In vitro apatite formation of calcium phosphate composite synthesized from fish bone

Calcium phosphate-based composite (CPC) is the main biomaterial substitute used for bone repair. Properties affecting bioactivity of this composite vary depending on the types of calcium phosphate crystalline phases. Hence, in this study, bioactivity behavior of novel CPC cement by the incorporation of calcium phosphate (CP), which was obtained from fish bones, dicalcium phosphate dehydrate, and chitosan solution, was monitored in simulated body fluid (SBF). In advance, the microstructure of CP produced by heat treatment (annealing) of fish bone was evaluated at two different temperatures 600 and 900°C. The X-ray diffraction (XRD) results showed that there was no secondary phase formation aside from natural hydroxyapatite (HA) in bones annealed; and the annealing process enhanced the crystallinity of CP phase in the bone matrix particularly when annealed at 900°C. After incubation of CPC cement in SBF, bone bonding ability and producing of biomimetic HA coat on the CPC cement surface were confirmed using XRD, fourier-transform infrared spectroscopy, and scanning electron microscopy. The analysis results show that needle-like and cauliflower apatite layer with the crystallite size about 100 nm was grown on the surface of CPC cement after 28 days incubation in SBF. Regardless of above findings, we conclude that varying the annealing temperature has tremendous effect on the production of natural HA from fish bone with required properties and the ultimate morphology of obtained CPC cements after soaking is directly depended on the degree of crystallinity of the prepared natural HA.     

In vitro bioactivity of novel cured ionomer cement based on iron oxide

The effect of adding Fe₂O₃ on the bioactivity of cured ionomer cement was examined in simulated body fluid (SBF). Although the polyacrylic acid and Fe₂O₃ are known as inhibitors for apatite formation, results clearly show that exposure of the cement to the SBF lead to the formation of rough layers of carbonated-apatite (Volmer–Weber growth). Interestingly, the addition of Fe₂O₃ to the cement structure decreases the possibility of acid–base reaction in ionomer cements due to the improved chemical durability of the glass. Therefore, more calcium ions were released from the cement at the initial stage of soaking which plays an important role in forming the surface apatite layer by heterogeneous nucleation via the OH⁻ groups on the cement surface.     

Micrometer-scale 3-D shape characterization of eight cements: Particle shape and cement chemistry, and the effect of particle shape on laser diffraction particle size measurement

Eight different portland cements were imaged on a synchrotron beam line at Brookhaven National Laboratory using X-ray microcomputed tomography at a voxel size of about 1 µm per cubic voxel edge. The particles ranged in size roughly between 10 µm and 100 µm. The shape and size of individual particles were computationally analyzed using spherical harmonic analysis. The particle shape difference between cements was small but significant, as judged by several different quantitative shape measures, including the particle length, width, and thickness distributions. It was found that the average shape of cement particles was closely correlated with the volume fraction of C₃S (alite) and C₂S (belite) making up the cement powder. It is shown that the non-spherical particle shape of the cements strongly influence laser diffraction results, at least in the sieve size range of 20 µm to 38 µm. Since laser diffraction particle size measurement is being increasingly used by the cement industry, while cement chemistry is always a main factor in cement production, these results could have important implications for how this kind of particle size measurement should be understood and used in the cement industry.     

Investigation of biocompatible nanosized materials for development of strong calcium phosphate bone cement: Comparison of nano-titania,nano-silicon carbide and amorphous nano-silica

The present paper deals with the effect of adding SiC, TiO₂ and SiO₂ nanoparticles on setting time, mechanical strength and hydraulic reactions of calcium phosphate cements (CPCs). The initial and final setting times of CPC increased by adding both nano-SiC and nano-TiO₂ additives but decreased by using nano-silica. Nano-titania and nano-silica had great effect on compressive strength of as-set CPC whereas slight changes were found by using nano-SiC. Although a sharp increase in compressive strength of all cements was observed by soaking them in physiological solution, the soaked additive-free cements and nano-SiO₂-added ones exhibited the greatest strength values. The results showed that adding these nano-additives did not influence on conversion rate of cement reactants to apatite phase during soaking in physiological solution period but the morphology of the formed phase was almost different. Overall, the results determined that nano-SiO₂ and nano-TiO₂ particles were appropriate additives to improve short-term mechanical strength of CPCs a(s-set CPCs), though nano-SiO₂ was found more effective because it improves the long-term mechanical strength of CPC (after soaking) too.     

