Preparation and structural characterisation of a novel ferrocene–amino acid conjugate

A new type of ferrocene–amino acid conjugate, 2-[(methoxycarbonyl)methyl]-2-aza[3]ferrocenophane (1), was obtained in a rather low yield via condensation reaction of 1,1′-bis(hydroxymethyl)ferrocene and glycine methyl ester in the presence of [RuCl₂(PPh₃)₃] as a catalyst. The compound was characterised by combustion analysis and by spectroscopic method, and its solid-state structure was established by single-crystal X-ray diffraction analysis. Compound 1 is reluctant towards alkylation with MeI but readily forms a stable picrate salt. Cyclic voltammetry experiments on 1 (in CH₃CN at Pt electrode) revealed the compound to undergo a one-electron reversible oxidation attributable to ferrocene/ferrocenium couple (E^o′ = ?5 mV vs. ferrocene itself), which shifts towards more positive potentials upon protonation with HCl.     

Preparation and in vitro apatite-forming ability of hydroxyapatite and β-wollastonite composite materials

This paper provides a one-step method of preparation of the ceramic powders, containing various amounts of hydroxyapatite (HA) and β-wollastonite (WT), based on the salt coprecipitation and subsequent thermal treatment of the synthesis products at 1000?°C. Aqueous solutions of Ca(OH)₂, H₃PO₄ and Na₂SiO₃ were used as precursors of Ca₁₀(PO₄)₆(OH)₂ and β-CaSiO₃, as a minimal amount of by-product is formed during such an interaction of reagents. Variation of the concentration of the initial reagents allows the preparation of ceramic powders containing from 0 to 100?wt% of apatite. All composites were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), laser diffraction analysis and an adsorption method (BET). Degradability of composite powders was analyzed in the Tris-HCl buffer solution. The apatite-forming ability of synthetic composites was investigated by soaking composite ceramics in a simulated body fluid (SBF). The results that were obtained reveal an increase in the dissolution rate of powders with wollastonite addition. Soaking of the composite ceramics in SBF leads to the formation of a bone-like apatite spherical particle layer on their surfaces, which become thicker while the content of β-СаSiO₃ in the samples increases.     

Preparation and characterisation of bioactive hydroxyapatite–silica composite nanopowders via sol–gel method for medical applications

Abstract

Abstract

This study focuses on preparation and characterisation of hydroxyapatite–silica composite nanopowders with different contents of silica. Hydroxyapatite–silica composite nanopowders with 10, 20, 30 and 40?wt‐% silica were prepared using a sol–gel method at 600°C with phosphoric pentoxide and calcium nitrate tetrahydrate as the source of hydroxyapatite, also tetraethylorthosilicate and methyltriethoxisilane as the source of silica. XRD, FTIR, SEM, EDAX and TEM techniques were used for characterisation and evaluation of the phase composition, crystallinity, crystallite size, functional groups, morphology and composition of the products. Dissolution behaviour of the products was evaluated at predetermined time periods by an atomic absorption spectrometer and a pH meter. Results indicated the presence of nanocrystalline hydroxyapatite phase and amorphous silica nanoparticles in composite nanopowders. Also, by increasing the content of silica in composite nanopowders, the crystallite size and crystallinity of hydroxyapatite phase decreased and the Ca ion release rate changed.     

Synthesis and characterisation of gelatin–nano hydroxyapatite composite scaffolds for bone tissue engineering

Abstract

Gelatin–hydroxyapatite (HAp) nanocomposites have been prepared by particulate leaching technique using glutaraldehyde (GTA) as cross-linking agent for polymer. The porosity in the scaffolds was controlled using sodium chloride as porogen agent. Microstructural investigation by scanning electron microscopy (SEM), revealed the formation of a well interconnected porous scaffold with pore size in the range of 100–200 μm. X-ray diffraction and Fourier transform infrared spectroscopy were used to confirm the formation of crystalline HAp as well the presence of both constituents in the composite samples. The bioactivity of the samples was evaluated by conducting MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay and cell adhesion tests. The results suggest that the use of GTA in excess of 0˙25% can be detrimental to cell survival. Cell attachment on the nanocomposite scaffold was verified by microscopic analysis.     

