Assessment of natural and synthetic wollastonite as source for bioceramics preparation

High temperature CaSiO3-Ca3(PO4)2 ceramic promotes osteogenic differentiation in adult human mesenchymal stem cells

Silicophosphate calcium ceramics are widely used in orthopedic and oral surgery applications because of their properties for stimulating bone formation and bone bonding. These bioceramics, together with multipotent undifferentiated adult human mesenchymal stem cells, are serious candidates in the field of bone tissue engineering and regenerative medicine. For this reason, the influence of a novel 30 wt%CaSiO₃ - 70 wt%Ca₃(PO₄)₂ ceramic over a primary adult human mesenchymal stem cells culture has been investigated in this study, observing a total colonization of the biomaterial by cells at 21 days. The osteoinductive capacity of the materials was also studied: alkaline phosphatase activity, gene quantification of osteoblastic genes and calcium deposits stained by Alizarin Red test, showed evidences of osteogenic differentiation of adult human mesenchymal stem cells seeded with this bioceramic both in growth medium and osteogenic medium. Therefore, the 30 wt%CaSiO₃ - 70 wt%Ca₃(PO₄)₂ bioceramic represents a potential scaffold which could be used in the field of biomaterials for bone tissue engineering, allowing cell adhesion, proliferation and promoting osteogenic differentiation of adult human mesenchymal stem cells.

Histological and Histomorphometric Analyses of Two Bovine Bone Blocks Implanted in Rabbit Calvaria

This study compared the osteogenic potential of two types of bovine bone blocks. Blocks were obtained by either sintered or a nonsintered process. Calvaria were surgically exposed in 20 rabbits. In each animal, six 0.5-mm-diameter cortical microperforations were drilled with a carbide bur before grafting to promote graft irrigation. The sintered (group 1) and nonsintered (group 2) bovine bone blocks (6 mm diameter, 5 mm high) were bilaterally screwed onto calvarial bone. Blocks were previously prepared from a larger block using a trephine bur. Rabbits were sacrificed after 6 and 8 weeks for the histological and histomorphometric analyses. Samples were processed using the historesin technique. The quantitative and qualitative analyses of the newly formed bone were undertaken using light microscopy. Both groups showed modest new bone formation and remodeling. At the 8-week follow-up, the sintered group displayed significantly lower bone resorption (average of 10% in group 1 and 25% in group 2) and neo-formation (12.86 ± 1.52%) compared to the nonsintered group (16.10 ± 1.29%) at both follow-ups (p < 0.05). One limitation of the present animal model is that the study demonstrates that variations in the physico-chemical properties of the bone substitute material clearly influence the in vivo behavior.

In Vitro Bioactivity and Cell Biocompatibility of a Hypereutectic Bioceramic

Two dense biphasic ceramics, with a hypereutectic composition of 30 wt % CaSiO3–70 wt % Ca3(PO4)2, were synthesized by a solid-state reaction of homogeneous pressed combinations of previously synthesized synthetic CaSiO3 and Ca3(PO4)2 powders. The objective was to produce a dense structure to generate large enough in situ pores for the ceramic to be used in tissue engineering. To develop such a structure, two grain sizes of CaSiO3 were used (63–100 µm and 100–150 μm) and some of their properties were studied in vitro, as they are relevant for tissue engineering. X-ray diffraction analysis, μ-Raman spectroscopy, diametrical compression test, and scanning electron microscopy with elemental mapping showed a coarse-grained homogeneous microstructure for the materials, which consisted of wollastonite (α-CaSiO3) and tricalcium phosphate (α-Ca3(PO4)2), with adequate mechanical properties for implantation. In vitro bioactivity was evaluated in simulated body fluid (SBF) by exploring a hydroxyapatite (HA)-like formation. The results showed that tricalcium phosphate grains dissolved more preferentially than those of wollastonite, but not fast enough to leave a pore before the surface was coated with an HA-like layer after soaking only for three days. Biocompatibility was evaluated by in vitro cell experiments, which showed cell proliferation, adhesion, and spreading on the ceramic surface. This ceramic is expected to be used as a bone graft substitute.

