Preparation and Reinforcement Adaptability of Jute Fiber Reinforced Magnesium Phosphate Cement Based Composite Materials

To improve the brittleness characteristics of magnesium phosphate cement-based materials(MPC)and to promote its promotion and application in the field of structural reinforcement and repair,this study aimed to increase the toughness of MPC by adding jute fiber,explore the effects of different amounts of jute fiber on the working and mechanical properties of MPC,and prepare jute fiber reinforced magnesium phosphate cement-based materials(JFRMPC)to reinforce damaged beams.The improvement effect of beam performance before and after reinforcement was compared,and the strengthening and toughening mechanisms of jute fiber on MPC were explored through microscopic analysis.The experimental results show that,as the content of jute fiber(JF)increases,the fluidity and setting time of MPC decrease continuously;When the content of jute fiber is 0.8%,the compressive strength,flexural strength,and bonding strength of MPC at 28 days reach their maximum values,which are increased by 18.0%,20.5%,and 22.6%compared to those of M0,respectively.The beam strengthened with JFRMPC can withstand greater deformation,with a deflection of 2.3 times that of the unreinforced beam at failure.The strain of the steel bar is greatly reduced,and the initial crack and failure loads of the reinforced beam are increased by 192.1%and 16.1%,respectively,compared to those of the unreinforced beam.The JF added to the MPC matrix dissipates energy through tensile fracture and debonding pull-out,slowing down stress concentration and inhibiting the free development of cracks in the matrix,enabling JFRMPC to exhibit higher strength and better toughness.The JF does not cause the hydration of MPC to generate new compounds but reduces the amount of hydration products generated.

Effect of Borax on Hydration and Hardening Properties of Magnesium and Pottassium Phosphate Cement Pastes

Magnesium and potassium phosphate cement （MKPC） sample were prepared by mixing dead burnt MgO powder, potassium phosphate and different dosages of retarder borax to investigate the effect of borax on its hydration and hardening characteristics. The pH value, fluidity, hydration temperature and strength development of MKPC paste were investigated, and the mineralogical composition and microstructural morphology of its hydration products were analyzed. The experimental results indicated that, within a certain dosage, borax caused an endothermal effect for MKPC paste, which decreased the early hydration rate of MKPC paste, increased the fluidity of MKPC paste. Thus, strength and micro-morphology of hardened MKPC are affected. It can be concluded that borax in MKPC paste retards the early hydration rate of MKPC paste by forming a film onto surface of MgO, decreasing the temperature and increasing the pH value of the system. As borax dosage varying, different factors may dorminate the effects.

Calcium phosphate cements for bone engineering and their biological properties

Calcium phosphate cements （CPCs） are frequently used to repair bone defects. Since their discovery in the 1980s, extensive research has been conducted to improve their properties, and emerging evidence supports their increased application in bone tissue engineering. Much effort has been made to enhance the biological performance of CPCs, including their biocompatibility, osteoconductivity, osteoinductivity, biodegradability, bioactivity, and interactions with cells. This review article focuses on the major recent developments in CPCs, including 3D printing, injectability, stem cell delivery, growth factor and drug delivery, and pre- vascularization of CPC scaffolds via co-culture and tri-culture techniques to enhance angiogenesis and osteogenesis.

REINFORCEMENT OF CALCIUM PHOSPHATE CEMENTS WITH PHOSPHORYLATED CHITIN

Phosphorylated chitins (P-chitins) as the additives of calcium phosphate cements (CPCs) were prepared by the phosphorylation of chitin with phosphorus pentoxide in methanesulfonic acid. Their physical properties and effects on CPCs from monocalcium phosphate monohydrate (MCPM) and calcium oxide (CaO) or dicalcium phosphate dihydrate (DCPD) and calcium hydroxide [Ca(OH)(2)] were investigated. Addition of P-chitin (M-w = 2.60 x 10(4); degree of substitution, DS = 0.68) to the liquid phase in amounts up to 3 wt.% for MCPM and CaO cements or 1.5 wt.% for DCPD and Ca(OH)(2) cements could enhance the mechanical strength considerably, while little influence on the setting time was observed. However, further addition of P-chitin will cause no setting.

