Synthesis of multifunctional macroporous-mesoporous TiO<Subscript>2</Subscript>-bioglasses for bone tissue engineering

Hierarchical porous TiO₂-bioglasses (TiO₂-BGs) with the macropore with the size of 30–50 μm and the mesopore with the diameter of 4.4–5.6 nm have been synthesized through the evaporation-induced self-assembly method. The corn stalks were used as the macroporous template and P123 as the mesoporous template in the process. The chemical and physical properties of the hierarchical porous TiO₂-BGs before and after immersion in simulated fluid (SBF) were evaluated by X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, nitrogen adsorption–desorption, and Energy dispersive spectrometer. The effect of TiO₂ content on the formation of surface hydroxyapatite and drug release profiles of the fabricated TiO₂-BGs in SBF were investigated in detail. It was found that macroporous-mesoporous TiO₂-bioglasses (MM TiO₂-BGs) exhibited a good ability of surface hydroxyapatite formation comparing with macroporous-mesoporous bioglasses. It took only 3 h for the MM TiO₂-BGs to be covered with the hydroxyapatite layer. It can be ascribed to the present of Ti–OH which may improve the spontaneous growth of apatite by consuming the calcium and phosphate ions from SBF. Additionally, MM TiO₂-BGs also showed good drug sustained release profiles. Therefore, the multifunctional MM TiO₂-BGs reported here could be a good candidate for application in bone tissue engineering.     

Bioactive sol–gel scaffolds with dual porosity for tissue engineering

Scaffolds containing dual porosity at the nano and macroscale appear to exhibit improved performance in terms of crystallization of hydroxycarbonate apatite plus cell adhesion and proliferation, as well as vascularization. The aim of the present work is to develop a novel, simple sol–gel process for the preparation of silica-based bioactive porous bone tissue scaffold, with a pore structure consisting of interconnected pores of both 100’s of micrometers and 10’s of nanometers in size, optimized for enhanced bone regeneration performance. SiO₂–CaO and SiO₂–CaO–P₂O₅ porous glass monoliths have been prepared with a dual pore structure including pores of both ~50–200 micrometers and a few to 10’s of nanometers in size, based on polymerization-induced phase separation together with the sol-gel transition, by adding a water soluble polymer to the precursor sol. The nanopore (~5–40 nm) structure of such macroporous gel skeletons was tailored by solvent exchange, followed by heat treatment at 600–700 °C. The overall pore structure has been studied by Scanning Electron Microscopy (SEM), N₂-adsorption (BET), Mercury intrusion porosimetry and Infrared spectroscopy. The scaffold bioactivity, tested in simulated body fluid, has been demonstrated by means of DRIFTS, SEM and X-ray diffraction measurements.     

Effects of pH on mechanical and morphological studies of silica filled polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposite

Effects of pH on mechanical properties as well as morphological studies of sol–gel derived in situ silica in polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposites are reported. In particular, a range of acid concentrations was investigated. These nanocomposites were prepared by solution casting technique and tetraethoxysilane (TEOS) was used as the silica precursor. The prepared nanocomposites were characterized using tensile test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tensile test indicated that the highest mechanical strength was at 30% TEOS added for the nanocomposite prepared at pH 2.0. At pH 1.0 and 1.5 the maximum tensile strength reading was at 20% TEOS added with value of 24.3 and 24.5 MPa, respectively. SEM and TEM revealed the dispersion of silica particles in the polymer matrix. For nanocomposites prepared at pH 1.0 and 1.5, the silica particles were finely dispersed with the average size of 60 nm until 20% TEOS added. Meanwhile for nanocomposite prepared at pH 2.0, silica particles were homogenously distributed in the polymer matrix with average diameter of 30 nm until 30% TEOS and agglomerated after 30% TEOS loading.     

Synthesis, characterization, and electrochemical properties of self-assembled leaf-like CuO nanostructures

A simple hydrothermal process was used to synthesize the assembled leaf-like copper oxide (CuO) from copper hydroxide and urea in aqueous solution. The field emission scanning electron microscopy revealed that the individual CuO leaf-like nanostructure has a dimension of about 0.5–1.5 μm in length, 50–70 nm in thickness, and 80–110 nm in width, respectively. These CuO nanostructures were structurally characterized by X-ray diffraction and Raman spectroscopy, which showed that the CuO nanostructures prepared from the hydrothermal process have high crystalline properties with a monoclinic structure. X-ray photoelectron spectroscopy studies confirmed that the as-prepared sample is composed of CuO, which is consistent with X-ray diffraction patterns. The CuO nanostructures were used as electrode materials for lithium-ion batteries, demonstrating electrochemical properties of a high initial discharge capacity of approximately 1,028 mAh/g along with good cycle stability.     

