Evaluation of colloidal silica suspension as efficient additive for improving physicochemical and in vitro biological properties of calcium sulfate-based nanocomposite bone cement

The Influence of Nanosilica on Properties of Cement Based on Tetracalcium Phosphate/Monetite Mixture with Addition of Magnesium Pyrophoshate

The effect of nanosilica on the microstructure setting process of tetracalcium phosphate/nanomonetite calcium phosphate cement mixture (CPC) with the addition of 5 wt% of magnesium pyrophosphate (assigned as CT5MP) and osteogenic differentiation of mesenchymal stem cells cultured in cement extracts were studied. A more compact microstructure was observed in CT5MP cement with 0.5 wt% addition of nanosilica (CT5MP1Si) due to the synergistic effect of Mg₂P₂O₇ particles, which strengthened the cement matrix and nanosilica, which supported gradual growth and recrystallization of HAP particles to form compact agglomerates. The addition of 0.5 wt% of nanosilica to CT5MP cement caused an increase in CS from 18 to 24 MPa while the setting time increased almost twofold. It was verified that adding nanosilica to CPC cement, even in a low amount (0.5 and 1 wt% of nanosilica), positively affected the injectability of cement pastes and differentiation of cells with upregulation of osteogenic markers in cells cultured in cement extracts. Results revealed appropriate properties of these types of cement for filling bone defects.

Preparation and characterization of injectable gelatin/alginate/chondroitin sulfate/α-calcium sulfate hemihydrate composite paste for bone repair application

In this study, a group of injectable composite pastes with a novel formulation consisting of two inorganic components: α-calcium sulfate hemihydrate (α-CSH, P/L = 1.8-2.1 g/ml) and calcium-deficient hydroxyapatite (CDHA, P/L = 0.1 g/ml) nanoparticles; and three biopolymers: gelatin (2, 4 wt. %), alginate (1, 1.5 wt. %), and chondroitin sulfate (0.5 wt. %) were carefully prepared and thoroughly characterized with commensurate characterizations. The composite sample composed of gelatin (2 wt. %), alginate (1.5 wt. %), chondroitin sulfate (0.5 wt. %), and also CDHA nanoparticles and α-CSH with P/L ratios of 0.1 and 2.1 g/ml, respectively, exhibited optimal properties in terms of injectability, anti-washout performance, and rheological characteristics. After 14 days of immersion of the chosen sample in the simulated body fluid medium, a dense layer of apatite was formed on the surface of the composite paste. The cellular in vitro tests, such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT), alkaline phosphatase assay, 4',6-diamidino-2-phenylindole staining, and cellular attachment, revealed the desirable response of MG-63 cells to the composite paste. The chondroitin sulfate significantly improved the injectability, anti-washout performance, and cellular response of the samples. Considering the promising features of the composite paste prepared in this research work, it could be considered as an alternative injectable bioactive material for bone repair applications.[Formula: see text].

Biphasic ceramic bone graft with biphasic degradation rates

In this study, the characteristics of a novel biphasic bone graft are reported. The bone graft is a physical mixture of calcium sulfate (CS) and hydroxyapatite (HA). This biphasic bone graft was prepared by sintering at 1100 °C. Since the degradation rate of CS is much faster than that of HA, the CS/HA biphasic bone graft exhibits two degradation rates. The degradation rate is rapid (~10 wt%/week) in the first stage and then slow (~1 wt%/week) in the second stage. The biphasic bone graft has been implanted into the distal femur of rat. Most the bone graft was degraded 13 weeks postoperatively. Instead, trabecular bone and vascular tissue are observed at the location of implant. The bone graft is unique for its burst of calcium ions at the start and its ability to remain stable throughout the degradation process. Its stable porous structure serves as an ideal scaffold for the formation of new bone as well as vascularization.