Effect of raw materials and proportion on mechanical properties of magnesium phosphate cement

Magnesium phosphate cement (MPC) cementitious material is a phosphate cement-based material with strengthformed by a serious of acid-base neutralization reactions among magnesium oxide, phosphate retarder and water,which has a high early strength and a broad application prospect in the field of pavement rehabilitation. Thisreview collects and organizes the latest progress in the field of research on the influencing factors of mechanicalproperties of magnesium phosphate cementitious materials worldwide in recent years, and discusses the possibilitiesof application in airport engineering.The type of phosphate has a great influence on the reaction products, and the strength of the reaction productsof ammonium salt is higher. Borax is the most commonly used retarder, and the retarding effect is related to theratio of boron to magnesium. However, borax retarders have an adverse effect on the strength of MPC. In terms ofthe influence of mineral admixtures on the properties of MPC, fly ash, silica fume and metakaolin, as commonmineral admixtures, have a positive influence on the mechanical properties of MPC, but the mechanism anddegree of the influence of the three materials on the strength of MPC are slightly different;Aggregates can alsoimprove the volume stability and mechanical properties of MPC by forming skeleton structure and slowing downthe exothermic reaction. In fiber reinforced MPC matrix, steel fiber is the most widely used and the bondingperformance between special-shaped steel fiber and MPC matrix is higher than that of straight fiber;basalt fiberhas also been proved to be used to improve the mechanical properties of MPC system.

The In-situ Reinforcement of Calcium Phosphate Cement and Its Micro-structural Analysis

Carbon nanotubes （ CNTs ） and polyacrylic acid were employed to modify the setting process and hydration products of β-TCP/TTCP calcium phosphate cement. The micro-structure of hydration product and the fashion of how additives and hydration particles interconnected were investigated. With the modification effect of CNTs , the setting particles and CNTs got winded and interconnected and thus made the composite more compact and denser.

The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

In this study, calcium phosphate cements （CPC） were prepared by mixing cement powders of tetracalcium phosphate （TTCP） with a cement liquid of phosphate acid saline solution. Tetracycline （TTC）-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry （FT-IR） no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1 seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

Microstructure and Mechanical Properties of Calcium Phosphate Cement/Gelatine Composite Scaffold with Oriented Pore Structure for Bone Tissue Engineering

The macroporous calcium phosphate（CPC） cement with oriented pore structure was prepared by freeze casting. SEM observation showed that the macropores in the porous calcium phosphate cement were interconnected aligned along the ice growth direction. The porosity of the as-prepared porous CPC was measured to be 87.6% by Archimede＇s principle. XRD patterns of specimens showed that poorly crystallized hydroxyapatite was the main phase present in the hydrated porous calcium phosphate cement. To improve the mechanical properties of the CPC scaffold, the 15% gelatine solution was infiltrated into the pores under vacuum and then the samples were freeze dried to form the CPC/gelatine composite scaffolds. After reinforced with gelatine, the compressive strength of CPC/gelatine composite increased to 5.12 MPa, around fifty times greater than that of the unreinforced macroporous CPC scaffold, which was only 0.1 MPa. And the toughness of the scaffold has been greatly improved via the gelatine reinforcement with a much greater fracture strain. SEM examination of the specimens indicated good bonding between the cement and gelatine. Participating the external load by the deformable gelatine, patching the defects of the CPC pores wall, and crack deflection were supposed to be the reinforcement mechanisms. In conclusion, the calcium phosphate cement/gelatine composite with oriented rmre structure nrenared in this work might be a potential scaffold for bone tissue engineerinm

Evaluation of Calcium Phosphate Cement As a Root Canal Sealer Filling Material

Calcium phosphate cement for root end sealing was obtained by in mixing alpha-tricalcium phosphate and additives with an aqueous solation of citric. Powder and liquid were mixed at a ratio of 1.25g/mL. The biocompatibility of this material was investigated primarily by subcutaneous implantation tests. Then calcium phosphate cement was used to fill three adult dogs' root canal, both calcium hydroxide paste and hydroxyapatite paste as control. The animals were killed at 4, 12, 20 weeks postoperatively respectively. The effects of different materials on the apical closure, restoration of periapical tissues and adaptability to the dentinal surface were examined by optical and electronic microscope. The observation at 20 weeks shows that the calcium phosphate cement has the potentialities of being a root canal sealer filling material available for pulpless teeth with open-apex and destructive periapical tissue.