Nano/macroporous monolithic scaffolds prepared by the sol–gel method

Development of optimal scaffolds for bone tissue engineering and regeneration is still a challenge, since many materials and structures have been proposed but few have reached clinical expectations. This work reports on the preparation and characterization of SiO₂-CaO and SiO₂-CaO-P₂O₅ sol–gel derived monoliths, with potential application as glass scaffolds for bone regeneration, exhibiting a nano/macro trimodal pore size distribution, including pores of ~100’s of micrometers (μm), several microns and just a few nanometers (nm) in size. Interconnected macropores (~20–200 μm) have been obtained in the present work by polymerization-induced spinodal phase separation along with the sol–gel transition, when a water soluble polymer [poly(ethylene oxide)] was added to the sol–gel solution; the several-micron pores are spherical and isolated and might be the result of secondary phase separation by nucleation-growth mechanism; the interconnected nanopore (~5–25 nm) structure of the macroporous gel skeleton, on the other hand, was tailored by solvent exchange procedures. The morphological and textural characterization of these materials was performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray ultra microscopy (XuM), nitrogen adsorption and mercury intrusion porosimetry. The factors affecting the porosity exhibited by the scaffolds, such as glass composition and solvent exchange conditions, have been assessed.

Preparation and modification of collagen-based porous scaffold for tissue engineering

In the effort to generate cartilage tissues using mesenchymal stem cells, porous scaffolds with prescribed biomechanical properties were prepared. Scaffolds with interconnected pores were prepared via lyophilisation of frozen hydrogels made from collagen modified with chitosan nanofibres, hyaluronic acid, copolymers based on poly(ethylene glycol) (PEG), poly(lactic-co-glycolic acid) (PLGA), and itaconic acid (ITA), and hydroxyapatite nanoparticles. The modified collagen compositions were cross-linked using N-(3-dimethylamino propyl)-N′-ethylcarbodiimide hydrochloride (EDC) combined with N-hydroxysuccinimide (NHS) in water solution. Basic physicochemical and mechanical properties were measured and an attempt to relate these properties to the molecular and supermolecular structure of the modified collagen compositions was carried out. Scaffolds containing hydrophilic chitosan nanofibres showed the highest swelling ratio (SR = 20–25) of all the materials investigated, while collagen modified with an amphiphilic PLGA-PEG-PLGA copolymer or functionalised with ITA exhibited the lowest swelling ratio (SR = 5–8). The best resistance to hydrolytic degradation was obtained for hydroxyapatite containing scaffolds. On the other hand, the fastest degradation rate was observed for synthetic copolymer-containing scaffolds. The results showed that the addition of hydroxyapatite or hyaluronic acid to the collagen matrix increases the rigidity in comparison to the collagen-chitosan scaffold. Collagen scaffold modified with hyaluronic acid presented reduced deformation at break while the presence of hydroxypatatite enhanced the scaffold deformation under tensile loading. The tensile elastic modulus of chitosan nanofibre collagen scaffold was the lowest but closest to the articular cartilage; however, the strength and deformation to failure increased up to 200 %. Presented at the 1st Bratislava Young Polymer Scientists Workshop, Bratislava, 20–23 August 2007.     

Surfactant assisted preparation and characterization of carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger

Carboxymethyl cellulose Sn(IV) phosphate composite nano-rod like cation exchanger with diameter in the range of 20–40 nm, length in the range of 100–150 μm and particle size in the range of 21–38 nm have been successfully prepared by surfactant assisted sol–gel method. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, fourier transform infra red spectroscopy and thermogravimetric analysis-differential thermal analysis studies were carried out to study the structure and morphology of this composite nano-rod like cation exchanger. Freundlich adsorption isotherm is well fitted for the adsorption of pyridine on the surface of this composite nano-rod like cation exchanger. The thermodynamic parameters such as Freundlich constant, thermodynamic equilibrium constant (K ₀), standard free energy changes (ΔG ⁰), standard enthalpy changes (ΔH ⁰) and standard entropy changes (ΔS ⁰) have been evaluated. These parameters indicated that the adsorption of pyridine on the surface of composite nano-rod like cation exchanger was feasible, spontaneous and exothermic in nature which suggests for the potential application of pyridine removal from water.     

