Preparation and characterization of theophylline loaded chitosan/β-cyclodextrin microspheres

The purpose of this project was to develop sustained release chitosan/β-cyclodextrin microspheres of theophylline (TH) prepared by spray drying method. The effect of several formulation variables on the characteristics of microspheres was studied. The B microspheres had a narrower particle size distribution with the diameter between l and 10 μm. SEM showed spherical microspheres with smooth or slightly wrinkled surfaces. FT-IR spectroscopy revealed that hydrogen bonds were formed between TH and chitosan or β-cyclodextrin. The drug entrapments significantly increased from 13.33 to 35.70% with an increase of the ratio of drug/polymer. The encapsulation efficiencies were from 85.16 to 91.40%. The in vitro release of TH from microspheres was related to the pH of the medium, swelling ability, especially in the ratio of drug/polymer. The B microspheres had a prolonged release pattern with the release rate of 60.20% (pH 6.8) within 8 h.     

Preparation and characterization of fenofibrate-loaded PLA–PEG microspheres

A series of biodegradable block copolymer of poly(lactide)(PLA)/poly(ethylene glycol) (PEG) were prepared by Ring-Opening polymerization of D, L-lactide, using stannous octoate as a catalyst. By nanoprecipitation method, the PLA-PEG can be made into microspheres containing fenofibrate, which is a kind of important cholesterol-lowering drugs. The purpose of this study is to investigate the effect of the copolymer composition on the size, the entrapment and the release behavior of the fenofibrate loaded microspheres. The microspheres can be achieved with small size below 100 nm, better encapsulation efficiencies of more than 55.3% and slower release rates. The release of fenofibrate from microsphere would reach the balance first, when the microsphere prepared by high proportion of hydrophilic PEG block. And the release property of fenofibrate/PLA-PEG microsphere was better than Lipanthyl (a commercial capsule of fenofibrate). It was observed that the composition of PLA-PEG copolymer played a major role in encapsulation efficiency of microspheres and release rates.     

Preparation of alginate–CaCl2 microspheres as resveratrol carriers

Resveratrol-loaded calcium alginate microspheres for prolonged drug release were prepared by ionic gelation of alginate with calcium chloride (CaCl₂). Further, resveratrol-loaded calcium alginate microspheres were developed using two concentrations of alginate (0.5 and 1 % w/v) and CaCl₂ (0.5 and 1 M) and an encapsulator equipped with a 300-μm nozzle. The mean particle size of the microspheres was between 175.52 and 244.03 μm, and an encapsulation efficiency (EE) of over 95 % was observed. FTIR spectroscopy indicated a polyelectrolyte interaction between alginate and CaCl₂; alginate microsphere thermograms were analyzed by differential scanning calorimetry. X-ray diffraction shows the crystalline change of microspheres by cross linking. The release profiles and EE increased depending on the CaCl₂ concentration, and a slow initial burst release was observed on freeze-dried microspheres. These results indicate that resveratrol-loaded calcium alginate microspheres can be used as a potential resveratrol delivery system in the food industry.     

Preparation and characterization of hydroxyapatite/polycaprolactone–chitosan composites

Hydroxyapatite (HA)/polycaprolactone (PCL)–chitosan (CS) composites were prepared by melt-blending. For the composites, the amount of HA was varied from 0% to 30% by weight. The morphology, structure and component of the composites were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The tensile properties were evaluated by tensile test. The bioactivity and degradation property were investigated after immersing in simulated body fluid (SBF) and physiological saline, respectively. The results show that the addition of HA to PCL–CS matrix tends to suppress the crystallization of PCL but improves the hydrophilicity. Adding HA to the composites decreases the tensile strength and elongation at break but increases the tensile modulus. After immersing in SBF for 14 days, the surface of HA/PCL–CS composites are covered by a coating of carbonated hydroxyapatite with low crystallinity, indicating the excellent bioactivity of the composites. Soaking in the physiological saline for 28 days, the molecular weight of PCL decreases while the mass loss of the composites and pH of physiological saline increase to 5.86% and 9.54, respectively, implying a good degradation property of the composites.     

Preparation and characterization of CuCrO2–CeO2 nanofibers by electrospinning method

Journal of Materials Science: Materials in Electronics - In this study, CuCrO2–CeO2 nanofibers were prepared by the electrospinning method and the influences of different concentrations on...     