Preparation of a Novel Calcium Phosphate Cement Using N-methylene Phosphonic Chitosan as a Gelling Agent

A modified chitosan （ N-methylene phosphonic Chitosan, NMPC） was synthesized to improve solubility and ability to bind calcium ion. The properties of the raw material chitosan and its derivative NMPC were characterised using FTIR , ^1H- NMR . The aim of this study was to enhance the compressive CPC by reinforcing with NMPC. A formulation consisting of CPC powder , buffer solution and gelling agent was used for preparation of the CPC. CPC powder coasisted of tetracalcium phosphate（ TTCP ） and dicalcium phosphate anhydrous （ DCPA ）. NMPC which acted as the gelling ageut was dissohed into KH2PO4-Na2 HPO4 buffer solution. Each specimen in the mold was sandciched between two fritted glass sides and kept for 24 hours. Compressive strengths were determined, the setting product was identified using X-ray diffraction and scanning electron microscopy was used to investigate the hydroxyapatite particles size and porosity. The experimental results showed that the dominating influence on the compressive strengths of CPC-AMPC was the HA panicle size, its uniformity and appropriate porosity.

Influence of Water Stability on Bond Performance Between Magnesium Phosphate Cement Mortar and Steel Fibre

The fibre pullout test was conducted to investigate the influence of the water stability on the bond behaviour between the Magnesium phosphate cement(MPC)matrix and the steel fibre.The composition of the MPC-matrix and the immersion age of the specimens are experimentally investigated.The average bond strength and the pullout energy are investigated by analysing the experimental results.In addition,the microscopic characteristics of the interface transition zone are investigated using scanning electron microscopy(SEM).The experimental results showed that the bond performance between the MPC-matrix and the steel fibre decreased significantly with the increase of the duration of immersion in water.The average bond strength between the steel fibre and the MPC-matrix reduced by more than 50%when the specimens were immersed in the water for 28 days.The effect of the water on the interface between the steel fibre and the MPC-matrix was found to be more significant compared to the composition of the MPC-matrix.In addition,the MgO-KH2PO4 mole ratio of the MPC significantly influenced the water stability of the interface zone between the steel fibre and MPC-matrix.

Effects of Calcination Temperature of Boron-Containing Magnesium Oxide Raw Materials on Properties of Magnesium Phosphate Cement as a Biomaterial

A new magnesium phosphate bone cement （MPBC） was prepared as a byproduct of boroncontaining magnesium oxide （B-MgO） after extracting Li2CO3 from salt lakes. We analyzed the elementary composition of the B-MgO raw materials and the effects of calcination temperature on the performance of MPBC. The phase composition and microstructure of the B-MgO raw materials and the hydration products （KMgPO4.6H2O） of MPBC were analyzed by X-ray diffraction and scanning electron microscopy. The results showed that ionic impurities and the levels of toxic elements were sufficiently low in B-MgO raw materials to meet the medical requirements for MgO （Chinese Pharmacopeia, 2O10 Edition） and for hydroxyapatite surgical implants （GB23101.1-2O08）. The temperature of B-MgO calcination had a marked influence on the hydration and hardening of MPBC pastes. Increasing calcination temperature prolonged the time required for the MPBC slurry to set, significantly decreased the hydration temperature, and prolonged the time required to reach the highest hydration temperature. However, the compressive strength of hardened MPBC did not increase with higher calcination temperatures. In the 900-1 000 ~C temperature range, the hardened MPBC had a higher compressive strength. Imaging analysis suggested that the setting time and the highest hydration temperature of MPBC pastes were dependent on the size and crystal morphology of the B-MgO materials. The production and microstructure compactness of KMgPOa＇6H2O, the main hydration product, determined the compressive strength.