Physicochemical,setting, rheological,and mechanical properties of a novel bio-composite based on apatite cement,bioactive glass,and alginate hydrogel

Calcium phosphate cements (CPC) have been widely investigated as bone substitutes, owing to their attractive features in terms of physicochemical and biocompatibility properties. However, the clinical applicability of this group of biomaterials is still critically limited by its poor strength and rheological properties in terms of injectability and cohesion. The present work aims to develop novel composite cement based on calcium phosphate cement (CPC) and bioactive glass (BG), associated with sodium alginate hydrogel (Alg). The composition, microstructure, setting, rheological, and mechanical properties of this composite cement were further investigated. Evaluation of setting properties showed that BG participates crucially in the setting reaction as a calcium and phosphate provider and serves as a setting accelerator. Thus, the setting time appears lower in these cements than in the reference CPC cement: it decreases from 75 to 42 min as the BG content increases from 10 to 25 wt% and is delayed from 42 to 73 min while the Alg amount augmented from 1 to 5 wt%. The rheological evaluation revealed that injectability was slightly improved with increasing BG content compared to the injectability of CPC, reaching a value close to 100% when combined with Alg hydrogel. The anti-washout property appeared to be weak for the CPC with or without BG, which are disintegrated in solution. The cohesiveness was significantly improved by introducing Alg hydrogel; furthermore, the addition of 5 wt% of alginate hydrogel induced an increase in the compressive strength about twice (7.2 MPa) higher than that of the reference CPC (4.0 MPa). According to the above findings, the addition of BG acts as a setting accelerator leading to a fast apatite formation, while the introduction of Alg hydrogel as a rheological promoting agent improves the injectability and cohesion. The combination of BG and Alg as additives increased the compressive strength compared to the reference cement.     

In-vitro formation and growth kinetics of apatite on a new light-cured composite calcium phosphate cement

Calcium phosphate cements are used as synthetic bone grafts with several advantages such as biocompatibility, osteoconductivity, and moldability. In this study, the synthesis of a biocement starting from calcium hydroxide (Ca(OH)₂) and Monocalcium Phosphate Monohydrate (MCPM) was investigated. A 6?wt% Na₂HPO₄ aqueous solution along with a modified polymeric resin (RIVA(SDI)^®) were adopted as the variable liquid phase in self- and light-cure cement groups. XRD analysis and FTIR spectroscopy were used to study the phase composition. The composite microstructure was characterized by scanning electron microscopy (SEM) and the degradation rates were measured by atomic absorption spectroscopy (AAS) analysis. In addition, the effect of soaking time of the cement in simulated body fluid (SBF) on the final phase and morphology was studied. The results showed that soaking the composite in SBF has a significant influence in phase transformation into hydroxyapatite, but following a slower kinetic in light-cured composite cements. Evidences of crosslinking reactions in light-cured cements were observable, which at the same time can legitimize slower apatite formation and faster biodegradation of these composite cements.     

Biomimetic apatite deposited on microarc oxidized anatase-based ceramic coating

Biomimetic apatite was formed on a microarc oxidized (MAO) anatase-based coating containing Ca and P in a simulated body fluid (SBF). At the process of the SBF immersion (0–96 h), the Ca and P of the MAO coating dissolve into the SBF, increasing the supersaturation degree near the surface of the MAO coating, which could promote the formation and growth of apatite. After SBF immersion for 7 days, the surface of the MAO coating was modified slightly. The entire surface immersed for 14 days was covered by an apatite coating. The apatite possesses carbonated structure, controllable crystallinity and pore networks. The results indicate that the MAO coating formed in an electrolyte containing phosphate and EDTA–Ca chelate complex possesses good apatite-forming ability.     

