Setting properties,mechanical strength and in vivo evaluation of calcium phosphate-based bone cements

Calcium phosphate cement (CPC) is a promising material for use in minimally invasive surgery for bone defect repair due to its similarity to the mineral phase of bone, biocompatibility, bioactivity, self-setting characteristics, low setting temperature, adequate stiffness and ease of shaping in complicated geometrics. In this study, we systematically investigate the influence of preparation variables on the final properties of CPCs. We determined the effects of CPC composition, accelerators, seed hydroxyapatite and reaction temperatures on the setting times and compressive strength of CPCs based on tetracalcium phosphate (TTCP), dicalcium phosphate dehydrate (DCPD), dicalcium phosphate anhydrous (DCPA), and α-tricalcium phosphate (α-TCP). The three types of CPCs (TTCP/DCPD, TTCP/DCPA, and TTCP/α-TCP-based bone cements) were prepared by varying the amounts of seed hydroxyapatite and citric acid used as a hardening accelerator. After 24 h of incubation, all three types of bone cements exhibited the characteristic peaks attributable to hydroxyapatite (HA) without characteristic peaks of unreacted raw materials. These results indicated that the bone cements were completely converted to HA. TTCP/DCPD-based bone cements showed faster setting times than TTCP/DCPA and TTCP/α-TCP-based bone cements. As citric acid concentrations in the liquid phase increased, the setting times of all three types of bone cements gradually decreased. However, the concentrations of seed HA in the cements were not related to significant changes in setting time. The compressive strengths of CPCs were significantly influenced by composition and reaction temperature. We also studied the effects of immersion time in physiological solution on the properties of the various CPCs. In the results of in vivo tests, subjects with bone defects implanted with CPCs exhibited more bone formation than control subjects that did not receive implantations of CPCs.     

Effects of strontium doping on the degradation and Sr ion release behaviors of α‐tricalcium phosphate bone cement

Strontium plays important physicochemical and biological roles in the applications of bone repair materials. The available methods of Sr doping in bone cements were believed to make a key effect on the biodegradation and Sr ion release behaviors of cements. In this work, Sr‐doped octacalcium phosphate (Sr‐OCP), Sr‐doped α‐tricalcium phosphate (Sr‐α‐TCP), SrCO₃, and SrCl₂ with different actual availability of Sr²⁺ were imported into α‐TCP bone cements, and their effects on the biodegradation and ions release of cements were comparatively investigated. Incorporation of different Sr carriers had led to distinct hydration morphologies, crystal evolutions, degradation rates, and microenvironments of bone cements during their in vitro biodegradation. Compared with other Sr carriers, Sr‐OCP facilitated the hydration reaction of α‐TCP, which induced the enhanced degradation and Sr ion release behaviors. In conclusion, Sr‐OCP was supposed to be a more potential Sr carrier applied in the synthesis of biodegradable Sr‐doped calcium phosphate bone cements.     

Study on the new bone cement based on calcium sulfate and Mg,CO3 doped hydroxyapatite

In order to improve some features of bone substitutes the new self-setting composite-type implant material based on Mg²⁺/CO₃^2? co-substituted hydroxyapatite (Mg-CHA) and calcium sulfate hemihydrate (CSH) was developed. Synthetic hydroxyapatites doped with small amounts of additives found in natural bone (e.g. Mg²⁺ and CO₃^2?) are regarded as promising components of calcium phosphate bone cements (CPCs). The CPCs, now available on the market, due to low resorption rate are too stable to permit material degradation and are slowly replaced by the newly formed bone. To improve cement resorption we used calcium sulfate which is a well-known biodegradable and biocompatible bone defect filler. Combining properties of Mg-CHA and CSH allowed developing a new, promising, easy shapeable implant material with high potential for bone regeneration.     

The ionic substituted octacalcium phosphate for biomedical applications: A new pathway to follow?

