Synthesis of chitin calcium phosphate composite in different growth media

This paper presents some results concerning chitin calcium phosphate composites obtained in different growth media. The synthesis of chitin calcium phosphate composite was carried out by phosphorylation, calcification, and soaking in different calcium phosphate growth media. This research is focused on studying and understanding the effect of using different growth media on composite samples. Hydroxyapatite was determined in the composite samples synthesized by using both simulated body fluid (SBF) and calcium phosphorus tris (Ca‐PTris) solution. Calcium/phosphorus (Ca:P) ratio of the composite synthesized by using SBF was found higher than that of composite synthesized by using Ca‐PTris solution as calcium phosphate growth media. The Ca:P ratio of the composite (1.72) immersed in 1.5× SBF for 35 day is similar to the theoretical value of hydroxyapatite (1.67) and closer to the theoretical value of human bone (1.75). POLYM. COMPOS., 29:84–91, 2008. © 2007 Society of Plastics Engineers     

Bone‐like apatite‐coated chitosan scaffolds: Characterization and osteoblastic activity

In this study, porous scaffolds were prepared from chitosan (2% w/v in acetic acid and deacetylation degree: DD > 85%) by freeze‐drying method, and freshly lyophilized scaffolds were stabilized with ethanol solutions. Bone‐like apatite formation on chitosan scaffolds was achieved by immersing the scaffolds into a novel concentrated simulated body fluid (10× SBF‐like solution) for different periods, i.e., 6 and 24 h. Scanning electron microscope views showed that the 6‐h treatment in 10× SBF‐like solution led to the formation of calcium phosphate nucleation sites on chitosan scaffolds, whereas the apatite particles showed characteristic cauliflower‐like morphology at the end of 24‐h treatment. X‐ray diffraction results supported the fact that mineral phase was made of hydroxyapatite. Osteogenic activities of untreated and SBF‐treated chitosan scaffolds were examined by preosteoblastic MC3T3 cell culture studies. The mitochondrial activity test showed that apatite‐coated scaffolds stimulated cell proliferation compared with uncoated scaffolds. Alkaline phosphatase and osteocalcine levels indicated that the differentiation of the cells on all scaffolds increased significantly from 15th day of culture to the 21th day of culture, especially for the cells on 24‐h SBF‐treated scaffolds. The results of this study indicated that 10× SBF‐like solution‐treated chitosan scaffolds may be evaluated for bone tissue engineering. POLYM. COMPOS., 31:1418–1426, 2010. © 2009 Society of Plastics Engineers     

Apatite formation on titania–vaterite powders in simulated body fluid

Titania–hydroxyapatite composites were prepared by soaking compacts of a powder mixture consisting of crystalline titania and calcium carbonate (vaterite) to form apatite in simulated body fluid (SBF). The apatite crystal formed on compacts in SBF at 37 °C within 2 days. The apatite-forming ability of the mixtures was much higher than that of titania crystals such as anatase or rutile on their own. Calcium carbonate (vaterite), which has high solubility in the aqueous solution, plays an important role in the apatite formation; the dissolution is suggested to increase the supersaturation of the apatite in SBF. Formation of titanium hydroxide groups, which may induce the apatite formation, is drastically promoted on the powder-compacts by the soaking in SBF, independently of the structures of the titania crystals (anatase or rutile). The apatite formation on the compact of the titania–calcium carbonate (vaterite) powder mixture containing the anatase phase occurs in a shorter period than that on the one of titania (rutile)–calcium carbonate (vaterite). Crystalline titania (anatase phase) is suggested to be particularly effective in inducing the apatite nucleation.     