Fabrication of hydroxyapatite blended cyclic type polylactic acid and poly (ε-caprolactone) tissue engineering scaffold

The ultimate goal of tissue engineering serves to repair, restore damaged tissue or organ due to accident or disease. In this research, we are aimed at investigating the feasibility of processing cyclic type polylactic acid (PDLLA)/poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) biomaterial into tissue engineering scaffold (TES) with variable mechanical properties, well interconnected pore architecture, and controlled hydrophilicity. For this, an in-house built bone scaffold 3D printing (BS3P) system was applied to two biomaterials, namely PDLLA-PCL and HA-PCL. These two biomaterials were produced by optimizing the robotic control system. Morphological investigation by scanning electron microscope (SEM) revealed both TES formed by new materials able to show honeycomb-like architectures, excellent fusion at the filament junctions, high uniformity, complete interconnectivity, and controlled channel characteristics of the TES. Compression tests align with the typical behavior of a porous material undergoing deformation. In vitro cell culture study and confocal laser microscopy (CLM) showed enhanced cell adhesion, proliferation, and extracellular matrix (ECM) formation. The results demonstrated the eligibility of the BS3P system to produce TES, and the suitability of the new biomaterial scaffolds in enhancing cell biocompatibility.     

Preparation，properties and applications of hydroxyapatite/synthetic polymer composites

随着生物医用材料的需求量日趋增大,磷灰石与人工合成高分子的复合材料成为组织修复和替代材料的研究热点。以不同单体分类,综述了磷灰石与合成的非降解高分子、可降解高分子复合材料的研究进展;对羟基磷灰石/合成高分子复合材料的制备方法、性能及其应用等方面进行研究,并对此复合材料存在的问题和发展前景进行讨论。说明从分子水平设计出具有良好力学性能、生物活性和生物相容性的医学材料,具有十分重要的意义。     

Preparation and characterisation of diopside-based glass–ceramic foams

Foaming and crystallisation behaviours of compacted glass powders based on a diopside glass–ceramic composition were investigated using the sintering route. The foaming agent was 2 wt.% SiC particles. The effect of PbO on the foaming ability of glasses was investigated. The results showed that the addition of PbO not only improved the foaming ability, by improving the wettability of the glass–SiC particles but also increased the crystallisation temperature and widened the temperature interval between the dilatometric softening point and the onset of crystallisation. The glass–SiC wetting angle was decreased from 85° for the lead-free glass, to 55° for the glass that contains 15 wt.% PbO.     

Mechanosynthesis of hydroxyapatite–ferrite composite nanopowder

In the present work, an investigation of the mechanosynthesis of calcium hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) from a mixture of calcium oxide (СаО) and ammonium hydrophosphate ((NH₄)₂HPO₄) and mechanotreatment of HA in a planetary mill with the use of steel drums and milling body has been performed. The obtained results have shown that the mechanosynthesis of crystalline nanodisperse HA proceeds through the stage of formation of an amorphous material. The temperature treatment of HA powders at 1000 °C has enabled us to establish the influence of the treatment time on the phase composition of the powders and establish the following sequence of phase transformations: Ca₁₀(PO₄)₆(OH)₂→β-Ca₃(PO₄)₂ (t_milling~2 h), β-Ca₃(PO₄)₂→α-Ca₃(PO₄)₂ (t_milling~5 h), β-,α-Ca₃(PO₄)₂→Ca₁₀(PO₄)₆(OH)₂ (t_milling~7 h).The mechanosynthesis and mechanotreatment of hydroxyapatite in steel drums with steel balls is accompanied by the contamination of hydroxyapatite by their wear debris (iron + manganese). A large part of oxidized iron forms superparamagnetic inclusions distributed in HA powder. A small part of Fe³⁺ and Mn²⁺ ions from the steel wear debris enters into the hydroxyapatite lattice, substituting Ca²⁺ ions. As a result, a nanocomposite powder consisting of hydroxyapatite, alloyed by Fe³⁺ and Mn²⁺ ions and ferrite inclusions forms. The phase composition of HA powders, the degree of their alloying by Fe³⁺ and Mn²⁺ ions, and the content of ferrite inclusions can be controlled by changing the time of mechanotreatment.     

