Sustained-release butorphanol microparticles

Various butorphanol-loaded microparticles have been prepared with a biodegradable copolymer P(FAD-SA) of erucic acid dimer (FAD) and sebacic acid (SA) and a copolymer P(CPP-SA) of carboxyphenoxypropane (CPP) and SA using a melt compounding and milling method. Drug release was measured in vitro following incubation of drug-loaded microparticles in water for injection at 37°C. It was found that butorphanol was released in a sustained manner, yielding a cumulative drug release of about 100% over a period of 48 hr. Also, drug release was affected by drug loading and the size of the microparticles; however, it was not significantly influenced by the copolymer composition. Scanning electron microscopic (SEM) results showed that most of the particles were irregular in shape with uneven surfaces. The molecular weights of the copolymers were not changed after this fabrication process. In addition, 20% butorphanol-encapsulated microspheres were prepared with copolymer P(FAD-SA) by spray-drying. The SEM micrograph shows that the particle sizes of the microspheres ranged from 2 to 10 μm, and the external surfaces appear smooth. Moreover, rapid drug release was observed for these microspheres, with more than 92% of the encapsulated drug released within the first 2 hr.     

Fluidization of microparticles in electric field

The results of statistical modeling of the electrodynamic fluidization of microparticles in an electric field are outlined. The dependence of the current density and charge distribution function of the microparticles on the microparticle concentration is discussed. The limiting attainable microparticle concentration in the interelectrode space is considered. The dependence of the concentration of fluidized microparticles on their bulk concentration is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 64–72, January, 1991.     

Self-organized patterns of microparticles in polymer films

A simple method to create self-organized patterns of microparticles in polymer films is demonstrated. Dye-loaded zeolite crystals are used as model microparticles, allowing convenient imaging of the patterns by fluorescence microscopy. The pattern formation can be interpreted within the general framework of the model of local self-activation and lateral inhibition. Two starting parameters, namely the polymer concentration and the wet film thickness, control the size and shape of the particle aggregates in the patterns, as well as their spacing. The size of the aggregates ranges from 50 to 340 μm.     

Charging of metal microparticles in electron flow

We have studied the charging of copper microparticles in electron flow. It is established that the parameters of secondary electron emission from microparticles can significantly differ from those for metal films and volume targets. Conditions are determined under which negative charging of micron-sized copper particles in electron flow takes place. In the case of spherical microparticles, secondary emission is significantly increased as a result of the oblique incidence of primary electrons. A general approach is proposed that can be used to estimate the electron energy necessary for charging microparticles to high negative potentials.

     

聚苯乙烯微球化学制备及镀镍工艺研究

在聚苯乙烯微球表面进行化学镀镍可以制备磁性微球.采用此方法,能将聚苯乙烯的轻质的优点和镍的磁性结合起来.同时,此方法还具有如下优点:操作简单、反应条件易于控制.采用扫描电镜(SEM)表征了微球的表面形貌.考察了施镀温度、镀液浓度、镀液pH值对结果的影响.     

Designing drug-loaded multi-layered polymeric microparticles

This work reports how novel multi-layered (from double-layered to quadruple-layered) microparticles comprising immiscible polymers can be fabricated through a simple, economical, reliable and versatile one-step solvent evaporation method. These multi-layered microparticles would be excellent candidates to overcome problems inherent in single-layered microparticles for drug delivery. Particle morphologies, layer configurations, and drug distribution were determined by scanning electron microscopy and Raman mapping. Key process parameters achieving the formation of the multi-layered structure were identified. Encapsulation of multiple drugs and layer localization of these drugs within these multi-layered microparticles have also shown to be possible, which were driven by drug-polymer affinity. This one-step fabrication technique can therefore be used for tailoring particle designs, thus facilitating the development of multiparticulate drug delivery devices.     

Ordered structures of microparticles in a glow discharge

The possibilities are analyzed and experimentally investigated of the formation and destruction of structures of charged microparticles in a glow discharge plasma in different gases. The use of a conical discharge tube and the introduction of an orifice plate into that tube enable one to stabilize the strata and obtain dust formations of different types. Given a fairly high concentration of dust particles in a structure, this structure itself affects the local properties of the plasma.     

Oxidative fabrication of spherical polycarbazole-based microparticles

A straightforward oxidative liquid phase polymerization (LPP) method has been successfully developed for the fabrication of spherical functional (polyCOOH) polycarbazole-based microparticles from corresponding carbazole-containing monomers. The influence of the chemical structure of starting carbazole monomers on the LPP-based microparticle formation has been deeply examined using scanning electron microscopy (SEM).     

