Abstract

In this study, the in vivo bone-regenerative capacity and resorption of the porous β-calcium silicate (β-CaSiO₃, β-CS) bioactive ceramics were investigated in a rabbit calvarial defect model, and the results were compared with porous β-tricalcium phosphate (β-Ca₃(PO₄)₂, β-TCP) bioceramics. The porous β-CS and β-TCP ceramics were implanted in rabbit calvarial defects and the specimens were harvested after 4, 8 and 16 weeks, and evaluated by Micro-CT and histomorphometric analysis. The Micro-CT and histomorphometric analysis showed that the resorption of β-CS was much higher than that of β-TCP. The TRAP-positive multinucleated cells were observed on the surface of β-CS, suggesting a cell-mediated process involved in the degradation of β-CS in vivo. The amount of newly formed bone was also measured and more bone formation was observed with β-CS as compared with β-TCP (p < 0.05). Histological observation demonstrated that newly formed bone tissue grew into the porous β-CS, and a bone-like apatite layer was identified between the bone tissue and β-CS materials. The present studies showed that the porous β-CS ceramics could stimulate bone regeneration and may be used as bioactive and biodegradable materials for hard tissue repair and tissue engineering applications.

Abstract

For a biomaterial to be considered suitable for bone repair it should ideally be both bioactive and have a capacity for controllable drug delivery; as such, mesoporous SiO₂ glass has been proposed as a new class of bone regeneration material by virtue of its high drug-loading ability and generally good biocompatibility. It does, however, have less than optimum bioactivity and controllable drug delivery properties. In this study, we incorporated strontium (Sr) into mesoporous SiO₂ in an effort to develop a bioactive mesoporous SrO–SiO₂ (Sr–Si) glass with the capacity to deliver Sr²⁺ ions, as well as a drug, at a controlled rate, thereby producing a material better suited for bone repair. The effects of Sr²⁺ on the structure, physiochemistry, drug delivery and biological properties of mesoporous Sr–Si glass were investigated. The prepared mesoporous Sr–Si glass was found to have an excellent release profile of bioactive Sr²⁺ ions and dexamethasone, and the incorporation of Sr²⁺ improved structural properties, such as mesopore size, pore volume and specific surface area, as well as rate of dissolution and protein adsorption. The mesoporous Sr–Si glass had no cytotoxic effects and its release of Sr²⁺ and SiO₄⁴⁻ ions enhanced alkaline phosphatase activity – a marker of osteogenic cell differentiation – in human bone mesenchymal stem cells. Mesoporous Sr–Si glasses can be prepared to porous scaffolds which show a more sustained drug release. This study suggests that incorporating Sr²⁺ into mesoporous SiO₂ glass produces a material with a more optimal drug delivery profile coupled with improved bioactivity, making it an excellent material for bone repair applications.

Abstract

In the present investigation, β-dicalcium silicate (β-Ca₂SiO₄) and γ-dicalcium silicate (γ-Ca₂SiO₄) powders were synthesized by sol-gel process and hydrothermal synthesis, respectively. The in vitro bioactivity of both β-, and γ-Ca₂SiO₄ was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of hydroxyapatite (HAp) on the surface of the powders. After soaked in SBF for 6 h, HAp appeared on the surface of β-, and γ-Ca₂SiO₄ particles, and uniform lathlike aggregates with typical morphology of HAp crystals formed after 5 days. The β-Ca₂SiO₄ showed strong hydration when soaked in SBF and the hydration was favorable for formation of carbonate-containing hydroxyapatite on the surface of the materials. The γ-Ca₂SiO₄ was not hydrated in SBF solution and showed a slower formation of carbonate-containing hydroxyapatite on the surface when compared with β-Ca₂SiO₄. In addition, the Si concentration in the SBF increased quickly up to 5 days and remained invariable with increased soaking time. The results obtained indicate that hydroxyapatite nuclei can form and grow on the β-, and γ-Ca₂SiO₄ particles, and these two dicalcium silicates are potential candidates as biomaterials for hard tissue repair.

Abstract

Bioactive beta-dicalcium silicate ceramics (β-Ca₂SiO₄) were fabricated by spark plasma sintering (SPS). The relative density of as-prepared β-Ca₂SiO₄ ceramics reached 98.1% when sintered at 1150 °C, leading to great improvement in bending strength (293 MPa), almost 10 times higher than that of the specimen prepared by conventional pressureless sintering (PLS). High fracture toughness (3.0 MPa m^1/2) and Vickers hardness (5.8 GPa) of β-Ca₂SiO₄ ceramics were also achieved by SPS at 1150 °C. The simulated body fluid (SBF) results showed that β-Ca₂SiO₄ ceramics had a good in vitro bioactivity to induce hydraxyapatite (HAp) formation on their surface, which suggests that β-Ca₂SiO₄ ceramics are promising candidates for load-bearing bone implant materials.