Preparation and optical properties of iron-modified titanium dioxide obtained by sol–gel method

In this paper twelve TiO₂:Fe powders prepared by sol–gel method were analyzed being into consideration the kind of iron compound applied. As a precursor titanium (IV) isopropoxide (TIPO) was used, while as source of iron Fe(NO₃)₃ or FeCl₃ were tested. Fe doped TiO₂ was obtained using two methods of synthesis, where different amount of iron was added (1, 5 or 10% w/w). The size of obtained TiO₂:Fe particles depends on the iron compound applied and was found in the range 80–300 nm as it was confirmed by SEM technique. TiO₂:Fe particles were additionally investigated by dynamic light scattering (DLS) method. Additionally, for the TiO₂:Fe particles UV–vis absorption and the zeta potential were analyzed. Selected powders were additionally investigated by magnetic force microscopy (MFM) and X-ray diffraction techniques. Photocatalytic ability of Fe doped TiO₂ powders was evaluated by means of cholesteryl hemisuccinate (CHOL) degradation experiment conducted under the 30 min irradiation of simulated solar light.     

Preparation of nanocrystalline tin powders by the γ-radiation method

The γ-radiation method has been successfully used to prepare nanocrystalline tin powders. X-ray powder diffraction reveals that the product is single phase of tin with a tetragonal structure. Electron microscopy shows that the average particle size is about 28 nm. The mechanism of Sn²⁺ ion reduction during γ-irradiation is discussed.     

Preparation of Fe3O4–chitosan nanoparticles used for hyperthermia

The Fe₃O₄–chitosan nanoparticles with core-shell structure have been prepared by crosslinking method. Oleic acid modified Fe₃O₄ nanoparticles were firstly prepared by co-precipitation then chitosan was added to coat on the surface of the Fe₃O₄ nanoparticles by physical absorption. The Fe₃O₄–chitosan nanoparticles were obtained by crosslinking the amino groups on the chitosan using glutaraldehyde. Transmission electron microscopy showed that the Fe₃O₄–chitosan nanoparticles were quasi-spherical with a mean diameter of 10.5 nm. X-ray diffraction pattern and X-ray photoelectron spectra indicated that the magnetic nanoparticles were pure Fe₃O₄ with a cubic inverse spinel structure. The modification using chitosan did not result in a phase change. The binding of chitosan to the Fe₃O₄ nanoparticles was also demonstrated by the measurement of fourier transform infrared spectra and thermogravimetric analysis. Magnetic measurement revealed that the saturation magnetization of the composite nanoparticles was 30.7 emu/g and the nanoparticles were superparamagnetic at room temperature. Furthermore, the inductive heating property of the composite nanoparticles in an alternating current magnetic field was investigated and the results indicated that the heating effect was significant. The Fe₃O₄–chitosan nanoparticles prepared have great potential in hyperthermia.     

Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol–gel method

Uniformly distributed nanoparticles of LiCoO₂ have been synthesized through the simple sol–gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge–discharge cycling performance. The powder calcined at a temperature of 900 °C for 5 h shows pure phase layered LiCoO₂. The results show that the particle size is reduced in presence of surfactant as compared to normal sol–gel method. Also, the sample prepared in presence of surfactant and calcined at 900 °C for 5 h shows the highest initial discharge capacity (106 mAh g^?1) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g^?1.     

Preparation of polycrystalline YAG/alumina composite fibers and YAG fiber by sol–gel method

Polycrystalline yttrium–aluminum garnet, Y₃Al₅O₁₂ (YAG) fiber and α-alumina and YAG matrix composite fiber were prepared by the sol–gel method. α-Alumina and YAG matrix composite fiber with fine and homogeneous microstructure could be successfully fabricated by interpenetrating YAG in alumina matrix and adding α-alumina of seed particles to fibers. Effect of α-alumina seed particles and YAG on crystallization and microstructure of composite fiber were discussed. The size of alumina matrix of the composite fibers heated at 1600°C for 4 h was below 2 μm. The tensile of strength alumina fiber heat-treated at 1500°C was 0.2 GPa, while that of the composite fiber was 1.1 GPa.     

Preparation of NiAl–TiC nanocomposite by mechanical alloying

NiAl–TiC nanocomposite was successfully synthesized via a ball-milled mixture of Ni, Al, Ti, and graphite powders. The structural and morphological evolutions of the powders were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Results show that NiAl–TiC composite was obtained after 6 h of milling. The mean grain sizes of 6 and 10 nm were attained for NiAl and TiC at the end of milling, respectively. An annealing of 3 h milled sample at 600 °C led to the formation of Ni (Al, Ti, C) solid solution. NiAl–TiC nanocomposite that was formed in the 12 h milled sample is stable during an annealing at 600 °C. The mean grain size of NiAl at the 12 h milled powder increased during annealing at 600 °C. Maximum micro hardness value of 870 kg/mm² (8.7 GPa) was acquired from the 12 h milled powder. SEM images and particle size measurement showed that very fine spheroid particles (1 μm) were procured at the end of milling.     