Preparation and characterisation of titania-supported vanadium–phosphorus oxide catalysts

A series of vanadium–phosphorus oxides (mainly with V P ) supported on pigmentary anatase (10 m² g^-1) has been prepared using aqueous NH₄VO₃ and (NH₄)H₂PO₄ solutions, with loadings up to 11.3 wt%, equivalent to about 12.7 monolayers. Characterisation by X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction suggests that the main phase present at loadings below about 10 wt% is an amorphous V–P oxide which exists chiefly as blocks of disordered material. The presence of small amounts of crystalline -VOPO₄ and of V₂O₅ is indicated at the highest loadings, especially when and V P ratios are used. The two materials having the lowest loadings are active for methanol oxidation at 473–533 K, and show high selectivity to formaldehyde. This revised version was published online in June 2006 with corrections to the Cover Date.     

Scaffolds of polylactic acid/hydroxyapatite coated by plasma with polypyrrole-iodine for the generation of neo-tissue–bone in vivo: Study in rabbit

This paper presents the study scaffolds of polylactic acid (PLA) and hydroxyapatite (HA) processed by electrospinning and covered with polypyrrole with iodine (PPy-I) synthetized by plasma polymerization. Two kinds of samples were prepared: PLA/HA and PLA/HA/PPy-I, each with two different HA concentrations (18.1 and 35.7%). 7-day in vitro test with osteoblasts of autologous mesenchymal stem cells was performed. In vivo test was done in the back of a rabbit for 30 days. After extraction, cell viability, immunohistochemistry, histological, and tension tests were performed. Scaffolds PLA/HA (35.7%)/PPy-I showed higher cell viability. Tension test showed better integration in high HA samples.     

Preparation of ω-hydroxynonanoic acid and its ester derivatives

Methyl ricinoleate was ozonized in methanol or in acetic acid and the intermediate hydroperoxides were reduced electrochemically on Pb-cathode to give 9-hydroxynonanoic acid 1 in high yields. The acid 1 was also prepared by direct castor oil ozonolysis in methanol followed by sodium borohydride reduction of the intermediate hydroperoxides. The cost of the electricity for the electroreduction was at least 30 times lower as compared with sodium borohydride consumption. 9-Hydroxynonanoic acid was then transformed to alkyl 9-acetoxynonanoates 3a–3d, for which ¹H nuclear magnetic reasonance, mass, and infrared spectra are given. Esterification of the hydroxy acid 1 with boric acid and pyrolysis of the resultant orthoborates produced 8-nonenoic acid 4 in a 45% yield. Reaction of 4 with lower aliphatic alcohols in presence of Amberlyst 15 produced alkyl 8-noneates 5a–5d along with some amounts of a cis/trans mixture of alkyl 7-noneates.     

