Nano‑calcium phosphate bone cement based on Si-stabilized α-tricalcium phosphate with improved mechanical properties

Investigation on the size and percentage effects of magnesium nanoparticles on thermophysical properties of reinforced calcium phosphate bone cement by molecular dynamic simulation

In recent years, bone materials and cement innovation have made extraordinary strides. Calcium phosphate cement (CPC) regenerates body tissues and repairs bone and dental defects. Since the presence of nanoparticles (NPs) increased the initial cement strength in terms of the reduction of porosity, magnesium (Mg) NPs were used because of their unique properties. In this study, the effects of various Mg NP percentages and sizes on reinforced cement thermal behavior and mechanical behavior are investigated using the molecular dynamics (MD) simulation method. The changes of Young's modulus (YM), maximum temperature (MT), and ultimate strength (US) were investigated for this reason. The US, YM, and MT of the reinforced cement sample improved from 0.879 to 0.171 MPa to 1.326 and 0.255 MPa, respectively, and from 1321 to 1403 K by raising the NPs percentage to 4%. The radius increase of NPs to 16 Å enhanced the US, YM, and MT to 0.899 MPa, 0.179 MPa, and 1349 K. The MT decreased to 1275 K. The quantity and size of the Mg NPs significantly enhanced the mechanical behavior of the finished cement, according to the findings.

Enhancing Stability of High-Concentration β-Tricalcium Phosphate Suspension for Biomedical Application

We propose a novel process to efficiently prepare highly dispersed and stable Tricalcium Phosphate (β-TCP) suspensions. TCP is coupled with a polymer to enhance its brittleness to be used as an artificial hard tissue. A high solid fraction of β-TCP is mixed with the polymer in order to improve the mechanical strength of the prepared material. The high solid fractions led to fast particle aggregation due to Van der Waals forces, and sediments appeared quickly in the suspension. As a result, we used a dispersant, dispex AA4040 (A40), to boost the surface potential and steric hindrance of particles to make a stable suspension. However, the particle size of β-TCP is too large to form a suspension, as the gravity effect is much more dominant than Brownian motion. Hence, β-TCP was subjected to wet ball milling to break the aggregated particles, and particle size was reduced to ~300 nm. Further, to decrease sedimentation velocity, cellulose nanocrystals (CNCs) are added as a thickening agent to increase the overall viscosity of suspension. Besides the viscosity enhancement, CNCs were also wrapped with A40 micelles and increase the stability of the suspension. These CNC/A40 micelles further facilitated stable suspension of β-TCP particles with an average hydration radius of 244.5 nm. Finally, β-TCP bone cement was formulated with the suspension, and the related cytotoxicity was estimated to demonstrate its applicability for hard tissue applications.

A Three-Parameter Weibull Distribution Method to Determine the Fracture Property of PMMA Bone Cement

Poly (methyl methacrylate) (PMMA) bone cement is an excellent biological material for anchoring joint replacements. Tensile strength ft and fracture toughness KIC have a considerable impact on its application and service life. Considering the variability of PMMA bone cement, a three-parameter Weibull distribution method is suggested in the current study to evaluate its tensile strength and fracture toughness distribution. The coefficients of variation for tensile strength and fracture toughness were the minimum when the characteristic crack of PMMA bone cement was αch∗=8dav. Using the simple equation αch∗=8dav and fictitious crack length Δαfic=1.0dav, the mean value μ (= 43.23 MPa), minimum value ftmin (= 26.29 MPa), standard deviation σ (= 6.42 MPa) of tensile strength, and these values of fracture toughness (μ = 1.77 MPa⋅m1/2, KICmin = 1.02 MPa⋅m1/2, σ = 0.2644 MPa⋅m1/2) were determined simultaneously through experimental data from a wedge splitting test. Based on the statistical analysis, the prediction line between peak load Pmax and equivalent area Ae1Ae2 was obtained with 95% reliability. Nearly all experimental data are located within the scope of a 95% confidence interval. Furthermore, relationships were established between tensile strength, fracture toughness, and peak load Pmax. Consequently, it was revealed that peak load might be used to easily obtain PMMA bone cement fracture characteristics. Finally, the critical geometric dimension value of the PMMA bone cement sample with a linear elastic fracture was estimated.

