Injectable β -TCP/MCPM cement associated with mesoporous silica for bone regeneration: characterization and toxicity evaluation

The effect of supplementing the calcium phosphate cement containing poloxamer 407 on cellular activities

Calcium phosphate cement (CPC) is generally used for bone repair and augmentation. Poloxamers are tri-block copolymers that are used as surfactants but have applications in drug and antibiotic delivery. However, their biological effects on bone regeneration systems remain unelucidated. Here, we aimed to understand how supplementing the prototype CPC with poloxamer would impact cellular activity and its function as a bone-grafting material. A novel CPC, modified beta-tricalcium phosphate (mβ-TCP) powder, was developed through a planetary ball-milling process using a beta-tricalcium phosphate (β-TCP). The mβ-TCP dissolves rapidly and accelerates hydroxyapatite precipitation; successfully shortening the cement setting time and enhancing the strength. Furthermore, the addition of poloxamer 407 to mβ-TCP could reduce the risk of leakage from bone defects and improve fracture toughness while maintaining mechanical properties. In this study, the poloxamer addition effects (0.05 and 0.1 g/mL) on the cellular activities of MC3T3-E1 cells cultured in vitro were investigated. The cell viability of mβ-TCP containing poloxamer 407 was similar to that of mβ-TCP. All specimens showed effective cell attachment and healthy polygonal extension of the cytoplasm firmly attached to hydroxyapatite (HA) crystals. Therefore, even with the addition of poloxamer to mβ-TCP, it does not have a negative effect to osteoblast growth. These data demonstrated that the addition of poloxamer 407 to mβ-TCP might be considered a potential therapeutic application for the repair and regeneration of bone defects.

Development and evaluation of local regenerative biomimetic bone-extracellular matrix scaffold loaded with nano-formulated quercetin for orthopedic fractures

The prevalence of bone injuries is greatly increasing each year and the proper healing of fractures without any complications is very challenging. Self-setting calcium phosphate cements (CPCs) have attracted great attention as bioactive synthetic bone substitutes. Quercetin (QT) is a multipurposed drug with reported bone-conserving properties. The loading of QT and QT-phospholipid complex within nanostructured lipid carriers (NLC) was proposed to overcome the poor physical properties of the drug and to introduce the use of bioactive excipients as phospholipids and olive oil. The aim of this work was to formulate a regenerative scaffold loaded with nano-formulated QT for local treatment of orthopedic fractures. For the first time, scaffolds composed of brushite CPC were prepared and loaded with quercetin lipid nano-systems. In vitro tests proved that the addition of lipid nano-systems did not deteriorate the properties of CPC where QT-NLC/CPC showed an adequate setting time, appropriate compressive strength, and porosity. The scanning electron microscope confirmed maintenance of nanoparticles integrity within the cement. Using a rat femur bone defect animal model, the histological results showed that the QT-NLC/CPC had a superior bone healing potential compared to crude unformulated QT/CPC. In conclusion, QT-NLC /CPC are promising lipid nano-composite materials that could enhance bone regeneration.

Injectable bone cements: What benefits the combination of calcium phosphates and bioactive glasses could bring?

Out of the wide range of calcium phosphate (CaP) biomaterials, calcium phosphate bone cements (CPCs) have attracted increased attention since their discovery in the 1980s due to their valuable properties such as bioactivity, osteoconductivity, injectability, hardening ability through a low-temperature setting reaction and moldability. Thereafter numerous researches have been performed to enhance the properties of CPCs. Nonetheless, low mechanical performance of CPCs limits their clinical application in load bearing regions of bone. Also, the in vivo resorption and replacement of CPC with new bone tissue is still controversial, thus further improvements of high clinical importance are required. Bioactive glasses (BGs) are biocompatible and able to bond to bone, stimulating new bone growth while dissolving over time. In the last decades extensive research has been performed analyzing the role of BGs in combination with different CaPs. Thus, the focal point of this review paper is to summarize the available research data on how injectable CPC properties could be improved or affected by the addition of BG as a secondary powder phase. It was found that despite the variances of setting time and compressive strength results, desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs. The published data also revealed that the degradation rate of CPCs is significantly improved by BG addition. Moreover, the presence of BG in CPCs improves the in vitro osteogenic differentiation and cell response as well as the tissue-material interaction in vivo.

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Properties of injectable calcium phosphate bone cements and bioactive glasses are discussed.

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Benefits that BG addition to CPC could bring are highlighted.

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Desirable injectable properties of bone cements can be achieved by the inclusion of BGs into CPCs.

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The presence of BG in CPC advances in vitro and in vivo response of the composites.

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Future research direction of BG containing injectable CPC composites are provided.

Titanium reinforced calcium phosphate improves bone formation and osteointegration in ovine calvaria defects: a comparative 52-weeks study

In a 52-week ovine calvaria implantation model, the restoration of cranial defects with a bare titanium mesh (Ti-mesh) and a titanium mesh embedded in a calcium phosphate (CaP-Ti) were evaluated in seven animals. During the study, no major clinical abnormalities were observed, and all sheep presented a normal neurologic assessment. Blood and CSF analysis, made at termination, did not show any abnormalities. No indentation of the soft tissue was observed for either test article; however, the Ti-mesh burr-hole covers were associated with filling of the calvarial defect by fibrous tissue mainly. Some bone formation was observed at the bottom of the created defect, but no significant bone was formed in the proximity of the implant. The defect sites implanted with CaP-Ti were characterized by a moderate degradation of the calcium phosphate that was replaced by mature bone tissue. Calcium-phosphate-filled macrophages were observed in all animals, indicating that they might play a vital role in osteogenesis. The newly formed bone was present, especially at the bony edges of the defect and on the dura side. Integration of the titanium mesh in a calcium phosphate improved bone formation and osteointegration in comparison to a bare titanium mesh.

Effects of Silicon Compounds on Biomineralization, Osteogenesis, and Hard Tissue Formation

Bioinspired stem cell-based hard tissue engineering includes numerous aspects: The synthesis and fabrication of appropriate scaffold materials, their analytical characterization, and guided osteogenesis using the sustained release of osteoinducing and/or osteoconducting drugs for mesenchymal stem cell differentiation, growth, and proliferation. Here, the effect of silicon- and silicate-containing materials on osteogenesis at the molecular level has been a particular focus within the last decade. This review summarizes recently published scientific results, including material developments and analysis, with a special focus on silicon hybrid bone composites. First, the sources, bioavailability, and functions of silicon on various tissues are discussed. The second focus is on the effects of calcium-silicate biomineralization and corresponding analytical methods in investigating osteogenesis and bone formation. Finally, recent developments in the manufacturing of Si-containing scaffolds are discussed, including in vitro and in vivo studies, as well as recently filed patents that focus on the influence of silicon on hard tissue formation.