Preparation of highly crystalline mesoporous TiO2 by sol–gel method combined with two-step calcining process

Mesoporous TiO₂ samples, with large specific surface area and high crystallinity, were prepared by a sol–gel method using polyethylene glycol and polyacrylamide (PAM) as composite templates and by two-step calcining process (at 500—700 °C in nitrogen and 500 °C in air). As a comparison, the sample was prepared using same composite templates by one-step calcining process (at 500 °C in air). The samples were characterised by X-ray diffraction, transmission electron microscopy, N₂ adsorption–desorption, and diffuse reflectance UV-visible absorption spectra. The results showed that when the samples were fabricated using two-step calcining process, they exhibited typical mesoporous structure, large specific surface area, and high crystallinity. The properties of samples were studied. The results showed that PAM accelerates gel rate. The crystallinity and specific surface areas of samples were increased by using two-step calcining process. Compared with the sample prepared using one-step calcining process, the visible light absorption of samples synthesised by the two-step calcining process was improved.     

Preparation of porous particles by liquid–liquid interfacial crystallization

Liquid–liquid interfacial crystallization was proposed as a novel method of controlling crystal shape and size of precipitated solute particles. The crystallization was performed at interface forming two separate phases of aqueous solution and organic solvent in the present study, and progressed by increase of supersaturation caused by the slightly mutual diffusion at the liquid–liquid system. This crystallization process is possible to precipitate particles at room and constant temperature without cooling or heating sources. The liquid–liquid interfacial crystallization method was able to carry out in changing the shape of the interface.A spherical shape was made by droplets in the present liquid atomization process. Crystallization started when the droplets of the solution sprayed into the organic liquid. Our research involved producing glycine porous particles by atomizing glycine solution into 1-butanol and other organic solvent with 3-fluid nozzle. The collision between the solutions in compressed air produced the micro-size droplets of glycine solution. In using 1-butanol liquid, the glycine crystallized at the glycine solution/1-butanol interface. The spherical aggregated particles were obtained in this spray granulation process. In addition, the transformation occurred from unstable β-structure to metastable α-structure with changing crystallization condition, and it was found that α- and β-structure of glycine coexist in the obtained particles from observation by X-ray powder diffraction.     

Preparation and characterization of Ba2TiSi2O8 ferroelectric films produced by sol–gel method

Fresnoite (Ba₂TiSi₂O₈, BTS) thin films were grown on polished Si(100) substrates by sol–gel method. The films were characterized using Fourier transform infrared spectroscopy (FTIR), Raman scattering spectroscopy, X-ray diffraction (XRD) and atom force microscopy (AFM). The results reveal that the crystallinity of fresnoite thin films increases and their structures become more compact as post-annealing temperature increases. Combined with XRD data, the strong FTIR peaks and Raman bands assigned to Ti–O and Si–O vibration indicate the formation of fresnoite phase in the films at a temperature of 750 °C. Besides, the AFM observation showed the films have a smooth surface, fine grains and dense structure.     

Preparation and comparative characterization of keratin–chitosan and keratin–gelatin composite scaffolds for tissue engineering applications

We report fabrication of three dimensional scaffolds with well interconnected matrix of high porosity using keratin, chitosan and gelatin for tissue engineering and other biomedical applications. Scaffolds were fabricated using porous Keratin–Gelatin (KG), Keratin–Chitosan (KC) composites. The morphology of both KG and KC was investigated using SEM. The scaffolds showed high porosity with interconnected pores in the range of 20–100 μm. They were further tested by FTIR, DSC, CD, tensile strength measurement, water uptake and swelling behavior. In vitro cell adhesion and cell proliferation tests were carried out to study the biocompatibility behavior and their application as an artificial skin substitute. Both KG and KC composite scaffolds showed similar properties and patterns for cell proliferation. Due to rapid degradation of gelatin in KG, we found that it has limited application as compared to KC scaffold. We conclude that KC scaffold owing to its slow degradation and antibacterial properties would be a better substrate for tissue engineering and other biomedical application.     

Preparation of Li–Al–O films by laser chemical vapor deposition

Li–Al–O films were prepared on AlN substrates by laser chemical vapor deposition at deposition temperatures (T_dep) of 800–1300 K and molar ratios of Li to Al precursors (R_Li/Al) of 0.1–12. Single-phase α-LiAl₅O₈ films having faceted grains with pyramidal and polygonal shapes were obtained at T_dep = 1107–1280 K and R_Li/Al = 0.1–2.9. Single-phase γ-LiAlO₂ films having pyramidal grains were prepared at T_dep = 984–1238 K and R_Li/Al = 0.9–10.6. Under the conditions of T_dep = 923 K and R_Li/Al = 11.4, single-phase β-Li₅AlO₄ films with a fluffy morphology were deposited. The highest deposition rate of Li–Al–O films was 98 μm h⁻¹ with a mixture of γ-LiAlO₂ and β-Li₅AlO₄ at T_dep = 944 K.     

