Fabrication of porous bioactive glass particles by one step sintering

In this study, we reported a facile method to prepare porous bioactive glass microparticles. Porous particles were synthesized by sintering hollow bioactive glass microspheres obtained using a sol-gel co-template technology. The results showed that porous bioactive glass particles possessed a narrow particle size distribution, a relatively porous surface morphology and a hollow structure. It is worth to say that the resulting microparticles present an amorphous structure although the sintering temperature was improved compared to hollow microspheres. The presence of macropore on the shell may provide an efficient method to carry drugs in the hollow cores. Considering the high deposit rate of nanoscale apatite for bioactive glass materials, the porous microparticles should have potential applications in drug and bioactive molecules delivery, in addition to bone tissue regeneration.     

Influence of the preparation procedure and chitosan type on physicochemical properties and release behavior of alginate–chitosan microparticles

Background: The potential for use of chitosan-treated alginate microparticles as a vehicle for oral phenytoin delivery has not been thoroughly exploited. Aim: We studied the influence of preparation procedure and chitosan type on physicochemical properties and release behavior of alginate-chitosan microparticles. Method: The total number of 24 microparticles formulations prepared by varying contents of calcium gelling ions and varying contents and type of chitosan was examined. As an additional variable, two different hardening times (1 and 24 hours) were employed. Possible interactions of components, surface morphology of microparticles as well as release profile of phenytoin were studied. Results: Both series of formulations with regard to hardening times, irrespective of the chitosan type and/or concentration employed appeared to be highly loaded with the model drug (above 90%). The drug release studies showed that the kinetics of phenytoin cannot be straightforwardly predicted based on the molecular weight of chitosan alone. On the other hand, prolonging the hardening time from 1 to 24 hours had significantly improved phenytoin kinetics, and gave rise to a formulation with the liberation half-time of about 2.5 hours. Conclusion: This study showed that the latter formulation is eligible for further modifications aimed at improving the regularity of phenytoin absorption.     

Microencapsulation of cytarabine using poly(ethylene glycol)–poly(ε-caprolactone) diblock copolymers as surfactant agents

Background: The high water solubility and the low molecular weight of cytarabine (Ara-C) are major obstacles against its particulate formulation as a result of its low affinity to the commonly used hydrophobic polymers. Methods: Biodegradable cytarabine loaded-microparticles (Ara-C MPs) were elaborated using poly(?-caprolactone) (PCL) and monomethoxy polyethylene glycol (mPEG)–PCL diblock copolymer in order to increase the hydrophilicity of the polymeric matrix. For this purpose, a series of mPEG–PCL diblock copolymers with different PCL block lengths were synthesized. Compositions and molecular weights of obtained copolymers were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, size exclusion chromatography, and size exclusion chromatography–multi-angle laser light scattering. Ara-C MPs were prepared by double emulsion-solvent evaporation method. The effects of varying PCL block lengths on microparticle encapsulation efficiency, size, and zeta potential were evaluated. Results: Increasing the PCL block lengths of copolymers substantially increased the Ara-C encapsulation efficiency and the microparticle size but it decreased their zeta potential. Microparticles were spherical in shape, with a smooth surface and composed of homogenously distributed Ara-C-containing aqueous domains in the polymer matrix. The in vitro drug release kinetics of the optimized microparticles showed a hyperbolic profile with an initial burst release. Conclusion: These results showed the important role of the amphiphilic diblock copolymers as stabilizing agent in the encapsulation of Ara-C in PCL microparticles, suggesting their potential use for the microparticulate formulations of other small hydrophilic bioactive molecules.     

Preparation and Physical Characterization of Alginate Microparticles Using Air Atomization Method

Alginate microparticles were prepared using an air atomization method and varying formulation and processing conditions. Thereafter, the size and surface morphology of alginate microparticles were characterized. The trapping efficiencies of the ketoconazole, acetaminophen, vitamin C, and Bifidobacteria bifidum as model core materials were then determined. The air atomization process produced free-flowing and small-size microparticles after the freeze-drying process. The size distribution and surface morphology varied depending on the concentration of wall-forming materials and processing conditions. Generally, the geometric mean size increased as the concentration of alginate and poly-l-lysine and the delivery rate increased, but the air pressure decreased. Most of all, the ratio of delivery rate of alginate solution and air pressure could affect the size and surface morphology of alginate microparticles. However, the geometric mean size of alginate poly-l-lysine microparticles reproducibly ranged from about 80 to 130 μm. The microparticles were irregularly spherical or elliptical. The trapping efficiencies of ketoconazole, acetaminophen, vitamin C, and bifidobacteria were determined to be 71.5%, 60.1%, 1.6%, and 31%, respectively, when alginate concentration (1.5%), poly-l-lysine concentration (0.02%), air pressure (0.75 bar), delivery rate (8 ml/min), and spraying distance (45 cm) were applied. The current microencapsulation process using the air atomization method provides an alternative to entrapping small molecules and macromolecules without using harmful organic solvents. In addition, the small-size and free-flowing alginate microparticles containing active substances can be used as an intermediate in pharmaceutical applications.     