The investigation of some physical properties and microstructure of Zn-doped hydroxyapatite bioceramics prepared by sol–gel method

In this study, the effect of Zn-dopant on the physical properties and microstructure of hydroxyapatite (HAP) bioceramics was investigated. The average crystallite size, phase composition and degree of crystallization of the pure hydroxyapatite and Zn-doped hydroxyapatite bioceramic samples prepared by sol–gel method were determined by X-ray diffraction method. It was seen that all the bioceramic samples were composed of the nanoparticles (29–46 nm). Fourier transform infrared spectroscopy was used to determine the functional groups in the samples. The dielectric properties of the bioceramics were investigated by dielectric impedance spectroscopy method, and the surface morphologies of them were analyzed using scanning electron microscopy technique. When the densities of the samples were measured by Archimedes method, it was seen that the densities of the samples increased with the increase of the molar ratio of Zn. The crystallization degree for all the samples dramatically decreased with the increasing content of the Zn dopant. With the increase of Zn to HAP, a change was observed in the degree of the crystallization, phase compositions, dielectric properties and microstructures of the samples.     

PVA-Based Sol–Gel Synthesis and Characterization of CdO–ZnO Nanocomposite

CdO–ZnO nanocomposite was fabricated by a sol–gel pyrrolysis method based on the poly vinyl alcohol (PVA) polymeric network. The prepared nanocomposite was carefully characterized using scanning electron microscopy, X-Ray dispersive energy analysis, ICP-atomic emission spectroscopy, X-Ray diffraction, transmission electron microscopy and UV–visible spectroscopy. The structure, composition, and morphology of this composite depend on a number of aspects: the amounts of cadmium salt, zinc salt, and PVA in the initial solution, the solvent composition, and the pyrrolysis temperature. The obtained results showed that the nanocomposite had excellent linear nanoclusters created from nanograins. Each nanograin was made of a CdO core, completely covered by ZnO layers. Total diameter of each nanograin was 70–90 nm.     

Effect of pH and temperature on the morphology and phases of co-precipitated hydroxyapatite

This paper reports a high-yield process to fabricate biomimetic hydroxyapatite nano-particles or nano-plates. Hydroxyapatite is obtained by simultaneous dripping of calcium chloride and ammonium hydrogen phosphate solutions into a reaction vessel. Reactions were carried out under various pH and temperature conditions. The morphology and phase composition of the precipitates were investigated using scanning electron microscope and X-ray diffraction. The analyses showed that large plates of calcium hydrophosphate are formed at neutral or acidic pH condition. Nanoparticles of hydroxyapatite were obtained in precipitates prepared at pH 9–11. Hydroxyapatite plates akin to seashell nacre were obtained at 40 °C and pH 9. This material holds promise to improve the strength of hydroxyapatite containing composites for bone implant or bone cement used in orthopaedic surgeries. The thermodynamics of the crystal growth under these conditions was discussed. An assembly mechanism of the hydroxyapatite plates was proposed according to the nanostructure observations.     

Preparation and performance of porous titania with a trimodal pore system as anode of lithium ion battery

A porous titania has been prepared by using polystyrene spheres and tri-block copolymer ((EO)₂₀–(PO)₇₀–(EO)₂₀, P123) as templates, and its structure, composition, and performance as anode of lithium ion battery are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and galvanostatic charge/discharge test. The results from SEM and TEM indicate that the prepared porous titania has a trimodal pore system, in which the pores are in ordered arrangement and interconnected with the same pore diameter and uniform wall thickness. The charge/discharge tests show that the battery using the prepared porous titania as anode exhibits good rate capacity and cycle stability.     

Synthesis of terbium doped calcium phosphate nanocrystalline powders by citric acid sol–gel combustion method

Terbium doped calcium phosphate (Tb-doped CaP) nanocrystalline powders were synthesized by the citric acid sol–gel combustion method. The phase composition, morphology and luminescent property of Tb-doped CaP nanocrystalline powders were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fluorescence spectrophotometer and fluorescence microscopy. At 700 °C, Tb-doped CaP nanocrystalline powders are composed of HAP (main phase) and β-TCP (minor phase) with Tb doping content of 0.5–4%. SEM and TEM observations show that the 4% Tb-doped CaP nanocrystalline powders are about 50–150 nm spherical particles. The 4% Tb-doped CaP nanocrystalline powders exhibit the strongest emission at 548 nm (λ_excitation = 240 nm) and show strong green fluorescence under fluorescence microscopy.     