Liposomes self-assembled from electrosprayed composite microparticles

Composite microparticles, consisting of polyvinylpyrrolidone (PVP), naproxen (NAP) and lecithin (PC), have been successfully prepared using an electrospraying process and exploited as templates to manipulate molecular self-assembly for the synthesis of liposomes in?situ. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) observations demonstrate that the microparticles have an average diameter of 960?±?140?nm and a homogeneous structure. X-ray diffraction (XRD) patterns, differential scanning calorimetry (DSC) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) results verify that the building blocks NAP and PC are scattered in the polymer matrix in a molecular way owing to the very fast drying of the electrospraying process and the favorable secondary interactions among the components. FESEM, scanning probe microscope (SPM) and TEM observations demonstrate that the liposomes can be achieved through molecular self-assembly in?situ when the microparticles contact water thanks to 'like prefers like' and by means of the confinement effect of the microparticles. The liposomes have an encapsulation rate of 91.3%, and 80.7% of the drug in the liposomes can be freed into the dissolution medium in a sustained way and by a diffusion mechanism over a period of 24?h. The developed strategy not only provides a new, facile, and effective method to assemble and organize molecules of multiple components into liposomes with electrosprayed microparticles as templates, but also opens a new avenue for nanofabrication in a step-by-step and controllable way.     

Continuous sorting of microparticles using dielectrophoresis

Sorting of particles such as cells is a critical process for many biomedical applications, and it is challenging to integrate it into an analytical microdevice. We report an effective and flexible dielectrophoresis (DEP)-based microfluidic device for continuous sorting of multiple particles in a microchannel. The particle sorter is composed of two components-a DEP focusing unit and a Movable DEP Trap (MDT). The trap is formed by an array of microelectrodes at the bottom of the channel and a transparent electrode plate placed at the top. The location of the trap is dependent on the configuration of voltages on the array and therefore is addressable. Flowing particles are first directed and focused into a single particle stream by the focusing unit. The streamed particles are then sorted into different fractions using the movable trap by rapidly switching the applied voltage. The performance of the sorter is demonstrated by successfully sorting microparticles in a continuous flow. The proposed DEP-based microfluidic sorter can be implemented in applications such as sample preparation and cell sorting for subsequent analytical processing, where sorting of particles is needed.     

Preparation and evaluation of posaconazole-loaded enteric microparticles in rats

Objectives: Posaconazole (POS) is an antifungal compound which has a low oral bioavailability. The aim of this study was to prepare POS enteric microparticles to enhance its oral bioavailability.

Methods: POS enteric microparticles were prepared with hypromellose acetate succinate (HPMCAS) via the spray drying method. The solvent mixtures of acetone and ethanol used in the preparation of the microparticles were optimized to produce the ideal POS enteric microparticles. Multivariate data analysis using a principal component analysis (PCA) was used to find the relationship among the HPMCAS molecular characteristics, particle properties and drug release kinetics from the spray dried microparticles.

Key findings: The optimal spray solvent mixtures were critical to produce the POS microparticles with the defined polymer entanglement index, drug surface enrichment, particle size and drug loading. The HPMCAS molecular characteristics affected the microscopic connectivity and diffusivity of polymer matrix and eventually influenced the drug release behavior, and enhanced the bioavailability of POS.

Conclusions: These studies suggested that the selection of suitable solvent mixtures of acetone and ethanol used in the spray drying of the microparticles was quite important to produce the entangled polymer structures with preferred polymer molecular properties of polymer coiling, overlap concentration and entanglement index. Additional studies on particle size and surface drug enrichment eventually produced HPMCAS-based enteric microparticles to enhance the oral bioavailability of POS.     

Preparation and in vitro characteristics of lactoferrin-loaded chitosan microparticles

In order to achieve the delivery and controlled release of lactoferrin (LF), a biologically multifunctional protein, chitosan microparticles loaded with LF were prepared. Several types of chitosan microparticles containing LF were prepared by the w/o emulsification-solvent evaporation method, and the particle characteristics and release properties in JP 2nd fluid, pH 6.8, were examined. All kinds of microparticles were obtained at a yield of more than 75% (w/w). LF-loaded microparticles prepared by nonsonication and nonaddition of sulfate, named Ch-LF(N), showed high drug content, small particle size and spherical particle shape. Also, for release properties, Ch-LF(N) exhibited gradual drug release over 7 hr with less remaining in the microparticles. Considering the mucoadhesive properties of chitosan microparticles, Ch-LF(N) are suggested to be useful for gradual supply to topical diseased sites or for effective delivery to intestinal areas with abundant LF receptors.     