Calcium silicate as a graft material for bone fractures: a systematic review

Objective

The goal of this review was to determine whether calcium silicate (wollastonite) as a bone graft material is a viable alternative to autogenous bone or whether the evidence base for its use is weak.

Methods

In this systematic review, electronic databases (MEDLINE/PubMed and BVS) were searched for relevant articles in indexed journals. Articles published in a 10-year period were identified (n = 48). After initial selection, 17 articles were assessed for eligibility; subsequently, seven articles were excluded and 10 articles were included.

Results

Among the studies included, 20% emphasized the importance of randomization, which adds reliability to the study, minimizing the risk of bias. High variability was observed in the material used, such as additives, amounts, dosage, and chemical alterations, rendering direct comparison among these studies impossible. The experimental periods varied considerably; one of the studies did not include statistical analysis, weakening the evaluation. Nonetheless, the true potential of wollastonite as a graft material conducive to new bone formation was reported in all studies.

Conclusion

The results support the use of wollastonite as a bone graft material. The initial research question was answered despite the significant variability observed among these preclinical studies, which hindered the precision of this analysis.

A New Biphasic Dicalcium Silicate Bone Cement Implant

This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C₂S) cement. Biphasic α´_L + β-C₂S_ss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF) and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C₂S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´_L + β-C₂S_ss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23) obtained higher bone-to-implant contact (BIC) percentage values (better quality, closer contact) in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic). The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

"Steel-Concrete" Inspired Biofunctional Layered Hybrid Cage for Spine Fusion and Segmental Bone Reconstruction

In this paper we report a "steel-concrete" inspired layered hybrid spine cage combining a titanium mesh and a bioceramic scaffold, which were welded together through a bioglass bonding layer using a novel multistep manufacturing methodology including three-dimensional slip deposition, gel casting, freeze-drying, and cosintering. The interfacial welding strength achieved 27 ± 0.7 MPa, indicating an excellent structural integrity of the hybrid cage construct. The biocramic scaffold layer consisting of wollastonite and hydroxyapatite had an interconnected, highly porous structure with a pore size of 100-500 μm and a porosity of >85%, well fufilling the structural requirements of bone regeneration. Simulated body fluid immersion assay showed that the hybrid cage exhibited excellent biodegradability to facilitate rapid bone-like apatite formation. In vitro studies demonstrated that the bioceramic scaffold on the hybrid cage supported attachment, spreading, growth, and migration of bone/vessel-forming cells and triggered osteogenic differentiation of human mesenchymal stem cells. In vivo studies further suggested that the bioceramic scaffold on the hybrid cage could actively promote fast generation of new bone tissues within 12 weeks of implantation in a rabbit femoral condyle model. This study has provided a new design and fabrication methodology of hybrid cages by integrating strong mechanical properties with excellent biological activities including osteoinductivity and bone regeneration ability, for spine fusion and segmental bone reconstruction.

Sorption on eggshell waste--a review on ultrastructure, biomineralization and other applications

The structure, adsorption behavior and applications of eggshell waste materials have been reviewed. The ultrastructure of eggshell particles has been discussed to understand the pore structure as well as the surface geometry of the materials leading to its multifarious applicability. Besides, the ultrastructure studies give full information regarding the chemical constituents of egghell particles as well as eggshell membranes. The process of biomineralization in living organisms, their consequent effect of controlling the formation of inorganic-organic composites propelling their application in biomimetic designing of advanced composites with optimized novel properties leading to advances in materials design have been discussed. Utilization of eggshell waste materials for the removal of organic dyes and heavy inorganic ions has been reviewed with suitable models for understanding their adsorption quality and capacity. The applications of these materials in various fields of research have been extensively discussed.