α-TCP-based Calcium Phosphate Cements: a critical review

Calcium phosphates are promising materials for applications in bone repair and substitution, particularly for their bioactivity and ability to form self-setting cements. Among them, α-tricalcium phosphate (α-TCP) stands out due to its high solubility, its hydration reaction and bioresorbability. The synthesis of α-TCP is particularly complex and the interactions between some of the synthesis parameters are still not completely understood. The variety of methods available to synthesize α-TCP has provided a substantial variance in the properties of α-TCP-based cements and the decision about which method, parameters and starting reagents will be used for the powder's synthesis is determinant of the properties of the resulting material. Therefore, this review paper focuses on α-TCP's synthesis and properties, presenting the synthesis methods currently in use as well as a discussion of how the synthesis parameters and the cement preparation affect the reactivity and mechanical properties of the material, providing a guide for the selection of the most suitable process for each α-TCP application. STATEMENT OF SIGNIFICANCE: α-TCP is a calcium phosphate and it is currently one of the most investigated bioceramics for applications that explore its bioresorbability and the hydration reaction of α-TCP-based cements. Despite the increasing number of publications on the topic, there are still aspects not well understood. This review article aims at contributing to this fascinating subject by offering an update on the state of the art of α-TCP's synthesis methods, while also addressing topics that are not often discussed about this material, such as the preparation of α-TCP-based cements and how its parameters affect the properties of the resulting cements.

A Novel Calcium Phosphate-Based Nanocomposite for Augmentation of Cortical Bone Trajectory Screw Fixation

Purpose

To evaluate the effect of cement augmentation of cortical bone trajectory (CBT) screws using a novel calcium phosphate–based nanocomposite (CPN).

Material and Methods

CBT screws were placed into cadaveric lumbar vertebrae. Depending on the material used for augmentation, they were divided into the following three groups: CPN, polymethylmethacrylate (PMMA), and control. Radiological imaging was used to evaluate the cement dispersion. Biomechanical tests were conducted to measure the stability of CBT screws. A rat cranial defect model was used to evaluate biodegradation and osseointegration of the CPN.

Results

After cement augmentation, the CPN tended to disperse into the distal part of the screws, whereas PMMA remained limited to the proximal part of the screws (P < 0.05). As for cement morphology, the CPN tended to form a concentrated mass, whereas PMMA arranged itself as a scattered cement cloud, but the difference was not significant (P > 0.05). The axial pullout test showed that the average maximal pullout force (Fmax) of CPN-augmented CBT screws was similar to that of the PMMA group (CPN, 1639.56 ± 358.21 N vs PMMA, 1778.45 ± 399.83 N; P = 0.745) and was significantly greater than that of the control group (1019.01 ± 371.98 N; P < 0.05). The average torque value in the CPN group was higher than that in the control group (CPN, 1.51 ± 0.78 N∙m vs control, 0.97 ± 0.58 N∙m) and lower than that in the PMMA group (1.93 ± 0.81 N∙m), but there were no statistically significant differences (P > 0.05). The CPN could be biodegraded and gradually replaced by newly formed bone tissue after 12 weeks in a rat cranial defect model.

Conclusion

The biocompatible CPN could be a valuable augmentation material to enhance CBT screw stability.

Role of nanostructured materials in hard tissue engineering

The rise in the use of biomaterials in bone regeneration in the last decade has exponentially multiplied the number of publications, methods, and approaches to improve and optimize their functionalities and applications. In particular, biomimetic strategies based on the self-assembly of molecules to design, create and characterize nanostructured materials have played a very relevant role. We address this idea on four different but related points: self-setting bone cements based on calcium phosphate, as stable tissue support and regeneration induction; metallic prosthesis coatings for cell adhesion optimization and prevention of inflammatory response exacerbation; bio-adhesive hybrid materials as multiple drug delivery localized platforms and finally bio-inks. The effect of the physical, chemical, and biological properties of the newest biomedical devices on their bone tissue regenerative capacity are summarized, described, and analyzed in detail. The roles of experimental conditions, characterization methods and synthesis routes are emphasized. Finally, the future opportunities and challenges of nanostructured biomaterials with their advantages and shortcomings are proposed in order to forecast the future directions of this field of research.

The advances in nanomedicine for bone and cartilage repair

With the gradual demographic shift toward an aging and obese society, an increasing number of patients are suffering from bone and cartilage injuries. However, conventional therapies are hindered by the defects of materials, failing to adequately stimulate the necessary cellular response to promote sufficient cartilage regeneration, bone remodeling and osseointegration. In recent years, the rapid development of nanomedicine has initiated a revolution in orthopedics, especially in tissue engineering and regenerative medicine, due to their capacity to effectively stimulate cellular responses on a nanoscale with enhanced drug loading efficiency, targeted capability, increased mechanical properties and improved uptake rate, resulting in an improved therapeutic effect. Therefore, a comprehensive review of advancements in nanomedicine for bone and cartilage diseases is timely and beneficial. This review firstly summarized the wide range of existing nanotechnology applications in the medical field. The progressive development of nano delivery systems in nanomedicine, including nanoparticles and biomimetic techniques, which are lacking in the current literature, is further described. More importantly, we also highlighted the research advancements of nanomedicine in bone and cartilage repair using the latest preclinical and clinical examples, and further discussed the research directions of nano-therapies in future clinical practice.