Effect of phosphorus–nitrogen compound on flame retardancy and mechanical properties of polylactic acid

A phosphorus-nitrogen flame retardant (PN) was synthesized by using cytosine and diphenylphosphinic chloride. The flame retardancy and thermal stability of polylactic acid (PLA)/PN composites were investigated by the UL-94 vertical burning test, limited oxygen index (LOI), cone calorimeter test, and thermogravimetric analysis. The PN performs efficiently on improving the flame retardancy of PLA. The PLA composite achieves the UL-94 V-0 rating and its LOI increases to 30.4 vol% by adding 0.5 wt% PN. The flame retardant mechanism analysis showed that PN catalyzes the degradation of PLA to improve the flame retardancy by melting-away mode. Meanwhile PN reduces the release of flammable gasses during thermal degradation of PLA by promoting the transesterification of PLA, which is helpful for extinguishing flame. Moreover, triglycidyl isocyanurate (TGIC) was used as a micro-crosslinking agent to reduce the loss of mechanical properties of PLA/PN composites caused by degradation. Adding 0.1 wt% TGIC and 1.0 wt% PN into PLA, the tensile strength and elongation at break of PLA/PN are increased to the same level as that of PLA. Therefore, PLA with excellent comprehensive performance can be obtained.     

Preparation and characterization of amphoteric cellulose–montmorillonite composite beads with a controllable porous structure

Conventional amphoteric and porous materials are often synthetic and polymer based; this tends to raise environmental concerns because of their poor biodegradability. To address this issue, novel natural-polymer- or amphoteric-modified cellulose and MOt (ACeOMt) composite beads with a typical mesoporous structure were developed in this study. These green-based porous beads, consisting of regenerated bagasse cellulose and oxalic acid modified montmorillonite (OMt), were successfully prepared by a facile coagulation method with fine calcium carbonate as a pore-forming agent. The beads with the best sphericity were obtained at a 1:1 weight ratio of cellulose to OMt. Scanning electron microscopy observation showed that ACeOMt possessed a smooth surface with abundant macropores. X-ray diffraction and thermogravimetric analysis characterizations demonstrated the success of the modification of montmorillonite and cellulose. The results of Brunauer–Emmett–Teller analysis indicate the presence of a typical mesoporous structure in the composite with a relatively high specific surface area. The resulting ACeOMt are expected to be biodegradable, nonhazardous, and applicable for various uses, including adsorption, chromatography, and soil remediation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47941.     

Fabrication and characterization of sol–gel derived hydroxyapatite/zirconia composite nanopowders with various yttria contents

Homogeneous composite nanopowders of hydroxyapatite/30 wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8 mol% Y₂O₃ (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared nanopowders. Analyses of HA–YSZ composite nanopowders showed the successful formation of desirable phases. HA unit cell volume in the composites increased as a result of ion exchange of calcium and zirconium between HA and zirconia. Results revealed the formation of HA particles with irregular morphology (40–80 nm) and spherical yttria-stabilized zirconia particles (20–30 nm). Segregation of yttrium ions at the grain boundaries of ZrO₂ particles retarded the grain growth of zirconia particles and the presence of ZrO₂ nanoparticles among the hydroxyapatite particles resulted in grain growth inhibition of HA particles. This process can be used to synthesize HA–YSZ composite nanopowders with improved properties, which are much needed for hard tissue repair and biomedical applications.     

Preparation and properties of DNA/PLLA,whey protein/PLLA and collagen/PLLA composites

The poor flexibility, low toughness and thermal stability have restricted the applications of degradable poly(lactic acid) bioplastic. The introduction of deoxyribonucleic acid, whey protein or collagen with helical structures, which include numerous intermolecular hydrogen bonds, can produce changes in mechanical and thermal properties of poly(lactic acid) materials. Due to the presence of more –C?=?O and –NH groups with strong hydratability, different composites exhibited a higher heat resistance compared with the neat poly(l-lactic acid). Moreover, for collagen/poly(l-lactic acid) composites, the tensile strength and elongation at break were increased by 88.6 and 154.9% compared with the neat poly(l-lactic acid), respectively. The results provide a basis for the design of novel poly(lactic acid)-based composites and can expand the application areas of materials, including plastic films, taker-bags, textiles and so on.     

