone (2-12 MPa). However, the mechanical response of bioactive glass and ceramic scaffolds in multiple loading modes such as flexure and torsion - as well as their mechanical reliability, fracture toughness, and fatigue resistance - has received little attention. Inspired by the designs of natural materials such as cortical bone and nacre, glass-ceramic and inorganic/polymer composite scaffolds created with extrinsic toughening mechanisms are showing potential for both high strength and mechanical reliability. Future research should include improved designs that provide strong scaffolds with microstructures conducive to bone ingrowth, and evaluation of these scaffolds in large animal models for eventual translation into clinical applications.

Fabrication and evaluation of osteoblastic differentiation of human mesenchymal stem cells on novel CaO-SiO2-P2O5-B2O3 glass-ceramics

Apatite-wollastonite glass-ceramics have high mechanical strength, and CaO-SiO2 -B2 O3 glass-ceramics showed excellent bioactivity and high biodegradability. A new type of CaO-SiO2 -P2 O5 -B2 O3 system of bioactive glass-ceramics (BGS-7) was fabricated, and the effect and usefulness was evaluated via bioactivity using simulated body fluid and human mesenchymal stem cells (hMSCs). The purpose of this study was to compare BGS-7 and hydroxyapatite (HA) using hMSCs in order to evaluate the bioactivity of BGS-7 and its possibility as a bone graft extender. Alkaline phosphatase (ALP) staining, ALP activity, cell proliferation 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, Alizarin Red-S (AR-S) staining, calcium levels, the mRNA expression of ALP, osteocalcin, osteopontin, and runt-related transcription factor 2 (runx-2) using reverse-transcription polymerase chain reaction (RT-PCR) and the protein expression of osteocalcin and runx-2 using Western blot were measured by transplanting hMSC onto a tissue culture plate, HA, and BGS-7. The ALP staining and AR-S staining of BGS-7 was greater than that of HA and control. The ALP value of BGS-7 was significantly higher than that of HA and control. The MTS results showed that BGS-7 had a higher value than the groups transplanted onto HA and control on day 15. The calcium level was higher than the control in both HA and BGS-7, and was especially high in BGS-7. There were more mineral products on BGS-7 than on the HA when analyzed by scanning electron microscopy. The mRNA expression of ALP, osteopontin, osteocalcin, and runx-2 were higher on BGS-7 than on HA and the control when analyzed by RT-PCR. The relative gene expression of osteopontin and runx-2 were found to be higher on BGS-7 than on HA and the control by Western blot. Accordingly, it is predicted that BGS-7 would have high biocompatibility and good osteoconductivity, and presents a possibility as a new bone graft extender.

A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

Several inorganic materials such as special compositions of silicate glasses, glass-ceramics and calcium phosphates have been shown to be bioactive and resorbable and to exhibit appropriate mechanical properties which make them suitable for bone tissue engineering applications. However, the exact mechanism of interaction between the ionic dissolution products of such inorganic materials and human cells are not fully understood, which has prompted considerable research work in the biomaterials community during the last decade. This review comprehensively covers literature reports which have investigated specifically the effect of dissolution products of silicate bioactive glasses and glass-ceramics in relation to osteogenesis and angiogenesis. Particularly, recent advances made in fabricating dense biomaterials and scaffolds doped with trace elements (e.g. Zn, Sr, Mg, and Cu) and investigations on the effect of these elements on the scaffold biological performance are summarized and discussed in detail. Clearly, the biological response to artificial materials depends on many parameters such as chemical composition, topography, porosity and grain size. This review, however, focuses only on the ion release kinetics of the materials and the specific effect of the released ionic dissolution products on human cell behaviour, providing also a scope for future investigations and identifying specific research needs to advance the field. The biological performance of pure and doped silicate glasses, phosphate based glasses with novel specific compositions as well as several other silicate based compounds are discussed in detail. Cells investigated in the reviewed articles include human osteoblastic and osteoclastic cells as well as endothelial cells and stem cells.

Synthesis, bioactivity and preliminary biocompatibility studies of glasses in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2

New compositions of bioactive glasses are proposed in the CaO-MgO-SiO(2)-Na(2)O-P(2)O(5)-CaF(2) system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO(4)) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts' cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).

In vivo study of novel biodegradable and osteoconductive CaO-SiO2-B2O3 glass-ceramics

To evaluate the possibility of novel CaO-SiO2-B2O3 glass-ceramics (CS10B) as a new bone replacement material, we compared the biodegradation and osteoconduction properties of CS10B, hydroxyapatite (HA), and tricalcium phosphate (TCP). Porous CS10B implants were prepared by the polymer sponge method. L5-6 single-level posterolateral spinal fusions were performed on 30 New Zealand white male rabbits. The animals were divided into three groups by implant material: CS10B, HA, and TCP. Radiographs were performed every 2 weeks. All animals were euthanized 12 weeks after surgery. The ratio of the area occupied by the ceramics by final and initial radiographs was calculated using radiomorphometric analysis. Uniaxial tensile strength was determined from seven cases in each group. The ratio of the area occupied by HA (88.7%+/-16.1%) was significantly higher than the others (p<0.005), and the ratio of the area occupied by CS10B (28.2%+/-9.3%) was significantly lower than those of HA and TCP (37%+/-9.6%, p<0.05). The mean values of the tensile strengths of the CS10B (182.7+/-19.9 N) and HA (191.4+/-33.5 N) were significantly higher (p<0.05) than that of TCP (141.1+/-28.2 N). CS10B had a fusion mass tensile strength similar to that of HA. Histological analysis confirmed that CS10B was well incorporated into the fusion mass. These findings suggest that CS10B is a possible bone replacement material.

Increased Osteogenesis Elicited by Boron-Modified Bioactive Glass Particles in the SiO2-CaO-P2O5-Na2O System: A Histomorphometric Study in Rats

The effect of boron-containing bioactive glass (BG) particles in the SiO2-CaO-P2O5-Na2O system on the bone formation was studied by histologic, histomorphometric and microchemical evaluation. Wistar rats were used throughout. Under anesthesia, 45S5 BG particles were placed inside the medullary compartment of the tibia (Control), while in the contralateral tibia (Experimental) 45S5.2B BG particles were implanted. The animals were sacrificed 15 days postimplantation. The tibiae were resected, radiographed, and embedded in methyl methacrylate resin. Sections were stained with toluidine blue and analyzed by light microscopy, backscattered scaning electron microscopy and energy-dispersive X-ray analysis (EDX). Histomorphometric determinations were performed. Light microscopy of the histologic sections showed lamellar bone formation surrounding both biomaterials. The histomorphometric study revealed a statistically significant increase in bone tissue around 45S5.2B BG particles. EDX of newly formed bone tissue showed a rise in the Ca:P ratio when 45S5.2B BG particles were employed. The results described in the present study reveal that this boron-containing bioactive glass may be used as scaffold for bone tissue regeneration.