碳/碳复合材料表面软复合磷酸钙层

为改进碳／碳复合材料的生物活性，发展了表面软复合磷酸钙层的制备工艺。首先在碳／碳复合材料表面通过离子束辅助沉积技术形成的钛镀层，然后经浓碱液处理后呈多孔网状，该网状结构可在模拟体液（SBF）中诱导沉积出生理磷灰石层，从而在碳／碳复合材料表面形成软复合磷酸钙层。所获得的软复合磷酸钙层厚度约为8μm ，结晶结构为羟基磷灰石，但其Ca,P摩尔比n(Ca)/n(P)低于1．67。     

In vitro properties of nano-hydroxyapatite/chitosan biocomposites

In vitro behavior of the composites was performed in simulated body fluid (SBF) to induce the formation of bone-like apatite layer onto their surfaces and its enhancement in the presence of citric acid (CA). The results proved the mineralization of calcium (Ca²⁺) and phosphorus (P) ions onto the composites which contain high chitosan concentration especially after longer time of immersion. The degradation data decreased with increase chitosan content especially C2 composites (containing 30% chitosan) and highly decreased in the presence of CA which increased binding strength through the composite. The swelling % increased with increase of chitosan content in HA composite but it decreased with CA addition as increase of interaction between three matrices. The Fourier Transformed Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM-EDAX) confirmed the formation of bone-like apatite layer on the surface of the composites especially these containing CA. These biocomposites have unique in vitro properties for bone substitute's applications in the future.     

Effect of carbonate content on the in vitro bioactivity of carbonated hydroxyapatite

The effect of carbonate content on the apatite-forming ability of carbonated hydroxyapatite (CHA) in simulated body fluid (SBF) has been investigated. Five different nanocrystalline B-type CHA with carbonate content ranged from 2.01 to 5.25 wt% were prepared, sintered, and assessed for their in vitro bioactivity in SBF solution for 7-weeks under static conditions at 36.5 °C. The formation of the apatite layer and the surface morphology of CHA were examined by using a scanning electron microscope (FESEM) at week 1, 3, and 7 of SBF immersion, respectively. The Ca/P molar ratio of the CHA was determined by X-ray fluorescence (XRF). In addition, the sample weight changes and the pH of the SBF solution were measured. The results show that the formation of apatite layer depends on the carbonate content of CHA. Increasing the carbonate content caused significant increases in the surface area of CHA and the rate of apatite formation. Weight loss was observed for all CHA samples during the first week of SBF immersion, and thereafter followed by weight regain weekly until week 7. The changes in the pH of SBF and the Ca/P molar ratio were proportional to the carbonate content of CHA. This study thus highlights the importance of determining carbonate content aspect that govern the bioactivity of CHA.     

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.     

Chitosan graft copolymers‐HA/DBM biocomposites: Preparation,characterization, and in vitro evaluation

The combination of biopolymer with a bioactive component takes advantage of the osteoconductivity and osteoinductivity properties. The studies on composites containing hydroxyapatite (HA), demineralized bone matrix (DBM) fillers and chitosan biopolymer are still conducted. In the present study, the bioactive fillers were loaded onto p(HEMA‐MMA) grafted chitosan copolymer to produce a novel biocomposites having osteoinductive and osteoconductive properties. The produced composites were assessed by TGA, XRD, FTIR, and SEM techniques to prove the interaction between both matrices. In vitro behavior of these composites was performed in SBF to verify the formation of apatite layer onto their surfaces and its enhancement. The results confirmed the formation of thick apatite layer containing carbonate ions onto the surface of biocomposites especially these containing HA‐DBM mixture and pMMA having bone cement formation in their structure. These a novel biocomposites have unique bioactivity properties can be applied in bone implants and tissue engineering applications as scaffolds in future. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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.     