Preparation of Ba–Ti–O films by laser chemical vapor deposition

Ba–Ti–O films were prepared on Pt-coated Si substrate by laser chemical vapor deposition, and their orientations and microstructures were compared. Ba₂TiO₄, BaTiO₃, BaTi₂O₅, Ba₄Ti₁₃O₃₀ and BaTi₄O₉ single-phase films were prepared at Ti to Ba molar ratio from 0.41 to 3.49. The α′-Ba₂TiO₄ film showed (0 1 0) and (0 9 1) co-orientation with elongated, truncated columnar grains. The BaTiO₃ film was composed of triangular and hexagonal grains with slight (1 1 1) orientation. The BaTi₂O₅ film had (0 1 0) orientation and faceted columnar grains. The Ba₄Ti₁₃O₄₀ film showed (1 0 0) and (0 1 2) co-orientation with shellfish-like grains. The BaTi₄O₉ film showed (0 1 0) orientation with slightly rounded faceted columnar grains. The deposition rates of Ba–Ti–O films ranged from 30 to 144 μm h⁻¹.     

Starch–chitosan hydrogels prepared by reductive alkylation cross-linking

Starch-chitosan hydrogels were produced by oxidation of soluble starch to produce polyaldehyde and subsequently cross-linked with chitosan via reductive alkylation. The swelling ratio of starch-chitosan membranes was increased gradually with increasing starch ratio, but it was always lower than the native chitosan. In dry state, starch-chitosan membranes with low starch ratio (0.16, 0.38) showed similar tensile strength values to those of native chitosan while these values decreased with increasing starch ratios (0.73-1.36). Membranes in physiological buffer solution (PBS) gave a tensile modulus between 2.8 and 1.0 MPa, decreasing with increasing starch ratio (0.16-1.36 (Wstarch/Wchitosan)). When the membranes were incubated in PBS only, a moderate weight loss was observed for the first two weeks. Original weights of low starch weight ratio membranes (0-0.38) were at near 85%, while high ratio samples (0.73-1.55) were kept around 70% after three months. However, for the membranes incubated in alpha-amylase solution, very fast weight loss was observed. For low starch ratio membranes (0.16, 0.38, 0.73), the residual original weights were measured to be 11%, 6%, 20%, while for high ratio membranes (1.04 and 1.36) these were 45% and 30%, respectively, after two months of enzyme incubation. Scanning electron microscopy analysis of alpha-amylase degraded membranes exhibited rough surface morphology.     

Preparation of core–shell poly(l-lactic) acid-nanocrystalline apatite hollow microspheres for bone repairing applications

In this paper, hybrid inorganic–organic core–shell hollow microspheres, made of poly(l-lactic acid) (PLLA) and biomimetic nano apatites (HA), were prepared from biodegradable and biocompatible substances, suitable for bone tissue applications. Preparation is started from Pickering emulsification, i.e., solid particle-stabilized emulsions in the absence of any molecular surfactant, where solid particles adsorbed to an oil–water interface. Stable oil-in-water emulsions were produced using biomimetic 20?nm sized HA nanocrystals as particulate emulsifier and a dichloromethane (CH₂Cl₂) solution of PLLA as oil phase. Hybrid hollow PLLA microspheres at three different HA nanocrystals surface coverage, ranging from 10 to 50?μm, were produced. The resulting materials were completely characterized with spectroscopic, calorimetric and microscopic techniques and the cytocompatibility was established by indirect contact tests with both fibroblasts and osteoblasts and direct contact with these latter. They displayed a high level of cytocompatibility and thus represent promising materials for drug delivery systems, cell carriers and scaffolds for regeneration of bone useful in the treatment of orthopaedic, maxillofacial and dental fields.     

Preparation of regenerated silk sericin/silk fibroin blend microparticles by emulsification–diffusion method for controlled release drug delivery

This study reports drug-loaded silk sericin (SS)/silk fibroin (SF) blend microparticles being fabricated by the water-in-oil emulsion solvent diffusion of a SS/SF aqueous blend solution. Blue dextran was used as the water-soluble drug model. The influence of the SS/SF blend ratio on the characteristics and drug release behavior of the blend microparticles was investigated. The blend microparticles were analyzed by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and UV-vis spectroscopy. The blend microparticles were nearly spherical in shape as determined from SEM micrographs. The FTIR and TG results demonstrated that interactions between SS and SF molecules had occurred. The blend microparticles showed very high drug loading efficiency (94–98%) for all blend ratios. The in vitro drug release significantly decreased with decreasing SS blend ratio. The results demonstrated that the SS/SF blend microparticles could be used as biocompatible and biodegradable microparticles for controlled release drug delivery applications.