Biomaterial Properties Modulating Bone Regeneration

Biomaterial scaffolds have been gaining momentum in the past several decades for their potential applications in the area of tissue engineering. They function as three-dimensional porous constructs to temporarily support the attachment of cells, subsequently influencing cell behaviors such as proliferation and differentiation to repair or regenerate defective tissues. In addition, scaffolds can also serve as delivery vehicles to achieve sustained release of encapsulated growth factors or therapeutic agents to further modulate the regeneration process. Given the limitations of current bone grafts used clinically in bone repair, alternatives such as biomaterial scaffolds have emerged as potential bone graft substitutes. This review summarizes how physicochemical properties of biomaterial scaffolds can influence cell behavior and its downstream effect, particularly in its application to bone regeneration.

Corrosion Protection of Nano-biphasic Calcium Phosphate Coating on Titanium Substrate

Background:

Increasing the bioactivity of metallic implants is necessary for biomaterial applications where hydroxyapatite (HA) is used as a surface coating. In industry, HA is currently coated by plasma spraying, but this technique has a high cost and produces coating with short-term stability.

Objectives:

In the present study, electrophoretic deposition (EPD) was used to deposit nano-biphasic calcium phosphate compound (β-tri-calcium phosphate (β-TCP) /hydroxyapatite (HA)) bio-ceramics on the titanium surface. The microstructural, chemical compositions and bioactivity of the β- TCP/HA coatings were studied in a simulated body fluid solution (SBF).

Methods:

Scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) were used. Additionally, the antibacterial effect was studied by the agar diffusion method. The corrosion behavior of the β-TCP/HA coating on titanium surface (Ti) in the SBF solution at 37oC was investigated by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests.

Results:

The Ti surface modification increased its biocompatibility and corrosion resistance in the simulated body fluid. The antibacterial inhibition activity of the β-TCP/HA bio-ceramic was enhanced by electroless silver deposition. The enhanced properties could be attributed to the use of nano-sized biphasic calcium phosphates in a low-temperature EPD process.

Conclusions:

The β-TCP/HA and β-TCP/HA/Ag coatings well protect Ti from the corrosion in SBF and endow Ti with biocompatibility. The β-4-TCP/HA/Ag/Ti substrate shows good antibacterial activity.

Incorporation of chitosan/graphene oxide nanocomposite in to the PMMA bone cement: Physical, mechanical and biological evaluation

One of the most popular types of bone cements is polymethylmethacrylate (PMMA). The properties of this bone cement have attracted many researchers effort to modify its properties. In this study, after preparation of chitosan (Cs) powder and Cs/graphene oxide (GO) nanocomposite powder, they were added homogeneously to the PMMA bone cement with different percentages. The results showed that the addition of 25 wt% of Cs/GO nanocomposite powder to the PMMA bone cement cause to increase the compressive strength by 16.2%, the compressive modulus by 69.1% and the bending strength by 24.0%. The obtained results showed that by adding Cs/GO nanocomposite powder to the PMMA bone cement, setting time and injectability were increased, maximum temperature was decreased and apatite-like deposition was increased after 4 weeks of incubation in SBF solution. The results of MG-63 cell culture confirmed the improvement of cell viability, growth and cell adhesion for 25 wt% PMMA-Cs/GO composite bone cement. Therefore, it can be concluded that 25 wt% PMMA-Cs/GO composite bone cement with improved mechanical, physical and biological properties can be a good replacement for common commercial bone cements in orthopedic applications.

Recent advances and future perspectives of sol–gel derived porous bioactive glasses: a review

Sol–gel derived bioactive glasses have been extensively explored as a promising and highly porous scaffold materials for bone tissue regeneration applications owing to their exceptional osteoconductivity, osteostimulation and degradation rates.