Investigation on structural properties and bioactivity of nanosized biphasic calcium phosphate

Synthetic biphasic bioceramics composed of hydroxyapatite (HA) and other calcium phosphates (CPs) can provide promising efficiency in the treatment of bone defects based on the rapid dissolution of the CPs, to allow its replacement by freshly formed bone, along with the slow resorption of the HA, to preserve the volume of the grafted area. For this purpose, the present study was conducted to prepare nanosized biphasic calcium phosphate (n-BCP) using a facile mechanochemical process. The experimental outputs were also compared to the commercial-grade HA in terms of physicochemical features. The Rietveld refinement was utilized to calculate the phase contents and crystal structures of the composites, including crystallite size, lattice parameters, and unit cell volume. Besides, the atomic arrangement of Ca1, Ca2, PO₄³⁻, and OH⁻ groups in the hexagonal crystal structure of HA and triclinic structure of anhydrous dicalcium phosphate (DCPA) was determined. The phase fraction, crystallite size, and the powder density of the biphasic structures, which were derived by Rietveld refinement, were found to be affected by ball-milling. In addition to biphasic structures, a monolithic hexagonal HA with an isotropic crystal growth was formed after 7 h of ball-milling under an argon atmosphere. The in vitro test in a simulated body fluid (SBF) confirmed the bioactivity of the biphasic structure through the formation of a bone-like apatite layer after one week.     

Growth of a Bonelike Apatite Layer on a Substrate by a Biomimetic Process

A dense and uniform bonelike apatite layer was formed on a substrate by the following biomimetic method. The substrate was first placed on granular particles of CaO, SiO₂-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma and then soaked in another fluid highly supersaturated with respect to the apatite. The thickness of the apatite layer increased in proportion to the soaking time in the second solution. The rate of increase in the thickness of the apatite layer increased from 0.5 to 7.0 μm/day with increasing temperature of the second solution from 10° to 60°C, increased from 0.15 to 1.7 μm/day with increasing ion concentrations of the second solution from 0.2 to 1.5 times those of the SBF, and doubled by shaking the second solution. These results indicate that the growth of the apatite layer is controlled by mass transport across the interface between the crystal and the fluid.     

Apatite Induction on Ca-Containing Titania Formed by Micro-Arc Oxidation

Ca-containing, particularly CaTiO₃, titania films were prepared by micro-arc oxidation (MAO) of Ti in an electrolytic solution containing calcium acetate monohydrate (CA), and their apatite-inducing ability was evaluated in a simulated body fluid (SBF). The phase, Ca content, and morphology of the films were found to be strongly dependent on the applied voltage. The CaTiO₃-embedded titania was obtained at higher voltages (>300 V). When immersed in SBF, no apatite was induced in all the MAO specimens irrespective of the presence of CaTiO₃, which has been claimed to be an apatite inducer. However, after a hydrothermal treatment at 250°C, apatite was formed on the surfaces of the CaTiO₃-embedded titania after 28 days, which was closely related to the formation of amorphous Ca(OH)₂ and presumably surface Ti–OH groups.     

Controlling the microstructure of lyophilized porous biocomposites by the addition of ZnO‐doped bioglass

The study presents the results of the study on porous composite biomaterials obtained using lyophilization method based on polymer solutions: chitosan solution, sodium alginate solution, or polylactide solution, and ZnO‐doped bioglass from CaO‐SiO₂‐P₂O₅ system. The properties of zinc ions were used, which have bactericidal, immune‐stimulating, and tissue‐regenerating functions in the organism. The effects of the polymer type, granulation, and bioglass amount, as well as the amount of solvent on composite microstructure, were studied. SEM‐EDS technique was used to visualize and describe the surface results occurring after incubation of composite in the Simulated Body Fluid (SBF). The selected method of preparation, used substrates, and the process conditions resulted in porous composites of the open, connected pore structure. It was proved that composite microstructure may be controlled by the appropriately selected amount of bioglass in relation to the polymer and its appropriate grain sizes. The morphology of the obtained composites is also affected by the amount of the solvent in lyophilizated dispersions. It was proved that bioactivity in composite material is induced by bioglass because after SBF incubation the surface layer is enriched with Ca and P, what may lead to a gradual formation of apatite layer. The obtained results enabled selection of the composites for further in vitro studies concerning cytotoxicity and antibacterial activity.     