The effects of particle size on the physicochemical properties of optimized astaxanthin-rich Xanthophyllomyces dendrorhous-loaded microparticles

To improve the entrapment efficiency (EE) of astaxanthin-rich Xanthophyllomyces dendrorhous (ASX)-loaded calcium alginate gel (ASX-CAG) microparticles, we used a response surface methodology to optimize preparation conditions including the ratio of ASX to total material (X₁), alginate concentration (X₂), and CaCl₂ concentration (X₃). The EE and the mean size of the ASX-CAG microparticles were 76.7 g/100 g and 210.26 μm, respectively, after preparation under optimal conditions: 24 g ASX/100 g total material, 1.0 g/100 g alginate, and 200 mmol/L CaCl₂. The effects of particle size on different characteristics were evaluated with increasing microparticle size; an increase in microparticle size significantly increased EE and the antioxidant activity of ASX, but resulted in a decrease in the release of entrapped ASX. Most importantly, the lipid peroxidation inhibitory activity of encapsulated ASX (55.1%) was significantly higher and longer-lasting than that of non-encapsulated ASX (40.5%) after 36 h of storage as determined using the thiobarbituric acid method.     

Fabrication of advanced particles and particle-based materials assisted by droplet-based microfluidics

Recent advances in the fabrication of complex particles and particle-based materials assisted by droplet-based microfluidics are reviewed. Monodisperse particles with expected internal structures, morphologies, and sizes in the range of nanometers to hundreds of micrometers have received a good deal of attention in recent years. Due to the capability of generating monodisperse emulsions and of executing precise control and operations on the suspended droplets inside the microchannels, droplet-based microfluidic devices have become powerful tools for fabricating complex particles with desired properties. Emulsions and multiple-emulsions generated in the microfluidic devices can be composed of a variety of materials including aqueous solutions, gels, polymers and solutions containing functional nanoparticles. They are ideal microreactors or fine templates for synthesizing advanced particles, such as polymer particles, microcapsules, nanocrystals, and photonic crystal clusters or beads by further chemical or physical operations. These particles are promising materials that may be applicable for many fields, such as photonic materials, drug delivery systems, and bio-analysis. From simple to complex, from spherical to nonspherical, from polymerization and reaction crystallization to self-assembly, this review aims to help readers be aware of the many aspects of this field.     

阳离子型有机微粒的助留助滤应用研究

探讨了自制的阳离子有机微粒(CPMP)对漂白阔叶木浆、漂白麦草浆和脱墨废纸浆助留助滤作用的影响.结果表明:各种纸料的一次留着率上升随着CPMP用量的增加而上升,随着转速的增加而减少;CPMP对剪切力和pH值大小不太敏感;CPMP对阔叶木浆的助留助滤效果最好,麦草浆次之,对脱墨废纸浆效果最差.     

Fabrication of size‐controllable mPEG‐decorated microparticles conjugating optically active ketoprofen based on self‐assembly of amphiphilic random copolymers

Novel size‐controllable mPEG‐decorated polymeric microparticles binding optically active ketoprofen were successfully fabricated based on chemoenzymatic synthesis and self‐assembly of amphiphilic random polymer–ketoprofen conjugates with mPEG and (S)‐ketoprofen as pendants. A series of mPEG₃₅₀‐ or mPEG₁₀₀₀‐functionalized amphiphilic random polymer–ketoprofen conjugates with drug loading capacity from 16.5% to 73.2% were easily prepared by combining enzymatic resolution with radical polymerization and characterized by Fourier Transform Infrared spectroscopy, ¹H‐NMR, and gel permeation chromatography. The formation of aggregates from the amphiphilic random polymer–ketoprofen conjugates was investigated by ultraviolet‐visible absorption spectra using pyrene as the guest molecule. Transmission electron microscopy measurement revealed that the self‐assemblies were well dispersed as spherical microparticles. The size of the self‐assemblies could be widely tuned by varying the length of mPEG chains and the content of ketoprofen in the synthetic polymer–ketoprofen conjugates, and a series of mPEG‐decorated (S)‐ketoprofen‐bound polymeric microparticles with average radius from 70 nm to 1.1 μm were obtained. The successful preparation of the microparticles containing (S)‐ketoprofen provided a new strategy for the design and fabrication of optically active drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrodeposition of platinum microparticle interface on conducting polymer film modified nichrome for electrocatalytic oxidation of methanol

A simple and “green” approach for fabrication of platinum microparticle interface on conducting polymer film modified nichrome matrix (Pt/PAn/Nc) for methanol oxidation was investigated. The Pt microparticles were grown directly on the polyaniline precursor film modified nichrome matrix (PAn/Nc) in dilute chloroplatinic acid solution by cyclic voltammetry. The SEM revealed that the deposits were composed of spherical Pt microparticles. Cyclic voltammetry and chronoamperometry were used for characterization of the electrode properties. Results showed that the spherical Pt/PAn/Nc electrode enhanced the catalytic activity and promoted methanol electrooxidation. The catalytic activity of Pt/PAn/Nc electrode was 15 times higher than that obtained from pure platinum under the same conditions. Moreover, the deposited Pt microparticles improved the electrochemical properties of nichrome and reduced the dosage of noble metal platinum, remarkably. The cost could be reduced dramatically by decreasing the contents of platinum. The Pt/PAn/Nc are likely a promising electrocatalyst for methanol electrooxidation.