Numerous studies have found that octacalcium phosphate possesses promising biological properties applicable to bone tissue regeneration. To further improve the osteogenic and regenerative properties of octacalcium phosphate, substitutions with Sr²⁺, Zn²⁺, Mg²⁺, Fe³⁺, Na⁺, F^? and CO₃^2? ions have been investigated in recent years. Despite that, hydroxyapatite is still considered the most promising calcium phosphate for bioactive bone grafts due to its biocompatibility, physicochemical similarity to biological apatite, osteoconductivity and strong bonding with the surrounding tissue. However, better biological properties of octacalcium phosphate in vivo as well as a larger volume of regenerated bone tissue, compared to hydroxyapatite, were confirmed by many studies. This review summarizes recent and relevant studies on cationic and anionic substitutions in the crystal lattice of octacalcium phosphate and its in vitro biological performance. It also discusses future challenges and prospects for the use of substituted octacalacium phosphate.     

Strontium-loaded magnesium phosphate bone cements and effect of polymeric additives

Magnesium phosphate-based cements (MPCs) are nowadays regarded as promising materials in the field of bone repair. The inclusion of Sr ions in the formulations may represent a valuable strategy to improve their bone regeneration performances, but the effect that such ion exerts on the physico-chemical properties of the material have not been investigated so far. In this work we describe the development of Sr-MPCs obtained including Sr ions in different forms, i.e., using Sr-substituted tri-magnesium phosphate precursor powder or including in the formulation Sr-based salts (SrCl₂ and SrHPO₄). The materials were characterized both in the form of pastes and hardened cements, finding that according to the type of Sr precursor used we can tune the setting time, the amount of binding phases in the cements, their morphology and thermal behavior. The dissolution behavior and the release kinetics of Mg²⁺ and Sr²⁺ can as well be modulated, and in particular the use of SrCl₂ in the formulation leads to a higher dissolution and a faster release of a significant amount of both Mg²⁺ and Sr²⁺, compared to the other samples. Given the unsatisfying performances obtained during the injectability and anti-washout tests, we also included two polymeric additives, namely poly(N-isopropylacrylamide) and mucin, in the Sr-MPCs formulations. The results demonstrate that it is possible to obtain Sr-MPCs with promising properties for applications as bone cements, that can be tuned according to the form under which Sr is included in the formulation. In addition, mucin markedly improves the cohesion and injectability of the Sr-MPC pastes, providing a simple but effective strategy to develop materials of interest in the orthopedic field.     

聚丙烯酸对(TTCP MCPM β-TCP)系骨水泥理化性质的影响

用聚丙烯酸(PAA)作为固化液,对磷酸四钙(TTCP)+一水磷酸二氢钙(MCPM)+β-磷酸三钙(β-TCP)系骨水泥理化性质进行研究。结果表明,随着液固比(固化液体积mL/固相总质量g,下同)增大,固化时间延长,液固比为1.0 mL/g时,终凝时间达7 min;抗压强度随液固比增大,先升高后降低,液固比为0.8 mL/g时,达到最大值20.86 MPa;随浸泡时间增加,降解率先增加后逐渐趋于稳定;X射线分析(XRD)结果显示,随液固比改变,固化反应结晶物有羟基磷灰石(HA)和二水磷酸氢钙(DCPD)相出现,晶相的差异造成骨水泥降解率不同。     

Synthesis of weakly crystallized hydroxyapatite with Zn substitution and its effect on the calcium phosphate and calcium sulfate cements

Zn is an essential trace element in the normal growth and loading Zn into biomaterials for biomedical applications has always been a hot topic due to its immune regulation. The preparation and characterization of Zn-substituted weakly crystallized hydroxyapatite (WCH) are studied in this work, and Zn-substituted WCH was added to calcium phosphate and calcium sulfate cements (CPC and CSC) to address the effect of Zn²⁺ on the hydration crystallization behavior of calcium phosphate and calcium sulfate. Our results demonstrate that Zn²⁺ will inhibit the transformation of α-TCP to HA during the hydration reaction of CPC. And the adding of Zn²⁺ in CSC changed the crystallization morphology of calcium sulfate. The regulation of Zn on the crystallization behavior of calcium phosphate and calcium sulfate resulted in the different in vitro degradation behaviors of CPC and CSC. With the purpose of improving the biological effects of materials, the polarization of Zn²⁺ released from cements on macrophages was also characterized in this work, and the results showed that appropriate concentrations of Zn²⁺ can inhibit inflammation after stimulating RAW264.7 cells for an appropriate period of time. The presented results may be useful guidelines for the preparation and design of composite bone cement with specific Zn content.     