Rheology,injectability, and bioactivity of bioactive glass containing chitosan/gelatin,nano pastes

Bioactive pastes containing bioactive sol–gel derived glass (BG) and various amounts of chitosan (Cn) and gelatin (Gel) were prepared in this study. To be exact, three pastes were prepared by mixing 25 parts by weight of glass powder with (a) 100 parts by weight of a 3 wt% acetic acid-based chitosan solution, (b) 100 parts by weight of a 3 wt% water-based gelatin solution, and (c) 100 parts by weight of a solution containing equal amounts of the above-mentioned solutions. The bioactivity of the composite samples was evaluated by the immersion of the prepared pastes into the simulated body fluid (SBF) solution. The samples were also analyzed by X-ray diffractometry (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and atomic absorption spectroscopy (AAS). The results indicated better apatite formation capacity on the glass-/chitosan-/gelatin-injected paste after 14 days. Furthermore, unlike the chitosan containing paste, the gelatin-containing sample was injectable and displayed viscoelastic behavior as determined by conducting the rheology test in oscillation mode. In addition, while chitosan made the paste more viscous, it improved the washout resistance when compared to the gelatin-containing sample. The experimental results also indicate the formation of spherical calcites in the pastes prior to immersion into the SBF solution.     

Phase evolution during the low temperature formation of stoichiometric hydroxyapatite-gypsum composites

Both plaster of Paris (CaSO₄·(1/2)H₂O, POP) and bone-like synthetic calcium phosphates (CaP) have been used as bone-like cements. The current study investigated the formation of composites involving POP with each of three types of stoichiometric hydroxyapatites (abbreviated as SHAp, S-SH, and C-SH, each with a Ca/P molar ratio of 1.67). The kinetics, variations in solution chemistry during the formation of these composites and phase compositions of the formed products were investigated over a course of 24 h. Although the presence of gypsum precursors was shown to decrease the alkalinity of the medium involving SHAp formation from its precursors, a delay in the growth kinetics of gypsum was observed. The same behavior was observed in the presence of commercial apatite (C-SH), whereas in the presence of synthetic apatite (S-SH), no delay was observed. A possibility of formation of a calcium sulfate phosphate double salt, as an intermediate, was investigated and confirmed by XRD analysis.     

Ultrafast bone-like apatite formation on bioactive tricalcium silicate cement using mussel-inspired polydopamine

The growing bone-like apatite layer at the tissue-implant interface is the essential condition for materials to bond robustly to surrounding bone and may provide a favorable environment for living bone formation. Inspired by versatility of mussel adhesive proteins, we developed an ultrafast and accessible route to accelerate effectively the formation of amorphous calcium phosphate (ACP), the precursor phase of bone-like apatite, on the surface of polydopamine (PDA)-coated tricalcium silicate (TCS) within 5?min in simulated body fluid (SBF). The key of the method lies in successful preparation of PDA coating on the surface of hydrated TCS by simple dip-coating of hydrated TCS in an aqueous solution of dopamine. A strong adsorption between PDA coating and surface of hydrated TCS could be formed via bidentate hydrogen and electrostatic bonds. After 7 d of soaking in SBF, the bone-like apatite layer on the surface of PDA-coated TCS disk, about 91.1?µm in height was thicker than that on the surface of pristine TCS disk, determining about 49.5?µm. The results indicate that PDA coating can facilitate the kinetic deposition of bone-like apatite on its surface. The abundant Ca²⁺ ions and the lower interface energy of ACP at the interface between ACP and surfaces of PDA-coated TCS disks are responsible for the ultrafast precipitation of ACP and formation of bone-like apatite layer which is carbonated hydroxyapatite (HA) confirmed by different analytical tools. The route can open avenues for development of PDA-coated TCS biomaterials for hard tissue repair and substitution.     