Nanosized mesoporous bioactive glass/poly(lactic-co-glycolic acid) composite-coated CaSiO3 scaffolds with multifunctional properties for bone tissue engineering

It is of great importance to prepare multifunctional scaffolds combining good mechanical strength, bioactivity, and drug delivery ability for bone tissue engineering. In this study, nanosized mesoporous bioglass/poly(lactic-co-glycolic acid) composite-coated calcium silicate scaffolds, named NMBG-PLGA/CS, were successfully prepared. The morphology and structure of the prepared scaffolds were characterized by scanning electron microscopy and X-ray diffraction. The effects of NMBG on the apatite mineralization activity and mechanical strength of the scaffolds and the attachment, proliferation, and alkaline phosphatase activity of MC3T3 cells as well as drug ibuprofen delivery properties were systematically studied. Compared to pure CS scaffolds and PLGA/CS scaffolds, the prepared NMBG-PLGA/CS scaffolds had greatly improved apatite mineralization activity in simulated body fluids, much higher mechanical property, and supported the attachment of MC3T3 cells and enhanced the cell proliferation and ALP activity. Furthermore, the prepared NMBG-PLGA/CS scaffolds could be used for delivering ibuprofen with a sustained release profile. Our study suggests that the prepared NMBG-PLGA/CS scaffolds have improved physicochemical, biological, and drug-delivery property as compared to conventional CS scaffolds, indicating that the multifunctional property of the prepared scaffolds for the potential application of bone tissue engineering.

Effect of Mg and Si co-substitution on microstructure and strength of tricalcium phosphate ceramics

Magnesium and silicon co-doped tricalcium phosphate (TCP) ceramics with compositions corresponding to 0, 5 and 10wt% CaMg(SiO3)2 in the system Ca3(PO4)2-CaMg(SiO3)2 were obtained by conventional sintering of compacted mixtures of Ca3(PO4)2, MgO, SiO2 and CaCO3 powders at temperatures between 1100 and 1450°C. Microstructural analyses were performed by X-ray diffraction and field emission scanning electron microscopy with energy dispersive spectroscopy. Major phases in the obtained ceramics were β- or α+β-tricalcium phosphate containing Mg and Si in solid solution. Certain amounts of liquid were formed during sintering depending on composition and temperature. There were found significant differences in distributions of strength determined by the diametral compression of disc tests (DCDT). Failure strengths were controlled by microstructural defects associated with phase development. Mg and Si additions were found to be effective to improve densification and associated strength of TCP bioceramics due to the enhancement of sintering by the low viscosity liquids formed. The highest density and strength were obtained for the TCP ceramic containing 5wt% CaMg(SiO3)2 sintered at 1300°C. Cracking and porosity increased at higher temperatures due to grain growth and swelling.

The stimulation of osteogenic differentiation of mesenchymal stem cells and vascular endothelial growth factor secretion of endothelial cells by β-CaSiO3/β-Ca3(PO4)2 scaffolds

Porous β-CaSiO3/β-Ca3(PO4)2 (β-CS/β-TCP) composite scaffolds have been previously shown to promote bone formation in vivo. However, the mechanisms underlying such beneficial effects remain unclear. In this study, we recreated an extracellular environment using the extracts of β-CS/β-TCP composites developed in our previous in vivo study, and investigated the effects of the extracts on osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) and its related mechanisms. The angiogenic potential of the extracts was also evaluated using human umbilical vein endothelial cells (HUVECs). In the absence of osteogenic supplements, the osteogenic differentiation of rBMSCs was detected by alkaline phosphatase (ALP) activity assay and the messenger RNA expression of a panel of osteoblast markers. The results showed that the soluble ions of porous β-CS/β-TCP composites were capable of promoting cell viability, directly inducing cell differentiation. The increase in phosphorylation of AMP-activated protein kinase (AMPK) and ERK1/2 were observed in rBMSCs cultured in β-CS/β-TCP composite extracts. The ALP expression, calcium deposition, and ERK1/2 phosphorylation of rBMSCs, which was promoted by ions released from β-CS/β-TCP composites, were blocked by an AMPK inhibitor, Compound C. These results indicate that bioactive ions extracted from β-CS/β-TCP composites could stimulate the osteogenic differentiation of rBMSCs via the AMPK-Erk1/2 pathway. Interestingly, the secretion of vascular endothelial growth factor and the viability of HUVECs were shown to be enhanced in the presence of extracts from the β-CS/β-TCP composite scaffolds. Our findings suggest that 50 or 80% wt. CS could promote bone regeneration by stimulating osteogenesis and angiogenesis.