Effects of Sr2+/Zn2+ co-substitution on crystal structure and properties of nano-β-tricalcium phosphate

The incorporation of therapeutic ions like Sr²⁺, Si⁴⁺, Zn²⁺ and Li⁺ into biomaterials has become a promising approach to promote bone regeneration. However, the effects of Sr²⁺ and Zn²⁺ co-substitution on the crystal structure and properties of β-tricalcium phosphate (β-TCP) have not been elucidated well. In this study, Sr²⁺/Zn²⁺ co-substituted β-tricalcium phosphate (SrZnTCP) nano-powders with different extents of substitution (0–4.8 mol%) were synthesized by poly(ethylene glycol)-assisted co-precipitation and subsequent heat treatment. The as-synthesized SrZnTCP nano-powders were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, Rietveld refinement and differential scanning calorimetry. The results showed that the conversion of calcium-deficient apatite to β-TCP was achieved after heat-treatment above 800 °C. The a-axis and c-axis lattice parameters gradually decreased with increasing level of Sr²⁺/Zn²⁺ co-substitution in β-TCP lattice. Sr²⁺ and Zn²⁺ preferentially occupied the ninefold coordinated Ca (4) sites and the sixfold coordinated Ca (5) sites, respectively. The co-substitution of Sr²⁺ and Zn²⁺ for Ca²⁺ significantly improved the thermal stability of β-TCP. The release rate of Zn²⁺ from SrZnTCP depended on Ca²⁺ concentration over 63-day immersion in PBS solution while that of Sr²⁺ was not affected by Ca²⁺ concentration. The amount of Sr²⁺ released increased with increasing Sr²⁺ content in SrZnTCP. Collectively, SrZnTCP showed great promise as a Sr²⁺/Zn²⁺-releasing biomaterial for bone repair, although no obvious mineralization was observed on β-TCP and SrZnTCP disc samples during 56 days of immersion in simulated body fluid.     

Synthesis,Characterization, Antibacterial Properties,and In Vitro Studies of Selenium and Strontium Co-Substituted Hydroxyapatite

In this study, as a measure to enhance the antimicrobial activity of biomaterials, the selenium ions have been substituted into hydroxyapatite (HA) at different concentration levels. To balance the potential cytotoxic effects of selenite ions (SeO₃²⁻) in HA, strontium (Sr²⁺) was co-substituted at the same concentration. Selenium and strontium-substituted hydroxyapatites (Se-Sr-HA) at equal molar ratios of x Se/(Se + P) and x Sr/(Sr + Ca) at (x = 0, 0.01, 0.03, 0.05, 0.1, and 0.2) were synthesized via the wet precipitation route and sintered at 900 °C. The effect of the two-ion concentration on morphology, surface charge, composition, antibacterial ability, and cell viability were studied. X-ray diffraction verified the phase purity and confirmed the substitution of selenium and strontium ions. Acellular in vitro bioactivity tests revealed that Se-Sr-HA was highly bioactive compared to pure HA. Se-Sr-HA samples showed excellent antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus carnosus) bacterial strains. In vitro cell–material interaction, using human osteosarcoma cells MG-63 studied by WST-8 assay, showed that Se-HA has a cytotoxic effect; however, the co-substitution of strontium in Se-HA offsets the negative impact of selenium and enhanced the biological properties of HA. Hence, the prepared samples are a suitable choice for antibacterial coatings and bone filler applications.     