Abstract

In this study, tricalcium silicate (Ca₃SiO₅), as a new promising injectable bioactive material, was employed to investigate its physical and chemical properties for an injectable bioactive cement filler. The workable Ca₃SiO₅ pastes with a liquid to powder (L/P) ratio of 0.8–1.2 ml g⁻¹could be injected for 15–60 min (nozzle diameter 2.0 mm). The setting process yielded cellular structures with compressive strength of 6.4–20.2 MPa after 2–28 days. The in vitro bioactivity of Ca₃SiO₅ paste was investigated by soaking in simulated body fluid (SBF) for various periods. The result showed that the Ca₃SiO₅ paste could induce hydroxyapatite (HA) formation and dissolve slowly in SBF. The result of indirect cytotoxicity evaluation indicated that Ca₃SiO₅ paste had a stimulatory effect on cell growth in a certain concentration range. The exothermic process showed that Ca₃SiO₅ had lower heat evolution rate during the hydration as compared to calcium phosphate cement (CPC). Our results indicated that Ca₃SiO₅ paste was bioactive and dissolvable, and it is a progressive candidate for further investigation as injectable tissue repairing substitute.

Abstract

Introduction

This study was to investigate the effects of tricalcium silicate (Ca₃SiO₅) on proliferation and odontogenic differentiation of human dental pulp cells (hDPCs) in vitro.

Methods

The hDPCs were seeded in culture medium with or without Ca₃SiO₅ extract and calcium hydroxide (Ca(OH)₂) extract. Proliferation of the hDPCs was measured by methyl-thiazol-tetrazolium (MTT) assay. Odontogenic differentiation of hDPCs was evaluated by real-time polymerase chain reaction by using odontogenic marker genes such as dentin sialophosphoprotein (DSPP), dentin matrix protein 1 (DMP 1), osteocalcin (OC), alkaline phosphatase (ALP), and collagen type I (Col I), which were verified by ALP activity assessment, mineralization assay, and immunocytochemistry staining for dentin sialoprotein (DSP).

Results

The MTT assay showed that hDPCs cultured with Ca₃SiO₅ extract proliferated more significantly as compared with Ca(OH)₂ extract. Analysis of odontogenic marker genes indicated that Ca₃SiO₅ enhanced the expression of those genes. Moreover, the extract of Ca₃SiO₅ stimulated mineralization and increased ALP and DSP production conspicuously.

Conclusions

These results reveal that Ca₃SiO₅ can induce the proliferation and odontogenic differentiation of hDPCs in vitro and might be a potential candidate for preparation of a new type of Ca₃SiO₅₋based cement as a pulp-capping agent.

Abstract

Forsterite (Mg₂SiO₄) ceramics were prepared by sintering the Mg₂SiO₄ green compacts at 1350–1550 °C and the sintering behavior and mechanical properties were examined. The results showed that the optimal bending strength (203 MPa) and fracture toughness (2.4 MPa m^1/2) of forsterite ceramics were obtained after hot treatment at 1450 °C for 8 h, which were higher than those of the currently available hydroxyapatite ceramics. In order to clarify the biocompatibility of the forsterite ceramics, osteoblast adhesion and proliferation experiments were carried out. Well-spread cells were observed on the surface of forsterite ceramics. In addition, MTT tests confirmed that the osteoblast proliferation rate was significantly higher on the surface of the sintered ceramics than on the controls at 7 days (p < 0.05). These findings suggest that forsterite ceramics possess good biocompatibility and mechanical properties and might be suitable for potential application like bone implant material.

Abstract

This work deals with the fabrication and characterization of nanostructured forsterite bulk. This material may have better biocompatibility and mechanical properties than coarse grain forsterite for the development of bone tissue engineering materials. Nanostructured forsterite bulks were prepared by two step sintering of sol–gel derived forsterite nanopowder. Their sinterability and mechanical properties were then studied. Biocompatibility of the nanostructured forsterite bulk was also evaluated by cell attachment and proliferation experiments. In addition, the effects of ionic products from forsterite nanopowder dissolution on osteoblasts were studied. Results show that dense nanostructured forsterite bulk was prepared with hardness and fracture toughness of about 1102 Hv and 4.3 MPa m^1/2, respectively. Nanostructured forsterite was biocompatible and the MTT test confirmed that the products from forsterite nanopowder dissolution significantly promoted osteoblast proliferation within a certain concentration range. In addition, cells attached to and spread on the surface of nanostructured forsterite bulks. Mechanical properties of the nanostructured forsterite were much higher than that of hydroxyapatite. It was concluded that nanostructured forsterite is a bioactive ceramic with good biocompatibility that can be used as a bone tissue engineering material.

