Papers by Keyword: Microsphere

Abstract: Poly (vinyl alcohol) (PVAL) was a common stabilizing agent used in formulate polymeric drug encapsulated micro-/nanoparticles. In preparing poly (lactic acid) (PLA) micro-/nanoparticles by emulsion and solvent evaporation (ESE) technique, the particle size and distribution have shown dependent on PVAL concentration. The focused of this project was to investigate the PVAL function in relation to significant changes in particle size. These studies were relatively important, as it was the basic studies of material usage in ESE fabricating process. The function of PVAL as, either surfactant that able to reduce interfacial tension or stabilizer to provide steric stability was further investigated by measuring the interfacial tension (IFT) of two liquids and zeta potential of the particles. As PVAL concentration increased, the reduction of IFT was only pronounced at the early stage of PVAL incorporation from 16.02 m N/m (absence of PVAL) to 2.0 m N/m (presence of 1 % PVAL), while zeta potential of particles was gradually decreased from-25 mV to-10.2 mV. As conclusion, the presence of PVAL could reduce the interfacial tension. However, to further stabilize the particle (e.g. reduce size and narrow size distribution) in the fabrication process, the steric stabilization provided by PVAL give more significant advantages.

Abstract: The basic properties of concrete can dramatically improve due to the unique structure of the nanosized particles. Namely, strength, frost resistance, fire resistance, corrosion resistance are increased, density and permeability are reduced; plasticity and water absorption are regulated. Despite of the huge number of advantages of nanomodified concrete, analysis of the use of nanoparticles shows that they are used quite seldom, as it requires a large cash outlay. It is not always profitable to use such additives. This article discusses some additives: magnesium nanoshpinel, microspheres, rice hull ash and metakaolin, astralenes, ferric hydroxide sol, carbon nanotubes, silica fume, nanosilica, MB-01, combined modifiers, based on iron hydroxide sol and silica sol. As well in this article sol-gel method as an additive in concrete is considered. The analysis shows that the use of nanosized particles can reduce a large amount of cement. As an addition, savings of the use are seen in reducing the cost of construction due to the low density with high strength. Accurate material consumption and maximum use of advantages of nanomodified concrete provide great prospects of implementation of this material in construction.

Abstract: Uniform α-alumina microspheres with mean partice size about 5-6 μm were prepared by the catalytic precipitation and calcination process. The spherical hydrated alumina precursor was first synthesized by the precipitation using ammonium aluminum sulfate and urea. During the reaction process, the urea can be decomposed to the mediator urease, which acts as the catalyst to influence the precipitate formation. The as-prepared α-alumina microspheres exhibit a very good shaping ability and the green body shaped by the dry-press process has a low linear shrinkage rate 5.8% at the sintering process.

Abstract: In this research, the microspheres of poly (99-dihexylfluorene) were fabricated with dichloromethane as a good solvent by self-assembly methods. The effects of poor solvent vapor, polymer concentration, and the temperature of environment on the formation of the sphere patterns were investigated. It was found that the microsphere could be easily prepared in the ethanol non-solvent vapor atmosphere. Besides, increasing the environment temperatures was advantageous to fabricate microspheres. Furthermore, the property of non-solvent vapor was a key role to the formation of the sphere.

Abstract: The purpose of this study was to investigate the biocompatibility and degradation behavior of theophylline/chitosan microspheres, which has the potential application in pulmonary delivery system. Hemolysis test was carried out to estimate its blood toxicity. In vitro enzymatic hydrolysis was performed in 0.2 mg/ml lysozyme solution, while in vitro hydrolysis degradation was in 0.2 mol/L PBS solution (pH 7.4). The results of hemolysis test showed that the hemolysis rate was 4.771%, which showed that theophylline/chitosan microspheres had no hemolysis. The degradation rate of enzymatic hydrolysis and PBS hydrolysis was 62.66±2.1% and 37.79±1.2%, which indicates that degradation in lysozyme solution is faster than that in PBS solution. The morphology of microspheres with lysozyme and PBS solution developed into rough surfaces and became irregularly shaped. Accordingly, theophylline/chitosan microspheres possess preferable biocompability and degradation, which have promising potential for use as safe carrier in pulmonary drug delivery systems.