Study on the improvement of compressive strength and fracture toughness of calcium phosphate cement

Calcium phosphate cement (CPC) has superior properties, such as excellent bioactivity, biocompatibility, osteoconductivity and degradability, since its hydration product is hydroxyapatite (HA). As a novel cement material, CPC also shows injectable and self-setting properties. However, the compressive strength (CS) and fracture toughness of most CPCs are far lower than that of human weight-bearing bones, which largely limit their applications in the repairment of weight-bearing bones. To improve the CS and fracture toughness of CPC, several methods, including in-situ reinforcement by Ca4(PO4)2O (TTCP) ceramic particles, suitable nanofibers are introduced in this study. The maximal CS of CPC prepared with TTCP (average particle size of 22.3 ± 0.4 μm) reached to 98.4 MPa, which is close to the strength of human long bones. The enhanced CS of CPC was attributed to the in-situ reinforcing effect of residual TTCP particles. Tendon collagen slices and HA nanofibers were used to improve the fracture toughness of CPC. The flexural strength (FS) and the work of facture (WOF) of CPC were slightly increased by adding HA nanofibers but was significantly increased by the addition of tendon collagen slices. With 1.000 wt% tendon collagen slices, the FS and WOF of CPC were increased by 61.3% and 22.6 times, respectively.     

Antimicrobial properties of co-doped tricalcium phosphates Ca3-2x(MˊMˊˊ)x(PO4)2 (M = Zn2+, Cu2+, Mn2+ and Sr2+)

The substituted (Ca²⁺/Cu²⁺), and co-substituted (Cu²⁺/Zn²⁺), (Cu²⁺/Sr²⁺), and (Sr²⁺/Mn²⁺) β-tricalcium phosphate (β-TCP)-based Ca_3-2x(MˊMˊˊ)_x(PO₄)₂ (M = Zn²⁺, Cu²⁺, Mn²⁺ and Sr²⁺) solid solutions have been synthesized using solid-state route. The powder X-ray diffraction study shows the formation of β-TCP-type structure as the main phase in all solid solutions. The crystal structures and chemical compositions were approved using Fourier-transform infrared (FT-IR) absorption spectra and energy-dispersive X-ray spectrometry (EDX) data, respectively. The unit cell parameters and volume of as-synthesized samples directly depend on the radius of the incorporated ions. The limits of the single-phase solid solutions were found based on the possible occupation of the crystal sites in β-TCP structure. For the divalent ions with small radii, such as Cu²⁺ or Zn²⁺, the limit composition was found as Ca_2.571Mˊ_0.429–xMˊˊ_x(PO₄)₂ for Mˊ and Mˊˊ – Cu²⁺ and Zn²⁺. The enlargement of the unit cell by incorporation of Sr²⁺ allows to extend the limit of solid solutions up to Ca_2.5Sr_0.5–xMˊ_x(PO₄)₂ for Mˊ – Cu²⁺ or Mn²⁺. The antibacterial properties were studied on 4 bacteria (S. aureus, P. aeruginosa, E. coli and E. faecalis) and 1 fungus (C. albicans). It has been showed that co-doped Ca_2.5Sr_0.25Cu_0.25(PO₄)₂ sample exhibits the highest antimicrobial activity resulting in 92%, 96% and 96% inhibition growth rate for S. aureus, P. aeruginosa and E. faecalis, respectively. The antimicrobial properties are strongly related to the occupation of the crystal sites in the β-TCP structure by doping ions.     

Preparation and characterization of calcium phosphate bone cement with rapidly-generated tubular macroporous structure by incorporation of polysaccharide-based microstrips

Calcium phosphate cements (CPCs) have been extensively used as bone graft substitutes for the repair of bone defect due to its biocompatibility, osteoconductivity and in-situ setting capability. They poorly degrade thus limiting their use in tissue engineering application. A possible strategy to improve the speed of CPC degradation is to add porogen to CPC to create macropores that can enhance cement resorption and can consequently be replaced by new bone. The as-generated macropores are generally not connected because of spherical shape of the porogens which can limit the extent of newly formed bone. The aim of this study was to fabricate CPCs having tubular macroporous structure by incorporating fast-dissolving maltodextrin microstrips (MDMS) and explore their properties such as setting time, mechanical property, microstructure and degradability of the cements. The results showed that after immersing MDMS-embedded composites in simulated body fluid under physiological condition for 1 d MDMS rapidly disintegrated (more than 70%), generating tubular macropores in CPCs. The disintegration of MDMS completed in 1 week. CPCs containing MDMS lower than 30% by weight had the same final setting time as those without MDMS. The average values of compressive strength of the CPC composites decreased with the disintegration of MDMS. % Porosity and pore interconnectivity increased with increasing MDMS content. In addition, MDMS-embedded CPCs were cell friendly with excellent cell adhesion, indicating a possible candidate as bone graft substitutes.     