块状壳聚糖多孔支架内交替浸渍沉积磷灰石层

在聚合物支架内沉积羟基磷灰石涂层有望提高支架的生物活性和骨传导性. 本研究采用交替浸渍沉积法, 以块状壳聚糖(Cs)三维多孔支架为沉积模板, 在氯化钙溶液和磷酸氢二钠溶液中交替浸渍, 沉积了羟基磷灰石(HA)涂层. 应用XRD、FT-IR、SEM、孔隙率测试、焙烧法和压缩实验对沉积前后支架的组成、形貌、孔隙率、无机物沉积量以及压缩强度进行了表征. 研究结果表明, 支架上沉积物为低结晶度的碳酸羟基磷灰石, 沿c轴择优生长, 与天然骨中磷灰石类似. 扫描电镜照片显示, 磷灰石在支架孔壁上的沉积量呈梯度分布, 外部沉积量多于内部, 靠近支架表面孔隙部分堵塞, 但内部仍保持连通的孔隙结构. 经6次交替浸渍处理的支架, 孔隙率为94.0%, 羟基磷灰石沉积量达到总质量的13.5%, 压缩强度则由0.055 MPa提高到0.109 MPa.     

Facile fabrication of cerium niobate nano-crystalline fibers by electrospinning technology

In this study, one-dimensional (1D) cerium niobate nano-crystalline fibers were first prepared by a facile sol–gel and electrospinning process, followed by heat treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) were used to characterize the samples. It can be seen from SEM images that the as-prepared xerogel samples and those annealed at 900 °C presented uniform fibrous morphology, with the diameter of 100–300 nm and length of several centimeters. The XRD and FT-IR results showed that cerium niobate samples had well-crystallized phase of CeNbO_4.25 with the crystallite size of about 28.6 nm at a heat treatment temperature of 900 °C, which can also be validated with the TEM image. The AC impedance of annealed disks made from the CeNbO_4.25 nano-crystalline fibers has been probed.     

Cellulose II nanoelements prepared from fully mercerized, partially mercerized and regenerated celluloses by 4-acetamido-TEMPO/NaClO/NaClO2 oxidation

A softwood bleached kraft pulp (SBKP) and cotton lint cellulose were fully or partially mercerized, and these along with celluloses and commercially available regenerated cellulose fiber and beads were oxidized by 4-acetamido-TEMPO/NaClO/NaClO₂ at 60 °C and pH 4.8. Weight recovery ratios and carboxylate contents of the oxidized celluloses were 65–80% and 1.8–2.2 mmol g⁻¹, respectively. Transparent and viscous dispersions were obtained by mechanical disintegration of the TEMPO-oxidized celluloses in water. These aqueous dispersions showed birefringence between cross-polarizers, indicating that mostly individualized cellulose nanoelements dispersed in water were obtained by these procedures. Transmission electron microscopy observation showed that the cellulose nanoelements prepared from mercerized SBKP, repeatedly mercerized SBKP, mercerized cotton lint cellulose, regenerated cellulose beads and 18% NaOH-treated SBKP, i.e. partially mercerized SBKP, had similar morphologies and sizes, 4–12 nm in width and 100–200 nm in length. The 18% NaOH-treated SBKP was converted to cellulose nanoelements consisting of both celluloses I and II.     

Preparation of mesoporous hydroxyapatite films used as biomaterials via sol–gel technology

The mesoporous hydroxyapatite films (MHFs) have been developed on glass slides by sol–gel dip-coating technology using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent and the effects of pH value and calcination temperatures on the surface morphology and the mesostructure have been discussed. The phase composition, surface morphology, mesostructure and surface wettability were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, N₂ adsorption–desorption isotherms and water contact angle analyzer, respectively. The continuous thin films consisted of mesoporous hydroxyapatite particles (~50 nm) with mesopores (~2 nm) within the particles have been obtained after being prepared in the condition of concentration of CTAB 0.09 M, pH of sol 3.0, reaction temperature 60 °C and calcination temperature 550 °C. In vitro cell culture, the mesoporous films, which possessed favorable surface wettability resulting from the special pore structure, have exhibited a high degree of MC3T3-E1 cell attachment and spreading, suggesting a better bioactivity. Therefore, the MHFs can be expected to have potential application for decreasing the ion release of implant and improving the bioactivity as a coating on material surface.     