Research highlights

? Mechanical properties of nanostructured forsterite were much higher than that of hydroxyapatite. ? MTT test confirmed that the products from forsterite nanopowder dissolution significantly promoted osteoblast proliferation within a certain concentration range. ? Osteoblast attached to and spread on the surface of nanostructured forsterite bulks. ? Nanostructured forsterite is a bioactive ceramic with good biocompatibility that can be used as a bone tissue engineering material.

Abstract

Although micron size forsterite is biocompatible, the degradation rate of this ceramic is extremely low, and the apatite formation ability is poor as well. In this study, the influence of nanostructure and the degree of crystallinity on the apatite formation ability and degradation rate were investigated. Forsterite was synthesized by 5 h of milling of talc and magnesium carbonate and subsequent annealing at 1000 °C in the presence of chloride ion. To investigate the in vitro bioactivity and degradability, the prepared forsterite powder was pressed in the form of tablets and then immersed in simulated body fluid (SBF) and Ringer's solution, respectively. The results showed that nanostructure forsterite powder with crystallite size of about 20 nm was bioactive and released magnesium ions in the SBF solution. With increasing crystallinity degree of nanostructure forsterite, the apatite formation ability and degradation rate decreased.

Abstract

This is the first report of successful synthesis of pure spinel–forsterite nanocomposites from talc, alumina, and magnesium carbonate powders. Appropriate ratios of initial materials were mixed and mechanically activated in a planetary ball mill. The obtained powders were annealed at high temperatures. Pure spinel–forsterite nanocomposites with crystallites size in the range of 30–87 nm were obtained after 40 h of mechanical activation and subsequent annealing at 1200 °C for 1 h. The results of cold crushing strength (CCS) showed that the maximum strength of the fired spinel–forsterite bodies (∼67 MPa) can be obtained in those samples with 10 wt.% spinel. The bulk density (BD) and apparent porosity (AP) of these samples were 1.46% and 17%, respectively.

Abstract

In the present study, the effects of a calcium magnesium silicate bioactive ceramic (akermanite) on proliferation and osteoblastic differentiation of human bone marrow stromal cells (hBMSC) have been investigated and compared with the classical ceramic (β-tricalcium phosphate, β-TCP). Akermanite and β-TCP disks were seeded with hBMSC and kept in growth medium or osteogenic medium for 10 days. Proliferation and osteoblastic differentiation were evaluated on day 1, 4, 7 and 10. The data from the Alamar Blue assay and lactic acid production assay showed that hBMSC proliferated more significantly on akermanite than on β-TCP. The analysis of osteoblast-related genes, including alkaline phosphatase (ALP), osteopontin (OPN), bone sialoprotein (BSP) and osteocalcin (OC), indicated that akermanite ceramics enhanced the expression of osteoblast-related genes, but type I collagen (COL I) showed no noticeable difference among akermanite and β-TCP ceramics. Furthermore, this stimulatory effect was observed not only in osteogenic medium, but also in normal growth medium without osteogenic reagents such as l-ascorbic acid, glycerophosphate and dexamethasone. This result suggests that akermanite can promote osteoblastic differentiation of hBMSC in vitro even without osteogenic reagents, and may be used as a bioactive material for bone regeneration and tissue engineering applications.

Abstract

This study investigated the effects of a calcium magnesium silicate bioceramic (akermanite) for bone regeneration in vitro and in vivo, with β-tricalcium phosphate (β-TCP) as a control. In vitro, the human bone marrow-derived mesenchymal stromal cells (hBMSCs) were cultured in an osteogenic medium supplemented with a certain concentration of two bioceramics' extracts for 20 days. An MTT assay showed that akermanite extract promoted proliferation of hBMSC significantly more than did β-TCP extract. The results of alkaline phosphatase (ALP) activity test and the expression of osteogenic marker genes such as ALP, osteopontin (OPN), osteocalcin (OCN) and bone sialoprotein (BSP) demonstrated that the osteogenic differentiation of hBMSC was enhanced more by akermanite extract than by β-TCP extract. In vivo, a histomorphology analysis and histomorphometry of the two porous bioceramics implants in rabbit femur defect models indicated that both in early- and late-stage implantations, akermanite promoted more osteogenesis and biodegradation than did β-TCP; and in late-stage implantations, the rate of new bone formation was faster in akermanite than in β-TCP. These results suggest that akermanite might be a potential and attractive bioceramic for tissue engineering.