Fabrication of ultrahigh-molecular-weight polyethylene porous implant for bone application

Porous implants play a crucial role in allowing ingrowth of host connective tissue and thereby help in keeping the implant in its place. With the aim of mimicking the microstructure of natural extracellular matrix, ultrahigh-molecular-weight polyethylene (UHMWPE) porous samples with a desirable pore size distribution were developed by combining thermally induced phase separation and salt leaching techniques. The porous UHMWPE samples consisted of a nanofibrous UHMWPE matrix with a fibre diameter smaller than 500 nm, highly interconnected, with a controllable pore diameter from nanoscale to 300 µm. Moreover, a porous UHMWPE sample was also developed as a continuous and homogeneous coating onto the UHMWPE dense sample. The dense/porous UHMWPE sample supported human foetal osteoblast 1.19 cell line proliferation and differentiation, indicating the potential of porous UHMWPE with a desirable pore size distribution for bone application. An osseointegration model in the sheep revealed substantial bone formation within the pore layer at 12 weeks via SEM evaluation. Ingrown bone was more closely opposed to the pore wall when compared to the dense UHMWPE control. These results indicate that dense/porous UHMWPE could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic application.

Smart Injectable Self-Setting Monetite Based Bioceramics for Orthopedic Applications

The present study is the first of its kind dealing with the development of a specific bioceramic which qualifies as a potential material in hard-tissue replacements. Specifically, we report the synthesis and evaluation of smart injectable calcium phosphate bone cement (CPC) which we believe will be suitable for various kinds of orthopedic and spinal-fusion applications. The smart nature of this next generation orthopedic implant is attained by incorporating piezoelectric barium titanate (BT) particles into monetite-based (dicalcium phosphate anhydrous, DCPA) CPC composition. The main goal is to take advantage of the piezoelectric properties of BT, as electromechanical effect plays a vital role in fracture healing at the defect site and bone integration with the implant. Furthermore, radiopacity of BT would help in easy detection of the CPC presence at the fracture site during surgery. Results reveal that BT addition favors important properties of bone cement such as good compressive strength, injectability, bioactivity, biocompatibility, and even washout resistance. Most importantly, the self-setting nature of the bone cements are not compromised with BT incorporation. The in vitro results confirm that the developed bone-cement abides by the standard orthopedic requirements making it apt for real-time prosthetic materials.

Enhanced Stability of Calcium Sulfate Scaffolds with 45S5 Bioglass for Bone Repair

Calcium sulfate (CaSO₄), as a promising tissue repair material, has been applied widely due to its outstanding bioabsorbability and osteoconduction. However, fast disintegration, insufficient mechanical strength and poor bioactivity have limited its further application. In the study, CaSO₄ scaffolds fabricated by using selective laser sintering were improved by adding 45S5 bioglass. The 45S5 bioglass enhanced stability significantly due to the bond effect of glassy phase between the CaSO₄ grains. After immersing for four days in simulated body fluid (SBF), the specimens with 45S5 bioglass could still retain its original shape compared as opposed to specimens without 45S5 bioglass who experienced disintegration. Meanwhile, its compressive strength and fracture toughness increased by 80% and 37%, respectively. Furthermore, the apatite layer was formed on the CaSO₄ scaffolds with 45S5 bioglass in SBF, indicating good bioactivity of the scaffolds. In addition, the scaffolds showed good ability to support the osteoblast-like cell adhesion and proliferation.

Development of nanosilica bonded monetite cement from egg shells

This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5±1 min. The compressive strength after 24h of incubation was approximately 8.45±1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10±1 min) process by about 2.5 min and improve compressive strength (20.16±4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics.

Development of monetite-nanosilica bone cement: a preliminary study

In this paper, we reported the results of our efforts in developing DCPA/nanosilica composite orthopedic cement. It is motivated by the significances of DCPA and silicon in bone physiological activities. More specifically, this paper examined the effects of various experimental parameters on the properties of such composite cements. In this work, DCPA cement powders were synthesized using a microwave synthesis technique. Mixing colloidal nanosilica directly with synthesized DCPA cement powders can significantly reduce the washout resistance of DCPA cement. In contrast, a DCPA-nanosilica cement powder prepared by reacting Ca(OH)2 , H3 PO4 and nanosilica together showed good washout resistance. The incorporation of nanosilica in DCPA can improve compressive strength, accelerate cement solidification, and intensify surface bioactivity. In addition, it was observed that by controlling the content of NaHCO3 during cement preparation, the resulting composite cement properties could be modified. Allowing for the development of different setting times, mechanical performance and crystal features. It is suggested that DCPA-nanosilica composite cement can be a potential candidate for bone healing applications.