Rheological characterisation of hydroxyapatite filled polyethylene composites. Part 1 – Shear and extensional behaviour

Abstract

The shear and extensional properties of injection moulding grade hydroxyapatite–polyethylene composites developed for orthopaedic applications have been studied. The composite was prepared without processing aids owing to concerns over the potential biological responses to such additives. The composite containing 20 vol.-% hydroxyapatite filler showed typical pseudoplastic behaviour. However, that containing 40 vol.-% hydroxyapatite filler tended to exhibit yield. The Maron–Pierce equation was found to be useful in predicting the viscosities of the composite systems. The activation energy of the composite and the unfilled polymer were equal, indicating that the 20 vol.-% system exhibits the same flow mechanism as the unfilled polymer. A qualitative assessment of extensional properties was made following Cogswell's method. The extensional stress of the unfilled polymer decreases with increasing temperature whereas the composites behave in a complex manner. For all the systems the Trouton ratios tend to increase with apparent shear rates. The Trouton ratio also indicates that at higher temperatures the flow of these composites is dominated by extensional properties.     

Preparation of biphasic hydroxyapatite/ β-tricalcium phosphate foam using the replication technique

Biphasic hydroxyapatite/β-tricalcium phosphate foams were prepared using the replication technique starting from a precipitated hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂: HAP) powder, and sodium glycerophosphate (GP). The effect of the grinding time, solid loading, dispersant amount, and etching, replication, and sintering processes were investigated. The SEM, OEM and FTIR analyses proved that the surface of the polyurethane template must be treated with NaOH solution to make it more hydrophilic prior to the coating process. With a solid loading of 40 wt-%, the slurries prepared from the precipitated hydroxyapatite presented a shear thinning behavior, which was useful for the coating process. The SEM analysis of the foams showed that the optimum number of coating layers to obtain foam with an identical structure with the template was limited to three. The use of GP and the optimized preparation parameters helped to decrease the consolidation temperature of the ceramic foams to 1000 °C. The XRD and FTIR analyses of the prepared foams showed that the thermal treatment of the GP and the HAP mixture led to a partial decomposition of the HAP to tricalcium phosphate. The fitting of the XRD patterns and the obtained lattice parameters proved that the decomposition was accompanied by the insertion of sodium from GP toward the lattice of tricalcium phosphate and the formation of Na-β-tricalcium. The results of the SEM analysis, the pore size distribution and the mechanical strength showed that the presence of the Na-β-tricalcium reduced the pore size distribution from 500-2700 to 100–1700 μm, decreased slightly the total porosity from 80 vol-% to 70 vol-%; and improved the mechanical strength of the obtained foam from 1.56 MPa to 2.60 MPa.     

Preparation and corrosion resistance of cordierite–spodumene composite ceramics using zircon as a modifying agent

To prolong the service life of cordierite–spodumene composite ceramics applied to the solar heat transmission pipeline, the zircon modifier was introduced to improve the corrosion resistance of the ceramics. The effects of zircon on the density, bending strength, crystalline phase, microstructure and chemical stability were studied. The results showed that the sintering temperature range of the composite ceramics was broadened to 40–60?°C with the introduction of 5–15?wt% zircon. Moreover, the mechanical strength and corrosion resistance of the ceramic materials were improved with the zircon introduction. In particular, sample C3 containing 15?wt% of zircon and sintered at 1360?°C exhibited the best performance, which had the 0.03% Wa, 0.07% Pa, 2.34?g?cm^?3 Db and 100.17?MPa bending strength. After acid and alkali corrosion, the water absorption was still less than 0.5% and the strength loss rate decreased to less than 5.3%. The XRD and SEM analyses demonstrated that the ZrSiO₄ grains dispersed at the grain boundaries could enhance the mechanical properties. Furthermore, the existence of the Zr⁴⁺ ions not only reduced the cationic solubility of the glassy phases but also led to a reaction with OH^? to form Zr(OH)₄ on the surfaces. This improved the corrosion resistance of the composite ceramics and endowed it with a high residual strength after the acid and alkali corrosion.