Optical near-field scanning by microparticles suspended in immersion fluid

A new method of obtaining images with a resolution exceeding the diffraction limit of an optical microscope is proposed and experimentally implemented. The method is based on monitoring the pattern of free motion of microparticles over the sample surface and an analysis of the intensity of light scattered by these particles. In experiment, a threefold increase in the ultimate resolution of a microscope has been achieved.     

One-pot synthesis of hierarchical fluorapatite hollow microparticles

Hierarchical fluorapatite (FHAp) microparticles with hollow interiors were prepared by a one-pot hydrothermal method using Na₂EDTA/citric acid (CA) as additive. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results showed that the resultant hollow FHAp microparticles with uniform shape and size are hierarchically constructed by many small FHAp crystallites building units. Time-dependent experimental results indicated that Ostwald ripening process could be used to explain the formation mechanism for the hollow FHAp microparticles.     

SAS过程制备乙基纤维素超细微粒实验研究

以自制的超临界反溶剂过程实验装置制备了乙基纤维素超细微粒。实验以乙醇为有机溶剂,超临界CO2为反溶剂,研究了操作温度、压力、反溶剂流量及溶液浓度等操作参数对制备的超细微粒的形态、粒径及粒径分布的影响。实验发现,通过控制实验参数,可使制备的乙基纤维素微粒基本呈球形,最小粒径可降至1μm以下,粒径分布较均匀。     

Preparation and characterization of collagen-modified polylactide microparticles

To improve cytocompatibility of polylactide (PLA) and to obtain an injectable scaffold for tissue engineering, collagen-modified PLA (CPLA) microparticles were prepared. Poly-(α-methacrylic acid)-grafted PLA (PMAA-PLA) was obtained by photooxidization and UV induced polymerization. Suspension of PMAA-PLA microspheres with an average size of 172.8 ± 3.6 nm was prepared with solvent evaporation technique. CPLA microparticles were prepared by adding collagen acetic acid solution into PMAA-PLA microsphere suspension prepared above. FTIR spectrum of PMAA-PLA confirmed that PMAA had been grafted on PLA surface. Analytical results of FTIR, XPS, SEM, hematoxylin and eosin (HE) stained and zeta potential measurement showed that the CPLA microparticles obtained by modifying PMAA-PLA microspheres with collagen molecules uniformly have a microporous structure and a particle size of less than 100 μm. The CPLA microparticles were expected to be used as an injectable scaffold for tissue regeneration.     

花状微米颗粒的制备及其电流变性能研究

采用溶剂热法制备出花状微米颗粒。采用SEM,TEM,XRD,FT-IR等方法分析颗粒形貌及成分。结果表明,花状颗粒为丙三醇基化合物,其表观直径在2~3μm之间,表面由次级的刺状结构组成。分别以花状微米颗粒和光滑球状Ti O2颗粒为分散相制备电流变液,并测试其电流变性能和沉降稳定性。实验结果表明,在相同电场强度下,花状颗粒电流变液的剪切屈服强度明显高于光滑球状颗粒电流变液,但漏电流密度远小于光滑球状颗粒电流变液;静置12 d,花状颗粒电流变液的抗沉降率较之光滑球状颗粒电流变液有显著提高。花状颗粒特有的形貌是其具有优异电流变性能和沉降稳定性的主要原因。     

Multiplexed protein quantification with barcoded hydrogel microparticles

We demonstrate the use of graphically encoded hydrogel microparticles for the sensitive and high-throughput multiplexed detection of clinically relevant protein panels in complex media. Combining established antibody capture techniques with advances in both microfluidic synthesis and analysis, we detected 1-8 pg/mL amounts of three cytokines (interleuken-2, interleuken-4, and tumor necrosis factor alpha) in single and multiplexed assays without the need for filtration or blocking agents. A range of hydrogel porosities was investigated to ensure rapid diffusion of targets and reagents into the particle as well as to maintain the structural integrity of particles during rinsing procedures and high-velocity microfluidic scanning. Covalent incorporation of capture antibodies using a heterobifunctional poly(ethylene glycol) linker enabled one-step synthesis and functionalization of particles using only small amounts of valuable reagents. In addition to the use of three separate types of single-probe particles, the flexibility of the stop-flow lithography (SFL) method was leveraged to spatially segregate the three probes for the aforementioned target set on an individual encoded particle, thereby demonstrating the feasibility of single-particle diagnostic panels. This study establishes the gel-particle platform as a versatile tool for the efficient quantification of protein targets and significantly advances efforts to extend the advantages of both hydrogel substrates and particle-based arrays to the field of clinical proteomics.