Strontium and zinc co-substituted nanophase hydroxyapatite

It is well documented that biological hydroxyapatite (HA) differs from pure and synthetically produced HA, and contains of a mixture of calcium phosphate (CaP) phases in addition to a range of impurity ions, such as strontium (Sr²⁺), zinc (Zn²⁺), magnesium (Mg²⁺), fluoride (F^-) and carbonate(CO₃^2-), but to name a few. Further to this, biological apatite is generally in the form of rod (or needle-like) crystals in the nanometre (nm) size range, typically 60 nm in length by 5–20 nm wide. In this study, a range of nano-hydroxyapatite (nHA), substituted nHA materials and co-substituted nHA (based on Sr²⁺ and Zn²⁺) were manufactured using an aqueous precipitation method. Sr²⁺ and Zn²⁺ were chosen due to the significant performance enhancements that these substitutions can deliver. The materials were then characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) techniques. The TEM results show that all of the samples produced were nano-sized, with Zn-substituted nHA being the smallest crystals around 27 nm long and 8 nm wide. The FTIR, XRD and XPS results all confirm that the materials had undergone substitution with either Sr²⁺ and Zn²⁺, for Ca²⁺ within the HA lattice (or both in the case of the co-substituted materials). The FTIR results confirmed that all of the samples were carbonated, with a significant loss of hydroxylation as a consequence of the incorporation of Sr²⁺ and Zn²⁺ into the HA lattice. None of the materials synthesised here in this study contained any other impurity CaP phases. Therefore this study has shown that substituted and co-substituted nanoscale apatites can be prepared, and that the degree of substitution (and the substituting ion) can have a profound effect of the attendant materials’ properties.     

Multiphase zinc and magnesium mono-substituted calcium phosphates derived from cuttlefish bone: A multifunctional biomaterials

Biomimetic calcium phosphate (CaP) systems mono-substituted with zinc (Zn²⁺) and magnesium (Mg²⁺) ions were prepared from a biogenic source (cuttlefish bone) by wet precipitation method. The results revealed that the as-prepared powders were composed of calcium-deficient carbonated hydroxyapatite (HAp), octacalcium phosphate (OCP), and amorphous calcium phosphate (ACP), while the heat-treated powders consisted of HAp, α-tricalcium phosphate (α-TCP), and β-tricalcium phosphate (β-TCP). In addition to Zn²⁺ and Mg²⁺ ions, the presence of CO₃^2?, Sr²⁺ and Na ⁺ ions was detected with elemental analysis, which can be attributed to the use of cuttlefish bone as a natural precursor of Ca²⁺ ions. The data obtained by XRD study demonstrated the decrease in lattice parameters in the OCP and β-TCP phases for Zn-substitution and Mg-substitution in the HAp, OCP, and β-TCP phases. Zn²⁺ occupies the Ca(1,3,4,6,7,8) sites in OCP and Ca(1,2,3,4) sites in β-TCP, while Mg²⁺ occupies the Ca(2) sites in HAp and the Ca(4,5) sites in β-TCP. Phase transformation study under simulated physiological conditions for 7 days showed the transformation of OCP and ACP into the thermodynamically more stable HAp. Characterization of the zeta-potential showed positively charged populations for all prepared CaP powders, while all samples showed high bovine serum albumin adsorption capacity. The culture of human embryonic kidney cells showed that the prepared CaPs are non-cytotoxic and that viability of the cells increases during the culture period. All powders obtained showed antibacterial activity towards Gram-negative Escherichia coli and low antibacterial effect against Gram-positive Staphylococcus aureus, as determined by viability analysis during 48 h. Inhibition zone analysis and observation of the morphology after 24 h showed no antibacterial properties.     