Abstract

This study investigated the in vitro effects of akermanite, a new kind of Ca-, Mg-, Si-containing bioceramic, on the attachment, proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs). Parallel comparison of the cellular behaviors of hASCs on the akermanite was made with those on beta-tricalcium phosphate (β-TCP). Scanning electron microscope (SEM) observation and fluorescent DiO labeling were carried out to reveal the attachment and growth of hASCs on the two ceramic surfaces, while the quantitative assay of cell proliferation with time was detected by DNA assay. Osteogenic differentiation of hASCs cultured on the akermanite and β-TCP was assayed by ALP expression and osteocalcin (OCN) deposition, which was further confirmed by Real-time PCR analysis for markers of osteogenic differentiation. It was shown that hASCs attached and spread well on the akermanite as those on β-TCP, and similar proliferation behaviors of hASCs were observed on the two ceramics. Both of them exhibited good compatibility to hASCs with only minor cytotoxicity as compared with the tissue culture plates. Interestingly, the osteogenic differentiation of hASCs could be enhanced on the akermanite compared with that on the β-TCP when the culture time was extended to ∼10 days. Thus, it can be ascertained that akermanite ceramics may serve as a potential scaffold for bone tissue engineering.

Abstract

Our previous study indicates that akermanite, a type of Ca-, Mg-, Si-containing bioceramic, can promote the osteogenic differentiation of hASCs. To elucidate the underlying mechanism, we investigated the effect of the extract from akermanite, on proliferation and osteogenic differentiation of hASCs. The original extract was obtained at 200 mg akermanite/ml LG-DMEM and further diluted with LG-DMEM. The final extracts were denoted as 1/2, 1/4, 1/8, 1/16, and 1/32 extracts based on the concentrations of the original extract. The LDH assay and live/dead stain were used to reveal the cytotoxicity of the different extracts on hASCs, while the DNA assay was carried out to quantitatively evaluate the proliferation of cells after being cultured with the extracts for 1, 3 and 7 days. Flow cytometry for cell cycle analysis was carried out on cells cultured in two media (GM and 1/2 extract) in order to further analyze the effect of the extract on cell proliferation behaviors. Osteogenic differentiation of hASCs cultured in the extracts was detected by ALP expression and calcium deposition, and further confirmed by real-time PCR analysis. It was shown that Ca, Mg and Si ions in the extract could suppress the LDH release and proliferation of hASCs, whereas promote their osteogenic differentiation. Such effects were concentration-dependent with the 1/4 extract (Ca 2.36 mM, Mg 1.11 mM, Si 1.03 mM) being the optimum in promoting the osteogenic differentiation of hASCs. An immediate increase in ERK was observed in cells cultured in the 1/4 extract and such osteogenic differentiation of hASCs promoted by released ions could be blocked by MEK1-specific inhibitor, PD98059. Briefly, Ca, Mg and Si ions extracted from akermanite in the concentrations of 2.36, 1.11, 1.03 mM, respectively, could facilitate the osteogenic differentiation of hASCs via an ERK pathway, and suppress the proliferation of hASCs without significant cytotoxicity.

Abstract

In this study, new bredigite (Ca₇MgSi₄O₁₆) ceramics were prepared by sintering sol–gel-derived bredigite powder compacts at 1350 °C for 8 h. The bending strength, fracture toughness and Young's modulus were about 156 MPa, 1.57 MPa m^1/2 and 43 GPa, respectively. The in vitro bioactivity of the bredigite ceramics was evaluated by investigating the apatite-formation ability in simulated body fluid (SBF) and the effect of ionic products from bredigite dissolution on the mouse fibroblasts cell line L929. In addition, the in vitro biocompatibility of the bredigite ceramics was evaluated by osteoblasts adhesion and proliferation assay. The results showed that bredigite ceramics could induce HAp formation in SBF. The products from bredigite dissolution significantly promoted cell growth at a certain concentration range. Furthermore, osteoblasts adhered and spread well on bredigite ceramics, and osteoblasts proliferation on bredigite ceramics was obvious.