Effect of coral sand on the mechanical properties and hydration mechanism of magnesium potassium phosphate cement mortar

Damaged structures on coral islands have been spalling and cracking due to the dual corrosion of tides and waves.To ensure easy access to aggregate materials,magnesium potassium phosphate cement(MKPC)and coral sand(CS)are mixed to repair damaged structures on coral islands.However,CS is significantly different from land-sourced sand in mineral composition,particle morphology,and strength.This has a substantial impact on the hydration characteristics and macroscopic properties of MKPC mortar.Therefore,in this study we investigated the compressive strength,interfacial mechanical properties,and corrosion resistance of MKPC CS mortar.Changes in the morphology,microstructure,and relative contents of hydration products were revealed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)and X-ray diffraction(XRD).The results indicated that the compressive strength increased linearly with the interfacial micro-hardness,and then stabilized after long-term immersion in pure water and Na2SO4 solution,showing excellent corrosion resistance.Compared with MKPC river sand(RS)mortar,the hydration products of CS mortar were an intermediate product 6KPO2·8H2O with a relative content of 3.9%at 1 h and 4.1%at 12 h.The hydration product MgKPO_(4)·6H_(2)O increased rapidly after 7-d curing,with an increased growth rate of 1100%.Our results showed that CS promoted the nucleation and formation of hydration products of MKPC,resulting in better crystallinity,tighter overlapping,and a denser interfacial transition zone.The results of this study provide technical support for applying MKPC mortar as a rapid repair material for damaged structures on coral islands.

Treatment of critical bone defects using calcium phosphate cement and mesoporous bioactive glass providing spatiotemporal drug delivery

Calcium phosphate cements (CPC) are currently widely used bone replacement materials with excellent bioactivity, but have considerable disadvantages like slow degradation. For critical-sized defects, however, an improved degradation is essential to match the tissue regeneration, especially in younger patients who are still growing. We demonstrate that a combination of CPC with mesoporous bioactive glass (MBG) particles led to an enhanced degradation in vitro and in a critical alveolar cleft defect in rats. Additionally, to support new bone formation the MBG was functionalized with hypoxia conditioned medium (HCM) derived from rat bone marrow stromal cells. HCM-functionalized scaffolds showed an improved cell proliferation and the highest formation of new bone volume. This highly flexible material system together with the drug delivery capacity is adaptable to patient specific needs and has great potential for clinical translation.

Reconstruction of orbital defect in rabbits with composite of calcium phosphate cement and recombinant human bone morphogenetic protein-2

Background Calcium phosphate cement （CPC） is a biocompatible and osteoconductive bone substitute, and recombinant human bone morphogenetic protein-2 （rhBMP-2） has strong osteoinductibility, therefore we developed a composite bone substitute with CPC and rhBMP-2 and evaluate its reconstruction effect in rabbit orbital defect.Methods Thirty-six rabbits were randomly divided into two groups and a 5 mmx5 mmx2 mm bone defect in the infraorbital rim was induced by surgery in each orbit （72 orbits in all）. The orbital defects were treated with pure CPC or composite of CPC and rhBMP-2. The osteogenesis ability of different bone substitute was evaluated by gross observation, histological examination, histomorphometrical evaluation, compressive load-to-failure testing, and scanning electron microscope （SEM）.Results Gross observation showed that both bone substitutes were safe and effective for reconstruction of orbital defect. However, histological examination, histomorphometrical evaluation and SEM showed that CPC/rhBMP-2 group had faster speed in new bone formation and degradation of substitute material than CPC group. Compressive load-to-failure testing showed that CPC/rhBMP-2 group had stronger compressive strength than CPC group at every stage with significant difference （P ＜0.05）.Conclusion Composite of CPC/rhBMP-2 is an ideal bioactive material for repairing orbital defect, with good osteoconductibility and osteoinductibility.