Effects of strontium substitution on the phase transformation and crystal structure of calcium phosphate derived by chemical precipitation

This study focused on the effects of strontium substitution on the phase transformation and crystal structure of calcium phosphate. Chemical precipitation was used to prepare Sr-doped hydroxyapatite (HA) precursor powders. The phase transformation of the as-prepared samples during sintering was analyzed. The powders were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Quantitative analysis of the phase content and fine structure was performed by Rietveld refinement. Sr doping was found to facilitate the phase transformation from HA to beta-tricalcium phosphate (β-TCP) at 1000 °C. The β-TCP content increased with increasing Sr content, causing a decline in the ratio of HA to β-TCP. With Sr contents of ≤5 mol%, HA remained the major phase in the biphasic mixtures; in contrast, with Sr contents of ≥15 mol%, the mass fraction of β-TCP exceeded 50%. The incorporation of Sr²⁺ into HA and β-TCP caused the lattice parameters of both phases to increase. Additionally, Sr incorporation slightly enhanced the binding energy of Ca. The study confirmed that Sr doping could be used to modulate the phase fractions of HA and β-TCP. The effective partial substitution of Sr in both HA and β-TCP makes these materials promising for bone repair.     

Investigation of antimicrobial properties and in-vitro bioactivity of Ce3+-Sr2+dual-substituted nano hydroxyapatites

Dual doped calcium apatite has been widely focused as it enhances the osteoconductive property for the possible applications in orthopedic and dental implants. In this work, we investigate the antimicrobial and bioactive properties of cerium/strontium (Ce³⁺/Sr²⁺) co-substituted hydroxyapatite (HA) nanoparticles synthesized by sol-gel assisted precipitation method. The structure, morphology, functional groups, photoluminescence, and thermal stability of the developed systems are examined. The comparative studies performed among the pure HA, Sr²⁺, and Ce³⁺-substituted HA nanoparticles illustrate higher antibacterial activity with lowered apatite-forming ability and biocompatibility for the Ce³⁺-substituted HA. However, the Ce³⁺/Sr²⁺co-substituted HA exhibits better biocompatibility, apatite-forming ability, and good antimicrobial properties. Sr²⁺ ion inclusion leads to better biological properties and compromise the cytotoxic nature of the Ce³⁺-HA. In addition, the Ce³⁺/Sr²⁺-HA nanoparticles prevent thermal decomposition up to 700°C, pointing also toward the possibility of this co-substituted HA in bone implant applications.     

Strontium and copper co-substituted hydroxyapatite-based coatings with improved antibacterial activity and cytocompatibility fabricated by electrodeposition

Bacterial infection are serious complications for biomedical implants in the orthopedic and dental fields, and the ideal implants should combine good antibacterial ability and bioactivity. In this paper, we have fabricated the strontium/copper substituted hydroxyapatite (SrCuHA) coating on the commercially pure titanium (CP-Ti) and studied their effect on antibacterial and in vitro cytocompatible properties. Cu was incorporated into HA in order to improve its antimicrobial properties. Sr was added as a second binary element to improve the biocompatibility. The structural and morphological characteristics of the SrCuHA coatings were investigated using various analytical techniques. The presence of Sr²⁺ and Cu²⁺ in solution led to reduced roughness of the coating and finer nucleus size formed. The results highlight that Sr²⁺ and Cu²⁺ were homogenously incorporated into HA lattice to form SrCuHA coatings. Inductively coupled plasma mass spectrometry (ICP-MS) was used for the leach out analysis of the samples. A low contact angle value revealed the hydrophilic nature. In vitro electrochemical corrosion studies indicated that the SrCuHA coating sustain in the stimulated body-fluid (SBF), exhibiting superior corrosion resistance with a lower corrosion penetration rate than the bare CP-Ti substrate. The SrCuHA coatings can kill Escherichia coli to a certain extent during the first few days, which might be due to the Cu substitution in the coating. An enhancement of in vitro osteoblast adhesion, proliferation, and alkaline phosphatase activity was observed, which could lead to the optimistic orthopedic and dental applications.     