Preparation and bioactivity of apatite coating on Ti6Al4V alloy by microwave assisted aqueous chemical method

To improve the bioactivity of titanium and its alloys, dense and uniform apatite coatings were prepared on Ti6Al4V titanium substrates using microwave assisted aqueous chemical method. The influence of the pretreatment to the titanium substrates and the Ca/P molar ratio of the microwave solution on the coating deposition and morphology, as well as the bioactivity of the coated samples were studied. Results showed that during the microwave process, alkali treatment followed by heat treatment to the titanium substrates would promote the rapid deposition of hydroxyapatite to form coating. And the morphologies of the apatite coatings could be adjusted by the Ca/P molar ratio of the microwave solution. After immersion test in simulated body fluid (SBF), the coated titanium alloy exhibits a good bioactivity by inducing the formation of apatite depositions.     

Preparation of Bioglasses Developed from Bypass Cement Dust for Bone Regeneration and Comparing Their Radiation Damage Prediction with Natural Bone

Cement industry causes many respiratory diseases due to the formation of bypass cement dust (BCD) as by-product. For this purpose a new study to get ride BCD from the environment by prepared three selected bioglasses samples with composition Na₂O₍₁₀₎?+?P₂O_5(90-x)?+?BCD_(x) where x value?=?10, 20, 30 in mol%. BCD contains an appropriate amount of calcium ions that can contribute in bioglass formulation for bone regeneration. Cooperative characterization for the prepared glasses were carried out through FTIR and SEM analysis before and after immersion in simulated body fluid (SBF) solution for up to 23 days at 37 °C. Therefore, the three samples can only be directly compared in the range of BCD content between 10 and 30 wt.%. After immersion in SBF, porous apatite layer is formed on the glass surface after 13 days and become denser after 23 days. Our results showing that, the porous hydroxy apatite layer was formed faster in the BCD 30 sample than in the BCD10 and BCD 20 samples. Further, SEM analysis revealed the formation of highly porous apatite layer on the composite surfaces when immersed in SBF solution at 37 °C. These porous structures provide channels for bone in growth and improve the microscopic bioresorption. The predicting radiation damage and atomic displacements per atom in BCD-30 sample if it was implanted to a patient exposed to radiotherapy or x-rays has been calculated and compared with natural bone. The gamma shielding parameters, mass stopping power (MSP), range for both proton (H-ions) and alpha (He-ions) in bioglass-BCD-30 and human bone tissue have estimated.

     

Morphology and Osteogenetic Characteristics of Polyamide/ NanoHydroxyapatite Biocomposites

Summary  The effect of shear or time of shearing – as exerted by different screw configurations – upon the nano hydroxyapatite (n-HA) dispersion, during the twin screw extrusion processing for the preparation of PA6-66/n-HA composites, was investigated. Three different screw configurations, designated as medium, high and very high shear, were used. A noticeable improvement in the n-HA dispersion, attributed to the increasing shear exerted upon the melt during mixing in the TSE, was observed. Crystallization and thermal behavior of n-HA reinforced PA6-66 composites were studied by X-Ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). An increase in the crystallization temperature, accompanied by a decrease in percent crystallinity with the addition of n-HA to the PA6-66 matrix was observed. That is, n-HA acted as a nucleating agent and enhanced the crystallization rate. In addition, it was observed that the n-HA promoted the occurrence of the Brill transition. The decomposition temperature increased with the addition of n-HA. The PA6-66/ n-HA nanocomposite was thereafter, immersed in simulated body fluid (SBF) and the generation of a new calcium phosphate layer on the nanocomposite surface was monitored by SEM, FTIR and Atomic Absorption. The Ca/P ratio in the forming apatite layer started at a low value, ca. 1.3, which corresponds to octacalcic phosphate, but increased with the immersion time to 1.6, which corresponds to carbonated apatite.     

Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core–Shell Particle for Protein Adsorption and pH-Controlled Release

Magnetic nanoparticle composite with a cobalt ferrite (CoFe₂O₄, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug^-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.