The enhancement of bone regeneration by a combination of osteoconductivity and osteostimulation using β-CaSiO3/β-Ca3(PO4)2 composite bioceramics

β-Tricalcium phosphate (β-TCP) is osteoconductive, while β-calcium silicate (β-CS) is bioactive with osteostimulative properties. Porous β-CaSiO(3)/β-Ca(3)(PO(4))(2) composite bioceramic scaffolds with various β-TCP:β-CS ratios were designed to combine both osteoconductivity and osteostimulation in order to enhance bone regeneration. The composite scaffolds were implanted in critical sized femur defects (6×12 mm) for 4, 12 and 26weeks with pure β-TCP and β-CS scaffolds as the controls. The in vivo biodegradation and bone regeneration of the specimens were investigated using sequential histological evaluations, immunohistochemical examination and micro-computed tomography technology. The results showed that the scaffolds with 50 and 80 wt.% β-CS dramatically enhanced the amount of newly formed bone and reduced the degradation rate. In contrast, porous β-CS displayed poor new bone formation due to its rapid degradation, while porous β-TCP showed moderate bone regeneration starting on the surface of the implants, due to a lack of osteostimulation. More importantly, the scaffolds with 50 and 80 wt.% β-CS not only had excellent osteoconductivity, but also stimulated rapid bone formation, and they could degrade progressively at a rate matching the regeneration of new bone. In summary, our findings indicated that the degradation rate and bioactivity of β-CS/β-TCP composite bioceramic scaffolds could be adjusted by controlling the ratio of β-CS to β-TCP, suggesting the potential application of β-CS/β-TCP composite bioceramic scaffolds with 50 and 80 wt.% β-CS component in hard tissue regeneration and bone tissue engineering.

Feasibility of ceramic-polymer composite cryogels as scaffolds for bone tissue engineering

The purpose of the current study was to investigate whether the cryopolymerization technique is capable of producing suitable scaffolds for bone tissue engineering. Cryopolymers made of 2-hydroxyethyl methacrylate and acrylic acid with (W1 and W20) and without (W0) wollastonite particles were prepared. The elastic modulus of the specimens rose one order of magnitude from W1 to W20. Total porosity reached 56% for W0, 72% for W1 and 36% for W20, with pore sizes of up to 2 mm, large interconnection sizes of up to 1 mm and small interconnection sizes of 50-80 µm on dry specimens. Cryogels swell up to 224 ± 17% for W0, 315 ± 18% for W1 and 231 ± 27% for W20 specimens, while maintaining the integrity of the bodies. Pore sizes > 5 mm can be observed for swollen specimens. The biocompatibility of the samples was tested using human mesenchymal stem cells isolated from bone marrow and adipose tissues. Both types of cells attached and grew on the three tested substrates, colonized their inner regions and organized an extracellular cell matrix. Fibronectin and osteopontin levels decreased in the media from cells cultured on W20 samples, likely due to increased binding on the ECM deposited by cells. The osteoprotegerin-to-receptor activator of nuclear factor-κB ligand secretion ratios increased with increasing wollastonite content. Altogether, these results indicate that an appropriate balance of surface properties and structure that favours stromal cell colonization in the porous cryogels can be achieved by modulating the amount of wollastonite.

Comparison of the Biological Behavior of Wollastonite Bioceramics Prepared from Synthetic and Natural Precursors

Wollastonite bioceramics prepared from synthetic and natural precursors were implanted in rats in bone and subcutaneous tissues. The implant sites were excised after 7, 30 and 120 days, fixed, dehydrated, embedded in paraffin wax for serial cutting and examined under transmitted light microscope. It was found a very similar behavior for both wollastonite bioceramics. They were biocompatible, bioactive and biodegradable when implanted in rat bone. The synthetic ceramic was more reabsorbable than the one from natural powder. When implanted in subcutaneous rat tissue, both materials elicited a mild initial inflammatory reaction that practically disappeared after 120 days. Both materials were encapsulated with a very thin fibrous capsule and slightly reabsorbed at their surfaces. None of the materials induced ectopic osteogenesis. According to the results, the studied materials seem to be able for manufacturing reabsorbable bone implants.