Cytocompatibility,bioactivity and mechanical strength of calcium phosphate cement reinforced with multi-walled carbon nanotubes and bovine serum albumin

This paper reports on the in vitro cytotoxicity, bioactivity behaviour and mechanical properties of novel injectable calcium phosphate cement filled with hydroxylated multi-walled carbon nanotubes and bovine serum albumin (CPC/MWCNT-OH/BSA). To predict the in vitro bioactivity of the calcium phosphate composites, we investigated apatite formation on CPC/MWCNT-OH/BSA composites after soaking in simulated body fluid (SBF) for up to 28 days. Compressive strength tests, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and cell culture experiments with human CCD-18Co fibroblasts cell lines were performed to evaluate the effect of SBF pre-treatment on the mechanical, structural and biological properties of the CPC/MWCNT-OH/BSA composites. Although apatite formation increased significantly with SBF immersion period, the results showed that all soaked CPC/MWCNT-OH/BSA composites exhibited up to 2.5 times lower compressive strength (13–20 MPa), which were however higher than values reported for the strength of trabecular bone (2–12 MPa). Cell culture experiments showed that low concentrations (6.25 and 12.5 μg/ml) of bio-mineralised CPC/MWCNT-OH/BSA composites led to cell proliferative rather than cytotoxic effects on fibroblasts, evidenced by high cell viabilities (104–113%). The novel CPC/MWCNT-OH/BSA composites presented in this study showed favourable cytocompatible and bioactive behaviour along with high compressive strength (13–32 MPa) and are therefore considered as an attractive bone filling material.     

Effect of suspension medium on the electrophoretic deposition of hydroxyapatite nanoparticles and properties of obtained coatings

The suspensions of hydroxyapatite (HA) nanoparticles were prepared in different alcohols. The zeta potential of HA nanoparticles was the highest in butanolic suspension (65.65 mV) due to the higher adsorption of RCH₂OH₂⁺ species via hydrogen bonding with surface P3OH group of HA. Electrophoretic deposition was performed at 20 and 60 V/cm for different times. Deposition rate was faster in low molecular weight alcohols due to the higher electrophoretic mobility of HA nanoparticles in them. The coating deposited from butanolic suspension had the highest adhesion strength and corrosion resistance in SBF solution at 37.5 °C. The surface of this coating was covered by apatite after immersion in SBF solution for 1 week.     

In-vitro bioactivity of wollastonite materials derived from limestone and silica sand

This paper describes the behaviour of bioactive wollastonite materials containing Malaysian limestone and silica sand. Wollastonite, which is also known as calcium silicate (CaSiO₃), is an industrial mineral composed of calcium, silicon and oxygen. Pseudowollastonite, which is a primary crystal of wollastonite, was synthesised via a solid-state reaction at a temperature of 1450 °C. The in-vitro bioactivity of wollastonite was examined by soaking it in simulated body fluid (SBF) solution for 1–7 days at 36.5 °C. The soaked wollastonite samples were characterised using XRD, SEM-EDX, FTIR and ICP analyses. Apatite particles precipitated on the surface of the wollastonite sample after the sample was soaked in the SBF. The XRD analysis indicated the presence of an increasing amount of the hydroxyapatite phase as the soaking time increased. The SEM and EDX analyses indicated the formation of granules of agglomerated apatite particles on the surface of the soaked wollastonite sample. During the formation of apatite, phosphate ions from the SBF solution were consumed. This process was confirmed by ICP, which revealed a decrease in ion concentration after the soaking process. The FTIR analysis indicated that the peaks of the phosphate ions increase when the apatite layer forms on the surface of the wollastonite sample. After the soaking process, a calcium deficient hydroxyapatite layer was observed on the wollastonite sample. The study concludes that wollastonite produced from Malaysian limestone and silica sand is bioactive and may be used as an implantable biomaterial.     