Improvement of in vitro osteogenesis and antimicrobial activity of injectable brushite for bone repair by incorporating with Se-loaded calcium phosphate

The main objective of this research is to study the effect of selenium (Se) on injectable brushite cement (Bru) derived from Se-loaded cement starting calcium phosphate powder (SP) to reveal whether injectable Se-loaded Bru has potential for bone repair. Se was incorporated into Bru by cement SP with a Se/P molar ratio of 0.05, 0.10, and 0.15, respectively. The results show that although the cement SP changes from β-calcium phosphate to hydroxyapatite as the Se content increases, brushite is still the dominant crystalline phase of the cements. The increase of Se concentration prolongs the cement setting time and promote the cement injectability, however, excellent anti-washout ability and degradability is observed for all the cements. Moreover, the cements with higher content of Se release out Se faster when soaking in phosphate buffer saline. The cell experimental results show that cements with a Se/P of 0.05 and 0.10 can not only be beneficial for osteoblastic MG63 cells adhesion and proliferation but also enhance cell mineralization property, while the cement with a Se/P ratio of 0.15 shows cytotoxicity. Furthermore, both the agar plate tests and the broth antimicrobial tests reveal that Se-loaded Bru can significantly inhibit the growth of E. coil, S. aureus, and P. aeruginosa. The antibacterial activity increases with the increase of Se concentration in the cement. Therefore, the biological performance of injectable Se-loaded brushite cement is dose-dependent and brushite cement with an appropriate dose of Se has potential for bone repair application.     

Synthesis and characterisation of nanophase hydroxyapatite co-substituted with strontium and zinc

In order to develop new bioactive calcium phosphate (CaP) materials to repair bone defects, it is important to ensure these materials more closely mimic the non-stoichiometric nature of biological hydroxyapatite (HA). Typically, biological HA combines various CaP phases with different impurity ions, which substitute within the HA lattice, including strontium (Sr²⁺), zinc (Zn²⁺), magnesium (Mg²⁺), carbonate (CO₃^2-) and fluoride (F^-), but to name a few. In addition to this biological HA have dimensions in the nanometre (nm) range, usually 60?nm in length by 5–20?nm wide. Both the effects of ion substitution and the nano-size crystals are seen as important factors for enhancing their potential biofunctionality. The driving hypothesis was to successfully synthesise nanoscale hydroxyapatite (nHA), co-substituted with strontium (Sr²⁺) and zinc (Zn²⁺) ions in varying concentrations using an aqueous precipitation method and to understand their chemical and physical properties. The materials were characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) techniques. The FTIR, XRD and XPS results confirmed that the nHA was successfully co-substituted with Sr²⁺ and Zn²⁺, replacing Ca²⁺ within the nHA lattice at varying concentrations. The FTIR results confirmed that all of the samples were carbonated, with a significant loss of hydroxylation as a consequence of the incorporation of Sr²⁺ and Zn²⁺ into the nHA lattice. The TEM results showed that each sample produced was nano-sized, with the Sr/Zn-10%nHA having the smallest sized crystals approximately 17.6 ± 3.3?nm long and 10.2 ± 1.4?nm wide. None of the materials synthesised here in this study contained any other impurity CaP phases. Therefore, this study has shown that co-substituted nHA can be prepared, and that the degree of substitution (and the substituting ion) can have a profound effect on the attendant materials’ properties.     

Synergistically reinforcement of a self-setting calcium phosphate cement with bioactive glass fibers

Calcium phosphate cements (CPCs) are highly promising for clinical uses due to their in situ-setting ability, excellent osteoconductivity and bone-replacement capability. However, the low strength limits their uses to non-load-bearing applications. In the present research, first, bioactive glass fibers (BGFs) in the ternary SiO₂-CaO-P₂O₅ system were prepared, and then the fiber composites with compositions based on CPC and BGFs were prepared and characterized. Then, the effect of structure and amount of BGF incorporation into the CPC system, and the effect of mechanical compaction on the fiber-modified system were investigated. The results showed that the compressive strength of the set cements without any BGFs was 0.635 MPa which was optimally increased to 3.69 MPa by applying 15% BGF and then decreased by further addition of it. In addition, both the work-of-fracture and elastic modulus of the cement were considerably increased after applying the fibers in the cement composition. Also, the setting time slightly decreased by applying the fibers. In summary, processing parameters were tailored to achieve optimum mechanical properties and strength. The prepared composite may be useful in surgical sites that are not freely accessible by open surgery or when using minimally invasive techniques.