Hyaluronic acid facilitates bone repair effects of calcium phosphate cement by accelerating osteogenic expression

Calcium phosphate cements(CPC)are widely anticipated to be an optimum bone repair substitute due to its satisfied biocompatibility and degradability,suitable to be used in minimally invasive treatment of bone defects.However the clinical application of CPC is still not satisfied by its poor cohesiveness and mechanical properties,in particular its osteoinductivity.Hyaluronic acid reinforced calcium phosphate cements(HA/CPC)showed extroadinary potential not only enhancing the compressive strength of the cements but also significantly increasing its osteoinductivity.In our study,the compressive strength of HA/CPC increased significantly when the cement was added 1%hyaluronic acid(denoted as 1-HA/CPC).In the meantime,hyaluronic acid obviously promoted ALP activity,osteogenic related protein and mRNA expression of hBMSCs(human bone marrow mesenchymal stem cells)in vitro,cement group of HA/CPC with 4%hyaluronic acid adding(denoted as 4-HA/CPC)showed optimal enhancement in hBMSCs differentiation.After being implanted in rat tibial defects,4-HA/CPC group exhibited better bone repair ability and bone growth promoting factors,comparing to pure CPC and 1-HA/CPC groups.The underlying biological mechanism of this stimulation for HA/CPC may be on account of higher osteogenic promoting factors secretion and osteogenic genes expression with hyaluronic acid incorporation.These results indicate that hyaluronic acid is a highly anticipated additive to improve physicochemical properties and osteoinductivity performance of CPCs for minimally invasive healing of bone defects.

In vitro and in vivo analysis of the biocompatibility of two novel and injectable calcium phosphate cements

Calcium phosphate cements(CPCs)have been widely used as bone graft substitutes for many years.The aim of this study was to evaluate the biocompatibility of two novel injectable,bioactive cements:b-tricalcium phosphate(b-TCP)/CPC and chitosan microsphere/CPC in vitro and in vivo.This was accomplished by culturing mouse pre-osteoblastic cells(MC3T3-E1)on discs and pastes of CPCs.Cell growth,adhesion,proliferation and differentiation were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and alkaline phosphatase assays as well as by scanning electron microscopy and fluorescence.The effect of CPC paste curing was also evaluated.Implantation of two materials into the muscle tissue of rabbits was also studied and evaluated by histological analysis.Cell analysis indicated good biocompatibility in vitro.The fluorescence assay suggested that the cured material discs had no obvious effect on cell growth,while the curing process did.Histological examination showed no inflammatory cell infiltration into soft tissue.These data suggest that b-TCP/CPC and chitosan microsphere/CPC composites may be promising injectable material for bone tissue engineering.

Sudoku of porous, injectable calcium phosphate cements – Path to osteoinductivity

With the increase of global population,people’s life expectancy is growing as well.Humans tend to live more active lifestyles and,therefore,trauma generated large defects become more common.Instances of tumour resection or pathological conditions and complex orthopaedic issues occur more frequently increasing necessity for bone substitutes.Composition of calcium phosphate cements(CPCs)is comparable to the chemical structure of bone minerals.Their ability to self-set and resorb in vivo secures a variety of potential applications in bone regeneration.Despite the years-long research and several products already reaching the market,finding the right properties for calcium phosphate cement to be osteoinductive and both injectable and suitable for clinical use is still a sudoku.This article is focused on injectable,porous CPCs,reviewing the latest developments on the path toward finding osteoinductive material,which is suitable for injection.

The Release Behavior,Biocompatibility and Physical Properties of Aid-loaded Strontium Doped Calcium Phosphate Cement

The effect of concurrent attendance of two inhibitors of bone degradation,namely Alendronate(Aid)sodium trihydrate and Strontium(Sr),on Calcium Phosphate Cement(CPC)characteristics was explored.To this aim,5 wt%Strontium and 21 mM Alendronate sodium trihydrate were used in calcium phosphate cement and setting time,ion and drug release were analyzed.RAW264.7 and G cell were cultured on cement samples and Tartrate-Resistant Acid Phosphatase(TRAP),Alkaline phosphatase(ALP)activity and MTT assay were studied.The results of structural analysis indicated that 21 mM Aid did not let the cement set.Therefore,colloidal silica was added to the cement formula and successfully decreased the setting time.In vitro tests showed Sr-loaded sample had a greater inhibitory effect on biocompatibility of G cells than Aid-loaded and Sr-Ald-loaded samples.In addition,the findings about osteoblast MTT and ALP activity indicated that Sr was more effective in osteogenic activity of G cells.The simultaneous presence of Aid and Sr in Calcium Phosphate Cement(CPC)was not as effective in its biocompatibility as the presence of Sr alone.