Abstract

Diopside (CaMgSi₂O₆) powders and dense ceramics have been shown to be bioactive biomaterials for bone repair. The aim of this study is to prepare bioactive diopside scaffolds and examine their physicochemical and biological properties. X-ray diffraction, scanning electron microscopy (SEM), micro-computerized tomography and energy-dispersive spectrometry were used to analyse the composition, microstructure, pore size and interconnectivity of the diopside scaffolds. The mechanical strength and stability as well as the degradation of the scaffolds were investigated by testing the compressive strength, modulus and silicon ions released, respectively. Results showed that highly porous diopside scaffolds with varying porosity and high interconnectivity of 97% were successfully prepared with improved compressive strength and mechanical stability, compared to the bioglass and CaSiO₃ scaffolds. The bioactivity of the diopside scaffolds was assessed using apatite-forming ability in simulated body fluids (SBF) and by their support for human osteoblastic-like cell (HOB) attachment, proliferation and differentiation using SEM, and MTS and alkaline phosphatase activity assays, respectively. Results showed that diopside scaffolds possessed apatite-forming ability in SBF and supported HOB attachment proliferation and differentiation. Bioactive diopside scaffolds were prepared with excellent pore/structure art, and improved mechanical strength and mechanical stability, suggesting their possible applications for bone tissue engineering regeneration.

Abstract

Ideal bioceramic microspheres for bone regeneration need to be bioactive and degradable, but at the same time possess a controlled drug-release ability. The main disadvantage of the currently available microspheres is their failure to combine these properties. The aim of this study is to develop bioactive ceramic microspheres with optimal properties for use in bone-tissue regeneration. In this study, we utilize diopside (CaMgSi₂O₆, DP) with proven excellent bioactivity and degradation ability to develop microspheres by controlling their porosity and size, and further modify their surface with polymer to enhance and control their drug-loading/release ability. The phase composition, surface and inner microstructure, and porosity of DP microspheres were tested. Results indicate that carbon powders as porogens with various contents determined the porosity of the porous DP microspheres. The drug-loading and release ability of dexamethazone (DEX) from porous DP microspheres was regulated by their porosity and size. Poly(lactide-co-glycolide) modification forms a film on the surface of DP microspheres and resulted in an enhanced DEX-loading and release ability of the microspheres. Results presented here indicate that the developed DP microspheres have the potential to be used as bioactive filling materials for bone-tissue regeneration.

Abstract

In this research, the synthesis of nanocrystalline merwinite (2SiO₂–3CaO–MgO) bioactive ceramic was carried out by the sol–gel method. After crushing, obtained sol–gel derived bioceramic powder pressed uniaxially to produce cylindrical-like pellets, followed by sintering at 1300 °C. Via immersion in simulated body fluid (SBF) for various time intervals, the formation of apatite was characterized. Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FT-IR) studies were conducted both before and after immersion in SBF. The crystallization temperature of the merwinite was determined by thermal analysis. Attained results confirmed formation of apatite layer within the first day of soaking. Accordingly it can be concluded that merwinite is bioactive and might be used for preparation of implantable biomaterials.

Abstract

Hardystonite (Ca₂ZnSi₂O₇) ceramics were prepared by sintering hardystonite sol–gel derived powder compacts at 1350 °C for 5 h, and their sinterability and mechanical properties were investigated. The biocompatibility of hardystonite ceramics was evaluated by culturing bone marrow mesenchymal stem cells (BMMSC) on the ceramics. The results showed the bending strength and fracture toughness of hardystonite ceramics to be 136 MPa, and 1.24 MPa m^1/2, respectively. SEM showed that BMMSC were attached and spread well on the hardystonite ceramics. Our preliminary studies indicate that hardystonite ceramics possess improved bending strength and fracture toughness as compared to hydroxyapatite (HAp), and may possess good biocompatibility.