NiTiO<Subscript>3</Subscript> nanoparticles encapsulated with SiO<Subscript>2</Subscript> prepared by sol–gel method

NiTiO₃ (NTO) nanoparticles encapsulated with SiO₂ were prepared by the sol–gel method resulting on core-shell structure. Changes on isoelectric point as a function of silica were evaluated by means of zeta potential. The NTO nanoparticles heat treated at 600°C were characterized by X-ray diffraction, transmission electron microscopy (TEM) and energy dispersive X-ray analysis. TEM observations showed that the mean size of NTO is in the range of 2.5–42.5 nm while the thickness of SiO₂ shell attained 1.5–3.5 nm approximately.     

High optical transparency and low dielectric constant of novel organosoluble poly(ether ketone amide)s derived from an unsymmetrical diamine containing trifluoromethyl and methyl pendant groups

A series of novel fluorinated poly(ether ketone amide)s (PEKAs) were prepared from an unsymmetrical aromatic diamine, (4′-(4″-amino-2″-trifluoromethylphenoxy)-3′,5′-dimethylphenyl)(4-aminophenyl)-methanone (1), with various aromatic dicarboxylic acids using the phosphorylation polycondensation technique. The PEKAs had inherent viscosities ranging from 0.43 to 0.65 dl/g. All the fluorinated PEKAs could be soluble in many polar organic solvents such as N-methyl-2-pyrrolidinone (NMP), N,N′-dimethylacetamide (DMAc), N,N′-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). Flexible and tough polymer films could be prepared by casting from DMAc solvent. The PEKA films exhibited high optical transparency with a cutoff wavelength of 354–365 nm and good mechanical properties with tensile strengths of 78–98 MPa and elongations at break of 11.5–18.5%. They showed glass-transition temperatures in the range of 288−323 °C and the onset decomposition temperatures in the range of 450−461 °C in nitrogen atmosphere. Meanwhile, the PEKA films possessed low dielectric constants of 1.98–2.71 at 1 MHz and low moisture absorption (<2%). Due to their properties, the fluorinated PEKAs could be considered as photoelectric and microelectronic materials.     

Catalytic activity and stability toward methanol oxidation of PtRu/CNTs prepared by adsorption in aqueous solution and reduction in ethylene glycol

In this paper, we reported an improved process for the preparation of PtRu/CNTs, which involves the adsorption of Pt and Ru ions on CNTs in aqueous solution and the reduction of the adsorbed Pt and Ru ions on CNTs in ethylene glycol. The surface morphology, structure, and compositions of the prepared catalyst were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive spectrometer. TEM observation showed that the particles size of the prepared PtRu alloy was in the range of 2–5 nm, XRD patterns confirmed a face-centered cubic crystal structure. The activity and stability of the prepared catalyst toward methanol oxidation were studied in 0.5 M H₂SO₄ + 1 M CH₃OH solution by cyclic voltammetry, chronoamperometry, and chronopotentiometry. The electrochemical results showed that the prepared catalyst exhibited higher activity and stability toward methanol oxidation than commercial PtRu/C with the same loading amount of Pt and Ru.     

In situ mineralization of hydroxyapatite on poly(vinyl alcohol) monolithic scaffolds for tissue engineering

A poly(vinyl alcohol) (PVA)/hydroxyapatite (HAp) composite monolithic scaffold is prepared via thermally impacted non-solvent induced phase separation method, successively followed by an alternate soaking process. The morphology of the resulting composite monolith is observed by scanning electron microscopy (SEM). The formation of hydroxyapatite is confirmed by X-ray diffraction, SEM in combination with energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The effects of soaking cycle and soaking time upon the formation of hydroxyapatite on the monolith surface are systematically investigated. With the increase of soaking cycle and soaking time, the amount of the formed hydroxyapatite increases. As the soaking cycle increases, the water uptake of the composite monolith decreases. The PVA/HAp composite monolith greatly has a promising application as scaffold of bone tissue engineering.