Biphasic Injectable Bone Cement with Fe3O4/GO Nanocomposites for the Minimally Invasive Treatment of Tumor-Induced Bone Destruction

Minimally invasive surgery will be gradually applied to the surgical treatment of bone tumors. One of the difficulties in the minimally invasive treatment of bone tumors is the lack of injectable materials that can be used to treat tumor-induced bone defects. Therefore, it is imperative to develop an injectable bone filler that can not only be injected into the defect site by minimally invasive methods to provide strong support and repair bone tissue but also inactivate residual tumor cells around the defect. To achieve this aim, in our study, for the first time, we doped Fe₃O₄/graphene oxide (GO) nanocomposites into α-tricalcium phosphate (α-TCP)/calcium sulfate (CS) biphasic bone cement to prepare an injectable magnetic bone cement (α-TCP/CS/Fe₃O₄/GO, αCFG), which can be applied in bone tumor minimally invasive surgery and fit ideally even if the area is irregular. The magnetothermal performance of the αCFG bone cement could be well adjusted by altering the content of Fe₃O₄/GO nanocomposites and the magnetic field parameters, but a 10 wt % Fe₃O₄/GO content formed the most stable bone cement with excellent magnetothermal performance. The αCFG bone cement not only promotes bone regeneration but also exhibits enhanced tumor treatment effects. Such multifunctional bone cement could provide a promising clinical strategy for the minimally invasive treatment of tumor-induced bone destruction.

Zinc doping induced differences in the surface composition, surface morphology and osteogenesis performance of the calcium phosphate cement hydration products

In order to investigate the influence of Zn on the hydration reaction of calcium phosphate cement (CPC), the incompletely hydrated CPC tablets were kept soaking in varying zinc-containing tris-(hydroxymethyl)-aminomethane/hydrochloric acid (Zn-Tris-HCl) buffers. It was found that Zn could retard the CPC hydration, the inhibitory effect was in direct proportional to the Zn content in the Zn-Tris-HCl buffer, and overhigh concentration of Zn (≧800 μM) caused the CPC hydration products having different phase composition and surface morphology. Cell culture experimental results revealed the CPC tablets which were soaked in the Zn-Tris-HCl buffer containing relative low Zn content (≦320 μM) favored the mouse bone mesenchymal stem cells (mBMSCs) spreading. When Zn-doped CPC tablets released 10.91 to 27.15 μM of zinc ions into the cell culture medium, it greatly contributed to the improvement of the proliferation ability and the alkaline phosphatase (ALP) activity of the mBMSCs. In the same case, the expression of osteogenesis related genes such as collagen I and runt-related transcription factor 2 was remarkably up-regulated as well. However, the release of high concentration of Zn (128.58 μM) would significantly reduce the ALP activity of the mBMSCs. Therefore, Zn not only facilitates osteogenesis but also affects the CPC hydration behavior, and the CPC with suitable Zn dosage concentration has great potentials to be used for clinical bone repairing.

Preparation of a novel bone wax with modified tricalcium silicate cement and BGs

Amino-grafted and vaterite-contained tricalcium silicate cement (A-V-C₃S) was composited with 58S bioglass/chitosan/carboxy methyl cellulose (BG/CS/CMC, referred as BGs) to surmount the non-absorbability and infection problems of traditional bone wax. Its material, bioactive, biocompatible and antibacterial properties were systematically characterized. The results revealed that A-V-C₃S/BGs possessed self-setting, injectable, mechanical and degradable abilities. A-V-C₃S/BGs (1:1 g/g) was optimum owing to its higher compressive strength (9.91 MPa) and lower pH value (7.6 to 8.1) in the test groups. In vitro immersion experiment demonstrated that A-V-C₃S/BGs had good hydroxyapatite formation ability, and its excellent cell adhesion, low cytotoxicity and superior cell proliferation were verified by mouse embryonic osteoblast precursor cells in cell tests. Compared with A-V-C₃S, antibacterial experiment illustrated the significantly enhanced antibacterial property of A-V-C₃S/BGs to Staphylococcus aureus and Escherichia coli.

Hemocompatible and Bioactive Heparin-Loaded PCL-α-TCP Fibrous Membranes for Bone Tissue Engineering

The combination of bioactive components such as calcium phosphates and fibrous structures are encouraging niche-mimetic keys for restoring bone defects. However, the importance of hemocompatibility of the membranes is widely ignored. Heparin-loaded nanocomposite poly(ε-caprolactone) (PCL)-α-tricalcium phosphate (α-TCP) fibrous membranes are developed to provide bioactive and hemocompatible constructs for bone tissue engineering. Nanocomposite membranes are optimized based on bioactivity, mechanical properties, and cell interaction. Consequently, various concentrations of heparin molecules are loaded within nanocomposite fibrous membranes. In vitro heparin release profiles reveal a sustained release of heparin over the period of 14 days without an initial burst. Moreover, heparin encapsulation enhances mesenchymal stem cell (MSC) attachment and proliferation, depending on the heparin content. It is concluded that the incorporation of heparin within TCP-PCL fibrous membranes provides the most effective cellular interactions through synergistic physical and chemical cues.