Abstract

Calcium silicate (CaSiO₃) ceramics have received considerable attention in recent years due to their excellent bioactivity and degradability. However, their poor chemical stability limits their biological applications. Hardystonite (Ca₂ZnSi₂O₇) ceramics are Ca–Si-based materials developed by incorporating zinc into the Ca–Si system to improve their chemical stability. However, the biological responses of Ca₂ZnSi₂O₇ to bone cells are unknown. The objective of this study is to investigate and compare the in vitro responses of human osteoblast-like cells (HOBs) and osteoclasts when cultured on Ca₂ZnSi₂O₇ and CaSiO₃ ceramic disks. The ability of Ca₂ZnSi₂O₇ ceramics to support HOB attachment, cytoskeleton organization, proliferation and differentiation was assessed by scanning electron microscopy, confocal microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, alkaline phosphatase activity and quantitative real-time polymerase chain reaction. Our results show that Ca₂ZnSi₂O₇ supported HOB attachment with a well-organized cytoskeleton structure, and significantly increased cellular proliferation and differentiation compared to CaSiO₃. In addition, Ca₂ZnSi₂O₇ showed increased expression levels of osteoblast-related mRNAs (alkaline phosphatase, collagen type I, osteocalcin, receptor activator of NF_κB ligand and osteoprotegerin) compared to CaSiO₃. Ca₂ZnSi₂O₇ ceramic supported the formation of mature and functional osteoclasts and formed resorption imprints. On CaSiO₃ ceramics, the cells failed to differentiate from the monocytes into osteoclasts. Taken together, these results indicate that Hardystonite ceramics are conducive to both types of bone cells, osteoblast-like cells and osteoclasts, suggesting their potential use for skeletal tissue regeneration and as coatings onto currently available orthopedic and dental implants.

Abstract

CaSiO₃ ceramics have been regarded as a potential bioactive material for bone regeneration. Strontium (Sr) as a trace element in human body has been found to have beneficial effects on bone formation. The aim of this study was to incorporate Sr into CaSiO₃ bioactive ceramics and to investigate their effect(s) on phase transition, sintering property, apatite-formation ability, ionic dissolution, and human bone-derived cells (HBDC) proliferation. Sr containing CaSiO₃ (Sr-CaSiO₃) ceramics at various concentrations (0–10% Sr) were prepared. The incorporation of Sr into CaSiO₃ promoted the phase transition from β to α-CaSiO₃ and enhanced ceramic densification but did not alter the mechanism and ability of apatite formation in SBF. The ionic dissolution rate of the Sr-CaSiO₃ decreased compared to the CaSiO₃. The addition of Sr decreased pH value in SBF. The effect of Sr-CaSiO₃ extracts, carried out according to the International Standard Organization, on HBDC proliferation was evaluated. At high extract concentration (100 and 200 mg/mL), CaSiO₃ was found to stimulate HBDC proliferation, however, the incorporation of Sr into CaSiO₃ stimulated HBDC proliferation even at low extract concentration (ranging from 12.5, 25 to 50 mg/mL). Our results indicate that Sr-CaSiO₃ ceramics improved the physical and biological properties of the pure CaSiO₃ ceramics.

Abstract

The host response to titanium alloy (Ti–6Al–4V) is not always favorable as a fibrous layer may form at the skeletal tissue–device interface, causing aseptic loosening. Recently, sphene (CaTiSiO₅) ceramics were developed by incorporating Ti in the Ca–Si system, and found to exhibit improved chemical stability. The aim of this study is to evaluate the in vitro response of human osteoblast-like cells, human osteoclasts and human microvascular endothelial cells to sphene ceramics and determine whether coating Ti–6Al–4V implants with sphene enhances anchorage to surrounding bone. The study showed that sphene ceramics support human osteoblast-like cell attachment with organized cytoskeleton structure and express increased mRNA levels of osteoblast-related genes. Sphene ceramics were able to induce the differentiation of monocytes to form functional osteoclasts with the characteristic features of f-actin and α_vβ₃ integrin, and express osteoclast-related genes. Human endothelial cells were also able to attach and express the endothelial cell markers ZO-1 and VE-Cadherin when cultured on sphene ceramics. Histological staining, enzyme histochemistry and immunolabelling were used for identification of mineralized bone and bone remodelling around the coated implants. Ti–6Al–4V implants coated with sphene showed new bone formation and filled the gap between the implants and existing bone in a manner comparable to that of the hydroxyapatite coatings used as control. The new bone was in direct contact with the implants, whereas fibrous tissue formed between the bone and implant with uncoated Ti–6Al–4V. The in vivo assessment of sphene-coated implants supports our in vitro observation and suggests that they have the ability to recruit osteogenic cells, and thus support bone formation around the implants and enhance osseointegration.