纳米二氧化硅/磷酸钙复合骨水泥的力学强度和水化过程

在磷酸钙骨水泥（CPC）中添加纳米二氧化硅（nSiO2）获得了nSiO2/CPC复合骨水泥。利用维卡仪、万能压力试验机和热导式等温量热仪研究了nSiO2的添加量对nSiO2/CPC复合骨水泥的凝结时间、抗压强度和水化行为的影响,利用X射线衍射和扫描电子显微镜等技术研究添加的nSiO2对nSiO2/CPC复合骨水泥固化产物的相组成和断面形貌的影响。研究结果表明：nSiO2添加量为5%的nSiO2/CPC复合骨水泥凝结时间由16 min缩短到10 min,抗压强度由原来的（24 2）MPa增加到（33 4）MPa,提高了38%,但添加超过5%的nSiO2会影响水化产物磷灰石的生成从而使复合骨水泥的力学强度下降。在水化反应过程中,一方面nSiO2作为填料,吸附了固化液中的水导致CPC的实际固液比增大,减弱了CPC的水化进程,由于实际固化液下降也减少了水化产物的孔隙大小和数目;另一方面,nSiO2与水化产生的Ca（OH）2发生化学反应形成CSH凝胶,改善了nSiO2和CPC基体之间的界面结合。这两方面的作用结果使得添加适量的nSiO2可以提高nSiO2/CPC复合骨水泥的抗压强度,缩短其凝结时间。     

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.     

钼锑抗分光光度法测定工业过氧化氢溶液中的磷酸盐

钼锑抗分光光度法稍做改进测定工业过氧化氢溶液中的磷酸盐含量。由于过氧化氢具有强氧化性,在酸性条件下与还原剂抗坏血酸作用[1],影响显色反应,在测定过程中加入足量的抗坏血酸溶液,能消除干扰。结果表明当含磷量范围在0~30μg/mL,加入9.0 mL 10%抗坏血酸溶液,方法的相对标准偏差1.0%,加标回收率为97.5%~101.5%,准确度较好。     

Polymeric calcium phosphate cements incorporated with poly‐γ‐glutamic acid: Comparative study of poly‐γ‐glutamic acid and citric acid

Polymeric calcium phosphate cements (PCPC) derived from biodegradable poly‐γ‐glutamic acid (γ‐PGA) were prepared in an attempt to improve the mechanical strength of calcium phosphate cement (CPC). The characteristics of the PCPCs were compared with those of cement incorporated with citric acid. The diametral tensile and compressive strengths of the CPC incorporated with γ‐PGA were significantly higher than that of cement incorporated with citric acid at equivalent concentrations (P < 0.05). The maximal diametral tensile and compressive strengths of the CPC incubated for 1 week in physiological saline solution were approximately 18.0 and 50.0 MPa, respectively. However, the initial setting time of the PCPC was slower than that of CPC incorporated with citric acid. The formation of ionic complexes between calcium ions and γ‐PGA was observed using FTIR spectroscopy. Hydroxyapatite (HA) formation was retarded by γ‐PGA incorporation according to scanning electronic microscopy (SEM) and powder X‐ray diffraction (XRD) observations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A gap-graded particle size distribution for blended cements: Analytical approach and experimental validation

To increase the packing density of blended cement paste, a gap-graded particle size distribution (PSD) was theoretically deduced and modified according to the wet density of actual paste. Then experiments were conducted to validate the hypothesis of improvement of the properties of blended cements by the gap-graded PSDs proposed. The experimental results show that the gap-graded PSD resulted in a decreased water requirement and an increased packing density of blended cement paste, and modified gap-graded PSDs gave further effects. The heat of hydration of gap-graded blended cement pastes released slowly in the first 24 h and increased rapidly afterward. The microstructure of gap-graded blended cements was much more homogeneous and denser than that of reference blended cement, therefore both early and late mechanical properties of low clinker gap-graded blended cements were improved significantly and even higher than those of Portland cement.     

