Effect of citric acid on setting reaction and tissue response to β -TCP granular cement

A novel two-step conversion from DCPD-coated β-TCP to low crystallinity β-TCP porous scaffolds via combination between dry heating and hydrothermal methods: Effects on pre-osteoblast cell responses

This study presents a novel two-step process to fabricate low crystallinity (LC) β-tricalcium phosphate (β-TCP) porous scaffolds and evaluates their implications for pre-osteoblast cell responses. The novelty of this study lies in the two-step conversion of dicalcium phosphate dihydrate (DCPD) -coated β-TCP porous scaffold into LC β-TCP porous scaffolds through a combination of dry heating and hydrothermal conditions at 200°C. The obtained LC β-TCP porous scaffolds were characterised using a Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), porosity, and compressive strength analysis confirmed the successful fabrication of LC β-TCP scaffolds. Besides, in vitro tests using pre-osteoblast MC3T3-E1 cells were conducted to investigate the cell responses toward LC β-TCP porous scaffolds. The results revealed that the LC β-TCP porous scaffolds were successfully fabricated by converting the DCPD-coated β-TCP into the dicalcium phosphate anhydrous (DCPA) coated β-TCP, followed by a hydrothermal process in a 0.1 mol/L calcium chloride (CaCl2) aqueous solution at 200°C for 24 hours to obtain LC of pure β-TCP scaffold. Moreover, in vitro cell study indicated that the cell density and proliferation surrounding the surface of the LC β-TCP porous scaffold were greater than DCPD-coated β-TCP porous scaffolds. The findings from this study are expected to significantly impact bioceramic technology by enhancing cell responses.

A new injectable quick hardening anti-collapse bone cement allows for improving biodegradation and bone repair

The development of injectable cement-like biomaterials via a minimally invasive approach has always attracted considerable clinical interest for modern bone regeneration and repair. Although α-tricalcium phosphate (α-TCP) powders may readily react with water to form hydraulic calcium-deficient hydroxyapatite (CDHA) cement, its long setting time, poor anti-collapse properties, and low biodegradability are suboptimal for a variety of clinical applications. This study aimed to develop new injectable α-TCP-based bone cements via strontium doping, α-calcium sulfate hemihydrate (CSH) addition and liquid phase optimization. A combination of citric acid and chitosan was identified to facilitate the injectable and anti-washout properties, enabling higher resistance to structure collapse. Furthermore, CSH addition (5 %-15 %) was favorable for shortening the setting time (5-20 min) and maintaining the compressive strength (10-14 MPa) during incubation in an aqueous buffer medium. These α-TCP-based composites could also accelerate the biodegradation rate and new bone regeneration in rabbit lateral femoral bone defect models in vivo. Our studies demonstrate that foreign ion doping, secondary phase addition and liquid medium optimization could synergistically improve the physicochemical properties and biological performance of α-TCP-based bone cements, which will be promising biomaterials for repairing bone defects in situations of trauma and diseased bone.

Influence of pH and ion components in the liquid phase on the setting reaction of carbonate apatite granules

Carbonate apatite (CO₃Ap) is an inorganic component of bone and replaces by natural bone after implantation into the bone defect. Because of this unique characteristic, CO₃Ap granules have been used in the dental field. However, washing out of granules from the bone defect area is an issue. The aim of this study was to set CO₃Ap granules by mixing CO₃Ap granules with acidic phosphate solutions and evaluate the influence of the pH and ion components of the solutions. When Na⁺ was the counter ion, the amount of precipitated dicalcium phosphate dihydrate (DCPD) was small and the setting ability disappeared with increasing pH of the solutions. Alternatively, when the counter ion was Ca²⁺, the amount of precipitated DCPD was high and the setting ability was observed even at high pH. These results suggest the presence of Ca²⁺ in the acidic phosphate solution is a key for fabricating CO₃Ap granular cement.