Abstract

In this study we have developed Ca₃ZrSi₂O₉ (Baghdadite) ceramics by incorporating Zirconium in Ca–Si system and determined their biological properties. Ca₃ZrSi₂O₉ ceramics possess apatite-formation ability in simulated body fluid, indicating their potential bioactivity. The response of human osteoblast like cells (HOB), osteoclast and endothelial cells when cultured on Ca₃ZrSi₂O₉ ceramics was investigated. Scanning electron microscopy and immunofluorescence studies demonstrated that this material supports HOB cell attachment with organized cytoskeleton structure. Compared to CaSiO₃, Ca₃ZrSi₂O₉ ceramics induced increased HOB proliferation and differentiation as shown by increased methyltetrazidium salt (MTS), alkaline phosphatase activity, and mRNA expression levels of bone-related genes (Collagen type I, alkaline phosphatase, Bone Sialoprotein, receptor activator of NF-κB ligand and osteoprotegerin). Ca₃ZrSi₂O₉ ceramics supported the fusion of monocytes to form functional osteoclasts with their characteristic features of f-actin ring structures and the expression of α_vβ₃ integrin consistent with functional activity. Osteoclasts cultured on Ca₃ZrSi₂O₉ expressed increased levels of osteoclast-related genes; Cathepsin K, Carbonic Anhydrase II, Matrix metalloproteinase-9, receptor activator of NF-κB and Calcitonin Receptor, consistent with the formation of functional osteoclasts. In addition to HOB and osteoclasts, Ca₃ZrSi₂O₉ supported the attachment of endothelial cells, which expressed the endothelial cell markers; ZO-1 and VE-Cadherin. Results presented here indicate that Ca₃ZrSi₂O₉ ceramics have the potential for applications in bone tissue regeneration.

Abstract

In this study we developed novel scaffolds through the controlled substitution and incorporation of strontium and zinc into a calcium–silicon system to form Sr–Hardystonite (Sr–Ca₂ZnSi₂O₇, Sr–HT). The physical and biological properties of Sr–HT were compared to Hardystonite (Ca₂ZnSi₂O₇) [HT]. We showed that Sr–HT scaffolds are porous with interconnected porous network (interconnectivity: 99%) and large pore size (300–500 μm) and an overall porosity of 78%, combined with a relatively high compressive strength (2.16 ± 0.52 MPa). These properties are essential for enhancing bone ingrowth in load-bearing applications. Sr–HT ceramic scaffolds induced the attachment and differentiation of human bone derived cells (HOB), compared to that for the HT scaffolds. Sr–HT scaffolds enhanced expression of alkaline phosphatase, Runx-2, osteopontin, osteocalcin and bone sialoprotein. The in vivo osteoconductivity of the scaffolds was assessed at 3 and 6 weeks following implantation in tibial bone defects in rats. Histological staining revealed rapid new growth of bone into the pores of the 3D scaffolds with the Sr–HT and HT, relative to the β-tricalcium phosphate (β-TCP). In vivo, HT and Sr–HT produced distinct differences in the patterns of degradation of the materials, and their association with TRAP positive osteoclast-like cells with HT appearing more resistant compared to both Sr–HT and β-TCP.

Abstract

Calcium silicate (CaSiO₃) ceramics were prepared by pressureless sintering. The effects of the sintering temperature and holding time on the mechanical strength, porosity and linear shrinkage of the ceramics, and the adhesion and proliferation of bone marrow mesenchymal stem cells (MMSC) were investigated. When the sintering temperature and holding time increased, the linear shrinkage of the ceramics increased and the porosity decreased. The CaSiO₃ ceramics sintered at 1100 °C for 5 h revealed a mechanical strength of 95.03 ± 7.11 MPa, similar to the bending strength of human cortical bone. In addition, the adhesion and proliferation of MMSC on the CaSiO₃ ceramics was examined and the results showed that the ceramics supported cell adhesion and proliferation, which indicated good biocompatibility. Our results suggested that CaSiO₃ ceramics might be a potential bioactive material as bone implant.

Abstract

Self-setting biomaterials are widely used for tissue repair and regeneration. Calcium sulfate hemihydrate has been used for many years as a self-setting biomaterial due to its good setting properties. However, too fast a degradation rate and lack of bioactivity have limited its application in orthopaedic field. Herein, tricalcium silicate was introduced into calcium sulfate hemihydrate (CaSO₄ · 1/2H₂O) to form a calcium sulfate hemihydrate-based composite, and its behavior as a cement was studied in comparison with pure calcium sulfate hemihydrate. The results indicated that the workability and setting time of the composite pastes are higher than those of pure CaSO₄ · 1/2H₂O, and the composite pastes showed much better short- and long-term mechanical properties than those of pure CaSO₄ · 1/2H₂O. Moreover, the biphasic specimens showed significantly improved bioactivity and degradability compared with those of pure CaSO₄ · 1/2H₂O, indicating that the composite cements might have a significant clinical advantage over the traditional CaSO₄ · 1/2H₂O cement.