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.     

Effects of chitosan and zirconia on setting time,mechanical strength,and bioactivity of calcium silicate‐based cement

In this research, we aimed at improving the setting properties and biocompatibility of the mineral trioxide aggregate‐like cements while maintaining the main chemical formula. Consequently, chitosan and zirconium oxide were added to the cement instead of bismuth oxide to improve the mechanical behavior, limit the possible toxicity, and enhance the bioactivity of the cements. Adding zirconia resulted in a shorter setting time and adding chitosan contributed to the setting time, mechanical strength, and biocompatibility at the same time. Thus, cements containing both chitosan and zirconia had the shortest setting time, highest compressive strength, and apatite‐forming ability.     

Fabrication and characterization of porous silver powder prepared by spray drying and calcining technology

High porosity porous silver powder with about 100 µm average size and 5 µm pore size was fabricated by spray drying and calcining technology. Effects of calcining temperature and process of spray-dried powder on the phases, grain size, particle morphology and pore microstructure of silver powder were investigated. The results showed that porous silver with approximately spherical shape and via hole structure was obtained using 0.25 mol Ag₂CO₃ solution of ammonia water, which was spray-dried at 200 °C and calcined at 400 °C for 30 min with heat treatment technology curve of gradient temperature in air. And there were not Ag₂CO₃, Ag₂O and AgO phases existing in the porous silver. However, using 0.25 mol Ag₂CO₃ solution of ammonia water, the porous silver powder could not be fabricated by spray pyrolysis technology with a solution feed rate of 300 mL/h, flux of carrier gas of 0.30 MPa, and 640 °C furnace set temperature.     

Bone-like forming ability of apatite-wollastonite glass ceramic

This research describes the preparation, characterisation and in vitro behavior of a bioactive glass ceramic containing 44.8 wt% apatite, 28.0 wt% wollastonite-2 M and 27.2 wt% of amorphous phase. The biomaterial was obtained by a specific thermal cycle process that caused the devitrification of the Ca₃(PO₄)₂-CaSiO₃ binary system's stoichiometric eutectic composition. Overall, the material combines the properties of a resorbable Si-Ca-rich glass, in addition to bioactive properties of wollastonite and apatite phases. The bioactivity of this material was studied by soaking the samples in a simulated body fluid (SFB) for 3, 7, 14 and 21 days at 36.5 °C. During the soaking, the amorphous phase and also wollastonite-2 M phase underwent steady dissolution by releasing Si and Ca ions into the SBF medium. After 7 days, a porous hydroxy-carbonate apatite (HCA) layer was formed at the SBF-glass ceramic interface. The micro-nanostructured apatite-wollastonite-2 M glass ceramics with improved mechanical properties, in comparison with the parent glass, could serve as a promising platform for hard tissue regeneration.     

Development of solid-phase microextraction for the determination of trihalomethanes in drinking water from Bizerte, Tunisia

Headspace-solid-phase microextraction (HS-SPME) combined with gas chromatography-electron capture detector (GC-ECD) has been developed and studied for the determination of trihalomethanes (THMs) in treated water samples. Experimental parameters such as the selection of thickness of the polymer coating, addition of salt, magnetic stirring, extraction temperature, and extraction time were studied. Extraction of the analytes was performed using HS-SPME with a 100 µm poly(dimethylsiloxane) coating followed by thermal desorption at 250 °C and GC analysis. The optimized conditions were 20 min extraction time at 35 °C with 25 w/v% NaCl. Analytical parameters such as linearity and limit of detection were also evaluated. The linear range of 1-100 µg/l was established with relative standard deviations (%RSD) within the range, 1.3-11.7%. The limits of detection (LODs) were ranged from 1.4 ng/l to 6.1 ng/l. The average THM concentration was 88.16 µg/l which was well within the proposed European Union directive of 100 µg/l.