Unravelling the Effect of Citrate on the Features and Biocompatibility of Magnesium Phosphate-Based Bone Cements

In the framework of new materials for orthopedic applications, Magnesium Phosphate-based Cements (MPCs) are currently the focus of active research in biomedicine, given their promising features; in this field, the loading of MPCs with active molecules to be released in the proximity of newly forming bone could represent an innovative approach to enhance the in vivo performances of the biomaterial. In this work, we describe the preparation and characterization of MPCs containing citrate, an ion naturally present in bone which presents beneficial effects when released in the proximity of newly forming bone tissue. The cements were characterized in terms of handling properties, setting time, mechanical properties, crystallinity, and microstructure, so as to unravel the effect of citrate concentration on the features of the material. Upon incubation in aqueous media, we demonstrated that citrate could be successfully released from the cements, while contributing to the alkalinization of the surroundings. The cytotoxicity of the materials toward human fibroblasts was also tested, revealing the importance of a fine modulation of released citrate to guarantee the biocompatibility of the material.

Effects of acidic calcium phosphate concentration on setting reaction and tissue response to β-tricalcium phosphate granular cement

Beta-tricalcium phosphate granular cement (β-TCP GC), consisting of β-TCP granules and an acidic calcium phosphate (Ca-P) solution, shows promise in the reconstruction of bone defects as it sets to form interconnected porous structures, that is, β-TCP granules are bridged with dicalcium phosphate dihydrate (DCPD) crystals. In this study, the effects of acidic Ca-P solution concentration (0-600 mmol/L) on the setting reaction and tissue response to β-TCP GC were investigated. The β-TCP GC set upon mixing with its liquid phase, based on the formation of DCPD crystals, which bridged β-TCP granules to one another. Diametral tensile strength of the set β-TCP GC was relatively the same, at ∼0.6 MPa, when the Ca-P concentration was 20-600 mmol/L. Due to the setting ability, reconstruction of the rat's calvarial bone defect using β-TCP GC with 20, 200, and 600 mmol/L Ca-P solution was much easier compared to that with β-TCP granules without setting ability. Four weeks after the reconstruction, the amount of new bone was the same, ∼17% in both β-TCP GC and β-TCP granules groups. Cellular response to β-TCP granules and β-TCP GC using the 20 mmol/L acidic Ca-P solution was almost the same. However, β-TCP GC using the 200 and 600 mmol/L acidic Ca-P solution showed a more severe inflammatory reaction. It is concluded, therefore, that β-TCP GC, using the 20 mmol/L acidic Ca-P solution, is recommended as this concentration allows surgical techniques to be performed easily and provides good mechanical strength, and the similar cellular response to β-TCP granules. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:22-29, 2020.

Fabrication of self-setting β-TCP granular cement using β-TCP granules and sodium hydrogen sulfate solution

Bridging beta-tricalcium phosphate (β-TCP) granules with dicalcium phosphate dihydrate (DCPD) creates a porous, interconnected β-TCP granular cement (GC) that is useful for reconstructing bone defects: the interconnected pores can accelerate new bone ingrowth and the set cement prevents the loss of granules from the bone defect area. However, the setting time of β-TCP GC in an acidic calcium phosphate solution is too short (<1 min) for handling in clinical applications, such as in orthopedic surgery. To address this issue, we sought to optimize the setting time of β-TCP GC using β-TCP granules and NaHSO₄ solution, as [Formula: see text] is a known inhibitor of DCPD formation. Both DCPD and calcium sulfate dihydrate (CSD) precipitated on the surface of β-TCP granules and bridged β-TCP granules to one another. Increasing NaHSO₄ concentration (from 0.5 mol/L to 5 mol/L) led to an increase in the amount of precipitant from 2.6 ± 0.2% to 21.6 ± 1.3% for DCPD and 1.3 ± 0.3% to 10.1 ± 0.5% for CSD. The diametral tensile strength was also increased from 0.03 ± 0.01 MPa to 2.0 ± 0.1 MPa with increasing NaHSO₄ concentration. When 2 mol/L NaHSO₄ solution was used as the liquid phase, setting time became 5.3 ± 0.2 min, which is suitable for handling in clinical applications to repair bone defects. In conclusion, β-TCP GC using NaHSO₄ solution as the liquid phase has good potential value as bone augmentation cement.