Abstract

Bioactive composite bone cements were obtained by incorporation of tricalcium silicate (Ca₃SiO₅, C₃S) into a brushite bone cement composed of β-tricalcium phosphate [β-Ca₃(PO₄)₂, β-TCP] and monocalcium phosphate monohydrate [Ca(H₂PO₄)₂·H₂O, MCPM], and the properties of the new cements were studied and compared with pure brushite cement. The results indicated that the injectability, setting time and short- and long-term mechanical strength of the material are higher than those of pure brushite cement, and the compressive strength of the TCP/MCPM/C₃S composite paste increased with increasing aging time. Moreover, the TCP/MCPM/C₃S specimens showed significantly improved in vitro bioactivity in simulated body fluid and similar degradability in phosphate-buffered saline as compared with brushite cement. Additionally, the reacted TCP/MCPM/C₃S paste possesses the ability to stimulate osteoblast proliferation and promote osteoblastic differentiation of the bone marrow stromal cells. The results indicated that the TCP/MCPM/C₃S cements may be used as a bioactive material for bone regeneration, and might have significant clinical advantage over the traditional β-TCP/MCPM brushite cement.

Abstract

Bioactive and degradable macroporous bioceramics play an important role in clinical applications. In the present study, 45S5 bioglass reinforced macroporous calcium silicate ceramics (45BG-reinforced MCSCs) were fabricated. The effect of bioglass additives on compressive strength and open porosity of the samples was investigated, and the bioactivity and degradability of the obtained reinforced samples were also evaluated. The 45S5 bioglass additive was found to be effective to increase the strength of the MCSCs by the liquid-phase sintering mechanism. The optimum amount of bioglass additives was 5 wt.% and the compressive strength of the reinforced samples was approximately 2 times higher as compared to the pure macroporous calcium silicate ceramics (MCSCs). The compressive strength of the reinforced samples with about 50% porosity reached 112.47 MPa, which was similar to those of the cortical bones. After soaking in simulated body fluid (SBF), hydroxycarbonate apatite (HCA) layer was formed on the surface of the 45BG-reinforced MCSCs. Furthermore, the degradation rate of the reinforced samples was just about one-third of those pure MCSCs. Our results indicated that degradable 45BG-reinforced MCSCs possess excellent mechanical strength and bioactivity, and may be used as bioactive and degradable biomaterials for hard tissue prosthetics or bone tissue engineering applications.

Abstract

Porous calcium silicates (CaSiO₃, WT) are regarded as a potential bioactive material for bone tissue engineering. However, their insufficient mechanical strength and high dissolution (degradation) limit their biological applications. The aim of this study is to surface modify WT scaffolds with poly(d,l-lactic acid) (PDLLA) to improve their mechanical and biological properties. The phase composition, microstructure, porosity and interconnectivity of WT and PDLLA-modified WT (WTPL) scaffolds were analyzed by X-ray diffraction, scanning electron microscopy and micro-computerized tomography. The WTPL scaffolds maintained a more uniform and continuous inner network, compared to that of the WT scaffolds, while maintaining the pore size, porosity and interconnectivity of the original materials. The compressive strength, compressive modulus and percentage strain of the WT and WTPL scaffolds were assessed in air and phosphate-buffered saline. PDLLA modification significantly improved the compressive strength and decreased the brittleness of the WT scaffolds. The weight loss and apatite-forming ability of the two scaffolds were evaluated by soaking them in simulated body fluid (SBF) for 1, 3, 7, 14 and 28 days. PDLLA modification decreased the dissolution of the WT scaffolds while maintaining their apatite-forming ability in SBF. In addition, PDLLA modification improved the spreading and viability of human bone-derived cells. Our results indicate that PDLLA-modified CaSiO₃ scaffolds possess improved mechanical and biological properties, suggesting their potential application for bone tissue regeneration.

Abstract

Nowadays, the scientific community widely accepts the statement that silicon-substituted calcium phosphates have better biological properties compared to pure calcium phosphates. For example, a review published in this journal in 2007 started with the sentence “Silicon (Si) substitution in the crystal structures of calcium phosphate (CaP) ceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP) generates materials with superior biological performance to stoichiometric counterparts” [1]. A critical look at published articles demonstrates that this sentence is controversial and somehow misleading, because there is no experimental evidence that Si ions are released from Si-substituted calcium phosphates at therapeutic concentrations, and because there is no study linking the improved biological performance of Si-substituted calcium phosphates to Si release. The aim of this article is to explain this statement in more details.