Abstract: Microspheres have been widely used for tissue engineering scaffolds. Microspheres have many advantages over the macrostructure such as high surface area for cell adhesion and proliferation and low mass transfer limits. In this study, we fabricated microspheres from gelatin and silk fibroin using water-in-oil (w/o) emulsion technique and glutaraldehyde crosslinking. Gelatin (G) and silk fibroin (SF) were blended at different G/SF weight blending ratios of 100/0, 90/10, 70/30, and 50/50. Physical and chemical properties of the microspheres including size and morphology were characterized. The Average size of microspheres obtained were at 858.42±41.93, 832.97± 9.44 , 785.24±17.66 and 735.83 ±13.19 μm, respectively. Morphology of G/SF microspheres was observed under a scanning electron microscope. Blending of silk fibroin increased the crosslinking degrees and water absorption. It also reduced degradation rate, comparing to the gelatin microspheres. The in vitro attachment and proliferation of rat bone marrow derived mesenchymal stem cells (MSC) cultured on G/SF microspheres were evaluated. G/SF 50/50 microspheres promoted the highest attachment of MSC on microspheres (46.0±5.8% of initial seeding at 6 hr). The G/SF 70/30 microspheres promoted the higher cell proliferation of MSC compared the others. Specific growth rate of the cells on the microspheres was at 9.85x10^-3 h^-1.

Abstract: A method was developed to prepare the Antheraea Pernyi silk fibroin (ASF) microspheres using lysozyme as a model drug to estimate the application of ASF in drug controlled release field. The structure of ASF microsphere carried drug was characterized by X-ray diffraction and FTIR. The morphology and the influence of the microspheres on the degradation of lysozyme were investigated using scanning electron microscope. The results show that encapsulation rate was increased and drug content was decreased with the addition of lysozyme increasing. In vitro release of lysozyme from the ASF particles we demonstrated that the release kinetics depends on the pH. The pH played important roles in controlling lysozyme release profiles. It also can be seen that the degradation speed of lysozyme ASF microspheres slightly larger than the pure ASF microspheres.

Abstract: In this study, chitosan (CS)/titanium dioxide (TiO₂) microspheres with different nanoTiO₂ content were obtained by suspension cross-linking technique and characterized by FT-IR and SEM. The strong peak of C=N stretching vibrations at 1641 cm^-1 were found which demonstrated that amino groups of CS reacted with aldehyde group of glutaraldehyde. SEM photographs showed that the CS/TiO₂ microspheres were spherical, and the size of the CS/TiO₂ microspheres ranging from 50 to 170 μm was analyzed with the software of Image J. The entrapment efficiency of the CS/TiO₂ microspheres was up to 67.7%. Compared with CS, CS/TiO₂ microspheres had better antibacterial activity against S. aureus and E. coli with a MIC value of 0.0125%.

Abstract: Chitosan (CS) microspheres loaded with levofloxacin (LOF) were prepared by emulsion crosslinking technique and the experimental parameters were optimized by orthogonal tests. The influences of various factors on the combination properties of chitosan microspheres were discussed. The optimal preparation condition was 98000 chitosan molecular weight, 30mg/ml chitosan concentration, 5:1 volume ratio of oil to water, 1:1 molar ratio of amino group of chitosan to aldehyde group of glutaraldehyde (GA), 1500 rpm stirring rate, 2:1 mass ratio of chitosan to levofloxacin and 1 h crosslinking time. The CS microspheres prepared under optimal parameters had spherical morphology with 1.59 μm of average geometric diameter and 0.99 of span, its loading capacity (LC) and association efficiency (AE) values were 21.71% and 80.49% respectively. In vitro release profile showed the levofloxacin released fast initially, and then slowly from the microspheres with T₉₀ occurring at 188.5h and its delivery behavior conformed to First-Order release kinetics model.

Abstract: Functional floating bead (F-FB), prepared by anchoring the organic sulfonic acid on the surface of the blackberry-like structural FB, was used as both the inorganic substrate and the in situ dopant for the in situ chemical oxidative polymerization of pyrrole to obtain the polypyrrole/functional floating bead (PPy/F-FB) composites. The encapsulating morphologies were revealed with the scanning electron microscopy technique. The PPy/F-FB composites were characterized with Fourier transform infrared spectroscopy and thermogravimetric analysis. Based on the cyclic voltammetry of the composites, it was found that the composites performed typical electrochemical supercapacitor behavior.